Werner syndrome as a hereditary risk factor for exocrine pancreatic cancer: potential role of WRN in pancreatic tumorigenesis and patient-tailored therapy

The Expression Characteristics and Function of the RECQ Family in Pan-Cancer

BACKGROUND

The genes of the RECQ DNA helicase family play a part in preserving the stability of the genome and controlling different disease mechanisms. However, the expression features of RECQs in relation to pan-cancer, their correlation with the immune microenvironment of tumors, and the landscape of prognostic power are still undisclosed.

METHODS

Various sequence and clinical data extracted from 33 cancers were utilized to generate a comprehensive overview of RECQs in the landscape. Afterward, we discovered variations in gene expression, potential enrichment of functions, genetic alterations, and analysis related to the immune response in tumors. Additionally, we explored the clinical characteristics and diagnostic significance of RECQs. And the important association of RECQL4 with liver hepatocellular carcinoma (LIHC) was investigated.

RESULTS

RECQs exhibited extensive mutations in different types of cancers. The expression of RECQ may be influenced by an oncogenic mutation in certain types of cancer, resulting in the observed genomic and epigenetic changes in diverse tumor formations. Furthermore, RECQs originating from tumors exhibited a significant association with the immune microenvironment of the tumor, indicating their potential as promising targets for therapy. Patient prognosis was significantly associated with the majority of genes in the RECQ family. In LIHC, RECQL4 eventually emerged as a separate prognostic determinant.

CONCLUSIONS

To summarize, RECQs are essential for the regulation of the immune system in tumors, and RECQL4 serves as a prognostic indicator in LIHC. The results of our study offer fresh perspectives on RECQs from a bioinformatics perspective and emphasize the importance of RECQs in the diagnosis and treatment of cancer.

Current status of inherited pancreatic cancer

Background

It is estimated that about 10% of pancreatic cancer cases have a genetic background. People with a familial predisposition to pancreatic cancer can be divided into 2 groups. The first is termed hereditary pancreatic cancer, which occurs in individuals with a known hereditary cancer syndrome caused by germline single gene mutations (e.g., BRCA1/2, CDKN2A). The second is considered as familial pancreatic cancer, which is associated with several genetic factors responsible for the more common development of pancreatic cancer in certain families, but the precise single gene mutation has not been found.

Aim

This review summarizes the current state of knowledge regarding the risk of pancreatic cancer development in hereditary pancreatic cancer and familial pancreatic cancer patients. Furthermore, it gathers the latest recommendations from the three major organizations dealing with the prevention of pancreatic cancer in high-risk groups and explores recent guidelines of scientific societies on screening for pancreatic cancers in individuals at risk for hereditary or familial pancreatic cancer.

Conclusions

In order to improve patients’ outcomes, authors of current guidelines recommend early and intensive screening in patients with pancreatic cancer resulting from genetic background. The screening should be performed in excellence centers. The scope, extent and cost-effectiveness of such interventions requires further studies.

WRN Germline Mutation Is the Likely Inherited Etiology of Various Cancer Types in One Iranian Family

Background

Familial cancers comprise a considerable distribution of colorectal cancers (CRCs), of which only about 5% occurs through well-established hereditary syndromes. It has been demonstrated that deleterious variants at the newly identified cancer-predisposing genes could describe the etiology of undefined familial cancers.

Methods

The present study aimed to identify the genetic etiology in a 32-year-old man with early onset familial CRC employing several molecular diagnostic techniques. DNA was extracted from tumoral and normal formalin-fixed-paraffin-embedded (FFPE) blocks, and microsatellite instability (MSI) was evaluated. Immunohistochemistry staining of MMR proteins was performed on tumoral FFPE blocks. Next-generation sequencing (NGS), multiplex ligation-dependent amplification (MLPA) assay, and Sanger sequencing were applied on the genomic DNA extracted from peripheral blood. Data analysis was performed using bioinformatics tools. Genetic variants interpretation was based on ACMG.

Results

MSI analysis indicated MSI-H phenotype, and IHC staining proved no expressions of MSH2 and MSH6 proteins. MLPA and NGS data showed no pathogenic variants in MMR genes. Further analysis of NGS data revealed a candidate WRN frameshift variant (p.R389Efs*3), which was validated with Sanger sequencing. The variant was interpreted as pathogenic since it met the criteria based on the ACMG guideline including very strong (PVS1), strong (PS3), and moderate (PM2).

