B-068 Functional inhibition of target YB1 via rationally designed ligand library for mechanistic biomarker validation in triple negative breast cancer models

Abstract

Breast cancer is one of the leading causes of death worldwide. Triple negative breast cancer accounts for 10-15% of all the breast cancer cases, and it is the most aggressive form. YB1 is a multifunctional protein that plays a major role in tumor progression, drug resistance, and metastasis in multiple cancers. Yb1 overexpression correlates with aggressive oncologic phenotypes, but its translation to functional biomarkers is constrained by lack of small molecule inhibitors for mechanistic perturbation studies. So, it is important to synthesize small molecule YB1 inhibitors to understand the functional role of YB1 as a biomarker. A curated library of 40 novel compounds is obtained from a multi-step synthetic process by incorporating chemically diverse compounds that yield potential YB1 inhibitors. All the compounds’ structures are characterized by hydrogen and carbon NMR, HPLC, and LC-MS. Later, functional screening is performed through the MTT cell viability assay in human and murine cell lines with YB1 overexpression and in the breast cancer cell line in which the YB1 is not overexpressed to evaluate the selectivity. Dose-response curves are generated, and IC50 values are obtained through non-linear regression models. Biological assay is performed thrice to ensure experimental robustness. Out of all the forty compounds, only a subset of compounds showed increased dose-dependent antiproliferative activity along with elevated selectivity towards YB1 protein. IC50 values for the drugs that have increased activity are valued below 5 µM and have a selectivity of greater than 100. The structure optimization revealed that the fluorine groups on the compounds contribute to increased activity. These results and future experiments help us understand the mechanistic target evaluation. This work provides the synthetic platform of YB1 inhibitory molecules that help with the mechanistic evaluation of YB1. These small molecules aid in assay development, mechanistic validation, and translational biomarker studies. In the future, we would like to explore more of the YB1 mechanism of action through these compounds.