Zinc-alpha-2-glycoprotein overexpression and maintaining anti-apoptotic function in oral squamous cell carcinoma

Overexpression of zinc-alpha-2-glycoprotein (ZAG) can be induced by various factors and has potential to be a biomarker in certain malignancies. However, in oral squamous cell carcinoma (OSCC), the risks and effects associated with ZAG overexpression are still poorly known. Here, we investigated the effect of HPV16 oncogenes and arecoline on the expression levels of ZAG and the possible effects of ZAG in OSCC cell lines.

The level of ZAG expression was determined in protein extracted from exfoliated buccal cells from cancer-free control individuals and oral lesion cells from OSCC. Oral cell lines expressing HPV16E6/E7, and treated with arecoline were prepared to investigate ZAG expression. The effects of ZAG on cell biological activity and its targeting of UCP1 were determined in ZAG-overexpressing and ZAG-knockdown cells.

The expression of ZAG protein was significantly increased in oral lesion cells from OSCC relative to controls. Notably, the expression level of ZAG in OSCC positive for HPV, betel-quid chewing, and combination of both factors, was slightly higher than in cancer-free controls. ZAG expression was upregulated in oral cells treated with HPV16 oncoproteins E6 and/or E7, and treatment with arecoline (25 μg/ml). Interestingly, ZAG overexpression significantly increased UCP1 and decreased apoptosis, whereas decreased UCP1 and increased apoptosis were found in ZAG-knockdown cells. The mRNA expression levels of TP53, STAT3, BCL2, and NFKB1 corresponded to observed anti-apoptosis function.

HPV oncoproteins and high doses of arecoline are risk factors for an overexpressed ZAG protein that has an anti-apoptotic function in OSCC.