Abstract PR006: The racial disparity-linked gene CRYβB2 alters cell adhesion and tumor microenvironment to promote proliferation and invasion in triple-negative breast cancer
Authors: Waly Amr A. , Harper London , Fleming Jodie M. , Costantini Lindsey M. 
Published: January 2023

Abstract
Background: Clinical and epidemiological data showed that African American (AA) women suffer higher incidence and mortality rates due to triple-negative breast cancer (TNBC) compared to European American (EA) women. These disparate disease outcomes are attributed to multiple factors including socioeconomic status, access to health care, and earlier disease onset. However, a growing body of evidence also shows the existence of different gene expression signatures and tumor microenvironments between these patient racial groups. We and others identified CRYβB2 as a cancer racial disparity gene that has higher expression in AA patients with breast, colon, and prostate cancers. We previously demonstrated, via in vitro and in vivo studies, that CRYβB2 promotes proliferation, metastasis, and IL-6 signaling. The objective of the current research is to identify the cellular and molecular mechanisms downstream of CRYβB2 leading to its tumor-promoting phenotypes. Methods: CRISPR/Cas9 and lentiviral knock-in gene editing tools were used to create TNBC cell lines with CRYβB2 knockout and overexpression respectively. The functional consequences of CRYβB2 were assessed in vitro using colony formation, tumor spheroid invasion, and collagenase activity assays. Additionally, tumor spheroids were grown and RNA sequencing (RNA-seq) was performed to assess the effect of CRYβB2 on gene expression. Results: Herein, functional assays showed that CRYβB2 promotes proliferation and invasion in vitro in both AA and EA cell lines. RNA-seq and Gene Ontology enrichment analyses revealed that CRYβB2 alters key pathways such as cell adhesion and extracellular matrix (ECM) organization. RT-qPCR validation also showed that CRYβB2 inhibits the expression of a specific class of adhesion molecules known as protocadherins (PCDHs). Downregulation of PCDHs has been shown to enhance tumor progression and is a predictive marker for low survival in many cancer types. Indeed, data mining of publicly available data shows that three of the identified PCDHs (PCDHGB5, PCDHGB6 and PCDHGB7) have significantly lower expression levels in breast cancer compared to normal tissue and their low expression leads to low overall survival. Furthermore, RNA-seq data showed that CRYβB2 promotes the expression of multiple matrix metalloproteinase (MMP) genes. This was functionally validated using collagenase activity assay where CRYβB2 enhanced collagen degradation in vitro. Conclusions: Our findings provide a mechanistic explanation for the role of CRYβB2 in driving disparate clinical outcome among AA and EA TNBC patients. We demonstrate a paradigm where high CRYβB2 expression promotes tumor progression by suppressing cell adhesion molecules and increasing ECM degradation to enhance tumor growth, invasion, and metastasis. Disclaimer: This work was prepared while Jodie Fleming was employed at NCCU. The opinions expressed in this article are the author's own and do not reflect the view of the National Institutes of Health, the Department of Health and Human Services, or the United States government.
Citation Format: Amr A. Waly, London Harper, Jodie M. Fleming, Lindsey M. Costantini. The racial disparity-linked gene CRYβB2 alters cell adhesion and tumor microenvironment to promote proliferation and invasion in triple-negative breast cancer [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PR006.