The p53R172H Mutant Does Not Enhance Hepatocellular Carcinoma Development and Progression

Hepatocellular carcinoma is a highly deadly malignancy, accounting for approximately 800,000 deaths worldwide every year. Mutation of the p53 tumor suppressor gene is a common genetic change in HCC, present in 30% of cases. p53R175H (corresponding to p53R172H in mice) is a hotspot for mutation that demonstrates prometastatic gain-of-function in other cancer models. Since the frequency of p53 mutation increases with tumor grade in HCC, we hypothesized that p53R172H is a gain-of-function mutation in HCC that contributes to a decrease in tumor-free survival and an increase in metastasis. In an HCC mouse model, we found that p53R172H/flox mice do not have decreased survival, increased tumor incidence, or increased metastasis, relative to p53flox/flox littermates. Analysis of cell lines derived from both genotypes indicated that there are no differences in anchorage-independent growth and cell migration. However, shRNA-mediated knockdown of mutant p53 in p53R172H-expressing HCC cell lines resulted in decreased cell migration and anchorage-independent growth. Thus, although p53 mutant-expressing cells and tumors do not have enhanced properties relative to their p53 null counterparts, p53R172H-expressing HCC cells depend on this mutant for their transformation. p53 mutants have been previously shown to bind and inhibit the p53 family proteins p63 and p73. Interestingly, we find that the levels of p63 and p73 target genes are similar in p53 mutant and p53 null HCC cells. These data suggest that pathways regulated by these p53 family members are similarly impacted by p53R172H in mutant expressing cells, and by alternate mechanisms in p53 null cells, resulting in equivalent phenotypes. Consistent with this, we find that p53 null HCC cell lines display lower levels of the TA isoforms of p63 and p73 and higher levels of DeltaNp63. Taken together these data point to the importance of p63 and p73 in constraining HCC progression

MicroRNAs of the mir-17~92 cluster regulate multiple aspects of pancreatic tumor development and progression

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy characterized by resistance to currently employed chemotherapeutic approaches. Members of the mir-17~92 cluster of microRNAs (miRNAs) are upregulated in PDAC, but the precise roles of these miRNAs in PDAC are unknown. Using genetically engineered mouse models, we show that loss of mir-17~92 reduces ERK pathway activation downstream of mutant KRAS and promotes the regression of KRASG12D-driven precursor pancreatic intraepithelial neoplasias (PanINs) and their replacement by normal exocrine tissue. In a PDAC model driven by concomitant KRASG12D expression and Trp53 heterozygosity, mir-17~92 deficiency extended the survival of mice that lacked distant metastasis. Moreover, mir-17~92-deficient PDAC cell lines display reduced invasion activity in transwell assays, form fewer invadopodia rosettes than mir-17~92-competent cell lines and are less able to degrade extracellular matrix. Specific inhibition of miR-19 family miRNAs with antagomirs recapitulates these phenotypes, suggesting that miR-19 family miRNAs are important mediators of PDAC cell invasion. Together these data demonstrate an oncogenic role for mir-17~92 at multiple stages of pancreatic tumorigenesis and progression; specifically, they link this miRNA cluster to ERK pathway activation and precursor lesion maintenance in vivo and identify a novel role for miR-19 family miRNAs in promoting cancer cell invasion

mTORC2 signaling drives the development and progression of pancreatic cancer

mTOR signaling controls several critical cellular functions and is deregulated in many cancers, including pancreatic cancer. To date, most efforts have focused on inhibiting the mTORC1 complex. However, clinical trials of mTORC1 inhibitors in pancreatic cancer have failed, raising questions about this therapeutic approach. We employed a genetic approach to delete the obligate mTORC2 subunit Rictor and identified the critical times during which tumorigenesis requires mTORC2 signaling. Rictor deletion resulted in profoundly delayed tumorigenesis. Whereas previous studies showed most pancreatic tumors were insensitive to rapamycin, treatment with a dual mTORC1/2 inhibitor strongly suppressed tumorigenesis. In late-stage tumor-bearing mice, combined mTORC1/2 and PI3K inhibition significantly increased survival. Thus, targeting mTOR may be a potential therapeutic strategy in pancreatic cancer

