Abstract
Background/Aim: Xeroderma pigmentosum complementation group C (XPC) is reported to play important roles in DNA integrity and genomic instability, however, the contribution of XPC to colorectal cancer (CRC) carcinogenesis is largely uncertain. Therefore, we aimed to examine the potential associations of XPC rs2228000 and rs2228001 genotypes and CRC susceptibility in a Taiwanese cohort.
Materials and Methods: A total of 362 patients with CRC and non-cancer controls were genotyped using the polymerase chain reaction-restriction fragment length polymorphism method. The distribution of genotypes and alleles was assessed, and conformity to Hardy–Weinberg equilibrium was checked.
Results: Firstly, no statistically significant differences were observed in the genotypic frequencies of XPC rs2228000 and rs2228001 between patients with CRC and healthy controls (p for trend=0.5419 and 0.5005, respectively). Secondly, the allelic analyses revealed lack of associations with CRC risk regarding XPC rs2228000 T allele (odds ratio=0.89, 95% confidence interval=0.72-1.11, p=0.3446), and rs2228001 C allele (odds ratio=1.14, 95% confidence interval=0.92-1.41, p=0.2688). Interestingly, individuals carrying the CT or TT genotypes of XPC rs2228000 were prone to presenting metastatic behavior (p=0.0001). Moreover, individuals carrying the AC or CC genotypes of XPC rs2228001 were more likely to have larger tumor sizes (≥5 cm, p=0.0116), lymph node involvement (p=0.0014), advanced clinical stage (III-IV, p=0.0002), and metastasis (p=0.0002).
Conclusion: Although the investigated XPC polymorphisms were not associated with CRC susceptibility, the rs2228000 and rs2228001 variant genotypes may serve as novel prognostic biomarkers. Further large-scale studies across diverse populations are recommended to validate these findings.
- Colorectal cancer
- genotype
- single nucleotide polymorphism
- xeroderma pigmentosum complementation group C
- Taiwanese
Introduction
Colorectal cancer (CRC) continues to represent a significant global public health challenge, ranking as the third most diagnosed malignancy and the second leading cause of cancer-associated deaths worldwide (1, 2). To effectively reduce its incidence and mortality, it is essential to elucidate both modifiable environmental exposures and inherited genetic factors that contribute to disease susceptibility. Among behavioral influences, a robust body of epidemiological evidence has repeatedly associated elevated CRC risk with a sedentary lifestyle (3, 4), habitual smoking (5, 6), and high alcohol consumption (7, 8). In addition, diets rich in red and processed meats (9, 10), frequent intake of sugar-sweetened beverages (11, 12) and excess body weight (13, 14) have been identified as critical risk-enhancing factors. The contribution of inherited susceptibility remains under intensive study, as translational medical researchers aim to uncover more predictive biomarkers that can inform individualized screening strategies and guide targeted interventions (15).
The xeroderma pigmentosum complementation group C (XPC) gene encodes a core component of the nucleotide excision repair (NER) pathway, particularly involved in the early detection of helix-distorting DNA lesions (16). Biochemical analyses have demonstrated that XPC forms a functional complex with RAD23 nucleotide excision repair protein B (RAD23B), which plays a pivotal role in recognizing bulky DNA adducts and triggering the NER cascade (17, 18). Within the broader NER process, damage recognition is considered the rate-limiting step, highlighting the significance of this initial interaction (18). This concept provides a mechanistic basis for exploring XPC as a potential biomarker in cancer susceptibility. According to data from the National Center for Biotechnology Information, the coding region of XPC harbors over 100 single nucleotide polymorphisms (SNPs). Among these, two variants, Ala499Val (rs2228000) and Lys939Gln (rs2228001) (Figure 1), have been most extensively studied in relation to cancer risk. The rs2228000 variant lies within the region responsible for RAD23B binding, whereas rs2228001 is situated in the domain that interacts with the transcription factor II H (TFIIH) (19). Numerous investigations have evaluated the correlation between these two polymorphisms and various types of malignancies [rs2228001 (20-24), and rs2228000 (25-28)]. However, findings across these studies have been heterogeneous, with no consistent consensus on their impact on cancer susceptibility.
