Abstract
Smoking is known to influence messenger RNA (mRNA) expression in colorectal cancer (CRC) cases. As microRNAs (miRNAs) are known repressors of mRNAs, we hypothesize that smoking may influence miRNA expression, thus altering mRNA expression. Our sample consisted of 1447 CRC cases that had normal colorectal mucosa and carcinoma miRNA data and lifestyle data. We examined current smoking, current versus never and former versus never (C/F/N) smoking1, and pack-years smoked with miRNA expression in normal mucosa as well as differential miRNA expression between paired normal and carcinoma tissue for colon and rectal tissue to determine associations between smoking and miRNA expression. We adjusted for multiple comparisons using the Benjamini Hochberg false discovery rate (FDR).
Significant associations were seen for rectal differential miRNA expression only. We analyzed miRNAs significantly associated with smoking with CIMP and MSI status, using a polytomous logistic regression. Two hundred and thirty-one miRNAs were differentially expressed with current smoking, 172 with C/F/N, and 206 with pack-years smoked; 111 were associated with all three. Forty-three miRNAs were unique to current smoking, 14 were unique to C/F/N and 57 were unique to pack years smoked. Of the 306 unique miRNAs associated with cigarette smoking, 41 were inversely associated and 200 were directly associated with CIMP high or MSI tumor molecular phenotype for either colon or rectal cancer. Our results suggest that cigarette smoking can alter miRNA expression and, given associations with CIMP high and MSI tumor molecular phenotype, it is possible that smoking influences tumor phenotype through altered miRNA expression.
Keywords: microRNAs, smoking, rectal, neoplasms, life style, CIMP, MSI
1. Introduction
Long-term and current cigarette smoking has been shown to increase risk of developing and dying from many cancers, including CRC (1–3). We have previously shown that certain mRNAs are differentially expressed in current smokers as compared to people who have never smoked (4). MiRNAs are small (~22 nucleotides), endogenously expressed, non-coding RNA molecules that bind to the 3’ untranslated region of the mRNAs to alter mRNA translation into protein (5). Typically, miRNAs cause mRNA degradation or block translation (6), however there is some evidence that in certain environments miRNAs may facilitate mRNA translation (7). MiRNAs have been shown to be differentially expressed in carcinoma tissue as compared to normal tissue (8–10), and, as miRNAs regulate many different target genes (6, 11), they have been implicated as key effector molecules in the carcinogenesis process (12). MiRNAs influence the translation of mRNAs, which we have seen are impacted by current cigarette use; it is possible, then, that smoking alters miRNA expression and contributes to the previously observed altered mRNA levels.
In this study we evaluate whether current smoking and pack-years of cigarettes smoked influence miRNA expression in CRC in both normal colon and rectal mucosa and differential (paired carcinoma tissue compared to normal colon and rectal mucosa) expression. We hypothesize that smoking will influence miRNA levels, with greater or temporal exposure having a larger influence on differential expression.
2. Materials and methods
2.1 Study population
Data come from participants in the population-based Diet, Activity, and Lifestyle study that were recruited from Utah or the Kaiser Permanente Medical Care Program of Northern California (KPMCP). Colon cancer cases were identified as having a primary adenocarcinoma diagnosed between 1 October 1991 and 30 September 1994, while rectal cancer cases were diagnosed between May 1997 and May 2001. Eligible cases were between 30 and 79 years of age at diagnosis, currently living in the study area, spoke English and were able to complete an interview, and had no prior history of CRC, Crohn’s disease, ulcerative colitis, or known familial adenomatous polyposis. This study was approved by the Institutional Review Board at the University of Utah; all participants signed an informed consent form.
2.2 Smoking Data
Data were collected by trained and certified interviewers using laptop computers. All interviews were audio-taped as previously described and reviewed for quality control purposes (13). The referent period for the study was two years prior to diagnosis for cases. As part of the study questionnaire, information was collected on cigarette smoking history. Anyone who reported having smoked at least 100 cigarettes in their lifetime was considered to have been a cigarette smoker. Regular smokers were then defined as anyone having smoked at least one cigarette a day for six months or longer. Data also were collected for start and stop dates for smoking in order to calculate pack-years smoked. We collected data on number of cigarettes smoked per day, and used amount smoked along with years smoked to calculate the pack-years. The pack-years variable was defined as the number of years a subject smoked a pack or 20 cigarettes a day. For rectal cancer subjects we also analyzed miRNA expression with exposure to smoke of others in and outside of the house in non-smokers only.
2.3 MiRNA Processing
RNA was extracted from formalin-fixed paraffin embedded tissues and processed as previously described (14). 100 ng total RNA was labeled with Cy3 and hybridized to Agilent Human miRNA Microarrays V19.0 and were scanned on an Agilent SureScan microarray scanner model G2600D using Agilent Feature Extract software v.11.5.1.1. Data were required to pass stringent QC parameters established by Agilent that included tests for excessive background fluorescence, excessive variation among probe sequence replicates on the array, and measures of the total gene signal on the array to assess low signal. Samples that failed to meet QC standards were repeated, and if a sample failed QC assessment a second time the sample was deemed to be of poor quality and was excluded from down-stream analysis. The Agilent platform was found to be highly reliable (r=0.98), and to have reasonable agreement with NanoString (15) as well as excellent agreement with qRT-PCR (8). For unpaired samples due to missing normal scans, we imputed values whenever possible for normal mucosa as previously described (16). In order to minimize differences that could be attributed to the array, amount of RNA, location on array, or other factors that could erroneously influence expression, total gene signal was normalized by multiplying each sample by a scaling factor which was the median of the 75th percentiles of all the samples divided by the 75th percentile of each individual sample (17). This scaling factor was implemented using SAS 9.4.
2.4 Statistical Analysis
Our sample consisted of 1447 carcinoma tissue and paired normal colorectal mucosa from subjects for whom smoking data were available. In this analysis, we included only the miRNAs in which at least 20% of the samples had some level of detectable expression in the tissue(s) of interest. We stratified the data by tumor site, i.e. colon vs. rectal cancer. The number of miRNAs analyzed varied from 766 to 817 depending on tissue and tumor site. We examined four smoking variables (ever smoked, smoking status (current/former/never), average number of cigarettes smoked per day, and pack-years smoked for rectal cancer only, since years starting and stopped was not collected for colon cancer cases) to determine if there was an association between smoking cigarettes and miRNA expression. We examined associations in both normal colon and rectal mucosa and the difference in expression between paired carcinoma tissue and normal colon and rectal mucosa. This was done by fitting a linear model to the log base 2 transformed miRNA expression levels and adjusting for age at diagnosis, study center and sex. P-values were generated using the bootstrap method by creating a distribution of 10,000 F statistics derived by resampling the residuals from the null hypothesis model of no association between the lifestyle variables and the miRNAs (18) using the boot package in R. Associations were considered significant if the Benjamini Hochberg (FDR) adjusted p-values were less than 0.05 (19). We standardized the slopes by transforming the miRNAs and continuous smoking variables to standard normal in order to better compare the results across the miRNA and cigarette smoking variables.
We analyzed any miRNAs that were significantly differentially expressed between carcinoma and normal mucosa for any smoking variable with CIMP and MSI tumor molecular phenotype in rectal and colon cancer subjects. Using a polytomous logistic regression we assessed associations for CIMP High/MSS, CIMP Low/MSI, and CIMP High/MSI relative to CIMP Low/MSS. For this analysis we report odds ratios and 95 percent confidence intervals.
3. Results
The study population consisted of 892 colon cancer cases and 555 rectal cancer cases; approximately 54% of cases were male and 46% were female for colon cases, and 57% of cases were male and 43% were female for rectal cases (Table 1). Approximately 11% of rectal cases and 14% of colon cases had a family history of CRC. About 55% of rectal cases and 58% of colon cases had ever smoked, with approximately 16% of rectal cases and 14% of colon cases smoking at the time of diagnosis. The average age at diagnosis was approximately 65 years old for colon subjects and 62 years old for rectal subjects. The average years smoked was 17.5 for colon cases and 14.8 for rectal cases; the average pack-years smoked for rectal cases was 16.1 pack-years.
Table 1.
