Concordant loss of MTAP and p16/CDKN2A expression in pancreatic intraepithelial neoplasia: evidence of homozygous deletion in a noninvasive precursor lesion

Prevalence of S-methyl-5'-thioadenosine Phosphorylase (MTAP) Deficiency in Human Cancer: A Tissue Microarray Study on 13,067 Tumors From 149 Different Tumor Types

Loss of S-methyl-5'-thioadenosine phosphorylase (MTAP) expression is a common event in cancer leading to a critical vulnerability of cancer cells towards anti-cancer drugs. Homozygous MTAP deletions result in a complete expression loss that can be detected by immunohistochemistry (IHC). In this study, a tissue microarray containing 17,078 samples from 149 different tumor entities was analyzed by IHC, and complete MTAP loss was validated by fluorescence in situ hybridization. MTAP loss was observed in 83 of 149 tumor categories, including neuroendocrine neoplasms (up to 80%), Hodgkin lymphoma (50.0%), mesothelioma (32.0% to 36.8%), gastro-intestinal adenocarcinoma (4.0% to 40.5%), urothelial neoplasms (10.5% to 36.7%), squamous cell carcinomas (up to 38%), and various types of sarcomas (up to 20%) and non-Hodgkin lymphomas (up to 14%). Homozygous MTAP deletion was found in 90% to 100% of cases with MTAP expression loss in most tumor categories. However, neuroendocrine tumors, Hodgkin lymphomas, and other lymphomas lacked MTAP deletions. MTAP deficiency was significantly linked to unfavorable tumor phenotype in selected tumor entities and the presence of PD-L1 expression on tumor cells, absence of PD-L1 expression on immune cells, and a low density of CD8 + lymphocytes. In summary, MTAP deficiency can occur in various tumor entities and is linked to unfavorable tumor phenotype and noninflamed tumor microenvironment, but is not always related to deletions. MTAP IHC is of considerable diagnostic value for the detection of neoplastic transformation in multiple different applications.

Loss of p16 Immunoexpression and Deletions of CDKN2A in the Progression of Extramammary Paget Disease: An Immunohistochemical and Genetic Study of 24 Invasive/Metastatic Cases

ABSTRACT

Information regarding the genetic alterations in extramammary Paget disease (EMPD) is scarce. This study investigated the significance of CDKN2A and MTAP alterations in EMPD progression using immunohistochemistry and panel DNA sequencing. In total, 24 invasive/metastatic EMPD cases were included in this study. The immunoexpression of p16 and MTAP in the primary in situ, primary invasive, and metastatic tumor components was evaluated. Panel DNA sequencing was performed for metastatic tumor components in 5 of the 24 cases. Immunoexpression of p16 in the in situ tumor component was at least partially preserved in all 19 tested cases (100%). By contrast, the invasive tumor component was diffusely or partially lost in 18 (81.8%) of 22 tested cases. Regarding the foci of lymph node metastasis, 13 (81.2%) of the 16 patients showed a significant loss of p16 expression. Loss of MTAP immunoexpression was observed less frequently compared with the loss of p16 expression. CDKN2A homozygous deletions were confirmed in all 5 tested cases by sequencing, whereas MTAP deletions were detected in only 2 cases. In conclusion, p16 expression loss and CDKN2A deletions can be frequently seen in invasive/metastatic cases of EMPD.

Comparing loss of p16 and MTAP expression in detecting CDKN2A homozygous deletion in pleomorphic xanthoastrocytoma

Pleomorphic xanthoastrocytomas (PXAs) harbor CDKN2A homozygous deletion in >90% of cases, resulting in loss of p16 expression by immunohistochemistry. Considering the proximity of MTAP to CDKN2A and their frequent concurrent deletions, loss of MTAP expression may be a surrogate for CDKN2A homozygous deletion. We evaluated p16 and MTAP expression in 38 patient PXAs (CNS WHO grade 2: n = 23, 60.5%; grade 3: n = 15, 39.5%) with available chromosomal microarray data to determine whether MTAP can be utilized independently or in combination with p16 to predict CDKN2A status. CDKN2A, CDKN2B, and MTAP homozygous deletion were present in 37 (97.4%), 36 (94.7%), and 25 (65.8%) cases, respectively. Expression of p16 was lost in 35 (92.1%) cases, equivocal in one (2.6%), and failed in 2 (5.3%), while MTAP expression was lost in 27 (71.1%) cases, retained in 10 (26.3%), and equivocal in one (2.6%). This yielded a sensitivity of 94.6% for p16 and 73.0% for MTAP in detecting CDKN2A homozygous deletion through immunohistochemistry. MTAP expression was lost in the 2 cases with failed p16 staining (combined sensitivity of 100%). Our findings demonstrate that combined p16 and MTAP immunostains correctly detect CDKN2A homozygous deletion in PXA, while MTAP expression alone shows reduced sensitivity.

Loss of methylthioadenosine phosphorylase immunoreactivity correlates with poor prognosis and elevated uptake of 11C-methionine in IDH-mutant astrocytoma

PURPOSE

The proximate localization of MTAP, which encodes methylthioadenosine phosphorylase, and CDKN2A/B on Chromosome 9q21 has allowed the loss of MTAP expression as a surrogate for homozygous deletion of CDKN2A/B. This study aimed to determine whether MTAP status correlates with clinical outcomes and 11C-methionine uptake in astrocytomas with IDH mutations.

METHODS

We conducted immunohistochemistry for MTAP in 30 patients with astrocytoma, IDH-mutant who underwent 11C-methionine positron emission tomography scans prior to surgical resection. The tumor-to-normal (T/N) ratio of 11C-methionine uptake was calculated using the mean standardized uptake value (SUV) for tumor and normal brain tissues. Cox regression analysis was used for multivariate survival analysis.

RESULTS

Among IDH-mutant astrocytomas, 26.7% (8/30) exhibited the loss of cytoplasmic MTAP expression, whereas 73.3% (22/30) tumors retained MTAP expression. The median progression-free survival (PFS) was significantly shorter in patients with MTAP loss than those with MTAP retention (1.88 years vs. 6.80 years, p = 0.003). The median overall survival (OS) was also shorter in patients with MTAP loss than in MTAP-retaining counterparts (5.23 years vs. 10.69 years, p = 0.019). Multivariate analysis identified MTAP status (hazard ratio (HR), 0.081) and extent of resection (HR, 0.104) as independent prognostic factors for PFS. Astrocytomas lacking cytoplasmic MTAP expression showed a significantly higher median T/N ratio for 11C-methionine uptake than tumors retaining MTAP (2.12 vs. 1.65, p = 0.012).

CONCLUSION

Our study revealed that the loss of MTAP expression correlates with poor prognosis and an elevated T/N ratio of 11C-methionine uptake in astrocytoma, IDH-mutant.

Impact of KRAS mutations and co-mutations on clinical outcomes in pancreatic ductal adenocarcinoma

The relevance of KRAS mutation alleles to clinical outcome remains inconclusive in pancreatic adenocarcinoma (PDAC). We conducted a retrospective study of 803 patients with PDAC (42% with metastatic disease) at MD Anderson Cancer Center. Overall survival (OS) analysis demonstrated that KRAS mutation status and subtypes were prognostic (p < 0.001). Relative to patients with KRAS wildtype tumors (median OS 38 months), patients with KRASG12R had a similar OS (median 34 months), while patients with KRASQ61 and KRASG12D mutated tumors had shorter OS (median 20 months [HR: 1.9, 95% CI 1.2-3.0, p = 0.006] and 22 months [HR: 1.7, 95% CI 1.3-2.3, p < 0.001], respectively). There was enrichment of KRASG12D mutation in metastatic tumors (34% vs 24%, OR: 1.7, 95% CI 1.2-2.4, p = 0.001) and enrichment of KRASG12R in well and moderately differentiated tumors (14% vs 9%, OR: 1.7, 95% CI 1.05-2.99, p = 0.04). Similar findings were observed in the external validation cohort (PanCAN's Know Your Tumor® dataset, n = 408).

