| Research Abstract |
Newly synthesized protein and immature proteins are easily aggregated because they ej(pose hydrophobic regions. Many stress conditions, such as heat shock or hypoxia, slow down their folding process and cause accumulation of unfolded/misfolded proteins in the cell. Molecular chaperones, including heat shock'proteins (IISPs), are induced in these conditions, bind to unfolded/misfolded proteins, and help them to be folded or reflolded properly. The protective role of molecular chaperones for the cells under stress has been reported.
Expression of angiogenic factors such as vascular endothelial growth factor (VEGF) under conditions of cell stress involves both transcriptionaland translational events, as well as an important role for inducible endoplasmicreticulum (ER) chaperones. Coexpression of VEGF and 150-kDaoxygen-regulated protein (ORP), a novel ER chaperone, in human glioblastomasuggested a link between angiogenesis and ORP150. C6 gliomacells stably transfected with ORP150 antisense
… More
displayed selectively reduced ORP150 expression. Tumors raised after in culation of immunocompromisedmice with ORP150 antisense C6 glioma transfectants demonstratedan initial phase of growth comparable to wild-type C6 gliomacells which was followed by marked regression within 8 days. Decreaseddensity of platelet/endothelial cell adhesion molecule 1-positive structureswithin the tumor bed was consistent with reduced angiogenesis in C6 gliomas expressing ORP150 antisense, compared with tumors derived from C6 cells overexpressing ORP150 sense or vector controls. In vitro,inhibition of ORP150 expression decreased release of VEGF into culturesupernatants ; in ORP150 antisense transfectants, VEGF accumulatedintracellularly within the ER. These findings demonstrate a critical rolefor the inducible ER chaperone ORP150 in tumor-mediated angiogenesisvia processing of VEGF, and, thus, highlight a new facet of angiogenicmechanisms amenable to therapeutic manipulation in tumors.
Heat shock proteins (HSPs)/stress proteins are molecular chaperflnes that are induced by various environmental and physiological stimuli. Evidence of the relations between the expression of HSPs and the regulation of cell growth or transformation has accumulated. The 150-kDa oxygen-regulated protein (ORP150), a new member of lisp family, functions as a molecular chaperone in the endoplasmic reticulum. We have examined whether transduced antisense ORP150 cDNA reduces tumorigenicity and angiogenicity. Relations between these stress proteins and cancer and possibilities for anticancer gene therapy are described. Less
|
