Silicon Microparticles Boost Effectives of Potential Breast Cancer Vaccines

By LabMedica International staff writers
Posted on 20 May 2015

Microparticles constructed from porous silicon were found to increase the effectiveness of potential anti-breast-cancer vaccines by stimulating a type I interferon response even when not carrying any specific antigen.

Investigators at Houston Methodist Research Institute (Texas, USA) were interested in improving the performance of vaccines targeting the breast cancer HER2 oncoprotein. These vaccines have mostly not been very potent because of inefficient vaccine delivery, a poor immune response at the site of the tumor, and other factors.

$Image: The porous silicon microparticles are about one micrometer in diameter. The hollow channels within each microparticle can be loaded with antigens—such as HER2—that can help train the immune system to recognize and destroy cancer cells overexpressing HER2 (Photo courtesy of Dr. Haifa Shen\'s laboratory, Houston Methodist Research Institute).$

Image: The porous silicon microparticles are about one micrometer in diameter. The hollow channels within each microparticle can be loaded with antigens—such as HER2—that can help train the immune system to recognize and destroy cancer cells overexpressing HER2 (Photo courtesy of Dr. Haifa Shen\'s laboratory, Houston Methodist Research Institute).

In a study published in the April 30, 2015, online edition of the journal Cell Reports, the authors described the use of porous silicon microparticles (PSM) as delivery vehicles for anti-HER2 vaccines. They reported that a PSM-based cancer vaccine displayed greatly enhanced cross-presentation and activated type I interferon (IFN-I) response in dendritic cells. PSM-loaded antigen exhibited prolonged early endosome localization and enhanced cross-presentation through both proteasome- and lysosome-dependent pathways. Dendritic cells primed with PSM-loaded HER2 antigen produced robust CD8 T-cell-dependent anti-tumor immunity in mice bearing HER2+ mammary gland tumors.

"We have shown for the first time that a microparticle can serve as a carrier for sustained release and processing of tumor antigens," said senior author Dr. Haifa Shen, professor of nanomedicine at Houston Methodist Research Institute. "But just as importantly, we learned the microparticles themselves appear to be enough to stimulate a type I interferon response, and were even transferred from one antigen-presenting cell to another to maintain a long-lasting antigen-releasing effect. PSMs persistently challenge the antigen-presenting cells to activate the T-cells, and the PSMs modify the tumor microenvironment so that the cytotoxic T-cells maintain their activity."

"We could completely inhibit tumor growth after just one dose of the cancer vaccine in the animal model," said Dr. Shen. "This is the most amazing result we have ever seen in a tumor treatment study."

Related Links:
Houston Methodist Research Institute