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Gene expression profile in BALB/c-3T3 cells transformed with beryllium sulfate
1Molecular Epidemiology Laboratory, Toxicology and Molecular Biology Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505, USA.
Abstract:
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 the 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.
Insights
Beryllium exposure alters gene expression, upregulating cancer-related genes and downregulating DNA repair genes, driving cell transformation and tumor formation. These changes are linked to specific molecular pathways.
Area of Science:
- Molecular Biology
- Toxicology
- Oncology
Background:
- Beryllium exposure is linked to cell transformation and tumorigenesis.
- The molecular mechanisms underlying beryllium-induced cancer require further elucidation.
Purpose of the Study:
- To investigate differential gene expression in beryllium-induced tumors.
- To identify molecular pathways involved in beryllium-induced cell transformation and tumorigenesis.
Main Methods:
- Utilized cDNA expression microarrays to compare gene expression profiles between tumor cells and nontransformed control cells.
- Confirmed differential gene expression using reverse transcription-polymerase chain reaction (RT-PCR).
- Investigated signaling pathways (protein kinase C, mitogen-activated protein kinase) involved in the transcriptional activation of specific genes.
Main Results:
- Identified 18 differentially expressed genes (at least twofold change) in tumor cells compared to controls.
- Observed upregulation of nine cancer-related genes (e.g., c-myc, c-jun) and downregulation of nine DNA synthesis, repair, and recombination genes (e.g., MCM4, MSH2).
- Demonstrated that beryllium-induced transcriptional activation of c-fos and c-jun is mediated by protein kinase C and mitogen-activated protein kinase pathways.
Conclusions:
- Beryllium-induced cell transformation and tumorigenesis are associated with significant alterations in gene expression.
- Upregulation of oncogenes and downregulation of DNA repair genes likely contribute to beryllium's carcinogenic effects.
- Specific signaling pathways are involved in the molecular response to beryllium exposure.