Reliability assessment of methylthioadenosine phosphorylase immunohistochemistry as a surrogate biomarker for CDKN2A homozygous deletion in adult-type IDH-mutant diffuse gliomas

According to the 2021 World Health Organization classification of brain tumors, astrocytomas containing a CDKN2A/B homozygous deletion (HD) are designated as grade 4 even when no microvascular proliferation and/or necrosis is present. In this study, we aimed to investigate the relationship between CDKN2A HD and loss of methylthioadenosine phosphorylase (MTAP) expression in adult-type IDH-mutant gliomas and to assess the sensitivity and specificity of MTAP immunohistochemistry (IHC) along with interobserver agreement as a surrogate biomarker for CDKN2A HD. Eighty-eight astrocytomas and 71 oligodendrogliomas cases that were diagnosed between 2014 and 2021 at Hacettepe University were selected and tissue microarrays were conducted to perform CDKN2A fluorescence in situ hybridization and MTAP IHC. Twenty-five (15.7%) cases harbored CDKN2A HD. MTAP loss was detected in 28 (15.7%) cases by the first observer and 27 (17%) cases by the second observer. The sensitivity and specificity of MTAP were calculated as 88% and 95.52%-96.27% for 2 observers. A very good/perfect agreement was noted between the observers (Cohen kappa coefficient = 0.938). Intratumoral heterogeneity was observed in 4 cases. MTAP IHC was found to be a reliable surrogate biomarker as a possible alternative to CDKN2A HD identification with a high sensitivity and specificity along with high interobserver agreement.

Deletions of CDKN2A and MTAP Detected by Copy-Number Variation Array Are Associated with Loss of p16 and MTAP Protein in Pleural Mesothelioma

CDKN2A deletion is a common alteration in pleural mesothelioma (PM) and frequently associated with co-deletion of MTAP. Since the standard detection method for CDKN2A deletion and FISH analysis is relatively expensive, we here investigated the suitability of inexpensive p16 and MTAP IHC by comparing concordance between IHC and OncoScan CNV arrays on samples from 52 PM patients. Concordance was determined using Cohen's kappa statistics. Loss of CDKN2A was associated with co-deletion of MTAP in 71% of cases. CDKN2A-MTAP copy-number normal cases were also IHC positive in 93% of cases for p16 and 100% for MTAP, while homozygous deletion of CDKN2A-MTAP was always associated with negative IHC for both proteins. In cases with heterozygous CDKN2A-MTAP loss, IHC expression of p16 and MTAP was negative in 100% and 71%, respectively. MTAP and p16 IHC showed high sensitivity (MTAP 86.5%, p16 100%) and specificity (MTAP 100%, p16 93.3%) for the detection of any gene loss. Loss of MTAP expression occurred exclusively in conjunction with loss of p16 labeling. Both p16 and MTAP IHC showed high concordance with Oncoscan CNV arrays (kappa = 0.952, p < 0.0001, and kappa = 0.787, p < 0.0001 respectively). We recommend combined MTAP and p16 immunohistochemistry to confirm the diagnosis of PM.

Post-operative mortality and recurrence patterns in pancreatic cancer according to KRAS mutation and CDKN2A, p53, and SMAD4 expression

Alterations in KRAS, CDKN2A (p16), TP53, and SMAD4 genes have been major drivers of pancreatic carcinogenesis. The clinical course of patients with pancreatic cancer in relation to these driver alterations has not been fully characterised in large populations. We hypothesised that pancreatic carcinomas with different combinations of KRAS mutation and aberrant expression of CDKN2A, p53, and SMAD4 might show distinctive recurrence patterns and post-operative survival outcomes. To test this hypothesis, we utilised a multi-institutional cohort of 1,146 resected pancreatic carcinomas and assessed KRAS mutations by droplet digital polymerase chain reaction and CDKN2A, p53, and SMAD4 expression by immunohistochemistry. Multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) for disease-free survival (DFS) and overall survival (OS) were computed according to each molecular alteration and the number of altered genes using the Cox regression models. Multivariable competing risks regression analyses were conducted to assess the associations of the number of altered genes with specific patterns of recurrence. Loss of SMAD4 expression was associated with short DFS (multivariable HR, 1.24; 95% CI, 1.09-1.43) and OS times (multivariable HR, 1.27; 95% CI, 1.10-1.46). Compared to cases with 0-2 altered genes, cases with three and four altered genes had multivariable HRs for OS of 1.28 (95% CI, 1.09-1.51) and 1.47 (95% CI, 1.22-1.78), respectively (ptrend  < 0.001). Patients with an increasing number of altered genes were more likely to have short DFS time (ptrend  = 0.003) and to develop liver metastasis (ptrend  = 0.006) rather than recurrence at local or other distant sites. In conclusion, loss of SMAD4 expression and an increasing number of altered genes were associated with unfavourable outcomes in pancreatic cancer patients. This study suggests that the accumulation of the four major driver alterations can confer a high metastatic potential to the liver, thereby impairing post-operative survival among patients with pancreatic cancer.

A prospective prognostic signature for pancreatic adenocarcinoma based on ubiquitination-related mRNA-lncRNA with experimental validation in vitro and vivo

Ubiquitination-related genes (URGs) exerted a crucial part in a variety of human disease disorders; however, their association with pancreatic adenocarcinoma (PAAD) had yet to be clearly described. We aimed to comprehensively characterize the contributions of URGs in PAAD through in silico analysis and experimental validation, and then identified a robust mRNA-lncRNA-based molecular prognostic panel for patients with PAAD using bulk RNA-sequencing and single-cell RNA-sequencing data. Initially, we collected the multi-omics data from TCGA platform to depict a comprehensive landscape of URGs in pan-cancer. Furthermore, we were accurate to PAAD for in-depth analysis. Significant differences of the activation of ubiquitination pathways and the expression of URGs were detected between normal and malignant cells. Unsupervised hierarchical clustering determined two PAAD subtypes with distinct clinical outcomes, ubiquitination pathway activities, immune microenvironment, and functional annotation characteristics. The expression profiles of ubiquitination-associated mRNAs and lncRNAs in the training and validation datasets were utilized to develop and verify a novel ubiquitination-related mRNA-lncRNA prognostic panel, which had a satisfied prediction efficiency. Our ubiquitination-associated model could function as an effective prognostic index and outperformed four other recognized panels in evaluating PAAD patients' survival status. Tumor immune microenvironment, mutation burden, and chemotherapy response were intensively explored to demonstrate the underlying mechanism of prognostic difference according to our panel. Our findings also revealed that FTI-277, a farnesyltransferase inhibitor, had a better curative effect in high-risk patients, while MK-2206, an Akt allosteric inhibitor, had a superior therapeutic effect in low-risk patients. The real-time PCR results uncovered the RNA expression of AC005062.1 in all the three PAAD cell lines was elevated several thousandfold. In conclusion, our URGs-based classification panel could be triumphantly served as a prediction tool for survival evaluation in patients with PAAD, and the genes in this panel could be developed as a potential target in PAAD therapy.

Advanced pancreatic cancer with KRAS wild-type and EGFR-sensitive mutation respond favorably to furmonertinib: A case report

Pancreatic cancer is the leading cause of cancer death, and treatment options are limited and mostly ineffective. The patient we report had an EGFR exon 19 deletion and had disease progression in the short term after receiving three front-line treatment regimens. We administered furmonertinib and observed tumor shrinkage, decreased CA19-9. The progression-free survival (PFS) of furmonertinib was 4.7 months, and no adverse effects were observed. However, the patient did not benefit from subsequent nimotuzumab-based therapy. Targeted therapy driven by the detection of genetic signatures in this patient shows potential clinical benefit in refractory advanced pancreatic cancer.

