Identification of environmental carcinogens utilizing T-cell mediated immunity

Our plain-English summary of Identification of environmental carcinogens utilizing T-cell mediated immunity, by R.H. Stevens, D.A. Cole, P.A. Lindholm, et al (Medical Hypotheses, 1986).

The study

• Authors: R.H. Stevens, D.A. Cole, P.A. Lindholm, H.F. Cheng
• Journal: Medical Hypotheses
• Published: 1986;19(3):267-85
• Read it: PubMed · Publisher

Abstract

There now exists a very large body of information that directly links the exposure to certain environmental factors with the ultimate development of specific types of human cancer. For this reason, a number of tests possessing varying degrees of biological complexity have been devised with the intent to first identify, and then ultimately reduce the risk of exposure to tumor causing agents. The presently employed chronic whole animal tests generally accepted as measures of human carcinogenicity have certain limitations in that they are lengthy to perform, very expensive, and require complicated pathological examinations of the various tissues. Consequently, there exists a need for short-term whole animal bioassays that can serve to complement such lengthy chronic studies; we are proposing that one such a test can be developed through utilizing procedures that have been designed for evaluating T-cell immunological responses.

In plain English

This article proposed that measuring T-cell (a type of white blood cell) responses in animals could serve as a short-term test for identifying cancer-causing agents. It was a hypothesis paper presenting findings from the authors' own laboratory in rats exposed to X-rays, several chemicals, asbestos and radionuclides, mostly cited to earlier publications. In the asbestos model, young adult male Fisher F344 rats received intraperitoneal injections of standard reference Canadian chrysotile B fibers, 100 mg in total over 4 weeks. Cells grown from a mesothelioma in one rat served as targets. In 12 rats with asbestos-induced peritoneal mesotheliomas, immune cells damaged both types of cultured tumor cells. Against the fibroblast-like cells the mean cytotoxicity was 8.7% (standard error 1.3%), and the authors saw no apparent significant difference between the two cultures. In the X-ray studies, 17 to 20 Gy produced small-bowel tumors. Immune reactivity was detected after 1 Gy and, according to more recent information, after as little as 10 cGy. The authors concluded that T-cell cytotoxicity may be one possible measure of cancer-causing potential, provided the hypothesis continues to be supported.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Hypothesis paper presenting findings from the authors' own laboratory's animal (rat) studies, mostly cited to earlier publications; some more recent data are given without a citation
• Who was studied: Rats (including Holtzman, Lewis Brown-Norway and Fisher F344 rats). The asbestos work used young adult male Fisher F344 inbred rats. Results for 12 tumor-bearing animals were reported for the asbestos model.
• Exposure: Asbestos model: intraperitoneal injection of 25 mg of standard reference Canadian chrysotile B fibers in saline, given over 4 weeks for a total of 100 mg per animal. Other agents covered were X-rays to the small bowel, 1,2-dimethylhydrazine (DMH), 7,12-dimethylbenz[a]anthracene (DMBA), halogenated hydrocarbons, and the radionuclides iodine-131 and technetium-99m.
• Main results:
  • In rats with asbestos-induced peritoneal mesotheliomas, immune cells caused injury and death to both cultured tumor target cell types (epithelial-like and fibroblast-like). Cytotoxicity against the fibroblast-like cells was a mean of 8.7% with a standard error of 1.3%, in a group of 12 tumor-bearing animals.
  • The authors detected no apparent significant difference in how sensitive the two mesothelioma cell cultures were to killing by immune cells from the tumor-bearing rats.
  • In rats given X-rays to the small bowel, tumors were induced at 17 to 20 Gy. Immune reactivity was identified after as little as 1 Gy.
  • According to more recent information the authors reported, immune reactivity in irradiated rats could be measured after a dose as little as 10 cGy, with cytotoxicity of 8.7% (standard error 5.4%) at 21 days after irradiation.
  • Among irradiated rats, the immune response was present whether or not they developed visible tumors. In Holtzman rats, cytotoxicity was 32.7% (standard error 3.1%) in 7 tumor-bearing rats and 29.6% (standard error 4.5%) in 7 irradiated rats with no evidence of tumors.
  • Carcinogenic halogenated hydrocarbons induced measurable cell-mediated immune responses. Chlorobenzene, described as apparently noncarcinogenic, had no effect.
• The authors' conclusion: The authors concluded that their work suggests evaluating T-cell cytotoxicity may be one possible measure of carcinogenic potential. They also proposed that localized tissue exposure to ionizing radiation be used as a standard for comparing carcinogens.
• Limitations the authors state:
  • The authors stated that their Radiation Equivalency approach depends on its assumptions holding true.
  • The authors made their proposal of rapid, inexpensive immune-based tests conditional on the hypothesis continuing to be supported.

Related studies

• Identification of carcinogens by measurement of cell-mediated immunity. III. Immunity to asbestos-induced rat peritoneal mesothelioma — D.A. Cole, R.H. Stevens, et al. (1982)
• Analysis of depressed cell-mediated immunity in asbestos workers — R.D. deShazo, J. Nordberg, et al. (1983)
• Evaluation of environmental carcinogens for cancer in man — A.L. Brown (1976)
• Risk-based indicators of Canadians' exposures to environmental carcinogens — E. Setton, P. Hystad, et al. (2013)
• An approach to estimating the environmental burden of cancer from known and probable carcinogens: application to Ontario, Canada — S.L. Greco, E. MacIntyre, et al. (2020)
• Consensus on synergism between cigarette smoke and other environmental carcinogens in the causation of lung cancer — A.E. Reif, T. Heeren (1999)

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