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Molecular cloning and functional analysis of a novel cadmium-responsive proto-oncogene
Pius Joseph1, Yi-Xiong Lei, Wen-Zong Whong
1Molecular Epidemiology Laboratory, Toxicology and Molecular Biology Branch, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, WV 26505, USA. pcj5@cdc.gov
Abstract:
The molecular mechanisms potentially responsible for cell transformation and tumorigenesis induced by cadmium, a human carcinogen, were investigated by differential gene expression analysis of BALB/c-3T3 cells transformed with cadmium chloride (CdCl(2)). Differential display analysis of gene expression revealed consistent overexpression of mouse translation initiation factor 3 (TIF3; GenBank accession number AF271072) in the cells transformed with CdCl(2) when compared with nontransformed cells. The predicted protein encoded by TIF3 cDNA exhibited 99% similarity to human eukaryotic initiation factor 3 p36 protein. A M(r) 36,000 protein was detected in cells transfected with an expression vector containing TIF3 cDNA. Transfection of NIH3T3 cells with an expression vector containing TIF3 cDNA resulted in overexpression of the encoded protein, and this was associated with cell transformation, as evidenced by the appearance of transformed foci exhibiting anchorage-independent growth on soft agar and tumorigenic potential in nude mice. Expression of the antisense RNA against TIF3 mRNA resulted in significant reversal of oncogenic potential of the CdCl(2)-transformed BALB/c-3T3 cells. Taken together, these findings demonstrate for the first time that the cell transformation and tumorigenesis induced by CdCl(2) are due, at least in part, to the overexpression of TIF3, a novel cadmium-responsive proto-oncogene.
Insights
Cadmium exposure causes cell transformation and tumor growth by increasing translation initiation factor 3 (TIF3). Suppressing TIF3 expression reverses these cancer-promoting effects, identifying TIF3 as a cadmium-responsive proto-oncogene.
Area of Science:
- Molecular biology
- Cancer research
- Toxicology
Background:
- Cadmium (CdCl2) is a known human carcinogen.
- The molecular pathways linking cadmium exposure to cancer are not fully understood.
Purpose of the Study:
- To investigate the molecular mechanisms of cadmium-induced cell transformation and tumorigenesis.
- To identify specific genes involved in cadmium's carcinogenic effects.
Main Methods:
- Differential gene expression analysis of BALB/c-3T3 cells treated with cadmium chloride (CdCl2).
- Gene cloning and transfection studies using NIH3T3 cells.
- Assessment of anchorage-independent growth and tumorigenic potential in nude mice.
- Expression of antisense RNA to evaluate oncogenic potential reversal.
Main Results:
- Overexpression of mouse translation initiation factor 3 (TIF3) was consistently observed in cadmium-transformed cells.
- TIF3 overexpression in NIH3T3 cells led to cell transformation, anchorage-independent growth, and tumor formation.
- Inhibition of TIF3 expression using antisense RNA reversed the oncogenic potential of cadmium-transformed cells.
Conclusions:
- Cadmium-induced cell transformation and tumorigenesis are, at least partly, mediated by the overexpression of TIF3.
- TIF3 is identified as a novel cadmium-responsive proto-oncogene.
- These findings provide critical insights into the mechanisms of cadmium carcinogenicity.