DNA repair: a double-edged sword

Genetic polymorphisms as potential pharmacogenetic biomarkers for platinum-based chemotherapy in non-small cell lung cancer

Platinum-based chemotherapy (PBC) is a widely used treatment for various solid tumors, including non-small cell lung cancer (NSCLC). However, its efficacy is often compromised by the emergence of drug resistance in patients. There is growing evidence that genetic variations may influence the susceptibility of NSCLC patients to develop resistance to PBC. Here, we provide a comprehensive overview of the mechanisms underlying platinum drug resistance and highlight the important role that genetic polymorphisms play in this process. This paper discussed the genetic variants that regulate DNA repair, cellular movement, drug transport, metabolic processing, and immune response, with a focus on their effects on response to PBC. The potential applications of these genetic polymorphisms as predictive indicators in clinical practice are explored, as are the challenges associated with their implementation.

ARL2 is required for homologous recombination repair and colon cancer stem cell survival

ARL2 regulates the dynamics of cytological components and is highly expressed in colon cancer tissues. Here, we report novel roles of ARL2 in the cell nucleus and colon cancer stem cells (CSCs). ARL2 is expressed at relatively low levels in K‐RAS active colon cancer cells, but its expression is induced in CSCs. Depletion of ARL2 results in M phase arrest exclusively in non‐CSC cultured cells; in addition, DNA break stress accumulates in CSCs leading to apoptosis. ARL2 expression is positively associated with the expression of all six RAD51 family genes, which are essential for homologous recombination repair (HRR). Furthermore, ARL2 is required for HRR and detected within chromatin compartments. These results demonstrate the requirement of ARL2 in colon CSC maintenance, which possibly occurs through mediating double‐strand break DNA repair in the nucleus.

Beyond the Double-Strand Breaks: The Role of DNA Repair Proteins in Cancer Stem-Cell Regulation

Simple Summary

Cancer stem cells (CSCs) are a tumor cell population maintaining tumor growth and promoting tumor relapse if not wholly eradicated during treatment. CSCs are often equipped with molecular mechanisms making them resistant to conventional anti-cancer therapies whose curative potential depends on DNA damage-induced cell death. An elevated expression of some key DNA repair proteins is one of such defense mechanisms. However, new research reveals that the role of critical DNA repair proteins is extending far beyond the DNA repair mechanisms. This review discusses the diverse biological functions of DNA repair proteins in CSC maintenance and the adaptation to replication and oxidative stress, anti-cancer immune response, epigenetic reprogramming, and intracellular signaling mechanisms. It also provides an overview of their potential therapeutic targeting.

Abstract

Cancer stem cells (CSCs) are pluripotent and highly tumorigenic cells that can re-populate a tumor and cause relapses even after initially successful therapy. As with tissue stem cells, CSCs possess enhanced DNA repair mechanisms. An active DNA damage response alleviates the increased oxidative and replicative stress and leads to therapy resistance. On the other hand, mutations in DNA repair genes cause genomic instability, therefore driving tumor evolution and developing highly aggressive CSC phenotypes. However, the role of DNA repair proteins in CSCs extends beyond the level of DNA damage. In recent years, more and more studies have reported the unexpected role of DNA repair proteins in the regulation of transcription, CSC signaling pathways, intracellular levels of reactive oxygen species (ROS), and epithelial–mesenchymal transition (EMT). Moreover, DNA damage signaling plays an essential role in the immune response towards tumor cells. Due to its high importance for the CSC phenotype and treatment resistance, the DNA damage response is a promising target for individualized therapies. Furthermore, understanding the dependence of CSC on DNA repair pathways can be therapeutically exploited to induce synthetic lethality and sensitize CSCs to anti-cancer therapies. This review discusses the different roles of DNA repair proteins in CSC maintenance and their potential as therapeutic targets.

Alteration of DNA mismatch repair capacity underlying the co-occurrence of non-small-cell lung cancer and nonmedullary thyroid cancer

Both non-small-cell lung cancer cases in never-smokers and nonmedullary thyroid cancer cases have been increasing in developed countries. Some studies have shown an excess of co-occurrence of non-small-cell lung cancer and nonmedullary thyroid cancer. We aimed to clarify the underlying genetic factors that contribute to the occurrence of these two malignancies. We performed germline exome sequencing in a cohort of 9 patients with the two malignancies. In terms of candidate genes, we performed target resequencing, immunohistochemistry, and microsatellite instability testing on another cohort. Two rare missense heterozygous variants in MSH6 were identified and verified by Sanger sequencing. One available tumour specimen showed heterogeneous MSH6 status in immunohistochemistry. Further exploration with different cohorts (a total of 8 patients with the two malignancies) demonstrated that 2 out of 8 patients had a germline missense or promotor variant of MLH1 and four out of 10 tumour specimens revealed heterogeneous immunohistochemistry staining in any of the four mismatch repair proteins: MLH1, PMS2, MSH2 and MSH6. Although our cohort showed a different disease profile than Lynch syndrome, this study suggests causal roles of impaired DNA mismatch repair capacity in non-small-cell lung cancer and nonmedullary thyroid cancer.

MicroRNA Expression Changes in Women with Breast Cancer Stratified by DNA Repair Capacity Levels

Breast cancer (BC) is the most commonly diagnosed cancer in women worldwide and is the leading cause of death among Hispanic women. Previous studies have shown that women with a low DNA repair capacity (DRC), measured through the nucleotide excision repair (NER) pathway, have an increased BC risk. Moreover, we previously reported an association between DRC levels and the expression of the microRNA (miRNA) let-7b in BC patients. MiRNAs can induce genomic instability by affecting the cell's DNA damage response while influencing the cancer pathobiology. The aim of this pilot study is to identify plasma miRNAs related to variations in DRC levels in BC cases. Hypothesis. Our hypothesis consists in testing whether DRC levels can be correlated with miRNA expression levels. Methods. Plasma samples were selected from 56 (27 cases and 29 controls) women recruited as part of our BC cohort. DRC values were measured in lymphocytes using the host-cell reactivation assay. The samples were divided into two categories: low (≤3.8%) and high (>3.8%) DRC levels. MiRNAs were extracted to perform an expression profile analysis. Results. Forty miRNAs were identified to be BC-related (p<0.05, MW), while 18 miRNAs were found to be differentially expressed among BC cases and controls with high and low DRC levels (p<0.05, KW). Among these candidates are miR-299-5p, miR-29b-3p, miR-302c-3p, miR-373-3p, miR-636, miR-331-5p, and miR-597-5p. Correlation analyses revealed that 4 miRNAs were negatively correlated within BC cases with low DRC (p<0.05, Spearman's correlation). Results from multivariate analyses revealed that the clinicopathological characteristics may not have a direct effect on specific miRNA expression. Conclusion. This pilot study provides evidence of four miRNAs that are negatively regulated in BC cases with low DRC levels. Additional studies are needed in order to have a complete framework regarding the overall DRC levels, miRNA expression profiles, and tumor characteristics.

Association of Base Excision Repair Gene Polymorphisms with the Response to Chemotherapy in Advanced Non-Small Cell Lung Cancer

Background:

Base excision repair (BER) plays an important role in the maintenance of genome integrity and anticancer drug resistance. This study aimed to explore the role of BER gene polymorphisms in response to chemotherapy for advanced non-small cell lung cancer (NSCLC) patients treated with platinum-based chemotherapy.

Methods:

During the period from November 2009 to January 2016, a total of 152 patients diagnosed with NSCLC Stage IIIB and IV in the First Hospital of Jilin University were admitted into this study. The XRCC1 G28152A, MUTYH G972C, HOGG1 C1245G, and PARP1 T2444C polymorphisms of all the patients were detected by mass spectrometry. The logistic regression was used for statictical analysis. All tests were bilateral test, and a P < 0.05 was considered statistically significant.

Results:

The logistic regression model showed that the response rate of chemotherapy of the PARP1 T2444C polymorphisms, CC genotype (odds ratio [OR]: 5.216, 95% confidence interval [CI]: 1.568–17.352, P = 0.007), TC genotype (OR: 2.692, 95% CI: 1.007–7.198, P = 0.048), as well as the genotype of TC together with CC (OR: 3.178, 95% CI: 1.229–8.219, P = 0.017) were significantly higher than those of TT wild type. There was no relationship between the MUTYH G972C, XRCC1 G28152A, and HOGG1 C1245G gene polymorphisms and chemosensitivity.

