Abstract
Breast cancer risk have been discussed to be associated with polymorphisms in genes as well as abnormal DNA damage repair function. This study aims to assess the relationship between genes single nucleotide polymorphisms (SNPs) related to DNA damage repair and female breast cancer risk in Chinese population. A case–control study containing 400 patients and 400 healthy controls was conducted. Genotype was identified using the sequence MassARRAY method and expression of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER-2) in tumor tissues was analyzed by immunohistochemistry assay. The results revealed that ATR rs13091637 decreased breast cancer risk influenced by ER, PR (CT/TT vs. CC: adjusted odds ratio [OR] = 1.54, 95% confidence interval [CI]: 1.04–2.27, p = 0.032; CT/TT vs. CC: adjusted OR = 1.63, 95%CI: 1.14–2.35, p = 0.008) expression. Stratified analysis revealed that PALB2 rs16940342 increased breast cancer risk in response to menstrual status (AG/GG vs. AA: adjusted OR = 1.72, 95%CI: 1.13–2.62, p = 0.011) and age of menarche (AG/GG vs. AA: adjusted OR = 1.54, 95%CI: 1.03–2.31, p = 0.037), whereas ATM rs611646 and Ku70 rs132793 were associated with reduced breast cancer risk influenced by menarche (GA/AA vs. GG: adjusted OR = 0.50, 95%CI: 0.30–0.95, p = 0.033). In a summary, PALB2 rs16940342, ATR rs13091637, ATM rs611646, and Ku70 rs132793 were associated with breast cancer risk.
Introduction
Breast cancer, a highly heterogeneous disease (Duijf et al., 2019), has an increasing impact on health of women worldwide (Trapani et al., 2022). Cancer heterogeneity can be driven by genomic instability (Kudelova et al., 2022). Mutations of genes involved in DNA damage repair pathway could disrupt the normal function, leading to genomic instability that ultimately facilitates the development and progression of cancer (Tubbs and Nussenzweig, 2017). The etiology of breast cancer is multifaceted, involving physiological, environmental, and genetic factors, with polymorphisms of genes across various biological pathways posing potential susceptibility for breast cancer (Bahreini et al., 2021).
Single nucleotide polymorphisms (SNPs) are DNA sequence polymorphisms generated by variations in a single nucleotide, which is the common type of human genetic variation, occurring in every 300 bases (Abd El-Fattah et al., 2018; Fadason et al., 2022). SNPs are common in the human genome, which can cause genetic differences between individuals, serving as significant genetic markers in the investigation of cancer and its characteristics. Growing evidence links breast cancer susceptibility to SNPs (Gao et al., 2019).
DNA damage repair pathways, which play an important role in maintaining genome stability and cellular homeostasis, include mismatch repair (MMR), base excision repair (BER), nucleotide excision repair (NER), nonhomologous end-joining (NHEJ) and homologous recombination (HR) repair (Kottemann and Smogorzewska, 2013; Scully et al., 2019). The occurrence and development of cancer are closely associated with the abnormal DNA damage repair function (Huang and Zhou, 2021).
RAD21, PALB2, ATR, ATM, Ku70, and Ku80 are all involved to DNA damage repair pathways and SNPs of these genes are likely to be linked to cancer risk. For example, RAD21 rs2289937 and rs4579555 have been proved to be associated with cervical cancer (Xia et al., 2018), RAD21 rs16888927, rs16888997, and rs16889040 may affect the risk of breast cancer and ovarian cancer (Sehl et al., 2009).
Studies have proved that variants of PALB2 conferred breast cancer susceptibility in the Chinese population, and PALB2 rs249954 and rs120963 were associated with increased cancer risk (Chen et al., 2008). In addition, several previous studies have explored the association of ATR, Ku70 and Ku80 SNPs with cancer risk (Henríquez-Hernández et al., 2016; Li et al., 2011; Lin et al., 2013; Singh et al., 2018; Vuorinen et al., 2023; Zhang et al., 2017).
