Hemostatic Effect of Palliative Radiation Therapy in Preventing Blood Transfusions from Bleeding Occurring within Advanced Gastric Cancer.

Purpose: To report the hemostatic effects of palliative radiation therapy (RT) for the prevention of blood transfusions (BT) in patients with advanced gastric cancer (AGC). Methods and Materials: Twenty-eight patients who received palliative three-dimensional conformal RT for hemostasis of gastric bleeding were retrospectively assessed in a study conducted in Japan. The median follow-up was 143.5 days. Changes in hemoglobin (Hb) levels were compared at the beginning of RT and four weeks later. Blood transfusion-free survival (BTFS) and overall survival (OS) were measured from the beginning of RT. Treatment toxicity was evaluated within 60 days of RT initiation. Results: No statistically significant decrease in Hb level was observed four weeks after RT. Twenty-eight patients did not receive BT within a month after RT, of whom three died within a month; 6/28 patients (21%) received BT at a median interval of 99.5 days following RT. The one-year BTFS and OS rates for all patients were 69% and 12%, respectively. The one-year BTFS was statistically significantly higher in 17 patients treated with a biologically effective dose (BED)10 of 39 Gy (30 Gy in 10 fractions) (78%) compared with six patients treated with a BED10 of 48 Gy (40 Gy in 20 fractions) (25%). Grade 1 and 2 nausea (n = 11) and a Grade 2 increase in alanine aminotransferase (n = 1) were observed. One patient died of Grade 5 hemorrhage. Conclusions: Palliative RT is an effective treatment to prevent BT for bleeding occurring within AGC. Specifically, a fractionation regimen of 30 Gy in 10 fractions (a BED10 of 39 Gy) has a more durable hemostatic effect and thus should be considered for better prognosis.

Novel peptide-based pepsin inhibitors containing an epoxide group.

1,2-Epoxy-3-(p-nitrophenoxy)propane (EPNP) is known to inhibit pepsin A and other aspartic proteinases by reacting with the active site aspartic acid residue(s). However, the reaction is considerably slow in general, and therefore, it is desirable to develop similar reagents that are capable of inhibiting these enzymes more rapidly. In the present study, we synthesized a series of novel inhibitors which have a reactive epoxide group linked with peptide by a hydrazide bond, with a general structure: Iva-L-Val-L-Val-(L-AA)(n)-N2H2-ES-OEt (n = 0 approximately 2) (Iva, isovaleryl; AA, bulky hydrophobic or aromatic amino acid residue; ES, epoxysuccinyl). These inhibitors were shown to inhibit porcine pepsin A remarkably faster than EPNP.

Chemical synthesis and application of C-terminally 5-carboxyfluorescein-labelled thymopentin as a fluorescent probe for thymopoietin receptor.

Thymopentin (TP5) is a synthetic pentapeptide fragment, which corresponds to position 32 - 36 of thymic polypeptide thymopoietin. Thymopoietin and TP5 display a variety of biological functions, including phenotypic differentiation of T cells and the regulation of immune systems. Previous chemical modification experiments suggested that there was an absolute requirement for N-terminal amino acids to maintain the biological activity of TP5. On the basis of this structure-activity relationship, we designed and synthesized the C-terminally 5-carboxyfluorescein-coupled TP5 (TP5-FAM) as a fluorescent probe for thymopoietin receptor. TP5-FAM could bind to the membrane of human lymphoid cell lines, MOLT-4 cells, in which the thymopoietin receptor is expressed. The binding is specific and saturable (K(d) = 33 microM). TP5 and human splenopentin are nearly equipotent inhibitors of TP5-FAM binding to the thymopoietin receptor, but porcine secretin did not show any significant inhibition of TP5-FAM binding to MOLT-4 cells. Thus, TP5-FAM is suggested to be a potent and biologically active ligand that would be useful for studying the binding and functional characteristics of the human thymopoietin receptor.

Human antithrombin III-derived heparin-binding peptide, a novel heparin antagonist.

In the blood coagulation cascade, human antithrombin III (hAT III) acts as an inhibitor of serine proteases such as thrombin and factor Xa, and this anticoagulatory glycoprotein requires the binding of heparin for its activation. In this study, we synthesized the polypeptides corresponding to the proposed heparin-binding sites including the (41-49), (286-301) and (123-139) regions of hAT III, and examined their interactions with heparin by means of physicochemical and biochemical methods. All the synthetic peptides had a high affinity toward heparin, evidenced by the fact that they were eluted from a heparin-agarose column at the high salt concentration range of 520-700 mM. In addition, hAT III (123-139) attenuated the effect of heparin on the activation of hAT III, whereas other HBPs did not, suggesting that only hAT III (123-139) could interact with the active site of heparin. On the basis of these results, we prepared novel hAT III (123-139)-related derivatives as potent heparin antagonist candidates, and examined the influence of several modifications on their activity in vitro. The results provided new findings about the structure-activity relationship of hAT III (123-139), and led us to the successful development of a potent antagonist for heparin.

Novel approach for preparation of heparins specific to factor Xa using affinity chromatography coupled with synthetic antithrombin III-related peptides.

In the blood coagulation cascade, heparin activates human plasma antithrombin III (hAT III), resulting in the inhibition of factor Xa. This polysaccharide also exhibits hemorrhagic tendency mediated by the inhibition of thrombin in heparinotherapy. Therefore, attention has focused on the development of low molecular weight heparins (LMW-heparins) that inhibit factor Xa but not thrombin. In this investigation, we examined the biochemical and physicochemical properties of hAT III-derived heparin-binding peptides (HBPs). Of all the tested HBPs, hAT III (123-139) exhibited the highest affinity with heparin and showed an inhibitory effect on the heparin-induced enhancement of hAT III activity toward factor Xa, indicating that hAT III (123-139) specifically interacts with the active region in heparin. We prepared a synthetic hAT III (123-139)-coupled affinity chromatography system, and demonstrated that this novel affinity chromatography is useful for fractionation of highly active moieties in LMW-heparins.