Conclusions:

The PARP1 2444 mutation allele C might be associated with the decreased sensitivity to platinum-based chemotherapy in advanced NSCLC. These findings may be helpful in designing individualized cancer treatment.

Chinese C allele carriers of the ERCC5 rs1047768 polymorphism are more sensitive to platinum-based chemotherapy: a meta-analysis

It is suspected that ERCC5 rs1047768 and rs17655 polymorphisms influence the response to platinum-based chemotherapy. This meta-analysis was performed to summarize the scattered evidence regarding the association between these two polymorphisms and sensitivity to platinum-based treatment. Thirteen studies were included after a comprehensive literature search. The pooled odds ratios and 95% confidence intervals suggested that the C allele of the ERCC5 rs1047768 polymorphism is associated with elevated sensitivity to platinating agents, especially for Chinese patients. However, no difference among rs17655 genotypes could be detected.

Enhancement of cisplatin cytotoxicity by Retigeric acid B involves blocking DNA repair and activating DR5 in prostate cancer cells

Retigeric acid B (RAB), a natural compound isolated from lichen, has been demonstrated to inhibit cell growth and promote apoptosis in prostate cancer (PCa) cells. The present study evaluated the function of RAB combined with clinical chemotherapeutic drugs in PCa cell lines by MTT assay, reverse transcription quantitative polymerase chain reaction and western blot analysis, and identified that RAB at low doses produced significant synergistic cytotoxicity in combination with cisplatin (CDDP); however, no marked synergism between RAB and the other chemotherapeutics was observed. Additional studies revealed that RAB exerted an inhibitory effect on DNA damage repair pathways, including the nucleotide excision repair and mismatch repair pathways, which are involved in the sensitivity to CDDP-based chemotherapy, as suggested by the significantly downregulated expression of certain associated repair proteins. Notably, Excision repair cross-complementing 1, a critical gene in the nucleotide excision repair pathway, exhibited the most significant decrease. When combined with CDDP, RAB-mediated impairment of DNA repair resulted in prolonged DNA damage, as demonstrated by the long-lasting appearance of phosphorylation of histone H2AX at Ser139, which potentially enhanced the chemosensitivity to CDDP. Concurrently, the proapoptotic protein death receptor 5 (DR5) was activated by RAB, which also enhanced the chemotherapeutic response of CDDP. Knockdown of DR5 partially blocked RAB-CDDP synergism, suggesting the crucial involvement of DR5 in this event. The results of the present study identified that RAB functioned synergistically with CDDP to increase the efficacy of CDDP by inhibiting DNA damage repair and activating DR5, suggesting the mechanistic basis for the antitumor effect of RAB in combination with current chemotherapeutics.

A genetic variation in microRNA target site of ETS2 is associated with clinical outcomes of paclitaxel-cisplatin chemotherapy in non-small cell lung cancer

The present study was performed to investigate the association of single nucleotide polymorphisms (SNPs) located in the miRNA target sites with the clinical outcomes of first line paclitaxel-cisplatin chemotherapy in advanced NSCLC. Eighty SNPs in miRNA binding sites of cancer related genes selected from 18,500 miRNA:target bindings in crosslinking, ligation, and sequencing of hybrids (CLASH) data were investigated in 379 advanced NSCLC patients using a sequenom mass spectrometry-based genotype assay. qRT-PCR and luciferase assay were conducted to examine functional relevance of potentially functional SNPs in miRNA binding sites. Of the 80 SNPs analyzed, 16 SNPs were significantly associated with the clinical outcomes after chemotherapy. Among these, ANAPC1 rs3814026C>T, ETS2 rs461155A>G, SORBS1 rs7081076C>A and POLR2A rs2071504C>T could predict both chemotherapy response and survival. Notably, ETS2 rs461155A>G was significantly associated with decreased ETS2 mRNA expression in both tumor and paired normal lung tissues (Ptrend = 4 × 10⁻⁷, and 3 × 10⁻⁴, respectively). Consistently, a decreased expression of the reporter gene for the G allele of rs461155 compared with the A allele was observed by luciferase assay. These findings suggest that the four SNPs, especially ETS2 rs461155A>G, could be used as biomarkers predicting the clinical outcomes of NSCLC patients treated with first-line paclitaxel-cisplatin chemotherapy.

A review on the effects of current chemotherapy drugs and natural agents in treating non-small cell lung cancer

Lung cancer is the leading cause of cancer deaths worldwide, and this makes it an attractive disease to review and possibly improve therapeutic treatment options. Surgery, radiation, chemotherapy, targeted treatments, and immunotherapy separate or in combination are commonly used to treat lung cancer. However, these treatment types may cause different side effects, and chemotherapy-based regimens appear to have reached a therapeutic plateau. Hence, effective, better-tolerated treatments are needed to address and hopefully overcome this conundrum. Recent advances have enabled biologists to better investigate the potential use of natural compounds for the treatment or control of various cancerous diseases. For the past 30 years, natural compounds have been the pillar of chemotherapy. However, only a few compounds have been tested in cancerous patients and only partial evidence is available regarding their clinical effectiveness. Herein, we review the research on using current chemotherapy drugs and natural compounds (Wortmannin and Roscovitine, Cordyceps militaris, Resveratrol, OSU03013, Myricetin, Berberine, Antroquinonol) and the beneficial effects they have on various types of cancers including non-small cell lung cancer. Based on this literature review, we propose the use of these compounds along with chemotherapy drugs in patients with advanced and/or refractory solid tumours.

The genetic variations in DNA repair genes ERCC2 and XRCC1 were associated with the overall survival of advanced non-small-cell lung cancer patients

It was reported that DNA repair can confer cancer cell resistance to therapeutic treatments by activating antiapoptotic cellular defense. We hypothesized that genetic variants of DNA repair genes may be associated with lung cancer prognosis. Seventeen tagging single‐nucleotide polymorphism (tagSNPs) selected from 12 DNA repair genes were genotyped in 280 advanced non‐small‐cell lung cancer (NSCLC) patients by TaqMan assay. The associations of these SNPs and overall survival of advanced NSCLC patients were investigated. Advanced NSCLC patients carrying ERCC2 rs50872 CT+TT genotypes had significantly longer median survival time (MST) and decreased death risk than patients with rs50872 CC genotype [log‐rank P = 0.031; adjusted HR(95% CI) = 0.73 (0.55–0.98), P = 0.033]. These effects were mainly seen among younger patients (≤65 years old) [HR(95% CI) = 0.57 (0.37–0.87), P = 0.010], patients without surgery [HR(95% CI) = 0.68 (0.47–0.98), P = 0.036] but with chemotherapy [HR(95% CI) = 0.64 (0.46–0.91), P = 0.012] or radiotherapy [HR(95% CI) = 0.58 (0.38–0.89), P = 0.013]. Meanwhile, compared to advanced NSCLC patients with rs25487 GG genotype, patients carrying XRCC1 rs25487 GA+AA genotypes had significantly shorter MST (MST = 11.7 vs. 16.7, log‐rank P = 0.048). In addition, advanced NSCLC patients carrying the ERCC2 rs50872 CC in combination with XRCC1 rs25487 GA+AA genotype had the shortest MST (11.2 month) and highest death risk [HR(95% CI) = 1.70 (1.15–2.52), P = 0.008] when compared with those carrying rs50872 CT+TT and rs25487 GG genotype (MST = 22.0 month). The ERCC2 rs50872 T allele was associated with favorable but XRCC1 rs25487 A allele with bad survival for advanced NSCLC in Chinese population, which may offer novel biomarkers for predicting clinical outcomes.

Base excision repair pathway: PARP1 genotypes as modulators of therapy response in cervical cancer patients

CONTEXT

Genetic polymorphisms in genes of the base excision repair (BER) pathway appear to modulate the therapy response of cancer patients. PARP1 protein recognizes the DNA strand damage and facilitates the subsequent recruitment of BER proteins. Few studies have reported an association between PARP1 Val762Ala polymorphism (rs1136410) and cancer therapy response.

OBJECTIVE

The purpose of our study was to determine whether PARP1 Val762Ala polymorphism have prognostic value in patients with cervical cancer.

MATERIALS AND METHODS

Two hundred and sixty adult patients, with histologically confirmed cervical cancer, at FIGO-stages IB2-IVA, primarily treated with concurrent chemotherapy (cisplatin) and radiotherapy. Overall survival (OS) and disease-free survival (DFS) were the primary end points of the analysis. The PARP1 Val762Ala genetic variants were analyzed by allelic discrimination by real-time PCR.

