高い腫瘍選択性を有する高分子化抗がん剤の開発に関する基礎的研究

博士（薬学）崇城大

Synthesis and In Vitro Assessment of pH-Sensitive Human Serum Albumin Conjugates of Pirarubicin

In a previous study, we reported on the development of a synthetic polymer conjugate of pirarubicin (THP) that was formed via an acid-labile hydrazone bond between the polymer and the THP. However, the synthetic polymer itself was non-biodegradable, which could lead to unexpected adverse effects. Human serum albumin (HSA), which has a high biocompatibility and good biodegradability, is also a potent carrier for delivering antitumor drugs. The objective of this study was to develop pH-sensitive HSA conjugates of THP (HSA-THP), and investigate the release of THP and the cytotoxicity under acidic conditions in vitro for further clinical development. HSA-THP was synthesized by conjugating maleimide hydrazone derivatives of THP with poly-thiolated HSA using 2-iminothiolane, via a thiol-maleimide coupling reaction. We synthesized two types of HSA-THP that contained different amounts of THP (HSA-THP2 and HSA-THP4). Free THP was released from both of the HSA conjugates more rapidly at an acidic pH, and the rates of release for HSA-THP2 and HSA-THP4 were similar. Moreover, both HSA-THPs exhibited a higher cytotoxicity at acidic pH than at neutral pH, which is consistent with the effective liberation of free THP under acidic conditions. These findings suggest that these types of HSA-THPs are promising candidates for further development

プロポリス成分カフェ酸エステル類がガングリオシドGD3 単分子膜に及ぼす影響

The distribution of benzyl caffeate (BC), cinnamyl caffeate (CC) and phenethyl caffeate (PC) isolated from propolis in ganglioside GD3 (GD3) monolayer as a model of a tumor membrane, and their effects of the caffeic acid esters on the GD3 monolayer were observed by atomic force microscopy (AFM). BC and PC distributed in the GD3 monolayer markedly changed the morphology of the GD3 monolayer from a flat surface to a percolated pattern, whereas CC distributed in the GD3 monolayer exhibited a broken percolation pattern. The effects of BC and PC on the GD3 membrane were similar to those of known antitumor compounds, suggesting that BC and PC may possess antitumor activity. The activity of CC seems to be weaker than that of BC and PC

ガングリオシドG[D3](GD3)単分子膜およびリン脂質/GD3混合単分子膜中へのカフェ酸の分布と作用

The distribution of caffeic acid (CA) in ganglioside GD3 (GD3) monolayer and in mixeddipalmitoylphosphatidylcholine (DPPC)/GD3 monolayer as models of tumor membrane, and the effects ofCA on the GD3 monolayer and the mixed DPPC/GD3 monolayer were observed by atomic forcemicroscopy (AFM). CA distributed in the GD3 monolayer markedly changed the morphology of the GD3monolayer from a flat and uniform surface to a percolated pattern. Furthermore, CA distributed in themixed DPPC/GD3 monolayer clearly changed the morphology of the mixed DPPC/GD3 monolayer froman unclear percolated surface to a typical percolation pattern. The effects of CA on the GD3 membraneand the mixed DPPC/GD3 membrane were similar to those of benzyl caffeate and known antitumorcompounds, suggesting that CA might possess antitumor activity

リン脂質/ガングリオシドG[D]₃混合単分子膜中へのカフェ酸エステル類の分布と作用

The distribution of benzyl caffeate (BC), cinnamyl caffeate (CC) and phenethyl caffeate (PC) isolatedfrom propolis in mixed dipalmitoylphosphatidylcholine (DPPC)/ganglioside GD3 (GD3) monolayer as amodel of a tumor membrane, and the effects of the caffeic acid esters on the mixed DPPC/GD3monolayer were observed by atomic force microscopy (AFM). BC distributed in the mixed DPPC/GD3monolayer formed a clear percolation pattern. The effect of BC on the mixed DPPC/GD3 membranewas similar to those of known antitumor compounds, suggesting that BC might possess antitumoractivity. The effect of PC on the mixed monolayer seems to be weaker than that of BC; however, onGD3 alone monolayer, the effect was similar to that of BC. It was suggested that the molecular size ofthe caffeic acid esters affected their activity on the mixed DPPC/GD3 monolayer

