Single nucleotide polymorphism in RECQL and survival in resectable pancreatic adenocarcinoma

Prevalence of RECQL germline variants in Pakistani early-onset and familial breast cancer patients

Background

The RecQ Like Helicase (RECQL) gene has previously been shown to predispose to breast cancer mainly in European populations, in particular to estrogen receptor (ER) and/or progesterone receptor (PR) positive tumor. Here, we investigated the contribution of pathogenic RECQL germline variants to hereditary breast cancer in early-onset and familial breast cancer patients from Pakistan.

Methods

Comprehensive RECQL variant analysis was performed in 302 BRCA1 and BRCA2 negative patients with ER and/or PR positive breast tumors using denaturing high-performance liquid chromatography followed by DNA sequencing. Novel variants were classified using Sherloc guidelines.

Results

One novel pathogenic protein-truncating variant (p.W75*) was identified in a 37-year-old familial breast cancer patient. The pathogenic variant frequencies were 0.3% (1/302) in early-onset and familial breast cancer patients and 0.8% (1/133) in familial patients. Further, three novel variants of unknown significance, p.I141F, p.S182S, and p.C475C, were identified in familial breast cancer patients at the age of 47, 68, and 47 respectively. All variants were absent in 250 controls.

Conclusions

Our data suggest that the RECQL gene plays a negligible role in breast cancer predisposition in Pakistan.

DNA helicases and their roles in cancer

DNA helicases, known for their fundamentally important roles in genomic stability, are high profile players in cancer. Not only are there monogenic helicase disorders with a strong disposition to cancer, it is well appreciated that helicase variants are associated with specific cancers (e.g., breast cancer). Flipping the coin, DNA helicases are frequently overexpressed in cancerous tissues and reduction in helicase gene expression results in reduced proliferation and growth capacity, as well as DNA damage induction and apoptosis of cancer cells. The seminal roles of helicases in the DNA damage and replication stress responses, as well as DNA repair pathways, validate their vital importance in cancer biology and suggest their potential values as targets in anti-cancer therapy. In recent years, many laboratories have characterized the specialized roles of helicase to resolve transcription-replication conflicts, maintain telomeres, mediate cell cycle checkpoints, remodel stalled replication forks, and regulate transcription. In vivo models, particularly mice, have been used to interrogate helicase function and serve as a bridge for preclinical studies that may lead to novel therapeutic approaches. In this review, we will summarize our current knowledge of DNA helicases and their roles in cancer, emphasizing the latest developments.

A Qualitative Review of Neoadjuvant Chemotherapy in Resectable Pancreatic Adenocarcinoma

The aim of this study was to evaluate outcomes of patients with resectable pancreatic adenocarcinoma (PDAC) who underwent neoadjuvant chemotherapy. The MEDLINE and PubMed databases were searched to identify relevant original articles investigating neoadjuvant therapy in resectable PDAC. Qualitative analyses were performed to investigate patient selection, disease stage, impact on perioperative outcomes, and cost-effectiveness. Forty-three studies met inclusion criteria for this review. Neoadjuvant chemotherapy for upfront resectable PDAC is cost-effective, safe, may result in lower stage disease and has potential survival advantages. With proper patient selection, neoadjuvant chemotherapy is an appropriate approach for upfront resectable PDAC. Nevertheless, the risk for disease progression and losing a curative surgical window highlights the need for appropriate patient identification, further discovery of superior biomarkers or molecular profiles representative of positive treatment response, and additional prospective comparative study.

RECQ1 A159C Polymorphism Is Associated With Overall Survival of Patients With Resected Pancreatic Cancer: A Replication Study in NRG Oncology Radiation Therapy Oncology Group 9704

PURPOSE

To confirm whether a previously observed association between RECQ1 A159C variant and clinical outcome of resectable pancreatic cancer patients treated with preoperative chemoradiation is reproducible in another patient population prospectively treated with postoperative chemoradiation.

METHODS AND MATERIALS

Patients were selected, according to tissue availability, from eligible patients with resected pancreatic cancer who were enrolled on the NRG Oncology Radiation Therapy Oncology Group 9704 trial of 5-fluorouacil (5-FU)-based chemoradiation preceded and followed by 5-FU or gemcitabine. Deoxyribonucleic acid was extracted from paraffin-embedded tissue sections, and genotype was determined using the Taqman method. The correlation between genotype and overall survival was analyzed using a Kaplan-Meier plot, log-rank test, and multivariate Cox proportional hazards models.