Conclusion

WRN is a DNA helicase participating in DNA repair pathways to sustain genomic stability. WRN deficient function may contribute to CRC development that is valuable for further investigation as a candidate gene in hereditary cancer syndrome diagnosis.

Werner Syndrome Protein Expression in Breast Cancer

INTRODUCTION

Werner protein (WRN) plays an important role in DNA repair, replication, transcription, and consequently genomic stability via its DNA-helicase and exonuclease activity. Loss of function of WRN is associated with Werner syndrome (WS), which is characterized by premature aging and cancer predisposition. Malignancies that are commonly linked to WS are thyroid carcinoma, melanoma, breast cancer, meningioma, and soft tissue and bone sarcomas. Currently, the clinicopathologic significance of WRN in breast cancer is largely unknown.

PATIENTS AND METHODS

We investigated the clinicopathologic and prognostic significance of WRN protein expression in a cohort of clinically annotated series of sporadic (n = 1650) and BRCA-mutated (n = 75) invasive breast cancers. We correlated WRN protein expression to clinicopathologic characteristics, DNA repair protein expression, and survival outcomes.

RESULTS

There is strong evidence of association between low nuclear and cytoplasmic WRN co-expression and low levels of KU70/KU80, DNA-PK, DNA Pol-B, CKD18, cytoplasmic RECQL4, and nuclear BLM protein expression (adjusted P-values < .05). Tumors with low nuclear or cytoplasmic WRN expression have worse overall breast cancer-specific survival (BCSS) (adjusted P-values < .05). In topoisomerase I overexpressed tumors, low WRN nuclear expression was associated with poor BCSS (P-value < .05). In BRCA-mutated tumors, low WRN cytoplasmic expression conferred shortest BCSS (P < .05).

CONCLUSIONS

Low WRN protein expression is associated with poor BCSS in patients with breast cancer. This can be used to optimize the risk stratification for personalized treatment.

High frequency of pathogenic germline variants within homologous recombination repair in patients with advanced cancer

Genomic screening of cancer patients for predisposing variants is traditionally based on age at onset, family history and type of cancer. Whereas the clinical guidelines have proven efficient in identifying families exhibiting classical attributes of hereditary cancer, the frequency of patients with alternative presentations is unclear. We identified and characterized germline variants in 636 patients with advanced solid cancer using whole exome sequencing. Pathogenic and likely pathogenic germline variants among 168 genes associated with hereditary cancer were considered. These variants were identified in 17.8% of the patients and within a wide range of cancer types. In particular, patients with mesothelioma, ovarian cancer, cervical cancer, urothelial cancer, and cancer of unknown primary origin displayed high frequencies of pathogenic variants. Variants were predominantly found in DNA-repair pathways and about half were within genes involved in homologous recombination repair. Twenty-two BRCA1 and BRCA2 germline variants were identified in 12 different cancer types, of which 10 (45%) were not previously identified in these patients based on the current clinical guidelines. Loss of heterozygosity and somatic second hits were identified in several of the affected genes, supporting possible causality for cancer development. A potential treatment target based on the pathogenic germline variant could be suggested in 25 patients (4%). The study demonstrates a high frequency of pathogenic germline variants in the homologous recombination pathway in patients with advanced solid cancers. We infer that genetic screening in this group of patients may reveal high-risk families and identify patients with potential PARP inhibitor sensitive tumors.

Camptothecin targets WRN protein: mechanism and relevance in clinical breast cancer