Descriptive Table.
| Colon | Rectal | ||||
|---|---|---|---|---|---|
| N/Mean | (%/SD) | N/Mean | (%/SD) | ||
| Age at diagnosis | 64.7 | (9.5) | 61.8 | (10.8) | |
| Sex | Male | 485 | (54.4) | 316 | (56.9) |
| Female | 407 | (45.6) | 239 | (43.1) | |
| Center | Kaiser | 626 | (70.2) | 340 | (61.3) |
| Utah | 266 | (29.8) | 215 | (38.7) | |
| Family history of colorectal cancer | No | 770 | (86.3) | 493 | (89.0) |
| Yes | 122 | (13.7) | 61 | (11.0) | |
| Ever Smoked | No | 373 | (41.9) | 252 | (45.4) |
| Yes | 517 | (58.1) | 303 | (54.6) | |
| Smoking Status | Never | 373 | (41.9) | 264 | (47.6) |
| Former | 390 | (43.8) | 200 | (36.0) | |
| Current | 127 | (14.3) | 91 | (16.4) | |
| Average # of cigarettes/day | None | 373 | (42.0) | 264 | (47.7) |
| 1–10 | 142 | (16.0) | 74 | (13.4) | |
| 11–20 | 215 | (24.2) | 146 | (26.4) | |
| >20 | 159 | (17.9) | 70 | (12.6) | |
| Years smoked | 17.5 | (18.3) | 14.8 | (17.8) | |
| Pack-years smoked | 16.1 | (23.4) | |||
We saw significant findings for differential miRNA expression, between carcinoma and normal colonic mucosa tissue, for rectal cancer only. We saw no significant findings for exposure to smoke of others in non-smoking rectal cancer cases. After adjustment for multiple comparisons, 231 miRNAs had significantly different differential expression (carcinoma tissue compared to normal colon and rectal mucosa) in current smokers as compared to cases that never smoked or were a former smoker. Thirty-six of these miRNAs were downregulated with current smoking and 195 were upregulated. One hundred and seventy-two miRNAs were associated significantly with C/F/N smoking; four of these miRNAs changed direction from never to former and from never to current, while 168 had differential expression increase or decrease in the same direction progressively from never to former to current. Of the 168 that had progressive changes in expression, 138 were upregulated and 30 were downregulated in current versus former or never smokers. Two hundred and six miRNAs were associated with pack-years smoked; of these, 37 were downregulated and 169 were upregulated with more pack-years smoked. Forty-three miRNAs were unique to current smokers (Table 2), 14 were unique to C/F/N smoking (Table 3), and 57 were unique to pack-years smoked (Table 4).
Table 2.
MiRNAs differentially expressed between carcinoma tissue and normal rectal mucosa and associated with only current smoking.
| Never & Former | Current | ||||||
|---|---|---|---|---|---|---|---|
| Mean miRNA Expression | Mean miRNA Expression | P-values | |||||
| miRNA | Carcinoma Tissue | Normal Mucosa | Carcinoma Tissue | Normal Mucosa | Beta1 | Raw | FDR |
| hsa-miR-1208 | 26.48 | 30.79 | 28.12 | 30.02 | 0.3125 | 0.0077 | 0.0328 |
| hsa-miR-1224-5p | 692.89 | 820.71 | 756.13 | 800.96 | 0.3061 | 0.0076 | 0.0328 |
| hsa-miR-1236-5p | 127.80 | 136.98 | 140.37 | 134.74 | 0.2980 | 0.0084 | 0.0344 |
| hsa-miR-1276 | 2.32 | 2.00 | 1.71 | 2.20 | −0.3268 | 0.0057 | 0.0280 |
| hsa-miR-1914-3p2 | 106.17 | 121.11 | 117.74 | 121.75 | 0.3159 | 0.0066 | 0.0301 |
| hsa-miR-196b-5p2 | 14.93 | 2.31 | 13.55 | 2.43 | −0.2829 | 0.0135 | 0.0456 |
| hsa-miR-197-5p | 2553.58 | 2891.42 | 2837.27 | 2837.46 | 0.2992 | 0.0075 | 0.0328 |
| hsa-miR-199b-5p | 3.83 | 0.96 | 2.70 | 1.30 | −0.3156 | 0.0053 | 0.0277 |
| hsa-miR-2276 | 89.25 | 86.67 | 96.83 | 83.14 | 0.3298 | 0.0035 | 0.0230 |
| hsa-miR-3174 | 12.41 | 10.63 | 11.76 | 11.19 | −0.2838 | 0.0149 | 0.0495 |
| hsa-miR-3187-5p | 3.84 | 2.27 | 3.10 | 2.52 | −0.3043 | 0.0072 | 0.0321 |
| hsa-miR-3189-5p | 5.19 | 5.12 | 4.40 | 5.45 | −0.3166 | 0.0066 | 0.0301 |
| hsa-miR-320e | 34.84 | 36.31 | 40.31 | 37.27 | 0.2885 | 0.0126 | 0.0441 |
| hsa-miR-3676-5p | 2912.88 | 3019.95 | 3453.19 | 3181.99 | 0.3046 | 0.0076 | 0.0328 |
| hsa-miR-423-3p | 15.79 | 19.47 | 17.74 | 20.02 | 0.2829 | 0.0146 | 0.0489 |
| hsa-miR-4257 | 267.62 | 316.63 | 302.40 | 318.08 | 0.3193 | 0.0053 | 0.0277 |
| hsa-miR-4311 | 2.99 | 2.06 | 2.22 | 2.21 | −0.3104 | 0.0067 | 0.0304 |
| hsa-miR-4313 | 22.87 | 27.84 | 26.76 | 28.83 | 0.2910 | 0.0113 | 0.0403 |
| hsa-miR-4322 | 88.99 | 88.90 | 97.53 | 88.46 | 0.2852 | 0.0130 | 0.0451 |
| hsa-miR-43272 | 201.55 | 202.77 | 223.68 | 198.38 | 0.3095 | 0.0057 | 0.0280 |
| hsa-miR-4450 | 4.15 | 3.17 | 3.43 | 3.49 | −0.3095 | 0.0065 | 0.0301 |
| hsa-miR-44702 | 31.28 | 37.96 | 34.27 | 37.99 | 0.2977 | 0.0098 | 0.0370 |
| hsa-miR-4487 | 94.43 | 106.26 | 101.39 | 103.66 | 0.3258 | 0.0049 | 0.0263 |
| hsa-miR-4515 | 280.18 | 336.05 | 308.11 | 333.67 | 0.3322 | 0.0041 | 0.0240 |
| hsa-miR-4665-3p2 | 87.69 | 110.91 | 102.16 | 113.04 | 0.3050 | 0.0094 | 0.0364 |
| hsa-miR-46732 | 66.94 | 81.77 | 74.74 | 81.75 | 0.3028 | 0.0098 | 0.0370 |
| hsa-miR-4676-5p | 2.51 | 1.80 | 1.60 | 2.05 | −0.3245 | 0.0045 | 0.0247 |
| hsa-miR-4695-5p | 299.23 | 347.39 | 324.06 | 341.22 | 0.2873 | 0.0131 | 0.0452 |
| hsa-miR-4746-3p | 370.75 | 429.01 | 409.40 | 428.00 | 0.3224 | 0.0055 | 0.0280 |
| hsa-miR-5006-5p | 544.48 | 647.79 | 581.01 | 634.52 | 0.2835 | 0.0132 | 0.0452 |
| hsa-miR-5189 | 26.37 | 28.82 | 28.72 | 28.62 | 0.2977 | 0.0091 | 0.0354 |
| hsa-miR-548q2 | 50.06 | 69.60 | 57.11 | 67.71 | 0.3043 | 0.0071 | 0.0320 |
| hsa-miR-550b-2-5p2 | 26.33 | 30.43 | 28.98 | 30.15 | 0.2897 | 0.0119 | 0.0419 |
| hsa-miR-60742 | 14.42 | 14.68 | 15.16 | 14.07 | 0.3116 | 0.0085 | 0.0344 |
| hsa-miR-6134 | 3.12 | 2.73 | 2.89 | 3.19 | −0.3222 | 0.0056 | 0.0280 |
| hsa-miR-61652 | 299.51 | 275.50 | 331.99 | 272.61 | 0.3083 | 0.0079 | 0.0331 |
| hsa-miR-642a-3p | 3129.76 | 3671.40 | 3499.61 | 3525.75 | 0.2994 | 0.0087 | 0.0344 |
| hsa-miR-6510-5p | 237.90 | 255.86 | 271.61 | 250.33 | 0.2993 | 0.0099 | 0.0370 |
| hsa-miR-6511b-5p | 50.18 | 53.48 | 55.37 | 53.09 | 0.2901 | 0.0141 | 0.0474 |
| hsa-miR-652-5p | 64.67 | 72.15 | 69.38 | 69.04 | 0.3105 | 0.0059 | 0.0285 |
| hsa-miR-934 | 5.21 | 0.70 | 4.43 | 0.86 | −0.2899 | 0.0111 | 0.0398 |
| hsa-miR-936 | 44.86 | 48.55 | 48.41 | 48.26 | 0.3020 | 0.0075 | 0.0328 |
| hsa-miR-939-5p2 | 467.20 | 552.48 | 529.55 | 547.50 | 0.3040 | 0.0079 | 0.0331 |
Adjusted for age at diagnosis, study center, and sex.
