HPV16 E7 Nucleotide Variants Found in Cancer-Free Subjects Affect E7 Protein Expression and Transformation

The human papillomavirus (HPV) type 16 E7 oncogene is critical to carcinogenesis and highly conserved. Previous studies identified a preponderance of non-synonymous E7 variants amongst HPV16-positive cancer-free controls compared to those with cervical cancer. To investigate the function of E7 variants, we constructed full-length HPV16 E7 genes and tested variants at positions H9R, D21N, N29S, E33K, T56I, D62N, S63F, S63P, T64M, E80K, D81N, P92L, and P92S (found only in controls); D14E, N29H (CIN2), and P6L, H51N, R77S (CIN3). We determined the steady-state level of cytoplasmic and nuclear HPV16 E7 protein. All variants from the controls showed a reduced level of steady-state E7 protein, with 7/13 variants having deficient protein levels. In contrast, 2/3 variants from the CIN3 precancer group had near-normal E7 levels. We assayed the activity of representative variants in stably transfected NIH3T3 cells. The H9R, E33K, P92L, and P92S variants found in control subjects had lower transforming activity than D14E and N29H variants (CIN2); and the R77S (CIN3) had activity only slightly reduced from wildtype E7. In addition, R77S and WT E7 caused increased migration of NIH3T3 cells in a wound-healing assay as compared with H9R, E33K, P92L, and P92S (controls) and D14E (CIN2). These data provide evidence that the E7 variants found in HPV16-positive cancer-free women are partially defective for transformation and cell migration further demonstrating the importance of fully active E7 in clinical cancer development.

Detection of human papillomavirus type 16 oncogen E7 in surgical materials from Russian prostate cancer patients

Introduction. High indices of prostate cancer (PC) incidence and mortality as well as high speed of growth of these figures testify to urgency of research into PC origin as well as means of its prophylaxis. The problem of possible PC association with oncogenic human papillomaviruses (HPV) is still being disputable. Objective: to test whether surgical materials from PC patients in Russia harbour E7 oncogene of HPV type 16 (HPV16), the main HPV type responsible for cervical cancer. Materials and methods. Prostate tissues excised in the course of radical prostatectomy from 17 PC patients were tested by polymerase chain reaction. For better DNA preservation cryopreserved tumor specimens not treated with either formalin or paraffin were used. The PC typical multifocal type of growth was taken into account by microdissecting of cryostate cuts to accumulate homogeneous cells (cancerous, dysplastic or normal). Results. HPV16 E7 was registered in prostate tissues of 7 patients out of 17 examined including all those 5 cases for which DNA had been isolated from homogeneous sites of cancer cells. Conclusion. The result obtained enables one to admit that HPV16 may be harbored in prostates of Russian PC patients not infrequently.