SYT4 binds to SNAP25 to facilitate exosomal secretion and prostate cancer enzalutamide resistance

Prostate carcinoma represents a predominant malignancy affecting the male population, with androgen deprivation therapy (ADT) serving as a critical therapeutic modality for advanced disease states, but it often leads to the development of resistance. Enzalutamide (Enz), a second-generation antiandrogen drug, initially offers substantial therapeutic benefit, but its efficacy wanes as drug resistance ensues. In this study, we found that synaptotagmin 4 (SYT4) is an upregulated gene in enzalutamide-resistant (EnzR) cell lines. The downregulation of SYT4, in combination with enzalutamide therapy, substantially enhances the antiproliferative effect on resistant prostate cancer cells beyond the capacity of enzalutamide monotherapy. SYT4 promotes vesicle efflux by binding to the synaptosome-associated protein 25 (SNAP25), thereby contributing to cell resistance against enzalutamide. The elevated expression of SYT4 is mediated by bromodomain-containing protein 4 (BRD4), and BRD4 inhibition effectively suppressed the expression of SYT4. Treatment with a therapeutic dose of enzalutamide combined with ASO-1, an antisense oligonucleotide drug targeting SYT4, shows promising results in reversing the resistance of prostate cancer to enzalutamide.