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Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 2016 Sep 6;113(38):10672–10677. doi: 10.1073/pnas.1606946113

Whole-exome sequencing identifies recurrent AKT1 mutations in sclerosing hemangioma of lung

Seung-Hyun Jung a,b, Min Sung Kim c, Sung-Hak Lee d, Hyun-Chun Park a,b, Hyun Joo Choi d, Leeso Maeng d, Ki Ouk Min d, Jeana Kim d, Tae In Park e, Ok Ran Shin d, Tae-Jung Kim d, Haidong Xu f, Kyo Young Lee d, Tae-Min Kim g, Sang Yong Song h, Charles Lee i,j, Yeun-Jun Chung a,b,1, Sug Hyung Lee c,1
PMCID: PMC5035874  PMID: 27601661

Significance

This report is an in-depth genetic profiling of pulmonary sclerosing hemangioma (PSH). We have discovered that PSH harbor recurrent AKT1 mutations (45.6%), most of which were AKT1 p.E17K mutations. This mutation may be the single-most common driver alteration to develop PSHs. In contrast to lung adenocarcinoma, PSH genomes harbor only a single driver mutation (AKT1 or β-catenin), which may provide clues to understanding the benign biology of PSH and for differential genomic diagnosis of lung tumors.

Keywords: pulmonary sclerosing hemangioma, whole-exome sequencing, AKT1 mutation, copy number alteration

Abstract

Pulmonary sclerosing hemangioma (PSH) is a benign tumor with two cell populations (epithelial and stromal cells), for which genomic profiles remain unknown. We conducted exome sequencing of 44 PSHs and identified recurrent somatic mutations of AKT1 (43.2%) and β-catenin (4.5%). We used a second subset of 24 PSHs to confirm the high frequency of AKT1 mutations (overall 31/68, 45.6%; p.E17K, 33.8%) and recurrent β-catenin mutations (overall 3 of 68, 4.4%). Of the PSHs without AKT1 mutations, two exhibited AKT1 copy gain. AKT1 mutations existed in both epithelial and stromal cells. In two separate PSHs from one patient, we observed two different AKT1 mutations, indicating they were not disseminated but independent arising tumors. Because the AKT1 mutations were not found to co-occur with β-catenin mutations (or any other known driver alterations) in any of the PSHs studied, we speculate that this may be the single-most common driver alteration to develop PSHs. Our study revealed genomic differences between PSHs and lung adenocarcinomas, including a high rate of AKT1 mutation in PSHs. These genomic features of PSH identified in the present study provide clues to understanding the biology of PSH and for differential genomic diagnosis of lung tumors.


Pulmonary sclerosing hemangioma (PSH) is a benign tumor that usually presents as a solitary, well-defined mass in the lung (1). PSH predominantly affects females (1:5) with a higher incidence in the Far East (2). As the name indicates, PSH is often hemorrhagic and sclerotic. Histologically, the tumor cells in PSH consist of two cell types (cuboidal epithelial and polygonal stromal cells) (3). Immunohistochemical and ultrastructural studies have identified that both cells are derived from undifferentiated respiratory epithelium that is the histologic origin of lung adenocarcinoma as well. Previous studies have shown that PSH and adenocarcinoma in the lung share some immunohistochemical and genetic features. For example, expression of TTF-1, which plays a crucial role in normal lung function and morphogenesis, is common to PSH and lung adenocarcinoma (3). In addition, allelic imbalance and CpG island methylation in some loci have been reported in these two tumors (4, 5). However, whereas many driver genes for lung adenocarcinomas have been identified, for somatic mutations, there have not been any candidate driver mutations identified in PSHs, except for low-frequency mutations in β-catenin and TP53 (6, 7). Frequent somatic mutations identified in lung adenocarcinomas, such as KRAS and EGFR, have not been detected in PSH, suggesting that genomic alterations of these two lung tumors might be different from each other. Furthermore, there is no evidence of PSH progression to lung cancers. These earlier data indicate that despite the common cellular origin of PSH and lung adenocarcinoma, genetic mechanisms for their development may be different.

Somatic genetic alteration is a driving force for the development of tumor. Even a benign tumor contains somatic mutations, albeit less common than in a malignant tumor. For example, uterine leiomyoma and breast fibroadenoma, common benign tumors, harbor recurrent mutations in MED12 (8, 9). Based on the established concept that PSH is a true tumor, we hypothesize that it may harbor somatic mutations. For a comprehensive elucidation of genetic alterations in cancers, genomes of many tumors have been studied by using whole-exome (WES) or whole-genome sequencing analysis (1012). However, to date, such high-throughput sequencing data on PSH is lacking. In this study we analyzed genomes of the PSH by WES.

Results

Whole-Exome Sequencing.

We conducted a comprehensive examination of genetic alterations (somatic mutations and copy number alterations, CNAs) in 44 cases of PSH: 8 fresh-frozen and 36 formalin-fixed paraffin-embedded (FFPE), from 43 patients (two separate PSHs were from one patient), with matched normal tissues using WES. Most of the patients were female (91%) and the median age was 52 y (range 12–74 y) (Table S1). Coverages of the sequencing depth were mean of 156× for PSHs and 152× for matched normal, with an average of 95% of bases covered by at least 20 reads in each sample, respectively (Table S2).

Table S1.

Patient characteristics of the discovery and validation sets

Sample ID Sets Gender Age at diagnosis (y) Tumor size (diameter, cm) Sample source
SH01 Discovery Female 56 2.5 Frozen
SH02 Discovery Male 42 1.5 Frozen
SH03 Discovery Female 30 1.7 FFPE
SH04 Discovery Female 55 1.5 FFPE
SH05 Discovery Female 34 3.0 Frozen
SH06T1 Discovery Female 46 0.6 FFPE
SH06T2 Discovery Female 46 1.4 FFPE
SH07 Discovery Female 62 1.5 Frozen
SH08 Discovery Female 48 1.8 Frozen
SH09 Discovery Female 55 1.5 FFPE
SH10 Discovery Female 74 3.5 FFPE
SH11 Discovery Female 50 2.2 FFPE
SH18 Discovery Female 29 1.5 FFPE
SH20 Discovery Female 61 2.2 FFPE
SH23 Discovery Female 28 2.4 FFPE
SH25 Discovery Female 73 1.3 FFPE
SH34 Discovery Female 64 1.5 FFPE
SH36 Discovery Female 43 1 × 1 FFPE
SH37 Discovery Male 27 6 FFPE
SH40 Discovery Female 54 4.5 FFPE
SH41 Discovery Female 70 2 FFPE
SH42 Discovery Female 54 2 FFPE
SH43 Discovery Female 49 3.5 FFPE
SH46 Discovery Female 42 2.0 FFPE
SH47 Discovery Female 52 2.5 FFPE
SH48 Discovery Female 68 3.5 FFPE
SH49 Discovery Female 51 2.8 FFPE
SH50 Discovery Male 12 2.8 FFPE
SH51 Discovery Female 22 4.5 FFPE
SH52 Discovery Female 67 2.0 FFPE
SH53 Discovery Male 48 2.3 FFPE
SH54 Discovery Female 49 2.2 FFPE
SH55 Discovery Female 61 3.5 FFPE
SH56 Discovery Female 36 1.8 FFPE
SH57 Discovery Female 64 2.1 FFPE
SH58 Discovery Female 49 2.0 FFPE
SH59 Discovery Female 63 2.3 FFPE
SH60 Discovery Female 63 1.0 FFPE
SH61 Discovery Female 17 1.5 FFPE
SH62 Discovery Female 58 1.0 FFPE
SH63 Discovery Female 53 3.5 FFPE
SH64 Discovery Female 61 4.5 Frozen
SH66 Discovery Female 40 1.8 Frozen
SH67 Discovery Female 52 2.0 Frozen
SH12 Validation Female 30 1.2 FFPE
SH13 Validation Female 60 2.0 FFPE
SH14 Validation Female 51 1.7 FFPE
SH15 Validation Female 55 1.5 FFPE
SH16 Validation Male 65 0.5 FFPE
SH17 Validation Male 30 2.0 FFPE
SH19 Validation Female 66 1.5 FFPE
SH21 Validation Female 53 1.7 FFPE
SH22 Validation Female 55 3.0 FFPE
SH24 Validation Female 48 3.0 FFPE
SH26 Validation Female 54 1.2 FFPE
SH27 Validation Female 48 2.0 FFPE
SH28 Validation Female 55 2.0 FFPE
SH29 Validation Female 61 1.9 FFPE
SH30 Validation Female 49 5.0 FFPE
SH31 Validation Female 28 5.0 FFPE
SH32 Validation Female 32 3.5 FFPE
SH33 Validation Female 57 2.0 FFPE
SH35 Validation Female 42 2.5 FFPE
SH38 Validation Male 17 2.5 FFPE
SH39 Validation Male 38 2.5 FFPE
SH44 Validation Male 58 2.5 FFPE
SH45 Validation Female 55 2.5 FFPE
SH65 Validation Female 55 3.0 Frozen

Table S2.

