Protocadherin-8 promotes invasion and metastasis via laminin subunit γ2 in gastric cancer.

Growing evidence suggests that protocadherins (PCDH) play crucial roles in pathogenesis and progression of cancers, including gastric cancer (GC). Protocadherin-8 (PCDH8) was previously reported to be involved in metastasis of GC, but functional studies yielded inconsistent results and the molecular mechanism remained unknown. The present study aimed to explore the clinical relevance, function and molecular mechanism of PCDH8 in GC. Data from the GEPIA and Kaplan-Meier plotter databases showed that high expression of PCDH8 was significantly correlated with poorer prognosis in GC. Ectopic expression of PCDH8 in GC cells promoted invasion and migration in vitro and metastasis in vivo, and knockdown of PCDH8 inhibited invasion and migration in vitro. RNA sequencing followed by gene set enrichment analysis found a remarkable enrichment in the extracellular matrix receptor interaction pathway, with the expression of laminin subunit γ2 (LAMC2) being significantly increased in the PCDH8-overexpressing group. High expression of LAMC2 was significantly correlated to poor prognosis in GC in GEPIA database. Upregulation of LAMC2 following PCDH8 overexpression was further confirmed by immunohistochemistry in liver metastatic lesions of nude mice. To our knowledge, this is the first report of the metastasis-enhancing property and molecular mechanism through upregulation of LAMC2 of PCDH8 in cancer. High expression of PCDH8 could be used as a biomarker for poor prognosis in clinical practice.