Lack of association between MDR1 C3435T polymorphism and chemotherapy response in advanced breast cancer patients: evidence from current studies

No Association between ABCB1 G2677T/A or C3435T Polymorphisms and Survival of Breast Cancer Patients—A 10-Year Follow-Up Study in the Polish Population

Many intensive studies are devoted to identifying novel cancer diagnostics or therapy strategies that would boost cancer therapy efficacy and recovery rates. Importantly, polymorphisms in the genes coding for ABC family proteins were considered good candidates for cancer development risk or cancer drug resistance markers. For this reason, we decided to assess the contribution of ABCB1’s most common variants (i.e., G2677T/A in exon 21/rs2032582 and C3435T in exon 26/rs1045642) to the cancer therapy response in breast cancer patients. A 10-year follow-up analysis of 157 breast cancer patients was performed. Clinical assessment, ABCB1 polymorphism status, estrogen/progesterone/human epidermal receptors status, and other characteristics were compared according to the follow-up status using the Chi-square statistic. For the analysis of overall survival curves in TCGA breast cancer patients, the Xena browser was used. We show that neither 2677 nor 3435 polymorphisms contributed to the survival of breast cancer patients. Interestingly, but not surprisingly, estrogen and progesterone receptors status were good prognostic factors and positively correlated with a disease-free survival for up to 10 years. To summarize, ABCB1 polymorphisms status may be one of the numerous factors that affect cancer development. However, they may not be the critical ones when it comes to risk or recovery assessment. Consequently, they may not be treated as reliable prognostic or predictive markers in breast cancer patients’ evaluation, which supports the previous findings and current knowledge.

Prevalence of ABCB1 3435C>T polymorphism in the Cuban population

OBJECTIVES

ABCB1 gene polymorphisms can modify P-glycoprotein function with clinical consequences.

METHODS

The 3435C>T polymorphism prevalence was analyzed using oligonucleotide probes and next-generation sequencing in 421 unrelated healthy individuals living in Cuba. Data were stratified by gender, ethnic background and residence. The genotype and allelic frequencies were determined.

RESULTS

The genotype distribution met the Hardy-Weinberg equilibrium assumption. The allelic frequency was 63.5% for the 3435C variant. The genotype frequencies were 41.1% for CC, 44.9% for CT and 14.0% for TT. The allele and genotype distributions differed between individuals living in La Habana and Santiago de Cuba (p<0.05) when ethnic background was analyzed. The allelic distribution was similar among Admixed and Black subjects, and they differed from Caucasians. The CC genotype was equally distributed among Admixed and Black subjects, and they differed from Caucasians. The TT genotype frequency differed between Caucasians and Admixed. The CT genotype was distributed differently among the three groups. Similar distribution was obtained in Brazilians, whereas some similarities were observed in African, Spanish and Chinese populations, consistent with the mixed Cuban ethnic origin.

CONCLUSIONS

This is the first report on allele and genotype frequencies of the 3435C>T polymorphism in Cuba, which may support personalized medicine programs.

Influence of ABCB1 C3435T and C1236T gene polymorphisms on tumour response to docetaxel-based neo-adjuvant chemotherapy in locally advanced breast cancer patients of South India

WHAT IS KNOWN AND OBJECTIVE

Variable response to docetaxel-based neo-adjuvant chemotherapy (NACT) in breast cancer patients had been reported. Genetic polymorphisms in the ABCB1 gene coding for the efflux transporter MDR1 (P-glycoprotein, P-gp) could result in altered tumour response. Hence, this study was proposed to assess the effect of single nucleotide polymorphisms (SNPs) of ABCB1 gene on tumour response in locally advanced breast cancer patients (LABC) of South India who have a distinct genetic makeup.

METHODS

Out of 162 LABC patients recruited, 129 patients were included for the final analysis. DNA was extracted by "phenol-chloroform extraction method" from the WBCs, and genotyping for SNPs rs1045642 (C3435T) and rs1128503 (C1236T) in ABCB1 gene was performed with real-time PCR system using validated TaqMan^® SNP genotyping assay method. Tumour response was assessed by RECIST criteria based on the MRIs taken before and after completion of four cycles of docetaxel therapy.