Activation of PyMT in β Cells Induces Irreversible Hyperplasia, but Oncogene-Dependent Acinar Cell Carcinomas When Activated in Pancreatic Progenitors

It is unclear whether the cellular origin of various forms of pancreatic cancer involves transformation or transdifferentiation of different target cells or whether tumors arise from common precursors, with tumor types determined by the specific genetic alterations. Previous studies suggested that pancreatic ductal carcinomas might be induced by polyoma middle T antigen (PyMT) expressed in non-ductal cells. To ask whether PyMT transforms and transdifferentiates endocrine cells toward exocrine tumor phenotypes, we generated transgenic mice that carry tetracycline-inducible PyMT and a linked luciferase reporter. Induction of PyMT in β cells causes β-cell hyperplastic lesions that do not progress to malignant neoplasms. When PyMT is de-induced, β cell proliferation and growth cease; however, regression does not occur, suggesting that continued production of PyMT is not required to maintain the viable expanded β cell population. In contrast, induction of PyMT in early pancreatic progenitor cells under the control of Pdx1 produces acinar cell carcinomas and β-cell hyperplasia. The survival of acinar tumor cells is dependent on continued expression of PyMT. Our findings indicate that PyMT can induce exocrine tumors from pancreatic progenitor cells, but cells in the β cell lineage are not transdifferentiated toward exocrine cell types by PyMT; instead, they undergo oncogene-dependent hyperplastic growth, but do not require PyMT for survival

Failure patterns in resected pancreas adenocarcinoma: lack of predicted benefit to SMAD4 expression.

OBJECTIVE: To determine whether SMAD4 expression is associated with recurrence pattern after resection for pancreatic ductal adenocarcinoma (PDA). BACKGROUND: SMAD4 expression status has been reported to be associated with patterns of failure in PDA, but studies have not examined recurrence patterns after resection. METHODS: A tissue microarray was constructed including 127 patients with resected PDA and either short-term (\u3c12 \u3emonths) or long-term (\u3e30 months) survival. SMAD4 expression was evaluated by immunohistochemistry and categorized as present or lost in tumor cells. Conventional pathologic features (lymph node metastases, positive resection margin, poor grade, and tumor size) were recorded, and disease-specific outcomes (eg, recurrence pattern and early cancer-specific mortality) were determined. RESULTS: Loss of SMAD4 expression in pancreatic adenocarcinoma was identified in 40 of 127 patients (32%). SMAD4 loss occurred in 27% of patients who experienced isolated local recurrence, 33% of patients with a distant recurrence, 33% of patients who experienced local and distant site recurrences, and 25% of patients who were without evidence of recurrence (Fisher exact, P = 0.9). In a multivariate analysis, the presence of regional lymph node metastases was the only factor associated with the development of distant metastases (odds ratio = 4.7, P = 0.02). SMAD4 was neither associated with recurrence pattern (odds ratio = 0.9, P = 0.9) nor associated with early death (odds ratio = 0.5, P = 0.15). CONCLUSIONS: Primary tumor SMAD4 expression status was not a predictor of recurrence pattern in a large cohort of patients with resected PDA

Comprehensive Genomic Profiling of Pancreatic Acinar Cell Carcinomas

significantly enriched for genomic alterations (GAs) causing inactivation of DNA repair genes (45%); these GAs have been associated with sensitivity to platinum-based therapies and PARP inhibitors. Collectively, these results identify potentially actionable GAs in the majority of PACCs, and provide a rationale for using personalized therapies in this disease. Statement of Significance PACC is genomically distinct from other pancreatic cancers. Fusions in RAF genes and mutually exclusive inactivation of DNA repair genes represent novel potential therapeutic targets that are altered in over two-thirds of these tumors

