Phase IB study of 25-hydroxyvitamin D-3 treatment to diminish suppressor cells in head and neck cancer patients

Patients with head and neck squamous cell carcinoma (HNSCC) have profound i mmune defects. These defects are associated with a poor prognosis and are m ediated, in part, by an increased number of immune inhibitory CD34(+) proge nitor cells in their peripheral blood and tumor. The CD34(+) cells suppress autologous T-cell functions. Our prior work had shown that the differentia tion inducer 1 alpha ,25-dihydroxyvitamin D-3 could drive the differentiati on of CD34(+) cells isolated from HNSCC patients into dendritic cells. A ph ase IB clinical trial was initiated with HNSCC patients to determine if 25- hydroxyvitamin D-3 treatment could diminish CD34(+) cell levels and improve immune function. Six patients per treatment group were orally administered 20 or 40 mug/day 25-hydroxyvitamin D-3 for six weeks. Peripheral blood was collected at 0, 1, 2, 4, 6, and 8 weeks, and assessed for markers of immun e activity. Although no clinical responses were observed, results of these pilot studies showed that 25-hydroxyvitamin D-3 reduced the presence of imm une suppressive CD34(+) cells and improved immune competence of HNSCC patie nts. (C) American Society for Histocompatibility and Immunogenetics, 2001. Published by Elsevier Science Inc.