The description of whole-exome sequencing data

Sample ID* Sequencing reads Mapped reads (%) Mapped reads in exon (%) Coverage (mean) Percent of bases (≥ 20 reads)
SH01N 118,197,262 108,879,483 (92.1) 85,500,955 (72.3) 144.1 91.5
SH01T 132,337,323 130,797,497 (98.8) 98,995,812 (74.8) 160.6 91.3
SH02N 140,640,591 138,969,521 (98.8) 105,375,731 (74.9) 170.9 92.0
SH02T 137,049,720 135,327,809 (98.7) 102,447,257 (74.8) 166.2 91.9
SH03N 114,313,694 106,844,646 (93.5) 83,339,445 (72.9) 140.6 92.1
SH03T 110,777,788 102,084,391 (92.2) 79,862,041 (72.1) 135.8 94.4
SH04N 150,751,493 118,523,596 (78.6) 89,610,363 (59.4) 149.4 90.9
SH04T 136,372,096 118,007,518 (86.5) 90,664,838 (66.5) 152.0 94.0
SH05N 124,952,345 122,723,818 (98.2) 95,145,874 (76.2) 155.2 91.2
SH05T 119,526,275 117,738,851 (98.5) 91,443,701 (76.5) 149.1 91.1
SH06N 157,568,019 117,318,182 (74.5) 89,172,393 (56.6) 149.4 91.1
SH06T1 126,569,663 109,392,999 (86.4) 85,479,819 (67.5) 144.9 93.2
SH06T2 175,568,457 151,033,814 (86.0) 118,488,533 (67.5) 209.1 98.5
SH07N 128,818,752 126,787,029 (98.4) 98,534,473 (76.5) 160.5 91.2
SH07T 136,319,429 134,117,448 (98.4) 103,376,647 (75.8) 168.7 92.0
SH08N 119,529,810 117,625,696 (98.4) 92,132,837 (77.1) 150.3 90.5
SH08T 125,915,096 124,153,408 (98.6) 96,643,803 (76.8) 157.7 91.2
SH09N 131,003,302 107,128,096 (81.8) 79,116,007 (60.4) 131.9 90.3
SH09T 117,101,034 107,342,807 (91.7) 84,463,728 (72.1) 141.8 93.8
SH10N 175,228,607 108,181,567 (61.7) 83,647,239 (47.7) 141.9 91.2
SH10T 152,523,855 105,434,450 (69.1) 81,423,260 (53.4) 137.9 93.5
SH11N 122,820,217 100,337,622 (81.7) 78,532,100 (63.9) 134.0 92.4
SH11T 112,382,717 89,922,844 (80.0) 69,735,021 (62.1) 119.3 94.2
SH18N 116,732,588 101,458,107 (86.9) 78,567,017 (67.3) 131.0 89.1
SH18T 124,536,062 105,694,862 (84.9) 81,013,572 (65.1) 136.7 90.6
SH20N 132,753,120 106,365,793 (80.1) 76,391,752 (57.5) 127.0 89.2
SH20T 135,387,229 106,936,962 (79.0) 80,198,879 (59.2) 135.0 90.2
SH23N 130,043,054 106,614,510 (82.0) 79,473,894 (61.1) 131.4 90.0
SH23T 135,166,104 103,163,691 (76.3) 76,516,158 (56.6) 125.7 88.5
SH25N 127,078,498 102,184,670 (80.4) 78,437,273 (61.7) 131.5 89.9
SH25T 124,186,239 110,542,064 (89.0) 88,827,247 (71.5) 149.5 90.0
SH34N 124,973,391 108,950,892 (87.2) 83,095,723 (66.5) 137.3 90.4
SH34T 103,537,061 93,226,848 (90.0) 70,780,434 (68.4) 117.8 91.4
SH36N 163,872,197 89,147,617 (54.4) 65,042,895 (39.7) 114.6 97.0
SH36T 140,366,854 81,719,297 (58.2) 59,154,273 (42.1) 104.1 97.2
SH37N 142,985,090 105,154,566 (73.5) 77,234,318 (54.0) 134.3 97.5
SH37T 133,475,817 73,305,138 (54.9) 52,805,549 (39.6) 92.3 94.9
SH40N 160,504,261 145,416,934 (90.6) 111,372,236 (69.4) 194.1 98.6
SH40T 140,261,603 98,583,945 (70.3) 78,287,285 (55.8) 138.4 96.9
SH41N 145,064,883 124,950,335 (86.1) 84,615,275 (58.3) 144.3 98.3
SH41T 188,747,902 172,127,790 (91.2) 120,456,820 (63.8) 207.8 98.9
SH42N 137,224,204 120,501,439 (87.8) 92,099,191 (67.1) 160.1 97.7
SH42T 138,967,416 121,023,015 (87.1) 89,481,085 (64.4) 155.2 97.4
SH43N 137,223,277 123,882,313 (90.3) 91,977,036 (67.0) 158.5 98.0
SH43T 136,061,555 116,221,260 (85.4) 81,271,036 (59.7\) 139.0 97.4
SH46N 145,984,632 113,670,486 (77.9) 85,169,792 (58.3) 148.7 97.7
SH46T 136,066,310 97,784,225 (71.9) 74,352,808 (54.6) 131.0 96.8
SH47N 112,702,783 45,464,195 (40.3) 31,150,064 (27.6) 54.4 93.6
SH47T 140,632,773 90,996,850 (64.7) 68,922,067 (49.0) 121.8 96.6
SH48N 132,620,143 83,943,164 (63.3) 60,714,739 (45.8) 106.7 96.3
SH48T 130,261,444 83,203,421 (63.9) 56,450,165 (43.3) 97.5 94.3
SH49N 150,088,974 124,607,378 (83.0) 92,205,060 (61.4) 160.6 97.5
SH49T 154,486,652 107,733,911 (69.7) 81,895,817 (53.0) 144.3 97.5
SH50N 156,684,408 116,450,452 (74.3) 89,703,913 (57.3) 157.8 97.9
SH50T 148,467,320 121,555,412 (81.9) 90,435,071 (60.9) 156.2 98.2
SH51N 133,692,879 99,903,393 (74.7) 75,958,803 (56.8) 132.3 97.2
SH51T 141,749,106 109,951,940 (77.6) 81,990,349 (57.8) 143.4 97.1
SH52N 121,310,408 104,169,224 (85.9) 77,096,639 (63.6) 134.2 97.5
SH52T 145,366,322 116,649,306 (80.3) 82,772,777 (56.9) 142.8 97.1
SH53N 137,496,941 109,009,039 (79.3) 85,140,313 (61.9) 149.8 97.6
SH53T 135,892,527 105,840,036 (77.9) 80,076,893 (58.9) 140.2 97.6
SH54N 153,828,328 120,765,196 (78.5) 90,628,736 (58.9) 156.9 97.7
SH54T 167,380,457 128,427,177 (76.7) 98,636,057 (58.9) 172.1 98.0
SH55N 160,101,576 137,028,025 (85.6) 104,740,233 (65.4) 182.4 98.3
SH55T 151,215,434 132,918,226 (87.9) 98,304,888 (65.0) 169.4 98.0
SH56N 170,826,963 152,859,159 (89.5) 116,900,850 (68.4) 201.7 98.6
SH56T 150,291,217 135,292,900 (90.0) 102,087,386 (67.9) 176.6 98.1
SH57N 164,562,624 140,950,814 (85.7) 104,274,204 (63.4) 180.2 97.7
SH57T 166,910,588 142,483,940 (85.4) 106,590,622 (63.6) 184.4 98.5
SH58N 158,765,599 136,063,847 (85.7) 103,308,734 (65.1) 179.7 98.4
SH58T 256,146,286 226,360,879 (88.4) 168,681,694 (65.9) 293.1 99.2
SH59N 131,869,090 107,582,973 (81.6) 80,198,460 (60.8) 140.1 97.9
SH59T 141,531,702 113,100,510 (79.9) 84,029,778 (59.4) 145.5 97.8
SH60N 233,204,919 209,703,150 (89.9) 150,638,813 (64.6) 260.3 99.1
SH60T 164,913,390 150,459,918 (91.2) 109,937,873 (66.7) 189.9 98.8
SH61N 159,817,195 140,643,778 (88.0) 106,019,548 (66.3) 184.4 98.2
SH61T 163,215,050 141,695,828 (86.8) 107,223,877 (65.7) 187.4 98.5
SH62N 158,222,605 150,463,576 (95.1) 111,403,676 (70.4) 192.2 98.7
SH62T 174,369,192 167,645,515 (96.1) 122,531,374 (70.3) 212.4 99.0
SH63N 172,873,073 160,521,206 (92.9) 116,714,622 (67.5) 200.2 99.1
SH63T 210,210,880 194,797,210 (92.7) 143,211,592 (68.1) 246.0 99.2
SH64N 105,638,112 103,775,831 (98.2) 80,371,219 (76.1) 131.3 90.2
SH64T 107,562,508 105,508,055 (98.1) 81,160,444 (75.5) 132.2 89.9
SH66N 127,938,350 126,054,904 (98.5) 98,196,686 (76.8) 160.2 91.1
SH66T 138,341,322 136,278,324 (98.5) 104,747,058 (75.7) 170.7 91.7
SH67N 116,586,515 114,970,060 (98.6) 89,608,070 (76.9) 146.1 90.5
SH67T 121,895,590 120,181,499 (98.6) 95,463,406 (78.3) 155.6 90.4
*