Werner syndrome protein (WRN) is a RecQ helicase that participates in DNA repair, genome stability and cellular senescence. The five human RecQ helicases, RECQL1, Bloom, WRN, RECQL4 and RECQL5 play critical roles in DNA repair and cell survival after treatment with the anticancer drug camptothecin (CPT). CPT derivatives are widely used in cancer chemotherapy to inhibit topoisomerase I and generate DNA double-strand breaks during replication. Here we studied the effects of CPT on the stability and expression dynamics of human RecQ helicases. In the cells treated with CPT, we observed distinct effects on WRN compared to other human RecQ helicases. CPT altered the cellular localization of WRN and induced its degradation by a ubiquitin-mediated proteasome pathway. WRN knockdown cells as well as CPT treated cells became senescent and stained positive for senescence-associated β-galactosidase at a higher frequency compared to control cells. However, the senescent phenotype was attenuated by ectopic expression of WRN suggesting functional implication of WRN degradation in CPT treated cells. Approximately 5-23% of breast cancer tumors are known to respond to CPT-based chemotherapy. Interestingly, we found that the extent of CPT-induced WRN degradation correlates with increasing sensitivity of breast cancer cells to CPT. The abundance of WRN decreased in CPT-treated sensitive cells; however, WRN remained relatively stable in CPT-resistant breast cancer cells. In a large clinical cohort of breast cancer patients, we find that WRN and topoisomerase I expression correlate with an aggressive tumor phenotype and poor prognosis. Our novel observations suggest that WRN abundance along with CPT-induced degradation could be a promising strategy for personalizing CPT-based cancer chemotherapeutic regimens.

Familial pancreatic cancer: Concept, management and issues

Familial pancreatic cancer (FPC) is broadly defined as two first-degree-relatives with pancreatic cancer (PC) and accounts for 4%-10% of PC. Several genetic syndromes, including Peutz-Jeghers syndrome, hereditary pancreatitis, hereditary breast-ovarian cancer syndrome (HBOC), Lynch syndrome, and familial adenomatous polyposis (FAP), also have increased risks of PC, but the narrowest definition of FPC excludes these known syndromes. When compared with other familial tumors, proven genetic alterations are limited to a small proportion (< 20%) and the familial aggregation is usually modest. However, an ethnic deviation (Ashkenazi Jewish > Caucasian) and a younger onset are common also in FPC. In European countries, “anticipation” is reported in FPC families, as with other hereditary syndromes; a trend toward younger age and worse prognosis is recognized in the late years. The resected pancreases of FPC kindred often show multiple pancreatic intraepithelial neoplasia (PanIN) foci, with various K-ras mutations, similar to colorectal polyposis seen in the FAP patients. As with HBOC patients, a patient who is a BRCA mutation carrier with unresectable pancreatic cancer (accounting for 0%-19% of FPC patients) demonstrated better outcome following platinum and Poly (ADP-ribose) polymerase inhibitor treatment. Western countries have established FPC registries since the 1990s and several surveillance projects for high-risk individuals are now ongoing to detect early PCs. Improvement in lifestyle habits, including non-smoking, is recommended for individuals at risk. In Japan, the FPC study group was initiated in 2013 and the Japanese FPC registry was established in 2014 by the Japan Pancreas Society.

Syndrome-Associated Tumors by Organ System

Certain tumors suggest the possibility of a patient harboring a genetic syndrome, particularly in children. Syndrome-associated tumors of the gastrointestinal tract, genitourinary tract, gynecologic tract, heart, lungs, brain, eye, endocrine organs, and hematopoietic system will be briefly discussed.

Aberrant over-expression of TRPM7 ion channels in pancreatic cancer: required for cancer cell invasion and implicated in tumor growth and metastasis

Our previous studies in zebrafish development have led to identification of the novel roles of the transient receptor potential melastatin-subfamily member 7 (TRPM7) ion channels in human pancreatic cancer. However, the biological significance of TRPM7 channels in pancreatic neoplasms was mostly unexplored. In this study, we determined the expression levels of TRPM7 in pancreatic tissue microarrays and correlated these measurements in pancreatic adenocarcinoma with the clinicopathological features. We also investigated the role of TRPM7 channels in pancreatic cancer cell invasion using the Matrigel(TM)-coated transwell assay. In normal pancreas, TRPM7 is expressed at a discernable level in the ductal cells and centroacinar cells and at a relatively high level in the islet endocrine cells. In chronic pancreatitis, pre-malignant tissues, and malignant neoplasms, there is variable expression of TRPM7. In the majority of pancreatic adenocarcinoma specimens examined, TRPM7 is expressed at either moderate-level or high-level. Anti-TRPM7 immunoreactivity in pancreatic adenocarcinoma significantly correlates with the size and stages of tumors. In human pancreatic adenocarcinoma cells in which TRPM7 is highly expressed, short hairpin RNA-mediated suppression of TRPM7 impairs cell invasion. The results demonstrate that TRPM7 channels are over-expressed in a proportion of the pre-malignant lesions and malignant tumors of the pancreas, and they are necessary for invasion by pancreatic cancer cells. We propose that TRPM7 channels play important roles in development and progression of pancreatic neoplasm, and they may be explored as clinical biomarkers and targets for its prevention and treatment.

