Engineering Bi-Specific CAR-NK Cells to Restore Antibody-Dependent Cellular Cytotoxicity in Solid Tumors

Area of Science:

• Immunology
• Cancer Biology
• Cell Therapy

Background:

• Natural Killer (NK) cell immunotherapy efficacy is limited by the ovarian tumor microenvironment (TME).
• Transforming Growth Factor-beta (TGF-β) in the TME inhibits NK cell function, specifically CD16-mediated Antibody-Dependent Cellular Cytotoxicity (ADCC).

Purpose of the Study:

• To elucidate the molecular mechanisms of TGF-β-induced NK cell suppression in ovarian cancer.
• To evaluate a bi-specific Chimeric Antigen Receptor (CAR) engineered NK cell strategy to overcome TGF-β-mediated inhibition.

Main Methods:

• Primary peripheral blood NK (PBNK) cells were treated with TGF-β to assess phenotypic and functional changes.
• NK-92 cells were engineered with a bi-specific CAR targeting Folate Receptor Alpha (FRα) and CD16.
• CAR-NK cell efficacy was evaluated in vitro and in ovarian cancer-derived spheroids, including synergy with Trastuzumab.

Main Results:

• TGF-β induced sustained SMAD2 phosphorylation, reduced activating receptors (CD16, NKG2D), and increased exhaustion markers (PD-1) in NK cells.
• TGF-β-treated NK cells exhibited impaired infiltration and cytotoxicity against ovarian cancer spheroids.
• Bi-specific CAR-NK cells successfully infiltrated tumoroids and, with Trastuzumab, mediated potent ADCC-induced tumor cell lysis, bypassing TGF-β suppression.

Conclusions:

• The TGF-β/SMAD2 signaling pathway is a key mechanism of NK cell dysfunction in the ovarian TME.
• Bi-specific CAR-NK cell platforms represent a promising therapeutic approach to restore NK cell anti-tumor activity in ovarian cancer by overcoming TME-induced suppression.