Multiple Omics Analysis of the Rac3 Roles in Different Types of Human Cancer

Rac Family Small GTPase 3 (Rac3) is a member of the Rho family of small GTP-binding proteins which play critical roles in the occurrence, progression, and metastasis of various tumors. Nevertheless, previous studies have focused on a single type of human cancer, so that the roles of Rac3 in different cancer types have not been sufficiently clarified. With the progress of biological detection and bioinformatics technology, the emerging cancer genomics databases make it possible to perform a pan-cancer analysis. Therefore, for the first time, we performed multiple omics analysis to investigate the roles of Rac3 in differential expression, survival prognosis, mutative status, DNA methylation, functions, immune infiltration, and immunotherapy across 33 human cancer types. We found that Rac3 expression was abnormal in 17 cancer types and significantly different in both molecular and immune subtypes of 10 cancers (p<0.05). These Rac3 expression dysregulations in cancer tissues significantly affected their corresponding survival prognosis. Our results also indicated that genetic alterations of Rac3 occurred in 27 cancer types and were significantly associated with prognosis. Moreover, methylation of Rac3 was associated with dysfunctional T-cell phenotypes and affected the prognosis of the brain, melanoma, and breast tumors, and Rac3 Copy Number Alterations (CNA) might affect the infiltration levels of different immune cells in nine cancers. Rac3 and Rac3-related genes were enriched in the axon guidance, actin cytoskeleton regulation, and neurotrophin signaling pathway, and involved the regulation of cellular localization and actin cytoskeleton organization, and small GTPase mediated signal transduction. Then, we further explored the correlations between Rac3 expression and 25 immune cells and cancer-associated fibroblasts across 33 human cancers. Furthermore, we found that Rac3 achieved higher predictive power (AUC>0.5) than three standardized biomarkers of tumor immune responses and was associated with cytotoxic T-cell levels (CTLs) and the risk of immunotherapeutic responses in three cancer types. Collectively, our study contributes to a comprehensive and integrative understanding of the oncogenic roles of Rac3 across human cancers and offers a new clue for treatment strategies.