Physical map for xeroderma pigmentosum complementation group C (XPC) rs2228000 and rs2228001 polymorphic sites.
Since 2006, several translational research studies have examined the potential involvement of XPC gene polymorphisms in CRC susceptibility. The majority of these investigations have focused on the common variants rs2228000 (29-34) and rs2228001 (29-42). Despite extensive efforts, the findings from these studies remain inconclusive, with conflicting results regarding the association between these SNPs and CRC risk.
We performed a hospital-based case–control study involving 362 patients with CRC and 362 age- and sex-matched healthy controls from a Taiwanese population. This investigation aimed to assess the potential contribution of XPC rs2228000 and rs2228001 variants to CRC susceptibility. Furthermore, we evaluated whether these polymorphisms may serve as prognostic indicators for CRC risk prediction.
Materials and Methods
Recruitment of hospital-based patients with CRC and matched controls. This hospital-based case–control study was designed to investigate the association between XPC gene polymorphisms and susceptibility to CRC. A detailed characterization of the study cohort has been described previously (43-45); a summary of baseline characteristics is presented in Table I. A total of 362 patients with CRC were recruited from the Department of General Surgery at China Medical University Hospital, a major tertiary medical center located in central Taiwan. Comprehensive clinicopathological data were systematically collected for each case. The control group consisted of 362 cancer-free individuals, frequency-matched to cases by age and sex at a 1:1 ratio. Information on demographic and lifestyle variables, including age, sex, smoking status, alcohol use, and body mass index (BMI), was obtained from structured medical records. Clinical data for CRC cases encompassed tumor anatomical location, size, histological grade, lymph node involvement, TNM stage (American Joint Committee on Cancer Staging Manual, 7th edition), and metastatic status (Table I).
Selected characteristics of the 362 patients with colorectal cancer and 362 non-cancer controls.
The study protocol was approved by the Institutional Review Board of China Medical University Hospital (approval number: DMR99-IRB-108) and was conducted in accordance with the ethical principles of the Declaration of Helsinki. All study participants were of Taiwanese ethnicity.
Genotyping procedure for XPC polymorphisms. Genomic DNA was extracted from peripheral blood leukocytes obtained from both patients with CRC and matched healthy controls using a commercially available DNA purification kit (Blossom, Taipei, Taiwan, ROC), following standardized protocols as described in previous studies (46, 47). Genotyping of XPC rs2228000 and rs2228001 polymorphisms was carried out using polymerase chain reaction-restriction fragment length polymorphism analysis using primer sequences (AllBio, Taichung, Taiwan, ROC) for XPC rs2228000 and rs2228001 as given in Table II. Polymerase chain reaction products were subsequently digested with the Fnu4H I restriction enzyme (New England BioLabs, Ipswich, MA, USA) for both loci, following the manufacturer’s instructions, producing the fragments as given in Table II.
Sequences of the designed primers, corresponding endonucleases and fragments identifications for genotyping of xeroderma pigmentosum complementation group C (XPC) rs2228000 and rs2228001.
Statistical analysis of XPC genotypes in the CRC cohort. The distribution of XPC genotypes among patients and controls was first assessed for conformity with Hardy–Weinberg equilibrium using the chi-square goodness-of-fit test. To compare differences in demographic variables, lifestyle factors, BMI, genotypic frequencies, and allelic distributions between the case and control groups, Pearson’s chi-square test was applied using 2×2 contingency tables, where appropriate. The association between XPC polymorphisms (rs2228000 and rs2228001) and CRC risk was estimated by calculating odds ratios (ORs) and corresponding 95% confidence intervals (CIs). All statistical tests were two-sided, and a value of p<0.05 was considered indicative of statistical significance.