RESULTS AND DISCUSSION

A total of 102 (79.1%) patients were found to be responders and 27 (20.9%) patients were found to be non-responders to docetaxel therapy. Patients with "CT/TT" genotypes (response rate: 83.3%) of ABCB1 (C1236T) gene showed better tumour response than those with "CC" genotype (response rate: 16.6%) [OR = 2.94 (CI: 1.15-7.52); P = 0.03]. However, on performing binary logistic regression, neither the studied SNPs nor the non-genetic factors like age, BMI, postmenopausal status, laterality of the tumour, ER status, PR status and Her-2/neu status were found to be associated with tumour response to docetaxel (P > 0.05).

WHAT IS NEW AND CONCLUSION

The tumour response to docetaxel was significantly influenced by the SNP C1236T of ABCB1 gene coding for the P-gp. However, when adjusted for other non-genetic factors, neither of the ABCB1 variants were found to be associated with tumour response to docetaxel-based NACT in LABC patients of South India.

Associations between genetic polymorphisms of membrane transporter genes and prognosis after chemotherapy: meta-analysis and finding from Seoul Breast Cancer Study (SEBCS)

Membrane transporters can be major determinants of the pharmacokinetic profiles of anticancer drugs. The associations between genetic variations of ATP-binding cassette (ABC) and solute carrier (SLC) genes and cancer survival were investigated through a meta-analysis and an association study in the Seoul Breast Cancer Study (SEBCS). Including the SEBCS, the meta-analysis was conducted among 38 studies of genetic variations of transporters on various cancer survivors. The population of SEBCS consisted of 1338 breast cancer patients who had been treated with adjuvant chemotherapy. A total of 7750 SNPs were selected from 453 ABC and/or SLC genes typed by an Affymetrix 6.0 chip. ABCB1 rs1045642 was associated with poor progression-free survival in a meta-analysis (HR = 1.33, 95% CI: 1.07-1.64). ABCB1, SLC8A1, and SLC12A8 were associated with breast cancer survival in SEBCS (P_gene < 0.05). ABCB1 rs1202172 was differentially associated with survival depending on the chemotherapy (P_interaction = 0.035). Our finding provides suggestive associations of membrane transporters on cancer survival.

ABCB1 gene polymorphisms and response to chemotherapy in breast cancer patients: A meta-analysis

The ABCB1 gene encodes the P-glycoprotein, an efflux pump for some antineoplastic agents which acts as a resistance mechanism to chemotherapy. Three SNPs (C3435T, C1236T and G2677T/A), are the most widely studied in ABCB1. The inconsistent conclusions about the association of these polymorphisms and the response to chemotherapy in breast cancer (BC) patients prompted us to conduct a meta-analysis. A total of nine (770 patients), five (566 patients) and three studies (367 patients) relating the ABCB1 C3435T, C1236T and G2677T/A polymorphisms respectively, were included. The main analysis revealed a lack of association between ABCB1 polymorphisms and response to chemotherapy in every genetic model: C3435T (dominant OR: 0.888; 95%CI: 0.558-1.413), C1236T (dominant OR: 1.968; 95%CI: 0.609-6.362) and G2677T/A (GG vs GT + GA + TT + TA + AA OR: 0.854; 95%CI: 0.418-1.744). Stratification by ethnicity, cancer type and response criteria did not change the pattern of results. The available evidence indicates that three polymorphisms within ABCB1; C3435T, C1236T and G2677T/A, cannot be considered a reliable predictor of response to chemotherapy in BC patients.

MDR1 C3435T polymorphism associated with the development of clinical features in Behçet's disease in Iranian Azeri Turkish patients

BACKGROUND

Behçet's disease (BD) is a systemic vasculitis of unknown cause with a higher prevalence along the ancient Silk Road. Behçet's occasional familial aggregation and its close association with genes of major histocompatibility complexes justify that genetic factors play an important role in the development of the disease. In this study, we evaluated the association of multidrug resistance (MDR1) C3435T polymorphism with the severity of BD.

