Degradation of p53 by HPV16-E6 variants isolated from cervical cancer specimens of Moroccan women.

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Cervical cancer is the second most diagnosed cancer in Moroccan women. The main etiological factor for developing cervical cancer is the persistent infection with HPV16. Genetic studies have reported the occurrence of amino acid variations within the E6 oncoprotein that promotes host cell transformation by targeting p53 for degradation. To verify the biological effects of E6 polymorphisms towards p53 degradation, HPV16-E6 prototype and 7 variants isolated from cervical cancer biopsies of Moroccan women were evaluated for their activities by transient expression assays using pcDNA3.1-E6 constructs in C33A cell line. Expression of E6 genes in transfected cells was detected with reverse transcription PCR (RT-PCR), then, p53 levels were evaluated by western blot analysis. Significant dissimilarities in p53 degradation activities of HPV16-E6 prototype and intratypic variants were noticed. As compared to the prototype, the highest p53 degradation were exhibited by the African variants Af2-a/r, Af1-d/G295 and Af2-a/G285 (p<0.001), followed by the European variants E- C442/G350 and E-G350/r (p<0.01), then, the North American variant NA1-b/r (p<0.05). The inter-variant differences were statistically significant between Af2-a/r variant and the North American variants NA1-b/r and NA1 (p<0.05). Thus, the Af2-a/r variant was significantly more active in degrading p53 in our in vitro experiments (p<0.0001). Our findings support the fact that HPV16-E6 variations have a biological impact on degrading p53, and so, represent a significant carcinogenic potential for developing cervical cancer.