Cancerous Phenotypes Exhibited by NIH/3T3 Fibroblasts Overexpressing BST‐2

Abstract

Oncogenesis is a multistep process initiated by the accumulation of genetic and/or epigenetic changes that culminate in the transformation of normal cells into cancer cells. The genetic and/or epigenetic changes result in dysregulated gene expression signature that may involve key cancer driving genes such as Bone Marrow Stromal Antigen 2 (BST‐2). In this study, we sought to test the hypothesis that BST‐2, a type II transmembrane protein regulates early events of oncogenesis. BST‐2 is a multifaceted protein with both antiviral and proviral functions and has been implicated in promoting aggressive cancer cell behavior such as migration and invasion. Meta‐analysis of breast cancer datasets from The Cancer Genome Atlas (TCGA) show a statistically significant correlation between elevated BST‐2 expression and poor survival. In addition to its role in breast cancer progression, elevated BST‐2 expression correlates with poor prognosis in endometrial, brain, lung, and oral cavity cancers, further implicating elevated BST‐2 expression in cancer progression. However, the role of BST‐2 in regulating early oncogenic events is not well understood. Our approach consisted of stably overexpressing exogenous human BST‐2 in NIH/3T3 mouse embryonic fibroblasts that express very low endogenous mouse BST‐2 to generate 3T3BST‐2 cells. The control cells were stably transfected with pCDNA3.1 to generate 3T3pCDNA cells. The cells were tested for phenotypes associated with early oncogenic events under two‐dimensional (2D) and three‐dimensional (3D) culture conditions. In a confluent 2D monolayer, 3T3BST‐2 cells compared to 3T3pCDNA cells resisted contact inhibition and had enhanced growth and survival that is associated with increased phosphorylated protein kinase AKT (T308), increased phosphorylated mitogen‐activated protein kinase (ERK1/2), and decreased pro‐apoptotic factor Bak. In a 3D spheroids model, 3T3BST‐2 spheroids were larger in area and had higher ATP content, an indication of anchorage‐independent survival. Suspended as single cells in a gel, 3T3BST‐2 cells also had enhanced survival, especially when arginylglycylaspartic acid (RGD) adhesive peptide motif was present. Suppressed contact inhibition and enhanced anchorage‐independent survival suggests that overexpression of BST‐2 contributes to malignant transformation of normal cells. Discerning the mechanisms of BST‐2 mediated oncogenesis will expand our understanding of events that transforms a normal cell into an unwanted cancerous cell, which may potentially form the foundation for the development of BST‐2‐targeted cancer therapies.Support or Funding Information1. Molecular and Cellular Pharmacology PhD program 2. CIE’s IMSD‐MERGE scholars program 3. Scholars in Biomedical Sciences program (SBMS) 4. Stony Brook University Cancer Center