Treatment of CEA-positive solid tumors with anti-CEA chimeric antigen receptor T-cells in CEA transgenic mice

Abstract

Abstract Chimeric antigen receptors (CARs) combine specificity of antibody to target antigen on cancer cells with the potent cytotoxic activity of T-cells without the need for MHC recognition. Chimeric antigen receptor (CAR) T-cells that were designed to express the single chain variable fragment binding domain of human anti-CEA antibody BW431/26 on mouse splenocytes were able to reduce CEA-expressing pancreatic adenocarcinoma tumor in CEA-transgenic (CEAtg) mice without significant off-target effects (Chmielewski et al., 2012). In this study, an anti-CEA CAR construct derived from murine anti-CEA antibody (T84.66) expressed on human T-cells targeted CEA+ colon carcinoma cells (LS174T/CEA and MC38CEA) with high specificity in vitro. When co-incubated with CEA-positive or CEA-negative mouse cancer cells, anti-CEA CAR expressed on mouse T-cells specifically targeted CEA-positive cancer cells in vitro. Compared to mock T-cells control, anti-CEA CAR T-cells injected intravenously delayed subcutaneous MC38CEA tumor growth in CEAtg mice. Lymphodepletion via cyclophosphamide injected before anti-CEA T-cells therapy further delayed subcutaneous MC38CEA tumor growth in CEAtg mice. To improve the therapeutic potential of anti-CEA CAR T-cells, IL2 was conjugated to a humanized anti-CEA antibody to form an immunocytokine (ICK). The ICK was injected interperitoneally after anti-CEA CAR T-cells into lymphodepleted CEAtg mice. A single injection of the ICK delayed subcutaneous MC38CEA tumor growth even further. Four injections of ICK after anti-CEA CAR T-cells eradicated subcutaneous MC38CEA tumors. These data show the therapeutic potential of anti-CEA CAR T-cells to target CEA-positive tumors.