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

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: 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. K5 PDX tumor cells or K7 PDX tumor cells at kidney 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 tumor administration.