Interleukin-1 regulates interleukin-6 secretion in human oral squamous cell carcinoma in vitro: possible influence of p53 but not human papillomavirus E6/E7.

ABSTRACT

We have previously shown that interleukin-1 (IL-1) and IL-6 are constitutively produced by human oral squamous cell carcinoma (SCC) and some derived cell lines but not by cultured normal oral keratinocytes. To elucidate possible cytokine regulatory pathways that may contribute to oral SCC growth and/or progression, we tested the hypotheses that exogenous and/or endogenous IL-1 regulates IL-6 production in vitro. We investigated the effects of exogenous IL-1 and IL-6 on secondary cytokine secretion. Our studies revealed that IL-1 strongly up-regulated IL-6 protein secretion in all three cell lines tested. This effect was completely abrogated by IL-1 receptor antagonist. IL-1 receptor antagonist also inhibited the secretion of IL-1alpha and IL-1beta in two of three cell lines. These data show for the first time that IL-1 strongly up-regulates IL-6 and support the notion of autocrine regulation of IL-1 in certain oral SCC cell lines. Additionally, because human papillomavirus (HPV) infection and p53 mutation have been implicated in the malignant transformation of SCC, we explored a second hypothesis, that HPV and/or p53 mutation contribute to cytokine dis-regulation. We investigated HPV DNA presence, transcriptional activation of HPV E6/E7 (in HPV DNA-positive cell lines), and p53 gene status in our cell lines. No association between HPV DNA and cytokine expression was found. However, the oral SCC cell lines secreting the most IL-6 had mutant rather than wild-type p53.