PGRN inhibits CD8 + T cell recruitment and promotes breast cancer progression by up-regulating ICAM-1 on TAM.

BACKGROUND: Tumor microenvironment actually reduces antitumor effect against the immune attack by exclusion of CD8+ T cells. Progranulin (PGRN) is a multifunctional growth factor with significant pathological effects in multiple tumors; however, its role in immunity evasion of breast cancer (BCa) is not completely understood.

METHODS: We depleted GRN (PGRN gene) genetically in mice or specifically in PY8119 murine BCa cell line, and mouse models of orthotopic or subcutaneous transplantation were used. Chimeric mice-deficient of PGRN (Grn-/- ) in bone marrow (BM) compartment was also generated. Association of PGRN expression with chemokine production or BCa development was investigated by histological and immunological assays.

RESULTS: We found PGRN was involved in exhaustion of cytotoxic CD8+ T cell in BCa with the increasing expressions of M2 markers and intercellular cell adhesion molecule-1 (ICAM-1) on macrophages. Specifically, ablation of PGRN in PY8119 cells reduced tumor burden, accompanied by the infiltrating of cytotoxic CD8+ T cells into tumor nests. Moreover, our result revealed that blockade of PD-1 in PGRN-depleted tumors exhibited better antitumor effect in vivo and significantly decreased tumor burden.

CONCLUSION: These findings suggest that inhibition of PGRN may act as a potential immune-therapeutic strategy by recovering infiltration of CD8+ T cell in BCa tissue and thereby enhancing the response to anti-PD-1 therapy.