Background In the USA, the breast cancer mortality rate is 41% higher for African-American women than non-Hispanic White women. While numerous gene expression studies have classified biological features that vary by race and may contribute to poorer outcomes, few studies have experimentally tested these associations. CRYβB2 gene expression has drawn particular interest because of its association with overall survival and African-American ethnicity in multiple cancers. Several reports indicate that overexpression of the CRYβB2 pseudogene, CRYβB2P1, and not CRYβB2 is linked with race and poor outcome. It remains unclear whether either or both genes are linked to breast cancer outcomes. This study investigates CRYβB2 and CRYβB2P1 expression in human breast cancers and breast cancer cell line models, with the goal of elucidating the mechanistic contribution of CRYβB2 and CRYβB2P1 to racial disparities. Methods Custom scripts for CRYβB2 or CRYβB2P1 were generated and used to identify reads that uniquely aligned to either gene. Gene expression according to race and tumor subtype were assessed using all available TCGA breast cancer RNA sequencing alignment samples (n = 1221). In addition, triple-negative breast cancer models engineered to have each gene overexpressed or knocked out were developed and evaluated by in vitro, biochemical, and in vivo assays to identify biological functions. Results We provide evidence that CRYβB2P1 is expressed at higher levels in breast tumors compared to CRYβB2, but only CRYβB2P1 is significantly increased in African-American tumors relative to White American tumors. We show that independent of CRYβB2, CRYβB2P1 enhances tumorigenesis in vivo via promoting cell proliferation. Our data also reveal that CRYβB2P1 may function as a non-coding RNA to regulate CRYβB2 expression. A key observation is that the combined overexpression of both genes was found to suppress cell growth. CRYβB2 overexpression in triple-negative breast cancers increases invasive cellular behaviors, tumor growth, IL6 production, immune cell chemoattraction, and the expression of metastasis-associated genes. These data underscore that both CRYβB2 and CRYβB2P1 promote tumor growth, but their mechanisms for tumor promotion are likely distinct. Conclusions Our findings provide novel data emphasizing the need to distinguish and study the biological effects of both CRYβB2 and CRYβB2P1 as both genes independently promote tumor progression. Our data demonstrate novel molecular mechanisms of two understudied, disparity-linked molecules.

Research demonstrates young African American (AA) women have higher mortality rates for triple-negative breast cancer (TNBC), despite lower incidence rates, when compared to Caucasian American (CA) women. These disparate poor patient outcomes may be attributed to access to quality care, socioeconomic status, education, or geographic location. However, numerous other studies have demonstrated that gene expression differences may also contribute to the higher mortality rates experienced by AA women, suggestive of biological differences among these two patient populations. Consequently, CRYBB2 is one gene that has consistently been associated with AA race in normal and malignant tissues. Although, its basic function in these tissues is currently unknown, higher expression of CRYBB2 is significantly correlated with poor outcome in breast, colorectal and prostate cancers in AAs. We analyzed all publically available gene expression datasets from studies focused on breast cancer health disparities and discovered that all probes detected CRYBB2 as well as its pseudogene, CRYBB2P1. It is becoming increasingly clear that pseudogenes have the ability to modify the mechanisms of their functional parental genes. However, it remains unclear whether the high expression of CRYBB2, CRYBB2P1, or both, affect cell behaviors to alter disease progression. Herein, we investigated the biological consequences of CRYBB2 and CRYBB2P1 in three basal-like TNBC cell lines (SUM159, MDA-MB-231, Hs578t) using CRISPR/Cas9 and overexpression technologies. The functional consequence of CRYBB2 and CRYBB2P1 expression were evaluated using in vitro and biochemical assays, as well as in vivo tumorigenesis studies. Our findings demonstrate overexpression of CRYBB2 and CRYBB2P1 alter cell proliferation, cytokine and growth factor production, and tumorigenesis. This data highlights the potential molecular mechanisms by which CRYBB2 and CRYBB2P1 contribute to poor patient outcome. Citation Format: Maya A. Barrow, Megan E. Martin, Denise K. Reaves, Breanna Jeffcoat, Ginger R. Smith, Michael Tarpley, Kevin P. Williams, Jodie M. Fleming. Race-associated breast cancer disparities: The role of CRYBB2 and its pseudogene [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4058.