Integrated genomic characterization of pancreatic ductal adenocarcinoma

We performed integrated genomic, transcriptomic, and proteomic profiling of 150 pancreatic ductal adenocarcinoma (PDAC) specimens, including samples with characteristic low neoplastic cellularity. Deep whole-exome sequencing revealed recurrent somatic mutations in KRAS, TP53, CDKN2A, SMAD4, RNF43, ARID1A, TGFβR2, GNAS, RREB1, and PBRM1. KRAS wild-type tumors harbored alterations in other oncogenic drivers, including GNAS, BRAF, CTNNB1, and additional RAS pathway genes. A subset of tumors harbored multiple KRAS mutations, with some showing evidence of biallelic mutations. Protein profiling identified a favorable prognosis subset with low epithelial-mesenchymal transition and high MTOR pathway scores. Associations of non-coding RNAs with tumor-specific mRNA subtypes were also identified. Our integrated multi-platform analysis reveals a complex molecular landscape of PDAC and provides a roadmap for precision medicine

Intraductal and papillary variants of acinar cell carcinomas: a new addition to the challenging differential diagnosis of intraductal neoplasms.

The recognition and differential diagnosis of pancreatic intraductal neoplasms (IN) have gained importance in the past few years, as the incidence of these tumors (especially intraductal papillary mucinous neoplasms-IPMNs) have risen to >10% of pancreatic resections, and their significance as precursors of invasive cancer is better appreciated. Acinar cell carcinomas (ACCs) are typically solid tumors; however, we have recently encountered 7 ACCs with either intraductal growth and/or a papillary/papillocystic pattern that could be mistaken for IN. The clinicopathologic features of these cases were studied. Four patients were male and 3 female, with a mean age of 59 and mean tumor size of 4.9 cm (as compared with 10 cm in conventional ACCs). Only 1 patient had metastasis at the time of diagnosis (as opposed to 50% in usual ACCs). In 5 cases, the tumors had nodular growth of sheet-forming acinar cells, some of which were within ducts, as evidenced by the polypoid nature of the process, partial ductal lining, and presence of small tributary ducts in the walls. In 3 cases, the tumor had papillary and/or papillocystic growth, at least focally. All cases had cystic areas. No mucin was identified. All expressed trypsin. Markers of ductal differentiation were either absent or focal. A minor endocrine component was present in 3. The main histologic findings that distinguished these tumors from IPMNs were the more sheetlike nature of the nodules (rather than villous or arborizing papillae), cuboidal cells, overall basophilia of the cytoplasm, prominent nucleoli, apical granules, intraluminal crystals or pale, acidophilic secretions (enzymatic condensations), and lack of mucin. In conclusion, some ACCs show intraductal growth or exhibit papillary patterns, which can mimic IN, especially IPMNs. In such cases, attention to morphologic details described above, and immunohistochemistry are helpful. The clinical significance of this variant is difficult to determine; however, it appears that the tumors are relatively small and metastasis at presentation is less common than typically seen in ACCs (1/7 vs. 50%)

A common classification framework for neuroendocrine neoplasms: an International Agency for Research on Cancer (IARC) and World Health Organization (WHO) expert consensus proposal

The classification of neuroendocrine neoplasms (NENs) differs between organ systems and currently causes considerable confusion. A uniform classification framework for NENs at any anatomical location may reduce inconsistencies and contradictions among the various systems currently in use. The classification suggested here is intended to allow pathologists and clinicians to manage their patients with NENs consistently, while acknowledging organ-specific differences in classification criteria, tumor biology, and prognostic factors. The classification suggested is based on a consensus conference held at the International Agency for Research on Cancer (IARC) in November 2017 and subsequent discussion with additional experts. The key feature of the new classification is a distinction between differentiated neuroendocrine tumors (NETs), also designated carcinoid tumors in some systems, and poorly differentiated NECs, as they both share common expression of neuroendocrine markers. This dichotomous morphological subdivision into NETs and NECs is supported by genetic evidence at specific anatomic sites as well as clinical, epidemiologic, histologic, and prognostic differences. In many organ systems, NETs are graded as G1, G2, or G3 based on mitotic count and/or Ki-67 labeling index, and/or the presence of necrosis; NECs are considered high grade by definition. We believe this conceptual approach can form the basis for the next generation of NEN classifications and will allow more consistent taxonomy to understand how neoplasms from different organ systems inter-relate clinically and genetically