Genetic analyses of isolated high‐grade pancreatic intraepithelial neoplasia (HG‐PanIN) reveal paucity of alterations in TP53 and SMAD4

Abstract

High-grade pancreatic intraepithelial neoplasia (HG-PanIN) is the major precursor of pancreatic ductal adenocarcinoma (PDAC) and is an ideal target for early detection. To characterize pure HG-PanIN, we analysed 23 isolated HG-PanIN lesions occurring in the absence of PDAC. Whole-exome sequencing of five of these HG-PanIN lesions revealed a median of 33 somatic mutations per lesion, with a total of 318 mutated genes. Targeted next-generation sequencing of 17 HG-PanIN lesions identified KRAS mutations in 94% of the lesions. CDKN2A alterations occurred in six HG-PanIN lesions, and RNF43 alterations in five. Mutations in TP53, GNAS, ARID1A, PIK3CA, and TGFBR2 were limited to one or two HG-PanINs. No non-synonymous mutations in SMAD4 were detected. Immunohistochemistry for p53 and SMAD4 proteins in 18 HG-PanINs confirmed the paucity of alterations in these genes, with aberrant p53 labelling noted only in three lesions, two of which were found to be wild type in sequencing analyses. Sixteen adjacent LG-PanIN lesions from ten patients were also sequenced using targeted sequencing. LG-PanIN harboured KRAS mutations in 94% of the lesions; mutations in CDKN2A, TP53, and SMAD4 were not identified. These results suggest that inactivation of TP53 and SMAD4 are late genetic alterations, predominantly occurring in invasive PDAC.

High‐grade PanIN presenting with localised stricture of the main pancreatic duct: A clinicopathological and molecular study of 10 cases suggests a clue for the early detection of pancreatic cancer

“…A recent study investigated the mutational landscape of high‐grade PanIN using next‐generation sequencing . KRAS , p16/CDKN2A and TP53 were mutated in 16 of 17 (94%), six of 17 (35%) and two of 17 (12%) cases, respectively.…”

A genetic roadmap of pancreatic cancer: still evolving

“…The major implication that emerges is that the mutational hierarchy of PanIN progression has been derived from duct cancerisation events and, in consequence, a substantial proportion of the published data on PanIN-3, and possibly PanIN-2 as well, refer to cancer cells. This notion is further supported by a recent genetic analysis of PanINs by Hosoda et al , which largely failed to identify TP53 and SMAD4 mutations in PanIN-3 lesions extracted from non-PDA cases 69. Furthermore, mutational pattern analysis showed that the majority of early versus advanced PanIN were unrelated, suggesting no clonal relation within a linear progression model of these lesions.…”

“…The accuracy of the estimates and the age-adjusted prevalence of such lesions need to be determined through additional autopsy series to control for potential selection biases. Another recent study on high-grade PanINs in pancreata from non-healthy individuals lacking PDA shows that the diameter of such lesions varies from the submillimetre to the few-millimetre range 69. Therefore, it seems plausible that small PanIN lesions (≤1 mm) may have gone unnoticed in previous histopathological studies, including those from Matsuda and Mukaka, due to the sampling strategy.…”

Precursor Lesions of Pancreatic Cancer

“…Until now it was thought that PanINs frequently display abnormal p53 expression and loss of SMAD4/DPC4 expression [22,23]. However, recent studies with isolated high-grade PanINs demonstrate that aberrant p53 expression occurs only in 20% of high-grade PanINs and all high-grade PanINs show intact SMAD4/DPC4 expression [24,25]. These discrepancies in previous studies may have been due to the presence of intraductal spread of invasive ductal adenocarcinomas.…”

“…Intraductal spread, also known as intraductal cancerization, is observed in up to 70% of surgically resected PDACs [27], and is extremely difficult to differentiate from high-grade PanIN on hematoxylin and eosin-stained slides [5]. Loss of SMAD4/DPC4 expression can be a differentiating feature of intraductal spread of invasive PDAC, while high-grade PanIN shows intact SMAD4/DPC4 expression [24,25]. …”