Directed Evolution Makes an Oncolytic Virus More Potent Against Breast-Cancer Stem-Like Cells

Directed Evolution Makes an Oncolytic Virus More Potent Against Breast-Cancer Stem-Like Cells

Laboratory evolution produced viral clones that killed chemotherapy-resistant breast-cancer stem-like cells more effectively than the original strain.
LS
Linsey Smith
Oct 9, 2026
1 min read

Researchers have used directed evolution to make an oncolytic virus more effective at killing breast-cancer stem-like cells that had become resistant to paclitaxel.

The team repeatedly passaged the T1L strain of mammalian orthoreovirus through paclitaxel-resistant, estrogen-receptor-positive tumor spheres, producing two evolved clones, T1L SP B and C. Both killed the resistant stem-like cells more effectively than the parental strain despite showing lower infectivity and reduced viral-protein production.

Genome sequencing linked the stronger effect to specific viral mutations. All tested strains triggered apoptosis, while T1L SP B also produced markers of immunogenic cell death and increased extracellular ATP, a damage signal associated with immune activation.

The work adds to broader interest in using oncolytic viruses to stimulate tumor-specific immune responses and other living therapies engineered to act inside tumors.

The results remain preclinical. They do not establish safety or effectiveness in patients, but they suggest directed viral evolution could help target treatment-resistant cancer-cell populations.

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