METHOD

We investigated the distribution of MDR1 C3435T polymorphism in 69 patients from the Iranian Azeri Turks group with BD and 92 ethnically sex-matched healthy controls, via the polymerase chain reaction-restriction fragment length polymorphism technique.

RESULT

Although there was no significant association of MDR1 C3435T polymorphism between two groups of patients and healthy controls, our data showed a substantial association of CC genotype with the development of several clinical features, including erythema nodosum (P = 0.001, OR = 2.686, 95%), pseudofolliculitis (P = 0.002, OR = 2.812, 95%), and skin lesions (P = 0.040, OR = 1.934, 95%).

CONCLUSION

These results suggest that CC genotype is a risk factor for the development of some clinical features of BD in patients from the Iranian Azeri Turk ethnic group.

Investigation on XRCC1 genetic polymorphism and its relationship with breast cancer risk factors in Chinese women

Breast cancer (BC) remains one of the most common cancers among women. The human X-ray repair cross-complementing 1 (XRCC1) gene plays key roles in base excision repair, and genetic polymorphisms of XRCC1 may be associated with the susceptibility to BC. This study aimed to evaluate the relationship between the XRCC1 genetic polymorphisms and BC susceptibility. A total of 354 BC patients and 366 cancer-free controls were enrolled in this study. Data about the risk factors of BC were collected using questionnaires. The XRCC1 genetic polymorphism was determined using created restriction site-polymerase chain reaction (CRS-PCR) and DNA sequencing methods. No significant differences in the allelic and genotypic frequencies of c.1804C>A genetic polymorphism were detected between cases and controls. The distributions of BC patients' risk factors were not significantly different between CC, CA, and AA genotypes. These findings indicate that the c.1804C>A genetic polymorphism of XRCC1 gene is not significantly associated with BC susceptibility in the Chinese women.

Association analysis between MDR1 genetic variant and breast cancer risk factors in Chinese Han population

The multidrug resistance 1 gene (MDR1) is an important candidate gene for influencing breast cancer susceptibility. This study aimed to evaluate the association between MDR1 genetic variants and breast cancer susceptibility. A total of 340 breast cancer patients and 348 cancer-free controls were enrolled in this study. The patients' general characteristics and related risk factors of breast cancer were collected by questionnaires. The c.4125A>C genetic variant was genotyped through created restriction site polymerase chain reaction method. Our data suggest that there are no significant differences in the allelic and genotypic frequencies between breast cancer patients and cancer-free controls. Moreover, the distribution of breast cancer patients' risk factors is not different among AA, AC, and CC genotypes. These preliminary results suggest that the c.4125A>C genetic variant is not significantly associated with breast cancer susceptibility.

Association between single genetic polymorphisms of MDR1 gene and gastric cancer susceptibility in Chinese

Gastric cancer is a common cancer worldwide. The multidrug resistance 1 gene (MDR1) is one of the most important candidate genes for influencing gastric cancer susceptibility. This study aimed to analyze the association between genetic variants of MDR1 gene and the susceptibility to gastric cancer in Chinese Han population. A total of 365 gastric cancer patients and 367 cancer-free controls were enrolled in this study. The single genetic polymorphisms (SNPs) of MDR1 gene were genotyped by the created restriction site-polymerase chain reaction method. Our data suggested that the allele and genotype frequencies of c.159G > T and c.1564A > T were statistically different between gastric cancer patients and cancer-free controls. Association analyses indicated that these two SNPs were statistically associated with the increased risk of gastric cancer (for c.159G > T, TT versus (vs.) GG: OR 2.34, 95 % CI 1.31-4.19; TT vs.

GT/GG

OR 2.32, 95 % CI 1.32-4.08; T vs. G: OR 1.27, 95 % CI 1.01-1.59; for c.1564A > T, TT vs. AA: OR 2.27, 95 % CI 1.31-3.93; TT vs.

AT/AA

OR 2.21, 95 % CI 1.30-3.75; T vs. A: OR 1.30, 95 % CI 1.04-1.62). The allele-T of both these two SNPs may contribute to the susceptibility to gastric cancer in Chinese Han population. The c.159G > T and c.1564A > T genetic variants might be used as molecular markers for detecting gastric cancer susceptibility.