Intrahepatic CD69 + v 1 T cells re-circulate in the blood of patients with metastatic colorectal cancer and limit tumor progression

Background More than 50% of all patients with colorectal cancer (CRC) develop liver metastases (CLM), a clinical condition characterized by poor prognosis and lack of reliable prognostic markers. V 1 cells are a subset of tissue-resident gamma delta (I 3) T lymphocytes endowed with a broad array of antitumor functions and showing a natural high tropism for the liver. However, little is known about their impact in the clinical outcomes of CLM. Methods We isolated human I 3δT cells from peripheral blood (PB) and peritumoral (PT) tissue of 93 patients undergone surgical procedures to remove CLM. The phenotype of freshly purified I 3δT cells was assessed by multiparametric flow cytometry, the transcriptional profiles by single cell RNA-sequencing, the functional annotations by Gene Ontology enrichment analyses and the clonotype by I 3δT cell receptor (TCR)-sequencing. Results The microenvironment of CLM is characterized by a heterogeneous immune infiltrate comprising different subsets of I 3δtumor-infiltrating lymphocytes (TILs) able to egress the liver and re-circulate in PB. V 1 T cells represent the largest population of I 3δTILs within the PT compartment of CLM that is greatly enriched in V 1 T effector (T EF) cells expressing constitutive high levels of CD69. These V 1 CD69 + TILs express a distinct phenotype and transcriptional signature, show high antitumor potential and correlate with better patient clinical outcomes in terms of lower numbers of liver metastatic lesions and longer overall survival (OS). Moreover, intrahepatic CD69 + V 1 TILs can egress CLM tissue to re-circulate in PB, where they retain a phenotype, transcriptional signature and TCR clonal repertoires resembling their liver origin. Importantly, even the increased frequencies of the CD69 + terminally differentiated (T EMRA) V 1 cells in PB of patients with CLM significantly correlate with longer OS. The positive prognostic score of high frequencies of CD69 + T EMRA V 1 cells in PB is independent from the neoadjuvant chemotherapy and immunotherapy regimens administered to patients with CLM prior surgery. Conclusions The enrichment of tissue-resident CD69 + V 1 T EMRA cells re-circulating at high frequencies in PB of patients with CLM limits tumor progression and represents a new important clinical tool to either predict the natural history of CLM or develop alternative therapeutic protocols of cellular therapies.