RESULTS

We observed that peri- and postmenopausal women carrying the C-allele present a statistically significant lower OS and DFS (log-rank test, p = 0.008 and p = 0.006, respectively) among those with early stage cervical cancer. Cox regression analysis confirmed these results, after adjustment for other prognostic factors (for OS: HR, 3.70; 95%CI, 1.32-10.38; p = 0.013 and for DFS: HR, 3.97; 95%CI, 1.59-9.93; p = 0.003).

CONCLUSIONS

This is the first study evaluating the effect of PARP1 Val762Ala polymorphism in treatment response in cervical cancer patients. PARP1 genotypes may contribute as an independent prognostic factor in cervical cancer, being useful in predicting the clinical outcome.

Gender-related differences in susceptibility to oxidative stress in healthy middle-aged Serbian adults

Gender-related differences in the association between polymorphism of xenobiotic-metabolising enzymes or non-genetic biomarkers and susceptibility to oxidative stress was assessed in healthy middle-aged Serbian adults, by urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG/creatinine) and total antioxidant status in serum (TAOS). Females were more susceptible to oxidative stress. In both genders, positive predictor of the antioxidative protection was serum triglyceride, while BMI <25 kg/m(2) was associated with oxidative stress. Susceptibility to oxidative stress in males was associated with GSTT1*null allele and increased serum iron, but in females, it was decreased serum bilirubin. Early identification of the risk factors could be important in the prevention of oxidative stress-related diseases.

DNA repair gene polymorphisms and clinical outcome of patients with primary small cell carcinoma of the esophagus

Polymorphisms in DNA repair genes impact on the synthesis of DNA repair proteins that are crucial to the repair of DNA damages induced by chemotherapy and radiotherapy. We retrospectively examined whether there was an association between the selected six single nucleotide polymorphisms (SNPs) of five DNA repair genes (PARP1-Val762Ala, XRCC1-Arg194Trp, XRCC1-Arg399Gln, XPC-Lys939Gln, BRCA1-Lys1183Arg, and BRCA2-Asn372His) and the clinical outcome of patients with primary small cell carcinoma of esophagus (SCCE), and it showed that the median progression-free survival (PFS) and the overall survival (OS) were 11.8 versus 9.7 months (P = 0.041) and 17.4 versus 14.8 months (P = 0.032) for patients carrying the variant allele (T/C + C/C) and the wild-type allele (T/T) of PARP1-Val762Ala polymorphism, respectively. However, no statistical significance was observed in the other five polymorphic loci (P > 0.05). When these six SNPs were combined, however, patients with at least three variant genotypes had significantly longer PFS and OS compared with those carrying less than three variant genotypes (P = 0.009 and P = 0.007, respectively). The presence of at least three polymorphic variants in certain DNA repair genes may impact on patient survival and could be a potential genomic predictor of clinical response to DNA-damaging treatment in SCCE patients.

An individual drug-therapy and genetic testing report of temporal bone verrucous carcinoma

Objective

To investigate the pathology and pathogenesis of and treatment methods for temporal bone verrucous carcinoma.

Materials and methods

A single-patient report of verrucous carcinoma on the left external auditory canal is presented and analyzed along with all cases of temporal bone verrucous carcinoma that have been documented in the English literature.

Results

Most of the patients with verrucous carcinoma of the temporal bone have histories of surgery, trauma, or infection, and verrucous carcinomas are sensitive to antimicrotubule chemotherapeutic medicines. Adjuvant radiation therapy is not effective, but surgical treatment might be relatively more effective.

Conclusion

Temporal bone verrucous carcinoma has a poor prognosis; therefore, the preferred treatment is surgical resection facilitated with antimicrotubule chemotherapeutic treatment. Adjuvant radiation therapy is not a preferred treatment for temporal bone verrucous carcinoma.

Identification of a putative Tdp1 inhibitor (CD00509) by in vitro and cell-based assays

Mutations of DNA repair pathways contribute to tumorigenesis and provide a therapeutic target for synthetic lethal interactions in tumor cells. Given that tyrosyl-DNA phosphodiesterase 1 (Tdp1) repairs stalled topoisomerase-I DNA complexes, we hypothesized that inhibition of Tdp1 has synthetic lethal effects in some cancers. To test this, we screened tumor arrays for Tdp1 expression and observed that Tdp1 is expressed in many tumors, including more than 90% of human breast tumors. Subsequent chemical screening identified putative Tdp1 inhibitors. Treatment of control human mammary epithelial cells and the breast cancer cell line MCF-7 with compound CD00509 preferentially sensitized MCF-7 cells to camptothecin and decreased cell proliferation 25% more than camptothecin treatment alone. This suggests that CD00509 specifically targeted Tdp1 in vitro, and CD00509 increased the sensitivity of wild-type murine embryonic fibroblasts (MEFs) to camptothecin to a degree comparable to that of Tdp1(-/-) MEFs. In addition, consistent with poly ADP-ribose polymerase-1 (PARP-1) collaborating with Tdp1 in DNA repair, combined Tdp1 and PARP-1 inhibition was more detrimental to MCF-7 cells than either treatment alone, whereas the combination was not additively harmful to control mammary cells. We conclude that targeting Tdp1 in anticancer therapy preferentially enhances the sensitivity of some breast cancer cells to camptothecin and may be an effective adjuvant for breast cancer therapy.

Associations of polymorphisms in DNA repair genes and MDR1 gene with chemotherapy response and survival of non-small cell lung cancer

Objectives

We aimed to determine the associations of genetic polymorphisms of excision repair cross-complementation group 1 (ERCC1) rs11615, xeroderma pigmentosum group D (XPD/ERCC2) rs13181, X-ray repair cross complementing group 1 (XRCC1) rs25487, XRCC3 rs1799794, and breast cancer susceptibility gene 1 (BRCA1) rs1799966 from the DNA repair pathway and multiple drug resistance 1 (MDR1/ABCB1) rs1045642 with response to chemotherapy and survival of non-small cell lung cancer (NSCLC) in a Chinese population.

Materials and Methods

A total of 352 NSCLC patients were enrolled to evaluate the associations of the six SNPs with response to chemotherapy and overall survival. Logistic regressions were applied to test the associations of genetic polymorphisms with response to chemotherapy in 161 advanced NSCLC patients. Overall survival was analyzed in 161 advanced and 156 early stage NSCLC patients using the Kaplan-Meier method with log-rank test, respectively. Multivariate Cox proportional hazards model was performed to determine the factors independently associated with NSCLC prognosis.

Results

BRCA1 rs1799966 minor allele C (TC+CC vs. TT, OR = 0.402, 95%CI = 0.204−0.794, p = 0.008) and MDR1/ABCB1 rs1045642 minor allele A (GA +AA vs. GG, OR = 0.478, 95%CI = 0.244−0.934, p = 0.030) were associated with a better response to chemotherapy in advanced NSCLC patients. Survival analyses indicated that BRCA1 rs1799966 TC+CC genotypes were associated with a decreased risk of death (HR = 0.617, 95% CI = 0.402−0.948, p = 0.028) in advanced NSCLC patients, and the association was still significant after the adjustment for covariates. Multivariate Cox regression analysis showed that ERCC1 rs11615 AA genotype (P = 0.020) and smoking (p = 0.037) were associated with increased risks of death in early stage NSCLC patients after surgery.

Conclusions

Polymorphisms of genes in DNA repair pathway and MDR1 could contribute to chemotherapy response and survival of patients with NSCLC.