However, breast cancer incidence continues to increase among Chinese women and there is still a lack of early screening, detection, and effective targeted treatment for breast cancer (Wang et al., 2021). Studies have demonstrated the association of SNPs with cancer risk, as well as the interconnection between abnormalities in DNA damage repair and cancer. On this basis, we expect to conduct a more in-depth analysis of the relationship between SNPs in genes of DNA damage repair pathway and breast cancer risk, with the goal of identifying potential markers for the disease.
Materials and Methods
Study subjects
Four hundred patients previously diagnosed with breast cancer (mean age 53.17 ± 10.79 years) and 400 healthy controls (mean age 52.46 ± 10.88 years) who took physical examination were recruited for the study in Nanjing First Hospital from January 2008 to January 2017. Both the case and control groups were from the same region. A questionnaire was used to collect information of patients, including smoking, drinking, and family history.
The inclusion criteria were as follows: (1) breast cancer with female patients; (2) no history of smoking and drinking; (3) no other types of cancer; and (4) no personal or family history. In addition, we collected other information about the patients, including age at menarche, reproductive history, menopause, and tumor type. Furthermore, the SNPs of genes we included in the study were associated with the DNA damage repair pathway, including MMR, BER, NER, NHEJ, and HR.
Whole blood samples were collected from patients receiving surgical or pharmacologic treatment. The study protocol was approved by the Institutional Review Board of the Nanjing First Hospital and written informed consent was obtained from all participants (KY20220124-04). The methods were performed in accordance with approved guidelines.
SNP genotyping
DNA was extracted from whole blood samples from patients by the GoldMag-Mini Whole Blood Genomic DNA Purification Kit (GoldMag, Xi'an, China) according to the protocol and the concentration, and purification of the DNA were measured using the spectrometry (DU 530 UV/Vis spectrophotometer, Beckman Instruments, Fullerton, CA, USA). SNP genotyping was performed using Sequence MassARRAY RS-1000 (Sequenom, San Diego, CA, USA). Furthermore, we used Sequenom Typer 4.0 software for data management and analysis (Gabriel et al., 2009; Thomas et al., 2007).
Immunohistochemistry assay
The immunohistochemistry assay was used to detect the expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER-2) in paraffin-embedded tumor tissues. The rabbit monoclonal antibodies to ER, PR, and HER-2 used in this study were purchased from Spring Bioscience (Pleasanton, CA, USA).
Statistical analysis
Patient characteristics were assessed using the t-test and fitted chi-squared (χ2) test, and the Hardy–Weinberg equilibrium (HWE) in the healthy control group was assessed using the two-sided χ2 test. The association between SNPs and the risk of developing breast cancer was evaluated by calculating the odds ratio (OR) and 95% confidence interval (CI) using logistic regression. We used SPSS 23.0 software (IBM Corp, Armonk, NY, USA) to analyze the data. A p < 0.05 indicating a statistically significant difference.
Results
A total of 400 patients and the same number of healthy controls were included in our study. The information of the study population was summarized in Table 1, and there was no statistically significant difference in age. We collected data on genes involved in DNA damage repair pathways, including MMR, BER, NER, NHEJ, and HR. After a screening process, we identified significant genes within the NHEJ and HR pathways for further analysis. The genotypic distribution of SNP in patients and controls is shown in Table 2, and the genotypic distribution of all SNPs was not biased in HWE.
Characteristics of Patients with Breast Cancer and Healthy Controls
Independent t-test.
Two-sided chi-squared (χ2) test for the selected variables between cases and controls.
ER, estrogen receptor; HER-2, human epidermal growth factor receptor-2; PR, progesterone receptor; SD, standard deviation.
Information on the Included Genetic Variations
HWE, Hardy–Weinberg equilibrium.
Logistic regression revealed that the RAD21 rs16888927 CC genotype was associated with an increased breast cancer risk in all participants (CC vs. TT: adjusted OR = 3.93, 95%CI: 1.08–14.27, p = 0.038). Moreover, it was observed that other SNPs did not exhibit a correlation with the breast cancer risk, as shown in Table 3.
