Saturday, August 24, 2013

breath straight kicking like cancer....,


thescientist | Fusobacterium nucleatum is a Gram-negative oral commensal microbe, but it has the potential to become pathogenic, occasionally causing periodontal disease. In October 2011, two separate teams from Canada’s BC Cancer Agency and the Broad Institute in Cambridge showed that the bacterium could also be found in the gut, where its abundance was associated with colorectal cancer. Now, two new studies present functional evidence to help explain how F. nucleatum spurs the development of cancer.

In papers published in Cell Host & Microbe today (August 13), teams led by Harvard Medical School’s Aleksandar Kostic and Case Western Reserve University’s Mara Roxana Rubinstein used a mouse model of intestinal tumorigenesis and human colon cancer cells, respectively, to show that F. nucleatum induces proinflammatory and oncogenic activities that promote the growth of colorectal cancer.

“It is usually impossible to infer whether microbes are causative or opportunistic colonizers without functional studies,” said Robert Holt, who led the BC Cancer Agency team that in 2011 reported an association between F. nucleatum in the gut and colorectal cancer but was not involved in the present studies. “Identifying an infectious origin for disease almost always starts with observing an association between the presence of a microbe and the presence of a particular pathology, but an understanding of causality—or lack thereof—requires the gradual accumulation of experimental and epidemiological evidence,” such as that reported today.

The Washington University School of Medicine’s Gautam Dantas agreed that the new work helps distinguish cause from consequence. “Is an observed altered microbiome state in a diseased individual the cause of the disease, or a symptom?” Dantas, who was not involved in the studies, wrote in an e-mail to The Scientist. The papers published today “report on significant strides towards . . . identifying the mechanisms by which a human commensal bacterium, Fusobacterium nucleatum, promotes colorectal cancer.”