The prognostic value of ERCC1 expression in gastric cancer patients treated with platinum-based chemotherapy: a meta-analysis

Numerous studies examined the association between excision repair complementation group 1 (ERCC1) expression and the prognosis of gastric cancer patients receiving platinum-based chemotherapy but yielded controversial results. We thus conducted a meta-analysis to quantitatively evaluate the prognostic value of ERCC1 expression in gastric cancer patients receiving platinum-based chemotherapy. A systematic literature search was performed to identify relevant studies in PubMed, Web of Science, Embase, Cochrane Library, China National Knowledge Infrastructure, Chinese Biomedical Literature Database, and WanFang Database up to December 17, 2013. Pooled hazard ratios (HRs) or odds ratios (ORs) with 95 % confidence intervals (CIs) were estimated. Moreover, meta-regression analysis and subgroup analysis were conducted according to ethnicity, HR extraction, detection methods, survival analysis, and quality score. A total of 1,409 patients from 21 studies were subjected to final analysis. Positive/high ERCC1 expression was significantly associated with poorer overall survival (HR, 1.58; 95 % CI, 1.09-2.28), especially in Asians (HR, 1.81; 95 % CI, 1.20-2.73), and lower response rate (OR, 0.26; 95 % CI, 0.18-0.36), but not with clinicopathological features, such as gender (OR, 1.01; 95 % CI, 0.68-1.51), grade (OR, 0.66; 95 % CI, 0.43-1.01), and stage (OR, 1.05; 95 % CI, 0.58-1.90). This meta-analysis suggested that ERCC1 expression might be a useful biomarker to predict response and survival for gastric cancer patients receiving platinum-based chemotherapy, particularly in Asians.

Genetic polymorphisms in XPG could predict clinical outcome of platinum-based chemotherapy for advanced non-small cell lung cancer

We conducted a prospective study to investigate the role of four single nucleotide polymorphisms (SNPs) of XPG on the clinical outcome of advanced non-small cell lung cancer (NSCLC) treated with platinum-based doublets chemotherapy. In total, 277 patients with histologically confirmed NSCLC were mainly from December 2007 and December 2008. The genotypes of rs2296147T>C, rs1047768C>T, rs873601G>A, and rs17655G>C were determined by polymerase chain reaction-restriction fragment length polymorphism. By univariate analysis, a shorter survival was associated with older age, sex, and higher disease stage. By multivariate Cox regression analysis, patients carrying rs2296147 TT genotype and T allele were prognostic factors of progression-free survival (PFS) and overall survival (OS). Similarly, patients carrying rs873601 GG genotype and G allele were marginally significantly associated with favorable outcome for PFS and OS. We found that individuals carrying both rs2296147 T allele and rs873601 G allele were associated with better PFS and OS. However, rs1047768C>T and rs17655G>C polymorphisms did not influence the PFS and OS of advanced NSCLC. In summary, our study provided statistical evidence that XPG rs2296147T>C and rs873601G>A polymorphisms may be used as surrogate markers toward individualizing NSCLC treatment strategies.

ERCC1 Protein Expression Is Associated with Differential Survival in Oropharyngeal Head and Neck Squamous Cell Carcinoma

Objective

To investigate ERCC1 protein expression and its relationship to clinical factors and treatment outcomes in patients with head and neck squamous cell carcinoma (HNSCC).

Design

Case series.

Setting

Tertiary care academic center.

Subjects

One hundred and seventy-six patients diagnosed with HNSCC and treated with intent to cure between 2002 and 2008 were analyzed with respect to clinical data and tumor pathology.

Main Outcome Measures

Tissue microarrays were constructed from tumor blocks and immunohistochemical staining for ERCC1 performed. ERCC1 expression status was dichotomized into high and low using the Allred score. Clinical characteristics of patients with high versus low ERCC1 expression were compared. Distributions of overall survival (OS) and progression-free survival (PFS) were analyzed using the Kaplan-Meier method.

Results

Of 176 patients, ERCC1 showed baseline nuclear staining in 148 patients (84.1%). Lower staining intensity ERCC1 expression was prominent in parabasal cells in the lower half of the epithelium, while at high staining intensity, ERCC1 expression was present throughout the epithelium. The median H-score was 50. No significant differences in age, gender, smoking status, tumor site, or stage were seen between the high and low ERCC1 expression groups. Expression of ERCC1 stratified by tumor site correlates with OS. Patients with oropharyngeal HNSCC and high ERCC1 expression (H-score > 120) were more likely to survive ( P < .01) and remain disease free when compared to non-oropharyngeal squamous cell carcinoma (SCCa) patients with high ERCC1 expression despite treatment modality and human papillomavirus virus (HPV) status.

Conclusion

Patients with oropharyngeal SCCa and high ERCC1 expression may have better outcomes despite HPV status.

Genetic polymorphisms of ERCC1‑118, XRCC1‑399 and GSTP1‑105 are associated with the clinical outcome of gastric cancer patients receiving oxaliplatin‑based adjuvant chemotherapy

The aim of the present study was to determine whether specific molecular parameters may serve as predictors of treatment outcomes and toxicity of oxaliplatin (OXA)‑based chemotherapy, which is used as an adjuvant treatment in resected gastric cancer. All gastric cancer patients examined in the study received an OXA/5‑fluorouracil chemotherapeutic regimen. Genetic polymorphisms of certain platinum‑related genes were determined by the TaqMan 5' nuclease assay and direct sequencing. Relapse‑free survival (RFS), overall survival (OS) and toxicity were evaluated according to each genotype. Following adjustment for the most relevant clinical variables, excision repair cross‑complimentary group 1 (ERCC1)‑118 and X-ray repair cross-complementing protein 1 (XRCC1‑399) demonstrated significant predictive value for RFS and OS. We also demonstrated that carrying at least one variant XRCC1 Arg399Gln or glutathione S-transferase π 1 (GSTP1) Ile105Val allele significantly increased the risk of any grade 3 or 4 hematological toxicity. In particular, carrying at least one variant GSTP1 Ile105Val allele was also significantly correlated with an increased risk of grade 3 or 4 gastrointestinal toxicity and neurotoxicity. Our data suggested that gastric cancer patients harboring ERCC1‑118 C/C and XRCC1‑399 A/G or A/A genotypes may benefit from receiving OXA‑based adjuvant chemotherapy, and carrying at least one variant XRCC1 Arg399Gln or GSTP1 Ile105Val allele may contribute to the occurrence of adverse drug effects associated with OXA‑based chemotherapy.

Pharmacogenetics of conventional chemotherapy in non-small-cell lung cancer: a changing landscape?

Pharmacogenetics might be used to select patients who may benefit from specific chemotherapy that best matches the individual and tumor genetic profile, thus allowing maximum activity and minimal toxicity. Even if most studies in non-small-cell lung cancer yielded contradictory results, several potential biomarkers for sensitivity/resistance to platinum compounds, gemcitabine, taxanes and pemetrexed have been proposed. However, these markers need to be validated within larger prospective randomized trials of customized chemotherapy in homogeneous populations. Other critical points include the optimization/standardization of technical procedures, and further studies to unravel the extremely complex regulation of gene function. From this perspective, the evaluation of key factors influencing genotype-phenotype relationships, such as miRNAs, and functional studies to clarify pharmacokinetic/pharmacodynamic interactions, are fundamental for the pharmacogenetic optimization of cancer chemotherapy. Finally, limitation of the traditional pharmacogenetic approach relying only on candidate genes suspected of affecting drug response is now being overcome by the use of novel genome-wide studies.

DNA repair and cytotoxic drugs: the potential role of RAD51 in clinical outcome of non-small-cell lung cancer patients

Many of the cytotoxic drugs used in the treatment of non-small-cell lung carcinoma patients can interfere with DNA activity and the definition of an individual DNA repair profile could be a key strategy to achieve better response to chemotherapeutic treatment. Although DNA repair mechanisms are important factors in the prevention of carcinogenesis, these molecular pathways are also involved in therapy response. RAD51 is a crucial element in DNA repair by homologous recombination and has been shown to interfere with the prognosis of patients treated with chemoradiotherapy. There is increasing evidence that genetic polymorphisms in repair enzymes can influence DNA repair capacity and, consequently, affect chemotherapy efficacy. We conducted this review to show the possible influence of the RAD51 genetic variants in damage repair capacity and treatment response in non-small-cell lung carcinoma patients.

DNA repair polymorphisms and treatment outcomes of patients with malignant mesothelioma treated with gemcitabine-platinum combination chemotherapy

INTRODUCTION

Genetic polymorphisms that affect DNA repair capacity can modulate the efficacy and toxicity of cytotoxic agents. Therefore, the aim of our study was to evaluate the influence of genetic variability in DNA repair genes on treatment outcome in patients with malignant mesothelioma (MM) treated with gemcitabine-platinum combination chemotherapy.

METHODS

In total, 109 patients with MM were genotyped for 10 polymorphisms in XRCC1, NBN, RAD51, and XRCC3 genes. The influence of selected polymorphisms on tumor response and occurrence of treatment-related toxicity was determined by logistic regression analysis, whereas their influence on survival was estimated by Cox proportional hazards model.

