Beatriz M. Morales-Cabán
Ivette J. Suarez-Arroyo

Department of Biochemistry, School of Medicine, Universidad Central del Caribe, Bayamón, Puerto Rico

Introduction

Triple-negative breast cancer (TNBC) is a heterogeneous and aggressive subtype of breast cancer characterized by the absence of estrogen and progesterone receptors and HER2 expression. These characteristics hinder diagnosis and treatment, highlighting the need for targeted therapies. Recent studies have identified secretory carrier membrane protein 3 (SCAMP3) as a key regulator of breast cancer progression and oncogenic pathways. In this study, we aim to investigate the role of SCAMP3 in regulating the oncogenic extracellular signal-regulated kinase (ERK 1/2) activity and its contribution to TNBC survival and proliferation.

Methods

To this end, we used wild-type (WT) and SCAMP3 knockout (SC3KO) SUM-149 TNBC cells to assess cell viability, cell cycle progression, and cell death pathways by western blot.

Results

After 24h of treatment with ERK inhibitor MK-8353 (0.062µM–64µM), SC3KO cells exhibited slightly higher IC50 value (2.1µM) compared to WT cells (1.7µM), suggesting a reduced sensitivity to ERK inhibition. Treatment with 1µM MK-8353 for 24h induced cell cycle arrest at G0/G1 in SC3KO cells, increased the expression of cyclins D and B, and decreased cyclin E. To assess cell death, we treated cells with 2µM MK-8353 for 24 hours and monitored caspase-3 and PARP1. Our results showed that treatment reduced caspase-3 levels, although cleaved caspase-3 was undetectable. In contrast, ERK inhibition induced cleavage of PARP1 in both WT and SC3KO cells, with a significantly higher increase observed in SC3KO cells.

Conclusion

Taken together, these findings suggest that knockout of SCAMP3 potentiates the effect of ERK inhibition, impairs proper cell cycle progression, and promotes TNBC cell death by apoptosis or through alternative pathways. This study highlights the potential of SCAMP3 as a therapeutic target for TNBC patients.

Funding

This work was supported in part by NIH/NIGMS (SC2GM141720), PRSTRT under agreement #2024-00198, UCC-GPBS, and the UCC-RISE program.