The neoplasia and matched normal genomes are discriminated with the use of “T” and “N,” respectively.

The mean coverage and the percent of bases (≥20 reads) were calculated onto the targeted regions (Agilent SureSelect 50 megabase exon).

A total of 672 nonsilent mutations were identified in the 44 PSH genomes (12 mutations per genome, range 0–76) (Fig. 1A and Dataset S1), corresponding to a mean rate of 0.3 somatic mutations per megabase. This finding is similar to the rates of other benign tumors [e.g., leiomyoma (13) (0.24 per megabase) and fibroadenoma (9) (0.11 per megabase)] but much lower than those observed in lung adenocarcinoma (10) (8.9 per megabase), lung squamous carcinoma (11) (8.1 per megabase), and other cancers (14) (Fig. 1B and Fig. S1). C > T substitutions are the most common mutation type (49.3%; 27.8% at CpG and 21.5% at non-CpG context) in PSHs (Fig. 1A). In contrast, C > A substitutions, the most common in lung cancer (26.8%), is less common in the PSHs (14.1%), suggesting that tumorigenic events in PSH may be different from those in lung cancer.

Fig. 1.

Fig. 1.

Landscape of somatic alterations in the PSH genomes. (A) The numbers of somatic nonsilent mutations (Upper) and types of base pair substitutions (Lower) are shown. (B) Mutation frequency in PSHs compared with those in other tumor types. Black bars represent the median values. Lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) data are from The Cancer Genome Atlas (TCGA) by Lawrence at al. (14). Fibroadenoma and leiomyoma data are from reports by Lim et al. (9) and Mehine et al. (13), respectively.

Fig. S1.

Fig. S1.

Mutation frequency in PSHs compared with those in other tumor types. Black bars represent the median values. Fibroadenoma and leiomyoma data are from reports by Lim et al. (9) and Mehine et al. (13), respectively. The other tumor data are from TCGA by Lawrence at al. (14). AML, acute myeloid leukemia; CLL, chronic lymphocytic leukemia; DLBCL, diffuse large B-cell lymphoma; ESAD, esophageal adenocarcinoma; GBM, glioblastoma multiforme; LUAD, lung adenocarcinoma; LUSC, lung squamous cell carcinoma.

AKT1 and β-Catenin Mutations in PSH Genomes.

In the PSHs, nonsilent, recurrent mutations were found in AKT1 (19 of 44 PSHs: 43.2%), CTNNB1 (β-catenin) (2 of 44), and ARID1B (2 of 44) (Fig. 2A). We also identified nonsilent mutations in an additional eight genes, which overlapped with both the Cancer Gene Census (15) and Cancer Drivers Database (16): APC, BLM, PLCG1, FAS, ATRX, EP300, KMT2D, and ATM (Fig. 2A), but no TP53 mutations were observed. Among these mutations, three truncating mutations were identified in tumor-suppressor genes (ARID1B, KMT2D, and ATM). To address whether these mutations could be causally implicated in the PSH development, we performed MutSigCV (14) and OncodriveFM (17) analyses and found that only AKT1 was significantly mutated in PSH genomes (q-value < 0.01). Key mutations were validated using Sanger sequencing or digital PCR (Fig. S2 and Table S3). Clinical and histopathological parameters could not distinguish AKT1 mutation (+) and (−) cases of PSHs (P > 0.05).

Fig. 2.

Fig. 2.

Cancer-related mutations in the PSH genomes, and a schematic diagram of AKT1 mutations. (A) Cancer-related mutations according to WES in the 44 PSH cases (discovery set). (B) Schematic diagram of the AKT1 mutations in PSHs (Upper). The x axis represents amino acid positions. The y axis represents the number of mutations. Distribution of AKT1 mutations in the discovery (44 cases) and validation (24 cases) sets are indicated.

Fig. S2.

Fig. S2.

Validation of somatic mutations. (A). Sanger sequencings of 18 genes (AKT1, ATM, ATRX, BLM, CTNNB1, EP300, FMR1, GLI1, KDM4B, KMT2D, NEDD4L, PABPC3, PIK3AP1, SETDB1, TJP1, ZMYM2, MYT1, and SPHK2) in PSH with matched normal. All of the mutations are identified in tumors, but not normal and interpreted as somatic. (B). Digital PCRs of six genes (APC, FAS, TCF7L1, FOXO1, MYT1, and MTOR) in tumor with matched normal. Red (VIC) and blue (6FAM) dots represent the reference allele and mutant allele, respectively. All of the mutations are identified in tumors, but not normal and interpreted as somatic.

Table S3.

