Identification of Novel Small Molecule Kinase Antagonists of the Prolactin Receptor In Breast Cancer

Abstract

Breast cancer remains to be a prevalent malignancy, as an estimated 231,840 women were diagnosed in the US in 2015. Furthermore, cancer cells have developed chemoresistance, necessitating the pursuit of innovative targets. Prolactin (PRL) acting via the prolactin receptor (PRLR) is an anti‐apoptotic hormone in breast cancer. Extensive research indicates that PRLR activation in breast cancer is associated with enhanced tumor growth, invasiveness, metastasis, and resistance to chemotherapy.To identify novel antagonists of the PRLR, a 340,000 small molecule library was scanned using high throughput screening and computational modeling techniques (in‐silico docking) to observe binding potential to the PRLR. Kd and IC50 values were found using cell based assays for testing ligand binding efficiency in T47D and Ba/F3 cell lines. 2 molecules, SMI 1 and SMI 6, were identified as potential inhibitors of the PRLR. Inhibitor cytotoxicity was tested using an LDH assay, utilizing a 468 cancer cell line, to ensure drug viability as a potential treatment. An invasion assay was produced to test cell invasion when exposed to 1nM prolactin in a 468 cell line. Immunoprecipitation and western blotting were used to observe downregulation of the PRLR signaling pathway. Cancer cell proliferation after inhibitor exposure was calculated using flow cytometry.Results indicated SMI 1 and 6 had minimal toxicity, ensuring both molecules' capabilities to be therapeutic agents. Furthermore, both inhibitors reduced cell invasion, and cell proliferation when exposed to prolactin, compared to exposure to prolactin only. Additionally, the inhibitors also appear to downregulate the STAT‐5 signaling pathway. Thus, both these small molecule antagonists hold great promise in targeting the prolactin receptor as potential cancer therapeutic drugs of the future.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.