Combination therapy of an anticancer drug with the FNIII14 peptide of fibronectin effectively overcomes cell adhesion-mediated drug resistance of acute myelogenous leukemia

We investigated whether FNIII14, a 22-mer peptide derived from fibronectin (FN) that potently impairs interaction of FN with beta 1-integrin, could overcome cell adhesion-mediated drug resistance (CAM-DR) induced by very late antigen (VLA)-4-to-FN interaction in acute myelogenous leukemia (AML). Two AML cell lines, U937 cells and HL-60 cells, and fresh leukemic cells from six AML patients with high alpha 4-integrin expression exhibited CAM-DR to cytosine arabinoside (Ara C) through VLA-4-to-FN interaction, while fresh leukemic cells from two AML patients with low a4-integrin expression did not display CAM-DR to Ara C. FNIII14 impaired VLA-4-to-FN interaction and restored sensitivity to Ara C in the CAM-DR leukemic cells. In these CAM-DR leukemic cells, upregulation of Bcl-2, which was induced through the focal adhesion kinase/Akt signal pathway upon VLA-4-to-FN interaction, was inhibited by FNIII14 treatment. In a mouse model of minimal residual disease (MRD) in bone marrow, 100% survival was achieved by combining FNIII14 with Ara C, whereas Ara C alone prolonged survival only slightly. The myelosuppression induced by Ara C was not augmented by the combination of FNIII14 in mouse experiments. Thus, the combination of anticancer drugs and FNIII14 holds promise to eradicate MRD in bone marrow after chemotherapy.