Cellular deficiency of Werner syndrome protein or RECQ1 promotes genotoxic potential of hydroquinone and benzo[a]pyrene exposure

The 5 known RecQ helicases in humans (RECQ1, BLM, WRN, RECQL4, and RECQ5) have demonstrated roles in diverse genome maintenance mechanisms but their functions in safeguarding the genome from environmental toxicants are poorly understood. Here, we have evaluated a potential role of WRN (mutated in Werner syndrome) and RECQ1 (the most abundant homolog of WRN) in hydroquinone (HQ)- and benzo[a]pyrene (BaP)-induced genotoxicity. Silencing of WRN or RECQ1 expression in HeLa cells increased their sensitivity to HQ and BaP but elicited distinct DNA damage response. The RECQ1-depleted cells exhibited increased replication protein A phosphorylation, Chk1 activation, and DNA double-strand breaks (DSBs) as compared to control or WRN-depleted cells following exposure to BaP treatment. The BaP-induced DSBs in RECQ1-depleted cells were dependent on DNA-dependent protein kinase activity. Notably, loss of WRN in RECQ1-depleted cells ameliorated BaP toxicity. Collectively, our results provide first indication of nonredundant participation of WRN and RECQ1 in protection from the potentially carcinogenic effects of BaP and HQ.

Translating discovery in zebrafish pancreatic development to human pancreatic cancer: biomarkers, targets, pathogenesis, and therapeutics

Abstract Experimental studies in the zebrafish have greatly facilitated understanding of genetic regulation of the early developmental events in the pancreas. Various approaches using forward and reverse genetics, chemical genetics, and transgenesis in zebrafish have demonstrated generally conserved regulatory roles of mammalian genes and discovered novel genetic pathways in exocrine pancreatic development. Accumulating evidence has supported the use of zebrafish as a model of human malignant diseases, including pancreatic cancer. Studies have shown that the genetic regulators of exocrine pancreatic development in zebrafish can be translated into potential clinical biomarkers and therapeutic targets in human pancreatic adenocarcinoma. Transgenic zebrafish expressing oncogenic K-ras and zebrafish tumor xenograft model have emerged as valuable tools for dissecting the pathogenetic mechanisms of pancreatic cancer and for drug discovery and toxicology. Future analysis of the pancreas in zebrafish will continue to advance understanding of the genetic regulation and biological mechanisms during organogenesis. Results of those studies are expected to provide new insights into how aberrant developmental pathways contribute to formation and growth of pancreatic neoplasia, and hopefully generate valid biomarkers and targets as well as effective and safe therapeutics in pancreatic cancer.

Toward the goal of personalized therapy in pancreatic cancer by targeting the molecular phenotype

The purpose of this article is to provide a critical review of the molecular alterations in pancreatic cancer that are clinically investigated as therapeutic targets and their potential impact on clinical outcomes. Adenocarcinoma of exocrine pancreas is generally associated with poor prognosis and the conventional therapies are marginally effective. Advances in understanding the genetic regulation of normal and neoplastic development of pancreas have led to development and clinical evaluation of new therapeutic strategies that target the signaling pathways and molecular alterations in pancreatic cancer. Applications have begun to utilize the genetic targets as biomarkers for prediction of therapeutic responses and selection of treatment options. The goal of accomplishing personalized tumor-specific therapy with tolerable side effects for patients with pancreatic cancer is hopefully within reach in the foreseeable future.