Homozygous MTAP deletion in primary human glioblastoma is not associated with elevation of methylthioadenosine

Homozygous deletion of methylthioadenosine phosphorylase (MTAP) in cancers such as glioblastoma represents a potentially targetable vulnerability. Homozygous MTAP-deleted cell lines in culture show elevation of MTAP’s substrate metabolite, methylthioadenosine (MTA). High levels of MTA inhibit protein arginine methyltransferase 5 (PRMT5), which sensitizes MTAP-deleted cells to PRMT5 and methionine adenosyltransferase 2A (MAT2A) inhibition. While this concept has been extensively corroborated in vitro, the clinical relevance relies on exhibiting significant MTA accumulation in human glioblastoma. In this work, using comprehensive metabolomic profiling, we show that MTA secreted by MTAP-deleted cells in vitro results in high levels of extracellular MTA. We further demonstrate that homozygous MTAP-deleted primary glioblastoma tumors do not significantly accumulate MTA in vivo due to metabolism of MTA by MTAP-expressing stroma. These findings highlight metabolic discrepancies between in vitro models and primary human tumors that must be considered when developing strategies for precision therapies targeting glioblastoma with homozygous MTAP deletion.

The metabolite methylthioadenosine (MTA) inhibits PRMT5. Therefore, MTA accumulation due to MTA phosphorylase (MTAP) deletion has been proposed as a vulnerability for PRMT5-targeted therapy in cancer. Here, the authors show that MTA does not accumulate in MTAP-deficient cancer cells but is secreted and metabolized by MTAP-intact cells in the tumour microenvironment.

Combined Blockade of MEK and CDK4/6 Pathways Induces Senescence to Improve Survival in Pancreatic Ductal Adenocarcinoma

Activating KRAS mutations, a defining feature of pancreatic ductal adenocarcinoma (PDAC), promote tumor growth in part through the activation of cyclin-dependent kinases (CDK) that induce cell-cycle progression. p16INK4a (p16), encoded by the gene CDKN2A, is a potent inhibitor of CDK4/6 and serves as a critical checkpoint of cell proliferation. Mutations in and subsequent loss of the p16 gene occur in PDAC at a rate higher than that reported in any other tumor type and results in Rb inactivation and unrestricted cellular growth. Therefore, strategies targeting downstream RAS pathway effectors combined with CDK4/6 inhibition (CDK4/6i) may have the potential to improve outcomes in this disease. Herein, we show that expression of p16 is markedly reduced in PDAC tumors compared with normal pancreatic or pre-neoplastic tissues. Combined MEK inhibition (MEKi) and CDK4/6i results in sustained downregulation of both ERK and Rb phosphorylation and a significant reduction in cell proliferation compared with monotherapy in human PDAC cells. MEKi with CDK4/6i reduces tumor cell proliferation by promoting senescence-mediated growth arrest, independent of apoptosis in vitro We show that combined MEKi and CDK4/6i treatment attenuates tumor growth in xenograft models of PDAC and improves overall survival over 200% compared with treatment with vehicle or individual agents alone in Ptf1acre/+ ;LSL-KRASG12D/+ ;Tgfbr2flox/flox (PKT) mice. Histologic analysis of PKT tumor lysates reveal a significant decrease in markers of cell proliferation and an increase in senescence-associated markers without any significant change in apoptosis. These results demonstrate that combined targeting of both MEK and CDK4/6 represents a novel therapeutic strategy to synergistically reduce tumor growth through induction of cellular senescence in PDAC.

Dominant role of CDKN2B/p15INK4B of 9p21.3 tumor suppressor hub in inhibition of cell-cycle and glycolysis

Human chromosome 9p21.3 is susceptible to inactivation in cell immortalization and diseases, such as cancer, coronary artery disease and type-2 diabetes. Although this locus encodes three cyclin-dependent kinase (CDK) inhibitors (p15^INK4B, p14^ARF and p16^INK4A), our understanding of their functions and modes of action is limited to the latter two. Here, we show that in vitro p15^INK4B is markedly stronger than p16^INK4A in inhibiting pRb1 phosphorylation, E2F activity and cell-cycle progression. In mice, urothelial cells expressing oncogenic HRas and lacking p15^INK4B, but not those expressing HRas and lacking p16^INK4A, develop early-onset bladder tumors. The potency of CDKN2B/p15^INK4B in tumor suppression relies on its strong binding via key N-terminal residues to and inhibition of CDK4/CDK6. p15^INK4B also binds and inhibits enolase-1, a glycolytic enzyme upregulated in most cancer types. Our results highlight the dual inhibition of p15^INK4B on cell proliferation, and unveil mechanisms whereby p15^INK4B aberrations may underpin cancer and non-cancer conditions.

The human chromosome locus 9p21.3 is a tumour suppressor hub which encodes three CDK inhibitors, p15INK4B, p14ARF and p16INK4A. Here, the authors show that p15INK4B inhibits the cell cycle and glycolysis in a murine model of HRas + ‐mediated urothelial carcinoma and has a more relevant role as a tumour suppressor than its neighbouring p16INK4A.

Utility of methylthioadenosine phosphorylase immunohistochemical deficiency as a surrogate for CDKN2A homozygous deletion in the assessment of adult-type infiltrating astrocytoma

Homozygous deletion (HD) of CDKN2A is one of the most promising biomarkers for predicting poor prognosis of IDH-mutant diffuse gliomas. The Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy (cIMPACT-NOW) recommendations propose that IDH-mutant lower-grade astrocytomas with CDKN2A/B HD be classified as grade IV tumors. Loss of methylthioadenosine phosphorylase (MTAP) immunohistochemistry staining has been proposed as a surrogate of CDKN2A HD in various tumors but its performance has not been fully investigated in diffuse glioma. This study determined whether MTAP immunoreactivity could serve as a proxy for CDKN2A HD in adult-type diffuse glioma, thereby contributing to stratifying patient outcome. MTAP immunohistochemistry staining using clone EPR6893 was scored in 178 diffuse glioma specimens consisting of 77 IDH-mutant astrocytomas, 13 IDH-mutant oligodendrogliomas, and 88 IDH-wildtype glioblastomas. The use of MTAP immunohistochemical deficiency to predict CDKN2A HD was good for IDH-mutant astrocytomas (sensitivity, 88%; specificity, 98%) and IDH-wildtype glioblastomas (sensitivity, 89%; specificity, 100%), but poor for IDH-mutant oligodendrogliomas (sensitivity, 67%; specificity, 57%). Both CDKN2A HD and MTAP immunohistochemical deficiency were significant adverse prognostic factors of overall survival for IDH-mutant astrocytoma (P < 0.001 each), but neither were prognostically significant for oligodendroglioma or IDH-wildtype glioblastoma. IDH-mutant lower-grade astrocytoma with CDKN2A HD and deficient MTAP immunoreactivity exhibited overlapping unfavorable outcome with IDH-mutant glioblastoma. MTAP immunostaining was easily interpreted in 61% of the cases tested, but scoring required greater care in the remaining cases. An alternative MTAP antibody clone (2G4) produced identical scoring results in all but 1 case, and a slightly larger proportion (66%) of cases were considered easy to interpret compared to using EPR6893. In summary, loss of MTAP immunoreactivity could serve as a reasonable predictive surrogate for CDKN2A HD in IDH-mutant astrocytomas and IDH-wildtype glioblastomas and could provide significant prognostic value for IDH-mutant astrocytoma, comparable to CDKN2A HD.