Results
Distribution and association analysis of XPC rs2228000 and rs2228001 polymorphisms. The genotypic distributions of XPC rs2228000 and rs2228001 were evaluated in a total of 362 CRC cases and 362 matched cancer-free controls, as presented in Table III. Genotypic frequencies in the control group conformed to Hardy–Weinberg equilibrium, with p-values of 0.3309 for rs2228000 and 0.7307 for rs2228001, indicating no deviation from expected proportions. Association analyses under both co-dominant and dominant genetic models revealed no statistically significant relationship between polymorphism and CRC susceptibility (Table III). In line with these findings, the allelic frequency comparison (Table IV) showed no significant differences between cases and controls. Specifically, neither the rs2228000 T allele nor the rs2228001 C allele demonstrated a meaningful association with CRC risk when compared to their respective wild-type alleles.
Genotypic frequency distributions of xeroderma pigmentosum complementation group C (XPC) genotypes among the colorectal cancer cases and healthy controls.
Allelic frequencies for xeroderma pigmentosum complementation group C (XPC) polymorphisms among colorectal cancer cases and healthy controls.
Associations between XPC genotypes and clinicopathological features in patients with CRC. The potential impact of XPC rs2228000 and rs2228001 polymorphisms on key clinicopathological characteristics of patients with CRC was further investigated. Analysis of the XPC rs2228000 variant revealed that individuals with T-carrying genotypes showed no significant differences in distribution by age (≤60 versus >60 years; p=0.6695), sex (male versus female; p=0.8875), or BMI (<24 versus ≥24 kg/m2; p=0.9542) (Table V). However, a statistically significant association was observed between the T-carrying genotypes of rs2228000 and the presence of distant metastasis (p=0.0001; Table VI). Similarly, no significant associations were found between rs2228001 C-carrying genotypes and patient age (p=0.8725), sex (p=0.7457), or BMI (p=0.3249) (Table VII). In contrast, the C-carrying genotypes of rs2228001 were significantly associated with several aggressive disease features, including larger tumor size (≥5 cm; p=0.0116), lymph node involvement (p=0.0014), advanced clinical stage (p=0.0002), and metastasis (p=0.0002) (Table VIII). These findings suggest that while neither polymorphism appears to be influenced by demographic characteristics, both may contribute to the progression and severity of CRC, particularly rs2228001, which was strongly associated with multiple indicators of poor prognosis.
Distribution of basic characteristics according to xeroderma pigmentosum complementation group C (XPC) rs2228000 genotype among 362 patients with colorectal cancer.
Distribution of clinical characteristics according to xeroderma pigmentosum complementation group C (XPC) rs2228000 genotype among 362 patients with colorectal cancer.
Distribution of basic characteristics according to xeroderma pigmentosum complementation group C (XPC) rs2228001 genotype among 362 patients with colorectal cancer.
Distributions of clinical characteristics according to xeroderma pigmentosum complementation group C (XPC) rs2228001 genotype among 362 patients with colorectal cancer.
Discussion
Genomic instability is a hallmark of CRC and often arises from the failure to repair DNA damage effectively (48, 49). The NER pathway is a major DNA-repair mechanism that has been repeatedly implicated in CRC pathogenesis (50, 51). In the current study, we found that individuals carrying either heterozygous or homozygous variant genotypes of XPC rs2228000 or rs2228001 did not exhibit a statistically significant increase in overall CRC susceptibility (Table III). Allelic distribution analysis further reinforced this observation, indicating that these variants are unlikely to serve as effective biomarkers for prediction of CRC risk (Table IV). Notably, we report for the first time the finding of CT and TT genotypes of rs2228000 as being significantly associated with distant metastasis in CRC patients (Table VI), suggesting a potential role in disease progression. Furthermore, carriers of the AC and CC genotypes at rs2228001 demonstrated a broader range of associations, including larger tumor size, lymph node involvement, advanced clinical stage, and metastatic disease (Table VIII). These findings point to a possible prognostic utility of XPC variants in stratifying CRC severity. Both rs2228000 and rs2228001 are missense polymorphisms, resulting in amino acid substitutions that may alter the conformation or functional capacity of the XPC protein, potentially impacting its role in DNA damage recognition within the NER pathway (52).