Validation of somatic mutations

Whole-exome sequencing Validation
Gene Genomic position Ref Alt Exonic function AA change Sample ID [tumor cell content (%)] WES VAF, % (adjusted VAF, %)* Method Status VAF, % CI, %
AKT1 chr14:105246551 C T Missense p.E17K SH01 (50) 18.6 (37) Sanger sequencing Somatic
AKT1 chr14:105246443 T G Missense p.N53H SH04 (80) 37.0 (46) Sanger sequencing Somatic
AKT1 chr14:105246455 C T Missense p.E49K SH04 (80) 37.1 (46) Sanger sequencing Somatic
AKT1 chr14:105246436 A T Missense p.F55Y SH06T1 (80) 21.5 (27) Sanger sequencing Somatic
AKT1 chr14:105246445 A C Missense p.L52R SH06T1 (80) 21.3 (27) Sanger sequencing Somatic
AKT1 chr14:105246551 C T Missense p.E17K SH06T2 (50) 22.5 (45) Sanger sequencing Somatic
AKT1 chr14:105246551 C T Missense p.E17K SH20 (20) 7.1 (36) Sanger sequencing Somatic
AKT1 chr14:105246551 C T Missense p.E17K SH23 (70) 34.8 (50) Sanger sequencing Somatic
AKT1 chr14:105246551 C T Missense p.E17K SH25 (80) 38.1 (48) Sanger sequencing Somatic
AKT1 chr14:105246551 C T Missense p.E17K SH34 (60) 29.6 (49) Sanger sequencing Somatic
AKT1 chr14:105246551 C T Missense p.E17K SH36 (70) 17.5 (25) Sanger sequencing Somatic
AKT1 chr14:105243045 A T Missense p.W80R SH37 (60) 18.4 (31) Sanger sequencing Somatic
AKT1 chr14:105243048 G T Missense p.Q79K SH37 (60) 18.4 (31) Sanger sequencing Somatic
AKT1 chr14:105246551 C T Missense p.E17K SH40 (80) 39.5 (49) Sanger sequencing Somatic
AKT1 chr14:105246545 T G Missense p.I19L SH42 (70) 30.9 (44) Sanger sequencing Somatic
AKT1 chr14:105246551 C T Missense p.E17K SH42 (70) 29.4 (44) Sanger sequencing Somatic
AKT1 chr14:105246551 C T Missense p.E17K SH48 (80) 77.8 (97) Sanger sequencing Somatic
AKT1 chr14:105246551 C T Missense p.E17K SH52 (70) 33.3 (48) Sanger sequencing Somatic
AKT1 chr14:105246551 C T Missense p.E17K SH55 (60) 52.9 (88) Sanger sequencing Somatic
AKT1 chr14:105243045 A T Missense p.W80R SH56 (70) 31.9 (46) Sanger sequencing Somatic
AKT1 chr14:105243048 G T Missense p.Q79K SH56 (70) 30.5 (44) Sanger sequencing Somatic
AKT1 chr14:105243045 A T Missense p.W80R SH60 (40) 14.5 (36) Sanger sequencing Somatic
AKT1 chr14:105243048 G T Missense p.Q79K SH60 (40) 15.3 (38) Sanger sequencing Somatic
AKT1 chr14:105243045 A C Missense p.W80G SH61 (70) 27.2 (39) Sanger sequencing Somatic
AKT1 chr14:105243048 G T Missense p.Q79K SH61 (70) 27.7 (39) Sanger sequencing Somatic
AKT1 chr14:105243045 A T Missense p.W80R SH62 (50) 19.2 (38) Sanger sequencing Somatic
AKT1 chr14:105243048 G T Missense p.Q79K SH62 (50) 19.2 (38) Sanger sequencing Somatic
APC chr5:112176515 C T Missense p.R1724C SH47 (70) 5.8 (8) Digital PCR Somatic 1.39 0.90–2.16
ATM chr11:108180895 C A Nonsense p.S1924X SH59 (60) 10.8 (18) Sanger sequencing Somatic
ATRX chrX:76776914 C A Missense p.R2308S SH23 (70) 7.1 (10) Sanger sequencing Somatic
BLM chr15:91292707 A G Missense p.D70G SH51 (70) 27.8 (40) Sanger sequencing Somatic
CTNNB1 chr3:41266113 C T Missense p.S37F SH66 (60) 21 (35) Sanger sequencing Somatic
CTNNB1 chr3:41266113 C T Missense p.S37F SH18 (85) 42 (49) Sanger sequencing Somatic
EP300 chr22:41523647 G A Missense p.E355K SH18 (85) 33.1 (39) Sanger sequencing Somatic
FAS chr10:90774110 G C Missense p.C283S SH60 (40) 3.7 (9) Digital PCR Somatic 1.77 1.32–2.36
FMR1 chrX:147024825 C T Missense p.R463C SH10 (80) 36.8 (46) Sanger sequencing Somatic
GLI1 chr12:57861886 G A Missense p.R268Q SH25 (80) 28.0 (35) Sanger sequencing Somatic
KDM4B chr19:5082513 C T Nonsense p.Q306X SH06T1 (80) 25.9 (32) Sanger sequencing Somatic
KMT2D chr12:49420876 G C Nonsense p.S4958X SH18 (85) 30.9 (36) Sanger sequencing Somatic
MTOR chr1:11303294 C T Missense p.R430H SH49 (70) 4.4 (6) Digital PCR Somatic 1.12 0.72–1.73
NEDD4L chr18:56018239 G C Missense p.R416T SH18 (85) 23.0 (27) Sanger sequencing Somatic
PABPC3 chr13:25670833 G A Missense p.R166H SH41 (70) 26.2 (37) Sanger sequencing Somatic
PIK3AP1 chr10:98376435 G A Nonsense p.R659X SH66 (60) 14.9 (25) Sanger sequencing Somatic
SETDB1 chr1:150902552 G C Missense p.E124Q SH18 (85) 41.0 (48) Sanger sequencing Somatic
TCF7L1 chr2:85536268 G A Missense p.A484T SH67 (70) 6.7 (10) Digital PCR Somatic 6.68 5.97–7.46
TJP1 chr15:30012156 G C Missense p.S943C SH18 (85) 21.2 (25) Sanger sequencing Somatic
ZMYM2 chr13:20657914 A C Missense p.K1313N SH25 (80) 7.0 (9) Sanger sequencing Somatic
FOXO1 chr13:41133744 C G Missense p.L628F SH02 (70) 5.1 (7) Digital PCR Somatic 4.02 3.45–4.67
MYT1 chr20:62839489 C G Missense p.Q314E SH64 (70) 4.2 (6) Digital PCR Somatic 2.36 1.96–2.83
MYT1 chr20:62839121 G A Missense p.G191D SH10 (80) 38.9 (49) Sanger sequencing Somatic
SPHK2 chr19:49131018 G C Missense p.G158A SH66 (60) 15.7 (26) Sanger sequencing Somatic

AA, amino acid; Alt, altered allele; CI, 95% confidence interval; Ref, reference allele.

*

Adjusted VAF: 100/%tumor content × WES VAF.

All validations were performed with their paired normal sample.

AKT1 is a serine/threonine kinase that stimulates many cancer-related processes, including cell proliferation, survival, and growth (18). All 19 AKT1 mutations identified (11 p.E17K, 1 p.E17K/p.I19L, 4 p.Q79K/p.W80R, 1 p.Q79K/p.W80G, 1 p.E49K/p.N53H, and 1 p.L52R/p.F55Y) were localized to the pleckstrin homology domain (Fig. 2B), which is crucial for membrane localization and downstream activation of AKT1 (19). Not only AKT1 p.E17K, but also p.N53-, p.F55-, p.Q79-, and p.W80-altering mutations are known to promote growth factor-independent cell proliferation compared with wild-type AKT1 (20). To further assess the recurrence of AKT1 mutations in PSHs, we performed Sanger sequencing of AKT1 in an independent validation set (24 FFPE PSHs), which confirmed the high frequency of AKT1 mutations in PSHs [12 of 24 (50%): 11 p.E17K and 1 p.Q79K/p.W80R] (Table 1 and Fig. 2B). Among PSHs with p.E17K mutations, all but one harbored a single AKT1 mutation. Those PSHs with non-p.E17K mutations harbored additional AKT1 mutations (“double” AKT1 mutations). All double AKT1 mutations were detected in the identical sequencing reads with similar variant allele frequency (VAF) (Fig. S3), suggesting that the double AKT1 mutations occurred in cis configuration in the same cells. The overall AKT1 mutation prevalence in PSHs was 45.6% (31 of 68), most of which were p.E17K (23 of 68, 33.8%). Recurrent AKT1 mutations, especially p.E17K, have been detected in breast cancers (4–8%) (20, 21) but rarely in the other cancers, including lung cancers (0–0.9%) (1012).

