Genetic Polymorphisms of DNA Repair Pathways in Sporadic Colorectal Carcinogenesis

Enhancing cisplatin drug sensitivity through PARP3 inhibition: The influence on PDGF and G-coupled signal pathways in cancer

Drug resistance poses a significant challenge in cancer treatment despite the clinical efficacy of cisplatin. Identifying and targeting biomarkers open new ways to improve therapeutic outcomes. In this study, comprehensive bioinformatic analyses were employed, including a comparative analysis of multiple datasets, to evaluate overall survival and mutation hotspots in 27 base excision repair (BER) genes of more than 7,500 tumors across 23 cancer types. By using various parameters influencing patient survival, revealing that the overexpression of 15 distinct BER genes, particularly PARP3, NEIL3, and TDG, consistently correlated with poorer survival across multiple factors such as race, gender, and metastasis. Single nucleotide polymorphism (SNP) analyses within protein-coding regions highlighted the potential deleterious effects of mutations on protein structure and function. The investigation of mutation hotspots in BER proteins identified PARP3 due to its high mutation frequency. Moving from bioinformatics to wet lab experiments, cytotoxic experiments demonstrated that the absence of PARP3 by CRISPR/Cas9-mediated knockdown in MDA-MB-231 breast cancer cells increased drug activity towards cisplatin, carboplatin, and doxorubicin. Pathway analyses indicated the impact of PARP3 absence on the platelet-derived growth factor (PDGF) and G-coupled signal pathways on cisplatin exposure. PDGF, a critical regulator of various cellular functions, was downregulated in the absence of PARP3, suggesting a role in cancer progression. Moreover, the influence of PARP3 knockdown on G protein-coupled receptors (GPCRs) affects their function in the presence of cisplatin. In conclusion, the study demonstrated a synthetic lethal interaction between GPCRs, PDGF signaling pathways, and PARP3 gene silencing. PARP3 emerged as a promising target.

MSH7 confers quantitative variation in pollen fertility and boosts grain yield in maize

Fertile pollen is critical for the survival, fitness, and dispersal of flowering plants, and directly contributes to crop productivity. Extensive mutational screening studies have been carried out to dissect the genetic regulatory network determining pollen fertility, but we still lack fundamental knowledge about whether and how pollen fertility is controlled in natural populations. We used a genome-wide association study (GWAS) to show that ZmGEN1A and ZmMSH7, two DNA repair-related genes, confer natural variation in maize pollen fertility. Mutants defective in these genes exhibited abnormalities in meiotic or post-meiotic DNA repair, leading to reduced pollen fertility. More importantly, ZmMSH7 showed evidence of selection during maize domestication, and its disruption resulted in a substantial increase in grain yield for both inbred and hybrid. Overall, our study describes the first systematic examination of natural genetic effects on pollen fertility in plants, providing valuable genetic resources for optimizing male fertility. In addition, we find that ZmMSH7 represents a candidate for improvement of grain yield.

The Impact of SNP-Induced Amino Acid Substitutions L19P and G66R in the dRP-Lyase Domain of Human DNA Polymerase β on Enzyme Activities

Base excision repair (BER), which involves the sequential activity of DNA glycosylases, apurinic/apyrimidinic endonucleases, DNA polymerases, and DNA ligases, is one of the enzymatic systems that preserve the integrity of the genome. Normal BER is effective, but due to single-nucleotide polymorphisms (SNPs), the enzymes themselves-whose main function is to identify and eliminate damaged bases-can undergo amino acid changes. One of the enzymes in BER is DNA polymerase β (Polβ), whose function is to fill gaps in DNA. SNPs can significantly affect the catalytic activity of an enzyme by causing an amino acid substitution. In this work, pre-steady-state kinetic analyses and molecular dynamics simulations were used to examine the activity of naturally occurring variants of Polβ that have the substitutions L19P and G66R in the dRP-lyase domain. Despite the substantial distance between the dRP-lyase domain and the nucleotidyltransferase active site, it was found that the capacity to form a complex with DNA and with an incoming dNTP is significantly altered by these substitutions. Therefore, the lower activity of the tested polymorphic variants may be associated with a greater number of unrepaired DNA lesions.

