Engineering of CD19-Specific Chimeric Antigen Receptor T Cells with the Integrin CD103 Results in Augmented Therapeutic Efficacy Against Human Lymphoma in a Preclinical Model

Whether tumor-reactive T cells can infiltrate into the tumor to execute effector function is essential for controlling tumor growth. CD103 is an integrin protein (αE) that binds integrin β₇ to form the heterodimeric integrin complex αEβ₇. CD103 is important for T cell retention in peripheral tissues by interacting with E-cadherin and a promising prognosis biomarker for assessment of tumor-reactive T cells infiltrating in the tumor from various types of cancer, such as lung cancer, ovarian cancer and cervical cancers. However, CD103 is not expressed on the surface of circulating peripheral blood T cells that are genetically modified to express a chimeric antigen receptor (CAR) for adoptive T cell therapy. Whether CD103 expression on the surface of tumor-reactive CAR T cells is functionally important for their anti-tumor activity has not been previously determined. Using a preclinical model of human lymphoma expressing E-cadherin, we demonstrate that engineering of CD19-specific human CAR T cells with CD103 significantly improves their therapeutic effects on eliminating pre-established human lymphoma in immune deficient NSG mice (NOD.scid.Il2Rγcnull). We synthesized a codon optimized CD19-specific CAR containing 4-1BB and CD3zeta intracellular signaling domains (named CD19-BBz-CAR), cloned it into lentiviral vector and infected human T cells. As expected, the resultant human CD19-BBz-CAR T cells possessed potent capacity to cure human B cell leukemia in NSG mice that had been intravenously inoculated with Raji leukemic/lymphoma cells. Notably, while approximately 10% of non-CAR T cells produced high levels of CD103 from these NSG mice, CD19-BBz-CAR T cells failed to upregulate CD103, suggesting that the expression of CD19-BBz-CAR inhibits the induction of CD103 in vivo. Ex vivo assay confirmed that CD19-BBz-CAR caused dose-dependent decrease of CD103 expression in human T cells cultured in the presence of TGF-β1. This effect was mediated by the expression of costimulatory molecule 41BB, which is known essential for sustaining CD19-BBz-CAR T cells in vivo. To circumvent the repression effect of 41BB on induction of CD103, we incorporated the gene encoding integrin αE into the CAR structure to generate CD103-CD19-BBz-CAR T cells. Intriguingly, as compared to conventional CD19-BBz-CAR T cells, CD103-CD19-BBz-CAR T cells expressed high levels of CD62L and CD45RA, which resemble less differentiated T cells, produced higher levels of IL-2, which is crucial for promoting T cell expansion and function, and underwent greater expansion in cultures. Upon adoptive transfer into NSG mice that had subcutaneous human Raji lymphoma, CD103-engineering of CD19-BBz-CAR T cells dramatically decreased the distal metastasis of lymphoma, increased the infiltration of CAR T cells into the solid lymphoma, and improved the in vivo persistence of tumor-reactive CAR T cells. As a result, transfer of CD103-CD19-BBz-CAR T cells significantly increased overall survival rate of lymphoma mice compared to conventional CD19-BBz-CAR T cells (40% versus 10%, p<0.05). Our findings suggest that engineering tumor-reactive T cell with CD103 may represent a novel strategy to improve their anti-tumor efficacy. Moreover, this newly established CD103-CAR structure may have broad implication in the solid tumor treatment.