Table 1.

Somatic mutations in AKT1 and CTNNB1

Gene Discovery set (n = 44) Validation set (n = 24) Combined set (n = 68)
Mut WT Mut rate (%) Mut WT Mut rate (%) Mut WT Mut rate (%)
AKT1 19 25 43.2 12 12 50.0 31 37 45.6
 p.E17K 11 33 25.0 11 13 45.8 22 46 32.4
 p.E17K and p.I19L 1 43 2.3 0 24 0 1 67 1.5
 p.E49K and p.N53H 1 43 2.3 0 24 0 1 67 1.5
 p.L52R and p.F55Y 1 43 2.3 0 24 0 1 67 1.5
 p.Q79K and p.W80R 4 40 9.1 1 23 4.2 5 63 7.4
 p.Q79K and p.W80G 1 43 2.3 0 24 0 1 67 1.5
CTNNB1 2 42 4.5 1 23 4.2 3 65 4.4
 p.S37F 2 42 4.5 0 24 0 2 66 2.9
 p.G38C 0 44 0 1 23 4.2 1 67 1.5

Mut, mutation; WT, wild type.

Fig. S3.

Fig. S3.

Double AKT1 mutations identified in WES. (A) WES snapshots of double AKT1 mutations. (B) VAF of AKT1 mutations. All double AKT1 mutations in each PSH were detected in the identical sequencing reads with similar VAFs, suggesting that the double AKT1 mutations occurred in cis configuration.

As for β-catenin mutations, p.S37F was identified in two different PSHs in the discovery set and p.G38C in a PSH in the validation set (3 of 68, 4.4%). β-catenin p.S37F is a hotspot mutation reported in many tumors (22, 23) and β-catenin mutations have been previously reported in PSHs (1 of 37, 2.7%, p.S33C) (6). AKT1 and β-catenin mutations did not co-occur in any of the PSHs we studied here.

Mutation Profiles in Multiple PSHs in One Patient.

Although multiple PSHs is a rare entity (24), one patient (SH06) in our study presented with two separate masses in the upper (tumor 1, T1) and lower (tumor 2, T2) lobes. To investigate their clonal origins, we compared the tumors’ germ-line and somatic variants. Almost all of the germ-line variants in the two PSH masses were shared with their matched normal (96.1% for T1 and 93.0% for T2), whereas somatic variants identified in the two PSH masses were mutually exclusive, indicating distinct clonal origins (i.e., double primary tumors) (Fig. 3). Interestingly, ATK1 mutations were identified in both lesions, but the variants were different from each other (p.L52R/p.F55Y in T1 and p.E17K in T2).

Fig. 3.

Fig. 3.

Mutation profiles of two separate PSHs from one patient. (Left) Correlation heat map of germ-line variants in the two PSHs with the matched normal. (Right) Somatic mutations identified in the two separate PSHs (SH06-T1 and SH06-T2) with the three functional categories.

AKT1 Mutations in PSHs from Histologically Different Cells.

Evidence has shown, by analyzing microsatellite patterns, that both cuboidal epithelial and polygonal stromal cells in PSHs could be monoclonal (25), but this hypothesis needs more evidence. In addition, there are still doubts about the true neoplastic nature of the components (entrapped normal epithelial cells and nonneoplastic stromal cells). We performed microdissections to procure two cell types in three PSHs and analyzed somatic and germ-line variant status, including the AKT1 mutation in the two types of cells. We found AKT1 p.E17K mutations in both cell types in the PSHs (Fig. 4), suggesting their uniclonal origin. To further validate this finding, we performed Sanger sequencing of six somatic and two germ-line variants in both epithelial and stromal cells. Regardless of somatic and germ-line event, all of the variants were detected in both cell types (Fig. S4).

Fig. 4.

Fig. 4.

Presence of AKT1 E17K mutation in both epithelial and stromal cells in represented PSH cases. (A) A sclerosing hemangioma shows both epithelial (arrows) and stromal (arrowheads) components before the microdissection. (B) The microdissection procures the epithelial cells and leaves holes behind. (C) Separately microdissected epithelial and stromal cells in three PSHs show identical mutations.

Fig. S4.

Fig. S4.

Presence of somatic (SETDB1, TJP1, KMT2D, NEDD4L, SLC25A30, and PROM2) and germ-line (BRCA2) variants in both epithelial and stromal cells in PSH cases. Separately microdissected epithelial and stromal cells in SH18 (A) and SH34 (B) show identical mutations.

CNA and Loss of Heterozygosity.

To characterize PSH genomic alterations at a copy number level, we analyzed the same 44 PSHs using the WES data (Table S4). Arm-level somatic CNAs were detected on 1q, 5p, 5q, 8p, 8q, 14q, 19p, and 19q (gains) and 13q, 15q, 16q, and 19p (losses) (7 of 44, 15.9%) (Fig. 5A), which is far fewer than that in lung cancers (10, 11), but only 1q and 14q gains were recurrent in the PSHs. The most common CNA was 14q gains (3 of 44, 6.8%), where AKT1 resides (Fig. 5B). One of the three PSHs with 14q gains also harbored AKT1 mutations, whereas the other two did not. In total, 33 PSHs (48.5%) harbored either an AKT1 mutation or 14q copy gain.

Table S4.

Copy number alterations identified across 44 PSHs by WES data

Sample ID Chr Start End Event Length Cytoband Cancer Gene Census*
SH66 1 144,009,907 249,212,668 CN Gain 105,202,762 q21.1-q44 PDE4DIP, BCL9, ARNT, TPM3, MUC1, PRCC, NTRK1, SDHC, FCGR2B, PBX1, ABL2, TPR, MDM4, ELK4, SLC45A3, H3F3A, FH
SH18 1 144,009,907 249,250,621 CN Gain 105,240,715 q21.1-q44 PDE4DIP, BCL9, ARNT, TPM3, MUC1, PRCC, NTRK1, SDHC, FCGR2B, PBX1, ABL2, TPR, MDM4, ELK4, SLC45A3, H3F3A, FH
SH51 5 1 48,400,000 CN Gain 48,400,001 p15.33-q11.1 IL7R, LIFR
SH51 5 49,411,098 180,915,260 CN Gain 131,504,163 q11.1-q35.3 IL6ST, PIK3R1, APC, PDGFRB, CD74, ITK, EBF1, RANBP17, TLX3, NPM1, NSD1
SH51 8 1 45,600,000 CN Gain 45,600,001 p23.3-q11.1 PCM1, WRN, WHSC1L1, FGFR1, HOOK3
SH51 8 46,842,549 146,364,022 CN Gain 99,521,474 q11.1-q24.3 TCEA1, PLAG1, CHCHD7, NCOA2, HEY1, COX6C, EXT1, MYC, NDRG1, RECQL4
SH36 13 30,524,423 77,870,582 CN Loss 47,346,160 q12.3-q22.3 BRCA2, LHFP, LCP1, RB1
SH42 14 19,000,023 107,349,540 CN Gain 88,349,518 q11.1-q32.33 CCNB1IP1, NKX2-1, NIN, KTN1, GPHN, TSHR, TRIP11, GOLGA5, DICER1, TCL6, TCL1A, BCL11B, AKT1
SH51 14 19,000,232 107,349,540 CN Gain 88,349,309 q11.1-q32.33 CCNB1IP1, NKX2-1, NIN, KTN1, GPHN, TSHR, TRIP11, GOLGA5, DICER1, TCL6, TCL1A, BCL11B, AKT1
SH53 14 19,000,265 107,349,540 CN Gain 88,349,276 q11.1-q32.33 CCNB1IP1, NKX2-1, NIN, KTN1, GPHN, TSHR, TRIP11, GOLGA5, DICER1, TCL6, TCL1A, BCL11B, AKT1
SH60 15 20,000,050 102,531,392 CN Loss 82,531,343 q11.1-q26.3 C15orf55, BUB1B, FLJ27352, TCF12, PML, NTRK3, IDH2, CRTC3, BLM
SH18 16 46,500,741 88,125,293 CN Loss 41,624,553 q11.2-q24.2 CYLD, HERPUD1, CDH11, CBFB, CDH1, MAF
SH66 19 1 14,064,025 CN Loss 14,064,025 p13.3-p13.12 FSTL3, STK11, TCF3, GNA11, SH3GL1, MLLT1, DNM2, SMARCA4, LYL1
SH18 19 1 19,664,859 CN Gain 19,664,859 p13.3-p13.11 FSTL3, STK11, TCF3, GNA11, SH3GL1, MLLT1, DNM2, SMARCA4, LYL1, BRD4, TPM4, JAK3, ELL
SH18 19 35,471,245 56,507,071 CN Gain 21,035,827 q13.11-q13.43 AKT2, CD79A, CIC, BCL3, CBLC, ERCC2, KLK2, PPP2R1A, ZNF331, TFPT
*

Cancer Gene Census (cancer.sanger.ac.uk/census).