It is critical to acknowledge that the distribution of XPC polymorphisms can vary considerably across ethnic groups, potentially contributing to discrepancies in genotype-phenotype associations observed in different study populations. To illustrate, we examined the allelic frequency of XPC rs2228000 using a global dataset (https://www.ncbi.nlm.nih.gov/snp/) comprising 649,452 individuals, including 530,208 of European descent, 47,674 Africans, 45,912 African Americans, 16,936 Asians, and 12,748 East Asians (Table IX). The minor allelic frequency (MAF) of the rs2228000 T allele ranged from 0.0939 in Africans to 0.3457 in East Asian populations. In our Taiwanese CRC cohort, the T allelic frequency was 0.3446, closely mirroring those in both Asian (0.3400) and East Asian (0.3457) groups but was substantially higher than that observed in African (0.0939) and African American (0.0953) populations (Table IX). Despite this population-level variation, prior studies across diverse ethnicities have consistently reported no significant association between rs2228000 genotypes and CRC susceptibility (29-34) (Table X). Our findings are in line with this literature, as the CT and TT genotypes of rs2228000 did not show a significant correlation with overall CRC risk in this Taiwanese cohort (Table III). Intriguingly, however, our study identified a novel association between rs2228000 CT and TT genotypes and metastatic CRC (Table VI), suggesting a potential role for rs2228000 as a prognostic biomarker rather than a susceptibility marker. Given the observed ethnic differences in allelic frequency and the possibility of gene–environment interactions, further validation in larger and more ethnically diverse populations is essential to confirm the generalizability and clinical applicability of these findings.
Variant allelic frequencies of xeroderma pigmentosum complementation group C (XPC) single nucleotide polymorphisms (SNP) among different populations according to data extracted from https://www.ncbi.nlm.nih.gov/snp/, updated 2025/07/25.
Literature-reported genotypes of xeroderma pigmentosum complementation group C (XPC) rs2228000 among colorectal cancer populations and association with colorectal cancer (CRC) risk.
Regarding the XPC rs2228001 variant, allelic frequency data from a global cohort of 520,780 individuals, comprising 400,210 Europeans, 49,198 Africans, 47,544 African Americans, 7,772 Asians, and 5,242 East Asians, revealed MAFs ranging from 0.2775 to 0.4110 (Table IX). Unlike rs2228000, where East Asians exhibit the highest MAF, the allelic frequency of rs2228001 is relatively consistent across populations, without a pronounced peak in East Asians. A review of the literature indicates that variant genotypes at rs2228001 have been linked to an increased risk of CRC in several case-control studies (31, 39, 40, 42). Conversely, our findings are consistent with many other investigations reporting a lack of association (Table XI) (29, 30, 32-38, 41). These discrepancies likely reflect the underlying ethnic heterogeneity in genotypic distributions and potential population-specific gene–environment interactions. While our study does not replicate the positive susceptibility associations reported by Liu et al. (39) and Wu et al. (31) in Chinese cohorts from East Asia, we identified that the C-carrying genotypes at rs2228001 are significantly associated with adverse clinicopathological features, such as larger tumor size, lymph node metastasis, advanced clinical stage, and distant metastasis, highlighting their potential utility as prognostic biomarkers in CRC (Table VIII and Table XI). Notably, similar null results regarding CRC susceptibility were observed in East Asian cohorts by Sun’s (34) and Wang’s (41) teams. Regarding gene–environment interactions, Hansen and colleagues reported that the CC genotype at rs2228001 significantly increased CRC risk among individuals with high red meat consumption compared to those with lower intake (35). In contrast, Berndt et al. found no significant interaction between XPC polymorphisms (rs2228000 and rs2228001) and smoking behavior (30), a finding our results are consistent with (data not shown).
