Time-dependent endogenous Angptl-7 expression in a 4T1 TNBC model

Breast cancer is one of the most frequently diagnosed cancers among women in the United States, with nearly 275,000 new cases each year. Although triple-negative breast cancer (TNBC) accounts for only 10-15% of those diagnoses, it is an aggressive subtype characterized by rapid metastasis and increased necrosis within the primary tumor core. Previous studies found angiopoietin-like protein 7 (A7) to be highly enriched in the tumor core compared to the viable rim in a TNBC mouse model, suggesting that A7 may play a role in driving necrotic activity and metastasis in TNBC. How A7 concentrations fluctuate with time-dependent stress and affect cell death and necrotic activity is unclear. In this study, we show that in 4T1 mouse mammary carcinoma cell lines with varying levels of endogenous A7 expression, A7 over-expressing cells exhibit a marked increase in cell death around hour 100 in culture and greater cell death overall. By performing western blotting and ELISA testing on cell lysates and culture media, we determined that extracellular human A7 secretion increases logarithmically over time, while intracellular A7 levels remain relatively stable. Taken together, these findings indicate that A7 may promote cell death and necrosis in TNBC only after being secreted into the primary tumor core.