Synthesis and In Vitro Assessment of pH-Sensitive Human Serum Albumin Conjugates of Pirarubicin

In a previous study, we reported on the development of a synthetic polymer conjugate of pirarubicin (THP) that was formed via an acid-labile hydrazone bond between the polymer and the THP. However, the synthetic polymer itself was non-biodegradable, which could lead to unexpected adverse effects. Human serum albumin (HSA), which has a high biocompatibility and good biodegradability, is also a potent carrier for delivering antitumor drugs. The objective of this study was to develop pH-sensitive HSA conjugates of THP (HSA-THP), and investigate the release of THP and the cytotoxicity under acidic conditions in vitro for further clinical development. HSA-THP was synthesized by conjugating maleimide hydrazone derivatives of THP with poly-thiolated HSA using 2-iminothiolane, via a thiol-maleimide coupling reaction. We synthesized two types of HSA-THP that contained different amounts of THP (HSA-THP2 and HSA-THP4). Free THP was released from both of the HSA conjugates more rapidly at an acidic pH, and the rates of release for HSA-THP2 and HSA-THP4 were similar. Moreover, both HSA-THPs exhibited a higher cytotoxicity at acidic pH than at neutral pH, which is consistent with the effective liberation of free THP under acidic conditions. These findings suggest that these types of HSA-THPs are promising candidates for further development

Structural Basis of the Change in the Interaction Between Mycophenolic Acid and Subdomain IIA of Human Serum Albumin During Renal Failure

Mycophenolic acid (MP) is an active metabolite of mycophenolate mofetil, a widely used immunosuppressive drug. MP normally exhibits high plasma protein binding (97–99%), but its binding rate is decreased in patients with renal insufficiency. This decreased protein binding is thought to be associated with leukopenia, a side effect of MP. In this study, we characterized the change in protein binding of MP in renal failure patients. Our findings indicate that MP binds strongly to subdomain IIA of human serum albumin. X-ray crystallographic data indicated that the isobenzofuran group of MP forms a stacking interaction with Trp214, and the carboxyl group of MP is located at a position that allows the formation of hydrogen bonds with Tyr150, His242, or Arg257. Due to the specific binding of MP to subdomain IIA, MP is thought to be displaced by uremic toxin (3-carboxy-4-methyl-5-propyl-2-furan-propionic acid) and fatty acids (oleate or myristate) that can bind to subdomain IIA, resulting in the decreased plasma protein binding of MP in renal failure

Structural Basis of the Change in the Interaction Between Mycophenolic Acid and Subdomain IIA of Human Serum Albumin During Renal Failure

Mycophenolic acid (MP) is an active metabolite of mycophenolate mofetil, a widely used immunosuppressive drug. MP normally exhibits high plasma protein binding (97–99%), but its binding rate is decreased in patients with renal insufficiency. This decreased protein binding is thought to be associated with leukopenia, a side effect of MP. In this study, we characterized the change in protein binding of MP in renal failure patients. Our findings indicate that MP binds strongly to subdomain IIA of human serum albumin. X-ray crystallographic data indicated that the isobenzofuran group of MP forms a stacking interaction with Trp214, and the carboxyl group of MP is located at a position that allows the formation of hydrogen bonds with Tyr150, His242, or Arg257. Due to the specific binding of MP to subdomain IIA, MP is thought to be displaced by uremic toxin (3-carboxy-4-methyl-5-propyl-2-furan-propionic acid) and fatty acids (oleate or myristate) that can bind to subdomain IIA, resulting in the decreased plasma protein binding of MP in renal failure