Cell cycle phenotype-based optimization of G2-abrogating peptides yields CBP501 with a unique mechanism of action at the G2 checkpoint.

Abstract

Cell cycle G(2) checkpoint abrogation is an attractive strategy for sensitizing cancer cells to DNA-damaging anticancer agent without increasing adverse effects on normal cells. However, there is no single proven molecular target for this therapeutic approach. High-throughput screening for molecules inhibiting CHK1, a kinase that is essential for the G(2) checkpoint, has not yet yielded therapeutic G(2) checkpoint inhibitors, and the tumor suppressor phenotypes of ATM and CHK2 suggest they may not be ideal targets. Here, we optimized two G(2) checkpoint-abrogating peptides, TAT-S216 and TAT-S216A, based on their ability to reduce G(2) phase accumulation of DNA-damaged cells without affecting M phase accumulation of cells treated with a microtubule-disrupting compound. This approach yielded a peptide CBP501, which has a unique, focused activity against molecules that phosphorylate Ser(216) of CDC25C, including MAPKAP-K2, C-Tak1, and CHK1. CBP501 is >100-fold more potent than TAT-S216A and retains its selectivity for cancer cells. CBP501 is unusually stable, enters cells rapidly, and increases the cytotoxicity of DNA-damaging anticancer drugs against cancer cells without increasing adverse effects. These findings highlight the potency of CBP501 as a G(2)-abrogating drug candidate. This report also shows the usefulness of the cell cycle phenotype-based protocol for identifying G(2) checkpoint-abrogating compounds as well as the potential of peptide-based compounds as focused multitarget inhibitors.

• Authors: Shi-Ken Sha, Takuji Sato, Hidetaka Kobayashi, Machiyo Ishigaki, Sayaka Yamamoto, Hitoshi Sato, Asako Takada, Sigetosi Nakajyo, Yasuo Mochizuki, Jonathan M Friedman, Fong-Chi Cheng, Takashi Okura, Ryohei Kimura, Donald W Kufe, Daniel D Vonhoff, Takumi Kawabe
• Journal: Molecular cancer therapeutics (Mol Cancer Ther) Vol. 6 Issue 1 Pg. 147-53 (Jan 2007) ISSN: 1535-7163 [Print] United States
• PMID: 17237275 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents
• Cdc25C phosphatase (211-221)
• Cell Cycle Proteins
• Peptide Fragments
• Peptides
• Bleomycin
• CDC25C protein, human
• Cdc25c protein, mouse
• cdc25 Phosphatases
• Cisplatin

Topics

• Amino Acid Sequence
• Animals
• Antineoplastic Agents (chemistry, metabolism, pharmacology)
• Bleomycin (adverse effects, pharmacology)
• Cell Cycle Proteins (metabolism)
• Cell Death (drug effects)
• Cisplatin (adverse effects, pharmacology)
• G2 Phase (drug effects)
• HCT116 Cells
• Humans
• Jurkat Cells
• Male
• Mice
• Mice, SCID
• Models, Molecular
• Molecular Sequence Data
• Neoplasms (pathology)
• Peptide Fragments (chemistry, metabolism, pharmacology)
• Peptides (chemistry, pharmacology)
• Phenotype
• Phosphorylation (drug effects)
• Xenograft Model Antitumor Assays
• cdc25 Phosphatases (chemistry, metabolism, pharmacology)