Membrane palmitoylated protein MPP1 inhibits immune escape by regulating the USP12/ CCL5 axis in urothelial carcinoma.

BACKGROUND

The response rate to immunotherapy in patients with urothelial carcinoma remains limited. Studies have shown that membrane palmitoylated proteins (MPPs) play key roles in tumor progression. However, the mechanisms by which MPP1 regulates immune escape in urothelial carcinoma are not well understood.

METHODS

The TCGA and BEST databases were used to analyze the associations between the expression of members of the MPP family and the prognosis or immunotherapy sensitivity of urothelial carcinoma patients. MPP1 was identified due to its significant association with survival and immunotherapy sensitivity. MPP1 expression in urothelial carcinoma tissues and cell lines was examined. An MPP1 overexpression vector was used to transfect urothelial carcinoma cells. The functional assays included proliferation, migration, urothelial carcinoma cell-CD8+ T-cell coculture, CD8+ T-cell chemotaxis, and tumorigenesis in human immune reconstitution NOG mice (HuNOG). Bioinformatics, coimmunoprecipitation (CO-IP), mass spectrometry, quantitative real-time polymerase chain reaction (RT-qPCR), and western blotting were used to validate the activity of the MPP1/USP12/CCL5 cascade.

RESULTS

Analysis of the BEST data revealed that, compared with other MPP family genes, MPP1 was more strongly associated with urothelial carcinoma prognosis and immunotherapy response. Low MPP1 expression was observed in urothelial carcinoma patients and was positively associated with better survival. MPP1 inhibited the proliferation and migration of urothelial carcinoma cells. Bioinformatics, in vitro coculture assays, and in vivo tumorigenesis experiments demonstrated that MPP1 promotes CCL5 production and CD8+ T-cell chemotaxis in the urothelial carcinoma tumor microenvironment (TME). Mechanistically, bioinformatics, mass spectrometry, co-IP, RT-qPCR, and western blot analyses indicated that MPP1 increases CCL5 expression by binding to and promoting USP12.

CONCLUSIONS

MPP1 significantly inhibits urothelial carcinoma cell proliferation and immune escape via the MPP1/USP12/CCL5 cascade. MPP1 has the potential to serve as a biomarker for guiding immunotherapy in patients with urothelial carcinoma.