Identification of two novel cellular genes associated with multistage carcinogenesis of human endocervical cells by mRNA differential display

Carcinogenesis originating from cervical cells has been recognized as a multistage process in which human papillomavirus (HPV) infection and cofactors, such as cigarette smoke, are frequently involved in the development of malignant cancer, However, the molecular mechanism underlying this process remains poorly understood, To identify the cellular genes involved in multistage cervical oncogenesis, we used the mRNA differential display method to analyze primary human endocervical cells (HEN), HPV 16-immortalized cells (HEN-16) and cigarette smoke condensate (CSC)-transformed cells (HEN-16T), Two cDNAs-PA4 and PA9-have been identified and isolated after comparing 8000 cDNAs from HEN, HEN-16 and HEN-16T. Northern blot analysis showed that PA4 was expressed 2- to 3-fold higher in HEN-16 and HEN-16T than in HEN, whereas PA9 was expressed uniquely in HEN, Moreover, the same patterns of PA4 and PA9 expression were found for a second line of HPV 16-immortalized endocervical cells and the corresponding transformed cells, An analysis of cDNA sequences showed that PA4 and PA9 had no homology to nucleotide sequences in Genbank, We suggest that immortalization, but not tumorigenesis, upregulated a new oncogene, PA4, and down-regulated a new tumor suppressor gene, PA9, These results demonstrated the utility of the human endocervical cell model system and the mRNA differential display method for identifying the genes that may be involved in multistage cervical carcinogenesis.