The Contribution of DNA Ligase 4 Polymorphisms to Colorectal Cancer

BACKGROUND/AIM

While numerous biomarkers associated with genetic susceptibility to colorectal cancer (CRC) have been identified and validated through epidemiological studies, the specific influence of DNA ligase 4 (Lig4) genotypes remains unexplored. This study aimed to elucidate the hitherto unexamined relationship between Lig4 genotypes and CRC risk.

MATERIALS AND METHODS

The genotypes of Lig4 rs1805388 were determined applying the polymerase chain reaction-restriction fragment length polymorphism methodology. The potential association between these genotypes and CRC risk was assessed in a Taiwanese population comprising 362 CRC cases and an equal number of age- and sex-matched controls.

RESULTS

In the genotypic analysis, the distribution of CC, CT, and TT genotypes for Lig4 rs1805388 among CRC cases was 54.7%, 38.1%, and 7.2%, respectively. This distribution was not significantly different from the controls, which exhibited genotypic frequencies of 57.2%, 36.7%, and 6.1%, respectively (p for trend=0.7314). Analysis of allelic distribution indicated that individuals carrying the T allele of Lig4 rs1805388 displayed a slightly elevated CRC risk compared to those carrying the C allele (odds ratio=1.10, 95% confidence interval=0.87-1.39, p=0.4685).

CONCLUSION

The variant genotypes of Lig4 rs1805388 may not serve as predictive markers for CRC risk in the Taiwanese population.

MLH1 rs1800734 Pathogenic Variant among Patients with Colorectal Cancer in the Lower Northeastern Region of Thailand

BACKGROUND

The -93G > A (rs1800734) polymorphism within the core promoter region of MLH1 gene is associated with MLH1 CpG island hypermethylation. This polymorphism has recently been proposed as a low penetrance variant for colorectal cancer. Many published studies have evaluated the association between the MLH1 -93G > A polymorphism and colorectal cancer risk. However, the results remain conflicting rather than conclusive. The aim of this study was to assess the association between the MLH1 -93G > A polymorphism and the risk of colorectal cancer in patients with colorectal cancer in the lower northeastern region of Thailand.

METHODS

One hundred fifty one samples from colorectal cancer patients and 100 samples from healthy control group were analyzed. Genomic DNA was extracted from white blood cell of all samples. The real-time polymerase chain reaction (qPCR) was used to demonstrate genetic polymorphism of MLH1 rs1800734.

RESULTS

This study demonstrated that the frequency of MLH1 rs1800734 in patients with colorectal cancer was higher than healthy control group. The MLH1 rs1800734 polymorphism variant AA was associated with an increased risk of colorectal cancer (p < 0.05). The MLH1 polymorphism variant AA carriers presented 1.36-folds high risk of colorectal cancer and the alcohol consumption was linked to their likelihood of developing colorectal cancer and their tumor's grade.

CONCLUSION

This study showed that MLH1 rs1800734 genotype AA was associated with colorectal cancer risk in the lower northeastern region of Thailand.

Structural, functional analysis and association of MSH6 rs1800932, rs1042821 polymorphisms with clinical outcome in North Indian lung cancer patients treated with platinum-based doublet chemotherapy

BACKGROUND

In this study, we have done structural and functional analysis of rs1800932 rs1042821 polymorphisms and tried to estimate any association of these polymorphisms with clinical outcomes in north Indian lung cancer patients.

METHODS

Genotyping of 500 lung cancer patients was completed utilizing PCR-RFLP (Polymerase chain reaction- Restriction fragment length polymorphism). MedCalc statistical software was used to calculate adjusted and unadjusted odds ratios. Various computational tools like SIFT PROVEAN are used for functional analysis. Structural analysis was completed via MODELLER and CHIMERA.

