TREM2 knockdown improves the therapeutic effect of PD-1 blockade in hepatocellular carcinoma

Triggering receptor expressed on myeloid cells 2 (TREM2), which is typically expressed in microglia/macrophage, is a crucial receptor modulating the activation of immune cells. Recent single-cell RNA sequencing studies of the tumor microenvironment (TME) have found that TREM2 is highly expressed in several subgroups of tumor-associated macrophages (TAMs) with immunosuppressive activity. TREM2 knockout mice are more resistant to tumor growth than wild-type mice in multiple mice tumor models. But the function of TREM2 expression in TAMs of hepatocellular carcinoma (HCC) is still unclear. Here we used a self-complementary adeno-associated virus (scAAV) with macrophage tropism to efficiently knockdown TREM2 in TAMs in vivo and found that the growth of hepatocellular carcinoma was suppressed by TREM2 knockdown. Moreover, we found that TREM2 knockdown remodeled TAMs to an immune-stimulating status and enhanced the therapeutic effect of PD-1 immune-checkpoint blockade in HCC.