Genotype Distribution of Polymorphisms
Adjusted by age and menopausal status. The results with significant differences are Bold.
CI, confidence interval; OR, odds ratio.
Furthermore, we considered the impact of menopausal status on the risk of breast cancer in the study. Subsequent stratified analysis revealed that there was no significant association between SNPs and breast cancer risk in the premenopausal cohort. In the postmenopausal population, PALB2 rs16940342 AG genotype (AG vs. AA: adjusted OR = 1.59, 95%CI: 1.03–2.48, p = 0.038) and AG/GG genotype (AG/GG vs. AA: adjusted OR = 1.72, 95%CI: 1.13–2.62, p = 0.011) increased the risk of breast cancer, as demonstrated in Table 4.
Stratified Effects of Polymorphisms on Breast Cancer Risk by Menopausal Status
Adjusted by age. The results with significant differences are Bold.
Moreover, a subgroup analysis was performed based on patients' age of menarche and number of births (Table 5). The results showed that the PALB2 rs16940342 AG/GG genotype increased the risk of breast cancer in participants who had the menarche before 14 years old (AG/GG vs. AA: adjusted OR = 1.54, 95%CI: 1.03–2.31, p = 0.037). Meanwhile, among participants with menarche after 14 years old, ATM rs611646 AT/TT genotype was associated with decreased breast cancer risk (AT/TT vs. AA: adjusted OR = 0.61, 95%CI: 0.40–0.94, p = 0.026).
Stratified Effects of Single Nucleotide Polymorphisms on Breast Cancer Risk by Menarche and Births
Adjusted by age. The results with significant differences are Bold.
Furthermore, Ku70 rs132793 showed a consistent result that GA/AA genotype (GA/AA vs. GG: adjusted OR = 0.54, 95%CI: 0.30–0.95, p = 0.033) reduced breast cancer risk. Regarding the effect of number of births, our analysis revealed that SNPs were not significantly associated with breast cancer risk in populations with number of births ≤1 or number of births >1.
A subgroup analysis was conducted to assess the influence of ER, PR, and HER-2 expression on the risk of breast cancer (Table 6). We found that the ATR rs13091637 CT/TT genotype increased the risk of ER-negative breast cancer (CT/TT vs. CC: adjusted OR = 1.54, 95%CI: 1.04–2.27, p = 0.032). Besides, the allele T of ATR rs13091637 increased the risk of PR-negative breast cancer (CT/TT vs. CC: adjusted OR = 1.63, 95%CI: 1.14–2.35, p = 0.008). As for participants with HER-2-negative or positive breast cancer, our results did not significantly show an association between SNPs and the risk of developing breast cancer.
Stratified Effects of Single Nucleotide Polymorphisms on Breast Cancer Risk by the Expression of Estrogen Receptor, Progesterone Receptor, and Human Epidermal Growth Factor Receptor-2
Adjusted by age. The results with significant differences are Bold.
Discussion
Through a case–control study of 400 breast cancer patients and 400 healthy controls, we assessed the association between SNPs in genes related to DNA damage repair pathways and breast cancer risk. Breast cancer has a major impact on health of women, and its incidence has been increasing globally (Nolan et al., 2023; Trapani et al., 2022). Early detection of cancer and precise intervention strategies contribute to the reduction of cancer mortality (Siegel et al., 2022).
Identifying SNPs associated with cancer susceptibility can help enhance comprehension of the correlation between genetic variants and cancer risk, thereby facilitating the exploration of potential cancer biomarkers (Stracquadanio et al., 2016). Previous studies have showed that the occurrence and development of cancer were closely related to effected SNPs; however, the heterogeneity of SNPs among different races was always reported with inconsistent result and published data of SNPs related to DNA damage repair pathway were not all in agreement to date.
On this basis, we aimed to explore the relationship between Chinese female breast cancer risk and SNPs of genes in DNA damage repair pathway, which were from NHEJ and HR pathways, and we identified SNPs associated with an increased risk of breast cancer as well as some protective factors against the development of this disease in this study.