Molecular Alterations in Pancreatic Cancer: Transfer to the Clinic

Pancreatic ductal adenocarcinoma (PDA) is the most common cancer of the exocrine pancreas and probably the tumor that has benefited the least from clinical progress in the last three decades. A consensus has been reached regarding the histologic classification of the ductal preneoplastic lesions (pancreatic intra-epithelial neoplasia-PanIN) and the molecular alterations associated with them. Mutations in KRAS and inactivation of CDKN2A, SMAD4 and TP53 are among the most prevalent alterations. Next generation sequencing studies are providing a broad picture of the enormous heterogeneity in this tumor type, describing new mutations less prevalent. These studies have also allowed the characterization of different subtypes with prognostic value. However, all this knowledge has not been translated into a clinical progress. Effective preventive and early diagnostic strategies are essential to improve the survival rates. The main challenge is, indeed, to identify new effective drugs. Despite many years of research and its limited success, gemcitabine is still the first line treatment of PDA. New drug combinations and new concepts to improve drug delivery into the tumor, as well as the development of preclinical predictive assays, are being explored and provide optimism and prospects for better therapies.

Regulation of metabolic reprogramming by tumor suppressor genes in pancreatic cancer

Background

Pancreatic cancer continues to be one of the most aggressive malignant tumors. Work in recent years in cancer molecular biology has revealed that metabolic reprogramming is an additional hallmark of cancer that is involved in the pathogenesis of cancers, and is intricately linked to gene mutations.

Main text

However, though oncogenes such as KRAS and c-Myc play important roles in the process, and have been extensively studied, no substantial improvements in the prognosis of pancreatic cancer have seen. Therefore, some scientists have tried to explain the mechanisms of abnormal cancer metabolism from the perspective of tumor suppressor genes. In this paper, we reviewed researches about how metabolic reprogramming was regulated by tumor suppressor genes in pancreatic cancer and their clinical implications.

Conclusion

Abnormal metabolism and genetic mutations are mutually causal and complementary in tumor initiation and development. A clear understanding of how metabolic reprogramming is regulated by the mutated genes would provide important insights into the pathogenesis and ultimately treatment of pancreatic cancer.

From somatic mutation to early detection: insights from molecular characterization of pancreatic cancer precursor lesions

Pancreatic cancer arises from noninvasive precursor lesions, including pancreatic intraepithelial neoplasia (PanIN), intraductal papillary mucinous neoplasm (IPMN), and mucinous cystic neoplasm (MCN), which are curable if detected early enough. Recently, these types of precursor lesions have been extensively characterized at the molecular level, defining the timing of critical genetic alterations in tumorigenesis pathways. The results of these studies deepen our understanding of tumorigenesis in the pancreas, providing novel insights into tumor initiation and progression. Perhaps more importantly, they also provide a rational foundation for early detection approaches that could allow clinical intervention prior to malignant transformation. In this review, we summarize the results of comprehensive molecular characterization of PanINs, IPMNs, and MCNs and discuss the implications for cancer biology as well as early detection. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

miRNA and Gene Expression in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains a challenging disease that is mostly diagnosed late in the course of the illness. Unlike other cancers in which measurable successes have been achieved with traditional chemotherapy, targeted therapy, and, recently, immunotherapy, PDAC has proved to be poorly responsive to these treatments, with only marginal to modest incremental benefits using conventional cytotoxic therapy. There is, therefore, a great unmet need to develop better therapies based on improved understanding of biology and identification of predictive and prognostic biomarkers that would guide therapy. miRNAs are small noncoding RNAs that regulate the expression of some key genes by targeting their 3'-untranslated mRNA region. Aberrant expression of miRNAs has been linked to the development of various malignancies, including PDAC. A series of miRNAs have been identified as potential tools for early diagnosis, prediction of treatment response, and prognosis of patients with PDAC. In this review, we present a summary of the miRNAs that have been studied in PDAC in the context of disease biology.

Well-differentiated Pancreatic Neuroendocrine Tumor in a Patient With Familial Atypical Multiple Mole Melanoma Syndrome (FAMMM)

Germline mutations in CDKN2A result in Familial Atypical Multiple Mole Melanoma Syndrome (FAMMM), which is associated with an increased risk for pancreatic ductal adenocarcinoma and melanoma. CDKN2A is somatically inactivated in multiple neoplasms, raising the possibility that, although the data are not conclusive, germline CDKN2A mutation may also impose an increased risk for other neoplasms. We present a patient with a CDKN2A germline mutation (p16-Leiden mutation) and mosaicism for neurofibromatosis type 2, who presented with a small asymptomatic pancreatic lesion, detected during endoscopic ultrasound screening of the pancreas. After resection, the lesion was found to be a well-differentiated pancreatic neuroendocrine tumor (PanNET). Molecular analysis of the tumor showed somatic loss of the second allele, supporting a causal relation of the PanNET to the underlying FAMMM syndrome. Recent data, showing the association between certain single-nucleotide polymorphisms in the CDKN2A gene and an increased incidence for PanNET, further support a role for germline CDKN2A alterations in PanNET risk. We conclude that PanNETs can be a phenotypic expression of FAMMM syndrome. This can have implications for screening and for the diagnosis of pancreatic neoplasms in carriers of germline CDKN2A mutations.

Fendiline Enhances the Cytotoxic Effects of Therapeutic Agents on PDAC Cells by Inhibiting Tumor-Promoting Signaling Events: A Potential Strategy to Combat PDAC

The L-type calcium channel blocker fendiline has been shown to interfere with Ras-dependent signaling in K-Ras mutant cancer cells. Earlier studies from our lab had shown that treatment of pancreatic cancer cells with fendiline causes significant cytotoxicity and interferes with proliferation, survival, migration, invasion and anchorage independent growth. Currently there are no effective therapies to manage PDACs. As fendiline has been approved for treatment of patients with angina, we hypothesized that, if proven effective, combinatorial therapies using this agent would be easily translatable to clinic for testing in PDAC patients. Here we tested combinations of fendiline with gemcitabine, visudyne (a YAP1 inhibitor) or tivantinib (ARQ197, a c-Met inhibitor) for their effectiveness in overcoming growth and oncogenic characteristics of PDAC cells. The Hippo pathway component YAP1 has been shown to bypass K-Ras addiction, and allow tumor growth, in a Ras-null mouse model. Similarly, c-Met expression has been associated with poor prognosis and metastasis in PDAC patients. Our results presented here show that combinations of fendiline with these inhibitors show enhanced anti-tumor activity in Panc1, MiaPaCa2 and CD18/HPAF PDAC cells, as evident from the reduced viability, migration, anchorage-independent growth and self-renewal. Biochemical analysis shows that these agents interfere with various signaling cascades such as the activation of Akt and ERK, as well as the expression of c-Myc and CD44 that are altered in PDACs. These results imply that inclusion of fendiline may improve the efficacy of various chemotherapeutic agents that could potentially benefit PDAC patients.

Targeting retinoblastoma protein phosphorylation in combination with EGFR inhibition in pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) remains a particularly lethal disease that is resistant to targeted therapies. Tyrosine kinase inhibitors (TKIs), including erlotinib and gefitinib, which block the action of the human epidermal growth factor receptor type 1 receptor, provide small increases in patient survival when administered with gemcitabine. The retinoblastoma (Rb) tumor suppressor protein is an additional target in pancreatic cancer, due to its documented inactivation in PDAC. The present study, using cell number, apoptosis and immunoblotting assays, aimed to evaluate the effects of activation of the Rb tumor suppressor via dephosphorylation by small interfering RNA-mediated phosphatase activation. In the Panc1, MIAPaCa-2 and Capan-2 pancreatic cancer cell lines, and in normal H6c7 cells, the effects of phosphatase activation on Rb were revealed to be dependent on expression of the p16 tumor suppressor, which regulates Rb phosphorylation. Phosphatase activation had no effect on non-transformed pancreatic epithelial cells. When comparing kinase inhibition with phosphatase activation, it was demonstrated that kinase inhibition reduced proliferation, whereas phosphatase activation induced apoptosis. Both treatments together resulted in a greater reduction of pancreatic cancer cells than either treatment alone. In addition, the effects of combination treatment of phosphatase activation with TKIs on cell number and activation of the signal transducer and activator of transcription 3 (STAT3) resistance pathway were determined. The combination of Rb phosphatase activation with TKIs resulted in a greater reduction in cell number compared with either treatment alone, without STAT3 pathway activation. These data suggested that targeting Rb phosphorylation by activating phosphatase may be a rational strategy to inhibit pancreatic tumor cell growth, without activation of acquired resistance.

