Expression Analysis of Several Lymphoma-specific Genes in Human Fibroblasts Immortalized with SV40

Abstract

Subtraction hybridization was earlier used to obtain cDNA clones corresponding to human genes upregulated in HIV-associated centroblast lymphoma (CL) as compared with HIV-associated immunoblast lymphoma (IL). With inverse subtraction hybridization, clones were isolated that correspond to genes upregulated in IL compared with CL. In addition to cDNAs characterized earlier, the resulting clones contained several (seven CL-specific and three IL-specific) sequences of unknown function. To identify the lymphoma-specific genes that are overexpressed in early carcinogenesis, Northern blotting was used to assess the level of gene transcription in two human fibroblast lines and in their derivatives immortalized with either a temperature-sensitive mutant of SV-40 or with pSV3neo carrying the SV-40 А gene, considering the latter as a model of early cell malignant transformation. Increased expression in at least one immortalized line compared with normal fibroblasts was observed for set, a-myb, ND1, ND2, ND4 (NADH dehydrogenase subunits 1, 2, and 4), COX2, COX3 (cytochrome c oxidase subunits 2 and 3), KIAA0129, and the gene corresponding to hss2-1-7-10 cDNA. High expression of these genes was assumed to be associated not only with lymphomogenesis, but also with early transformation (immortalization) of other, nonlymphoid cells. Expression of the calpain gene and the gene corresponding to hss2-2-9-5 cDNA proved to be lower in immortalized than in normal fibroblasts. This was indicative of an alternative mechanism of fibroblast transformation or of different processes regulating the expression of these genes in early and late carcinogenesis.