Small-molecule inhibitor HI-TOPK-032 improves NK-92MI cell infiltration into ovarian tumours

The effectiveness of natural killer (NK) cells transferred adoptively in combating solid tumours is limited by challenges such as their difficulty in penetrating tumours from the bloodstream and maintaining viability without the support of interleukin-2 (IL-2). Genetically modified NK-92MI cells, which can release IL-2 to sustain their viability, have been identified as a promising alternative. This adaptation addresses the negative consequences of systemic IL-2 administration. The role of PSD-95/discs large/ZO-1 (PDZ)-binding kinase (PBK) in cancer development is recognized, but its effects on immunity are not fully understood. This study explores how PBK expression influences the ability of NK-92MI cells to infiltrate ovarian tumours. Elevated levels of PBK expression have been found in various cancers, including ovarian cancer (OV), with analyses showing higher PBK mRNA levels in tumour tissues compared to normal ones. Immunohistochemistry has confirmed increased PBK expression in OV tissues. Investigations into PBK's role in immune regulation reveal its association with immune cell infiltration, indicating a potentially compromised immune environment in OV with high PBK expression. The small-molecule inhibitor HI-TOPK-032, which inhibits PBK, enhances the cytotoxicity of NK-92MI cells toward OV cells. It increases the production of interferon-γ and tumour necrosis factor-α, reduces apoptosis and encourages cell proliferation. Mechanistic studies showed that contact with OV cells treated with HI-TOPK-032 upregulates CD107a on NK-92 cells. In vivo studies demonstrated that HI-TOPK-032 improves the antitumour effects of NK-92MI cells in OVCAR3^Luc xenografts, extending survival without significant side effects. Safety assessments in mice confirm HI-TOPK-032's favourable safety profile, highlighting its potential as a viable antitumour therapy. These results suggest that combining NK-92MI cells with HI-TOPK-032 enhances antitumour effectiveness against OV, indicating a promising, safe and effective treatment strategy that warrants further clinical investigation.