Analysis of CHRNA5 expression in breast cancer cell lines in response to serum starvation and estrogen treatment
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Breast cancer is a complex disease that can be classified into distinct molecular subtypes including Basal, Luminal A, Luminal B and HER2 positive. These molecular subtypes mainly differ in their hormone receptor expression and response to treatment. This makes the discovery of new molecular markers for further classification important. Cholinergic nicotinic acetylcholine receptors are ion channels involved in smoking behavior, neurodegenerative diseases and cancer. Cholinergic nicotinic receptor alpha 5 (CHRNA5) has been associated with nicotine addiction and recently with lung cancer yet its importance in breast cancer remains relatively unexplored. In the present study, a panel of 10 breast cancer cell lines were used for quantification of isoform-specific CHRNA5 expression using qPCR. Changes in CHRNA5 expression in response to serum starvation and estrogen treatment were assessed. qPCR showed that CHRNA5 was alternatively spliced, with at least five different isoforms in breast cancer cell lines. qPCR analysis for CHRNA5 expression in serum treated and serum starved cells were analyzed after outlier detection and exclusion; and statistical tests included ANCOVA using geometric mean of TPT1 and SDHA, as reference genes. Our results demonstrated that, CHRNA5 expression differed between different subtypes of breast cancer cell lines. CHRNA5 expression significantly responded to serum starvation in ZR75-1 and MDA-MB-157 cell lines, isoform specifically. Isoform expression of CHRNA5 exhibited significant alterations upon estrogen treatment in a dose and time-dependent manner. Expression of 1000bp variant, isoform2 and isoform3 of CHRNA5 significantly increased upon E2 treatment and total CHRNA5 and isoform2 CHRNA5 increased in expression at 24 hours when compared with 12 hours of treatment. Our findings show that CHRNA5 has multiple isoforms in breast cancer, with potential to be modulated by serum starvation and estrogen treatment in a cell-specific manner.