A specialized vaccine made from induced pluripotent stem cells (iPSCs) can slow tumor growth in mouse models of breast, lung, and skin cancers, research from Stanford University shows. This vaccine also may prevent recurrence of the disease.
“What surprised us most was the effectiveness of the iPSC vaccine in re-activating the immune system to target cancer,” lead author Joseph C. Wu, MD, PhD, said in a press release. Wu is with Stanford’s Cardiovascular Institute and Institute for Stem Cell Biology and Regenerative Medicine.
For almost a century, scientists have known that tumors can be cleared from the body after immunization with embryonic materials containing embryonic stem cells. Unlike traditional vaccinations where single antigens (proteins that drive immune responses) are presented to the immune system to induce an immune response, whole-cell vaccination from embryonic stem cells can present a wider range of antigens. Some of these antigens are known, but many of them are not. The presentation of a broad variety of antigens allows the immune system to simultaneously target multiple antigens and may lead to a more pronounced and prolonged immune response.
Using embryonic stem cells is restricted for ethical reasons. However, researchers have figured out how to generate stem cells from adult cells. These are called induced pluripotent stem cells (iPSCs). Because the iPSCs are generated from one’s own cells, the tumorigenic and immunogenic properties of these iPSCs can better reflect the host’s own tumor.
In this study, “Autologous iPSC-Based Vaccines Elicit Anti-tumor Responses In Vivo,” published recently in Cell Stem Cell, researchers tested the hypothesis that vaccines generated from iPSCs may be able to induce an immune response against different cancers in mouse models.
By comparing the genes expressed by tumors and by the iPSCs generated from the host animal, researchers found a large number of overlapping genes. This was the first evidence to suggest that using iPSCs as a vaccine could prime the host to develop immunity against the tumor-specific antigens. Therefore, these iPSCs could be a administered as a type of immunotherapy — an anti-cancer vaccine.
In a mouse model of breast cancer, 40 mice received versions of the iPSC vaccine that had been inactivated by irradiation. In seven out of 10 mice, tumors had regressed completely. In the remaining 30 percent, tumors had significantly shrunk in size.
Similar results were seen in mouse models of lung cancer.
Although initial treatment in a melanoma mouse model did not significantly reduce tumor growth, treatment with this vaccine could prevent the recurrence of melanoma tumors after primary tumor removal.
“This approach may have clinical potential to prevent tumor recurrence or target distant metastases,” Wu said.
This study provides the first evidence that, in the future, a patient’s own cells may be reprogrammed into iPSCs and administered as an anti-cancer vaccine to shrink tumors. Additionally, this new immunotherapy also could be administered after surgery, chemotherapy, or radiation therapy to prevent cancer recurrence.