Novel antibody cocktail therapy targeting extracellular tumor-specific mutations to treat triple-negative breast cancer

Background Treatment options for triple-negative breast cancer (TNBC) remain limited, and the highly heterogeneous nature of these tumors often contributes to therapeutic resistance. While we have previously demonstrated that preparing a cocktail of antibodies targeting multiple distinct mutated cell surface proteins (MSPs) harboring neoepitopes unique to a given tumor can effectively disrupt tumor growth in mice, the feasibility of this approach in treating TNBC has yet to be tested. Methods We used the murine EMT6 cell line to model TNBC, comparing the EMT6 cell genome to that of parental BALB/c mice to guide the production of polyclonal antibodies (pAbs) targeting 12 different EMT6-specific MSPs. Antibody binding to purified peptides, EMT6 cells, and healthy tissues was assessed through immunofluorescence staining. EMT6 tumor-bearing mice were established and treated with a pAb cocktail in combination with anti-PD-1, and tumor growth and survival were monitored. A bioinformatics-based survey of genomic data from TNBC patients in The Cancer Genome Atlas (TCGA) database was conducted to assess MSP prevalence. Results Of the 12 pAb preparations, 9 successfully bound to EMT6 cell surfaces in a cumulative manner without detectable non-tumor binding. When we administered a cocktail of these 9 MSP-targeting pAbs to EMT6 tumor-bearing mice, delayed tumor growth and improved survival were observed. Analyses of the TCGA cohort of TNBC patients revealed that the tumors of a larger proportion of these patients harbored > 10 MSPs as compared to individuals with other forms of breast cancer (69% vs. 42%), making them particularly good candidates for MSP-specific antibody cocktail treatment. Conclusions Together, these results highlight the promise of using antibodies directed against MSPs expressed by TNBC tumor cells to kill tumor cells in vivo , providing a unique approach to individualized cancer patient care with the potential to achieve superior patient outcomes through the elimination of heterogeneous tumor cell populations.