RESULTS

In our study, patients suffering from small cell lung cancer (SCLC) and harboring heterozygous genotype (AG) for MSH6 (rs1800932) polymorphism have reported a significant increase in median survival time (MST) (20.6 vs. 7.6 months, p = 0.03). Furthermore, for MSH6 rs1042821 polymorphism, patients undergoing docetaxel and carbo/cisplatin combination chemotherapeutic regimen and carrying heterogeneous genotype (CT) reported a significant increase in MST (16.6 vs.8.36 months, p = 0.03) and a corresponding decrease in hazard ratio 0.42 (95% CI= 0.18-1.03). Structural and Functional analysis of rs1042821 polymorphism revealed that it is present in the non-coding region of MSH6 protein and is significantly associated with increased overall survival.

CONCLUSIONS

These results suggest that MSH6 rs1800932 rs1042821 polymorphisms are involved in increasing the overall survival of lung cancer patients, further confirmed by computational analysis.

Role of K63-linked ubiquitination in cancer

Ubiquitination is a critical type of post-translational modifications, of which K63-linked ubiquitination regulates interaction, translocation, and activation of proteins. In recent years, emerging evidence suggest involvement of K63-linked ubiquitination in multiple signaling pathways and various human diseases including cancer. Increasing number of studies indicated that K63-linked ubiquitination controls initiation, development, invasion, metastasis, and therapy of diverse cancers. Here, we summarized molecular mechanisms of K63-linked ubiquitination dictating different biological activities of tumor and highlighted novel opportunities for future therapy targeting certain regulation of K63-linked ubiquitination in tumor.

A miR-15a related polymorphism affects NSCLC prognosis via altering ERCC1 repair to platinum-based chemotherapy

Platinum‐based chemotherapy is regarded as a preferential curative‐intent option for non‐small cell lung cancer (NSCLC), while the acquired drug resistance has become a major obstacle that limits its clinical application. Since the repair efficiency of tumour cells to platinum‐DNA adducts plays a crucial role in chemotherapy resistance, we aimed to explore whether several meaningful polymorphisms of DNA repair genes were associated with the benefits of platinum‐based chemotherapy in NSCLC patients. Firstly, six single nucleotide polymorphisms (SNPs) located in the 3'untranslated region (3'UTR) of three DNA repair genes were detected in 246 NSCLC patients receiving platinum‐based chemotherapy and analysed the correlation of these candidate SNPs with the overall survival. Cox proportional hazard model showed that NSCLC patients carrying ERCC1 rs3212986 AA genotype had a shorter overall survival compared to those with CC. Mechanistically, we performed tumour chemosensitivity assay to observe the convincing linkage of rs3212986 polymorphism with ERCC1 expression and cisplatin sensitivity. The subsequent in vitro experiments identified that rs3212986 polymorphism altered the post‐transcriptional regulation of ERCC1 via affecting the binding of miR‐15a, and further changed the sensitivity to platinum analogue. It reminded that patients carrying ERCC1 rs3212986 CC homozygote were expected to respond better to platinum‐based chemotherapy due to a lower expression of ERCC1. Compared with previous studies, our current comprehensive study suggested that rs3212986, a 3'UTR polymorphism in ERCC1, might have clinical relevance in predicting the prognosis of NSCLC patients receiving platinum‐based chemotherapy.

Genetic polymorphisms in the mismatch repair pathway (MMR) genes contribute to hematological and gastrointestinal toxicity in North Indian lung cancer patients treated with platinum-based chemotherapy