These miRNAs have been previously associated with differential expression and survival
Table 3.
MiRNAs differentially expressed between carcinoma tissue and normal rectal mucosa and associated with only C/F/N smoking.
| Never | Former | Current | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Mean miRNA Expression | Mean miRNA Expression | Mean miRNA Expression | P-values | |||||||
| miRNA | Carcinoma Tissue |
Normal Mucosa |
Carcinoma Tissue |
Normal Mucosa |
Beta1 | Carcinoma Tissue |
Normal Mucosa |
Beta1 | Raw | FDR |
| hsa-miR-141-3p | 33.88 | 22.13 | 29.52 | 23.59 | −0.2704 | 32.73 | 24.52 | −0.2624 | 0.0084 | 0.0438 |
| hsa-miR-16-5p | 77.93 | 58.03 | 67.77 | 55.89 | −0.2250 | 65.75 | 58.32 | −0.3325 | 0.0079 | 0.0427 |
| hsa-miR-17-5p2 | 58.74 | 12.85 | 49.85 | 13.12 | −0.1944 | 47.11 | 13.85 | −0.3429 | 0.0098 | 0.0461 |
| hsa-miR-200a-3p | 25.70 | 17.69 | 21.28 | 18.25 | −0.3084 | 23.06 | 19.24 | −0.3464 | 0.0017 | 0.0271 |
| hsa-miR-21-5p | 404.36 | 117.53 | 360.56 | 120.50 | −0.2770 | 374.43 | 128.14 | −0.3106 | 0.0049 | 0.0383 |
| hsa-miR-29a-3p2 | 103.95 | 39.54 | 87.04 | 39.29 | −0.2676 | 90.14 | 40.54 | −0.3469 | 0.0019 | 0.0271 |
| hsa-miR-29b-3p | 20.28 | 6.72 | 17.14 | 7.26 | −0.3570 | 17.01 | 7.09 | −0.3591 | <.0001 | 0.0256 |
| hsa-miR-30b-5p | 21.97 | 20.00 | 18.53 | 19.26 | −0.1801 | 21.11 | 20.73 | −0.3485 | 0.0107 | 0.0484 |
| hsa-miR-3150b-5p2 | 11.39 | 16.30 | 12.30 | 15.89 | 0.2478 | 14.18 | 15.96 | 0.3330 | 0.0069 | 0.0411 |
| hsa-miR-3620-3p | 7.04 | 8.66 | 7.35 | 8.06 | 0.3440 | 7.52 | 7.90 | 0.2400 | 0.0016 | 0.0271 |
| hsa-miR-425-5p2 | 11.85 | 5.52 | 9.95 | 5.80 | −0.3016 | 10.45 | 5.92 | −0.2500 | 0.0054 | 0.0394 |
| hsa-miR-4485 | 1074.42 | 1298.17 | 1012.29 | 1335.83 | −0.2928 | 1127.54 | 1347.92 | 0.0495 | 0.0043 | 0.0362 |
| hsa-miR-509-3-5p | 5.58 | 6.67 | 5.96 | 6.40 | 0.2902 | 6.00 | 6.36 | 0.2117 | 0.0099 | 0.0463 |
| hsa-miR-60842 | 13.00 | 14.82 | 14.26 | 15.10 | 0.2296 | 15.58 | 14.63 | 0.3358 | 0.0069 | 0.0411 |
Adjusted for age at diagnosis, study center, and sex.
These miRNAs have been previously associated with differential expression and survival.
Table 4.
MiRNAs differentially expressed between carcinoma tissue and normal rectal mucosa and associated with only pack-years smoked.
| Mean miRNA Expression | P-values | ||||
|---|---|---|---|---|---|
| miRNA | Carcinoma Tissue | Normal Mucosa | Beta1 | Raw | FDR |
| hsa-miR-1273g-5p | 8.35 | 8.60 | −0.0418 | 0.0130 | 0.0491 |
| hsa-miR-127-3p | 2.27 | 0.85 | −0.0744 | 0.0080 | 0.0386 |
| hsa-miR-1290 | 147.04 | 117.28 | 0.0578 | 0.0029 | 0.0269 |
| hsa-miR-139-3p2 | 7.94 | 10.64 | 0.1110 | 0.0124 | 0.0475 |
| hsa-miR-146b-5p | 3.35 | 1.27 | −0.1280 | 0.0041 | 0.0299 |
| hsa-miR-192-3p | 1.98 | 2.54 | −0.1243 | 0.0054 | 0.0351 |
| hsa-miR-196a-5p2 | 6.29 | 2.68 | −0.1548 | 0.0004 | 0.0240 |
| hsa-miR-203a | 12.40 | 3.42 | −0.1715 | 0.0002 | 0.0240 |
| hsa-miR-2277-3p | 3.99 | 4.62 | 0.0277 | 0.0004 | 0.0240 |
| hsa-miR-28-5p | 1.36 | 1.69 | −0.0737 | 0.0061 | 0.0363 |
| hsa-miR-3147 | 31.02 | 29.77 | 0.1183 | 0.0082 | 0.0388 |
| hsa-miR-320b | 76.00 | 75.48 | 0.0998 | 0.0087 | 0.0397 |
| hsa-miR-320d | 41.27 | 41.01 | 0.0944 | 0.0090 | 0.0406 |
| hsa-miR-330-3p | 3.27 | 5.68 | −0.1205 | 0.0060 | 0.0359 |
| hsa-miR-339-3p | 3.41 | 3.16 | −0.1126 | 0.0103 | 0.0429 |
| hsa-miR-3648 | 302.77 | 265.50 | 0.1188 | 0.0073 | 0.0381 |
| hsa-miR-3667-5p2 | 19.58 | 22.73 | 0.1104 | 0.0133 | 0.0495 |
| hsa-miR-3677-3p | 4.49 | 2.39 | −0.1125 | 0.0116 | 0.0463 |
| hsa-miR-3911 | 84.61 | 75.53 | 0.1290 | 0.0034 | 0.0269 |
| hsa-miR-3934-5p | 41.73 | 42.63 | 0.1307 | 0.0033 | 0.0269 |
| hsa-miR-425-3p2 | 12.37 | 15.09 | 0.0846 | 0.0090 | 0.0406 |
| hsa-miR-4259 | 17.67 | 15.88 | 0.0795 | 0.0036 | 0.0273 |
| hsa-miR-4292 | 11.43 | 5.11 | −0.1131 | 0.0098 | 0.0425 |
| hsa-miR-42982 | 164.14 | 149.05 | 0.1330 | 0.0036 | 0.0273 |
| hsa-miR-4419a | 62.35 | 59.78 | 0.1238 | 0.0049 | 0.0342 |
| hsa-miR-4419b | 23.99 | 25.29 | 0.1165 | 0.0074 | 0.0381 |
| hsa-miR-4421 | 1.62 | 1.90 | −0.1106 | 0.0122 | 0.0475 |
| hsa-miR-44292 | 21.85 | 22.49 | 0.1257 | 0.0048 | 0.0341 |
| hsa-miR-4436b-3p | 7.98 | 6.42 | −0.1067 | 0.0126 | 0.0478 |
| hsa-miR-44812 | 64.90 | 69.70 | 0.1377 | 0.0022 | 0.0266 |
| hsa-miR-4513 | 25.75 | 25.91 | 0.1300 | 0.0034 | 0.0269 |
| hsa-miR-4640-5p | 27.75 | 25.32 | 0.1151 | 0.0097 | 0.0425 |
| hsa-miR-4667-5p | 56.42 | 56.33 | 0.1110 | 0.0106 | 0.0437 |
| hsa-miR-4685-5p2 | 19.37 | 20.14 | 0.1089 | 0.0124 | 0.0475 |
| hsa-miR-4698 | 33.40 | 34.05 | 0.1324 | 0.0031 | 0.0269 |
| hsa-miR-4710 | 36.12 | 34.94 | 0.1188 | 0.0074 | 0.0381 |
| hsa-miR-4743-5p | 54.09 | 53.32 | 0.1098 | 0.0126 | 0.0478 |
| hsa-miR-4758-5p | 106.67 | 105.94 | 0.1197 | 0.0075 | 0.0381 |
| hsa-miR-4778-5p | 68.39 | 52.84 | 0.1307 | 0.0034 | 0.0269 |
| hsa-miR-4783-3p2 | 11.39 | 13.57 | 0.1374 | 0.0024 | 0.0266 |