Systems Oncology: Bridging Pancreatic and Castrate Resistant Prostate Cancer

Large investments by pharmaceutical companies in the development of new antineoplastic drugs have not been resulting in adequate advances of new therapies. Despite the introduction of new methods, technologies, translational medicine and bioinformatics, the usage of collected knowledge is unsatisfactory. In this paper, using examples of pancreatic ductal adenocarcinoma (PaC) and castrate-resistant prostate cancer (CRPC), we proposed a concept showing that, in order to improve applicability of current knowledge in oncology, the re-clustering of clinical and scientific data is crucial. Such an approach, based on systems oncology, would include bridging of data on biomarkers and pathways between different cancer types. Proposed concept would introduce a new matrix, which enables combining of already approved therapies between cancer types. Paper provides a (a) detailed analysis of similarities in mechanisms of etiology and progression between PaC and CRPC, (b) diabetes as common hallmark of both cancer types and (c) knowledge gaps and directions of future investigations. Proposed horizontal and vertical matrix in cancer profiling has potency to improve current antineoplastic therapy efficacy. Systems biology map using Systems Biology Graphical Notation Language is used for summarizing complex interactions and similarities of mechanisms in biology of PaC and CRPC.

The evolution into personalized therapies in pancreatic ductal adenocarcinoma: challenges and opportunities

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) is projected to be the second leading cause of cancer related mortality in the United States in 2030, with a 5-year overall survival of less than 10% despite decades of extensive research. Pancreatic cancer is marked by the accumulation of complex molecular changes, complex tumor-stroma interaction, and an immunosuppressive tumor microenvironment. PDAC has proven to be resistant to many cytotoxic, targeted and immunologic treatment approaches. Areas covered: In this paper, we review the major areas of research in PDAC, with highlights on the challenges and areas of opportunity for personalized treatment approaches. Expert commentary: The focus of research in pancreatic cancer has moved away from developing conventional cytotoxic combinations. The marked advances in understanding the molecular biology of this disease especially in the areas of the microenvironment, metabolism, and DNA repair have opened new opportunities for developing novel treatment strategies. Improved understanding of molecular abnormalities allows the development of personalized treatment approaches.

A genetic roadmap of pancreatic cancer: still evolving

A diagnosis of pancreatic ductal adenocarcinoma (PDA) is often fatal. PDA is widely recognised as one of the 'incurable cancers' because therapies against this tumour type are generally ineffective. The fatal nature of this tumour is due to its aggressive clinical course. Pancreatic cancer commonly presents at the metastatic stage; even in cases where tumours are localised to the pancreas at diagnosis, metastatic seeds have often been invariably been spawned off, frustrating surgical attempts to cure the cancer. The key principles of pancreatic cancer mutational development were outlined nearly two decades ago using the genetics of precursor lesions to position the various stages of tumour progression. Since then, there has been a cavalcade of new data. How these recent studies impact the classical perceptions of pancreatic cancer development is a work in progress. Given that significant improvements in patient outcomes are not in sight for this disease, it is likely that broadening the current perspectives and acquiring deeper biological insights into the morphogenetic route of tumour development will be needed to foster new strategies for more effective cancer control.

Collagen-derived proline promotes pancreatic ductal adenocarcinoma cell survival under nutrient limited conditions

Tissue architecture contributes to pancreatic ductal adenocarcinoma (PDAC) phenotypes. Cancer cells within PDAC form gland-like structures embedded in a collagen-rich meshwork where nutrients and oxygen are scarce. Altered metabolism is needed for tumour cells to survive in this environment, but the metabolic modifications that allow PDAC cells to endure these conditions are incompletely understood. Here we demonstrate that collagen serves as a proline reservoir for PDAC cells to use as a nutrient source when other fuels are limited. We show PDAC cells are able to take up collagen fragments, which can promote PDAC cell survival under nutrient limited conditions, and that collagen-derived proline contributes to PDAC cell metabolism. Finally, we show that proline oxidase (PRODH1) is required for PDAC cell proliferation in vitro and in vivo. Collectively, our results indicate that PDAC extracellular matrix represents a nutrient reservoir for tumour cells highlighting the metabolic flexibility of this cancer.

Cancer cells adapt their metabolism to survive limited nutrient availability. Here, the authors show that in conditions of limited glucose or glutamine availability, pancreatic ductal adenocarcinoma cells can use collagen-derived proline to foster the TCA cycle and allow cell survival both in vitro and in vivo.

Molecular Genetics of Pancreatic Neoplasms

Pancreatic neoplasms have a wide range of histologic types with distinct clinical outcomes. Recent advances in high-throughput sequencing technologies have greatly deepened our understanding of pancreatic neoplasms. Now, the exomes of major histologic types of pancreatic neoplasms have been sequenced, and their genetic landscapes have been revealed. This article reviews the molecular changes underlying pancreatic neoplasms, with a special focus on the genetic changes that characterize the histologic types of pancreatic neoplasms. Emphasis is also made on the molecular features of key genes that have the potential for therapeutic targets.

Clinical applications of circulating tumor DNA and circulating tumor cells in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is the most frequent pancreatic cancer type and is characterized by a dismal prognosis due to late diagnosis, local tumor invasion, frequent distant metastases and poor sensitivity to current therapy. In this context, circulating tumor cells and circulating tumor DNA constitute easily accessible blood-borne tumor biomarkers that may prove their clinical interest for screening, early diagnosis and metastatic risk assessment of PDAC. Moreover these markers represent a tool to assess PDAC mutational landscape. In this review, together with key biological findings, we summarize the clinical results obtained using "liquid biopsies" at the different stages of the disease, for early and metastatic diagnosis as well as monitoring during therapy.

Characterization of MTAP Gene Expression in Breast Cancer Patients and Cell Lines

MTAP is a ubiquitously expressed gene important for adenine and methionine salvage. The gene is located at 9p21, a chromosome region often deleted in breast carcinomas, similar to CDKN2A, a recognized tumor suppressor gene. Several research groups have shown that MTAP acts as a tumor suppressor, and some therapeutic approaches were proposed based on a tumors´ MTAP status. We analyzed MTAP and CDKN2A gene (RT-qPCR) and protein (western-blotting) expression in seven breast cancer cell lines and evaluated their promoter methylation patterns to better characterize the contribution of these genes to breast cancer. Cytotoxicity assays with inhibitors of de novo adenine synthesis (5-FU, AZA and MTX) after MTAP gene knockdown showed an increased sensitivity, mainly to 5-FU. MTAP expression was also evaluated in two groups of samples from breast cancer patients, fresh tumors and paired normal breast tissue, and from formalin-fixed paraffin embedded (FFPE) core breast cancer samples diagnosed as Luminal-A tumors and triple negative breast tumors (TNBC). The difference of MTAP expression between fresh tumors and normal tissues was not statistically significant. However, MTAP expression was significantly higher in Luminal-A breast tumors than in TNBC, suggesting the lack of expression in more aggressive breast tumors and the possibility of using the new approaches based on MTAP status in TNBC.

