Abstract
Cervical cancer in females is a worldwide health issue. High risk subtype of human papilloma viruses (HPV) are involved as a major risk factor. HPV oncogenes, E7 and E6 which are over-expressed in the host cells and promote malignant transformation. There is also evidence of HPVE7 involvement in immune modulation. Microparticles (MP), a type of small membrane fragments (0.1um ~1um) released by activated cells, have been implicated in suppressing immunity following interaction with antigen presenting cells. Our laboratory has previously reported up-regulation of microparticle secretion by HPV16E7 expressing keratinocytes. A component of this study is to advancing the understanding of the effect of keratinocyte microparticle on the phenotype of langerhans cells. Increasingly, roles for p53 in regulation of the immune response is being recognized. In this project, the effect of p53 status in langerhans cells on maintianing the immune phenotype will also be tested.
The HPV16E7 oncoprotein expressing mouse keratinocyte (E7-PDV) cell line was established following lentiviral transduction, for microparticle (MP) production. Wild-type (p53+) Langerhans cell-like cells (LCLC) and p53 deficient (p53-) LCLC, which were generated from murine bone marrow cells resembling the phenotype of epidermal LC, were used in this study. The effect of MP on LCLC phenotype (CD40, CD86, E-cadherin and cytokine production) was investigated following 48 h co-culture.
Compared to the control PDV cell lines, HPV16E7 expressing PDV were found to produce more MP, suggesting a poteintial role for oncoprotein HPV16E7 in inducing MP production. In response to lipopolysacharride stimulation, the up-regulation of inflammatory surface marker CD40 on p53- LCLC was abrogated compared to wild-type LCLC and E-cadherin expression was also found to be low compare to that of wild-type LCLC. This suggests, to some extend, a potential role for p53 protein in maintaining the proper immune phenotype of normal LCLCs. Moreover, comparing to control groups, the same amount of MP from E7-PDV found to have an inhibitory effect on CD40 expression and it also reduced inflammatory cytokine interleukin 12 productions in LPS-stimulated LCLC. The altered LCLC phenotypes subject to MP treatment had confirmed the hypothesis that HPV16E7 induced MP had a modulating effect on the phenotype of LCLC. Finally, the combined down-regulating effect on CD40 expression was observed when MP treatment was applied to p53- LCLC suggested that the MP effect on CD40 expression was p53 independent. The findings of phenotypic alteration of LCLC subject to MP treatment has unveiled the potential role of HPV-induced MP in immune supression that might provide a mechanism to contribute HPV persistence in the skin.