IDDF2020-ABS-0119 Dissecting the molecular mechanism and clinical significance for regulating the malignant progression of gastric cancer by HIPK3

Background Gastric cancer (GC) is one of the most threatening malignant diseases in east Asia with largely unknown mechanisms. Protein kinases and their signaling pathways were closely related to cancer occurrence and progression. We decide to investigate the role of related protein kinases and their signaling pathways in GC. Methods We analyze the protein kinases activity using the phosphorylated proteomic data of gastric cancer and find that the substrates of HIPK family with abnormal phosphorylated levels. HIPK3 with less known function and mechanisms is chosen for further research, and its low expression in GC is confirmed by qPCR and immunohistochemistry analysis in a large GC patient cohort. MTS assay, colony formation assay, transwell migration and invasion assays are performed after ectopic express or knockdown of HIPK3 in vitro. Additionally, subcutaneous xenograft and in situ xenograft models are built in vivo. We detect the HIPK3 mRNA and protein level in cisplatin-resistant GC cells by qPCR and western blotting and measure the tolerance of cisplatin after overexpression of HIPK3. Coimmunopreicipitation and mass spectrometry analysis identify the interaction between HIPK3 and MAP7. Immunofluorescence confirms their co-localization. Downstream mechanisms were examined by regular molecular biological methods. Results We discovered the aberrant phosphorylation of substrates for HIPK family kinases based on the profiled gastric cancer phosphoproteome data and bioinformatical pipeline for kinase activity analysis. Then the low expression of HIPK3 in the gastric tumor was validated and correlated with patient overall survival. Cell line and mouse model experiments for gastric cancer showed that reducing the HIPK3 expression promoted the growth, proliferation, migration, invasion and metastasis, and high expression of HIPK3 could reverse the cisplatin resistance. Further molecular mechanism revealed that HIPK3 might regulate the progression of gastric cancer through phosphorylating MSH6 to regulate DNA mismatch repair and interaction with MAP7 to regulate cell morphology. Conclusions Our study explicit the potential of HIPK3 as a key regulator for progression, an effective biomarker for prognosis and drug resistance, and a potential therapy to target gastric cancer.