SKIN TUMORIGENESIS BY 7,12-DIMETHYLBENZ(A)ANTHRACENE: INHIBITION BY ACTINOMYCIN D

Hydrocarbon carcinogens induce p53 activity in normal mouse tissue

Previous studies led to the suggestion that a sub class of hydrocarbon carcinogens have the capacity of damage DNA and evade normal cellular defence mechanisms. To examine the ability of hydrocarbon carcinogens to induce p53 transcriptional activity in normal tissues, we have used transgenic mice in which LacZ transgene is driven by a p53 response element. We demonstrate that transcriptionally active p53 is induced in normal tissue after exposure to putative stealth carcinogens in an identical manner to non-stealth agents.

Decreased risk of radiation-associated second malignant neoplasms in actinomycin-D-treated patients

One hundred two long-term survivors of childhood cancers with second malignant neoplasms (SMNs) were collected from 10 institutions. Forty-seven cases fulfilling study criteria were studied to determine the risk of developing a SMN in irradiated fields after exposure to various chemotherapeutic agents. The case control method was used. The risk of developing such tumors was decreased by a factor of 7 in patients receiving actinomycin-D (AMD). The "protective" effect of AMD was more pronounced in patients receiving repeated courses of the agent. No change in relative risk was found for children given antifolates, the vinca alkaloids, or alkylating agents. AMD "protection" is an unexpected finding because the agent is an oncogen in animals and an enhancer of radiation, the latter being a known carcinogen. Possible mechanisms, which remain speculative, are discussed. These results indicate the need for careful long-term observation of cancer survivors to gain understanding of the late effects of multimodal treatments.

TRANSFORMATION OF ROUS SARCOMA VIRUS: A REQUIREMENT OF DNA SYNTHESIS

Transient inhibition of DNA synthesis immediately after infection of cells with Rous sarcoma virus prevents subsequent morphological transformationof the cells. Inhibition of DNA synthesis for an identical period before infection, or later in the course of infection, has only slight effect on transformation. Thus DNA synthesis is a specific requirement in the transformation of cells by Rous sarcoma virus.

Uracil Mustard: A Potent Inducer of Lung Tumors in Mice

Uracil mustard, injected intraperitoneally, increased the incidence and average number of pulmonary tumors in A/J mice. In comparison to a typical alkylating agent, nitrogen mustard, or to urethan, uracil mustard (on a molar basis) was considerably more carcinogenic.