Fig. 5.

Fig. 5.

CNAs identified across 44 PSH genomes. (A) The heatmap summarizes chromosomal copy gains (red) and copy losses (blue) in the tumors; each row represents PSH cases. The red boxes denote the arm-level copy gains and the blue boxes denote the arm-level copy losses. Copy number gains on 1q (SH18 and SH66) and 14q (SH42, SH51, and SH53) are identified recurrently. (B) Genome-wide log2 ratio plots from three PSHs with copy number gains on 14q. The red arrows represent the 14q copy gains. The x axis represents individual chromosomes and the y axis represents the relative depth ratio (tumor/matched normal) in log2 scale.

We also assessed the B-allele profiles and identified three copy-neutral loss-of-heterozygosity (LOH) events (Fig. 6). Two of these events (SH48 and SH55) harbored LOH on 14q and co-occurred with AKT1 p.E17K mutation. Mean VAF of AKT1 mutations in the two PSHs with 14q LOH was 2.5 times higher than that without 14p LOH (65.4% vs. 25.6%, respectively) (Fig. 6B), suggesting that the 14q LOH might have occurred after AKT1 mutation events in these cases. Wide distribution of AKT1 VAFs may be a result of subclonal nature of AKT1 mutations in some samples or nonneoplastic cell contamination. When looking at the histology of PSHs, we observed that nonneoplastic stromal components (for example, inflammatory cells) besides the neoplastic polygonal stromal cells were embedded in the analyzed tissues for WES at various degrees (Fig. S5 and Table S3). Adjusted VAFs considering tumor cell contents in AKT1-mutated cases were 25–49% in non-LOH cases and 88–97% in LOH cases (Table S3), suggesting that the AKT1 mutations in PSH may be clonal. The other one (SH18) harbored 59-megabase–sized LOH on chromosome 10 (10q22.2-q26.3), which has been observed in PSHs previously (4). Tumor-suppressor genes PTEN and TCF7L2 reside in this area.

Fig. 6.

Fig. 6.

Copy-neutral LOH events identified across 44 PSH genomes. (A) List of copy-neutral LOH events identified in this study. Three PSHs with copy-neutral LOH either on 14q or 10q. (B) VAF of AKT1 mutations. The red circle represents PSHs with 14q LOH. Mean VAF of AKT1 mutations in the PSHs with 14q LOH is 2.5 times higher than those without 14p LOH (65.4% vs. 25.6%, respectively). (C) Genome-wide B allele frequency (BAF) plot of the three PSHs with copy-neutral LOH. Red boxes represent copy-neutral LOH events. The x axis represents individual chromosomes and the y axis represents the BAF.

Fig. S5.

Fig. S5.

Histology of sclerosing hemangiomas. Sclerosing hemangiomas with AKT1 mutations (SH01, -04, -6T1, -6T2, -18, -20, -25, -34, -36, -37, -40, -42, -48, -52, -55, -56, -60, -61, and -62) and with other mutations (SH18, -23, -47, -51, -59, and -66). Nonneoplastic stromal components (for example, inflammatory cells) besides the neoplastic polygonal stromal cells were embedded in the analyzed tissues for WES at various degrees. Case SH20 shows massive infiltration of lymphoid cells in the tumor (marked in circle). Case SH20 showed WES VAF of AKT1-mutation was 7.1% (Table S3), but it was adjusted to VAF 36% when considering the huge infiltration of inflammatory cells (20% of tumor cell content).

Pathway Analysis.

To further gain insights into the role of genomic alterations underlying PSH development, we analyzed the genome data through pathway analysis using the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Several mutated genes in PSHs were significantly enriched for cell survival, proliferation, growth, and angiogenesis activities (Table S5). Of note, AKT1 activation is closely connected to these pathways (Fig. 7A). We identified mutations in multiple components of the AKT/GSK3/β-catenin signalings, including CTNNB1, APC, and TCF7L1. In addition, a copy loss of STK11 and mutations in mammalian target of rapamycin (MTOR) and EIF4E2 in PI3K/AKT/mTOR signaling pathways, as well as mutations in MYT1 and FOXO1 responsible for cell cycle regulation and cell survival, were detected in the PSH genomes (Fig. 7B). Interestingly, several gene alterations are related to the VEGF signaling pathway that activates angiogenesis, possibly suggesting their roles in the vascular phenotype (“hemangioma”) of PSH. AKT1 has been engaged as a target in ongoing clinical trials (26), suggesting that AKT1 inhibitors may have potential therapeutic value in PSH.

Table S5.

