Abstract Triple-negative breast cancer (TNBC) tumors lack estrogen receptor-α (ERα), progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER2) overexpression. Consequently, current targeted therapies for ER-positive or HER2 overexpressing tumors have little efficacy for these biologically heterogenous tumors. TNBCs are highly metastatic and tend to overexpress insulin-like growth factor-2 (IGF2), a hormone that stimulates pro-survival signaling pathways when bound to the tyrosine kinase receptors, insulin receptor isoform A (IR-A) and insulin-like growth factor-1 receptor (IGF1R). The proliferative action of IGF2 is inhibited by BMS-754807 both in vitro and in vivo. Flow cytometry analysis confirms the pro-apoptotic effect of the BMS-754807 on MDA-MB-468 TNBC cultures. The percentage of Annexin-V positive/7-AAD negative cells (early apoptosis) is significantly elevated in the BMS-754807 and IGF2+BMS-754807 groups compared to the control and IGF2-treated groups (p0.01, one-way ANOVA with post-hoc Tukey test). Late apoptotic cells (Annexin-V positive/7-AAD positive) are twice as high in BMS-754807 and IGF2+BMS-754807 groups compared to the control and IGF2-treated groups (p0.05, one-way ANOVA with post-hoc Tukey test). We hypothesize that BMS-754807 antagonizes the pro-survival effects of IGF2 on TNBC cells, partially through the regulation of small extracellular vesicles (sEV) number and/or vesicular cargo (e.g. IGF2 receptor (IGF2R), IGF cascade proteins). The sEV obtained from MDA-MB-468 cultures treated with BMS-754807 have a 20% - 100% increase of CD63 levels, a tetraspanin protein that is a marker for sEV and plays a role in cell-cell communication and cargo sorting. Proteomic analysis reveals detectable nSMase2 (SMPD3), an enzyme responsible for ceramide generation, in sEV obtained from BMS-754807 and IGF2+BMS-754807 treatment groups. BMS-754807- induced activation of nSMase2-dependent exosome release may alter sEV number and composition. Moreover, an increase in intracellular ceramide levels may lead to apoptosis. Additionally, a strong enrichment of sEV-associated insulin-degrading enzyme (IDE) and IGF-binding protein-2 (IGFBP2) are observed in IGF2+BMS-754807 cultures. Both proteins can reduce the effect of IGF2 on TNBC tumor cells, either by degrading the growth factor (IDE) or by preventing its binding to cellular receptors (IGFBP2). Although sEV-associated IGF2R levels were not significantly different between treatment groups, IGF1R was exclusively detected in sEV fractions from cultures treated with BMS-754807 and IGF2+BMS-754807. At time when targeted treatments for TNBC are urgently needed, these data suggest that BMS-754807 inhibits TNBC tumor growth and stimulates apoptosis not only through inhibition of IGF1R/IR signaling but also by increasing sEV with vesicular cargo that inhibit IGF2 availability. (Funding by RWJF 69352; NCI U54 CA143930; CBCRP 24IB-0053 UCLA JCCC BC Award, UCLA TDG, Team Research Grant, CIRM DISC2-14166, UCLA SON Pilot Grant) Citation Format: Mikhail Melnik, PhD, Tina Bilousova PhD, Diana C. Márquez-Garbán, MD, Neda A. Moatamed, MD, Mario Morales Martinez, PhD, Richard J. Pietras, MD, PhD, Karen Gylys, PhD, MS, BSN, Nalo M. Hamilton, PhD, MSN, APRN-BC. BMS-754807 inhibits the survival of triple-negative breast cancer tumors by regulating cargo in small extracellular vesicles (sEV) abstract. In: Proceedings of the 18th AACR Conference on the Science of Cancer Health Disparities; 2025 Sep 18-21; Baltimore, MD. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2025;34(9 Suppl):Abstract nr A040.
Melnik et al. (Thu,) studied this question.