Figure 5
Myeloid derived suppressor cells associated with advanced tumor burden are responsible for blunting immunotherapy potency. (A) Flow cytometry of splenocyte populations obtained from (i) tumor naïve mice, (ii) mice bearing large, establish TC1 tumors or (iii) mice 3 days status post partial resection. Top-panel — Myeloid derived suppressor cells (CD11b+ Gr1+) were compared. MDSCs increased with tumor growth, but were found to be eliminated following cytoreduction surgery. Middle-panel— Granulocytic MDSCs (Ly6GhiLy6Cmod) were also compared; and increased with tumor growth, but were found to be eliminated following cytoreduction surgery. Bottom-panel— Splenic macrophages (Cd11b+F4/80+) increased with tumor growth were found to be eliminated following cytoreduction surgery. (B) Immunosuppressive cytokines (G-CSF and IL-6) in mouse serum at various times as measured by ELISA. Maximum levels were found in large tumors; surgical cytoreduction significantly decreased these cytokines to normal levels. * Represents a p < 0.05, ** represents a p < 0.01.