The present study investigated the relationship between MLH1, MSH2, MSH3, and MSH6 polymorphisms and toxicity due to platinum-based doublet chemotherapy for North Indian lung cancer patients. Polymerase chain reaction-restriction fragment length polymorphism technique was used to assess the polymorphism. For MSH2 IVS1 + 9G > C polymorphism variant type genotype reported a 1.4-fold increased risk of anemia (AOR = 1.4; 95% CI = 0.98-1.99; p = 0.04) and decreased risk of developing gastrointestinal toxicity (diarrhea) (AOR = 0.53; 95% CI = 0.28-1.01; p = 0.04). Further, we also reported a 10-fold increased risk of developing severe grade anorexia in combined genotype (GC + CC) (AOR = 9.18; 95% CI = 0.98-86.1; p = 0.05). For MSH2 T > C/-6 polymorphism, variant type reported a 3-fold and 2-fold increased risk of developing severe grade leukopenia (AOR = 3.37; 95% CI = 1.44-7.88; p = 0.005) and neutropenia respectively (AOR = 2.23; 95% CI = 1.07-4.66; p = 0.03). For MSH3 G > A polymorphism, heterozygous (GA) and combined genotype (GA + AA) reported a 7-fold and 6-fold increased risk of developing anemia (AOR = 7.23; 95% CI = 1.51-34.6; p = 0.01, AOR = 6.39; 95% CI = 1.53-26.6; p = 0.01). Our results suggest that polymorphisms in DNA mismatch repair genes are associated with hematological, and gastrointestinal toxicities and might be considered a predictor for pretreatment evaluation in lung cancer patients.

APE1/Ref-1 Role in Inflammation and Immune Response

Apurinic/apyrimidinic endonuclease 1/redox effector factor 1 (APE1/Ref-1) is a multifunctional enzyme that is essential for maintaining cellular homeostasis. APE1 is the major apurinic/apyrimidinic endonuclease in the base excision repair pathway and acts as a redox-dependent regulator of several transcription factors, including NF-κB, AP-1, HIF-1α, and STAT3. These functions render APE1 vital to regulating cell signaling, senescence, and inflammatory pathways. In addition to regulating cytokine and chemokine expression through activation of redox sensitive transcription factors, APE1 participates in other critical processes in the immune response, including production of reactive oxygen species and class switch recombination. Furthermore, through participation in active chromatin demethylation, the repair function of APE1 also regulates transcription of some genes, including cytokines such as TNFα. The multiple functions of APE1 make it an essential regulator of the pathogenesis of several diseases, including cancer and neurological disorders. Therefore, APE1 inhibitors have therapeutic potential. APE1 is highly expressed in the central nervous system (CNS) and participates in tissue homeostasis, and its roles in neurodegenerative and neuroinflammatory diseases have been elucidated. This review discusses known roles of APE1 in innate and adaptive immunity, especially in the CNS, recent evidence of a role in the extracellular environment, and the therapeutic potential of APE1 inhibitors in infectious/immune diseases.

Genetic polymorphisms in DNA repair genes and hepatocellular carcinoma risk

Hepatocellular carcinoma (HCC) is one of the most frequent types of tumors worldwide. Its occurrence and development have been related to various risk factors, such as chronic infection with hepatitis B or C viruses and alcohol addiction. DNA repair systems play a critical role in maintaining the integrity of the genome. Defects in these systems have been related to increased susceptibility to various types of cancer. Multiple genetic polymorphisms in genes of DNA repair systems have been reported that may affect DNA repair capacity (DRC) and modulate risk to cancer. Several studies have been conducted to assess the role of polymorphisms of DNA repair genes on the HCC risk. Identifying these polymorphisms and their association with HCC risk may help to improve prevention and treatment strategies. In this study, we review investigations that evaluated the association between genetic polymorphisms of DNA repair genes and risk of HCC.

Rare Variants in the DNA Repair Pathway and the Risk of Colorectal Cancer

BACKGROUND

Inherited susceptibility is an important contributor to colorectal cancer risk, and rare variants in key genes or pathways could account in part for the missing proportion of colorectal cancer heritability.

METHODS

We conducted an exome-wide association study including 2,327 cases and 2,966 controls of European ancestry from three large epidemiologic studies. Single variant associations were tested using logistic regression models, adjusting for appropriate study-specific covariates. In addition, we examined the aggregate effects of rare coding variation at the gene and pathway levels using Bayesian model uncertainty techniques.

