Gut Bacteria. It is not the name of a second-tier punk band or the title of a horror movie at a drive-in theatre. It is real, and has frightening -- if not life-threatening -- consequences, according to new research.
While it is long-known that plenty of bacteria live in the intestinal tract, serving useful purposes, such as aiding in digestion, researchers at the University of Michigan have zeroed in on the harmful effect of rogue organisms and their link to colorectal cancer. The urgency for this type of research is clear: The American Cancer Society, 136,830 people will be diagnosed this year and 50,310 will die from colon cancer.
The research took a fresh look at the question of whether the harmful bacteria caused the cancer of large intestine -- ranked by Johns Hopkins as accounting for 21 percent of all cancers and second to only lung cancer in mortality -- or if existing malignant growths were more welcoming hosts.
The University of Michigan team worked their way through this maze by using mice in microbial-gut-swapping tests. Samples of microbiome -- a complex community of microbes -- were injected with a cancer-causing agent designed to cause colon tumors and then transplanted into germ-free mice. The result, the mice that previously had what were sterilized colons before being injected, developed twice the number of tumors.
That followed with a second step. A sub-group of the mice essentially injected with colon cancer were given antibiotics, and fewer and smaller tumors were the result. The researchers were then better able to determine which populations of bacteria were more closely associated with colon cancer, simply by examining the differences in the microbial universe of the test animals.
In short, inflammation is culprit. Researchers felt strongly that these particular communities of bacteria -- those in the Bacteroides, Odoribacter and Akkermansia genera, and the Prevotellaceae and Porphyromonadaceae families -- are more likely to serve as a magnet to the body's inflammatory steel. The same immune cells that cause inflammation are likely dividing into tumors.
"It's not just the microbiome, it's not just the inflammation, it's both," wrote one of the study's co-authors, Patrick Schloss, PhD.
In addition to known risk factors for colon cancer, researchers says there may actually be a living culprit responsible for contributing to at least some cases of the disease.
The Michigan team is still on the job, investigating the various populations of gut bacteria they encountered to better understand which combinations are most tumor-friendly, and which might be more helpful for patients to make their colons less hospitable to malignant growths. That could lead to probiotic-type treatments that could lower colon-cancer risk.
"If you can better understand what functions in the microbial community are important for protecting against tumor formation or making it worse, we can hopefully translate those results to humans to understand why people do or do not get colorectal cancer, to help develop therapeutics or dietary manipulations to reduce people's risk," said Schloss.
A 2013 article in Medicalnewstoday.com, penned by Catherine Paddock, PhD, drew a similar conclusion when research was presented by a research team from the University of Nottingham in the UK.
Presented at last year's General Microbiology Autumn Conference, the study showed that "common stomach bacterium" with known connections to stomach cancer -- as well as duodenal ulcers -- could be "disarming the part of the immune system that triggers inflammation."
It identified the pathogen as Helicobacter pylori, a bacterium that "establishes a life-long infection in humans and is estimated to inhabit the stomach lining of around half the world's population."
The research team found that H. pylori -- linked to more than half the cases of stomach cancer by the American Cancer Society -- is able to suppress the body's natural production of human beta defensin 1 (hβD1), an antimicrobial agent found in the stomach lining, where it helps to stave off bacterial infection, the article added. While 50% of people are infected with H. pylori, with only 1-2% of them going on to develop gastric cancer. Nonetheless, much like pancreatic cancer, survival rates are low because the symptoms do not usually emerge until the cancer is in the later and less-treatable stages.
The team examined tissue samples biopsied from the stomach lining of 54 patients being treated at Nottingham's Queens Medical Centre and found that levels of hβD1 were 10 times lower in patients infected with H. pylori. Additionally, according to the study, patients with the lowest level of the antimicrobial agent had the highest level of the bacteria. Much work still remains to be done in connecting all the dots, as the article indicated that those with H. pylori are actually at a lower risk of other types of cancer and that it may work as a shield against stroke.
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