Implication of oral contraceptive use to phenotypic expression pattern of receptors in breast cancer

Abstract

Background: Triple negative breast carcinoma (TNBC) is a breast cancer sub-type associated with high mortality rate and inadequate therapeutic options. Clinical data indirectly implicates where Oral Contraceptive Pill (OCP) usage is high, prevalence of Estrogen Receptor+ (ER+) breast cancer is high and prevalence of TNBC is low. This has lead to our hypothesis that OCP use may add to risk of ER+ breast cancer and OCP use may reduce the risk of TNBC. In in-vitro study we tried to differentiate the effect of estrogen on development of ER+ and triple negative breast cancer tumor affecting Epidermal growth factor receptor EGFR expression in respective cancer cell lines as TNBC commonly displays EGFR. It is known that effective EGFR degradation results in suppression of tumor in various models. Aims and Objectives: We aimed at to comparing the prevalence and association of sub-types of breast cancer in OCP users and OCP non-users among woman 30 to 60 years of age, and in-vitro study we aimed at treating MDA-MB-231 cell lines with Cycloheximide with or without 17β-estrdiol to observe whether 17β-estradiol leads to EGFR degradation. We also aimed at whether degradation occurs through ubiquitination pathway. Methods : This hospital-based observational human study of three year duration included 155 subjects of primary invasive breast cancer who got admitted at our institution. The data was obtained for ER, PR, HER2 condition, clinical classification and data related to demographic factors, reproductive history, and history of OCP use. They were divided into two groups. Group-1 included 48 patients with history of OCP use and group-2 included 107 patients who did not use OCP. In in-vitro study MDA- MB-231 cells were treated with 17β-estradiol (E2) and EGFR expression was evaluated by western blotting at different intervals by using Cycloheximide chase. To gauge ubiquitination pathway of degradation of EGFR in the MDA-MB-231 cell line, MG-132 was utilized. Data was analysed using SPSS-20. Results: A significant increase in prevalence of molecular sub-types ER+, Progesterone Receptor+ (PR+) and Luminal B breast cancers in OCP users was observed compared to non-users. There was considerable decrease in the age at the point of admission in ER+ cancer in OCP users (45.3 years) compared to non-users (52.2years). Whereas in OCP users age at the time of admission of Basal (TNBC) cancer patients (53.1 years) was higher when compared to non-users (45.4years). Logistic regression revealed the likelihood of ER+, PR+ and Luminal B in OCP users was 11%,10% and 13% less respectively with 1 year of higher age against the likelihood of TNBC among OCP users was 18% more and 8% less in non-users. In in-vitro study EGFR expression was reduced with β-estradiol treatment in MDA-MB- 231 cell line with Cycloheximide chase. Upon Treatment with MG-132 and E2, EGFR expression did not reduce suggestive of that Estrogen degrades EGFR by ubiquitination pathway. Conclusions: OCP use may be allied with increase in the prevalence of ER+, PR+ and Luminal B breast cancer. On the contrary OCP use is may be related with delay in the progression of the TNBC. In-vitro study conclusion was that estrogen degrades EGFR in MDA-MB-231 cells and this degradation occurs by ubiquitination