Significance of myeloid-derived suppressor cells in squamous cell carcinoma of the head and neck.

Abstract

6070 Background: Patients with advanced stage squamous cell carcinoma of the head and neck (SCCHN) have less than 50% 5-year survival rate Human papillomavirus (HPV)-associated SCCHN in oropharyngeal sites have shown better prognosis. Little is known about the role of myeloid-derived suppressor cells (MDSCs) in immune suppression or tumor progression in the setting of SCCHN. Our objective is to evaluate the clinical significance of MDSCs in subjects with SCCHN, HPV-positivity, and advanced cancer staging. Methods: Thirty-three subjects with SCCHN and 10 healthy donors were enrolled in this prospective cohort study. Fresh blood was collected at the time of surgical resection of SCCHN in a tertiary academic center between August 2011 and January 2013. Peripheral blood mononuclear cells (PBMCs) were obtained using Ficoll Hypaque. MDSCs were immunophenotyped as CD14-CD33+CD11b+by flow cytometry. HPV status was determined by in situ hybridization Frequencies of MDSCs in blood of different cohorts were evaluated. Results: Thirty-three subjects (ages 34-83 years, 25 males) with SCCHN were enrolled. Increased numbers of CD14-CD33+CD11b+ cells of total leukocytes were found in HPV-associated SCCHN (median 26.6%, n=11) compared to HPV-negative SCCHN (16.3%, n=19). Interestingly, 3 subjects who previously had HPV-positive SCCHN but with no evidence of disease had 6.24% (n=3) CD14-CD33+CD11b+cells of leukocytes which was higher than healthy donors (3.55%, n=10). Subjects with advanced cancer stages (III-IV) had higher levels of MDSCs (26%, n=19) compared to those with a lower grade (I-II, 15.5%, n=11) regardless of HPV status. Three subjects were lost to follow up. Of the remaining subjects, the overall median follow time was 3 months and subjects who were found to have recurrence, regional or local metastasis had higher frequencies of MDSCs in the blood (26.35%, n=4) compared to those with no evidence of disease (18.5%, n=26) at the time of surgery. Conclusions: This study suggests there is an accumulation of MDSCs in peripheral blood of patients with SCCHN, particularly in HPV-associated SCCHN. Further, increased levels of MDSCs in the peripheral blood are related to more advance cancer stage and poor clinical outcomes.