RAB20 Promotes Proliferation via G2/M Phase through the Chk1/cdc25c/cdc2-cyclinB1 Pathway in Penile Squamous Cell Carcinoma

SIMPLE SUMMARY: There is no available biomarker that could be used to predict the prognosis or progression of penile squamous cell carcinoma (PSCC) currently. Here, we conducted comprehensive genomic sequencing on eight pairs of PSCC tissues and found that RAB20 was upregulated in tumors, especially in metastatic lymph nodes. We then detected the expression of RAB20 in a large cohort of 259 PSCC cases using IHC assay and analyzed the association between the RAB20 expression and clinical features. We found that high RAB20 expression predicted poor prognosis and advanced clinicopathological features. Further in vitro and in vivo tumorigenesis assays revealed that RAB20 regulates cell proliferation at the G2/M cell cycle phase through the Chk1/cdc25c/cdc2-cyclinB1 pathway. Our results indicated that RAB20 could be a promising prognostic biomarker of advanced PSCC with poor survival and could be a potential therapeutic target. ABSTRACT: RAB20, a member of the RAS GTPase oncogene family, is overexpressed in several cancers with poor outcomes, promoting tumorigenesis and inducing genomic instability. Here, we performed comprehensive genomic sequencing on eight penile squamous cell carcinoma (PSCC) and normal tissue pairs and found that RAB20 was upregulated in tumors, especially in metastatic lymph nodes. RAB20 overexpression in tumors was further verified by qPCR, Western blotting, and immunohistochemistry of our newly established PSCC cell lines and paired tissues. The clinical significance of RAB20 was validated in 259 PSCC patients, the largest cohort to date, and high RAB20 expression positively correlated with the T, N, M status, extranodal extension, and clinical stage (all p < 0.01). RAB20 was an unfavorable independent prognostic indicator in the survival analysis (p = 0.011, HR = 2.090; 95% Cl: 1.183–4.692), and PSCC patients with high RAB20 expression experienced shorter 5-year cancer-specific survival times (p < 0.001). Furthermore, tumorigenesis assays demonstrated that RAB20 knockdown inhibited cell proliferation, migration, and colony formation in vitro and tumor growth in vivo. RAB20 depletion also induced PSCC cell cycle arrest at G2/M by increasing Chk1 expression and promoting cdc25c phosphorylation to reduce cdc2-cyclinB1 complex formation. Our study revealed an oncogenic role for RAB20 in promoting PSCC cell proliferation at the G2/M phase via the Chk1/cdc25c/cdc2-cyclinB1 pathway. Thus, RAB20 could be a promising prognostic biomarker of advanced PSCC with poor patient survival outcomes and could be a potential therapeutic target.