Sensitive CAR T cells redefine targetable CD70 expression in solid tumors [RNA-seq RCC]

Overcoming tumor antigen heterogeneity in solid tumors is a major challenge for cancer immunotherapies including chimeric antigen receptor (CAR) T cells. Unlike CD19 for B-cell malignancies, no target with pan-cellular expression in solid tumors and absence in normal vital cells has been identified. CD70 is a potential candidate, confined to immune cell subsets and aberrantly expressed in many solid tumors, albeit heterogeneously. We find that CD70 expression in heterogeneous tumors is not binary but ranges from high to very low, appearing negative. We show that CD70-heterogeneous tumors are efficiently eliminated by highly sensitive CD70 receptors where prototypic CAR T cells fail. We further identify an epigenetic signature that predicts targetable expression. These findings provide a potential strategy to treat a broad range of solid tumors. Overall design: Mice bearing ccRCC tumor at both the kidney and lung site within the same mouse were used for bulk ATAC and RNA sequencing. For the ccRCC kidney model, 5×10E5 FFLuc-Tdtomato K5 or K7 ccRCC cells were injected into the renal subcapsule of male NOD.Cg-Prkdc scid IL2rg tm1Wjl/SzJ (NSG, Jackson Laboratory) mice, aged 6-8 weeks. For the ccRCC lung model, 7.5×105 FFLuc-Tdtomato K5 or K7 ccRCC cells were administered via tail vein injection into the same NSG mouse bearing tumor at the kidney site. K5 PDX tumor cells or K7 PDX tumor cells at kidney site and lung site were digested into single cell suspensions using the Tumor Dissociation Kit, human (Miltenyi Biotec) according to the manufacturer's instructions and isolated by fluorescence-activated cell sorting 15 days post orthotopic kidney tumor implantation. Live cells were sorted for TdtomatoPOS. CD70LO and CD70HI tumor cells from kidney site or lung site were isolated by FACs, denoted as day 0 of isolation, d0. Isolated CD70LO and CD70HI tumor cells from kidney site, and CD70HI tumor cells from lung site were then cultured for 8 days. CD70 transcript expression and chromatin accessibility was assessed for each biological replicate in CD70LO and CD70HI tumor cells at d0 of isolation, d2 and d8 of culture.