Tumors and Microbes, Sitting in a Tree…

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Science Translational Medicine  04 Apr 2012:
Vol. 4, Issue 128, pp. 128ec58
DOI: 10.1126/scitranslmed.3004065

Bacteria cozy up to tumors because of the distinct tumor microenvironment. How or why bacteria prefer the company of tumors to healthy tissue remains something of a mystery. Now, Cronin et al. have figured out a way to track bacteria in mice in real time, to learn more about what makes the tumor microenvironment so attractive to these microbes.

By modifying nonpathogenic and pathogenic bacteria to express the luxABCDE operon, Cronin and colleagues were able to monitor bacterial growth in tumor-bearing mice in real time using three-dimensional bioluminescent imaging. The intensity of the luminescence increased as more microbes accumulated in a target area. As an added bonus, the luminescent signal could be coregistered with microcomputed tomography for detailed anatomic resolution. Their imaging approach had sufficient resolution to demonstrate that certain bacterial species, such as Bifidobacterium brevi, actually localize and replicate in clusters spaced throughout the tumor. This sheds light on the bacterium’s capacity for growth in tumors, as well as the heterogeneity of the tumor microenvironment, and has implications not only for bacteriolytic therapies, but also for anticancer therapeutics. Given the high spatial resolution demonstrated in this study, it is possible that bacteria could be used as a surrogate marker for tumor activities in vivo. Such high-resolution bioluminescence will enable researchers to better understand the kinetics of bacterial germination in the context of human cancer therapy and could provide a different method of monitoring microbes from a general infectious disease perspective.

M. Cronin et al., High resolution in vivo bioluminescent imaging for the study of bacterial tumour targeting. PLoS ONE 7, e30940 (2012). [PubMed]

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