Effects of human papillomavirus type 16 oncoproteins on survivin gene expression

Role of HPV E6 proteins in preventing UVB-induced release of pro-apoptotic factors from the mitochondria

Apoptotic elimination of UV-damaged cells from the epidermis is an important step in preventing both the emergence and expansion of cells with carcinogenic potential. A pivotal event in apoptosis is the release of apoptogenic factors from the mitochondria, although the mechanisms by which the different proteins are released are not fully understood. Here we demonstrate that UV radiation induced the mitochondrial to nuclear translocation of apoptosis inducing factor (AIF) in normal skin. The human papillomavirus (HPV) E6 protein prevented release of AIF and other apoptotic factors such as cytochrome c and Omi from mitochondria of UV-damaged primary epidermal keratinocytes and preserved mitochondrial integrity. shRNA silencing of Bak, a target for E6-mediated proteolysis, demonstrated the requirement of Bak for UV-induced AIF release and mitochondrial fragmentation. Furthermore, screening non-melanoma skin cancer biopsies revealed an inverse correlation between HPV status and AIF nuclear translocation. Our results indicate that the E6 activity towards Bak is a key factor that promotes survival of HPV-infected cells that facilitates tumor development.

Survivin promoter polymorphism and cervical carcinogenesis

BACKGROUND

Survivin, a novel member of the inhibitor of apoptosis family, plays an important role in cell cycle regulation. A common polymorphism at the survivin gene promoter (G/C at position 31) was shown to be correlated with survivin gene expression in cancer cell lines.

AIM

To investigate whether this polymorphism could be involved in the development of human papillomavirus (HPV)-associated cervical carcinoma.

METHODS

Survivin promoter polymorphism was detected in patients with cervical cancer, in patients with equivocal cytological atypia and in a control population using polymerase chain reaction (PCR-restriction fragment length polymorphism (RFLP) and PCR-single strand conformation polymorphism analysis. HPV was typed in patients with cervical cancer and cytological atypia using PCR-RFLP.

RESULTS

No statistically significant differences were found in the genotype distributions of the survivin promoter variants among our study groups.

CONCLUSIONS

The survivin promoter polymorphism at position 31 may not represent an increased risk for the development of cervical cancer, at least in the population studied here.