RESULTS

There were no associations between the investigated polymorphisms and tumor response, but we observed a significant association between XRCC1 399Gln allele and reduced overall survival (hazards ratio = 1.70; 95% confidence interval [CI] 1.06-2.73; p = 0.028). Interaction between XRCC1 399Gln allele and C-reactive protein levels revealed that carriers of at least one XRCC1 399Gln allele with C-reactive protein levels above median had significantly shorter overall survival time compared with other patients (12.9 months versus 25.3 months, log-rank p < 0.001). We also observed an association between XRCC1 399Gln and lower frequency of leukopenia (odds ratio [OR] = 0.25; 95% CI 0.09-0.67; p = 0.006), neutropenia (OR = 0.24; 95% CI 0.09-0.68; p = 0.007), and thrombocytopenia (OR = 0.27; 95% CI 0.09-0.84; p = 0.024). In addition, NBN 3474A>C, XRCC3 -316A>G, and Thr241Met polymorphisms showed significant associations with treatment-related toxicity.

CONCLUSIONS

Our results support the hypothesis that DNA repair gene polymorphisms, particularly XRCC1 Arg399Gln, may modify the response to gemcitabine-platinum combination chemotherapy and, for the first time, show this effect in patients with MM.

The effects of ERCC1 expression levels on the chemosensitivity of gastric cancer cells to platinum agents and survival in gastric cancer patients treated with oxaliplatin-based adjuvant chemotherapy

Excision repair cross-complementing 1 (ERCC1) is reported to be involved in the sensitivity of cancer cells to platinum-based chemotherapy. The present study was designed to evaluate the effects of ERCC1 expression on the chemosensitivity of platinum agents in gastric cancer cell lines, and on survival in gastric cancer patients treated with surgery followed by oxaliplatin-based adjuvant chemotherapy. ERCC1 expression levels were measured by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot analysis, respectively. The chemosensitivity of a series of gastric cancer cell lines to platinum agents in vitro was evaluated using CellTiter 96 Aqueous One Solution Cell Proliferation Assay kit. The apoptotic effect of the drugs was evaluated by double staining with Annexin-V-fluorescein isothiocyanate (FITC) and propidium iodide (PI). The results demonstrated that the expression levels of ERCC1 mRNA were correlated with the chemosensitivity of platinum agents, and depletion of ERCC1 sensitized the relatively resistant MKN45 cells to cisplatin and oxaliplatin. Univariate analyses revealed that patients with low ERCC1 levels had longer relapse-free survival (RFS) and overall survival (OS) than those with high ERCC1 levels (median RFS, 18 vs. 7 months, P=0.001; median OS, 27 vs. 11 months, P=0.001). Multivariate analyses suggested that high ERCC1 expression is an independent prognostic marker of poor RFS [hazard ratio (HR), 2.16; 95% confidence interval (CI), 1.09–4.25; P= 0.026] and OS (HR, 2.21; 95% CI, 1.07–4.55; P=0.031). These results suggest that overexpression of ERCC1 is correlated with platinum drug resistance in gastric cancer cells, and that depletion of ERCC1 sensitizes gastric cancer cell lines to cisplatin and oxaliplatin. Gastric cancer patients with low levels of ERCC1 expression demonstrate a benefit from oxaliplatin-based adjuvant chemotherapy.

Predictive value of XRCC1 gene polymorphisms on platinum-based chemotherapy in advanced non-small cell lung cancer patients: a systematic review and meta-analysis

PURPOSE

Published data have shown conflicting results about the relationship between X-ray repair cross-complementing group 1 (XRCC1) gene polymorphisms (Arg399Gln and Arg194Trp) and clinical outcome of platinum-based chemotherapy in patients with advanced non-small cell lung cancer (NSCLC). A meta-analysis is needed to provide a systematic review of the published findings.

EXPERIMENTAL DESIGN

We conducted a systematic review and meta-analysis to evaluate the predictive value of XRCC1 gene polymorphisms on clinical outcome up to October 1, 2010. The quality of each study was scored on the basis of predefined criteria.

RESULTS

A total of 13 eligible follow-up studies met all the inclusion criteria. The XRCC1194Trp allele was found to be significantly associated with a favorable response rate relative to 194Arg [Trp vs. Arg: OR, 1.88; 95% confidence interval (CI), 1.48-2.38]. XRCC1399Gln was less favorably associated with both response rate (Gln vs. Arg: OR, 0.67; 95% CI, 0.52-0.87) and overall survival (Gln vs. Arg: HR, 1.30; 95% CI, 1.04-1.63) than 399Arg in analyses using all available studies; but these associations became insignificant when only high-quality studies were used.

CONCLUSION

These findings suggest a predictive role for XRCC1 gene polymorphisms in clinical outcome. However, the role of 399Gln could be considered controversial because its impact on clinical outcome was insignificant in high-quality studies. These findings show the importance of establishing suitable criteria, including genetic epidemiologic, phenotypic, and clinical criteria, to improve quality control of study design and methods in pharmacogenomic studies related to XRCC1 gene polymorphism.

Role of the RAD51 G172T polymorphism in the clinical outcome of cervical cancer patients under concomitant chemoradiotherapy

INTRODUCTION

Cervical cancer is one of the most common cancers diagnosed in women worldwide. Mammalian cells are constantly exposed to a wide variety of genotoxic agents from both endogenous and exogenous sources. The RAD51 protein is required for meiotic and mitotic recombination and plays a central role in homology-dependent recombinational repair of double-strand breaks (DSBs). Given the functional relevance of the DNA repair system on carcinogenesis, potential associations between genetic polymorphisms of DNA repair genes, cancer risk and response to therapy have been intensively evaluated. This is the first study evaluating the role of the RAD51 G172T genetic variants in cancer prognosis and clinical outcome of cervical cancer patients.

MATERIAL AND METHODS

We analyzed RAD51 G172T polymorphism genotypes in cervical cancer patients who underwent a platinum-based chemotherapy in combination with radiotherapy. Genotyping was performed by Taqman™ Allelic Discrimination methodology.

RESULTS AND DISCUSSION

Concerning the overall survival rates found using Kaplan-Meier method and Log Rank Test, we observed that the mean survival rates were statistically different according to the patients RAD51 genotypes. The group of patients carrying the T allele present a higher mean survival rate than the other patients (102.3months vs. 86.4months, P=0.020). Using the Cox regression analysis, we found an increased overall survival time for T-carrier patients, when compared with GG genotype, with tumor stage, age and presence of lymph nodes as covariates [hazard ratio (HR), 0.373; 95% CI, 0.181-0.770; P=0.008]. Among patients (n=193), RAD51 genotype frequency distributions were not under the influence of clinicopathologic characteristics, namely, treatment response (P=0.508), recurrence (P=0.150) and tumor stage (P=0.250).

CONCLUSIONS

This is the first study evaluating the role of the RAD51 G172T genetic variants in cancer prognosis and clinical outcome of cervical cancer patients. Our results indicate an influence of the RAD51 genetic variants in overall survival of cervical cancer. Thereby, RAD51 G172T genotypes may provide additional prognostic information in cervical cancer patients who underwent cisplatin-based chemotherapy in combination with radiotherapy.

[Effect of the XRCC1 and XRCC3 genetic polymorphisms on the efficacy of platinum-based chemotherapy in patients with advanced non-small cell lung cancer]

背景与目的

DNA修复基因多态性预测铂类药物化疗敏感性对非小细胞肺癌(non-small cell lung cancer, NSCLC)个体化治疗具有重要意义。本研究旨在探讨X线修复交错互补基因1(X-ray repair cross complementing gene 1, XRCC1)和X线修复交错互补基因3(X-ray repair cross complementing gene 3, XRCC3)单核苷酸多态性与晚期NSCLC患者对铂类药物化疗疗效的关系。

方法

采用PCR-RFLP方法检测130例以含铂方案化疗的晚期NSCLC患者外周血DNA中XRCC1 Arg194 Trp、Arg399 Gln和XRCC3 Thr241 Met基因多态性, 分析其基因型与化疗疗效的关系。

