tigapotide and Neoplasm-Metastasis

PCK3145 is an anti-metastatic synthetic peptide with promising therapeutic efficacy against hormone-refractory prostate cancer. The characterization of the PCK3145 peptide cell surface binding/internalization mechanisms and of the receptors involved remained to be explored.. [(14)C]PCK3145 cell surface binding assays showed rapid and transient kinetic profile, that was inhibited by RGD peptides, laminin, hyaluronan, and type-I collagen. RGD peptides were however unable to inhibit PCK3145 intracellular uptake. Far-Western ligand binding studies enabled the identification of the 37-kDa laminin receptor precursor (37LRP) as a potential ligand for PCK3145. Overexpression of the recombinant 37LRP indeed led to an increase in PCK3145 binding but unexpectedly not to its uptake.. Our data support the implication of laminin receptors in cell surface binding and in transducing PCK3145 anti-metastatic effects, and provide a rational for targeting cancers that express high levels of such laminin receptors.

Topics: Catechin; Cell Communication; Cell Line, Tumor; Collagen Type I; Drug Synergism; Humans; Kinetics; Matrix Metalloproteinase 9; Neoplasm Metastasis; Oligopeptides; Peptide Fragments; Prostatic Secretory Proteins; Protein Precursors; Receptors, Cell Surface; Receptors, Laminin

PCK3145 is a synthetic peptide corresponding to amino acids 31-45 of prostate secretory protein 94, which can reduce experimental skeletal metastases and prostate tumor growth in vivo. Part of its biological action involves the reduction of circulating plasma matrix metalloproteinase (MMP)-9, a crucial mediator in extracellular matrix (ECM) degradation during tumor metastasis and cancer cell invasion. The antimetastatic mechanism of action of PCK3145 is however, not understood.. HT-1080 fibrosarcoma cells were treated with PCK3145, and cell lysates used for immunoblot analysis of small GTPase RhoA and membrane type (MT)1-MMP protein expression. Conditioned media was used to monitor soluble MMP-9 gelatinolytic activity by zymography and protein expression by immunoblotting. RT-PCR was used to assess RhoA, MT1-MMP, MMP-9, RECK, and CD44 gene expression. Flow cytometry was used to monitor cell surface expression of CD44 and of membrane-bound MMP-9. Cell adhesion was performed on different purified ECM proteins, while cell migration was specifically performed on hyaluronic acid (HA).. We found that PCK3145 inhibited HT-1080 cell adhesion onto HA, laminin-1, and type-I collagen suggesting the common implication of the cell surface receptor CD44. In fact, PCK3145 triggered the shedding of CD44 from the cell surface into the conditioned media. PCK3145 also inhibited MMP-9 secretion and binding to the cell surface. This effect was correlated to increased RhoA and MT1-MMP gene and protein expression.. Our data suggest that PCK3145 may antagonize tumor cell metastatic processes by inhibiting both MMP-9 secretion and its potential binding to its cell surface docking receptor CD44. Such mechanism may involve RhoA signaling and increase in MT1-MMP-mediated CD44 shedding. Together with its beneficial effects in clinical trials, this is the first demonstration of PCK3145 acting as a MMP secretion inhibitor.

Topics: Fibrosarcoma; Flow Cytometry; Gene Expression Profiling; Humans; Hyaluronan Receptors; Matrix Metalloproteinase 9; Neoplasm Metastasis; Peptide Fragments; Polyesters; Prostatic Secretory Proteins; Reverse Transcriptase Polymerase Chain Reaction; Tumor Cells, Cultured