RESULTS

In an exome-wide gene-level analysis, we identified ST6GALNAC2 as the top associated gene based on the Bayesian risk index (BRI) method [summary Bayes factor (BF)BRI = 2604.23]. A rare coding variant in this gene, rs139401613, was the top associated variant (P = 1.01 × 10-6) in an exome-wide single variant analysis. Pathway-level association analyses based on the integrative BRI (iBRI) method found extreme evidence of association with the DNA repair pathway (BFiBRI = 17852.4), specifically with the nonhomologous end joining (BFiBRI = 437.95) and nucleotide excision repair (BFiBRI = 36.96) subpathways. The iBRI method also identified RPA2, PRKDC, ERCC5, and ERCC8 as the top associated DNA repair genes (summary BFiBRI ≥ 10), with rs28988897, rs8178232, rs141369732, and rs201642761 being the most likely associated variants in these genes, respectively.

CONCLUSIONS

We identified novel variants and genes associated with colorectal cancer risk and provided additional evidence for a role of DNA repair in colorectal cancer tumorigenesis.

IMPACT

This study provides new insights into the genetic predisposition to colorectal cancer, which has potential for translation into improved risk prediction.

New perspectives in cancer biology from a study of canonical and non-canonical functions of base excision repair proteins with a focus on early steps

Alterations of DNA repair enzymes and consequential triggering of aberrant DNA damage response (DDR) pathways are thought to play a pivotal role in genomic instabilities associated with cancer development, and are further thought to be important predictive biomarkers for therapy using the synthetic lethality paradigm. However, novel unpredicted perspectives are emerging from the identification of several non-canonical roles of DNA repair enzymes, particularly in gene expression regulation, by different molecular mechanisms, such as (i) non-coding RNA regulation of tumour suppressors, (ii) epigenetic and transcriptional regulation of genes involved in genotoxic responses and (iii) paracrine effects of secreted DNA repair enzymes triggering the cell senescence phenotype. The base excision repair (BER) pathway, canonically involved in the repair of non-distorting DNA lesions generated by oxidative stress, ionising radiation, alkylation damage and spontaneous or enzymatic deamination of nucleotide bases, represents a paradigm for the multifaceted roles of complex DDR in human cells. This review will focus on what is known about the canonical and non-canonical functions of BER enzymes related to cancer development, highlighting novel opportunities to understand the biology of cancer and representing future perspectives for designing new anticancer strategies. We will specifically focus on APE1 as an example of a pleiotropic and multifunctional BER protein.

Association Between Arg72Pro Polymorphism in TP53 and Malignant Abdominal Solid Tumor Risk in Hunan Children

Pediatric solid tumors are heterogeneous and comprise various histological subtypes. TP53, a tumor suppressor, orchestrates the transcriptional activation of anti-cancer genes. The gene coding for this protein is highly polymorphic, and its mutations are associated with cancer development. The Arg72Pro polymorphism in TP53 has been associated with susceptibility to various types of cancer. Here, in this hospital-based study, we evaluated the association of this polymorphism with susceptibility toward malignant abdominal solid tumors in children in the Hunan province of China. We enrolled 162 patients with neuroblastoma, 60 patients with Wilms' tumor, and 28 patients with hepatoblastoma as well as 270 controls. Genotypes were determined using a TaqMan assay, and the strength of the association was assessed using an odds ratio, within a 95% confidence interval identified using logistic regression models. Our results showed that the Arg72Pro polymorphism did not exhibit significant association with susceptibility toward pediatric malignant abdominal solid tumors. Stratification analysis revealed that this polymorphism exerts weak sex- and age-specific effects on Wilms' tumor and hepatoblastoma susceptibility, respectively. Overall, our results indicate that the Arg72Pro polymorphism may have a marginal effect on susceptibility toward pediatric malignant abdominal solid tumors in Hunan, and this finding warrants further confirmation.

