OBJECTIVETo explore the presence, frequency and clinical value of myeloid-derived suppressor cells (MDSCs) in peripheral blood of patients with small cell lung cancer (SCLC).

METHODSFlow cytometry using antibodies against CD11b, CD33, CD14 or HLA-DR was conducted to explore the unique cell surface markers of MDSCs and statistical analysis was performed to explore the correlation of MDSCs and clinical features.

RESULTSMDSCs were present in 36 patients with SCLC and uniquely marked by CD11b and CD33-positive, but HLA-DR-negative on cell surfaces and possessed mononuclear phenotype. The levels of CD11b(+)CD33(+)HLA-DR(-)cells (MDSCs) in the SCLC patients and healthy controls were (26.87 ± 6.87)% and (11.04 ± 3.76)%, respectively, with a statistically significant difference (P < 0.001). MDSCs level was significantly associated with clinical stage and tumor distant metastasis (P < 0.05) , but not with age, sex, smoking status and performance status. The later was the clinical stage, the higher was the MDSCs level (r = 0.665, P < 0.001). The level of MDSCs was higher in SCLC patients with distant metastasis than in those without metastasis (r = 0.489, P = 0.003). The level of MDSCs was higher before treatment than after treatment and the difference was statistically significant (P = 0.003).

CONCLUSIONSThe results of our study demonstrate the existence of MDSCs in SCLC patients and the MDSCs level is associated with SCLC stage, metastasis and treatments. MDSCs might be a novel biomarker for early diagnosis and prognosis for SCLC patients.