Prostate cancer is the second most common cancer in men worldwide, and its most aggressive form — metastatic castration-resistant prostate cancer — remains notoriously difficult to treat. One major obstacle is that these tumors are immunologically "cold": the immune system does not recognize or attack them effectively. A new study from Weill Cornell Medicine and Cornell Engineering suggests a surprisingly simple solution built from one of the most abundant materials on Earth.
Researchers led by Dr. Michelle Bradbury and Professor Ulrich Wiesner have shown that ultrasmall silica nanoparticles — called Cornell Prime dots, or C' dots — can both kill prostate tumor cells directly and transform the tumor microenvironment into an immunologically "hot" state. In mouse models of aggressive prostate cancer, the treatment induced several complete remissions.
The particles trigger a form of programmed cell death called ferroptosis — a process driven by runaway oxidation of the fatty molecules that make up cell membranes. The C' dots, originally developed for medical imaging, appear to pick up positively charged iron ions from the bloodstream and carry them inside tumor cells, where the iron catalyzes this destructive oxidation. Remarkably, healthy cells are largely unaffected.
At the same time, the particles convert the tumor's immune environment. T cells, macrophages, and other immune cells in the tumor vicinity switch from inert or actively immunosuppressive modes to robust antitumor activity. Cold tumors become hot. In combination with existing immunotherapies, the effect was even more pronounced — suggesting that C' dots could dramatically enhance the effectiveness of checkpoint inhibitors.
The study, published June 15 in Cancer Research, a journal of the American Association for Cancer Research, evaluated the particles targeted specifically to prostate cancer cells using a molecule that homes in on a prostate cell surface protein called PSMA. Even in non-prostate tissues where the particles briefly concentrated, such as the spleen, there was no sign of toxicity.
Wiesner noted a fascinating connection: silica is abundant in leafy greens, bananas, and cereal grains. "Ultrasmall silica's very early and ubiquitous presence in the environment and foods has given it a connection to biology that we're only beginning to glimpse," he said. The particles have already progressed into advanced-phase clinical trials for image-guided surgery, and the new findings support their investigation in cancer immunotherapy trials.
Knowledge takeaway: Engineered silica nanoparticles (C' dots) simultaneously trigger ferroptosis in prostate cancer cells and convert immunologically "cold" tumors into "hot" ones that the immune system can attack, achieving complete remissions in preclinical models without toxicity to healthy tissues.