PLEK2 promotes gallbladder cancer invasion and metastasis through EGFR/CCL2 pathway

Gallbladder cancer (GBC) is an extremely malignant tumor with a high mortality rate. Little is known about its invasion and metastasis mechanism so far.

To identify the driver genes in GBC metastasis, we performed a mRNA microarray of metastatic GBC and paired non-tumor samples, and found PLEK2 was markedly upregulated in GBC tissues. Next, the expression of PLEK2 in GBC were examined in a larger cohort of patients by qRT-PCR, western blot and IHC staining. The clinicopathologic correlation of PLEK2 was determined by statistical analyses. The biological involvement of PLEK2 in GBC metastasis and the underlying mechanisms were investigated.

In this study, we found that PLEK2 had higher expression in GBC tumor tissues compared to non-cancerous adjacent tissues and cholecystolithiasis tissues. The clinicopathologic analyses showed PLEK2 expression was positively correlated with tumor TNM stage, distant metastasis and PLEK2 was an independent predictor of overall survival (OS) in GBC patients. The cellular function assays showed PLEK2 promoted GBC cells migration, invasion and liver metastasis in mouse model via the regulation of epithelial-mesenchymal transition (EMT) process. Our mass spectrum and co-immunoprecipitation (co-IP) assays demonstrated that PLEK2 could interact with the kinase domain of EGFR and suppress EGFR ubiquitination mediated by c-CBL, leading to constitutive activation of EGFR signaling. Furthermore, RNA-sequencing and qRT-PCR results demonstrated chemokine (C-C motif) ligand 2 (CCL2), a target gene downstream of PLEK2/EGFR signaling, mediated the motility-promoting function of PLEK2.

On the basis of these collective data, we propose that PLEK2 promotes the invasion and metastasis of GBC by EGFR/CCL2 pathway and PLEK2 can serve as a potential therapeutic target for GBC treatment.