Genetic alterations leading to the downregulation of EpCAM expression on gastric cancer cells represent a primary obstacle to the success of CAR T cell therapy. EpCAM, a transmembrane glycoprotein, is often targeted for internalization and degradation upon CAR T cell recognition. Genetic mutations affecting the EpCAM gene or alterations in regulatory elements can result in reduced or absent EpCAM expression, rendering CAR T cells ineffective. Strategies aimed at overcoming EpCAM downregulation include the identification of alternative target antigens or the development of dualtargeting CAR T cell constructs. Intra-tumoral heterogeneity poses a significant challenge, with distinct subpopulations of gastric cancer cells exhibiting diverse antigenic profiles. Genetic alterations leading to the emergence of subclones with reduced or absent EpCAM expression can limit the efficacy of CAR T cells. Comprehensive profiling of tumor heterogeneity and the incorporation of multi-antigen targeting strategies are essential for addressing this challenge. Furthermore, advances in single-cell sequencing technologies can provide insights into the dynamic changes in antigen expression within the tumor microenvironment [2].
The immunosuppressive nature of the tumor microenvironment poses a formidable barrier to CAR T cell therapy in gastric cancer. Immunosuppressive cells, such as regulatory T cells (T regs) and myeloid-derived suppressor cells (MDSCs), infiltrate the tumor, creating an environment that hampers CAR T cell function. Genetic alterations in signaling pathways regulating immune checkpoints, such as PD-L1 overexpression, contribute to immune evasion. Combining CAR T cell therapy with immune checkpoint inhibitors or modulators of the tumor microenvironment may enhance therapeutic outcomes. The presence of dense stromal components and an aberrant extracellular matrix in gastric tumors can impede CAR T cell infiltration and function. Genetic alterations affecting the composition of the extracellular matrix or promoting fibrosis create physical barriers, limiting the access of CAR T cells to cancer cells. Strategies to modify the tumor microenvironment, including stromaltargeted therapies or extracellular matrix-degrading enzymes, may enhance CAR T cell penetration and improve treatment outcomes [3].