Novel mediators of cell-cell fusion in triple negative breast cancer

Ploidy altering mechanisms such as cell-cell fusion and whole genome doubling (WGD) can drive intratumoral heterogeneity and alter chemotherapeutic response. Understanding the causes and consequences of these mechanisms is especially important in triple negative breast cancer (TNBC) which accounts for 15-20% of diagnosed breast cancers and does not have targeted treatment options. We hypothesize that ploidy altering mechanisms are a driving force behind intratumoral heterogeneity and can function as active escape or damage recovery mechanisms to allow cells to resist chemotherapy. Our previous data show that even rare homotypic fusion events in TNBC cells can result in durable aneuploidy, enhanced motility, and therapeutic resistance, highlighting a need to uncover the molecular regulators of this process. The central objective of this proposal is to identify and validate gene activators of cancer cell-cell fusion that contribute to CIN and tumor evolution in TNBC. In Aim 1, we will perform a pooled CRISPRa screen in TNBC cells to discover genes whose activation promotes homotypic cell-cell fusion, using a dual-fluorescent coculture system and targeted sgRNA sequencing to quantify enrichment in fusion-derived populations. In Aim 2, we will develop a live-cell imaging pipeline to track fusion dynamics and perform a small-scale arrayed CRISPRa screen to validate the top candidate drivers of Aim 1. Together, these studies aim to reveal novel, targetable regulators of cell-cell fusion in TNBC, offering new therapeutic options to block TNBC progression. This project is a focused, two-year effort to identify candidate regulators of a novel, understudied process. We envision that this work will generate strong preliminary data for a detailed mechanistic investigation of cancer cell-cell fusion (through an R01 or similar application) in the future. Project Number: 1R03CA313537-01 | Fiscal Year: 2026 | NIH Institute/Center: National Cancer Institute (NCI) | Principal Investigator: Amy Brock | Institution: UNIVERSITY OF TEXAS AT AUSTIN, AUSTIN, TX | Award Amount: $150,898 | Activity Code: R03 | Study Section: Special Emphasis Panel[ZRG1 BTC-T (80)] View on NIH RePORTER: https://reporter.nih.gov/project-details/11359786