Characterization and Prognostic Significance of Methylthioadenosine Phosphorylase Deficiency in Nasopharyngeal Carcinoma

Identification of cancer-associated genes by genomic profiling contributes to the elucidation of tumor development and progression. The methylthioadenosine phosphorylase (MTAP) gene, located at chromosome 9p21, plays a critical role in tumorigenicity and disease progression in a wide variety of cancers. However, the prognostic impact of MTAP in patients with nasopharyngeal carcinoma (NPC) remains obscured. Through data mining from published transcriptomic database, MTAP was first identified as a differentially downregulated gene in NPC. In this study, our aim was to evaluate the expression of MTAP in NPC and to clarify its prognostic significance.MTAP immunohistochemistry was retrospectively performed and analyzed in biopsy specimens from 124 NPC patients who received standard treatment without distant metastasis at initial diagnosis. The immunoexpression status was correlated with the clinicopathological variables, disease-specific survival (DSS), distant metastasis-free survival (DMFS), and local recurrence-free survival (LRFS). Real-time quantitative polymerase chain reaction (PCR) was used to measure MTAP gene dosage. In some cases, we also performed methylation-specific PCR and pyrosequencing to assess the status of promoter methylation.MTAP deficiency was significantly associated with advanced tumor stages (P = 0.023) and univariately predictive of adverse outcomes for DSS, DMFS, and LRFS. In the multivariate comparison, MTAP deficiency still remained prognostically independent to portend worse DSS (P = 0.021, hazard ratio = 1.870) and DMFS (P = 0.009, hazard ratio = 2.154), together with advanced AJCC stages III to IV. Homozygous deletion or promoter methylation of MTAP gene were identified to be significantly associated with MTAP protein deficiency (P < 0.001).MTAP deficiency was correlated with an aggressive phenotype and independently predictive of worse DSS and DMFS, suggesting its role in disease progression and as an independent prognostic biomarker of NPC, which potentially offers new strategy of targeted treatment for patients lacking MTAP expression.

The Key Role of Calmodulin in KRAS-Driven Adenocarcinomas

KRAS4B is a highly oncogenic splice variant of the KRAS isoform. It is the only isoform associated with initiation of adenocarcinomas. Insight into why and how KRAS4B can mediate ductal adenocarcinomas, particularly of the pancreas, is vastly important for its therapeutics. Here we point out the overlooked critical role of calmodulin (CaM). Calmodulin selectively binds to GTP-bound K-Ras4B; but not to other Ras isoforms. Cell proliferation and growth require the MAPK (Raf/MEK/ERK) and PI3K/Akt pathways. We propose that Ca(2+)/calmodulin promote PI3Kα/Akt signaling, and suggest how. The elevated calcium levels clinically observed in adenocarcinomas may explain calmodulin's involvement in recruiting and stimulating PI3Kα through interaction with its n/cSH2 domains as well as K-Ras4B; importantly, it also explains why K-Ras4B specifically is a key player in ductal carcinomas, such as pancreatic (PDAC), colorectal (CRC), and lung cancers. We hypothesize that calmodulin recruits and helps activate PI3Kα at the membrane, and that this is the likely reason for Ca(2+)/calmodulin dependence in adenocarcinomas. Calmodulin can contribute to initiation/progression of ductal cancers via both PI3Kα/Akt and Raf/MEK/ERK pathways. Blocking the K-Ras4B/MAPK pathway and calmodulin/PI3Kα binding in a K-Ras4B/calmodulin/PI3Kα trimer could be a promising adenocarcinoma-specific therapeutic strategy.

Perspectives in the treatment of pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an incurable lethal disease whose incidence rate is growing. There is no effective screening for detection of early stage tumors and, in most cases, PDAC is diagnosed at advanced disease stages, when radical pancreatic resection is not possible. The aggressive nature of pancreatic tumor cells lies in the complex genetic mechanisms behind their uncontrolled capability to grow and metastasize, which involve essential adaptive changes in cellular metabolism, signaling, adhesion and immunoediting. In addition, PDAC cells promote a dense functional stroma that facilitates tumor resistance to chemotherapy and radiation. During the last two decades, gemcitabine has been the reference for the systemic treatment of PDAC. However, recently, a regimen combining fluorouracil, irinotecan, oxaliplatin, and leucovorin (FOLFIRINOX) and another combining albumin-bound paclitaxel with gemcitabine have shown clear therapeutic advantage in advanced PDAC, with survival outcomes of 11.3 and 8.5 mo on phase III trials, respectively, over single-agent gemcitabine. With the pending issue of their higher toxicities, these regimens set the reference for ongoing and future clinical studies in advanced PDAC. In addition, the efficacy of oral fluoropyrimidine (S-1) has been well documented in Asiatic PDAC patients. The development of therapeutic approaches other than cytotoxic drugs has proven difficult in the past, with only one drug (erlotinib) approved to date. Besides, a number of agents targeting signaling pathways in tumor or stroma cells are being investigated. Likewise, immunotherapies that target PDAC in various ways are the subject of a number of clinical trials. The search for reliable biomarkers with diagnostic and prognostic value using genomics and mass spectrometry methods may facilitate monitoring and refinement of therapies. This review focuses on current understanding of the pathogenesis of PDAC and the latest developments in the treatment of advanced PDAC.

Pancreatic cancer: current understanding of molecular and genetic aetiologies

Pancreatic ductal adenocarcinoma (PDAC) is one of the few cancers where prognosis has not improved over the past few decades. However, there have been several advances in our understanding of the disease leading to earlier detection and targeted therapeutic treatment. It is now understood that specific somatic and germline mutations lead to the development of the disease, and the risk factors associated with this are clearer. Further, several precursor lesions have been identified which, with early detection and surveillance, allows treatment before the development of carcinoma. PDAC can now be diagnosed with a high sensitivity and specificity following advances in radiology, and treatment can be commenced at an earlier stage of the disease. With continued research we are hopeful that the next decade will see an improved survival rate for all patients with pancreatic cancer.

Genetics and Biology of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma remains a clinical challenge. Thus far, enlightenment on the downstream activities of Kras, the tumor's unique metabolic needs, and how the stroma and immune system affect it have remained untranslated to the clinical practice. Given the numbers of diverse therapies in development and a growing knowledge about how to evaluate these systems preclinically and clinically, this is expected to change significantly and for the better over the next 5 years.

Mitochondrial uncoupling protein 2 and pancreatic cancer: A new potential target therapy

Overall 5-years survival of pancreatic cancer patients is nearly 5%, making this cancer type one of the most lethal neoplasia. Furthermore, the incidence rate of pancreatic cancer has a growing trend that determines a constant increase in the number of deceases caused by this pathology. The poor prognosis of pancreatic cancer is mainly caused by delayed diagnosis, early metastasis of tumor, and resistance to almost all tested cytotoxic drugs. In this respect, the identification of novel potential targets for new and efficient therapies should be strongly encouraged in order to improve the clinical management of pancreatic cancer. Some studies have shown that the mitochondrial uncoupling protein 2 (UCP2) is over-expressed in pancreatic cancer as compared to adjacent normal tissues. In addition, recent discoveries established a key role of UCP2 in protecting cancer cells from an excessive production of mitochondrial superoxide ions and in the promotion of cancer cell metabolic reprogramming, including aerobic glycolysis stimulation, promotion of cancer progression. These observations together with the demonstration that UCP2 repression can synergize with standard chemotherapy to inhibit pancreatic cancer cell growth provide the molecular rationale to consider UCP2 as a potential therapeutic target for pancreatic cancer. In this editorial, recent advances describing the relationship between cancer development and mitochondrial UCP2 activity are critically provided.

