Gene expression as a biomarker of responsiveness: A personalized therapeutic approach towards metastatic breast cancer patients on cdk4/6 inhibitor

Objective of the study is to assess whether gene (mRNA) expression of Retinoblastoma Susceptibility Gene Product (Rb) signature and CCNE1, the gene encoding cyclin E1 can be used as markers of responsiveness to CDK4/6 inhibitors in metastatic breast cancer patients In this cross-sectional study, eighty metastatic breast cancer patients with positive estrogen and progesterone receptor responses, but negative HER2, on CDK4/6 inhibitors will be recruited. Five ml of EDTA blood samples will be collected. Expression of genes, CCNA2(cyclin 2), MCM7 (mini chromosome maintenance complex component 7) and CCNE1(Gene encoding cyclin E1) will be analyzed by following steps; i.isolation of RNA ii.cDNA synthesis by reverse transcription iii. Quantification by real time PCR.2 ml of blood will be collected in plain vials for Estimation of CCNA2, MCM7 and CCNE1 levels in serum samples.Chisquare test will be done to find the association of gene expression and serum levels of biomarkers of response (BoR) with the outcome CDK4/6 inhibitor therapy. Biomarkers for response to CDK4/6 inhibitors in breast cancer patients may be helpful in differentiating responders and non-responders. This may open up a personalized therapeutic approach in breast cancer patients.