结果

130例晚期NSCLC患者采用含铂方案化疗2个周期后, 化疗总有效率为33.8%。XRCC1 194和399基因多态性与铂类药物化疗敏感性相关, 而XRCC3 241基因多态性与化疗敏感性无关(P=0.145)。携带至少1个XRCC1 194 Trp等位基因者化疗有效率至少是携带Arg/Arg基因型患者的2.5倍(42.1% vs 22.2%, OR=2.545, 95%CI:1.159-5.590, P=0.020)。携带XRCC1 399 Arg/Arg基因型者的化疗有效率为45.5%, 明显高于携带至少1个Gln等位基因者(21.9%)(OR=0.336, 95%CI:0.156-0.722, P=0.005)。XRCC1 194和399基因多态性之间存在联合作用, 同时携带至少1个XRCC1 194 Trp等位基因和399 Arg/Arg基因型者的化疗有效率明显高于同时携带194 Arg/Arg和399 Arg/Gln基因型者(44.4% vs 18.8%, OR=3.467, 95%CI:1.223-9.782, P=0.019)。XRCC1和XRCC3基因多态性在化疗敏感性方面存在一定的联合作用, 携带至少1个XRCC1 194 Trp等位基因和399 Arg/Arg野生型基因同时又携带XRCC3 241 Thr/Met基因型者的化疗有效率明显高于其它基因型携带者。

结论

XRCC1和XRCC3的多态联合可能与晚期NSCLC患者对铂类药物化疗疗效具有相关性。

Association between DNA-repair polymorphisms and survival in pancreatic cancer patients treated with combination chemotherapy

AIM

This multicenter study evaluated the association of 11 candidate polymorphisms in eight genes with outcome of pancreatic cancer patients treated with the equivalent polychemotherapeutic regimens: cisplatin/epirubicin/capecitabine/gemcitabine, cisplatin/docetaxel/capecitabine/gemcitabine and gemcitabine/capecitabine plus epirubicin/cisplatin intra-arterial infusion.

PATIENTS & METHODS

Towards this end, polymorphisms were assessed in DNA from 122 pancreatic cancer stage-III/IV patients, and their associations with toxicity/response and progression-free survival (PFS) and overall survival were evaluated using Pearson-χ(2) and log-rank test.

RESULTS

Patients harboring XPD Gln751Gln, XPD Asp312Asn + Asn312Asn or XRCC1 Arg399Gln + Gln399Gln genotypes had a worse prognosis. XPD Gln751Gln (hazard ratio: 1.9; p = 0.003), as well as a combination of over two risk genotypes (hazard ratio: 2.7; p < 0.001), emerged as independent predictors for death risk at multivariate analysis. No correlations were observed with toxicity. Conversely, XPD Gln751Gln was associated with shorter PFS, while the lack of association with overall survival/PFS in gemcitabine monotherapy-treated patients suggested its role only for platinum-based regimens.

CONCLUSION

Polymorphisms of DNA-repair genes appear to be candidate biomarkers of primary resistance to gemcitabine/cisplatin-based polychemotherapeutic regimens. The relatively small sample size, coupled with the retrospective and exploratory design of the present study, imply that these results should be considered as hypothesis generators, and should be further evaluated in larger and adequately designed retrospective/prospective studies.

Prognostic significance of ERCC1 expression in resected non small cell lung carcinoma

BACKGROUND AND AIM

The effects of DNA repair pathway on survival were assessed by measuring the tumoral excision repair cross complementation 1 (ERCC1) expression in patients with resected non-small cell lung carcinoma (NSCLC). We aimed to determine the prognostic and predictive significance of ERCC1 in patients with completely resected NSCLC.

METHODS

Immunohistochemistry (IHC) was used to assess the expression of ERCC1 in resected lung tumor samples obtained from 98 patients untreated without pre- or post-operative chemotherapy and/or radiotherapy. The median H score was used as a cut-off for ERCC1 IHC. Univariate and multivariate analyses were performed for factors influencing patient survival.

RESULTS

The 5-year survival rates of patients for ERCC1 positive expression and ERCC1 negative expression were 76% and 49%, respectively; this difference was statistically significant (p = 0.004). Subsequent multivariate analysis suggested that ERCC1 expression (adjusted hazard ratio for death, 0.38; 95% CI, 0.18 to 0.78; p = 0.008) and pathological stage (2.2; 95% CI, 1.09 to 4.5; p = 0.027) were both independent prognostic factors.

CONCLUSION

The level of ERCC1 expression in tumors a strong predictor of survival in resected NSCLC patients untreated without pre- or post-operative chemotherapy and/or radiotherapy.

Systematic evaluation of genetic variants in three biological pathways on patient survival in low-stage non-small cell lung cancer

INTRODUCTION

Studies from selected candidate genes suggest that single-nucleotide polymorphisms (SNPs) involved in glutathione metabolism, DNA repair, or inflammatory responses may affect overall survival (OS) in stages I to II or low-stage non-small cell lung cancer (LS-NSCLC); however, results are inconclusive. In this study, we took a systematic pathway-based approach to simultaneously evaluate the impact of genetic variation from these three pathways on OS after LS-NSCLC diagnosis.

METHODS

DNA from 647 patients with LS-NSCLC was genotyped for 480 SNPs (tag-SNPs) tagging 57 genes from the three candidate pathways. Associations of tag-SNPs with OS were assessed at the individual SNP and whole gene levels, adjusting for age, tumor stage, surgery type, and adjuvant therapy. The genotype combinations of the SNPs associated with OS were also estimated.

RESULTS

Among the 412 tag-SNPs that were successfully genotyped and passed quality assessments, 28 showed association with OS (p < 0.05). Two of the 28 were estimated to have less than a 20% chance of being false positives (rs3768490 in GSTM5: p = 1.32 × 10, q = 0.06; rs1729786 in ABCC4: p = 9.25 × 10, q = 0.20). Gene-based analysis suggested that in addition to GSTM5 and ABCC4, variation in two other genes, PTGS2 and GSTA2, was also associated with OS.

CONCLUSIONS

We describe further evidence that variations in genes involved in the glutathione and inflammatory response pathways are associated with OS in patients with LS-NSCLC. Further studies are warranted to verify our findings and elucidate their functional mechanisms and clinical utility leading to improved survival for patients with lung cancer.

Lung cancer in women: the differences in epidemiology, biology and treatment outcomes

Although the prevalence of lung cancer in men has been decreasing, it has been increasing in women. Without a doubt, lung cancer is a major health problem for women in the USA, not only owing to its high incidence rate but, more alarming, the high mortality rate. Lung cancer kills more women each year than breast, ovarian and uterine cancers combined. One of the most important risk factors for the development of lung cancer in both men and women is cigarette smoking. Unfortunately, the prevalence of smoking among women has increased significantly since 1980, which is a major concern as epidemiologic data suggest that women may be more susceptible to developing lung cancer than men. Many will argue, however, that after adjusting for tobacco exposure, some studies have failed to show that women are at a higher risk for developing lung cancer. Indeed, the increased risk of lung cancer in women remains controversial. There is, however, little controversy to the fact that the biology of lung cancer differs between the sexes. This paper summarizes the explanations for the sex differences in lung cancer, including differences in molecular abnormalities, growth factor receptors, hormonal influences, differences in cytochrome P-450 enzymes and DNA repair capacity, as well as variations in treatment outcomes.

Potentially functional polymorphisms in DNA repair genes and non-small-cell lung cancer survival: a pathway-based analysis

To assess systematically whether potentially functional polymorphisms in DNA repair genes influence the clinical behavior of non-small-cell lung cancer (NSCLC), we examined the impact of a comprehensive panel of 218 signal nucleotide polymorphisms (SNP) in 50 candidate DNA repair genes on overall survival of NSCLC in a case-cohort of 568 lung cancer patients. SNPs associated with lung cancer prognosis primarily mapped to 14 genes in different repair pathways, and 6 SNPs were remained in the final model after multivariate stepwise Cox regression analysis: ATM rs189037; MRE11A rs11020802; ERCC2 rs1799793; MBD4 rs140693; XRCC1 rs25487, and PMS1 rs5742933. In the combined analysis of these 6 SNPs, an increasing number of unfavorable loci was associated with a poorer prognosis (P for trend: <0.0001) and patients having 2-4 unfavorable loci had a 1.99-fold elevated risk of death 95% confidence interval (CI) = 1.58-2.50, compared with those carrying 0-1 unfavorable loci, and this elevated risk was more evident among stages I-II patients (hazard ratio = 3.04, 95% CI = 1.86-4.98, P for heterogeneity: 0.07). Furthermore, a significant effect of SNPs in nucleotide excision repair pathway on lung cancer survival was observed among 185 stages III-IV patients treated with platinum-based chemotherapy without surgical operation: XPC rs2228000 (Ala499Val; P = 0.002) and ERCC1 rs11615 (Asn118Asn; P = 0.012). Our data indicate that potentially functional polymorphisms in DNA repair genes may serve as candidate prognostic markers of clinical outcome of NSCLC.

