RESUMO
Foxp3-expressing CD25+CD4+ regulatory T cells (Tregs) are abundant in tumor tissues. Here, hypothesizing that tumor Tregs would clonally expand after they are activated by tumor-associated antigens to suppress antitumor immune responses, we performed single-cell analysis on tumor Tregs to characterize them by T cell receptor clonotype and gene-expression profiles. We found that multiclonal Tregs present in tumor tissues predominantly expressed the chemokine receptor CCR8. In mice and humans, CCR8+ Tregs constituted 30 to 80% of tumor Tregs in various cancers and less than 10% of Tregs in other tissues, whereas most tumor-infiltrating conventional T cells (Tconvs) were CCR8- CCR8+ tumor Tregs were highly differentiated and functionally stable. Administration of cell-depleting anti-CCR8 monoclonal antibodies (mAbs) indeed selectively eliminated multiclonal tumor Tregs, leading to cure of established tumors in mice. The treatment resulted in the expansion of CD8+ effector Tconvs, including tumor antigen-specific ones, that were more activated and less exhausted than those induced by PD-1 immune checkpoint blockade. Anti-CCR8 mAb treatment also evoked strong secondary immune responses against the same tumor cell line inoculated several months after tumor eradication, indicating that elimination of tumor-reactive multiclonal Tregs was sufficient to induce memory-type tumor-specific effector Tconvs. Despite induction of such potent tumor immunity, anti-CCR8 mAb treatment elicited minimal autoimmunity in mice, contrasting with systemic Treg depletion, which eradicated tumors but induced severe autoimmune disease. Thus, specific removal of clonally expanding Tregs in tumor tissues for a limited period by cell-depleting anti-CCR8 mAb treatment can generate potent tumor immunity with long-lasting memory and without deleterious autoimmunity.
Assuntos
Memória Imunológica , Neoplasias/metabolismo , Receptores CCR8/metabolismo , Animais , Anticorpos Monoclonais , Biomarcadores Tumorais , Diferenciação Celular , Terapia Baseada em Transplante de Células e Tecidos , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Deleção de Genes , Regulação Neoplásica da Expressão Gênica , Humanos , Camundongos , Receptores CCR8/genética , Linfócitos T ReguladoresRESUMO
BACKGROUND/AIM: Cancer stem cells (CSCs) are considered to be one of the causes of tumor recurrence after chemotherapy. The purpose of our study was to isolate CSCs from human colorectal cancer cell (CRC) lines. MATERIALS AND METHODS: Nine CRC lines were screened based on the expression level of potential CSC markers to identify putative CSCs. Tumor formation capacity in immunodeficient mice was compared with that of their counterparts. Stemness, differentiation potency and sensitivity to 5-fluorouracil (5-FU), in vitro, were also assessed. Microarray analysis was used to characterize the features of the putative CSCs. RESULTS: COLO 201 cells were separated into two populations based on CD44 expression. CD44 positive (CD44+) cells showed significantly higher tumor formation capacity than CD44- cells in immunodeficient mice. CD44+ cells also possessed stemness properties and lower sensitivity to 5-FU in vitro. Moreover, cancer stemness and chemoresistance-related genes were highly up-regulated in CD44+ cells. CONCLUSION: CD44+ COLO 201 cells possessed the features of CSCs; therefore, the present CSC model could serve as a valuable tool to accelerate CSC research.