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Stem cell-based vaccine may protect against melanoma, other cancers

An in-vivo study using induced pluripotent stem cells (iPSCs) to induce an immune response against melanoma and other cancers has produced promising results that suggest that one day a patient's own stem cells may protect them against many types of cancer.

Published online ahead of print in Cell Stem Cell (Feb. 15, 2018), the research was inspired by a finding that human and mouse stem cells express antigens on their surface that are also common to tumour cells.

“We’ve learned that [iPSCs] are very similar on their surface to tumour cells,” said the paper's senior author, Dr. Joseph Wu, in a press release. Dr. Wu is director of Stanford University’s Cardiovascular Institute in Stanford, Calif., and professor of cardiovascular medicine and of radiology.

“When we immunized an animal with genetically matching [iPSCs], the immune system could be primed to reject the development of tumours in the future. Pending replication in humans, our findings indicate these cells may one day serve as a true patient-specific cancer vaccine.”

In the study, four groups of mice were used. One was injected with a control solution, one received genetically matching iPSCs that had been irradiated to prevent the formation of teratomas, one received a generic immune-stimulating vaccine adjuvant, and one received a combination of irradiated iPSCs and adjuvant. All the mice in the study received their injections once a week for four weeks. After that, a mouse breast cancer cell line was transplanted into the animals to observe the potential growth of tumours.

One week after cancer cells were transplanted, all of the mice had developed tumours of the breast cancer cells at the injection site. These tumours grew robustly in the control groups, but shrank in size in seven out of 10 mice vaccinated with iPSCs plus the adjuvant. Two of these mice were able to completely reject the breast cancer cells and live for more than one year after tumour transplantation. Similar results were obtained when mouse melanoma and mesothelioma (a type of lung cancer) cell lines were transplanted into treated mice.

The research team also demonstrated that immune T-cells taken from vaccinated mice were able to slow the growth of breast cancer tumours in unvaccinated mice.

“This approach is particularly powerful because it allows us to expose the immune system to many different cancer-specific epitopes simultaneously,” said lead author Dr. Nigel Kooreman. “Once activated, the immune system is on alert to target cancers as they develop throughout the body.” Dr. Kooreman was a postdoctoral scholar at Stanford at the time of the study, and is now a surgical resident in the Netherlands.

The investigators hope to next look at the potential protective effect of iPSC vaccination in vitro on human cancer samples.

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