TRPM7 and TRPM8 Ion Channels in Pancreatic Adenocarcinoma: Potential Roles as Cancer Biomarkers and Targets

Transient receptor potential (TRP) ion channels are essential for normal functions and health by acting as molecular sensors and transducing various stimuli into cellular and physiological responses. Growing evidence has revealed that TRP ion channels play important roles in a wide range of human diseases, including malignancies. In light of recent discoveries, it has been found that TRP melastatin-subfamily members, TRPM7 and TRPM8, are required for normal and cancerous development of exocrine pancreas. We are currently investigating the mechanisms which mediate the functional roles of TRPM7 and TRPM8 and attempting to develop these ion channels as clinical biomarkers and therapeutic targets for achieving the goal of personalized therapy in pancreatic cancer.

TRPM8 ion channel is aberrantly expressed and required for preventing replicative senescence in pancreatic adenocarcinoma: potential role of TRPM8 as a biomarker and target

Pancreatic adenocarcinoma is mostly fatal and generally resistant to conventional treatments, such that effective therapies with tolerable side effects are desperately needed. Ion channels including the transient receptor potential (TRP) channels have been implicated in human malignancies, but their roles in pancreatic cancer were mostly unknown. Recent identification of the melastatin-subfamily members of the TRP family of ion channels, and their functions in pancreatic epithelia and adenocarcinoma, is expected to provide a new perspective to understanding the mechanism underlying pancreatic tumorigenesis. In this report, we present the clinical and pathological features of a mini-series of patients with pancreatic adenocarcinoma, which aberrantly exhibits immunoreactivity against the TRPM8 channel. We have recently demonstrated the proliferative role of TRPM8 channel in pancreatic cancer cells. Here, we present evidence that RNA interference-mediated silencing of TRPM8 induces replicative senescence in pancreatic adenocarcinoma cells. This suggests that the aberrantly expressed TRPM8 channel may contribute to pancreatic tumorigenesis by preventing oncogene-induced senescence, and targeted inhibition of TRPM8 may enhance tumor sensitivity to therapeutics. Based on these observations, we hypothesize that the TRPM8 ion channel plays a crucial role in the growth and progression of pancreatic neoplasia during tumorigenesis. We propose that TRPM8 can be exploited as a clinical biomarker and as a therapeutic target for developing personalized therapy in pancreatic adenocarcinoma.

Targeted silencing of TRPM7 ion channel induces replicative senescence and produces enhanced cytotoxicity with gemcitabine in pancreatic adenocarcinoma

The transient receptor potential TRPM7 ion channel is required for cellular proliferation in pancreatic epithelia and adenocarcinoma. To elucidate the mechanism that mediates the function of TRPM7, we examined its role in survival of pancreatic cancer cells. RNA interference-mediated silencing of TRPM7 did not induce apoptotic cell death. TRPM7-deficient cells underwent replicative senescence with up-regulation of p16(CDKN2A) and WRN mRNA. The combination of anti-TRPM7 siRNA and gemcitabine produced enhanced cytotoxicity as compared to gemcitabine alone. Thus, TRPM7 is required for preventing senescence, and modulation of TRPM7 expression may help improve treatment response of pancreatic cancer by combining with apoptosis-inducing agents.

The Werner's Syndrome RecQ helicase/exonuclease at the nexus of cancer and aging

Werner's Syndrome (WS) or adult-onset progeria is an autosomal recessive disorder of accelerated aging caused by mutations of the DNA RecQ helicase/exonuclease (WRN). WRN is an ATP-dependent helicase with 3' to 5' DNA exonuclease activity that regulates the replicative potential of dividing cells, and WRN loss-of-function mutations promote cellular senescence and neoplastic transformation. These molecular findings translate clinically into adult-onset progeria manifested by premature hair graying, dermal atrophy, cardiovascular disease, and cancer predilection along with a markedly reduced life expectancy. Recently, a patient with WS who developed pancreatic adenocarcinoma was identified in Honolulu suggesting a significant prevalence of loss-of-function WRN mutations in Hawaii's Japanese-American population. Based upon the indigenous Japanese WRN loss-of-function mutation heterozygote rate of 6 per 1,000, we speculate the possibility of approximately 1,200 heterozygotes in Hawaii. Our ongoing studies aim to evaluate Hawaii's true allelic prevalence of WRN loss-of-function mutations in the Japanese-American population, and the role of WRN silencing in sporadic cancers. In summary, WRN plays a nexus-like role in the complex interplay of cellular events that regulate aging, and analysis of WRN polymorphisms in Hawaii's population will generate novel insights to advance care for age-related pathologies.