We assessed the association of SNPs in HR pathway genes with breast cancer susceptibility. ATR is a key kinase of DNA damage which response as a sensor of replication stress (Bradbury et al., 2020), our results revealed that ATR rs13091637 increased the risk of ER-negative, PR-negative, or HER-2-negative breast cancer. Previous studies have also reported the effect of ATR SNPs with breast cancer risk (Lin et al., 2013; Mehmood et al., 2020). ATR signaling facilitates the tolerance to DNA replication stress, and SNPs in ATR may consequently lead to dysfunction of genes and increased DNA damage. Simultaneously, normal cells may also be vulnerable to persistent replication stress (Yano and Shiotani, 2023).
In addition, we investigated ATM, a tumor suppressor involved in the repair of broken double strands of DNA (Stucci et al., 2021). ATM SNPs have been associated to an intermediate risk of breast cancer (Thompson et al., 2005). Li et al. have found that ATM rs611646 increased the risk of lung adenocarcinoma (Han et al., 2017), ATM rs611646 was also discovered to be a susceptibility locus for renal cell cancer by Shu et al. (Shu et al., 2018). However, we found ATM rs611646 was related to decreased risk of breast cancer in participants with menarche after 14 years old.
The inconsistency across the studies may be attributed to the impact of a later age at menarche (>14 years old) could shorten the total reproductive years of a woman, helping to reduce breast cancer risk (Daraei et al., 2019; Yang et al., 2022). And a longer interval between menarche and first pregnancy were associated with an increasing risk of breast cancer (Li et al., 2008; Liu et al., 2016). In addition, longer exposure to estrogen was also a detrimental factor in breast cancer (Collaborative Group on Hormonal Factors in Breast Cancer, 2012; Mishra et al., 2017; Yager and Davidson, 2006).
Furthermore, germline mutations in breast cancer susceptibility genes and SNPs, which contributed to breast cancer risk, were also affected by racial differences (Yap et al., 2019). Genetic diversity can lead to differences in the immune microenvironment and regulatory capacity of individuals. In addition, environmental differences across geographic regions and the lifestyles of various populations also contributed to variations in cancer risk (Martini et al., 2022; Yap, 2023).
We also analyzed PALB2, the partner and localizer of BRCA2 (Nepomuceno et al., 2021), which plays an important role in initiating HR and maintaining genome stability (Foo and Xia, 2022). Previous studies implied a significant relationship between PALB2 SNPs and breast cancer susceptibility, a finding that is consistent with the results of our study (Cecener et al., 2016; Wong et al., 2011; Wu et al., 2018). Our results indicated that PALB2 rs16940342 increased breast cancer risk in specific populations, including postmenopausal individuals, those with menarche occurring after the age of 14, and women who have given birth more than twice.
These populations were exposed to estrogen for long periods of time. Breast cancer risk factors include genetic and environmental factors (Cintolo-Gonzalez et al., 2017; Gail, 2015). Therefore, germline mutations in PALB2, a breast cancer susceptibility gene, may affect the HR pathway leading to genomic instability and tumorigenesis (Wu et al., 2020). In addition, early menarche, late menopause, and increased estrogen exposure were recognized as environmental risk factors for breast cancer (Yoshimura et al., 2022).
RAD21 is a crucial component of cohesin complex involved in the repair of DNA double-stranded breaks (Deng et al., 2022). Dysfunction of cohesin caused by RAD21 mutation can drive genomic instability, which eventually leads to cancer occurrence (Di Nardo et al., 2022). Our results revealed that RAD21 rs16888927 was linked to an increased risk of breast cancer; however, the reliability and consistency of these results were compromised by the limited sample size. It is necessary to expand the sample for further analyses.
