Abstract C56: The role of BetaB2-crystallin in progression of colorectal and breast cancers in African Americans
Authors: Bumpers Harvey L. , Katkoori Venkat , Chen Dongquan , Manne Upender 
Published: May 2015

Purpose: African-American (AA) breast cancer (BC) and colorectal cancer (CRC) patients experience higher mortality rates than Non-Hispanic Caucasian (CA) patients. These disparities are thought to be due to race/ethnicity-specific tumor molecular biology. Our initial gene expression investigations have identified a Beta B2-Crystallin (CRYBB2) gene that is preferentially over-expressed in CRC of AA patients. However, the precise role of CRYBB2 in aggressiveness of CRC and BC has not been examined. Therefore, we hypothesize that biological mechanism linked to CRYBB2 could contribute to the disparate progression of CRC and BC in AA patients.

Experimental Design: Gene expression studies were performed using Affymetrix Human Genome U133 Plus 2.0 arrays and mRNA samples extracted from 10 fresh frozen Stage III CRCs (5 from AA and 5 from CA) that were previously analyzed for the microsatellite instability (MS) status. Established CRC (HT29 and SW480) and BC (MBA-MD 231) cell lines were used to examine the phenotypic expression of CRYBB2. Also, paired lesions of human CRC (hCRC) and human mice CRC (hmCRC) xenograft were assessed for CRYBB2 by western blot and immunofluorescence (IF). To study the involvement of CRYBB2 in CRC and BC biology, siRNA mediated gene silencing was used to inhibit CRYBB2 expression. The apoptosis of CRC and BC cells after knockdown of CRYBB2 was analyzed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. The epithelial-mesenchymal transition (EMT) of CRC and BC cells was analyzed by western blot for E-cadherin, MM9 and vimentin expression. Western blot analysis was performed on lysates of CRC and BC cells to assess the effect of CRYBB2 knockdown for expression/ activation of the AKT, and mitogen-activated protein kinase pathway proteins.

Results: Our microarray analyses have suggested that several key genes involved in tumor metastasis (CRYBB2, VSNL-1and PFN2) are up-regulated in MS-CRCs of AA but down regulated in MS-CRCs of CA patients. The phenotypic expression of CRYBB2 was found to be higher in CRC tissues as compared to matching normal tissues. Over-expression of CRYBB2 correlated with metastatic CRC and N-cadherin expression and the expression of CRYBB2 was substantially increased in metastatic lesion of CRC and BC xenografts as compared to the primary tumors. Knockdown of CRYBB2 induced apoptosis in CRC and BC cells. In addition, Knockdown of CRYBB2 suppressed EMT signatures, such as decreasing the expression of MMP9, vimentin (mesenchymal markers) and increasing the expression of E-cadherin (epithelial marker). Furthermore, depletion of CRYBB2 decreased the phosphorylation of AKT (p-AKT) in CRC and BC cells. CRYBB2 was mainly localized in cytoplasm of BC and CRC cells.

Conclusions: Our data suggest that CRYBB2 inhibits apoptosis, activates EMT process and AKT phosphorylation by which it contributes the aggressiveness of CRC and BC. It may serve as a promising biomarker for identifying CRC and BC patients at high risk for metastases. It may also be useful as a therapeutic target to inhibit the growth and metastasis of CRC and BC. These studies are supported by NIH/NCI funds (R21-CA171251 and U54- CA 118948).

Citation Format: Harvey L. Bumpers, Venkat Katkoori, Dongquan Chen, Upender Manne. The role of BetaB2-crystallin in progression of colorectal and breast cancers in African Americans. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C56. doi:10.1158/1538-7755.DISP13-C56