Radiation, chemicals, heredity, and viruses have all been linked to cancer. Although bacteria seem to be unlikely contributors to cancer, experts continue to look into their role in carcinogenesis.
In his book, Can Bacteria Cause Cancer?, David Hess, Ph.D., a professor and chair of the Department of Science and Technology Studies at Renesselear Polytechnic Institute, Albany, suggests that bacterial theories of cancer development have been largely overlooked.
|
The H. pyloristomach cancer link is one of the few accepted connections between cancer and bacteria. However, Hess argues that bacterial theories related to cancer may not have been given proper consideration.
"I am not a microbiologist and I dont claim that there is an established relationship, but I can offer an historical perspective on the issue," Hess said in an interview. "I think it is fair to say that the older attempts to find a single bacterial agent represent a rejected program. However, with emerging linkages between H. pylori and cancer, the research field may be reopening.
"If you look back in the history of science, a number of chronic diseases have been linked to bacteria, so it is not entirely unreasonable to wonder if the long history of clinical findings of bacteria associated with tumor samples or the blood of cancer patients suggests an overlooked pathogenic role."
Hess added that bacterial advocates were largely ignored because emerging trends favored todays conventional therapies and because of the extreme nature of some bacterial theories.
"There is good evidence that the bacterial theories and therapies were pushed aside by the emerging trends in support of the chemotherapy and radiation therapy," said Hess. "There was also evidence that advocates overstated their case by claiming that a single, pleomorphic bacterium caused all cancers."
However, with the acceptance of H. pylori as a cause of stomach cancer, more doctors and researchers are studying other cancer and bacteria connections.
"Theres no reason to think that the association between H. pylori and cancer is unique," says Julie Parsonnet, Ph.D., associate professor and chief of the Division of Infectious Diseases and Geographic Medicine at the Stanford University School of Medicine.
Research continues to associate bacteria with other lesser-known cancers. "For instance, theres an established relationship between low-grade non-Hodgkins lymphoma of the stomach and H. pylori," said Charles Rabkin, M.D., of the Division of Cancer Epidemiology and Genetics at the National Cancer Institute. "Theres also a subset of gall bladder cancer cases that have been associated with Salmonella typhi and Salmonella paratyphi."
According to Rabkin, there is also research that suggests bacterial associations, both causal and protective, with colorectal cancer. Additionally, cancers such as childhood acute lymphoblastic leukemia may have bacterial connections. However, direct evidence in both cases is lacking.
Despite the increased attention, some scientists believe that the H. pyloristomach cancer connection is the exception and will not become the rule.
"There is no evidence that bacteria, besides H. pylori, contribute to the development of human cancer in any significant way," said Henry C. Pitot, M.D., Ph.D., a professor in the Department of Oncology at the University of Wisconsin, Madison.
"Chronic infections have been shown to enhance or promote skin neoplasia in humans during the days when no antibiotics were available," Pitot said.
Rabkin noted that there are many problems in establishing associations with other cancers. "Once tumors develop there is an increased risk of bacterial infection," he said. "Often it can be difficult to determine if the bacteria caused the tumor or if the tumor developed before the bacterial infection. Given the potential pitfalls, open-minded skepticism is needed in serious consideration of other bacterial causes of cancer."
![]() |
||||
|
Oxford University Press Privacy Policy and Legal Statement |