Notably, Sehl et al. (2009) found that RAD21 rs16888927 was a risk factor for breast cancer. It has been discovered that RAD21 mutations or absence could impact the inhibitory effect of cohesin on PD-L1 and consequently increased immune evasion of tumor cells (Oreskovic et al., 2022). Sharaf et al. (2022) proposed a correlation between alterations in RAD21 and increased telomere length, which could promote the proliferation of cancer cells. These studies have revealed that RAD21 rs16888927 has the potential to be a marker for breast cancer.
The NHEJ pathway plays a crucial role in DNA damage repair in which Ku70 and Ku80 form dimers that bind to DNA ends, thereby assisting in the repair process (Inagawa et al., 2020). Our results implied that Ku70 rs132793 was associated with a reduced risk of breast cancer in participants who had menarche after 14 years old, whereas Ku80 SNPs had not been implicated in breast cancer risk. However, previous studies have found that Ku70 promoter region polymorphisms may be a breast cancer susceptibility factor, and the association between SNPs and breast cancer risk was stronger in female patients chronically exposed to estrogen (He et al., 2012; Willems et al., 2009).
The relationship between Ku80 SNPs and cancer risk has also been involved in numerous studies (Gomes et al., 2010; Hsu et al., 2009; Li et al., 2011). The discrepancies observed in these studies could be explained by variations in genetic profiles resulting from the impact of SNPs on gene coding. On a broader level, ethnic diversity and geographic influences may play a role in modulating the relationship between SNPs and the risk of breast cancer. In addition, individual characteristics of patients were possible to influence risk assessment such as estrogen expression and immune status.
Genome-wide association studies (GWAS) enable the study of common genetic variants associated with disease susceptibility and survival prognosis (Wang et al., 2019). The application of GWAS is important in cancer treatment, which has contributed to the identification of SNPs associated with increased cancer risk across diverse populations. However, the increase in cancer risk resulting from SNPs was limited (Fanfani et al., 2021b; Sud et al., 2017), which indicated that these risks were likely to be filtered by multiple hypothesis correction procedures in GWAS analyses (Pasaniuc and Price, 2017), especially when the minor allele frequency of locus is low, ultimately resulting in a portion of the cancer risk that cannot be reasonably explained (Fanfani et al., 2021a).
In contrast, our investigation into the correlation between gene SNPs involved in the DNA damage repair pathway and the susceptibility to breast cancer considered the impact of geographical factors and ethnicity, and our study cohort consisted of Chinese women from a homogeneous region. In addition, the individual characteristics of the participants were also considered and subgroup analyses were conducted with respect to their number of births and menopausal status.
This study also has some limitations: (1) breast cancer risk is closely related to estrogen stimulation, so more indicators related to this should be considered; (2) the study cohort had a relatively small sample size, highlighting the importance of expanding the research population for more robust findings; (3) all samples were from the Nanjing First Hospital, which is geographically homogeneous; and (4) the expression spectrum of HER-2 is beyond binary categorizations of positive and negative, and increasing numbers of studies are considering HER-2 expression status rather than simply classifying it as negative or positive (Anderson et al., 2023; Eiger et al., 2021).
Conclusion
PALB2 rs16940342, ATR rs13091637, ATM rs611646, and Ku70 rs132793 were associated with breast cancer risk.
Footnotes
Acknowledgments
We wish to express gratitude to all authors who participated in the research and completed the manuscript.
Authors' Contributions
Y.W. designed the main study, collected the primary data, and drafted the article. Y.S. validated and analyzed the data and further wrote the article. M.T. and X.L. checked all the analyses and refined the article. P.T., X.H., Q.J., and D.Y. provided much help in samples collection and analysis. T.X. and B.H. decided the main direction of the study and made the final revision of the article. All authors read and approved the final version of the article.
Author Disclosure Statement
No competing financial interests exist.
Funding Information
This study was supported by the National Nature Science Foundation of China (Grant No. 81902143), Nanjing Medical and Health Scientific Research Project (Grant No. YKK21137), and the Jiangsu Provincial Medical Key Discipline Cultivation Unit (Grant No. JSDW202239).
Supplementary Material
Supplementary Table S1
References
Supplementary Material
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