A Qualitative Transcriptional Signature for Predicting CpG Island Methylator Phenotype Status of the Right-Sided Colon Cancer

A part of colorectal cancer which is characterized by simultaneous numerous hypermethylation CpG islands sites is defined as CpG island methylator phenotype (CIMP) status. Stage II and III CIMP−positive (CIMP+) right-sided colon cancer (RCC) patients have a better prognosis than CIMP−negative (CIMP−) RCC treated with surgery alone. However, there is no gold standard available in defining CIMP status. In this work, we selected the gene pairs whose relative expression orderings (REOs) were associated with the CIMP status, to develop a qualitative transcriptional signature to individually predict CIMP status for stage II and III RCC. Based on the REOs of gene pairs, a signature composed of 19 gene pairs was developed to predict the CIMP status of RCC through a feature selection process. A sample is predicted as CIMP+ when the gene expression orderings of at least 12 gene pairs vote for CIMP+; otherwise the CIMP−. The difference of prognosis between the predicted CIMP+ and CIMP− groups was more significantly different than the original CIMP status groups. There were more differential methylation and expression characteristics between the two predicted groups. The hierarchical clustering analysis showed that the signature could perform better for predicting CIMP status of RCC than current methods. In conclusion, the qualitative transcriptional signature for classifying CIMP status at the individualized level can predict outcome and guide therapy for RCC patients.

Polymorphisms of xenobiotic-metabolizing and transporter genes, and the risk of gastric and colorectal cancer in an admixed population from the Brazilian Amazon

Colorectal (CRC) and gastric (GC) cancers are associated with increased morbidity and mortality. Single nucleotide polymorphisms (SNPs) of xenobiotic metabolism and transporter genes may play a role in the individual responses to exposure to substances implicated in susceptibility to cancer. The investigation of the genetic variation related to the activation and detoxification of xenobiotics may thus help to clarify the prevalence of neoplasms. We analyzed the role of 30 SNPs in xenobiotic-metabolizing and transporter genes in susceptibility to CRC and GC. The study included individuals diagnosed with CRC (n = 121) and GC (n = 95), and 141 controls (non-cancer patients) from the population of Belém, in the Brazilian Amazon. The results indicated an association between the polymorphisms rs2231142 (P = 0.013; OR = 3.01; 95% CI = 1.26-7.13), in the ABCG2 gene, and rs1801159 (P = 0.03; OR = 2.35; 95% CI = 1.14-5.05), in DPYD gene, with the risk of developing GC. The polymorphism rs17116806 of the DPYD gene was found to be associated with a lower risk of developing gastric (P≤0.0001; OR = 0.043; 95% CI = 0.015-0.12) or colorectal (P≤0.0001; OR = 0.076; 95% CI = 0.33-0.18) cancers, indicating that the same variant may play a similar role in different types of cancer tissue. Additionally, the carriers of the TT genotype of the polymorphism in the ABCB1 gene (rs1128503) presented a reduced probability of developing CRC (P = 0.0001; OR = 0.16; 95% CI = 0.06-0.41) as well as GC (P = 0.007; OR = 0.27; 95% CI = 0.1-0.7). Our findings indicate that polymorphisms in xenobiotic-metabolizing and transporter genes may modulate susceptibility to colorectal and gastric cancers.

Molecular and structural characterization of disease-associated APE1 polymorphisms

