ABSTRACT
Despite the use of targeted therapy, chronic myelogenous leukemia [CML] currently remains incurable with drug therapy, with patients requiring life-long treatment. Developing either a vaccine to prevent the disease or another novel drug to specifically target and eradicate the CML cell will require the identification of CML-associated cell-surface markers and molecules that can bind specifically to the cell surface. In an attempt to discover peptides that bind specifically to cells in the early chronic phase of the disease, we used phage-display technology to identify heptapeptides that bind specifically to the surface of BCR/ABL-expressing fibroblasts. An in vitro system using NIH3T3 stably transfected with pGD210 [BCR/ABL] was used as a model for the chronic phase of the disease. The cells were panned using a linear heptapeptide phage library [Ph.D 7.0] in a negative/positive panning strategy with NIH3T3 containing only the plasmid vector as the wild type control. We identified four novel peptides that were enriched through this technique. These peptides contained either multiple proline residues or serine/threonine-proline pairs and showed a confirmed binding preference for BCR/ABL+ fibroblasts. The peptide Y-R-A-P-W-P-P also showed a binding affinity for granulocytes from untreated CML patients. We have identified several novel peptides that can be used in future studies to identify specific CML cell-surface antigens or provide a novel drug-delivery mechanism.
ABSTRACT
Research has implied that the immune system plays a role in the pathogenesis of MDS and that T-cells are reacting to tumour antigen present on the surface of the malignant cells. This could imply that the immune system could be utilized to generate immune based therapy. The aim of this pilot study was to examine the feasibility of studying this further by analysing the interaction of dendritic cells with T-cells in a small cohort of MDS patients. Dendritic cells were generated in 6 MDS patients and 9 controls by culturing monocytes with GMCSF and IL-4. After activation with LPS and TNFalpha, the dendritic cells were analyzed for expression of co-stimulatory and activation antigens. Thereafter, they were co-cultured with T-cells and the T-cell response was examined by measuring the % change in expression of the activation antigen CD69. MDS MoDC had reduced expression of HLA-DR [p=0.006], CD11c [p=0.0004], CD80 [p=0.03] and CD86 [p=0.003], while resting T-cells from MDS patients had higher expression of the activation antigen CD69 on all subsets. The % change in CD69 expression increased significantly for both the control and MDS T-cells after co-culture with allogeneic dendritic cells, however this change was lower in the MDS group. Despite the increased CD69 expression prior to culture, MDS MoDC significantly up-regulated CD69 expression on autologous T-cells to values that were statistically higher than control cells. This initial study suggests that the T-cells in MDS are able to respond to dendritic cells and are therefore probably not part of the malignant clone. It further implies that the dendritic cell population could be capable of presenting antigen and initiating an immune response and therefore further study is both feasible and warranted