Castration-resistant prostate cancer (CRPC) poses a significant challenge in management due to its resistance to conventional therapies. Cellular senescence is closely associated with tumor resistance, and neuregulin-1 (NRG1) plays a critical role in regulating cell proliferation and survival. This study investigates the potential of NRG1 in reversing drug resistance in CRPC, by examining its effects on androgen receptor (AR) expression and its involvement in cellular senescence through the modulation of the p27, p16, and ATF4 signaling pathways.

The CRPC model, designated as LNCaP Enzalutamide-resistance (Enz-R), was established by treating LNCaP cells with 10 μM enzalutamide for over 6 months, followed by maintenance in media containing 5 μM enzalutamide. The expression of NRG1 in both cell lines was analyzed using enzyme-linked immunosorbent assay (ELISA), western blotting, reverse transcription polymerase chain reaction, and immunofluorescence. After stimulation with NRG1, beta-galactosidase activity was assessed through senescence-associated staining, and ELISA was performed to evaluate the expression of key senescence-associated factors, including IL-6, IL-8, and IL-1. Both cell lines were stimulated with a high dose of NRG1 (100 ng/ml) and treated with inhibitors targeting p21, p27, and ATF4.

As shown in the figure, panel (A), in LNCaP cells, high-dose NRG1 stimulation led to a significant reduction in IL-6 and IL-8 expression. When the cells were treated with inhibitors, both the p21 and ATF4 inhibitors displayed expression patterns consistent with those observed with NRG1 stimulation alone. However, treatment with the p27 inhibitor reversed the NRG1-induced reduction in IL-6 and IL-8 levels. Similar results were observed in the CRPC model (panel B), where high-dose NRG1 stimulation significantly reduced the expression of IL-6 and IL-8. When different inhibitors were introduced, the expression patterns with p21 and ATF4 inhibitors were consistent with those seen with NRG1 stimulation alone. However, treatment with the p27 inhibitor reversed the NRG1-induced reduction in IL-6 and IL-8 levels. In panel (C), both cell lines were subjected to senescence-associated staining following treatment with different inhibitors after NRG1 stimulation. While p21 and ATF4 inhibitors did not significantly alter the senescence induced by NRG1 stimulation, the p27 inhibitor reversed the NRG1-induced senescence.

Our study demonstrates that NRG1 plays a pivotal role in regulating the AR expression and cellular senescence in both LNCaP and LNCaP Enz-R cell lines. Our findings also suggest that targeting p27 may represent a potential therapeutic approach to modulate senescence and AR expression in prostate cancer, particularly in castration-resistant models. Further investigation into p27's role could provide new insights for improving treatment strategies in advanced prostate cancer.