Literature-reported genotypes of xeroderma pigmentosum complementation group C (XPC) rs2228001 among colorectal cancer populations and association with colorectal cancer (CRC) risk.
Several limitations of the present study should be acknowledged. Firstly, the absence of long-term follow-up data limits our ability to evaluate the prognostic significance of the XPC rs2228000 and rs2228001 polymorphisms in CRC risk determination, particularly with regard to their potential impact on patient survival, metastatic progression, and risk of recurrence. Secondly, the study lacks comprehensive expression profiling of XPC at both the mRNA and protein levels, thereby constraining our ability to establish definitive genotype–phenotype correlations. Thirdly, although our hypothesis proposes that impaired DNA-repair capacity may contribute to genomic instability and thereby increase CRC susceptibility, we did not perform functional assays to assess DNA_repair efficiency in patients with CRC nor healthy controls.
Our findings suggest that variant genotypes at XPC rs2228000 and rs2228001 do not function as robust clinical biomarkers for predicting susceptibility to CRC. Nonetheless, the presence of variant (CT+TT) genotypes at rs2228000 appears to be a promising indicator of metastatic progression. Similarly, variant (AC+CC) genotypes at rs2228001 are associated with more aggressive disease features, including larger tumor size, lymph node involvement, advanced clinical stage, and metastasis, highlighting their potential prognostic value. Future studies should prioritize elucidating the functional impact of these polymorphisms on XPC protein activity and their influence on NER efficiency. Additionally, a comprehensive examination of gene–phenotype interactions is warranted to clarify the complex interplay between genetic variants and clinical outcomes. Reinvestigating how XPC genetic alterations affect DNA-repair capacity may provide critical insights for personalized medicine, enabling the development of targeted therapeutic strategies. In summary, the role of XPC in colorectal carcinogenesis remains an essential subject for continued research, with significant implications for improving understanding of CRC progression and refining treatment approaches.
Acknowledgements
The Authors would like to acknowledge the doctors, nurses and all the participants for their invaluable data collection. In addition, the technical support from Ai-Chia Tung and Hong-Xue Ji are highly appreciated. Furthermore, the Authors would like to extend their gratitude to all the study participants, as well as the doctors, nurses, and colleagues who contributed to the study. This study was supported by grants from Shin-Kong Wu Ho-Su Memorial Hospital (2021SKHADR031), Taichung Armed Forces General Hospital (TCAFGH-D-113014), and Taichung Veterans General Hospital (TCVGH-1142101B).
Footnotes
Authors’ Contributions
Conceptualization: Tsai YF, Chang WS, and Bau DT; collection: Ke TW, Wu MH, and Yueh TC; Data curation: Ke TW, Wu MH, Lin TC and Yueh TC; genotyping: Shih HY, Wang YC and Chang WS; statistical analysis: Yang JS, Hung YC and Tsai CW; project administration: Tsai YF, Lin TC, Wu MH and Bau DT; supervision: Bau DT, Tsai CW and Chang WS; validation: Chang WS and Bau DT; writing–original draft: Tsai YF, Bau DT and Chang WS; writing–review and editing: Bau DT and Chang WS. All Authors have read and agreed to the published version of the manuscript.
Conflicts of Interest
The Authors declare no conflicts of interest regarding this study.
Artificial Intelligence (AI) Disclosure
No artificial intelligence tools, including large language models or machine learning software, were used in the preparation, analysis, or presentation of this manuscript.
- Received July 25, 2025.
- Revision received August 7, 2025.
- Accepted August 8, 2025.
- Copyright © 2025 The Author(s). Published by the International Institute of Anticancer Research.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
References
In this issue
Jump to section
Related Articles
Cited By...
- No citing articles found.