Is non-genic inheritance involved in carcinogenesis? A cytotactic model of transformation

Our plain-English summary of Is non-genic inheritance involved in carcinogenesis? A cytotactic model of transformation, by K.K. Hjelm (Journal of Theoretical Biology, 1986).

The study

• Author: K.K. Hjelm
• Journal: Journal of Theoretical Biology
• Published: 1986;119(1):89-101
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

There is convincing evidence that the patterns formed by microtubules and by other fibres and organelles in ciliates are partly determined by non-genic inherited information, the so-called cytotactic information. There is also some evidence that this exists in metazoan cells and is perhaps involved in neoplastic transformation. On this background a cytotactic model of transformation which allows new interpretation of several characteristics of cancer cells has been developed. It proposes (a) that most cells contain cytotactic information, (b) that mechanisms to repair modifications of this information exist, and (c) that transformation may result when the cytotactic information is modified beyond repair. The model further proposes that (d) the modified cytotactic information is unevenly distributed between daughter cells at the following divisions so that cells with abnormal patterns, increasing pleomorphy and malignancy, and possibly altered gene functions are formed. The cytotactic transformation is proposed to take place in one or in two steps and to be inducible not only by many usual carcinogens but also by for example aborted cell divisions. A cytotactic interpretation of cancers induced by asbestos and of certain other observations is attempted.

In plain English

This was a theoretical paper. It reported no new study of patients or animals, though it briefly mentioned the author's own experiments, published and unpublished, with single-celled organisms called ciliates. Drawing mainly on earlier published ciliate experiments, the author argued that cells may carry inherited information not stored in genes, called "cytotactic" information. The author proposed a model in which cancer-type transformation may happen, usually in two steps, when this information is changed beyond the cell's ability to repair it. Uneven sharing of the changed information between daughter cells was proposed to lead to increasingly irregular cells. The author reported that various treatments of the ciliate Tetrahymena, among them uptake of asbestos fibres, produced irregular (pleomorphic) cell lines. Some of these treatments were cited to the author's earlier papers. In some experiments, cited as unpublished and not tied to a particular treatment, more than half of treated cells gave rise to such lines. For asbestos and other mineral fibres, the author suggested that fibre damage might disturb this information, for example by causing aborted cell divisions. The author acknowledged writing with a bias toward supportive evidence and noted that no experiments had yet been designed to test the idea. The author hoped to stimulate such work.

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: Theoretical article proposing a hypothesis (a cytotactic model of transformation), based on the author's reading of previously published observations, with brief mention of the author's own published and unpublished ciliate experiments; no new patient or animal study
• Who was studied: No patient or animal study population. The article discussed observations mainly in ciliates (Paramecium, Tetrahymena, Oxytricha, Colpidium), including the author's own Tetrahymena experiments, plus some observations in other eukaryote cells and in cancer cells
• Exposure: Mineral fibres such as asbestos (no specific fibre type named), discussed as one example the model might explain; also chemical carcinogens, aborted cell divisions, implanted plastic films and formaldehyde
• Main results:
  • The author proposed that most cells contain cytotactically inherited information influencing the pattern of their organelles
  • The author proposed that modification of this information leading to transformation usually requires two steps: first a reduction in repair capacity, then a change beyond repair. Under certain conditions it may happen in one step
  • The author proposed that repeated unequal division and distribution results in cells of increasing pleomorphy and malignancy
  • The author reported that pleomorphic Tetrahymena cell lines were produced by various treatments. These included methyl cellulose, flattening, and elevated temperatures (some cited to the author's 1977 and 1978 papers), and uptake of asbestos fibres. All the treatments seemed initially to induce aborted divisions
  • In some experiments, cited as the author's unpublished work and not linked to a specific treatment, more than half of the treated cells gave rise to pleomorphic cell lines
  • For asbestos and other fibres, the author suggested that mechanical damage by long, thin fibres may cause cytotactic modifications. This could happen either by inducing aborted divisions or by altering structures that carry this information
• The authors' conclusion: The author concluded that better evidence is needed to prove the model, and hoped the ideas would stimulate experiments and reinterpretation of existing data
• Limitations the authors state:
  • The author stated the article was written with a bias toward presenting evidence in line with the model
  • The author stated that no experiments had yet been designed to test whether cytotaxis is involved
  • The author stated it is difficult to decide how similar pleomorphic ciliates are to cancer cells

Topics

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

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