Under conditions of oxidative stress, reactive oxygen species (ROS) continuously assault the structure of DNA resulting in oxidation and fragmentation of the nucleobases. When the nucleobase structure is altered, its base-pairing properties may also be altered, promoting mutations. Consequently, oxidative DNA damage is a major source of the mutation load that gives rise to numerous human maladies, including cancer. Base excision repair (BER) is the primary pathway tasked with removing and replacing mutagenic DNA base damage. Apurinic/apyrimidinic endonuclease 1 (APE1) is a central enzyme with AP-endonuclease and 3' to 5' exonuclease functions during BER, and therefore is key to maintenance of genome stability. Polymorphisms, or SNPs, in the gene encoding APE1 (APEX1) have been identified among specific human populations and result in variants of APE1 with modified function. These defects in APE1 potentially result in impaired DNA repair capabilities and consequently an increased risk of disease for individuals within these populations. In the present study, we determined the X-ray crystal structures of three prevalent disease-associated APE1 SNPs (D148E, L104R, and R237C). Each APE1 SNP results in unique localized changes in protein structure, including protein dynamics and DNA binding contacts. Combined with comprehensive biochemical characterization, including pre-steady-state kinetic and DNA binding analyses, variant APE1:DNA complex structures with both AP-endonuclease and exonuclease substrates were analyzed to elucidate how these SNPs might perturb the two major repair functions employed by APE1 during BER.

Association of DNA repair gene variants with colorectal cancer: risk, toxicity, and survival

Background

Single nucleotide polymorphisms (SNPs) in DNA repair genes have a potential clinical value in predicting treatment outcomes. In the current study, we examined the association of SNPs in the genes XRCC1-rs25487, ERCC1-rs11615, ERCC2-rs238406, and ERCC2-rs13181 with colorectal cancer (CRC) risk, relapse-free survival (RFS), overall survival (OS), and toxicity during chemotherapy.

Methods

SNPs were analysed in 590 CRC cases and 300 controls using TaqMan technology. The association of SNPs with CRC risk and toxicity during chemotherapy was analysed using Chi2 test. The Kaplan–Meier method and log-rank test was used to measure the effects of the SNPs on RFS and OS.

Results

The CC genotype of ERCC2-rs238406 and the ERCC2-rs13181 C allele were associated with a significantly increased risk of CRC. The ERCC1-rs11615 genotype T/T was associated with stomatitis in adjuvant chemotherapy (p = 0.03). Also, more patients with the ERCC2-rs13181 C allele needed dose reduction compared to patients with the A/A genotype (p = 0.02). In first line chemotherapy, more patients with the ERCC1-rs11615 C allele suffered from nausea compared to those with the T/T genotype (p = 0.04) and eye reactions and thrombocytopenia were more common in patients with the ERCC2-rs13181 C allele compared to the A/A genotype (p = 0.006 and p = 0.004, respectively). ERCC2- rs238406 C/C was also associated with a higher frequency of thrombocytopenia (p = 0.03). A shorter 5-year OS was detected in stage I & II CRC patients with the ERCC2- rs238406 C allele (p = 0.02). However, there was no significant association between the SNPs and 5-year RFS.

Conclusions

Both SNPs in ERCC2 were associated with risk of CRC as well as toxicity during first line treatment. In addition, ERCC2- rs238406 was linked to OS in early stage CRC. The ERCC1-rs11615 variant was associated with toxicity during adjuvant chemotherapy. The results add support to previous findings that SNPs in ERCC1 and ERCC2 have a prognostic and predictive value in clinical management of CRC.

A New Polygenic Model for Nonfamilial Colorectal Cancer Inheritance Based on the Genetic Architecture of the Azoxymethane-Induced Mouse Model

The azoxymethane model of colorectal cancer (CRC) was used to gain insights into the genetic heterogeneity of nonfamilial CRC. We observed significant differences in susceptibility parameters across 40 mouse inbred strains, with 6 new and 18 of 24 previously identified mouse CRC modifier alleles detected using genome-wide association analysis. Tumor incidence varied in F1 as well as intercrosses and backcrosses between resistant and susceptible strains. Analysis of inheritance patterns indicates that resistance to CRC development is inherited as a dominant characteristic genome-wide, and that susceptibility appears to occur in individuals lacking a large-effect, or sufficient numbers of small-effect, polygenic resistance alleles. Our results suggest a new polygenic model for inheritance of nonfamilial CRC, and that genetic studies in humans aimed at identifying individuals with elevated susceptibility should be pursued through the lens of absence of dominant resistance alleles rather than for the presence of susceptibility alleles.