HER2.taNK(NantKwest)

Chimeric antigen receptor-engineered NK cells hold promise for adoptive cancer immunotherapy. In one such approach, the ErbB2 (HER2)-specific CAR-NK cell line NK-92/5.28.z is under investigation as an off-the-shelf therapy in a phase I trial in glioblastoma patients. To evaluate activity of NK-92/5.28.z cells against ErbB2-positive breast cancer, here we developed an organoid model derived from CKP mice that allows conditional activation of oncogenic driver mutations. Expression of ErbB2 and Cre recombinase in CKP mammary epithelial cells induced malignant transformation, with the resulting EC-CKP cells characterized by neoplastic morphology, loss of p53, and constitutive activation of the MAP kinase pathway. NK-92/5.28.z cells demonstrated potent CAR-mediated cytotoxicity against EC-CKP organoids, with tumor cell lysis dependent on exposure time and organoid size. In vivo passaging of EC-CKP organoids revealed cellular plasticity and induced an EMT phenotype associated with increased resistance to standard therapies. Importantly, NK-92/5.28.z cells retained high and specific cytotoxicity against these breast cancer cells in vitro and in an aggressive organoid-based in vivo mouse model that reflects advanced-stage disease. Our data highlight the therapeutic potential of NK-92/5.28.z cells against ErbB2-positive breast cancer, supporting their further development toward clinical application.

Treatment resistance and immune escape are hallmarks of metastatic rhabdomyosarcoma (RMS), underscoring the urgent medical need for therapeutic agents against this disease entity as a key challenge in pediatric oncology. Chimeric antigen receptor (CAR)-based immunotherapies, such as the ErbB2 (Her2)-CAR-engineered natural killer (NK) cell line NK-92/5.28.z, provide antitumor cytotoxicity primarily through CAR-mediated cytotoxic granule release and thereafter-even in cases with low surface antigen expression or tumor escape-by triggering intrinsic NK cell-mediated apoptosis induction via additional ligand/receptors. In this study, we showed that bortezomib increased susceptibility toward apoptosis in clinically relevant RMS cell lines RH30 and RH41, and patient-derived RMS tumor organoid RMS335, by upregulation of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor DR5 in these metastatic, relapsed/refractory (r/r) RMS tumors. Subsequent administration of NK-92/5.28.z cells significantly enhanced antitumor activity in vitro. Applying recombinant TRAIL instead of NK-92/5.28.z cells confirmed that the synergistic antitumor effects of the combination treatment were mediated via TRAIL. Western blot analyses indicated that the combination treatment with bortezomib and NK-92/5.28.z cells increased apoptosis by interacting with the nuclear factor κB, JNK, and caspase pathways. Overall, bortezomib pretreatment can sensitize r/r RMS tumors to CAR- and, by upregulating DR5, TRAIL-mediated cytotoxicity of NK-92/5.28.z cells.