Rapidly accumulating evidence indicates that the insulin-like growth factor-1 receptor (IGF-1R) can play a major role in transformation and tumorigenesis. We have demonstrated that epithelial cervical cancer cells consistently overexpress the type I insulin-like growth factor receptor (IGF-1R) compared to normal cervical epithelial cells and that cervical cancer cells characteristically express mRNA for IGF-2. Results also indicate that stimulation with epidermal growth factor induces the autocrine production of IGF-2 by cervical cancer cells which, in turn, activates the IGF-1R. Using embryonic fibroblasts from normal and IGF-1R knock-out mice, it has been shown that the Simian virus 40 (SV-40) large tumor antigen (T-Ag) requires a functional IGF-1R gene for transformation. Because HPV-16 E6 and E7 share certain properties with T-Ag, such as inactivation of the tumor suppressors p53 and pRB, respectively, we investigated if a functional IGF-1R is also a prerequisite for the transforming effects of HPV E6 and E7. We have found that, in contrast to T-Ag, HPV E6 and E7 together can transform murine fibroblasts in the absence of a functional IGF-1R gene while E6 or E7 alone cannot. These experiments suggest that IGF-1R and E6 are functionally equivalent in assisting E7 in transformation and may each participate in survival pathways which protect from apoptosis. Furthermore, our data indicates that E6 appears to suppress apoptotic responses by a p53 independent mechanism. The goal of these investigations is to define the molecular mechanisms involved in HPV-induced malignant transformation in order to develop new methods to prevent, more effectively treat, or more accurately predict the clinical course of cervical cancer. Other investigations have focused on the development of a vaccine for cervical cancer. Over 90% of invasive cervical tumors harbor HPV DNA, and genotype 16 can be detected in approximately 50% of squamous cell carcinomas of the cervix. Recent research has shown that the E6 and E7 genes of HPV-16 encode for oncoproteins which can immortalize human keratinocytes. Because oncoproteins E6 and E7 are selectively retained and expressed in cervical tumors associated with HPV-16, they are attractive targets for novel immunotherapies. Presentation to T cells of endogenously synthesized viral antigens involves degradation of the viral protein into small epitope peptides that are transported via the endoplasmic reticulum to the cell surface in association with class I MHC molecules. Cytolytic T-cells (CTL) recognize antigens by the binding of their clonotypic T cell receptors to the processed endogenous peptides associated with class I molecules. Major histocompatibility (MHC) class I restricted CTL epitope peptides of HPV-16 E6 and E7 have been identified for both human and mouse model systems. Using leukapheresis specimens from patients with cervical cancer, we have assessed the vaccine potential of peptide epitopes of E7. The peptides have been used to stimulate patients' cytotoxic T-lymphocytes to recognize and kill cervical cancer cells infected with the virus. This study forms part of the scientific basis for a clinical protocol to test the effects of a lipidated E7 peptide to treat patients with advanced cervical cancer.
