Targeting STK32C suppresses colon cancer progression with combinatorial potential with 5-fluoruracil via HSP90 and PI3K/AKT/mTOR signaling axis

Background: In this work, the oncogenic pathogenesis of STK32C was explored in colorectal cancer cells in association with HSP90 and PI3K/AKT/mTOR signaling. Methods: TCGA analysis, tissue microarray, next generation sequencing analysis, RNA interference, wound-healing, transwell, MTT, clonogenic, TUNEL and flow cytometry assays, RT-qPCR and Western blotting were employed in HCT116 and SW620 cells transfected with STK32C depletion or overexpression plasmid. Nude mouse tumor model was used to confirm in vitro data. Close interaction between STK32C and HSP90 was investigated by Homology analysis, Co-immunoprecipitation, Coomassie blue staining, GST pulldown assay and immunofluorescence. CompuSyn and SynergyFinder softwares were employed for synergy analysis with 5-Fu Results: STK32C was highly expressed in HCT116, HT29, SW480, and SW620 cells compared to CCD-18Co fibroblasts with poor prognosis. STK32C depletion exerted cytotoxic, anti-migratory, and anti-invasive effects, inhibited the expression of pro-PARP, pro-Caspase-3, PI3K, p-AKT, p-mTOR, HSP90, and Bcl-2 and increased Bax, sub-G1 population, Annexin V and TUNEL-positive cells in HCT116 and SW620 cells. Also, STK32C depletion enhanced the antitumor activity of 5-FU in HCT116 cells. STK32C binds directly to N-terminal domain of HSP90 by homology, colocalization and binding. Consistently, HSP90 N-terminal inhibitor Ganetespib reduced STK32C and p-AKT1, while the HSP90 C-terminal inhibitor EGCG or AKT inhibitor LY294002 did not affect STK32C. Furthermore, STK32C depletion reduced the growth of HCT116 cells in BALB/c mice with decreased expression of STK32C, HSP90, PCNA, and AKT and activation of caspase 3. Conclusions: Targeting STK32C inhibits colorectal cancer progression with combinatorial potential with 5FU via HSP90 and PI3K/AKT/mTOR signaling.