| hsa-miR-4800-5p | 181.69 | 154.52 | 0.1448 | 0.0014 | 0.0240 |
| hsa-miR-483-5p | 102.04 | 92.12 | 0.1398 | 0.0017 | 0.0246 |
| hsa-miR-487b | 1.78 | 2.05 | −0.1290 | 0.0031 | 0.0269 |
| hsa-miR-508-5p2 | 2.99 | 3.42 | 0.0278 | 0.0062 | 0.0363 |
| hsa-miR-514b-5p | 29.50 | 28.13 | 0.1212 | 0.0060 | 0.0359 |
| hsa-miR-5187-5p | 1.95 | 2.19 | −0.1196 | 0.0074 | 0.0381 |
| hsa-miR-5190 | 26.14 | 26.81 | 0.1147 | 0.0087 | 0.0397 |
| hsa-miR-532-3p | 2.56 | 1.34 | −0.1185 | 0.0079 | 0.0386 |
| hsa-miR-5585-3p | 308.27 | 307.70 | 0.1290 | 0.0046 | 0.0333 |
| hsa-miR-5585-5p | 5.18 | 5.83 | −0.1261 | 0.0051 | 0.0343 |
| hsa-miR-616-3p | 1.22 | 0.77 | −0.0628 | 0.0021 | 0.0266 |
| hsa-miR-659-5p | 1.73 | 2.59 | −0.1311 | 0.0031 | 0.0269 |
| hsa-miR-6716-3p | 4.90 | 4.75 | −0.0409 | 0.0053 | 0.0350 |
| hsa-miR-6716-5p | 3.80 | 3.73 | 0.0838 | 0.0009 | 0.0240 |
| hsa-miR-758-5p | 27.84 | 29.46 | −0.0508 | 0.0103 | 0.0429 |
| hsa-miR-766-3p | 22.63 | 27.90 | 0.0713 | 0.0070 | 0.0381 |
| hsa-miR-93-5p2 | 35.97 | 12.16 | −0.0681 | 0.0076 | 0.0383 |
Adjusted for age at diagnosis, study center, and sex.
These miRNAs have been previously associated with differential expression and survival.
One hundred and eleven miRNAs were associated with all three smoking variables (Table 5). Of these, 110 the same direction of association for every variable; one miRNA, hsa-miR-432-5p, had a positive change from never to former but negative changes in current smoking, never to current smoking, and pack-years smoked. Of the 110 with the same direction of association, 11 were downregulated with current smoking, never to former as well as never to current smoking, and with pack-years smoked; 99 miRNAs were upregulated with these variables.
Table 5.
MiRNAs associated with current smoking, C/F/N smoking and pack-years smoked.
| Beta1 | ||||
|---|---|---|---|---|
| miRNA | Current Smoking | Never vs. Former | Never vs. Current | Pack-Years |
| hsa-miR-106b-5p2 | −0.3240 | −0.2585 | −0.4337 | −0.1597 |
| hsa-miR-1185-1-3p | 0.3492 | 0.0624 | 0.3756 | 0.1237 |
| hsa-miR-1185-2-3p | 0.3925 | 0.0841 | 0.4282 | 0.1450 |
| hsa-miR-12021 | 0.4067 | 0.0485 | 0.4273 | 0.1481 |
| hsa-miR-1207-5p2 | 0.3785 | 0.1107 | 0.4255 | 0.1361 |
| hsa-miR-1225-5p2 | 0.3685 | 0.0829 | 0.4037 | 0.1424 |
| hsa-miR-1226-5p2 | 0.3854 | 0.1882 | 0.4652 | 0.1525 |
| hsa-miR-1227-5p2 | 0.3413 | 0.1035 | 0.3852 | 0.1160 |
| hsa-miR-1229-3p | 0.4794 | 0.1478 | 0.5421 | 0.1095 |
| hsa-miR-1229-5p2 | 0.3419 | 0.1298 | 0.3970 | 0.1410 |
| hsa-miR-1234-5p2 | 0.3967 | 0.0929 | 0.4361 | 0.1395 |
| hsa-miR-125a-3p | 0.3628 | 0.1325 | 0.4191 | 0.1470 |
| hsa-miR-130b-3p | −0.3470 | −0.1079 | −0.3928 | −0.1344 |
| hsa-miR-1342 | 0.3889 | 0.1307 | 0.4444 | 0.1423 |
| hsa-miR-138-2-3p | −0.3258 | −0.1233 | −0.3782 | −0.1187 |
| hsa-miR-1469 | 0.3908 | 0.1560 | 0.4570 | 0.1196 |
| hsa-miR-149-3p2 | 0.3351 | 0.1743 | 0.4090 | 0.1181 |
| hsa-miR-150-3p2 | 0.3640 | 0.0670 | 0.3924 | 0.1352 |
| hsa-miR-1587 | 0.3449 | 0.0882 | 0.3823 | 0.1173 |
| hsa-miR-188-5p | 0.3828 | 0.2098 | 0.4718 | 0.1620 |
| hsa-miR-19b-3p2 | −0.2856 | −0.2561 | −0.3942 | −0.1222 |
| hsa-miR-20b-5p2 | −0.3292 | −0.2362 | −0.4294 | −0.1305 |
| hsa-miR-3121-3p | −0.3705 | −0.0328 | −0.3844 | −0.1219 |
| hsa-miR-31382 | 0.2932 | 0.1901 | 0.3738 | 0.1380 |
| hsa-miR-3162-5p | 0.3507 | 0.1443 | 0.4119 | 0.1340 |
| hsa-miR-31852 | 0.3578 | 0.1743 | 0.4318 | 0.1343 |
| hsa-miR-3187-3p2 | 0.3029 | 0.1543 | 0.3683 | 0.1225 |
| hsa-miR-31882 | 0.3751 | 0.1140 | 0.4235 | 0.1320 |
| hsa-miR-33b-3p2 | 0.3843 | 0.1037 | 0.4283 | 0.1408 |
| hsa-miR-345-3p2 | 0.3234 | 0.1109 | 0.3705 | 0.1488 |
| hsa-miR-36212 | 0.2991 | 0.1617 | 0.3678 | 0.1051 |
| hsa-miR-3651 | −0.2860 | −0.2557 | −0.3945 | −0.1114 |
| hsa-miR-3656 | 0.3801 | 0.1196 | 0.4309 | 0.1216 |
| hsa-miR-3663-3p2 | 0.4170 | 0.1177 | 0.4670 | 0.1433 |
| hsa-miR-36652 | 0.3961 | 0.1056 | 0.4409 | 0.1316 |
| hsa-miR-3679-5p2 | 0.3396 | 0.0987 | 0.3815 | 0.1300 |
| hsa-miR-373-5p | 0.3683 | 0.0888 | 0.4060 | 0.1120 |
| hsa-miR-39372 | 0.3675 | 0.1251 | 0.4205 | 0.1290 |
| hsa-miR-3940-5p2 | 0.3637 | 0.0924 | 0.4029 | 0.1223 |
| hsa-miR-39452 | 0.3190 | 0.1568 | 0.3855 | 0.1159 |
| hsa-miR-39602 | 0.3710 | 0.1280 | 0.4254 | 0.1444 |
| hsa-miR-42702 | 0.4566 | 0.1074 | 0.5022 | 0.1746 |
| hsa-miR-4271 | 0.3615 | 0.1231 | 0.4138 | 0.1388 |
| hsa-miR-42812 | 0.4036 | 0.0565 | 0.4275 | 0.1452 |
| hsa-miR-4304 | 0.3229 | 0.1970 | 0.4065 | 0.1571 |
| hsa-miR-432-5p2 | −0.3634 | 0.1652 | −0.2933 | −0.0580 |
| hsa-miR-4433-3p2 | 0.3621 | 0.1150 | 0.4109 | 0.1420 |
| hsa-miR-4442 | 0.3462 | 0.0744 | 0.3777 | 0.1404 |
| hsa-miR-44432 | 0.3592 | 0.0282 | 0.3711 | 0.1311 |
| hsa-miR-44592 | 0.3270 | 0.1111 | 0.3741 | 0.1133 |
| hsa-miR-44632 | 0.3475 | 0.0852 | 0.3836 | 0.1497 |
| hsa-miR-44662 | 0.4036 | 0.1375 | 0.4619 | 0.1422 |
