Background: To date, the impact and potential molecular mechanisms of CLDN12 and its association with malignancy in osteosarcoma have not been determined.
Materials and methods: In the present study, the expression profiles of CLDN12 in osteosarcoma cell lines and tissues were explored by immunohistochemistry. A fetal osteoblast cell line was transfected with a eukaryotic expression plasmid, and endogenous CLDN12 in osteosarcoma cells were silenced through an RNA interference (RNAi) method. These transfections were verified, and the activation state of Thr308 site in protein kinase B (Akt) was explored by Western blotting. Moreover, the malignant phenotype of osteosarcoma cells was evaluated by cell counting kit-8 (CCK-8), colony formation, Transwell, and wound-healing assays. Furthermore, osteoblast cells were treated with the phosphatidylinositol-3-kinase (PI3K) inhibitor LY294002 to determine the impact of the PI3K/Akt signaling pathway on cell migration ability.
Results: The results revealed that CLDN12 was overexpressed and localized in the cytoplasm of osteosarcoma cells, and its overexpression was associated with an unfavorable prognosis, irrespective of tumor node metastasis stage. In addition, the knockdown of CLDN12 in cultured osteosarcoma cells markedly attenuated cell proliferation and migration, as indicated by the Cell Counting Kit-8 assay, colony formation assay, scratch wound healing assay and Transwell migration assay. The results also demonstrated that the overexpression of CLDN12 increased the activation of Thr308 site in Akt in fetal osteoblast cells, and the PI3K inhibitor LY294002 partially decreased CLDN12-promoted proliferation and metastasis.
Conclusion: In conclusion, the results of the present study indicated that CLDN12 promoted cell proliferation and migration through the PI3K/Akt signaling pathway in osteosarcoma cells, suggesting that CLDN12 may be a potential agent in the treatment of patients with osteosarcoma.
Keywords: tight junction, claudin-12, osteosarcoma, metastasis, protein kinase B