Influence of polymorphisms in MTHFR 677 C→T, TYMS 3R→2R and MTR 2756 A→G on NSCLC risk and response to platinum-based chemotherapy in advanced NSCLC

AIMS

Genetic factors may contribute to individual differences in cancer susceptibility, drug efficacy and toxicity. This study was designed to investigate the effects of the polymorphisms of methylenetetrahydrofolate reductase 677 C→T (MTHFR 677 C→T), thymidylate synthase (TYMS 3R→2R),and methionine synthase 2756 A→G (MTR 2756 A→G) on the risk of lung cancer and response to platinum-based chemotherapy in advanced non-small-cell lung cancer (NSCLC).

MATERIALS & METHODS

We conducted a case-control study involving 438 NSCLC cases (including 101 follow-up cases) and 641 healthy controls in North China.

RESULTS & CONCLUSION

Using a genetic model analysis, the polymorphism MTHFR 677 C→T showed a significantly increased risk for NSCLC in women but not in men, which was observed in the codominant model (CT vs CC adjusted odds ratio [OR] = 2.46; 95% confidence interval [CI]: 1.37-4.42; p = 0.003; TT vs CC adjusted OR: 2.04; 95% CI: 1.09-3.81; p = 0.03) and the dominant model (CT + TT vs CC adjusted OR: 2.30; 95% CI: 1.31-4.05; p = 0.004). In addition, we found that patients with the MTHFR 677 TT genotype showed a better response to platinum-based chemotherapy in the recessive model (TT vs CT + CC adjusted OR: 0.24; 95% CI: 0.09-0.68; p = 0.007), the generalized OR was 0.44 (0.22-0.88; p = 0.04). There were no significant associations of the polymorphisms of TYMS 3R→2R or MTR 2756 A→G with the risk of NSCLC or response to platinum-based chemotherapy in advanced NSCLC in any genetic model. Our results suggest that genetic polymorphisms of MTHFR 677 C→T may contribute to NSCLC development in Chinese women and could also influence treatment response for advanced NSCLC patients with platinum-based chemotherapy. Further studies with larger sample sizes are required to validate this association.

Assays to determine DNA repair ability

DNA repair is crucial to the integrity of the human genome since mammalian cells are continuously exposed to different chemical and physical genotoxic agents. To counteract the lesions induced by these agents, organisms have developed a number of highly conserved repair mechanisms involving numerous protein complexes grouped in several different repair pathways. The importance of studying the individual capacity to repair DNA damage lies in the observation that deficient repair mechanisms of the genome have been linked to the presence of large number of diseases and cancer, and alterations in these mechanisms may also alter the susceptibility of individuals exposed to a particular mutagen. This review focused on the current knowledge of different assays developed to evaluate DNA repair capacity (DRC). These assays, which are grouped into five major categories, have been successfully applied in (1) in vitro studies, (2) epidemiological studies in patients with cancer or other different pathologies, and (3) environmentally or occupationally exposed populations. Nevertheless, some of the limitations include high interlaboratory variability and difficulty to implement the assays on a large scale. The selection of an adequate DRC assay needs to be made on the basis of the objective raised for its application and taking into account a number of determining factors, namely, (1) speed and cost, (2) type of DNA repair to be evaluated, and (3) sample availability.

Assessment of XPD Lys751Gln and XRCC1 T-77C polymorphisms in advanced non-small-cell lung cancer patients treated with platinum-based chemotherapy

Polymorphisms in DNA repair genes were thought to represent important determinants of platinum drug efficacy. This study tested whether XPD Lys751Gln and XRCC1 T-77C polymorphisms were associated with survival in platinum-treated patients with advanced non-small-cell lung cancer (NSCLC). In this study, 199 advanced NSCLC patients with platinum-based chemotherapy were recruited. During the median 26.5 months of follow-up, patients with the XPD 751Lys/Lys genotype had a median survival time of 17.0 months (95% CI, 14.5-19.6 months), not much longer than those carried Lys/Gln heterozygote (12.0 months; 95% CI, 3.4-20.6 months; log-rank test, P=0.542). In Cox proportional hazards model, no significant associations were found between XPD Lys751Gln polymorphism and survival. For XRCC1 T-77C polymorphism, the median survival of patients with TC+CC genotype (18 months; 95% CI, 13.5-22.5 months) was similar to those with the TT genotype (16.0 months; 95% CI, 13.3-18.7 months; log-rank test, P=0.399). XRCC1 T-77C polymorphism was not associated with survival in Cox proportional hazards model. Additionally, the analysis for combination of these two polymorphisms also showed no prognostic significance for NSCLC. Our findings indicated that neither XPD Lys751Gln nor XRCC1 T-77C could be genetic determinant for prognosis of advanced NSCLC patients treated with platinum-based chemotherapy.

Predictive value of ERCC1 and XPD polymorphism in patients with advanced non-small cell lung cancer receiving platinum-based chemotherapy: a systematic review and meta-analysis

The published data on the predictive value of polymorphism of ERCC1 and XPD in patients with advanced non-small cell lung cancer receiving platinum-based chemotherapy are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. Relevant studies were identified by searching the Medline, Embase, CNKI and American Society of Clinical Oncology abstract databases. Inclusion criteria were patients with advanced NSCLC, received platinum-based chemotherapy, evaluation of polymorphism of ERCC1 and XPD and overall response rate (ORR). A total of 12 studies were included in this meta-analysis. For studies evaluating ERCC1 polymorphism at codon 118, the ORR for the wild-type C/C genotype versus the heterozygous C/T and T/T genotype was 2.17 (95% confidence interval (CI), 1.43-3.33; P = 0.000). For studies evaluating XPD Asp312Asn and XPD Lys751Gln, the pooled OR was 1.33 (95% CI, 0.92-1.91; P = 0.13) and 1.02 (95% CI, 0.72-1.45; P = 0.915), respectively. The results indicated that platinum-based chemotherapy sensitivity was significantly associated with polymorphism of ERCC1 C118T. However, XPD Asp312Asn and XPD Lys751Gln were not predictive makers for platinum-based chemotherapy in patients with advanced NSCLC.

Association between polymorphisms in DNA repair genes and survival of non-smoking female patients with lung adenocarcinoma

Background

Excision repair cross-complementing group 1 (ERCC1) and group 2 (ERCC2), and X-ray repair cross-complementing group 1 (XRCC1) proteins play important roles in the repair of DNA damage and adducts. Single nucleotide polymorphisms (SNPs) of DNA repair genes are suspected to influence treatment effect and survival of cancer patients. This study aimed to investigate the relationship between polymorphisms in ERCC2, ERCC1 and XRCC1 genes and survival of non-smoking female patients with lung adenocarcinoma.

Methods

We used polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method to evaluate SNPs in ERCC2, ERCC1 and XRCC1 genes among 257 patients.

Results

The overall median survival time (MST) was 13.07 months. Increasing numbers of either ERCC1 118 or XRCC1 399 variant alleles were associated with shorter survival of non-smoking female lung adenocarcinoma patients (Log-rank P < 0.001). The adjusted hazard ratios (HRs) for individuals with CT or TT genotype at ERCC1 Asn118Asn were 1.48 and 2.67 compared with those with CC genotype. For polymorphism of XRCC1 399, the HRs were 1.28 and 2.68 for GA and AA genotype. When variant alleles across both polymorphisms were combined to analysis, the increasing number of variant alleles was associated with decreasing overall survival. Using the stepwise Cox regression analysis, we found that the polymorphisms in ERCC1 and XRCC1, tumor stage and chemotherapy or radiotherapy status independently predicted overall survival of non-smoking female patients with lung adenocarcinoma.

Conclusions

Genetic polymorphisms in ERCC1 and XRCC1 genes might be prognostic factors in non-smoking female patients with lung adenocarcinoma.

