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Enzymatic activation of a doxorubicin-peptide prodrug by prostate-specific antigen
1Johns Hopkins Oncology Center, Johns Hopkins School of Medicine, Baltimore, Maryland 21231-1001, USA.
Abstract:
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.
Insights
A novel doxorubicin prodrug targets prostate cancer by utilizing prostate-specific antigen (PSA) for activation. This targeted approach demonstrates specific cytotoxicity against PSA-producing cancer cells, offering a promising strategy for metastatic prostate cancer therapy.
Area of Science:
- Oncology
- Pharmacology
- Biochemistry
Background:
- Metastatic prostate cancer necessitates targeted cytotoxic therapies.
- Doxorubicin is a potent chemotherapy agent but lacks specificity.
- Prostate-specific antigen (PSA) is a biomarker overexpressed in prostate cancer.
Purpose of the Study:
- To develop and evaluate a novel doxorubicin prodrug activated by PSA.
- To assess the prodrug's efficacy and specificity against prostate cancer cells in vitro.
Main Methods:
- Synthesis of a doxorubicin prodrug linked to a PSA-cleavable peptide carrier.
- Culturing of human prostate cancer cell lines (PC-82, LNCaP, TSU) with varying PSA secretion levels.
- In vitro cytotoxicity assays to determine prodrug efficacy and specificity.
Main Results:
- The doxorubicin prodrug was specifically cleaved by PSA to release active cytotoxin.
- LNCaP cells, despite lower PSA levels, activated the prodrug, leading to cytotoxicity.
- PSA-nonproducing TSU cells showed no cytotoxicity even at high prodrug concentrations, demonstrating specificity.
Conclusions:
- The PSA-activated doxorubicin prodrug exhibits specific cytotoxicity against prostate cancer cells.
- This targeted drug delivery system holds potential for treating metastatic prostate cancer.
- Further research is warranted to explore in vivo efficacy and therapeutic applications.