seryl-isoleucyl-lysyl-valyl-alanyl-valinamide and Prostatic-Neoplasms

Effective gene therapy for disseminated metastatic cancer is currently impossible because of poor delivery of vector to target sites. Modification of viral vectors to target advanced cancer has long been a challenge. In this study, we aimed to redirect adenovirus tropism to infect prostate cancer cells via alpha6beta1 integrins, whose expression is upregulated during prostate cancer progression. To ablate normal mechanisms of infection and provide a framework for attachment of targeting ligands, viruses were non-genetically modified with pHPMA-ONp polymer. Addition of polymer-coated virus to prostate cells showed significantly reduced transgene expression compared with unmodified virus. To restore infectivity, an alpha6-integrin binding peptide (-SIKVAV-) derived from laminin was incorporated onto the surface of the polymer-coated viruses. Photon correlation spectroscopic analysis revealed a small increase in the mean diameter of the particles following retargeting. Addition of -SIKVAV- peptide restored virus infectivity of PC-3 cells in a ligand concentration-dependent manner that was significantly improved following removal of unincorporated polymer and peptide. Competition assays using cells preincubated with Ad5 fiber protein or free -SIKVAV- peptide confirmed that entry of retargeted viruses was mediated via the incorporated ligand. Application of retargeted viruses to a panel of human cell lines revealed varying levels of transduction efficiency. Flow cytometric analysis of cells using anti-alpha6 integrin and anti-beta1 integrin antibodies demonstrated that for prostate cells, greater transduction efficiency correlated with higher levels of expression of both integrin subunits. Furthermore with the exception of LNCaP cells, increased alpha6beta1 integrin expression correlated with advanced disease. Intravenous administration of retargeted viruses to tumor-bearing mice resulted in slower plasma clearance and greatly reduced liver tropism, and hence toxicity compared with unmodified virus, while maintaining reporter gene expression in the tumor. The data suggest that YESIKVAVS-retargeted viruses have potential for systemic delivery for the treatment of metastatic disease.

Topics: Adenoviridae; Cell Line, Tumor; Genetic Therapy; Genetic Vectors; Humans; Integrin alpha6; Laminin; Male; Oligopeptides; Polymers; Prostatic Neoplasms; Transduction, Genetic

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. These anti-metastatic and anti-tumoral effects of PCK3145 are partially explained by the in-vivo and in-vitro decrease in matrix metalloproteinase (MMP)-9 extracellular levels through as yet unidentified molecular mechanisms of action. Gelatin zymography and immunoblots were used to monitor the levels of secreted MMP-9 from HT-1080 cells. Flow cytometry was used to monitor HT-1080 cell surface binding of FITC-labeled PCK3145 and biotin-labeled laminin. PCK3145-coated cell culture dishes were used to monitor cell adhesion. HT-1080 cell lysates were used for immunoblotting of HuR, extracellular signal-regulated protein kinase (ERK) and phospho-ERK. Total RNA was isolated and RT-PCR used to monitor HuR gene expression. We found that PCK3145 bound to the HT-1080 cell surface and that this binding rapidly triggered ERK phosphorylation that, ultimately, led to a reduction of secreted MMP-9. Laminin inhibited both cell surface binding and ERK phosphorylation by PCK3145. Overexpression of the 67-kDa laminin receptor led to an increased binding of the cells to PCK3145. HuR, a protein that can bind to and stabilize MMP-9 mRNA, was found to be downregulated by PCK3145. The mitogen-activated protein kinase/ERK (MEK) inhibitor PD98059 as well as native laminin and SIKVAV laminin-derived peptide prevented that downregulation. Our data suggest that PCK3145 rapidly triggers intracellular signaling through cell surface laminin receptors. This leads to decreased HuR expression and subsequent destabilization of MMP-9 transcripts. This is the first molecular evidence demonstrating the intracellular signaling and anti-metastatic mechanism of action of PCK3145 that leads to the inhibition of MMP-9 secretion.

Topics: Antigens, Surface; Bone Neoplasms; Cell Line, Tumor; ELAV Proteins; ELAV-Like Protein 1; Flavonoids; Humans; Laminin; Male; Matrix Metalloproteinase 9; Matrix Metalloproteinase Inhibitors; Oligopeptides; Peptide Fragments; Prostatic Neoplasms; Prostatic Secretory Proteins; Protein Binding; Protein Serine-Threonine Kinases; Receptors, Laminin; RNA-Binding Proteins; Signal Transduction