| hsa-miR-4476 | 0.3621 | 0.1176 | 0.4121 | 0.1313 |
| hsa-miR-4484 | 0.3822 | 0.0646 | 0.4096 | 0.1357 |
| hsa-miR-4496 | 0.3775 | 0.1499 | 0.4411 | 0.1602 |
| hsa-miR-44992 | 0.3372 | 0.1257 | 0.3905 | 0.1393 |
| hsa-miR-45082 | 0.3430 | 0.1441 | 0.4041 | 0.1302 |
| hsa-miR-45162 | 0.4308 | 0.1052 | 0.4754 | 0.1434 |
| hsa-miR-4530 | 0.3611 | 0.0590 | 0.3861 | 0.1180 |
| hsa-miR-45342 | 0.3288 | 0.1076 | 0.3744 | 0.1416 |
| hsa-miR-4535 | 0.3563 | 0.1111 | 0.4035 | 0.1234 |
| hsa-miR-4538 | 0.3610 | 0.0744 | 0.3926 | 0.1160 |
| hsa-miR-4539 | 0.5240 | 0.2030 | 0.6101 | 0.1816 |
| hsa-miR-46342 | 0.3583 | 0.1556 | 0.4243 | 0.1526 |
| hsa-miR-4646-5p | 0.3163 | 0.1306 | 0.3717 | 0.1245 |
| hsa-miR-4651 | 0.3795 | 0.1688 | 0.4511 | 0.1427 |
| hsa-miR-4655-5p2 | 0.3497 | 0.0956 | 0.3902 | 0.1173 |
| hsa-miR-4664-3p2 | 0.3634 | 0.1665 | 0.4340 | 0.1137 |
| hsa-miR-4665-5p2 | 0.3253 | 0.2652 | 0.4378 | 0.1404 |
| hsa-miR-4669 | 0.3472 | 0.1225 | 0.3992 | 0.1116 |
| hsa-miR-4687-3p2 | 0.3893 | 0.0693 | 0.4187 | 0.1363 |
| hsa-miR-4690-5p2 | 0.3449 | 0.0919 | 0.3839 | 0.1307 |
| hsa-miR-4700-5p | −0.3031 | −0.1716 | −0.3759 | −0.1163 |
| hsa-miR-4701-3p | 0.2990 | 0.1822 | 0.3763 | 0.1418 |
| hsa-miR-47342 | 0.3823 | 0.1301 | 0.4376 | 0.1230 |
| hsa-miR-47392 | 0.3876 | 0.0814 | 0.4221 | 0.1334 |
| hsa-miR-4740-5p | 0.3805 | 0.1893 | 0.4608 | 0.1324 |
| hsa-miR-47412 | 0.3299 | 0.1453 | 0.3916 | 0.1415 |
| hsa-miR-4745-5p | 0.3852 | 0.1719 | 0.4582 | 0.1319 |
| hsa-miR-4763-3p | 0.3866 | 0.0937 | 0.4263 | 0.1292 |
| hsa-miR-4767 | 0.3502 | 0.1117 | 0.3975 | 0.1141 |
| hsa-miR-4787-3p | 0.3618 | 0.1469 | 0.4241 | 0.1119 |
| hsa-miR-4787-5p2 | 0.3331 | 0.1020 | 0.3764 | 0.1146 |
| hsa-miR-484 | −0.3872 | −0.0332 | −0.4013 | −0.1189 |
| hsa-miR-4982 | 0.3321 | 0.1042 | 0.3763 | 0.1183 |
| hsa-miR-5001-5p2 | 0.3668 | 0.0957 | 0.4074 | 0.1214 |
| hsa-miR-500a-3p | −0.3082 | −0.1597 | −0.3760 | −0.1226 |
| hsa-miR-5195-3p2 | 0.3657 | 0.0876 | 0.4029 | 0.1438 |
| hsa-miR-550a-3-5p2 | 0.3391 | 0.0485 | 0.3597 | 0.1250 |
| hsa-miR-557 | 0.3773 | 0.1589 | 0.4447 | 0.1435 |
| hsa-miR-5722 | 0.3640 | 0.0900 | 0.4022 | 0.1293 |
| hsa-miR-5787 | 0.2933 | 0.1829 | 0.3709 | 0.1195 |
| hsa-miR-6012 | 0.3915 | 0.1433 | 0.4523 | 0.1451 |
| hsa-miR-60682 | 0.3695 | 0.1019 | 0.4128 | 0.1225 |
| hsa-miR-6076 | 0.3567 | 0.0598 | 0.3821 | 0.1212 |
| hsa-miR-60862 | 0.3344 | 0.1146 | 0.3831 | 0.1256 |
| hsa-miR-60872 | 0.4023 | 0.0505 | 0.4238 | 0.1354 |
| hsa-miR-60882 | 0.3818 | 0.0590 | 0.4068 | 0.1370 |
| hsa-miR-60892 | 0.3912 | 0.1205 | 0.4423 | 0.1331 |
| hsa-miR-60902 | 0.4363 | 0.1023 | 0.4797 | 0.1529 |
| hsa-miR-61242 | 0.3394 | 0.0816 | 0.3740 | 0.1457 |
| hsa-miR-61252 | 0.3672 | 0.1027 | 0.4107 | 0.1214 |
| hsa-miR-61262 | 0.3887 | 0.1204 | 0.4398 | 0.1268 |
| hsa-miR-617 | 0.3833 | 0.1717 | 0.4562 | 0.1249 |
| hsa-miR-6382 | 0.3835 | 0.1030 | 0.4272 | 0.1300 |
| hsa-miR-6722-3p2 | 0.3570 | 0.1116 | 0.4044 | 0.1481 |
| hsa-miR-6723-5p | 0.3597 | 0.0792 | 0.3933 | 0.1418 |
| hsa-miR-6724-5p2 | 0.3419 | 0.0944 | 0.3820 | 0.1313 |
| hsa-miR-770-5p | −0.3457 | −0.0423 | −0.3637 | −0.1213 |
| hsa-miR-877-5p2 | 0.3441 | 0.1394 | 0.4032 | 0.1504 |
| hsa-miR-8872 | 0.3314 | 0.1118 | 0.3788 | 0.1162 |
Adjusted for age at diagnosis, study center, and sex.
These miRNAs have been previously associated with differential expression and survival.
Associations between the miRNAs associated with cigarette smoking the tumor molecular phenotype are summarized in Table 6 (Supplemental Table 1 has complete data for rectal cancer and Supplemental Table 2 has complete data for colon cancer). Differential expression of 39 miRNAs was directly associated, and of five miRNAs was inversely associated, with CIMP Low/MSI tumors in both colon and rectal cancer subjects (Table 6), however the magnitude of the associations, although less precise for rectal cancer, were much stronger. Nine miRNAs in rectal subjects and 11 in colon had differential expression that was inversely associated with CIMP Low/MSI, while 28 miRNAs in rectal and 79 in colon cancer subjects were differentially expressed in a direct relationship to CIMP Low/MSI. Few miRNAs associated with smoking were significantly associated with a CIMP High/MSS tumor. The strongest associations with the most miRNAs associated with cigarette smoking were observed when the tumor phenotype was CIMP High/MSI. Current smoking versus never smoked was significantly associated with CIMP High/MSI, OR = 2.42, 95% CI 1.16 – 5.03. Twelve miRNAs were differentially expressed in an inverse manner with CIMP High/MSI in both colon and rectal cancer cases, and 135 were differentially expressed in a direct manner for both tumor sites. Additionally, five miRNAs were inversely associated with CIMP High/MSI rectal tumors and of 54 miRNAs were directly associated with CIMP High/MSI rectal tumors
Table 6.
