EPS8 Differentially Regulates Antioxidant Defense and Mitochondrial Homeostatic Signaling in LNCaP and Enzalutamide-resistant LNCaP Cells.

BACKGROUND/AIM: Epidermal growth factor receptor pathway substrate 8 (EPS8) is an adaptor protein implicated in tumor progression and therapeutic resistance; however, its role in mitochondrial homeostatic signaling and antioxidant regulation remains unclear. This study examined the effects of EPS8 modulation in lymph node carcinoma of the prostate (LNCaP) and enzalutamide-resistant LNCaP (LNCaP-Enz) cells.

MATERIALS AND

METHODS

LNCaP-Enz cells were generated by long-term exposure to enzalutamide and maintained in 5 μM enzalutamide. EPS8 expression was modulated by plasmid-mediated overexpression or shRNA-mediated knockdown. Superoxide dismutase (SOD) activity and cellular adenosine triphosphate (ATP) levels were measured using colorimetric assays. Mitochondrial membrane potential (ΔΨm) was evaluated using JC-1 fluorescence, and mitochondrial staining patterns were qualitatively examined using MitoTracker Green staining. Protein expression associated with antioxidant defense, mitochondrial dynamics, mitochondrial stress response, mitochondrial biogenesis, and AMP-activated protein kinase (AMPK)-mammalian target of rapamycin (mTOR) signaling was analyzed by western blotting.

RESULTS

EPS8 overexpression increased SOD activity and the expression of SOD1 and SOD2, whereas EPS8 knockdown reduced these antioxidant parameters. Conversely, EPS8 silencing increased cellular ATP levels and enhanced JC-1 red fluorescence patterns. EPS8 silencing increased MFN1 and OPA1 expression and reduced DRP1 expression, consistent with a fusion-associated mitochondrial profile. EPS8 silencing also increased SIRT1, PGC-1α, NRF1, TFAM, p-AMPK/AMPK, and p-mTOR/mTOR, but reduced HSP60, LONP1, ATF5, and CEBPβ expression.

CONCLUSION

EPS8 differentially regulates SOD-associated antioxidant capacity and mitochondrial homeostatic signaling in LNCaP-based cell models. Further studies are required to determine whether EPS8 modulation affects enzalutamide responsiveness.