- An interesting 1995 Article From The British Medical
Journal
- BMJ 1995;310:1611
- 7-17-95
-
-
- The Society for General Microbiology is currently celebrating
its golden jubilee. How timely, then, for Milton Wainwright, writing in
the society's Quarterly (1995;22:48-50), to review past and present evidence
that micro-organisms can cause cancer.
-
- Current interest, of course, centres on the association
between stomach cancer and the bacterium Helicobacter pylori. Although
the case is not as watertight as that incriminating H pylori in ulcers,
several papers published over the past four years have successively strengthened
the evidence for a causal link. Epidemiological demonstrations of a higher
risk of gastric cancer among patients infected with the organism have been
supported by plausible evidence for appropriate mechanisms.
-
- But as Wainwright points out, H pylori is not the only
micro-organism now under suspicion as a cause of malignancy. At least two
recent studies, for example, have implicated bacteria in colon cancer.
-
- Wainwright's historical review shows that the idea of
microbes causing cancer took root in the 1880s, developing apace over the
early decades of this century and then virtually disappearing around the
time when the Society for General Microbiology was formed in 1945. During
the years when the theory was going strong, many different microbes (often
described as pleomorphic because of their frequent changes in morphology)
were implicated in cancer.
-
- Claims of particular interest include those of the surgeon
Sir James Young. Working at the Edinburgh Medical School in the early 1920s,
he reported the isolation of a pleomorphic organism from 34 of 40 human
tumours, and its capacity to induce progressive neoplastic change in mesodermal
cells when injected into laboratory animals. Earlier work by William Russell,
pathologist at the Royal Edinburgh Infirmary, implicated blastomyces (which
we would now call yeasts) in malignant growths.
-
- What Wainwright describes as the most bizarre claim
about cancer germs was made in 1911 by the eminent surgeon Sir Henry Butlin.
He concluded that cancer cells themselves give rise to new "unicellular
cancri"--protozoa-like organisms.
-
- So what possible relevance does any of this have to
a world in which we now see cancer as essentially a disease attributable
to oncogenes, triggered into mischief by external carcinogens such as chemicals
and radiation? The answer may be very little. On the other hand, the likely
role of H pylori in stomach cancer would have seemed frankly absurd until
just a few years ago. Moreover, though the past 50 years have seen only
sporadic papers about microbes causing cancer, some of those reports have
been impressive and have left unanswered questions.
-
- There have, for example, been suggestive claims that
mycoplasms (which can induce chromosome breaks in tissue culture) have
a role in malignancy. Other papers have implicated amoebae in breast and
stomach cancer, and protozoa and mycobacteria in other types of neoplasm.
One specific suggestion is that Mycobacterium tuberculosis may help to
induce cervical cancer by converting cholesterol in smegma into a carcinogen.
-
- No doubt many of the historical assertions about microbes
in malignancy were invalid and based on faulty experimentation or hasty
misinterpretation. But perhaps not all. As Milton Wainwright suggests,
H pylori could turn out to be only the first of several rediscovered cancer
germs.--BERNARD DIXON, European contributing editor, Biotechnology
-
- Bernard Dixon
- alancantwell@sbcglobal.net
-
-
- http://www.ariesrisingpress.com
-
- FOUR WOMEN AGAINST CANCER:
- Bacteria, Cancer and the Origin of Life
|