MicroRNAs that are significantly differentially expressed with cigarette smoking and are associated with CIMP and/or MSI status in colon and rectal cancer subjects with an FDR < 0.05.
| CIMP Low / MSI | CIMP High / MSS | CIMP High / MSI | |
|---|---|---|---|
| Colon and Rectal Tissue | |||
|
Directly Associated miRNAs |
hsa-miR-320c, hsa-miR-1207-5p,
hsa-miR- 1225-5p, hsa-miR-1229-3p, hsa-miR-1234-5p, hsa-miR-125a-3p, hsa-miR-134, hsa-miR-135a- 3p, hsa-miR-188-5p, hsa-miR-1914-3p, hsa- miR-3610, hsa-miR-3917, hsa-miR-3945, hsa- miR-3960, hsa-miR-4270, hsa-miR-4459, hsa- miR-4470, hsa-miR-4499, hsa-miR-4508, hsa- miR-4516, hsa-miR-4530, hsa-miR-4532, hsa- miR-4673, hsa-miR-4739, hsa-miR-4745-5p, hsa-miR-5006-5p, hsa-miR-5088, hsa-miR- 520b, hsa-miR-575, hsa-miR-5787, hsa-miR- 6086, hsa-miR-6090, hsa-miR-6126, hsa-miR- 617, hsa-miR-718, hsa-miR-762, hsa-miR-1469, hsa-miR-3676-5p, hsa-miR-877-5p |
hsa-miR-3622a-5p | hsa-miR-1202, hsa-miR-1226-5p,
hsa-miR- 1307-5p, hsa-miR-149-3p, hsa-miR-150-3p, hsa-miR-3150b-5p, hsa-miR-3646, hsa-miR- 3652, hsa-miR-3666, hsa-miR-3667-5p, hsa- miR-371a-5p, hsa-miR-423-3p, hsa-miR-4253, hsa-miR-4463, hsa-miR-4476, hsa-miR-4515, hsa-miR-4655-5p, hsa-miR-4664-3p, hsa-miR- 4665-3p, hsa-miR-4665-5p, hsa-miR-4783-3p, hsa-miR-4787-3p, hsa-miR-550b-2-5p, hsa- miR-601, hsa-miR-623, hsa-miR-6723-5p, hsa- miR-6724-5p, hsa-miR-887, hsa-miR-940, hsa- miR-99b-3p, hsa-miR-5189, hsa-miR-1185-1- 3p, hsa-miR-1185-2-3p, hsa-miR-1207-5p, hsa-miR-1225-5p, hsa-miR-1227-5p, hsa-miR- 1229-3p, hsa-miR-1229-5p, hsa-miR-1233-1- 5p, hsa-miR-1234-5p, hsa-miR-125a-3p, hsa- miR-1275, hsa-miR-129-5p, hsa-miR-134, hsa- miR-135a-3p, hsa-miR-1587, hsa-miR-188-5p, hsa-miR-1914-3p, hsa-miR-1915-3p, hsa-miR- 197-5p, hsa-miR-2861, hsa-miR-3162-5p, hsa- miR-3187-3p, hsa-miR-3188, hsa-miR-3610, hsa-miR-3620-5p, hsa-miR-3665, hsa-miR- 3679-5p, hsa-miR-3917, hsa-miR-3937, hsa- miR-3940-5p, hsa-miR-3945, hsa-miR-4257, hsa-miR-4270, hsa-miR-4271, hsa-miR-4281, hsa-miR-4419b, hsa-miR-4429, hsa-miR-4459, hsa-miR-4466, hsa-miR-4470, hsa-miR-4499, hsa-miR-4505, hsa-miR-4507, hsa-miR-4508, hsa-miR-4516, hsa-miR-4530, hsa-miR-4532, hsa-miR-4535, hsa-miR-4538, hsa-miR-4651, hsa-miR-4669, hsa-miR-4672, hsa-miR-4673, hsa-miR-4687-3p, hsa-miR-4690-5p, hsa-miR- 4721, hsa-miR-4739, hsa-miR-4740-5p, hsa- miR-4745-5p, hsa-miR-4746-3p, hsa-miR- 4763-3p, hsa-miR-4787-5p, hsa-miR-5001-5p, hsa-miR-5006-5p, hsa-miR-5088, hsa-miR- 5195-3p, hsa-miR-520b, hsa-miR-548q, hsa- miR-557, hsa-miR-572, hsa-miR-575, hsa-miR- 5787, hsa-miR-6068, hsa-miR-6076, hsa-miR- 6084, hsa-miR-6086, hsa-miR-6087, hsa-miR- 6088, hsa-miR-6089, hsa-miR-6090, hsa-miR- 6125, hsa-miR-6126, hsa-miR-6127, hsa-miR- 617, hsa-miR-638, hsa-miR-671-5p, hsa-miR- 6722-3p, hsa-miR-718, hsa-miR-762, hsa-miR- 874, hsa-miR-937-5p, hsa-miR-939-5p, hsa- miR-1208, hsa-miR-1224-5p, hsa-miR-1469, hsa-miR-3621, hsa-miR-3622a-5p, hsa-miR- 373-5p, hsa-miR-4486, hsa-miR-4497, hsa- miR-4695-5p, hsa-miR-4734, hsa-miR-769-3p, hsa-miR-877-5p |
|
Inversely Associated miRNAs |
hsa-miR-196a-5p, hsa-miR-196b-5p,
hsa-miR- 20b-5p, hsa-miR-215, hsa-miR-30b-5p |
hsa-miR-196b-5p | hsa-miR-196b-5p, hsa-miR-127-3p,
hsa-miR- 19b-3p, hsa-miR-20a-5p, hsa-miR-20b-5p, hsa-miR-215, hsa-miR-29a-3p, hsa-miR-29b- 3p, hsa-miR-30b-5p, hsa-miR-425-5p, hsa- miR-501-3p, hsa-miR-93-5p |
| Rectal Tissue Only | |||
|
Directly Associated miRNAs |
hsa-miR-3663-3p, hsa-miR-4534,
hsa-miR- 4634, hsa-miR-1202, hsa-miR-1225-3p, hsa- miR-1226-5p, hsa-miR-1307-5p, hsa-miR-139- 3p, hsa-miR-3150b-5p, hsa-miR-345-5p, hsa- miR-3646, hsa-miR-3652, hsa-miR-3667-5p, hsa-miR-4253, hsa-miR-4476, hsa-miR-4664- 3p, hsa-miR-4665-3p, hsa-miR-4689, hsa-miR- 4767, hsa-miR-4783-3p, hsa-miR-5190, hsa- miR-601, hsa-miR-6085, hsa-miR-6510-5p, hsa- miR-6723-5p, hsa-miR-877-3p, hsa-miR-887, hsa-miR-940 |
hsa-miR-4721, hsa-miR-4470 | hsa-miR-1183, hsa-miR-1236-5p,
hsa-miR- 1249, hsa-miR-2392, hsa-miR-3138, hsa-miR- 3156-5p, hsa-miR-3158-5p, hsa-miR-3185, hsa-miR-3194-5p, hsa-miR-320a, hsa-miR- 320b, hsa-miR-33b-3p, hsa-miR-345-3p, hsa- miR-3648, hsa-miR-3656, hsa-miR-3934-5p, hsa-miR-423-5p, hsa-miR-4259, hsa-miR- 4304, hsa-miR-4322, hsa-miR-4327, hsa-miR- 4417, hsa-miR-4433-3p, hsa-miR-4433-5p, hsa-miR-4442, hsa-miR-4484, hsa-miR-4487, hsa-miR-4488, hsa-miR-4646-5p, hsa-miR- 4685-5p, hsa-miR-4707-5p, hsa-miR-4726-5p, hsa-miR-4741, hsa-miR-4743-5p, hsa-miR- 4758-5p, hsa-miR-4788, hsa-miR-4793-5p, hsa-miR-498, hsa-miR-5196-5p, hsa-miR- 550a-3-5p, hsa-miR-602, hsa-miR-642b-3p, hsa-miR-6511b-5p, hsa-miR-652-5p, hsa-miR- 936, hsa-miR-1225-3p, hsa-miR-139-3p, hsa- miR-345-5p, hsa-miR-4689, hsa-miR-4767, hsa-miR-5190, hsa-miR-6085, hsa-miR-6510- 5p, hsa-miR-877-3p |
|
Inversely Associated miRNAs |
hsa-miR-106b-5p, hsa-miR-140-3p,
hsa-miR- 425-5p, hsa-miR-501-3p, hsa-miR-126-3p, hsa- miR-200a-3p, hsa-miR-203a, hsa-miR-429, hsa- miR-4709-3p |
hsa-miR-1273g-5p,
hsa-miR- 130b-3p |
hsa-miR-141-3p, hsa-miR-106b-5p,
hsa-miR- 140-3p, hsa-miR-15b-5p, hsa-miR-3174 |
| Colon Tissue Only | |||
|
Directly Associated miRNAs |
hsa-miR-5001-5p, hsa-miR-5195-3p,
hsa-miR- 548q, hsa-miR-557, hsa-miR-572, hsa-miR- 6068, hsa-miR-6076, hsa-miR-6084, hsa-miR- 6087, hsa-miR-6088, hsa-miR-6089, hsa-miR- 6125, hsa-miR-6127, hsa-miR-638, hsa-miR- 671-5p, hsa-miR-6722-3p, hsa-miR-874, hsa- miR-937-5p, hsa-miR-939-5p, hsa-miR-1208, hsa-miR-1224-5p, hsa-miR-330-3p, hsa-miR- 3621, hsa-miR-3622a-5p, hsa-miR-373-5p, hsa- miR-4486, hsa-miR-4497, hsa-miR-4695-5p, hsa-miR-4734, hsa-miR-769-3p |
hsa-miR-509-3-5p, hsa-miR- 5189, hsa-miR-1208, hsa-miR- 1224-5p, hsa-miR-1469, hsa- miR-330-3p, hsa-miR-3621, hsa-miR-3676-5p, hsa-miR- 373-5p, hsa-miR-4486, hsa- miR-4497, hsa-miR-4695-5p, hsa-miR-4734, hsa-miR-769- 3p, hsa-miR-877-5p |
hsa-miR-3663-3p, hsa-miR-4481,
hsa-miR- 4534, hsa-miR-4634, hsa-miR-3960, hsa-miR- 330-3p, hsa-miR-3676-5p |
|
Inversely Associated miRNAs |
