Pilot Study to Determine Prevalence of CYP2B6*6,CYP2C19*2 and CYP2C19*3 in Breast Cancer Patients Versus Normal Healthy Controls Among Three Major Ethnic Groups in Singapore

Background: Breast cancer is the top cancer suffered by women worldwide and has been identified to be the greatest killer for women living in Singapore. Unfortunately, most of breast cancer cases were detected only at later stage of disease development. This has crippled the effort of breast cancer therapy. As early detection of breast cancer could greatly improve the outcome of breast cancer therapy, it is of utmost importance to identify relevant biomarkers at the primitive stage of breast cancer development before the transformation of normal breast cells into cancerous cells. These biomarkers provide important clues leading to an efficient and targeted treatment approach in breast cancer preventive care.Methods: 455 breast cancer patients were consented to join this study. Buccal swabs were collected for genotyping on CYP2B6*6, CYP2C19 *2 & CYP2C19*3. The genotyping data were then compared to data collected from healthy individuals. Clinical data were collected from patient notes and analysed. All the statistical analyses were done using SPSS statistical software, version 19.0. Chi-square or Fisher’s Exact test were performed to examine the difference between subject’s characteristics for categorical variables and One-Way Anova was performed to assess age difference across alleles of CYP2B6*6, CYP2C19*2 and CYP2C19*3. Binary logistics regression was performed to identify demographic factors associated with breast cancer.Results: We reported thatCYP2B6*6 could be a risk factor leading to earlier onset of breast cancer among Indian population with OR found to be 1.69 (95% C.I.= 0.549-5.191, p=0.359). In the case of CYP2C19*2, OR is 1.57 for Malay (95% C.I. = 0.696-3.522, p=0.278); 1.15 for Chinese population (95% C.I. =0.862-1.545, p=0.335) and 1.03 for Indian (95% C.I. =0.301-3.496, p=0.968). CYP2C19*3 OR in Chinese population is 1.34 (95% C.I. =0.830-2.155, p=0.231) and 0.77 (95% C.I. =0.172-3.394, p=0.724) for Malay population. No CYP2C19*3 was detected in both cohorts of Indian patients and healthy controls. Conclusions: CYP2B6*6 and CYP2C19*2 polymorphisms may confer a risk for breast cancer development in Singaporean breast cancer patients. This is an exploratory study to identify potential breast cancer susceptibility gene polymorphisms, a bigger sample size study could be done to corroborate these findings in future studies.