The pterocarpan (+)-PTC modulates cytoskeletal proteins and induces apoptosis in metastatic castration-resistant prostate cancer: a proteomic perspective.

Treatment of metastatic, castration-resistant prostate cancer (mCRPC) remains clinically challenging due to tumor heterogeneity and resistance to standard microtubule-targeting agents, such as docetaxel and cabazitaxel. The natural pterocarpan (+)-(6aS,11aS)-2,3,9-trimethoxypterocarpan [(+)-PTC] has previously shown selective cytotoxicity and disruption of bipolar spindle assembly in mCRPC PC-3 cells yet its full mechanism of action and global proteomic impact remain uncharacterized. PC-3 cells were treated with (+)-PTC (2.0 µM or 8.0 µM) for 24 h and assessed by flow cytometry (Annexin V and rhodamine 123) Western blot, and caspase-3/7 luminescence assays. Global proteomic profiling was performed by quantitative LC-MS/MS using a 2D nano-UPLC data-independent acquisition platform with nocodazole (0.25 µM, microtubule depolymerizer) and monastrol (50 µM, Eg5 inhibitor) as comparators. (+)-PTC-induced concentration-dependent apoptosis (19.8% early apoptotic cells at 2.0 µM; 26.1% at 8.0 µM) and progressive mitochondrial membrane depolarization. Western blot and caspase activities assays confirmed upregulation of BAX and caspase-7, consistent with intrinsic pathway activation. Proteomic analysis identified 212 differentially expressed proteins (DEPs) in (+)-PTC-treated cells, with over 80% overlap with nocodazole-treated cells (82% among upregulated and 84% among downregulated proteins), while clustering with monastrol was markedly lower. The top upregulated proteins, TTLL3, ANAPC7, PIK3CA, ARID4B, and COL16A1, are linked to microtubule dynamics and cell cycle regulation; the main downregulated, namely KDM2B, PTOV1, YWHAQ, PSMB6, and PRKCB, are involved in cell survival, protein homeostasis and mitotic checkpoint control. These findings provide proteomic evidence that (+)-PTC interferes with cytoskeletal protein dynamics and promotes apoptosis in mCRPC and so warranting its further investigation as a candidate anti-cancer scaffold.