Inhibition of collagen and DNA biosynthesis by a novel amidine analogue of chlorambucil is accompanied by deregulation of β 1-integrin and IGF-I receptor signaling in MDA-MB 231 cells

Abstract

A novel amidine analogue of chlorambucil N-(2-(4-(4-bis(2-chloroethyl)aminophenyl)butyryl)aminoethyl)-5-(4-amidinophenyl)-2-furanecarboxamide hydrochloride (AB 1), and the parent drug were compared for their effects on collagen and DNA synthesis in breast cancer MDA-MB 231 cells. IC 50 values for chlorambucil and its amidine analogue for collagen synthesis were found to be about 44 and 19 μM, respectively. Increased ability of AB 1 to suppress the protein synthesis, compared to chlorambucil, was found to be related to an inhibition of prolidase activity and expression. The phenomena were probably a result of disruption of β 1-integrin and the insulin-like growth factor-I (IGF-I) receptor mediated signaling caused by this compound. Expression of β 1-integrin receptor, as well as focal adhesion kinase pp125 FAK (FAK), growth-factor receptor-bound protein 2 (GRB2), son of sevenless protein 1 (Sos1) and phosphorylated mitogen activated protein kinases (MAPK), extracellular-signal-regulated kinase 1 (ERK 1) and kinase 2 (ERK 2) but not Src and Shc proteins was significantly decreased in cells incubated for 24 h with 10 μM AB 1, compared to controls. Chlorambucil in the same conditions did not evoke any changes in expression of all these signaling proteins, as shown by Western immunoblot analysis. In addition, AB 1 revealed a higher antiproliferative activity than chlorambucil, accompanied by a stronger down-regulation of IGF-I receptor expression. The results were confirmed by [ 3H]thymidine incorporation assay. Incubation of the cells with 10 μM AB 1 for 12 and 24 h contributed to a decrease in DNA synthesis by about 33 and 46% of the control values, respectively, while in case of chlorambucil by about 23 and 29%, respectively. These data suggest that the amidine analogue of chlorambucil (AB 1) disturbs MDA-MB 231 cell metabolism more potently than does the parent drug, chlorambucil. The mechanism of this phenomenon may be due to its stronger suppression of β 1-integrin and IGF-I receptor signaling.