MMP3 overexpression enhances CAR-T cell infiltration and antitumor activity in a CAF-enriched solid tumor model

Area of Science:

• Immunotherapy
• Oncology
• Biotechnology

Background:

• Chimeric antigen receptor (CAR) T cell therapy shows promise in blood cancers but struggles with solid tumors.
• The dense extracellular matrix (ECM) in solid tumors acts as a physical barrier, impeding T cell infiltration and efficacy.
• Overcoming ECM barriers is crucial for advancing CAR T cell therapy in solid tumor treatment.

Purpose of the Study:

• To engineer CAR T cells capable of overcoming the physical barriers posed by the tumor extracellular matrix (ECM).
• To investigate the impact of co-expressing matrix metalloproteinase-3 (MMP3) on CAR T cell function and anti-tumor activity in solid tumors.
• To assess the therapeutic potential of MMP3-engineered CAR T cells in various pre-clinical models, including those with challenging tumor microenvironments.

Main Methods:

• CAR T cells targeting mesothelin or B7H3 were engineered to co-express matrix metalloproteinase-3 (MMP3).
• In vitro assays (Matrigel-based) and in vivo models (xenograft and syngeneic) enriched with cancer-associated fibroblasts (CAFs) were used to evaluate MMP3-engineered CAR T cells.
• CAR T cell proliferation, activation, cytotoxicity, tumor infiltration, expansion, and anti-tumor activity were assessed.

Main Results:

• MMP3 overexpression did not compromise CAR T cell proliferation, activation, or cytotoxicity.
• MMP3-engineered CAR T cells exhibited enhanced ECM invasion and improved tumor cell killing in vitro.
• In CAF-rich models, MMP3-engineered CAR T cells showed superior infiltration, expansion, and anti-tumor effects, rescuing the function of B7H3 CAR T cells.
• MMP3 overexpression conferred potent anti-tumor activity in immunocompetent mouse models.

Conclusions:

• Co-expression of MMP3 is a straightforward and potent strategy to enhance CAR T cell infiltration through ECM barriers.
• MMP3 engineering significantly improves the efficacy of CAR T cell therapy in solid tumors, even within challenging microenvironments.
• This approach holds promise for advancing CAR T cell therapy for solid tumor indications.