Pathway analysis of mutations using IntOGen v2.4.1 software

KEGG identifier Description FM-bias Samples Recurrence Mutation frequency (%)
hsa05215 Prostate cancer 8.4 × 10−18 44 25 56.8
hsa04150 Mammalian target of rapamycin (mTOR) signaling pathway 3.2 × 10−17 44 22 50.0
hsa04910 Insulin signaling pathway 3.2 × 10−17 44 25 56.8
hsa05218 Melanoma 4.8 × 10−17 44 20 45.5
hsa05222 Small cell lung cancer 7.8 × 10−16 44 19 43.2
hsa04510 Focal adhesion 9.9 × 10−16 44 26 59.1
hsa04725 Cholinergic synapse 9.9 × 10−16 44 21 47.7
hsa05166 HTLV-I infection 1.6 × 10−15 44 25 56.8
hsa04920 Adipocytokine signaling pathway 1.7 × 10−15 44 21 47.7
hsa05212 Pancreatic cancer 6.4 × 10−15 44 20 45.5
hsa05220 Chronic myeloid leukemia 6.4 × 10−15 44 19 43.2
hsa04630 Jak-STAT signaling pathway 8.1 × 10−15 44 22 50.0
hsa05210 Colorectal cancer 1.3 × 10−14 44 23 52.3
hsa04210 Apoptosis 1.3 × 10−14 44 23 52.3
hsa05221 Acute myeloid leukemia 1.3 × 10−14 44 22 50.0
hsa04973 Carbohydrate digestion and absorption 2.5 × 10−14 44 20 45.5
hsa04728 Dopaminergic synapse 3.4 × 10−14 44 23 52.3
hsa05200 Pathways in cancer 5.6 × 10−14 44 27 61.4
hsa05161 Hepatitis B 7.1 × 10−14 44 21 47.7
hsa05214 Glioma 9.6 × 10−14 44 21 47.7
hsa04914 Progesterone-mediated oocyte maturation 1.1 × 10−13 44 22 50.0
hsa05211 Renal cell carcinoma 1.1 × 10−13 44 20 45.5
hsa05152 Tuberculosis 3.9 × 10−13 44 25 56.8
hsa04066 HIF-1 signaling pathway 3.9 × 10−13 44 22 50.0
hsa04620 Toll-like receptor signaling pathway 4.5 × 10−13 44 22 50.0
hsa05162 Measles 6.0 × 10−13 44 21 47.7
hsa04010 MAPK signaling pathway 9.1 × 10−13 44 23 52.3
hsa05142 Chagas disease (American trypanosomiasis) 2.3 × 10−12 44 22 50.0
hsa04151 PI3K–Akt signaling pathway 2.9 × 10−12 44 29 65.9
hsa04660 T-cell receptor signaling pathway 2.9 × 10−12 44 21 47.7
hsa04662 B-cell receptor signaling pathway 2.0 × 10−11 44 23 52.3
hsa04370 VEGF signaling pathway 3.2 × 10−11 44 21 47.7
hsa05160 Hepatitis C 3.7 × 10−11 44 23 52.3
hsa05145 Toxoplasmosis 3.7 × 10−11 44 22 50.0
hsa04012 ErbB signaling pathway 1.3 × 10−10 44 22 50.0
hsa04666 Fcγ R-mediated phagocytosis 1.5 × 10−10 44 22 50.0
hsa05213 Endometrial cancer 4.5 × 10−10 44 25 56.8
hsa05164 Influenza A 1.7 × 10−09 44 25 56.8
hsa04062 Chemokine signaling pathway 1.3 × 10−08 44 23 52.3
hsa04664 Fcε RI signaling pathway 1.5 × 10−08 44 21 47.7
hsa04380 Osteoclast differentiation 1.5 × 10−08 44 20 45.5
hsa04530 Tight junction 4.9 × 10−08 44 30 68.2
hsa05223 Nonsmall cell lung cancer 1.7 × 10−07 44 21 47.7
hsa05169 Epstein–Barr virus infection 6.5 × 10−07 44 21 47.7
hsa04722 Neurotrophin signaling pathway 1.1 × 10−05 44 24 54.5
hsa04540 Gap junction 2.2 × 10−04 44 5 11.4
hsa04310 Wnt signaling pathway 0.002 44 9 20.5
hsa04730 Long-term depression 0.003 44 3 6.8
hsa04916 Melanogenesis 0.004 44 7 15.9
hsa04060 Cytokine-cytokine receptor interaction 0.006 44 10 22.7
hsa00310 Lysine degradation 0.009 44 5 11.4
hsa04810 Regulation of actin cytoskeleton 0.013 44 11 25.0
hsa04520 Adherens junction 0.014 44 7 15.9
hsa04720 Long-term potentiation 0.014 44 7 15.9
hsa05143 African trypanosomiasis 0.016 44 4 9.1
hsa04972 Pancreatic secretion 0.017 44 4 9.1
hsa04726 Serotonergic synapse 0.023 44 9 20.5
hsa04120 Ubiquitin mediated proteolysis 0.027 44 9 20.5
hsa04110 Cell cycle 0.029 44 7 15.9
hsa05217 Basal cell carcinoma 0.055 44 6 13.6
hsa04144 Endocytosis 0.056 44 12 27.3
hsa04723 Retrograde endocannabinoid signaling 0.080 44 8 18.2
hsa03013 RNA transport 0.091 44 12 27.3
hsa04270 Vascular smooth muscle contraction 0.096 44 8 18.2
hsa05202 Transcriptional misregulation in cancer 0.146 44 8 18.2
hsa02010 ABC transporters 0.162 44 5 11.4
hsa00600 Sphingolipid metabolism 0.175 44 3 6.8
hsa04713 Circadian entrainment 0.201 44 6 13.6
hsa04912 GnRH signaling pathway 0.201 44 6 13.6
hsa04142 Lysosome 0.304 44 11 25.0
hsa05032 Morphine addiction 0.309 44 7 15.9
hsa04114 Oocyte meiosis 0.309 44 5 11.4
hsa01100 Metabolic pathways 0.342 44 23 52.3
hsa05203 Viral carcinogenesis 0.373 44 6 13.6
hsa04020 Calcium signaling pathway 0.376 44 11 25.0
hsa05412 Arrhythmogenic right ventricular cardiomyopathy (ARVC) 0.433 44 11 25.0
hsa03440 Homologous recombination 0.477 44 4 9.1
hsa04064 NF-κB signaling pathway 0.492 44 5 11.4
hsa00230 Purine metabolism 0.597 44 9 20.5
hsa03015 mRNA surveillance pathway 0.681 44 6 13.6
hsa04070 Phosphatidylinositol signaling system 0.717 44 6 13.6
hsa05016 Huntington's disease 0.717 44 5 11.4
hsa04360 Axon guidance 0.756 44 3 6.8
hsa03040 Spliceosome 0.846 44 7 15.9
hsa04670 Leukocyte transendothelial migration 0.899 44 11 25.0
hsa05414 Dilated cardiomyopathy 0.899 44 8 18.2
hsa05010 Alzheimer's disease 0.899 44 7 15.9
hsa05410 Hypertrophic cardiomyopathy (HCM) 0.899 44 7 15.9
hsa05110 Vibrio cholerae infection 0.949 44 10 22.7
hsa00562 Inositol phosphate metabolism 0.949 44 5 11.4
hsa04650 Natural killer cell mediated cytotoxicity 0.963 44 7 15.9
hsa05168 Herpes simplex infection 0.963 44 7 15.9
hsa04512 ECM-receptor interaction 0.969 44 4 9.1
hsa05100 Bacterial invasion of epithelial cells 0.994 44 7 15.9
hsa05130 Pathogenic Escherichia coli infection 0.996 44 9 20.5
hsa04330 Notch signaling pathway 1.000 44 9 20.5
hsa05131 Shigellosis 1.000 44 5 11.4
hsa05120 Epithelial cell signaling in Helicobacter pylori infection 1.000 44 5 11.4

Fig. 7.

Fig. 7.

Somatically altered pathways in PSH. (A) Schematic representation of possible genetic mechanisms for PSH development. Predicted pathways from mutation data are depicted. Genes are shown along with the percentage of somatic mutations and CNAs. A potential druggable gene is highlighted in green lightning symbols. (B) Somatic mutations and CNAs in the discovery (44 cases) and validation (24 cases) sets of PSHs.

Discussion

In this study, we attempted to identify the genetic alterations of PSH genomes by WES. First, we observed highly frequent AKT1 gene alterations (somatic mutations and copy gains) in the PSH genomes. Based on the current knowledge of AKT1 mutations (oncogenic activities and recurrent hotspot mutations) (20, 27, 28), our data suggest that AKT1 gene alterations are the most common genetic driver that might contribute to the PSH development. Recurrent AKT1 mutation was first reported in breast cancers and subsequently in other tumors (29). In these tumors, however, the frequency of AKT1 mutations was much lower (∼8%) than that of the PSHs in our study. When combining AKT1 mutations with AKT1 copy gain, AKT1 genetic alterations in PSH reached 48.5%, which is the highest incidence of AKT1 alterations in human tumors (the COSMIC database). We also observed β-catenin mutation in 4.4% of the PSHs that was mutually exclusive with AKT1 mutation in PSHs. In addition, several tumor-related genes, including ARID1B, APC, BLM, PLCG1, FAS, ATRX, EP300, KMT2D, and ATM were detected in the PSHs at low incidences (2.3–4.5%). As for CNAs, 15.9% of the PSHs harbored alterations, whereas most PSHs (84.1%) did not exhibit any noticeable CNAs. Such a high incidence of oncogenic AKT1 alterations and a low incidence of other mutations, as well as few CNAs in the PSHs, suggest that AKT1 alterations are likely key players in PSH development. Other mutations and CNAs might possibly contribute to PSH pathogenesis, but their causal roles or the roles in conjunction with AKT1 signaling remain to be clarified.

Of note, either AKT1 or β-catenin mutation in malignant tumors usually co-occurs with other driver genomic alterations (22, 30, 31). However, AKT1 mutations in benign tumors, such as meningiomas and PSHs, and β-catenin mutations in pilomatricoma do not usually co-occur with each other or other known driver mutations (3234). It is possible that AKT1 or β-catenin mutation alone is able to produce a benign tumor but not a malignant tumor. AKT1 mutation itself has a weak transforming activity (35), which might make the cells proliferate and change morphology but not acquire the capability to further progress to malignancy.

