CD14+HLA-DR−/low MDSC have been reported to contribute to tumor progression and/or therapy resistance, and increased abundance of these cells has been described in the PB and/or tumor tissues from hepatocellular carcinoma (HCC), melanoma, lung cancer, head and neck SCC (HNSCC), esophageal SCC and prostate cancer [15–23], and in several cancer types, has shown correlation with poor prognosis of cancer patients [15, 20, 22]. The gene discussed is CD14; the disease is head and neck squamous cell carcinoma.