hsa-miR-17-5p, hsa-miR-19b-3p,
hsa-miR-20a-5p, hsa-miR-29b-3p, hsa-miR-3651, hsa-miR-4485, hsa-miR-199b-5p, hsa-miR-29a-3p, hsa-miR-758- 5p, hsa-miR-3174, hsa-miR-6716-3p |
hsa-miR-17-5p, hsa-miR-196a- 5p, hsa-miR-19b-3p, hsa-miR- 20a-5p, hsa-miR-20b-5p, hsa- miR-215, hsa-miR-29b-3p, hsa-miR-3651, hsa-miR-4485, hsa-miR-200a-3p, hsa-miR- 425-5p, hsa-miR-429, hsa- miR-532-3p, hsa-miR-192-3p, hsa-miR-28-5p, hsa-miR-484 |
hsa-miR-17-5p, hsa-miR-4485,
hsa-miR-200a- 3p, hsa-miR-196a-5p, hsa-miR-3651, hsa-miR- 199b-5p, hsa-miR-758-5p, hsa-miR-429, hsa- miR-532-3p, hsa-miR-107, hsa-miR-3121-3p, hsa-miR-3135b, hsa-miR-4313, hsa-miR- 4436b-3p, hsa-miR-4800-5p |
4. Discussion
In this study, we investigated whether cigarette smoking influences miRNA expression in CRC subjects. Two hundred and thirty-one miRNAs were associated with current smoking, 172 with C/F/N smoking, and 206 with pack-years smoked. One hundred and ninety-two miRNAs were associated with two or more smoking criteria, while 111 were associated with all three variables and 114 were unique to only one. Together, these results suggest that a lifestyle factor, such as cigarette smoking, is indeed able to alter endogenous levels of miRNAs in rectal cancer subjects. Additionally, while some miRNAs are altered with smoking in general, different amounts and type of exposure also results in different dysregulated miRNAs.
Previously, we identified miRNAs whose differential expression between carcinoma tissue and normal colorectal mucosa were associated significantly with survival after being diagnosed with rectal cancer (20). In that study, hazard ratios and 95% confidence intervals were adjusted for age, sex, AJCC stage, and MSI tumor status. Of the 43 miRNAs associated with only current smoking, differential expression of 11 miRNAs had previously been identified with altered survival after diagnosis with rectal cancer. One of these miRNAs (hsa-miR-196b-5p) had improved survival in rectal cases when this miRNA was upregulated in rectal carcinoma tissue relative to normal mucosa, and this miRNA had decreased differential (carcinoma minus normal mucosa) expression in current smokers. Ten miRNAs (hsa-miR-1914-3p, hsa-miR-4327, hsa-miR-4470, hsa-miR-4665-3p, hsa-miR-4673, hsa-miR-548q, hsa-miR-550b-2-5p, hsa-miR-6074, hsa-miR-6165, and hsa-miR-939-5p) were upregulated in tumors of rectal cases of current smokers and the differential expression of these miRNAs was previously shown to be associated with worse survival when expression in carcinoma tissue increased. Five of the 14 miRNAs associated significantly with only C/F/N smoking were previously identified as being differentially expressed between carcinoma and normal mucosa and this change in expression was also shown to alter survival of rectal cancer cases. Three of these miRNAs (hsa-miR-17-5p, hsa-miR-29a-3p, and hsa-miR-425-5p) improved survival, and were downregulated in tumors of current and former smokers compared to those who never smoked. Two of the miRNAs (hsa-miR-3150b-5p and hsa-miR-6084) increased risk of death from colorectal cancer in cases diagnosed with rectal cancer when expression increased in carcinoma tissue; both miRNAs had higher expression in carcinoma tissue in both former and current smokers compared to carcinoma tissue of cases who never smoked. Twelve of the fifty-seven of the miRNAs associated with only pack-years smoked were associated with differential expression between carcinoma and normal mucosa and with colorectal cancer survival in cases diagnosed with rectal cancer. Four of these miRNAs (hsa-miR-196a-5p, hsa-miR-429, hsa-miR-508-5p, and hsa-miR-93-5p) reduced the risk of death from colorectal cancer after being diagnosed with rectal cancer when expression increased in carcinoma tissue, and all but one of these (hsa-miR-508-5p) was downregulated in tumors in cases who smoked more pack-years. Eight of the miRNAs (hsa-miR-139-3p, hsa-miR-3667-5p, hsa-miR-425-3p, hsa-miR-4298, hsa-miR-4429, hsa-miR-4481, hsa-miR-4685-5p, and hsa-miR-4783-3p) increased risk of colorectal cancer death among rectal cancer cases with expression increases in carcinoma tissue, and these miRNAs had higher expression in carcinoma tissue with subjects who smoked more pack-years. Of the 111 miRNAs associated with all three smoking variables, 69 were previously identified as being associated with rectal survival. Four miRNAs (hsa-miR-106b-5p, hsa-miR-19b-3p, hsa-miR-20b-5p, and hsa-miR-432-5p) were seen to improve survival and these were generally downregulated in all smoking variables. Of the 69 previously associated with CRC survival in cases diagnosed with rectal cancer, 65 were seen to worsen survival and these were upregulated with every smoking variable. These data suggest that smoking alters miRNA levels in a manner conducive to poorer outcomes.
Current smoking was associated with the largest number of dysregulated miRNAs, with 231 miRNAs whose differential expression was significantly associated with current versus not current smoking; pack-years smoked was associated significantly with 206 miRNAs, and had the highest number of unique miRNAs that were differentially expressed (N=57). These data show that, not only are many miRNAs generally dysregulated with any smoking, there are specific miRNAs that represent current as well as amount and duration (embodied by pack-years smoked) of smoking. Additionally, differential expression of these unique miRNAs has been shown to be associated significantly with altered survival in rectal cancer subjects. These data support the hypothesis that current smoking does indeed influence a larger number of miRNAs, however it also supports the notion that cigarette smoking in a large amount, regardless of contemporariness to diagnosis, is able to influence miRNA expression in a unique manner and possibly alter survival of rectal cancer in a negative manner.
