Engineers reprogram Clostridium to attack tumors
- University of Waterloo researchers reported two linked advances for tumor-targeting Clostridium sporogenes: an oxygen-tolerance gene that helps the bacterium survive tumor edges, and a quorum-sensing circuit that times when engineered genes switch on. - The oxygen-tolerance tweak uses the noxA gene from Clostridium aminovalericum, while the signaling circuit borrows the agr system from Staphylococcus aureus to activate only after enough bacteria accumulate inside a tumor. - The pieces have not yet been fully combined in one strain or tested in tumors; Waterloo says preclinical tumor trials are the next step. (uwaterloo.ca)
Solid tumors often have a dead, oxygen-starved center and a more oxygen-exposed outer rim. That split is why University of Waterloo researchers are engineering Clostridium sporogenes, a bacterium that grows where oxygen is absent, as a possible cancer therapy. (uwaterloo.ca) (pubmed.ncbi.nlm.nih.gov) The basic idea is that spores can stay inactive in healthy, oxygen-rich tissue, then germinate inside hypoxic tumor cores. Researchers have studied that tumor-seeking behavior in clostridia for decades because solid tumors often contain necrotic, low-oxygen pockets that normal tissue does not. (pubmed.ncbi.nlm.nih.gov) (nature.com) The problem is that wild-type C. sporogenes tends to stall before finishing the job. As the bacteria spread outward from the oxygen-free core toward the tumor rim, rising oxygen levels kill them off and leave viable cancer cells behind. (pubmed.ncbi.nlm.nih.gov) (uwspace.uwaterloo.ca) One piece of the Waterloo work was to make the bacterium more oxygen-tolerant. In a 2024 Biotechnology Journal paper, the team reported that adding the noxA gene from Clostridium aminovalericum gave C. sporogenes a degree of aerotolerance. (pubmed.ncbi.nlm.nih.gov) The second piece was timing. Bacteria use quorum sensing as a kind of head count, releasing chemical signals that build up as more cells gather in one place. (uwaterloo.ca) (news-medical.net) Waterloo researchers said they inserted the agr quorum-sensing system from Staphylococcus aureus into C. sporogenes so engineered genes would switch on only after enough bacteria had accumulated in a tumor. In the recent ACS Synthetic Biology study, they tested that circuit by linking it to green fluorescent protein as a visible readout. (uwaterloo.ca) (news-medical.net) That sequencing is the safety logic behind the project. If oxygen tolerance turned on too early, the bacteria could survive in oxygen-rich places such as the bloodstream, so the team is trying to make that trait depend on bacterial density inside tumors. (sciencedaily.com) (uwaterloo.ca) The work is not yet a finished cancer treatment. Sara Sadr’s 2025 University of Waterloo thesis says the group built the aerotolerant strain and the functional quorum-sensing switch, but did not complete final integration of noxA under quorum-sensing control within that study. (uwspace.uwaterloo.ca) Waterloo said the next step is to combine both elements in one bacterium and test it against tumors in preclinical studies. For now, the result is a set of engineered parts aimed at making a tumor-colonizing microbe survive longer where cancer cells still remain. (uwaterloo.ca) (news-medical.net)
