Melanoma is among the most lethal forms of cancer, accounting for 80% of deaths despite comprising just 5% of skin cancer cases. Treatment options remain limited due to the genetic and epigenetic mechanisms associated with melanoma heterogeneity that underlie the rapid development of secondary drug resistance. For this reason, the development of novel treatments remains paramount to the improvement of patient outcomes. Although the advent of chimeric antigen receptor-expressing T (CAR-T) cell immunotherapies has led to many clinical successes for hematological malignancies, these treatments are limited in their utility by their immune-induced side effects and a high risk of systemic toxicities. CAR natural killer (CAR-NK) cell immunotherapies are a particularly promising alternative to CAR-T cell immunotherapies, as they offer a more favorable safety profile and have the capacity for fine-tuned cytotoxic activity. In this review, the discussion of the prospects and potential of CAR-NK cell immunotherapies touches upon the clinical contexts of melanoma, the immunobiology of NK cells, the immunosuppressive barriers preventing endogenous immune cells from eliminating tumors, and the structure and design of chimeric antigen receptors, then finishes with a series of proposed design innovations that could improve the efficacy CAR-NK cell immunotherapies in future studies.

Most of the lymphocytes in the human pregnant uterus are natural killer (NK) cells. Here, we showed that soluble HLA-G expressed by fetal trophoblast cells at the maternal-fetal interface in early pregnancy stimulated transcription of mostly the same genes in primary NK cells as an agonistic antibody to the receptor KIR2DL4. An exception was the transcription of type I interferon (IFN-I)–stimulated genes (ISGs), which were selectively induced by HLA-G through a noncanonical pathway. This ISG response required the transcription factor IRF7 and the kinase JAK1. The carboxyl-terminal portion of the KIR2DL4 cytoplasmic tail includes a sequence analogous to conserved JAK1 binding sites in IFN receptors and was required for JAK1 binding to KIR2DL4. Phosphorylation of IRF7 and the JAK substrate STAT2, which link IFN-I stimulation to ISG transcription, was detected in the nuclei of HLA-G–stimulated NK cells. Single-cell RNA sequencing (scRNA-seq) showed that HLA-G induced a broader transcriptional response in CD56 ^bright NK cells than in CD56 ^dim NK cells and that ISG expression was similar in both NK cell subsets. Comparison of our data with scRNA-seq data from the early maternal-fetal interface revealed that HLA-G induced the transcription of genes that distinguish decidual NK cells from maternal blood NK cells. Thus, ISG transcription, which is inducible by HLA-G, is detected in early pregnancy and may underlie intrinsic antipathogen resistance of NK cells in the maternal decidua.

