FDC Like Cell Line HK With IL-2, IL-4 and OX40 Ligand Supports The Growth Of ATLL Cells

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive neoplasm derived from CD4+ T-cells with HTLV-I infection, and its mechanisms of tumorigenesis still remain to be elucidated. The fact that tumor cells rarely proliferate in vitro is one of the most important problems to be solved. The establishment of cell line from ATLL patient samples has been difficult even in the presence of interleukins. Previously we established one cell line (HU-ATTAK) from acute or lymphoma types of 10 ATLL cases which did not proliferate in the presence of IL-2 and/or IL-4. HU-ATTAK is critically dependent on IL-2 and human umbilical cord vein endothelial cells (HUVEC) as feeder cells. In HU-ATTAK, adding anti-OX40 ligand antibody into the culture system completely inhibited its proliferation. So, OX40 ligand as well as L-2 and/or IL-4 is suggested be necessary for the proliferation of ATLL cells, and feeder cells may also confer the favorable environment. As the substitute of HUVEC, follicular dendritic cell like cell line HK which expresses OX40 ligand was used by introducing human OX40 ligand cDNA (HK-OX40L). When 9 ATLL patient samples were co-cultured with HK-OX40L in the presence of L-2 and/or IL-4, two ATLL cells proliferate vigorously only in the presence of both IL-2 and IL-4 simultaneously. These cell lines were confirmed to be derived from original tumor cells by array CGH analysis, and continued the growth for more than a year. Depletion of IL-2 and IL-4 made these cell lines stop growing within 6 days even on HK-OX40L. In the presence of IL-2 and IL-4, the conditions such as HK alone without OX40 ligand or OX40 ligand alone without HK made the cell lines growing for three months at most. In the presence of IL-2 and IL-4 without HK-OX40L, these cell lines vigorously proliferated for more than three months but finally stopped growing. These data suggested that for the growth of these two cell lines, the cell division is dependent on IL-2 and IL-4, and the maintenance of immortalization is dependent on OX40 ligand and HK cells. This culture analysis would provide important factors for cell growth of ATLL which will explore new targets for ATLL treatment. *HK cells are kindly provided by Dr. Young S Choi at Ochsner Cancer Center, New Orleans. Disclosures: No relevant conflicts of interest to declare.