TLR Agonist Nano Immune Therapy Clears Peritoneal and Systemic Ovarian Cancer

Area of Science:

• Immunology
• Nanotechnology
• Oncology

Background:

• Metastatic ovarian cancer poses significant treatment challenges.
• Current immunotherapies often struggle with effective delivery and activation of anti-tumor immune responses.
• Targeting regional immune cells within the peritoneal cavity is crucial for treating peritoneal metastases.

Purpose of the Study:

• To evaluate the efficacy of intraperitoneally delivered immunogenic mesoporous silica nanoparticles (iMSN) in a mouse model of metastatic ovarian cancer.
• To investigate the immune mechanisms underlying iMSN-mediated anti-tumor activity.
• To compare the therapeutic effects of different administration routes (intraperitoneal, subcutaneous, intravenous) for iMSN.

Main Methods:

• Development and characterization of iMSN functionalized with Toll-like receptor (TLR) agonists (PEI, CpG, MPLA).
• Administration of iMSN via intraperitoneal (IP), subcutaneous (SC), and intravenous (IV) routes in mice with peritoneal ovarian cancer.
• Analysis of myeloid cell uptake, trafficking to lymphoid tissues (milky spots, FALCs), and immune cell populations (T cells).
• Assessment of tumor burden, survival, and protection against tumor rechallenge.

Main Results:

• IP delivery of iMSN rapidly activated peritoneal myeloid cells, which trafficked nanoparticles to lymphoid aggregates.
• iMSN treatment led to a decrease in suppressive T cells and an increase in activated memory T cells.
• Two doses of IP iMSN significantly reduced or cleared ovarian and colorectal tumors and provided long-term protection.
• SC and IV administration of iMSN were ineffective for peritoneal metastases, highlighting the importance of regional immune activation.
• Remarkably, IP iMSN also cleared established subcutaneous ovarian tumors, suggesting T cell homing to extraperitoneal sites.

Conclusions:

• Intraperitoneal administration of iMSN is a highly effective strategy for treating peritoneal carcinomatosis by engaging regional immunity.
• iMSN-mediated immunotherapy promotes robust anti-tumor CD8+ T cell responses and protective immunity.
• The route of administration is critical for iMSN efficacy, with IP delivery being superior for peritoneal and even distant tumors.