Cyclin D1, p16(INK) (4A) and p27(Kip1) in pancreatic adenocarcinoma: assessing prognostic implications through quantitative image analysis

The prognostic significance of cyclin D1, p16(INK) (4A) and p27(Kip1) expression has been documented in several human malignancies; however, their prognostic potential in pancreatic adenocarcinoma is still unclear. This study aimed to assess the correlation of the aforementioned molecules with clinicopathological parameters and prognosis. Sixty patients with pancreatic ductal adenocarcinoma underwent surgical resection at a single institution; immunohistochemical staining of the studied markers was quantified by Ιmage analysis system. Cyclin D1 overexpression was positively associated with grade, neural infiltration and vascular invasion, whereas p27 positively correlated with age. Higher cyclin D1 expression indicated poorer survival (adjusted HR = 9.75, 95%CI: 1.48-64.31, p = 0.018, increment: one unit in H-score), whereas a marginal trend toward an association between p16 positivity and improved survival was observed (adjusted HR = 0.58, 95%CI: 0.32-1.05, p = 0.072 regarding positive vs negative cases). No significant association with overall survival was noted regarding p27. In conclusion, cyclin D1 overexpression and possibly p16 loss of expression in pancreatic adenocarcinoma seem to be adverse prognostic factors, whereas p27 expression did not seem to possess such prognostic properties. Further validation of the present findings in studies encompassing larger samples seems to be needed.

Genetic polymorphisms in the 9p21 region associated with risk of multiple cancers

The chromosome 9p21 region has been implicated in the pathogenesis of multiple cancers. We analyzed 9p21 single nucleotide polymorphisms (SNPs) from eight genome-wide association studies (GWAS) with data deposited in dbGaP, including studies of esophageal squamous cell carcinoma (ESCC), gastric cancer (GC), pancreatic cancer, renal cell carcinoma (RCC), lung cancer (LC), breast cancer (BrC), bladder cancer (BC) and prostate cancer (PrC). The number of subjects ranged from 2252 (PrC) to 7619 (LC). SNP-level analyses for each cancer were conducted by logistic regression or random-effects meta-analysis. A subset-based statistical approach (ASSET) was performed to combine SNP-level P values across multiple cancers. We calculated gene-level P values using the adaptive rank truncated product method. We identified that rs1063192 and rs2157719 in the CDKN2A/2B region were significantly associated with ESCC and rs2764736 (3' of TUSC1) was associated with BC (P ≤ 2.59 × 10(-6)). ASSET analyses identified four SNPs significantly associated with multiple cancers: rs3731239 (CDKN2A intronic) with ESCC, GC and BC (P = 3.96 × 10(-) (4)); rs10811474 (3' of IFNW1) with RCC and BrC (P = 0.001); rs12683422 (LINGO2 intronic) with RCC and BC (P = 5.93 × 10(-) (4)) and rs10511729 (3' of ELAVL2) with LC and BrC (P = 8.63 × 10(-) (4)). At gene level, CDKN2B, CDKN2A and CDKN2B-AS1 were significantly associated with ESCC (P ≤ 4.70 × 10(-) (5)). Rs10511729 and rs10811474 were associated with cis-expression of 9p21 genes in corresponding cancer tissues in the expression quantitative trait loci analysis. In conclusion, we identified several genetic variants in the 9p21 region associated with the risk of multiple cancers, suggesting that this region may contribute to a shared susceptibility across different cancer types.

Expression and clinical significance of IMP3 in microdissected premalignant and malignant pancreatic lesions

INTRODUCTION

Insulin-like growth factor 2 (IGF-2) mRNA-binding protein 3 (IMP3) is overexpressed in pancreatic cancer, while remaining undetectable in the normal pancreas, indicating its important role in pancreatic cancer pathogenesis. The role of IMP3 in pancreatic carcinogenesis has not been fully understood. The main goal of this study was to probe the expression profile of IMP3 in different stages of pancreatic ductal adenocarcinoma (PDAC) development, and evaluate their prognostic significance in PDAC patients.

MATERIALS AND METHODS

We used quantitative real-time RT-PCR combined manual microdissection to precisely detect IMP3 expression in 97 microdissected foci from 50 patients with PDAC. Nonparametric test, Log-rank test and Cox regression analysis were used to evaluate the clinical significance of DNMTs expression.

RESULTS

Expression of IMP3 increased from normal duct to pancreatic intraductal neoplasia and to PDAC. IMP3 mRNA expression statistically correlated with TNM staging. Univariate analysis showed that high level of IMP3 expression, tumor differentiation, TNM staging and alcohol consumption were statistically significant risk factors. Multivariate analysis showed that high level of IMP3 expression and tumor differentiation were statistically significant independent poor prognostic factors.

CONCLUSIONS

These results suggested that pancreatic carcinogenesis involves an increased IMP3 mRNA expression, and it may become valuable diagnostic and prognostic markers as well as potential therapeutic targets for pancreatic cancer.

Molecular biology of pancreatic ductal adenocarcinoma

PURPOSE OF REVIEW

Recent advances in sequencing technology have led to a deeper and more comprehensive understanding of the molecular biology of pancreatic ductal adenocarcinoma. This timely review seeks to summarize these recent advances which will provide a foundation for future studies in the field.

RECENT FINDINGS

Stereotypical genetic alterations have been identified and confirmed. However, additional alterations have highlighted the importance and complexity of a number of intracellular signaling pathways that present unique opportunities for therapeutic targeting.

SUMMARY

A genetic signature of pancreatic ductal adenocarcinoma has been identified. This recent and important work is currently in the process of being applied in many clinical applications from early diagnostics to customized therapeutic regimens for this disease. A fundamental understanding of these findings will thus be of utmost importance for future research in the field and in the clinical care of patients with this lethal disease.

The Mdm network and its regulation of p53 activities: a rheostat of cancer risk

The potent transcriptional activity of p53 (Trp53, TP53) must be kept in check for normal cell growth and survival. Tumors, which drastically deviate from these parameters, have evolved multiple mechanisms to inactivate TP53, the most prevalent of which is the emergence of TP53 missense mutations, some of which have gain-of-function activities. Another important mechanism by which tumors bypass TP53 functions is via increased levels of two TP53 inhibitors, MDM2, and MDM4. Studies in humans and in mice reveal the complexity of TP53 regulation and the exquisite sensitivity of this pathway to small changes in regulation. Here, we summarize the factors that impinge on TP53 activity and thus cell death/arrest or tumor development.

Sweating the small stuff: microRNAs and genetic changes define pancreatic cancer

MicroRNAs (miRNAs) are 18- to 22-nucleotide-long, single-stranded, noncoding RNAs that regulate important biological processes including differentiation, proliferation, and response to cellular stressors such as hypoxia, nutrient depletion, and traversion of the cell cycle by controlling protein expression within the cell. Many investigators have profiled cancer tissue and serum miRNAs to identify potential therapeutic targets, understand the pathways involved in tumorigenesis, and identify diagnostic tumor signatures. In the setting of pancreatic cancer, obtaining pancreatic tissue is invasive and impractical for early diagnosis. Several groups have profiled miRNAs that are present in the blood as a means to diagnose tumor progression and predict prognosis/survival or drug resistance. Several miRNA signatures found in pancreatic tissue and the peripheral blood, as well as the pathways that are associated with pancreatic cancer, are reviewed here in detail. Three miRNA biomarkers (miR-21, miR-155, and miR-200) have been repetitively identified in both pancreatic cancer tissue and patients' blood. Those miRNAs regulate and are regulated by the central genetic and epigenetic changes observed in pancreatic cancer including p53, transforming growth factor β, p16(INK4A), BRCA1/2, and Kras. These miRNAs are involved in DNA repair, cell cycle, and cell invasion and also play important roles in promoting metastases.

Common genetic variants in the 9p21 region and their associations with multiple tumours

BACKGROUND

The chromosome 9p21.3 region has been implicated in the pathogenesis of multiple cancers.

