Engineered Bacteria Offers New Hope in the Battle Against Skin Cancer in Mice

Stan­ford Med­i­cine researchers have made a ground­break­ing dis­cov­ery that could pave the way for inno­v­a­tive can­cer treat­ments. By mod­i­fy­ing the genomes of skin-dwelling microbes and bac­te­ria, sci­en­tists have suc­cess­ful­ly used them to com­bat can­cer in mice. When the altered microbes were applied to the mice’s fur, their tumors began to shrink.

The bac­te­ria, Staphy­lo­coc­cus epi­der­midis, was col­lect­ed from mice fur and engi­neered to pro­duce a pro­tein that stim­u­lates the immune sys­tem to tar­get spe­cif­ic tumors. The exper­i­ment showed great promise, with the mod­i­fied bac­te­ria effec­tive­ly killing aggres­sive metasta­t­ic skin can­cer with­out caus­ing inflammation.

“It seemed almost like mag­ic,” said Michael Fis­chbach, PhD, an asso­ciate pro­fes­sor of bio­engi­neer­ing at Stan­ford. “These mice had very aggres­sive tumors grow­ing on their flank, and we gave them a gen­tle treat­ment where we sim­ply took a swab of bac­te­ria and rubbed it on the fur of their heads.”

This research delves into the large­ly unex­plored world of micro­bio­mes, which con­sist of numer­ous bac­te­ria, fun­gi, and virus­es. While gut bio­mes receive most of the atten­tion, the skin also hosts count­less microbes whose func­tions are often unknown.

In this case, sci­en­tists dis­cov­ered that Staphy­lo­coc­cus epi­der­midis cells ini­ti­ate the pro­duc­tion of immune cells called CD8 T cells. The researchers essen­tial­ly repro­grammed the S. epi­der­midis to pro­duce CD8 T cells that tar­get spe­cif­ic anti­gens relat­ed to skin can­cer tumors. Upon encoun­ter­ing a match­ing tumor, these cells rapid­ly mul­ti­plied and either reduced or entire­ly elim­i­nat­ed the tumor mass.

“Watch­ing those tumors dis­ap­pear — espe­cial­ly at a site dis­tant from where we applied the bac­te­ria — was shock­ing,” Fis­chbach said. “It took us a while to believe it was happening.”

Despite the promis­ing results, there are sev­er­al caveats to con­sid­er. The exper­i­ments were only con­duct­ed on mice, and it is unclear whether the same treat­ment would be effec­tive in humans. Stan­ford researchers are uncer­tain if S. epi­der­midis trig­gers a sim­i­lar immune response in humans, and they may need to inves­ti­gate oth­er microbes for poten­tial mod­i­fi­ca­tion. Addi­tion­al­ly, this treat­ment is designed for skin can­cer tumors and applied top­i­cal­ly; its effi­ca­cy in treat­ing inter­nal can­cers remains to be seen.