Targeting SHP-1-Mediated Inhibition of STAT3 and ERK Signalling Pathways Rescues the Hyporesponsiveness of MHC-I-Deficient NK-92MI.

Natural Killer (NK) cells have shown promising prospects in 'off-the-shelf' cell therapy, particularly the NK-92 cell line, which can serve as a foundation for the next generation of universal chimeric antigen receptor (CAR)-engineered NK products. A key strategy for generating universal cellular products is the elimination of the beta-2-microglobulin (B2M) gene, which encodes a component of MHC class I molecules (MHC-I) that plays a role in the presentation of foreign antigens and in the 'licensing' or 'education' of NK cells. To functionally study the impacts of MHC-I deficiency on NK-92, we generated a B2M knockout (KO) NK-92MI (B-92) cell line and compared the multidimensional properties of B2M KO and wild-type NK-92MI cells in terms of biological phenotypes, effector functions, and transcriptomic signatures. We observed a decrease in activating receptors, cytokine production, and cytotoxicity in B-92 cells. Further analysis of signalling events revealed that the upregulated expression and phosphorylation of SHP-1 in B-92 cells inhibited the phosphorylation levels of STAT3 and ERK, thereby affecting their killing function. By knocking out SHP-1 (PTPN6), we partially restored the cytotoxic function of B-92 cells. Notably, we also found that CAR modification can overcome the hyporesponsiveness of B-92 cells. These findings will facilitate further exploration in the development of NK cell-based products.