Silicon Investor (SI) -- The First Internet Community

STOCKTALK

We've detected that you're using an ad content blocking browser plug-in or feature. Ads provide a critical source of revenue to the continued operation of Silicon Investor. We ask that you disable ad blocking while on Silicon Investor in the best interests of our community. If you are not using an ad blocker but are still receiving this message, make sure your browser's tracking protection is set to the 'standard' level.

Biotech / Medical : CYTO -- Ignore unavailable to you. Want to Upgrade?

To: Jim Oravetz who wrote (7834)	4/5/2000 12:57:00 PM
From: Jim Oravetz	Read Replies (1) \| Respond to of 8116

OT - EntreMed's abstract from AACR on PSA I believe this was a company PR. I snipped it from WSJ$. FWIW: The second abstract reinforced EntreMed's earlier reports that Prostate Specific Antigen (PSA), a marker of progressive prostate cancer, is a naturally occurring antiangiogenic molecule. EntreMed and its collaborators presented eleven abstracts at this year's AACR Annual Meeting. Selected abstracts are attached below..... ANTIANGIOGENIC PROPERTIES OF RECOMBINANT PROSTATE-SPECIFIC ANTIGEN. Fortier A, Holaday JW, Liang H, Dey C, Abbata F, Shivers W Y, Grella DK, Holland-Linn J, Vu HA, Nelson BJ, Sim BKL, EntreMed Inc, Rockville, MD. Prostate specific antigen (PSA), a member of the kallikrein family of proteins, with serine protease activity, is used as a diagnostic marker of prostate cancer. Using highly purified human PSA from Vitro Diagnostics, Inc., we recently described anti-angiogenic properties of PSA by virtue of its ability to inhibit endothelial cell responses to pro-angiogenic factors bFGF and VEGF. These data suggested that PSA may have an important biologic role in the regulation of the angiogenic balance during tumor growth. To further our hypothesis and determine the mechanism of the inhibitory activity of the molecule we cloned and expressed full length PSA in Pichia pastoris. The recombinant protein was purified by ammonium sulfate precipitation and cation exchange chromatography. After concentration/diafiltration recombinant PSA was tested for serine protease activity by hydrolysis of the chromogenic substrate S-2586 and anti-angiogenic activity by bFGF-stimulated endothelial cell migration. The rate of substrate hydrolysis by the recombinant was similar to that of native PSA. The concentration of PSA that resulted in a 50% inhibition (IC50) of endothelial cell migration was 0.6 micromolars for the native PSA and for the recombinant protein IC50=1.7 micromolars. To optimize expression of the clone, two mutant constructs were made by modifications of the N terminus; an N+1 and an N-1 clone. Due to the structural similarities between PSA and chymotrypsin, the N-terminus may be important for enzymatic activity of PSA. Neither of these clones expressed in P. pastoris had proteolytic activity as assess by the hydrolysis of S-2586, however, the yields for both clones were increased. Further characterization of these mutants and others for their anti-angiogenic responses is ongoing and will aid our understanding of this biological role of PSA.