Down modulation of IL‐18 expression by human papillomavirus type 16 E6 oncogene via binding to IL‐18

Abstract

To understand modulation of a novel immune-related cytokine, interleukin-18, by human papillomavirus type (HPV) 16 oncogenes, HaCaT, normal keratinocyte cell line, and C-33A, HPV-negative cervical cancer cell line, were prepared to establish stable cell lines expressing E6, E6 mutant (E6m), E6E7, or E7 constitutively. Expressions of various HPV oncogene transcripts were identified by RT-PCR. Expression of HPV oncogene E6 was reversely correlated to the expression of interleukin-18, a novel pro-inflammatory cytokine. The expression of E6 in C-33A, independent of E6 splicing, resulted in decreased IL-18 expression and that of IL-18 was also significantly reduced in HaCaT cells expressing E6. The level of p53 was reduced in C-33A cells expressing E6 whereas not altered in HaCaT cells expressing E6, suggesting that E6 downregulated IL-18 expression via an independent pathway of p53 degradation in HaCaT cells which have a mutated p53 form. However, E7 did not affect IL-18 expression significantly in both C-33A and HaCaT cells. Cotransfection experiments showed that E6 oncogene did not inhibit the activities of IL-18 promoter P1 and P2, suggesting that E6 oncogene indirectly inhibited IL-18 expression. Taken together, E6, E6m and E6/E7 inhibited IL-18 expression with some variation, assuming that cells expressing E6 oncogene can evade immune surveillance by downregulating the expression of immune stimulating cytokine gene, IL-18, and inhibiting the cascade of downstream effects that follow activation of the IL-18 receptor. ß

Advances in Peptide-based Human Papillomavirus Therapeutic Vaccines

“…An E6 oncoprotein-mediated reduction in expressed interleukin-8 (IL-18) CD8 + was also observed [60].…”

“…The lipid core peptide (LCP), a vaccine delivery system incorporating lipoamino acids, was used to produce vaccine candidates against HPV-16 [104]. Moyle et al demonstrated that an LCP system that incorporated the long sequence E7 [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] (known as 8Q) with CTL, T helper cell, and B cell epitopes was self-adjuvanting and reduced tumor size. This epitope was unable to prevent TC-1 tumors when delivered alone [104].…”

“…The self-adjuvanting properties of LCP are predominantly derived from its propensity to target vaccines to DCs and induce DC maturation [22,112]. In another mouse study, a lipopeptide vaccine incorporated the E6 [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] and E7 [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] epitopes conjugated to a dipalmitoyl-lysine-glycineglycine (Pam 2 KGG) moiety. It was shown that although both epitopes were individually able to elicit specific CTL responses in mice, the lipid-tailed (Pam 2 KGG) diepitopic construct was more efficient than the monomeric forms [113].…”

“…Another animal study, which used a long peptide (E7 [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] ) and the DC-activating adjuvant ODN-CpG, has identified that vaccination with a longer peptide containing CTL and Th cell epitopes, and ODN-CpG represents a promising strategy against MHC-I deficient tumors. This study also investigated the efficacy of cellular vaccines based on ex vivo cultured DCs pulsed with either minimal CTL (E7 [49][50][51][52][53][54][55][56][57] ) epitope or longer CTL (E7 [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] ) epitopes, and then matured with ODNCpG. The use of ex vivo cultured DCs is particularly suitable f...…”

“…Intratumoral administration with E7 peptide in combination with PADRE and poly(I:C) generated better CD8 + T cell immune responses when compared with subcutaneous vaccination [123]. Combining a long CTL (E [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] ) epitope with poly(I:C) and the vascular disrupting agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA), has also been shown to enhance the E7 specific CD8 + T cell immune responses. Interestingly, the timing/treatment regimen of DMXAA administration played an important role in vaccine efficacy [124].…”