Epitope-targeted cytotoxic T cells mediate lineage-specific antitumor efficacy induced by the cancer mucosa antigen GUCY2C

Abstract

<p id="P1">Guanylyl cyclase C (GUCY2C) is the index cancer mucosa antigen, an emerging class of immunotherapeutic targets for prevention of recurrent metastases originating in visceral epithelia. GUCY2C is an auto-antigen principally expressed by intestinal epithelium, and universally by primary and metastatic colorectal tumors. Immunization with adenovirus expressing the structurally unique GUCY2C extracellular domain (GUCY2C _ECD; Ad5-GUCY2C) produces prophylactic and therapeutic protection against GUCY2C-expressing colon cancer metastases in mice, without collateral autoimmunity. GUCY2C antitumor efficacy is mediated by a unique immunological mechanism involving lineage-specific induction of antigen-targeted CD8 ⁺ T cells, without CD4 ⁺ T cells or B cells. Here, the unusual lineage-specificity of this response was explored by integrating high-throughput peptide screening and bioinformatics, revealing the role for GUCY2C-directed CD8 ⁺ T cells targeting specific epitopes in anti-tumor efficacy. In BALB/c mice vaccinated with Ad5-GUCY2C, CD8 ⁺ T cells recognize the dominant GUCY2C _254-262 epitope in the context of H-2K ^d, driving critical effector functions including interferon gamma secretion, cytolysis <i>ex vivo</i> and <i>in vivo</i>, and antitumor efficacy. The ability of GUCY2C to induce lineage-specific responses targeted to cytotoxic CD8 ⁺ T cells recognizing a single epitope mediating anti-tumor efficacy without autoimmunity highlights the immediate translational potential of cancer mucosa antigen-based vaccines for preventing metastases of mucosa-derived cancers. </p>