Previously, we identified mRNAs that were differentially expressed in colon tissue of current smokers versus people who never smoked (4). In order to see if miRNAs associated with smoking could be influencing mRNA expression, we found the target genes for the five miRNAs that were unique to C/F/N smoking whose differential expression was previously seen to be associated with rectal cancer survival, as these miRNAs are more likely to be influencing mRNA expression. Three mRNAs from this list were previously shown to be dysregulated in current smokers: FGA (fold change = 28.01), RBM20 (fold change = 2.99), and YY2 (fold change = 3.34) were all upregulated in current smokers (4). Hsa-miR-17-5p is known to regulate RBM20 and hsa-miR-29a-3p is known to regulate FGA and YY2; both of these miRNAs have decreasing expression in carcinoma tissue and increasing expression in normal colonic mucosa in current smokers compared to people who never smoked (BetaC vs. N = −0.3429 for hsa-miR-17-5p; BetaC vs. N = −0.3469 for hsa-miR-29a-3p). This could explain the increased expression of these target genes. Our past study on mRNA used differential expression in colon tissue. However, the miRNAs that are differentially expressed in regards to smoking are differentially expressed in rectal tissue. This may account for incomplete overlapping between target genes of miRNA and our previous report of smoking and mRNA expression. It is likely that multiple miRNAs regulate these target genes, and while the observed miRNA-mRNA expression direction is in concordance with the hypothesis that the altered miRNA expression contributes to the mRNA differential expression, it is not the only possible interaction.
We analyzed all miRNAs significantly differentially expressed across any of the smoking variables for associations with CIMP and MSI tumor phenotype in both colon and rectal tissues. We have previously shown that cigarette smoking is more likely to be associated with MSI and CIMP High tumors in colon cancer cases (21–23). Overall, of the 306 miRNAs associated with cigarette smoking, 41 were inversely associated with either CIMP High or MSI tumor phenotype and 200 were directly associated with CIMP High or MSI tumor molecular phenotype for either colon or rectal cancer, with directionality consistent across tissue types. Associations with these miRNAs were generally stronger for rectal tumors, however given the few MSI rectal cases, the estimates were much less precise than those observed for colon cancer. These results suggest that smoking may alter miRNAs, whose differential expression may influence CIMP and MSI tumor phenotype.
Ten miRNAs were differentially expressed in rectal tissue across current smokers versus those who had never smoked as well as with CIMP High/MSI tumor phenotype. Five of these, hsa-miR-29a-3p, hsa-miR-29b-3p, hsa-miR-30b-5p, hsa-miR-3150b-5p, and hsa-miR-425-5p, were associated with both current versus never smoking as well as CIMP High/MSI phenotype for both rectal and colon differential tissue, while hsa-miR-17-5p, hsa-miR-200a-3p, hsa-miR-4485 were associated only in colon tissue, and hsa-miR-141-3p and hsa-miR-6084 were associated only in rectal tissue. Seven of ten miRNAs, hsa-miR-29a-3p, hsa-miR-29b-3p, hsa-miR-30b-5p, hsa-miR-425-5p, hsa-miR-17-5p, hsa-miR-200a-3p, and hsa-miR-141-3p had decreased differential expression in current smokers as compared to never smokers, and this differential expression was indirectly associated with CIMP High/MSI status. Two miRNAs, hsa-miR-3150b-5p and hsa-miR-6084, had increased differential expression in current smokers compared to never smokers, and this increase in expression was directly associated with CIMP High/MSI. One miRNA, hsa-miR-4485, had increased differential expressed in current smokers with colon cancer, and this was indirectly associated with CIMP High/MSI. Current smoking compared to never smoked showed a significant association with CIMP High/MSI tumor phenotype in colon cancer cases, OR = 2.42, 95% CI 1.16 – 5.03. As nine of the 10 miRNAs associated with both current versus never smoking and CIMP High/MSI tumor phenotype had agreement in the direction of their associations, i.e. increased differential expression with current versus never smoking as well as a direct relationship with CIMP High/MSI or decreased differential expression and an inverse relationship, our data suggests that current versus never smoking alters miRNA expression, and this alteration influences the development of a CIMP High/MSI tumor.
The study has several strengths including our large sample size. This enabled us to look at colon and rectal samples separately. Since we only found miRNAs significantly differentially expressed with smoking among rectal cancer cases, we may not have found significant results if we had combined colon and rectal cancers or examined only colon cancer cases. We also consider our platform as an asset in this study. As previously stated, our platform has very high reliability and good concordance with other methods (8, 15). The large microarray platform enables a discovery approach, which is needed since previous studies have not examined miRNA expression and cigarette smoking in colorectal tissue. Another strength is the range of data available for these analyses. These data enabled us to investigate a variety of smoking variables, which was essential to this study, as we have shown that smoking temporality, duration, and amount have different influences on miRNA expression. Additionally, we have been able to examine not only how smoking is associated with miRNA expression but also how miRNAs associated with cigarette smoking are also associated with tumor molecular phenotypes that have been associated with cigarette smoking.
A limitation in this study is that, given the large numbers of miRNAs, and the overlap in genes targeted by the different miRNAs, it is very difficult to discern distinct biological pathways altered by specific miRNAs associated with smoking. This limitation is not unique to our study, but a limitation of the field in general. Since each miRNA can regulate thousands of genes, it is unknown which of the many pathways and genes targeted are most important for colorectal cancer. Additionally, most miRNA-functionality tools available are not tissue specific, and this is likely a detriment to performing functional analysis based on miRNAs only identified as being associated with cigarette smoking in rectal tissue. However, while we cannot identify the exact functionality these miRNAs have, we are able to see that these miRNAs have been associated with CRC prognosis, and this supports the assertion that smoking can have a functional impact in rectal cancer, possibly through regulation of miRNA expression. Our rectal cancer sample size was not large enough to have sufficient power to detect significant associations between smoking and CIMP/MSI tumor phenotype given the rare nature of MSI rectal tumors. We encourage others to replicate this analysis with larger samples.
5. Conclusions
Overall, our findings suggest that smoking is able to alter miRNA expression in rectal carcinoma tissue, and they lend support to the hypothesis that this alteration is responsible for worsening survival for rectal cancer cases and may influence CIMP and MSI tumor phenotype.
Supplementary Material
Highlights.
As both smoking and miRNA expression have been associated with cancer risk, we propose that current smoking and pack-years smoked alter microRNA expression in colorectal cancer.
We found that differential expression of numerous unique miRNAs are associated with current smoking or pack-years smoked, and various others were associated with all smoking variables, in rectal cancer cases.
We found that cigarette smoking was associated significantly with CIMP High/MSI tumor phenotype, and that this phenotype was associated with the differential expression of many miRNAs in both colon and rectal cancer cases.
Our findings support the hypothesis that smoking, as a lifestyle variable, is able to alter microRNA expression in rectal cancer and that this may in turn contribute to tumor molecular phenotype.
Acknowledgments
The contents of this manuscript are solely the responsibility of the authors and do not necessarily represent the official view of the National Cancer Institute. We would like to acknowledge Dr. Bette Caan and the Kaiser Permanente Medical Research Program for sample contributions, Erika Wolff and Michael Hoffman at the University of Utah for miRNA processing, Brett Milash and the Bioinformatics Shared Resource of the Huntsman Cancer Institute and University of Utah for miRNA and mRNA bioinformatics data processing, Sandie Edwards at the University of Utah for her efforts in overall study monitoring and tumor tissue collection, Dr. Wade Samowitz at the University of Utah for slide review, and Daniel Pellatt at the University of Utah for his assistance with statistical analysis.
Funding
This study was supported by NCI grants CA163683 and CA48998.
Footnotes
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C/F/N smoking: Differential miRNA expression in subjects who were current smokers at time of diagnosis compared to subjects who never smoked, and differential miRNA expression in former smokers compared to those who had never smoked.
Ethics and Consent to Participate
All participants signed an informed consent and this study was approved by the Institutional Review Board at the University of Utah; the committee numbers for this paper are IRB_00055877 and IRB_00002335.
Conflicts of Interest
Conflicts of interest: none.
Lila Mullany wrote the manuscript. Martha Slattery obtained funding and the data used in the manuscript and assisted in writing the manuscript. Roger Wolff oversaw microRNA assays. Jennifer Herrick analyzed the data. John Stevens assisted in determining appropriate statistical methodologies. All authors reviewed and provided input to the manuscript. All authors have read and approved the final version of the manuscript.
Contributor Information
Jennifer S. Herrick, Email: Jennifer.Herrick@hsc.utah.edu.
Roger K. Wolff, Email: Roger.Wolff@hsc.utah.edu.
John R. Stevens, Email: john.r.stevens@usu.edu.
Martha L. Slattery, Email: Marty.Slattery@hsc.utah.edu.
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