The histogenesis of the dual cells present in PSHs has long puzzled scientists. One theory suggests that both cuboidal epithelial and polygonal stromal cells represent a neoplastic origin by identifying monoclonality of these two cells (3). The other theory suggests that the polygonal cell population may represent neoplastic cells, whereas the cuboidal cells represent entrapped epithelial cells from immunohistochemical analysis (25). Our study identified that both of the cell components in PSHs, cuboidal epithelial and polygonal stromal, harbored the same somatic and germ-line variants, supporting the former theory. Our data suggest that both cells are a true neoplastic component and that they may be histologically different but not genetically. Some nonneoplastic respiratory epithelial cells may be entrapped in the PSHs, but many of the cuboidal epithelial cells, especially deep inside of the PSHs, may represent neoplastic cells. It could be possible that the microdissection was not specific enough and that both components were present in the preparations. However, this possibility, if any, with a minor contamination of stromal cells into epithelial cells, may be low because the height of mutant peaks in the sequencing (Fig. 4 and Fig. S4) are similar (even higher in epithelial cells in some cases) between the two cells. Furthermore, we discovered that multinodular PSHs in a patient harbored two different AKT1 mutation variants, indicating that the multinodularity in PSH may not result from metastasis.

Tumor-suppressor genes constitute the largest group of hereditary cancer genes, whereas only a few oncogenes—including RET, MET, KIT, and AKT1—are associated with hereditary tumor development (36). For example, Proteus syndrome, a congenital disease involving overgrowth of skin, muscles, fatty tissues, and blood vessels, as well as pulmonary cysts and venous dilatation, is caused by somatic mosaic mutations of AKT1 p.E17K (37). Afflicted individuals are at increased risk for developing benign tumors of the ovary, meninx, and the parotid gland. However, the risk of malignant tumor is not increased (38). Congenital AKT1 p.E17K mutations associated with benign tumors and vascular lesions might explain the role of somatic AKT1 mutation in the PSH phenotype.

Despite the predominant prevalence of AKT1 mutations, ∼40% of PSHs exhibited neither driver mutation nor CNA, suggesting epigenetic or not yet identified genetic origin of this disease. Further genetic or epigenetic studies with AKT1 mutation-negative PSHs will be required to discover other driver alterations of PSH.

In conclusion, our study has revealed genomic differences between PSHs and lung adenocarcinomas, including a high rate of AKT1 mutation and few CNAs in PSH. These genomic features of PSH identified in the present study provide clues to understanding the benign biology of PSH and for differential genomic diagnosis of lung tumors.

Materials and Methods

Sclerosing Hemangioma Tissues.

Approval for this study was obtained from the Institutional Review Board at the Catholic University of Korea, College of Medicine. Clinicopathologic features of the patients are summarized in Table S1. The PSH patients in our study did not show any congenital abnormalities of Proteus syndrome. All of the patients were Korean. Fresh-frozen tissues from eight patients with PSH were obtained from the Tissue Banks of Seoul St. Mary Hospital of Catholic University (Seoul, Korea), Guro Hospital of Korea University (Seoul, Korea), and Pusan National University Hospital (Pusan, Korea). Initially, frozen tissues from the tissue banks were cut, stained with H&E, and examined under a microscope by a pathologist, who identified areas rich in PSH tumor cells. To procure matched normal tissues from each patient, we used lung tissues that were confirmed to be free of tumor cells based on examination under the microscope. The purities of PSH tumor cells were ∼20–80%. In addition, 36 FFPE PSHs from 35 patients (two PSHs in one patient) were used as the discovery set for WES. Another 24 FFPE PSHs were used for validation of important alterations. The FFPE tissues were archival tissues collected from Seoul St. Mary Hospital (Seoul, Korea), Incheon St. Mary Hospital (Incheon, Korea), Ujeongbu St. Mary Hospital (Ujeongbu, Korea), St. Vincent Hospital (Suwon, Korea), St. Paul Hospital (Seoul, Korea), Bucheon St. Mary Hospital (Bucheon, Korea), Yeouido St. Mary Hospital (Seoul, Korea), and Kyungpook National University Hospital (Daegu, Korea) under the permission of the Institutional Review Board at the Catholic University of Korea, College of Medicine (MC14SISI0002). The tumor cells and normal cells were separately procured from H&E-stained slides. For genomic DNA extraction, we used the DNeasy Blood & Tissue Kit (Qiagen).

WES.

WES was performed for the genomic DNA obtained from tumor and matched normal specimen using the Agilent SureSelect Human All Exome 50Mb kit (Agilent Technologies) and Illumina HiSeq2000 platform, according to the manufacturer’s instructions. Acquisition and processing of the sequencing data were performed as previously described (39). A Burrows–Wheeler aligner was used to align the sequencing reads onto the human reference genome (UCSC hg19). The aligned sequencing reads were evaluated using Qualimap (40), and the sequences were deposited in the Sequence Read Archive database (Project ID: PRJNA297066).

Identification of Somatic Variants.

Somatic variants were identified using MuTect (41) and SomaticIndelDetector (42) for point mutations and indels, respectively. The ANNOVAR package (43) was used to select somatic variants located in the exonic sequences and to predict their functional consequences. To obtain reliable and robust mutation calling, the following somatic variants were eliminated: (i) read depth fewer than 20 in either the tumor or matched normal; (ii) polymorphisms referenced in either 1000 Genomes Project, Exome Aggregation Consortium, or Exome Sequencing Project with a minor allele frequency greater than 2%; and (iii) variants with VAF between 45% and 55% in a copy-neutral region. Finally, validated variants according to Sanger sequencing or digital PCR were manually curated.

Cancer-Related Mutations and Validation.

We performed MutSigCV (14) and OncodriveFM (17) analyses to identify and validate cancer-related mutations. Significantly mutated genes with q-value < 0.01 were considered driver mutations. Cancer-related genes are also defined as those identified in both the Cancer Gene Census (15) and Cancer Drivers Database (16). We validated 51 mutations of 23 genes using either digital-PCR or Sanger sequencing. Details are summarized in Table S3. Digital-PCR was performed using the TaqMan Genotyping assay and the QuantStudio 3D digital PCR system (Life Technologies) as described elsewhere (44). The digital PCR data were analyzed using the Relative Quantification module of the QuantStudio 3D AnalysisSuite Cloud Software. The confidence level was set to 95%, and the desired precision value was 10%. In addition, to further assess the recurrent mutations in PSHs, we performed Sanger sequencing of AKT1 and CTNNB1 in the independent validation set (24 FFPE PSHs).

DNA Copy Number and LOH Analysis.

DNA copy number and LOH were estimated using WES data. The ngCGH module and RankSegmentation statistical algorithm in NEXUS software v7.5 (Biodiscovery) were used to define CNAs of each sample (44). We inferred the LOH events using Sequenza (45). All of the identified CNAs and LOH events were manually curated in terms of depth ratio and B allele frequency.

Supplementary Material

Supplementary File
pnas.1606946113.sd01.xlsx (77.6KB, xlsx)

Acknowledgments

This study was supported by National Research Foundation of Korea (Grant 2012R1A5A2047939), the Korean Health Industry Development Institute of the Ministry of Health and Welfare of Korea (Grant HI13C2148), and the National Cancer Institute of the NIH (Grant P30CA034196). C.L. is a distinguished Ewha Womans University Professor supported in part by the Ewha Womans University Research grant of 2015.

Footnotes

The authors declare no conflict of interest.

This article is a PNAS Direct Submission. J.D.M. is a Guest Editor invited by the Editorial Board.

Data deposition: The sequences have been deposited in the NCBI Sequence Read Archive database, www.ncbi.nlm.nih.gov/sra (Project ID: PRJNA297066).

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1606946113/-/DCSupplemental.

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Supplementary Materials

Supplementary File
pnas.1606946113.sd01.xlsx (77.6KB, xlsx)

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