METHODS

We systematically examined up to 203 tagging SNPs of 22 genes on 9p21.3 (19.9-32.8 Mb) in eight case-control studies: thyroid cancer, endometrial cancer (EC), renal cell carcinoma, colorectal cancer (CRC), colorectal adenoma (CA), oesophageal squamous cell carcinoma (ESCC), gastric cardia adenocarcinoma and osteosarcoma (OS). We used logistic regression to perform single SNP analyses for each study separately, adjusting for study-specific covariates. We combined SNP results across studies by fixed-effect meta-analyses and a newly developed subset-based statistical approach (ASSET). Gene-based P-values were obtained by the minP method using the Adaptive Rank Truncated Product program. We adjusted for multiple comparisons by Bonferroni correction.

RESULTS

Rs3731239 in cyclin-dependent kinase inhibitors 2A (CDKN2A) was significantly associated with ESCC (P=7 × 10(-6)). The CDKN2A-ESCC association was further supported by gene-based analyses (Pgene=0.0001). In the meta-analyses by ASSET, four SNPs (rs3731239 in CDKN2A, rs615552 and rs573687 in CDKN2B and rs564398 in CDKN2BAS) showed significant associations with ESCC and EC (P<2.46 × 10(-4)). One SNP in MTAP (methylthioadenosine phosphorylase) (rs7023329) that was previously associated with melanoma and nevi in multiple genome-wide association studies was associated with CRC, CA and OS by ASSET (P=0.007).

CONCLUSION

Our data indicate that genetic variants in CDKN2A, and possibly nearby genes, may be associated with ESCC and several other tumours, further highlighting the importance of 9p21.3 genetic variants in carcinogenesis.

Deciphering the mechanisms of tumorigenesis in human pancreatic ductal epithelial cells

PURPOSE

The most common genetic lesions in pancreatic ductal adenocarcinoma (PDAC) have been identified. However, significant gaps still exist in our understanding of how such genetic alterations act in concert to induce PDAC development. In this study, we investigated the mechanism of tumorigenic transformation in the immortalized human pancreatic ductal epithelial (HPDE) cell line by sequentially introducing PDAC signature alterations into this cell line.

EXPERIMENTAL DESIGN

The phenotype for stable expression of mutant K-ras, Her2, p16/p14shRNA, and Smad4shRNA in HPDE cells was examined by assays for cell proliferation, migration, invasion, soft agar, and orthotopic tumorigenesis. The mechanisms of tumorigenic transformation were further explored by gene expression profiling and pathway analyses.

RESULTS

The transformed cells exhibited enhanced proliferation, migration, and invasion, displayed anchorage-independent growth in soft agar, and grew orthotopic tumors with some histopathologic features of PDAC. We found that Smad4 played key roles in the tumorigenic transformation of HPDE cells. We further found that MDM2 and Bmi-1 were overexpressed in the tumorigenic HPDE cells and that Bmi-1 overexpression was regulated by Smad4. Ingenuity Pathway Analysis software analysis of microarray data revealed that dysregulation of integrin-linked kinase signaling and the cell cycle were the most significant changes involved in tumorigenic transformation. Altogether, this cell culture model closely recapitulated human pancreatic carcinogenesis from gene lesions, activation of specific signaling pathways, and some histopathologic features.

CONCLUSION

The combination of activated K-ras and Her2 with inactivated p16/p14 and Smad4 was sufficient and essential to transform HPDE cells, thus revealing the potential tumorigenic mechanism.

Molecular markers in pancreatic cancer diagnosis

Pancreatic ductal adenocarcinoma (PDAC) represents a fatal neoplasia with a high mortality rate. Effective early detection methods are needed since this is the best way to cure this disease. During the last several years, many investigations focused on determining relevant biomarkers that may be present during early stages of pancreatic tumor development. Although several biomarkers have been proposed for pancreatic cancer detection, the clinical applicability has been confusing. Currently, although CA19-9 is one test used, the sensitivity and specificity for the disease are less than optimal. Here, we review several new potential serum, plasma and stool markers that are currently under evaluation. Although these have not been sufficiently validated for routine clinical use, these markers could prove valuable with further investigations. We keep the hope that a combination of some of these novel biomarkers can be a useful tool for early PDAC diagnosis before image techniques and/or patient's symptoms reveal disease in an incurable state.

Study human pancreatic cancer in mice: how close are they?

Pancreatic cancer is the fourth leading cause of cancer deaths and is characterized by dismal prognosis. Xenograft and genetically engineered mouse (GEM) models have recapitulated critical elements of human pancreatic cancer, providing useful tools to probe the underlying cause of cancer etiology. In this review, we provide a brief description of the common genetic lesions that occur during the development of pancreatic cancer. Next, we describe the strengths and weaknesses of these two models and highlight key discoveries each has made. Although the relative merits of GEM and xenograft pancreatic cancer mouse models are subject to debate, both systems have and will continue to yield essential insights in understanding pancreatic cancer etiology. This information is critical for the development of new methods to screen, treat, and prevent pancreatic cancer.

A review of methionine dependency and the role of methionine restriction in cancer growth control and life-span extension

Methionine is an essential amino acid with many key roles in mammalian metabolism such as protein synthesis, methylation of DNA and polyamine synthesis. Restriction of methionine may be an important strategy in cancer growth control particularly in cancers that exhibit dependence on methionine for survival and proliferation. Methionine dependence in cancer may be due to one or a combination of deletions, polymorphisms or alterations in expression of genes in the methionine de novo and salvage pathways. Cancer cells with these defects are unable to regenerate methionine via these pathways. Defects in the metabolism of folate may also contribute to the methionine dependence phenotype in cancer. Selective killing of methionine dependent cancer cells in co-culture with normal cells has been demonstrated using culture media deficient in methionine. Several animal studies utilizing a methionine restricted diet have reported inhibition of cancer growth and extension of a healthy life-span. In humans, vegan diets, which can be low in methionine, may prove to be a useful nutritional strategy in cancer growth control. The development of methioninase which depletes circulating levels of methionine may be another useful strategy in limiting cancer growth. The application of nutritional methionine restriction and methioninase in combination with chemotherapeutic regimens is the current focus of clinical studies.

Association of increased DNA methyltransferase expression with carcinogenesis and poor prognosis in pancreatic ductal adenocarcinoma

INTRODUCTION

Epigenetic modifications play an important role in multistage carcinogenesis. The role of the three functional DNA methyltransferases (DNMTs) in pancreatic carcinogenesis has not been fully understood. The main goal of this study was to examine DNMT expression in different stages of pancreatic ductal adenocarcinoma (PDAC), and evaluate their prognostic significance in PDAC.

MATERIALS AND METHODS

A large number of premalignant and malignant pancreatic lesions were obtained by manual microdissection. Quantitative real-time RT-PCR was used to detect DNMTs mRNA expression. Nonparametric test, logrank test and Cox regression analysis were used to evaluate the clinical significance of DNMT expression.

RESULTS

The mRNA expression of the three DNMTs increased with the development of pancreatic cancer from normal duct to pancreatic intraductal neoplasia and further to PDAC, and were statistically correlated with each other. Expression of the three DNMTs was statistically correlated with TNM staging and history of chronic pancreatitis. DNMT3A and DNMT3B, but not DNMT1 expression, was statistically correlated with tumour size. Patients with higher levels of DNMT1, DNMT3A and/or DNMT3B expression had an overall lower survival than those with lower levels of expression. Univariate analysis showed that high expression levels of DNMTs, alcohol consumption, tumour differentiation and TNM staging were statistically significant risk factors. Multivariate analysis showed that high level of DNMT3B expression and tumour differentiation were statistically significant independent poor prognostic factors.

CONCLUSIONS

These results suggested that pancreatic carcinogenesis involves an increased mRNA expression of three DNMTs, and they may become valuable diagnostic and prognostic markers as well as potential therapeutic targets for pancreatic cancer.