Denmeade S R, Nagy A, Gao J, Lilja H, Schally A V, Isaacs J T
Johns Hopkins Oncology Center, Johns Hopkins School of Medicine, Baltimore, Maryland 21231-1001, USA.
Cancer Res. 1998 Jun 15;58(12):2537-40.
New approaches to target cytotoxic therapy specifically to metastatic prostate cancer sites are urgently needed. As such an approach, an inactive prodrug was synthesized by coupling the primary amine of doxorubicin to the COOH-terminal carboxyl of a seven-amino acid peptide carrier (i.e., Mu-His-Ser-Ser-Lys-Leu-Gln-Leu). The seven-amino acid peptide was documented to be hydrolyzable specifically by the serine protease prostate-specific antigen (PSA) to liberate the active cytotoxin L-leucyl-doxorubicin. Primary cultures of PC-82 human prostate cancer cells secreted high levels of enzymatically active PSA (i.e., 70 +/- 5 ng of enzymatically active PSA/10(6) cells/24 h), whereas LNCaP human prostate cancer cells produced lower levels of enzymatically active PSA (i.e., 2.3 +/- 1 ng/10(6) cells/24 h). LNCaP cells, however, secreted sufficient amounts of enzymatically active PSA to activate the doxorubicin prodrug to a cytotoxic form in vitro. The specificity of the cytotoxic response to the prodrug was demonstrated by the fact that 70 nM of the prodrug killed 50% of the PSA-producing LNCaP cells, whereas doses as high as 1 microM had no cytotoxic effect on PSA-nonproducing TSU human prostate cancer cells in vitro.
迫切需要新的方法将细胞毒性疗法特异性地靶向转移性前列腺癌部位。作为这样一种方法，通过将阿霉素的伯胺与一种七氨基酸肽载体（即Mu-His-Ser-Ser-Lys-Leu-Gln-Leu）的COOH末端羧基偶联，合成了一种无活性的前药。据记载，这种七氨基酸肽可被丝氨酸蛋白酶前列腺特异性抗原（PSA）特异性水解，从而释放出活性细胞毒素L-亮氨酰阿霉素。PC-82人前列腺癌细胞的原代培养物分泌高水平的具有酶活性的PSA（即70±5 ng具有酶活性的PSA/10⁶个细胞/24小时），而LNCaP人前列腺癌细胞产生的具有酶活性的PSA水平较低（即2.3±1 ng/10⁶个细胞/24小时）。然而，LNCaP细胞分泌了足够量的具有酶活性的PSA，能够在体外将阿霉素前药激活为细胞毒性形式。对前药的细胞毒性反应的特异性通过以下事实得到证明：70 nM的前药杀死了50%产生PSA的LNCaP细胞，而高达1 μM的剂量在体外对不产生PSA的TSU人前列腺癌细胞没有细胞毒性作用。
