Treatment of transplanted rat tumours with double-stranded RNA(BRL 5907). II. Treatment of pleural and peritoneal growths

Our plain-English summary of Treatment of transplanted rat tumours with double-stranded RNA(BRL 5907). II. Treatment of pleural and peritoneal growths, by M.V. Pimm, R.W. Baldwin (British Journal of Cancer, 1976).

The study

• Authors: M.V. Pimm, R.W. Baldwin
• Journal: British Journal of Cancer
• Published: 1976;33(2):166-71
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Intrapleural growth of transplanted rat tumours was prevented or retarded by intrapleural administration of double-stranded RNA. A similar suppression of growth was achieved with peitoneal tumours by the intraperitoneal injection of the compound. These studies indicate the possible potential of this form of treatment of thoracic and peritoneal tumours for clinical application in the treatment of mesothelioma.

In plain English

This was an animal experiment in inbred Wistar rats at the University of Nottingham. It did not study asbestos or test any mesothelioma. The authors injected rat sarcomas Mc7, Mc57 and Sp24 and mammary carcinoma AAF57 into the chest (pleural) or abdominal (peritoneal) cavity. They treated the rats with fungal virus double-stranded RNA (ds-RNA, BRL 5907), usually mixed with the tumour cells. With sarcoma Mc7, 250 micrograms of ds-RNA completely suppressed pleural tumour growth in three tests, judged by finding no tumours visible without a microscope when the experiments ended (Day 30-55), while all but 2 of 15 control rats developed pleural tumours. Giving ds-RNA several days before the tumour cells had no effect. With sarcoma Mc57, treatment 2 or 4 days after the tumour cells still suppressed growth or prolonged survival. The weakly immunogenic tumours AAF57 and Sp24 grew in all treated rats, though survival was longer in some tests. Results in the abdominal cavity were similar. The authors concluded the treatment had possible potential for clinical use against mesothelioma, but said its toxicity still needed comparing with BCG.

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: Animal experiment: transplanted rat tumours in the pleural or peritoneal cavity, treated with ds-RNA injected into the same site, with survival compared against untreated control rats
• Who was studied: Rats of an inbred Wistar strain at the Cancer Research Campaign Laboratories, University of Nottingham, in groups of roughly 3 to 7 per arm. The transplanted tumours were sarcomas Mc7, Mc57 and Sp24 and mammary carcinoma AAF57, either induced with chemical carcinogens or arising spontaneously. The study dates are not given.
• Exposure: No asbestos exposure. The treatment was fungal virus double-stranded RNA (BRL 5907), 100 or 250 micrograms, injected intrapleurally or intraperitoneally. It was mostly given mixed with the tumour cells, in some tests 5 or 7 days before the tumour cells (per Table I), and in one test 2 or 4 days after.
• Main results:
  • Sarcoma Mc7, pleural, 100 micrograms ds-RNA with 1 x 10^6 cells: growth was not completely suppressed, but survival of treated rats (16-44 days) was longer than that of controls (12-24 days).
  • Sarcoma Mc7, pleural, 250 micrograms ds-RNA with 2 x 10^6 cells, in three further tests: complete suppression, judged by the absence of macroscopically visible tumours when the experiments ended (Day 30-55). All but 2 of 15 control rats developed intrapleural tumours and were killed between Days 15 and 40.
  • Sarcoma Mc7 (Experiment 5): ds-RNA given at the same time as the tumour cells completely suppressed growth, but ds-RNA given days before the tumour challenge had no effect.
  • Sarcoma Mc57, pleural, 250 micrograms ds-RNA: growth was completely arrested in Experiment 7 and inhibited with prolonged survival in Experiments 6 and 8. In Experiment 8, treatment delayed until 2 or 4 days after tumour challenge still completely suppressed growth or prolonged survival.
  • Weakly immunogenic tumours, pleural: with mammary carcinoma AAF57 (5 x 10^2 or 1 x 10^3 cells plus 250 micrograms ds-RNA), tumours grew progressively in all recipients, with a small but significant increase in survival. With sarcoma Sp24, tumours grew in all treated rats, with a significant survival increase in 2 of the 3 tests.
  • Peritoneal: growth of sarcomas Mc7 and Mc57 (2 x 10^6 cells) was totally suppressed by 250 micrograms ds-RNA. Sarcoma Sp24 (2-5 x 10^4 cells) and mammary carcinoma AAF57 (1 x 10^4 cells) were not suppressed, although survival increased significantly in the Sp24-treated rats.
• The authors' conclusion: The authors concluded that ds-RNA injected into the pleural and peritoneal cavities may control tumour growth at these sites, and that this indicates possible potential for clinical use in treating mesothelioma. No mesothelioma tumours were tested.
• Limitations the authors state:
  • The authors stated that, before clinical use, the toxicity of ds-RNA needs to be compared with that of bacterial adjuvants such as BCG.
  • The authors stated that the mode of action, including the role of host factors, had not yet been established and that tests were in progress.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma.

Related studies

• Proceedings: B.C.G. treatment of pleural and peritoneal tumour growth in rats — M.V. Pimm (1974)
• Failure to demonstrate tumour-associated transplantation antigens on asbestos-induced mesotheliomas in rats — D.G. Brown, J.C. Wagner, et al. (1980)
• Pleuro-pulmonary tumours detected by clinical and chest X-ray analyses in rats transplanted with mesothelioma cells — F. Le Pimpec-Barthes, I. Bernard, et al. (1999)
• Tumorigenicity of cellulose fibers injected into the rat peritoneal cavity — R.T. Cullen, B.G. Miller, et al. (2002)
• Double-Stranded RNA Structural Elements Holding the Key to Translational Regulation in Cancer: The Case of Editing in RNA-Binding Motif Protein 8A — A. Abukar, M. Wipplinger, et al. (2021)
• Histology and ultrastructure of serially transplanted rat mesotheliomas — J.C. Wagner, N.F. Johnson, et al. (1982)

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