Figure 4. Regulation of MM by mouse neutrophils.

(A–C) CD11b⁺Gr1⁺ MDSC were isolated from BM of MM DP42-bearing mice 12 days after tumor cell inoculation; CD11b⁺Gr1⁺ cells were isolated from BM of tumor-free mice. (A,B) Mouse DP42 (A) or ATLN (B) cells were cultured overnight with or without CD11b⁺Gr1⁺ cells or MDSCs (ratio 1:5) followed by 24h treatment with doxorubicin or melphalan and detection of apoptosis. (C) MM DP42 cells were cultured with or without myeloid cells in indicated ratios overnight followed by 24h treatment with doxorubicin and detection of apoptosis. (D) CD11b⁺Ly6G⁺Ly6C^low neutrophils were isolated from BM of tumor-free mice and CD11b⁺Ly6G⁺Ly6C^low PMN-MDSCs were isolated from BM of MM DP42-bearing mice. These myeloid cells were cultured with DP42 cells overnight. Cells were then treated with doxorubicin followed by detection of apoptosis. Each experiment was performed independently at least 3 times and the combined results are shown. (E) DP42 cells were cultured with or without lymphocytes overnight followed by 24h treatment with doxorubicin and detection of apoptosis.