Prognostic and Immunological Significance of Rhomboid Domain Containing Protein 1 in Multiple Primary Cancers

Background: RHBDD1 is an intramembrane serine protease of the rhomboid superfamily that regulates diverse physiological and pathological processes. However, the relationship between RHBDD1 expression, tumor-infiltrating immune cells (TIICs), and cancer prognosis remains unclear. Objective: We comprehensively analyzed the prognostic and immunological significance of RHBDD1 in multiple primary cancers. Methods: RHBDD1 expression was investigated using Oncomine, TIMER, and UALCAN databases, after which the clinical prognostic value of RHBDD1 was assessed with online public databases. In addition, we explored the correlation between RHBDD1 and TIICs by TIMER and GEPIA and investigated the relationship between RHBDD1 expression and chemokines in cancers by TIMER. Results: In general, compared to that in adjacent normal tissue, lower expression of RHBDD1 was found in various cancers and was correlated to pathological stages. Although RHBDD1 showed a protective effect on multiple solid tumors, a high expression level of RHBDD1 was detrimental to the survival of stomach adenocarcinoma patients. RHBDD1 was positively correlated to immune infiltration levels in various cancers, including lung, breast, ovarian, and gastric cancer. Furthermore, gene markers of TIICs, such as tumor-associated macrophages (TAMs), dendritic cells (DCs), and regulatory T cells, were also correlated to RHBDD1 expression. In addition, the RHBDD1 expression level was positively correlated to multiple chemokines in cancers, which could recruit diverse immune cells at the tumor site. Conclusions: RHBDD1, which correlates with immune infiltration, can be used as a potential prognostic biomarker in multiple primary cancers. Specifically, RHBDD1 expression potentially contributes to the recruitment of TAMs and DCs and the regulation of T cell functions in cancers.