RESULTS

In the 154 of the study's 451 eligible patients with evaluable tissue, genotype distribution followed Hardy-Weinberg equilibrium (ie, 37% had genotype AA, 43% AC, and 20% CC). The RECQ1 variant AC/CC genotype carriers were associated with being node positive compared with the AA carrier (P=.03). The median survival times (95% confidence interval [CI]) for AA, AC, and CC carriers were 20.6 (16.3-26.1), 18.8 (14.2-21.6), and 14.2 (10.3-21.0) months, respectively. On multivariate analysis, patients with the AC/CC genotypes were associated with worse survival than patients with the AA genotype (hazard ratio [HR] 1.54, 95% CI 1.07-2.23, P=.022). This result seemed slightly stronger for patients on the 5-FU arm (n=82) (HR 1.64, 95% CI 0.99-2.70, P=.055) than for patients on the gemcitabine arm (n=72, HR 1.46, 95% CI 0.81-2.63, P=.21).

CONCLUSIONS

Results of this study suggest that the RECQ1 A159C genotype may be a prognostic or predictive factor for resectable pancreatic cancer patients who are treated with adjuvant 5-FU before and after 5-FU-based chemoradiation. Further study is needed in patients treated with gemcitabine to determine whether an association exists.

Identification of RECQ1-regulated transcriptome uncovers a role of RECQ1 in regulation of cancer cell migration and invasion

The RECQ protein family of helicases has critical roles in protecting and stabilizing the genome. Three of the 5 known members of the human RecQ family are genetically linked with cancer susceptibility syndromes, but the association of the most abundant human RecQ homolog, RECQ1, with cellular transformation is yet unclear. RECQ1 is overexpressed in a variety of human cancers, indicating oncogenic functions. Here, we assessed genome-wide changes in gene expression upon knockdown of RECQ1 in HeLa and MDA-MB-231 cells. Pathway analysis suggested that RECQ1 enhances the expression of multiple genes that play key roles in cell migration, invasion, and metastasis, including EZR, ITGA2, ITGA3, ITGB4, SMAD3, and TGFBR2. Consistent with these results, silencing RECQ1 significantly reduced cell migration and invasion. In comparison to genome-wide annotated promoter regions, the promoters of genes downregulated upon RECQ1 silencing were significantly enriched for a potential G4 DNA forming sequence motif. Chromatin immunoprecipitation assays demonstrated binding of RECQ1 to the G4 motifs in the promoters of select genes downregulated upon RECQ1 silencing. In breast cancer patients, the expression of a subset of RECQ1-activated genes positively correlated with RECQ1 expression. Moreover, high RECQ1 expression was associated with poor prognosis in breast cancer. Collectively, our findings identify a novel function of RECQ1 in gene regulation and indicate that RECQ1 contributes to tumor development and progression, in part, by regulating the expression of key genes that promote cancer cell migration, invasion and metastasis.

Genomic profiling guides the choice of molecular targeted therapy of pancreatic cancer

Pancreatic cancer has the worst five-year survival rate of all malignancies due to its aggressive progression and resistance to therapy. Current therapies are limited to gemcitabine-based chemotherapeutics, surgery, and radiation. The current trend toward "personalized genomic medicine" has the potential to improve the treatment options for pancreatic cancer. Gene identification and genetic alterations like single nucleotide polymorphisms and mutations will allow physicians to predict the efficacy and toxicity of drugs, which could help diagnose pancreatic cancer, guide neoadjuvant or adjuvant treatment, and evaluate patients' prognosis. This article reviews the multifaceted roles of genomics and pharmacogenomics in pancreatic cancer.

RECQL1 and WRN DNA repair helicases: potential therapeutic targets and proliferative markers against cancers

