Differential gene expression was studied to understand the potential molecular mechanism responsible for cell transformation and tumorigenesis induced by beryllium. Cell lines were derived from tumors developed in nude mice injected subcutaneously with BALB/c-3T3 cells morphologically transformed with beryllium sulfate. Using the atlas mouse 1.2 cDNA expression, microarray, the expression profiles of 1176 genes, belonging to several different functional categories, were studied in the tumor cells as well as in the nontransformed control cells. Expression of 18 genes belonging to two functional groups was found to be consistently and reproducibly different (at least twofold) in the tumor cells compared with the control cells. The functional groups and the differentially expressed genes are as follows: The cancer-related genes (nine genes) were the ets-related transcription factor activated by ras, colony-stimulating factor, A-myb, sky, cot1, c-fos, c-jun, c-myc, and R-ras proto-oncogenes. The DNA synthesis, repair, and recombination genes (nine genes) were teh DNA replication licensing factor MCM4, the DNA replication licensing factor MCM5, the DNA mismatch repair gene PMS2, the DNA excision repair gene, the DNA mismatch repair gene MSH2, the ultraviolet excision repair gene Rad23, DNA ligase 1, Rad51, and Rad52. The differential gene expression profile was confirmed with reverse transcription-polymerase chain reaction using primers specific for the differentially expressed genes. In general, expression of the cancer-related genes was upregulated, while expression of genes involved in DNA synthesis, repair, and recombination was downregulated in the tumor cells compared with the control cells. Using c-fos and c-jun, two of the differentially expressed genes, as model genes, we have found that in the nontransformed BALB/c-3T3 cells, the beryllium-induced transcriptional activation of these genes was dependent on pathways of protein kinase C and mitogen-activated protein kinase and independent of reactive oxygen species. These results indicate that beryllium-induced cell transformation and tumorigenesis are accompanied by and are possibly a product of alterations in expression of genes related to cancer and to DNA synthesis, repair, and recombination.
Pius Joseph, MS 3014, Toxicology and Molecular Biology Branch, CDC/NIOSH, 1095 Willowdale Road, Morgantown, WV 26505