SLFN11 Enhances PARPi Sensitivity in Ovarian Cancer via Ubiquitin-Mediated Stabilization

Schlafen family member 11 (SLFN11), implicated in cancer drug resistance, may improve poly(ADP-ribose) polymerase inhibitor (PARPi) efficacy. This study investigates SLFN11's role in epithelial ovarian cancer (EOC) progression and its influence on PARPi sensitivity, particularly in BRCA-wild-type contexts, with a focus on its emerging function in proteostasis regulation. SLFN11 expression in EOC and adjacent tissues was evaluated via immunohistochemistry, quantitative polymerase chain reaction (PCR), and Western blot. Functional assays-including cell viability, transwell migration, wound healing, and colony formation-assessed SLFN11's effects on SKOV3 cells (BRCA-wild-type) proliferation and invasiveness. PARPi sensitivity in SKOV3 cells with SLFN11 knockdown or overexpression (OE) was tested using Cell Counting Kit (CCK)-8 and Terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) assays. Protein stability and ubiquitination levels of PARP1/2 were analyzed as the central mechanism. SLFN11 mRNA and protein levels were markedly lower in EOC tissues compared with normal tissues. Silencing SLFN11 enhanced EOC cell proliferation, migration, and invasion, whereas OE inhibited these malignant behaviors. SLFN11 knockdown reduced PARPi-induced apoptosis and drug sensitivity, while its OE amplified these responses. Mechanistically, we demonstrate that SLFN11 suppresses global proteotoxic ubiquitination, thereby specifically stabilizing PARP1/2 proteins and potentiating PARPi-mediated DNA damage through enhanced chromatin trapping. SLFN11 enhances PARPi sensitivity in EOC by stabilizing PARP1/2 via inhibition of proteotoxic ubiquitination, supporting its role as a biomarker in a BRCA-wild-type EOC cell model where PARPi efficacy is limited by intrinsic resistance. While the application of PARPi in other subtypes of EOC still requires further validation, SLFN11 may improve PARPi response and could be explored as a strategy to address PARPi resistance.