肿瘤微环境的酶促重塑增强抗 CEACAM5 CAR-T 细胞对结直肠癌的疗效

Chimeric antigen receptor (CAR) T-cell therapy has shown unprecedented success in haematological cancers but faces challenges in solid tumours. Although carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) is differentially expressed in many solid tumours, anti-CEACAM5 CAR T-cells are ineffective.

Here, we have studied the interaction of CEACAM5 targeting primary CAR T-cells with colorectal cancer (CRC) cells using fluorescence microscopy.

We found that CRC cells' glycocalyx is much thicker than that of the CAR T cell causing delayed activation. Oscillating calcium fluxes, indicative of non-sustained CAR T cell activation, are observed when CAR T cells interacted with CRC cells, which increased with increasing cell-seeding time. Significant reduction in cytotoxicity is observed on going from early to longer-seeded CRC monolayers. Imaging revealed that this effect correlated with a progressive loss of accessible CEACAM5 antigen on the CRC cell surface, possibly due to their sequestration in the intercellular junction, rendering CAR T cell engagement less effective.

Local proteolytic treatment with trypsin to disrupt the CRC cell monolayer, using a micropipette, increased CEACAM5 availability, decreased glycocalyx thickness, and restored sustained CAR T cell calcium fluxes. Similar enhanced interaction is observed after treatment of CRC cell monolayer with hyaluronidase, approved for use in humans. Enzymatic treatment significantly enhanced CAR T cell-mediated cytotoxicity and increased the percentage of TNF- -secreting CAR T cells.

We observed limited availability of CEACAM5 on human colorectal cancer tissues, whereas treatment with trypsin or hyaluronidase increased accessibility.

Our results reveal why CAR T cells targeting CEACAM5 are ineffective and suggest possible routes to improved therapy for CRC.