Expression of lymphomagenic oncogenes in T-cell lymphomas of HPV 16 transgenic mice

We have previously established that a dimer repeat of the complete HPV 16 genome is sufficient to cause multiple organ malignancies, either carcinomas or T-cell lymphomas, in transgenic mice. Here, we report the expression of oncogenes supporting the notion that these tumors arose via multiple oncogenic pathways. In these mice, the transgenic HPV 16 genome cosegregated with the tumor phenotype. E6/E7 expression was observed in both carcinomas and T-cell lymphomas, while E2 expression was observed only in T-cell lymphomas. Some of the T-cell lymphomas revealed E2 expression alone, implying that oncogenic pathways of HPV other than the one involving E6/E7 existed in these transgenic mice. To establish that this is the case, expression of genes downstream from E6/E7 and oncogenes involved in T-cell lymphoma formation were analyzed. p53 mutations were observed in two of five tumors that lacked E6 expression. High levels of c-myc gene expression were observed in five of six tumors with E7 expression, suggesting that a pathway involving E7, inactivation of Rb, and activation of c-myc is important in tumorigenesis of HPV 16 in these transgenic animals. High levels of expression of the c-Pim gene were also noted in two of three c-myc-expressing T-cell lymphomas, suggesting cooperation between these two proto-oncogenes. Activation of Hox-11, Tal2/SCL-2, and Rbtn1/Ttg1 expression, which are highly associated with human T-cell acute lymphoblastic leukemia (T-ALL), was observed in three of three T-cell lymphomas with E2 expression but not E6/E7 expression, showing that pathways to tumor formation not involving E6/E7 exist in these transgenic animals. At least two oncogenic pathways to tumors in HPV 16 transgenic mice exist, one involving E6/E7 and c-myc and the other involving E2 and lymphomagenic oncogenes.