The Fascinating and Evolving Story of Bacteria and Cancer

Dr Eric Topol, a cardiologist and director of the Scripps Translational Science Institute, writing over the weekend: It was medical dogma: cancer tissue is sterile. That's what we had learned and taught in medical school for decades even though bacteria were detected in tumors more than 100 years ago. When studies were reported asserting that bacteria were present in tumor tissue, they were consistently debunked as representing contaminants. Then came new tools that include single-cell sequencing and sophisticated spatial profiling providing high-resolution portraits of tumors. The new dogma is that bacteria have a pervasive (yet variable) presence within and across solid tumors -- the "presence of intratumoral bacteria being designated a hallmark of cancer." Furthermore, where bacteria are more apt to be found within tumor regions, T cell recruitment and function is suppressed. These regions of tumor are micro-niches exhibiting immune evasion. Just as that has been determined, there was a new twist this week: engineering bacteria to induce a potent T cell immune response to kill the tumor. This can be viewed as the polar opposite. Instead of bacteria improving a tumor's ability to duck our immune response and spread, this represents clever ways to genetically manipulate bacteria (aka "designer bugs" with the schematic in the linked post) to make it considerably more antigenic, a new route to immunotherapy.

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