Emodin enhances cisplatin-induced cytotoxicity via down-regulation of ERCC1 and inactivation of ERK1/2

Emodin, a tyrosine kinase inhibitor, is a natural anthraquinone derivative found in the roots and rhizomes of numerous plants; it exhibits an anticancer effect on many malignancies. The most important chemotherapeutic agent for patients with advanced non-small cell lung cancer (NSCLC) is a platinum-containing compound such as cisplatin or carboplatin. The molecular mechanism underlying decreased NSCLC cell viability after treatment with emodin and cisplatin is unclear. Therefore, the aim of this study was to assess the cytotoxic effect of combined emodin and cisplatin on NSCLC cell lines and to clarify underlying molecular mechanisms. Exposure of human NSCLC cells to emodin decreased cisplatin-elicited ERK1/2 activation and ERCC1 protein induction by increasing instability of ERCC1 protein. Cisplatin alone did not affect expression of ERCC1 mRNA. However, emodin alone or combined with cisplatin significantly decreased expression of ERCC1 mRNA levels. Enhancement of ERK1/2 activation by transfection with constitutively active MKK1/2 (MKK1/2-CA) vector increased ERCC1 protein levels and protein stability, as well as increasing viability of NSCLC cells treated with emodin and cisplatin. In contrast, blocking ERK1/2 activation by U0126 (an MKK1/2 inhibitor) decreased cisplatin-elicited ERCC1 expression and enhanced cisplatin-induced cytotoxicity. Depletion of endogenous ERCC1 expression by si-ERCC1 RNA transfection significantly enhanced cisplatin's cytotoxic effect. In conclusion, ERCC1 protein protects NSCLC cells from synergistic cytotoxicity induced by emodin and platinum agents. Further investigation of combined emodin and cisplatin may lead to novel therapy in the future for NSCLC through down-regulating expression of ERCC1.

[ERCC1 and RRM1 genes in lung cancer]

In lung cancer, expressive survival has not yet been achieved in non surgical stages. Non-small cell lung cancer (NSCLC) patients are treated with platinum and other drugs. To choose these agents we can actual ly define predictive biomarkers to preview therapeutic response. A literature revision was done in order to define the role of ERCC1 e RRM1 genes in the response to chemotherapy based in platinum and gemcitabine respectively. The expression of these genes is faced as a predictive marker to the chemotherapy response in patients with adenocarcinomas and squamous cell carcinomas, providing a personalized therapy. Published data supports this behaviour and is useful to individualize therapy accordingly to individual levels of ERCC1 which are modified by genetic mutations. Polymorphisms in codons 118 C/T and C8092A, seem to influence the carcinogenesis, cytostatic resistance, survival and even the prognosis. Clinical and laboratorial trials showed that high expression of RRM1 gene in NSCLC has impact in the tumoral phenotype. Patients having done surgical resection and presenting high expression of RRM1 have better survival than those with lower expression. However, patients with advanced NSCLC and treated with chemotherapy with gemcitabine and cisplatin appear to have a poor outcome if the tumor express elevated levels of RRM1 gene.

Statistically significant association of the single nucleotide polymorphism (SNP) rs13181 (ERCC2) with predisposition to Squamous Cell Carcinomas of the Head and Neck (SCCHN) and Breast cancer in the north Indian population

Background

Non-synonymous single nucleotide polymorphisms (SNPs) within vital DNA repair genes may cause reduction of activity leaving the genome unrepaired resulting in genomic instability and cancer.

Materials and methods

The present endeavour involved study on the association of the SNP rs13181 (Lys751Gln/A18911C) in the Nucleotide Excision Repair (NER) pathway gene ERCC2 (excision repair cross-complementing rodent repair deficiency, complementation group 2) with the risks of Squamous Cell Carcinomas of the Head and Neck (SCCHN) and Breast cancer using a case-control based association study among 685 (400 controls and 285 SCCHN-affected cases) and 395 (227 normal healthy female controls and 168 breast cancer cases) ethnically-matched samples, respectively from north India using Polymerase Chain Reaction followed by Restriction Fragment Length Polymorphism (PCR-RFLP) analysis.

Results

Results showed significant association of rs13181 homozygous mutant (CC) [Odds Ratio (OR) 4.412, 95% Confidence Interval (CI) 2.413 to 8.068], heterozygous (AC) (OR 2.086, 95% CI 1.246 to 3.492) and combined mutant (AC + CC) (OR 2.672, 95% CI 1.647 to 4.334) genotypes with predisposition to Breast cancer. Statistically significant increase in SCCHN risk was also associated with the mutant genotypes of rs13181 (ERCC2), viz. homozygous mutant (CC) (OR 1.680, 95% CI 1.014 to 2.784), heterozygous (AC) (OR 1.531, 95% CI 1.092 to 2.149) and combined mutant (AC + CC) (OR 1.560, 95% CI 1.128 to 2.158) genotypes.

Conclusion

The results of this case-control study indicate that the polymorphism rs13181 might be a risk factor for predisposition towards SCCHN and breast cancer among north Indian subpopulations.

The FAS ligand promoter polymorphism, rs763110 (-844C>T), contributes to cancer susceptibility: evidence from 19 case-control studies

The potentially functional polymorphism, rs763110 (-844C>T), in the promoter region of the FAS ligand (FASL) gene, has been implicated in cancer risk, but individually published studies show inconclusive results. To derive a more precise estimation of the association between the FASL rs763110 and risk of cancer, we performed a meta-analysis of 19 published studies that included 11,105 cancer cases and 11,372 controls. We used odds ratios (ORs) and 95% confidence intervals (CIs) to assess the strength of the associations. Overall, the rs763110 CT and TT variant genotypes were associated with a significantly reduced cancer risk of all cancer types in different genetic models (homozygote comparison: OR=0.80, 95% CI: 0.68-0.95, P(heterogeneity)=0.001; heterozygote comparison: OR=0.82, 95% CI: 0.72-0.95, P(heterogeneity)<0.001; dominant model comparison: OR=0.82, 95% CI: 0.71-0.94, P(heterogeneity)<0.001; and recessive model comparison: OR=0.88, 95% CI: 0.81-0.96, P(heterogeneity)=0.074). In the stratified analyses, the risk remained for studies of the smoking-related cancers and Asian populations, or population-based studies in all the genetic models. Although some modest bias could not be eliminated, this meta-analysis suggests that the FASL rs763110 T allele has a possible protective effect on cancer risk.

Germline genetic variations in drug action pathways predict clinical outcomes in advanced lung cancer treated with platinum-based chemotherapy

PURPOSE

Genetic polymorphisms contribute to interindividual variation in drug response. However, a single polymorphism is likely to exhibit a modest effect. Therefore, we applied a pathway-based approach to evaluate the cumulative effect of multiple polymorphisms on clinical outcome of patients with non-small cell lung cancer.

METHODS

We genotyped 25 functional polymorphisms in 16 key genes involved in cisplatin metabolism and action and evaluated their associations with overall survival in 229 non-small cell lung cancer patients receiving first-line cisplatin-based chemotherapy.

RESULTS

Several biologically plausible main effects were identified in individual analysis. More importantly, when six polymorphisms in nucleotide excision repair genes were analyzed jointly, a significant trend of reduced risk of death with decreasing number of putative unfavorable genotypes was observed (P for trend < 0.001 and log rank P < 0.001). Survival tree analysis revealed potential higher-order gene-gene interactions and categorized subgroups with dramatically different survival experiences, based on distinct genotype profiles. The median survival time was 78.5 months for terminal node 1 in the low-risk group, 15.1 months for terminal node 10 in the medium-risk group, and 6.7 months for terminal node 9 in the high-risk group (log rank P < 0.001). We also constructed a prediction hazard model. The area under the curve increased from 0.71 (using clinical variables only) to 0.84 (using clinical, epidemiological, and genetic variations from survival tree analysis).

CONCLUSION

Our results highlight the clinical potential of taking a pathway-based approach and using survival tree analytic approach to identify subgroups of patients with distinctly differing outcomes.

Lung cancer and women

In the early 1900s, lung cancer was a rare malignancy in women, but starting from the 1960s it has progressively reached epidemic proportions, surpassing breast cancer in 1987 and becoming the leading cause of cancer deaths in many countries. Retrospective data show that the 5-year survival rate for women who have lung cancer is 15.6%, compared with 12.5% for men, and this improved survival could have important implications in the design and interpretation of lung cancer trials. Women have major responses to therapy regardless of stage, therapeutic modalities or histology. The increase of lung cancer incidence among women is reflected in their clinical trial participation, causing a survival improvement and suggesting the need of stratification by sex in future studies. No specific drugs for women with lung cancer are currently available, but researchers are devoting energies in this area in order to better understand the implication of gender differences in epidemiology, pathogenesis, prognosis and tumor response.