Vibhavi Chinthalapudi
Research Mentor: Deeksha Sharma
Mentor Department: Internal Medicine, Medicine
Author(s): Vibhavi Chinthalapudi, Deeksha Sharma, Monica Burness
Session: Session 1 (9:00 AM – 9:50 AM)
Presentation Type: Poster 124
Abstract
Fibroblasts are stromal cells within the tumor microenvironment (TME) that produce extracellular matrix components and regulate tumor growth. In cancer, fibroblasts differentiate into cancer-associated fibroblasts (CAFs), which promote tumor progression by remodeling the extracellular matrix and secreting factors that enhance cancer cell invasion. Although current cancer therapies have reduced breast cancer mortality by eliminating the majority of tumor cells, CAFs often evade treatment and persist within the TME, contributing to disease progression and therapy resistance. This highlights the need for therapeutic strategies that specifically target the TME. The bromodomain and extraterminal domain (BET) family of proteins BRD2, BRD3, and BRD4 regulate gene expression through super-enhancer complexes and are essential for tumor cell survival, making them promising therapeutic targets. Previous work from the Burness laboratory demonstrated that the BET protein degrader ZBC260 suppresses tumor cell growth and cancer stem cell populations by altering the TME(depletion of CAFs). However, the direct effects of BET protein inhibition on CAFs remain unclear. Here, we investigate how BET proteins regulate CAF differentiation, and viability . ZBC260 was tested in plain murine mammary fibroblast (PMMF) cells, with CAF differentiation induced using tumor conditioned media (TCM) from the murine breast cancer D2A1 cell line. CAF-like differentiation was assessed by marker gene expression, while ZBC260’s effect on viability was evaluated using MTT assays. After 72 hour treatment, MTT assays on PMMF cells showed no significant difference in cell viability between the control and tumor-conditioned media(TCM), but ZBC260 significantly reduced the viability(p<.0001), suggesting that ZBC260 is inhibiting fibroblast cell growth. e. Another MTT assay comparing ZBC260 concentrations suggests that this effect is not dose dependent. Further, PMFF cells differentiation was evaluated by qPCR analysis that revealed that TCM upregulated CAF markers (COL1A1. COL3A1, ACTA-2, and TNC), suggesting successful fibroblast cell differentiation. Furthermore, we checked if ZBC260 inhibits this TCM induced PMFF cell differentiation and observed that treatment with ZBC260 significantly (p<0.05) reduced the tested marker expression. In conclusion, these findings indicate that ZBC260 inhibits fibroblast differentiation into a CAF-like phenotype and may suppress pro-tumor activity within the TME.
