Researchers at Weill Cornell Medicine and Cornell's engineering school have engineered microscopic particles that obliterate prostate tumors through a two-pronged assault: directly destroying cancer cells while simultaneously reviving the body's dormant immune defenses. In preclinical studies using mice with aggressive prostate cancer, the approach produced complete tumor remissions, clearing a potential pathway toward human testing.
The particles, called Cornell Prime dots or C' dots, are made from amorphous silica, the same form of silicon dioxide that occurs naturally in foods and fossilized marine organisms. Originally designed as imaging tracers for surgery, the particles were recently found to selectively obliterate cancer cells while leaving healthy tissue largely untouched.
In the study published June 15 in Cancer Research, researchers injected the nanoparticles into tumor-bearing mice and watched a transformation unfold. The particles made cancer cells extremely vulnerable to a process called ferroptosis, a specialized form of self-destruction driven by overwhelming oxidation inside cells. The mechanism appears to hinge on the particles' ability to collect positively charged iron ions from the bloodstream and ferry them into tumor cells, where the iron fuels the destructive oxidation cascade.
"It seems unreal how is it possible that rather than a single pathway we see all these effects happening simultaneously and only in tumors and not in healthy tissues," said Dr. Ulrich Wiesner, co-leader of the research. He hypothesized that silica's widespread presence in nature and everyday foods may have given it an evolutionary connection to human biology that scientists are only beginning to understand.
Flipping the Immune Switch
Beyond killing tumor cells directly, the particles orchestrated a broader transformation in the cancer microenvironment. T cells, macrophages, and other immune sentries that had been suppressed or dormant suddenly shifted into aggressive cancer-fighting mode. The shift was so pronounced that the tumors became substantially more responsive to existing immunotherapy drugs.
To ensure precision targeting, the research team attached molecules to the particles that recognize PSMA, a protein displayed on prostate cancer cell surfaces. Although some particles briefly accumulated in organs like the spleen, the team detected no signs of toxicity outside tumor tissue.
The survival data proved the most striking. Mice treated with the C' dots alone or with standard immunotherapy showed modest survival gains. But when researchers combined the nanoparticles with immune checkpoint blockade therapy, four of ten mice achieved complete or near-complete remissions with indefinite survival.
Adding a third component called CSF-1R blockade, which targets tumor-associated immune cells, pushed complete remissions to five of ten mice.
"We think there's nothing else out there that has such a strong and durable tumor growth suppressing effect," said Dr. Michelle Bradbury, the study's senior author and director of the Molecular Imaging Innovations Institute at Weill Cornell Medicine.
The convergence of direct cell killing with immune reprogramming addresses a critical weakness in current cancer therapy. Prostate cancer has historically resisted long-term responses to immunotherapy alone, leaving oncologists seeking combinations that work in concert.
"By creating conditions that support a more effective antitumor immune response, these particles may help unlock the full potential of immunotherapy in prostate cancer, where durable responses have historically been difficult to achieve," said Dr. Jedd Wolchok, director of the Sandra and Edward Meyer Cancer Center and chief of the Parker Institute for Cancer Immunotherapy at Weill Cornell.
The research team is now preparing to evaluate the safety and effectiveness of the treatment in human clinical trials, with the long-term vision of developing ultrasmall silica particles as a new class of cancer therapy capable of simultaneously influencing inflammatory, immune, and metabolic pathways.
Author Jessica Williams: "This is the kind of elegant solution to cancer that researchers should be chasing: multiple biological effects from a single, naturally occurring substance, but so far it has only worked in mice."
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