Targeted next‐generation sequencing of cancer genes dissects the molecular profiles of intraductal papillary neoplasms of the pancreas

Abstract

Intraductal neoplasms are important precursors to invasive pancreatic cancer and an opportunity to detect and treat pancreatic neoplasia before an invasive carcinoma develops. The diagnostic evaluation of these lesions is challenging as diagnostic imaging and cytological sampling do not provide accurate information on lesion classification, the grade of dysplasia or the presence of invasion. Moreover, the molecular driver gene mutations of these precursor lesions have yet to be fully characterized. Fifty-two intraductal papillary neoplasms, including 48 intraductal papillary mucinous neoplasms (IPMNs) and 4 intraductal tubulopapillary neoplasms (ITPNs), were subjected to the mutation assessment in 51 cancer-associated genes, using Ion Torrent semiconductor-based next-generation sequencing. P16 and Smad4 immunohistochemistry was performed on 34 IPMNs, and 17 IPMN-associated carcinomas. At least one somatic mutation was observed in 46/48 (96%) IPMNs; 29 (60%) had multiple gene alterations. GNAS and/or KRAS mutations were found in 44/48 (92%) of IPMNs. GNAS was mutated in 38/48 (79%) IPMNs, KRAS in 24/48 (50%), and these mutations coexisted in 18/48 (37.5%) of IPMNs. RNF43 was the third most commonly mutated gene and was always associated with GNAS and/or KRAS mutations, as were virtually all the low frequency mutations found in other genes. Mutations in TP53 and BRAF genes (10% and 6%) were only observed in high-grade IPMNs. P16 was lost in 7/34 IPMNs and 9/17 IPMN-associated carcinomas; Smad4 was lost in 1/34 IPMN and 5/17 IPMN-associated carcinomas. In contrast to IPMNs, only one of four ITPN had detectable driver gene (GNAS and NRAS) mutations. Deep sequencing DNA from 7 cyst fluid aspirates identified 10 of the 13 mutations detected in their associated IPMN. Using next-generation sequencing to detect cyst fluid mutations has the potential to improve the diagnostic and prognostic stratification of pancreatic cystic neoplasms.

Thirty Years of Experience with Intraductal Papillary Mucinous Neoplasm of the Pancreas: From Discovery to International Consensus

“…GNAS mutations are unique to IPMN, and activation of G-protein signaling may play a crucial role in IPMN progression. Amato et al [49] reported an even higher frequency of GNAS mutation in IPMN (38/48; 79%) using next-generation sequencing. The second most common mutation was KRAS , found in 50% of IPMN, and the third most common was RNF43 , found in 14%.…”

Molecular Characterization and Pathogenesis of Intraductal Papillary Mucinous Neoplasms of the Pancreas

“…Amato et al [23] used next-generation targeted sequencing to find the most important mutations in IPMNs. They identified GNAS (79%), KRAS (50%), RNF43 (14%), TP53 (10%) and BRAF (6%) as the most important mutations.…”

“…None of the gastric- or oncocytic-type IPMNs or ITPNs show such mutations, and there is always an association with a GNAS and/or a KRAS mutation. One deletion in exon 2, one insertion in exon 3 and one insertion in exon 7, two missense variants in exons 5 and 9 and one nonsense mutation in exon 9 are found (table 2) [23]. …”

“…p53 mutations are detected in 8-10% of IPMNs in contrast to PDAC where the share amounts to 75% [8,23]. p53 expression does not demonstrate a significant difference between gastric- and intestinal-type IPMNs [11].…”

“…BRAF is altered in 6-12% of IPMNs, and a PIK3CA (exon 10 and 21) mutation can be found in 10% of IPMNs [4,19,23]. …”