Induction of p53 protein expression by sodium arsenite

Arsenic disrupts cellular levels of p53 and mdm2: a potential mechanism of carcinogenesis

The antitumor protein p53 plays a critical role in DNA repair. Inorganic arsenic exposure is associated with a wide variety of human tumors, particularly of the skin. To investigate how inorganic arsenic might interfere with DNA repair and lead to greater incidence of hyperkeratosis and skin tumors, we exposed human keratinocytes (HaCaT) to environmentally relevant concentrations of arsenite for 14 days. Arsenite reduced p53 levels while concomitantly increasing the p53 regulatory protein mdm2 levels in a dose- and time-dependent manner. We propose the disruption of the p53-mdm2 loop regulating cell cycle arrest as a model for arsenic-related skin carcinogenesis and it may be important in tumors with elevated mdm2 levels.

Are metals dietary carcinogens?

Humans have been in contact with metals almost since the beginning of our existence. In fact, one cannot even think on human evolution without considering the great role played by metals in mankind's development. Metals are common moieties of molecules involved in a wide variety of biological processes, and hence are found in virtually all living organisms. Some metals are essential for human nutrition; others are found as contaminants in foodstuffs. One feature of the normal human diet which is frequently found is the simultaneous presence of both essential and toxic metals. Other factors important in the risk-evaluation analysis of metals are their pharmacokinetics, interactions among them and with other major components of the diet, and, especially, the great differences in the dietary habits of different populations and in the regional distribution of metals. In attempting to understand the role which dietary metals could play in human carcinogenesis, we found that the many factors involved and the lack of specific information made it difficult to reach firm conclusions on the hazards of dietary metals. We hope that this paper will raise the interest of genetic toxicologists in the subject and will consequently facilitate a risk analysis of the carcinogenic potential of dietary metals.