Table 4.
Molecular profiling studies revealing INK4a/ARF and RB1 pathway alterations in pNETs.
| Technique | Reference | Key Findings |
|---|---|---|
| Sequencing and mutational analysis | [24] | No INK4A/ARF mutation observed in 68 pNETs. |
| [11] | Inactivating mutations in the RB1 gene identified in 75% (3/4) small cell pNECs and 66.67% (2 of 3) large cell pNECs, however, absent in 11 well-differentiated pNETs analyzed. No CDKN2A mutations observed in 7 pNECs and 11 pNETs. |
|
| Methylation Specific PCR (MSP) | [112] | In total, 91.7% of 12 gastrinomas and non-functioning pNETs demonstrated INK4a homozygous gene deletions (41.7%) or 5′ CpG island hypermethylation. However, no mutations were found by single-strand conformation polymorphism (SSCP) analyses. |
| [103] | INK4a 5′-CpG island hypermethylation in 52% of 44 gastrinomas, along with homozygous gene deletions. | |
| [126] | In total, 17% of 17 insulinomas exhibited INK4a gene alterations: homozygous deletion in 5.9% and promoter hypermethylation in 11.8%. No INK4a mutations were identified by SSCP. IHC confirmed loss of the p16 protein expression in samples harboring gene alterations. | |
| [116] | INK4a CpG island hypermethylation in 17% of 12 pNETs, more frequently in malignant (29%) than in benign (0%) tumors. | |
| PCR (MSP or gene specific and LOH) | [114] | INK4a and ARF CpG island hypermethylation in 9% (1 out of 11) pNETs each vs. 44% and 31%, respectively, in carcinoid NETs. Chromosome 9p loss identified in 18% (2 of 11) pNETs. |
| RT-PCR | [104] | Absent expression of INK4a, INK4b, and ARF in 28% (2/7), 57% (4/7), and 43% (3/7) NF-pNETs. Loss of INK4b observed in 26% insulinomas and gastrinomas (N = 19), however, INK4a and ARF found to be expressed. |
| [35] | Overexpression of CDK4 and CDK6 in MEN1 NF-pNETs (N = 10) compared to VHL (N = 9) and sporadic (N = 9) NF-pNETs and normal islets (N = 4). | |
| Tissue microarray, qPCR, and FISH | [122] | IHC revealed high CDK4, cyclin D1 and phospho-RB1 levels in 58–68% of total pNETs (N = 92) in contrast to negative staining in the normal pancreas. qRT-PCR revealed marked upregulation of CDK4 in 19% of 26 pNETs, which were found to have amplified CDK4 or CDK6 genes by qPCR and FISH. |
| IHC | [11] | RB1 protein expression intact in well-differentiated pNETs, however, lost in 88.9% of 9 small cell and 60% of large cell pNECs. Loss of p16 expression observed in pNECs with intact RB1 suggest p16/Rb pathway is disrupted in virtually all pNECs. |