Harnessing CD70-Targeted CAR-NK Cells: A Promising Approach for Hematological and Solid Cancer Therapies

Cellular immunotherapy has achieved FDA approval for certain treatments, but autologous CAR-T cell therapies are not without their drawbacks, such as safety issues and production limitations. An alternative approach is allogeneic CAR-NK cell therapy, which offers a readily available solution that avoids the challenges of CAR-T cell production. This therapy is especially promising for acute myeloid leukemia (AML) due to the natural ability of NK cells to target cancer cells, which can be further enhanced by a CAR targeting an antigen expressed by AML cells.

CD70 is a target of interest for CAR therapy in AML, as it is highly expressed on leukemic stem cells and blasts but not in normal bone marrow hematopoietic stem cells. It is also linked to other conditions such as NHL and renal cell carcinoma (RCC). However, CD70 is only expressed in immune cells like T, B, DC, and NK cells, and not in resting peripheral blood NK cells, but its expression increases upon NK cell activation.

Our research has shown that incorporating CD70-specific CARs into NK cells can lead to a reduction in cell expansion due to fratricide. Interestingly, the absence of CD70 does not hinder NK cell growth or their natural ability to kill target cells. By utilizing the TcBuster Transposon System, we successfully introduced a CD70 CAR and an IL15 gene into primary human NK cells while simultaneously removing CD70 using CRISPR/Cas9. This one-step process achieved high CAR integration and CD70 knockout rates.

The modified CAR-NK cells showed resistance to fratricide and expanded well after activation. The IL15 gene also helped the CAR-NK cells to persist longer in vitro without needing additional cytokines. In tests, these engineered cells were effective against various CD70-positive tumor cell lines, expressed markers of cytotoxicity, and produced cytokines such as IFNγ and TNFα.

These findings suggest that CAR-NK cell therapy targeting CD70 could be a viable treatment for AML, RCC, and other malignancies that express CD70, while also mitigating the risk of fratricide through the use of a non-viral transposon system in combination with CRISPR/Cas9 editing.