RECQL1 and WRN helicases in the human RecQ helicase family participate in maintaining genome stability, DNA repair, replication, and recombination pathways in the cell cycle. They are expressed highly in rapidly proliferating cells and tumor cells, suggesting that they have important roles in the replication of a genome. Although mice deficient in these helicases are indistinguishable from wild-type mice, their embryonic fibroblasts are sensitive to DNA damage. In tumor cells, silencing the expression of RECQL1 or WRN helicase by RNA interference induces mitotic catastrophe that eventually kills tumor cells at the mitosis stage of the cell cycle. By contrast, the same gene silencing by cognate small RNA (siRNA) never kills normal cells, although cell growth is slightly delayed. These findings indicate that RECQL1 and WRN helicases are ideal molecular targets for cancer therapy. The molecular mechanisms underlying these events has been studied extensively, which may help development of anticancer drugs free from adverse effects by targeting DNA repair helicases RECQL1 and WRN. As expected, the anticancer activity of conventional genotoxic drugs is significantly augmented by combined treatment with RECQL1- or WRN-siRNAs that prevents DNA repair in cancer cells. In this review, we focus on studies that clarified the mechanisms that lead to the specific killing of cancer cells and introduce efforts to develop anticancer RecQ-siRNA drugs free from adverse effects.

An appraisal of RECQ1 expression in cancer progression

RECQ1 is the most abundant member of the human RecQ family of DNA helicases genetically linked with cancer predisposition syndromes and well known for their functions in genome stability maintenance through DNA repair. Despite being the first discovered RecQ homolog in humans, biological functions of RECQ1 have remained largely underappreciated and its relevance to cellular transformation is yet unclear. RECQ1 is overexpressed and amplified in many clinical cancer samples. In silico evaluation of RECQ1 mRNA expression across the NCI-60 cancer cell lines predicts an association of RECQ1 with cancer cell migration, invasion, and metastasis. Consistent with this, latest work implicates RECQ1 in regulation of gene expression, especially of those associated with cancer progression. Functionally, silencing RECQ1 expression significantly reduces cell proliferation, migration, and invasion. Collectively, these results propose that discerning the role of RECQ1 in conferring proliferative and invasive phenotype to cancer cells could be useful in developing therapeutic strategies to block primary tumor progression and metastasis.

Haplotype analysis of RECQL5 gene and laryngeal cancer

RECQL is a DNA helicase involved in DNA mismatch repair. Previous studies indicated that the RECQL gene mutation was associated with human cancers. In the present study, we investigated the association between polymorphisms of RECQL gene and laryngeal cancer in a Chinese population. Four polymorphisms of the RECQL5 gene (rs820186, rs820196, rs820200, and rs4789223) were genotyped by the TaqMan method in 275 patients with larynx cancer and 300 age- and sex-matched non-cancer controls. We found that rs820196 polymorphism of RECQL5 was associated with larynx cancer, the CC genotype (16.4% vs 9.3%, P = 0.013) and C allele (42% vs 34.2%, P = 0.006) was common in larynx cancer patients than in the control subjects, respectively. Haplotype analysis showed that GCGA (OR = 18.955, 95% confidence interval (CI) 9.479 ~ 37.905; P < 0.001) and GTTG (OR = 1.684; 95% CI 1.327 ~ 2.137; P < 0.001) were associated with increased risk for larynx cancer. However, ACGA (OR = 0.605; 95% CI 0.430 ~ 0.852; P = 0.003), GCGG (OR = 0.636; 95% CI 0.411 ~ 0.982; P = 0.039), and GTGG (OR = 0.194; 95% CI 0.104 ~ 0.361; P < 0.001) were associated with decreased risk for larynx cancer. The present study indicated that RECQL5 genetic polymorphism and haplotypes were associated with larynx cancer in a Chinese population.

Survival among pancreaticoduodenectomy patients treated for pancreatic head cancer <1 or 2 cm

BACKGROUND

Size of primary tumor has implications for staging, imaging, and treatment of pancreatic head carcinomas. Limited data suggest that small tumor size is associated with better survival. The objective of this population study is to analyze characteristics and survival of patients with resected pancreatic head ductal carcinomas sized <1 and 2 cm.

METHODS

Analysis of resected invasive pancreatic head ductal carcinomas captured within SEER Program from 1998 to 2008.

RESULTS

A total of 7,135 cases were analyzed with nodal metastases in 31, 55, and 67 % for subcentimeter, 1.1-2 cm, and >2 cm tumors, respectively. Median survival was longest for node-negative tumors (38, 26, 19 months for tumors measuring ≤ 1, 1.1-2, and >2 cm, respectively; p < 0.001) versus node-positive tumors (18, 19, 14 months, p < 0.001). In multivariate analysis, large tumor size was associated with higher risk of death (hazard ratio (HR) = 1.179 for tumors 1.1-2 cm, p = 0.152; HR = 1.665 for tumors >2 cm, p < 0.001).

