ABSTRACT
<p><b>OBJECTIVE</b>To explore the presence, frequency and clinical value of myeloid-derived suppressor cells (MDSCs) in peripheral blood of patients with small cell lung cancer (SCLC).</p><p><b>METHODS</b>Flow 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.</p><p><b>RESULTS</b>MDSCs 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).</p><p><b>CONCLUSIONS</b>The 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.</p>