Biology

Dr.Ritesh Kumar
Texas A & M Health Science Center, Houston, Texas, USA

Streptococcus gallolyticus subsp. gallolyticus has long been known to have a strong association with colorectal cancer (CRC). This knowledge has important clinical implications, and yet little is known about the role of S. gallolyticus on CRC and the underlying mechanisms. Here we demonstrate that S. gallolyticus promotes human colon cancer cell proliferation in a manner that depends on cell context, bacterial growth phase and direct contact between bacteria and colon cancer cells. In addition, we observed increased levels of β-catenin, c-Myc and PCNA in colon cancer cells following S. gallolyticus treatment. Knockdown or inhibition of β-catenin abolished S. gallolyticus effect. Furthermore, mice treated with S. gallolyticus had significantly higher tumor burden and dysplasia grade, increased cell proliferation and β-catenin level in colonic crypts compared to mice treated with control bacteria. Finally, we showed that S. gallolyticus is present in the majority of CRC patients and is preferentially associated with tumor compared to normal tissues obtained from CRC patients. These results provide new information and establish a tumor promoting role of S. gallolyticus that involves specific bacterial and host factors. The concept that microbes are involved in the development of CRC is gaining recognition, raising hope that we may be able to exploit knowledge about microbes to improve cancer diagnosis and treatment by incorporating microbes into clinical strategies.