CONCLUSIONS

Small pancreatic cancers have a poor prognosis and surprisingly high rate of nodal involvement; therefore, they cannot be considered early cancers. Size-based screening is unlikely to save lives with current treatment options.

A replication study and genome-wide scan of single-nucleotide polymorphisms associated with pancreatic cancer risk and overall survival

PURPOSE

To explore the effects of single-nucleotide polymorphisms (SNP) on pancreatic cancer risk and overall survival (OS).

EXPERIMENTAL DESIGN

The germ line DNA of 531 pancreatic cancer cases and 305 healthy controls from a hospital-based study was genotyped at SNPs previously reported to be associated with pancreatic cancer risk or clinical outcome. We analyzed putative risk SNPs for replication of their reported effects on risk and tested for novel effects on OS. Similarly, we analyzed putative survival-associated SNPs for replication of their reported effects on OS and tested for novel effects on risk. Finally, we conducted a genome-wide association study (GWAS) of OS using a subset of 252 cases, with two subsequent validation sets of 261 and 572 patients, respectively.

RESULTS

Among seven risk SNPs analyzed, two (rs505922 and rs9543325) were associated with risk (P < 0.05). Among 24 survival-associated SNPs analyzed, one (rs9350) was associated with OS (P < 0.05). No putative risk SNPs or putative survival-associated SNPs were found to be associated with OS or risk, respectively. Furthermore, our GWAS identified a novel SNP [rs1482426, combined stage I and II, P = 1.7 × 10(-6), per-allele HR, 1.74; 95% confidence interval (CI), 1.38-2.18] to be putatively associated with OS.

CONCLUSIONS

The effects of SNPs on pancreatic cancer risk and OS were replicated in our study, although further work is necessary to understand the functional mechanisms underlying these effects. More importantly, the putative association with OS identified by GWAS suggests that GWAS may be useful in identifying SNPs associated with clinical outcome in pancreatic cancer.

HuR status is a powerful marker for prognosis and response to gemcitabine-based chemotherapy for resected pancreatic ductal adenocarcinoma patients

BACKGROUND

Pancreatic ductal adenocarcinoma (PDA) is a devastating disease that killed nearly 38,000 people in the United States this past year.

OBJECTIVE

Treatment of PDA typically includes surgery and/or chemotherapy with gemcitabine. No reliable biomarker exists for prognosis or response to chemotherapy. Two previously proposed prognostic markers, cyclooxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF), are regulated by Hu protein antigen R (HuR), an mRNA binding protein that we have previously demonstrated to be a promising predictive marker of gemcitabine response. This study was designed to evaluate the clinical utility of HuR, COX-2, and VEGF as potential prognostic and predictive biomarkers for PDA.

METHODS

A tissue microarray of 53 PDA specimens from patients who underwent potentially curative pancreatic resection was analyzed. HuR, COX-2, and VEGF status were correlated with clinicopathologic and survival data. We also performed ribonucleoprotein immunoprecipitation assays using an HuR antibody to assess VEGF and COX-2 mRNA binding to HuR in pancreatic cancer cells.

RESULTS

Roughly 50% (27/53) of patients had high cytoplasmic HuR expression. These patients had worse pathologic features as assessed by T staging (P = 0.005). Only cytoplasmic HuR status correlated with tumor T staging, whereas VEGF (P = 1.0) and COX-2 (P = 0.39) expression did not correlate with T staging. Additionally, HuR status was an unprecedented positive predictive marker for overall survival in patients treated with gemcitabine, pushing median survival over 45 months in the high cytoplasmic HuR expressing patient population compared with less than 23 months in the low cytoplasmic HuR expressing patient group (P = 0.033 for log-rank test and P = 0.04 in a Cox regression model) for the low versus high cytoplasmic HuR expressing group. We also validated that mRNA transcripts for both VEGF and the gemcitabine metabolizing enzyme, deoxycytidine kinase, are specifically bound by HuR in pancreatic cancer cells.

CONCLUSIONS

HuR is a useful prognostic biomarker for PDA patients as indicated by its association with higher tumor T stage. Additionally, HuR status is a robust predictor of outcome for patients with resected PDA in the setting of adjuvant gemcitabine therapy. Finally, HuR binds to VEGF mRNA implying that HuR, in part, regulates VEGF expression in PDA. This study supports the notion that HuR status should be used by clinicians for the individualized treatment of PDA in the future.