Ubiquitin-specific protease 1 facilitates tumor immune escape from natural killer cells and predicts the prognosis in small cell lung cancer.

Objective: Small cell lung cancer (SCLC) is commonly recognized as the most fatal lung cancer type. Despite substantial advances in immune checkpoint blockade therapies for treating solid cancers, their benefits are limited to a minority of patients with SCLC. In the present study, novel indicators for predicting the outcomes and molecular targets for SCLC treatment were elucidated.

Methods: We conducted bioinformatics analysis to identify the key genes associated with tumor-infiltrating lymphocytes in SCLC. The functional role of the key gene identified in SCLC was determined both in vitro and in vivo.

Results: A significant correlation was observed between patient survival and CD56dim natural killer (NK) cell proportion. Furthermore, we noted that the hub gene ubiquitin-specific protease 1 (USP1) is closely correlated with both CD56dim NK cells and overall survival in SCLC. Bioinformatics analysis revealed that USP1 is upregulated in SCLC. In addition, gene set enrichment analysis revealed that USP1 overexpression hinders NK cell-mediated immune responses. By co-cultivating NK-92 cells with SCLC cells, we demonstrated that NK cell cytotoxicity against SCLC could be improved either via USP1 knock-down or pharmacological inhibition. Furthermore, using a nude-mice xenograft tumor model, we noted that USP1 inhibition effectively suppressed tumor proliferation and increased the expression of NK cell-associated markers.

Conclusions: Our study findings highlight the importance of NK cells in regulating SCLC. USP1 overexpression can inhibit NK cell-mediated immunity; therefore, USP1 may serve not only as a prognostic biomarker but also as a potential molecular target of SCLC therapy.