AXL is a receptor tyrosine kinase (RTK) that is commonly expressed in metastatic melanoma and several other forms of cancer. Activation of AXL signaling is linked to tumor cell growth, invasion, metastatic transformation, drug resistance, and immune response regulation. However, treatment of metastatic melanoma continues to present clinical challenges due to its capacity to rapidly develop drug resistance, which manifests under the influence of AXL signaling. As such, AXL may be a viable antigen target for immunotherapies. Despite their successes in hematological malignancies, chimeric antigen receptor (CAR)-T cell therapies remain limited by their susceptibility to causing off-target toxicity. In contrast, natural killer (NK) cells are not associated with such risks, which makes them clinically appealing as an alternative to T cells. However, studies on the application of CAR-NK cells to treat solid tumors remain acutely scarce. To explore the clinical viability of CAR-NK cells for the treatment of metastatic melanoma, AXL-specific CAR-NK cells were generated by transfecting NK cells obtained from NK cell lines. Preliminary data from a cytotoxicity assay indicated that the cytotoxicity of CAR-NK92-MI cells against AXL-positive melanoma cell lines was significantly stronger (up to a 10-fold difference) than the corresponding parental cells. Further in vitro characterization of this CAR-NK cell line and other CAR-NK cell lines, as well as in vivo evaluation of their efficacy in a mouse xenograft model of melanoma metastasis, is underway.Citation Format: Winston Hibler, Glenn Merlino, Yan Lin Yu. Characterization of anti-AXL CAR-NK cell therapy for the treatment of melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1337. AXL is a receptor tyrosine kinase (RTK) that is commonly expressed in metastatic melanoma and several other forms of cancer. Activation of AXL signaling is linked to tumor cell growth, invasion, metastatic transformation, drug resistance, and immune response regulation. However, treatment of metastatic melanoma continues to present clinical challenges due to its capacity to rapidly develop drug resistance, which manifests under the influence of AXL signaling. As such, AXL may be a viable antigen target for immunotherapies. Despite their successes in hematological malignancies, chimeric antigen receptor (CAR)-T cell therapies remain limited by their susceptibility to causing off-target toxicity. In contrast, natural killer (NK) cells are not associated with such risks, which makes them clinically appealing as an alternative to T cells. However, studies on the application of CAR-NK cells to treat solid tumors remain acutely scarce. To explore the clinical viability of CAR-NK cells for the treatment of metastatic melanoma, AXL-specific CAR-NK cells were generated by transfecting NK cells obtained from NK cell lines. Preliminary data from a cytotoxicity assay indicated that the cytotoxicity of CAR-NK92-MI cells against AXL-positive melanoma cell lines was significantly stronger (up to a 10-fold difference) than the corresponding parental cells. Further in vitro characterization of this CAR-NK cell line and other CAR-NK cell lines, as well as in vivo evaluation of their efficacy in a mouse xenograft model of melanoma metastasis, is underway.Citation Format: Winston Hibler, Glenn Merlino, Yan Lin Yu. Characterization of anti-AXL CAR-NK cell therapy for the treatment of melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1337.

Introduction: Chronic kidney disease (CKD) involves a progressive loss of renal function and is characterized by chronic oxidative stress and kidney fibrosis. Tetrahydrocurcumin (THCu), a metabolite of curcumin, may possess antioxidant benefits in CKD. This study evaluated the transcriptomic changes and therapeutic potential of THCu against kidney damage and fibrosis in the 5/6 nephrectomy rat CKD model. Methods: Adult female Sprague–Dawley rats were randomized into CKD groups and three THCu doses were tested (100, 300 and 500 mg/kg). A liposomal formulation of THCu was given twice daily via oral gavage for 4 weeks. Serum creatinine and proteinuria were measured, and kidney fibrosis was assessed on histology. Kidney lysates were processed for total RNA sequencing to analyze differential gene expression in the experimental groups. The data were screened for outliers prior to ANOVA and correlation analyses. Results: In the untreated CKD group, serum creatinine and proteinuria were increased compared to control animals. Transcriptomic profiling revealed that untreated CKD animals exhibited marked upregulation across three key gene categories: immune cell activation, kidney injury and fibrosis, and inflammation and oxidative stress. THCu treatment mitigated these pathways by which there was downregulation of markers of immune cell activation as well as the kidney injury marker Kim1, while the fibrosis markers Col1a1 and Col3a1 were decreased to expression levels similar to non-CKD control animals. Furthermore, the highest dose of THCu at 500 mg/kg triggered a cellular detoxification and metabolic clearance response, with highly significant upregulation of Abcb11 and Gls2. Antioxidant benefit was evidenced by upregulation of Gpx1 in the high-dose THCu group compared to the untreated CKD group. Pathway enrichment analysis demonstrated that the high-dose THCu group restored key metabolic and signaling pathways disrupted in renal fibrosis, including small and organic solute metabolism, fatty acid oxidation, lipid biosynthesis, and peptide hormone response. Furthermore, the treatment upregulated essential anion and organic solute transport functions. Proteinuria was reduced with THCu therapy; however, serum creatinine and urine creatinine clearance were not significantly modified in comparison to untreated CKD rats. Conclusions: Oral THCu therapy demonstrated promising transcriptional changes in antioxidant and anti-fibrotic pathways in a rat CKD model. Confirmatory protein-level studies are needed to clarify benefits on kidney function.