Abstract
The proprotein convertase PACE4 has been validated as a potential target to develop new therapeutic interventions in prostate cancer (PCa). So far, the most effective compound blocking the activity of this enzyme has been designed based on the structure of a small peptide Ac-LLLLRVKR-NH2 known as the Multi-Leu (ML) peptide. Optimization of this scaffold led to the synthesis of compound C23 (Ac-[DLeu]LLLRVK-amidinobenzylamide) with a potent in vivo inhibitory effect on the tumor growth. However, further developments of PACE4 inhibitors may require additional improvements to counter their rapid renal clearance and to increase their tumor targeting efficiency. Herein, we explored the transformation of the ML-peptide into an albumin-binding prodrug containing a tumor specific release mechanism based on the prostate-specific antigen. Our data confirms that intravenous treatment using the ML-peptide alone has little effect on tumor growth, whereas by using the ML-prodrug in LNCaP xenograft-bearing mice it was significantly reduced. Additionally, excellent in vivo stability and tumor-targeting efficiency was demonstrated using a radiolabelled version of this compound. Taken together, these results provide a solid foundation for further development of targeted PACE4 inhibition in PCa.
Highlights
Prostate cancer (PCa) is the most commonly diagnosed cancer in North American men and it ranks second in cancer-related deaths[1,2]
The first designed albumin binding ML-ligand was composed by the linking of three fragments via amide bonds: (i) 6-maleimidohexanoic acid (EMC) as a thiol binding moiety, (ii) prostate-specific antigen (PSA) cleavable peptide sequence (RSSYYSL), (iii) a ML inhibitor (Fig. 1) and was synthesized using solid phase peptide synthesis (SPPS) as described in Methods
To confirm its binding affinity to albumin, the ML-ligand was incubated with the mouse serum albumin (MSA) and the formation of prodrug 1 (MSA-EMC-RSSYYSLLLLLRVKR-NH2) was monitored by a reverse-phase high-performance liquid chromatography (RP-HPLC) and matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF); for details see Methods
Summary
Prostate cancer (PCa) is the most commonly diagnosed cancer in North American men and it ranks second in cancer-related deaths[1,2]. The ML-peptide inhibits PACE4 with Ki value of 22 nM and exhibits potent anti-proliferative effect on PCa cell lines (DU145, LNCaP)[12], it only works in vivo if injected directly at the tumor site, whereas its intravenous administration is poorly effective[13]. This is due to both rapid clearance and poor stability. We decided to turn our attention to the covalent conjugation of developed inhibitors to the albumin, which can serve as a drug carrier
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
