title: 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.affiliation: CanBas Co. Ltd., Makiya Building 5F, 9 Tooriyoko-cho, Numazu 410-0891, Japan.
authors.forename: Shi-Ken
authors.initials: SK
authors.lastname: Sha
authors.forename: Takuji
authors.initials: T
authors.lastname: Sato
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Machiyo
authors.initials: M
authors.lastname: Ishigaki
authors.forename: Sayaka
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sato
authors.forename: Asako
authors.initials: A
authors.lastname: Takada
authors.forename: Sigetosi
authors.initials: S
authors.lastname: Nakajyo
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Mochizuki
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Friedman
authors.forename: Fong-Chi
authors.initials: FC
authors.lastname: Cheng
authors.forename: Takashi
authors.initials: T
authors.lastname: Okura
authors.forename: Ryohei
authors.initials: R
authors.lastname: Kimura
authors.forename: Donald W
authors.initials: DW
authors.lastname: Kufe
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Vonhoff
authors.forename: Takumi
authors.initials: T
authors.lastname: Kawabe
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D001761:Bleomycin / Q000009:adverse effects / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002945:Cisplatin / Q000009:adverse effects / Q000494:pharmacology; D016195:G2 Phase / Q000187:drug effects*; D045325:HCT116 Cells; D006801:Humans; D019169:Jurkat Cells; D008297:Male; D051379:Mice; D016513:Mice, SCID; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000473:pathology; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology*; D010641:Phenotype; D010766:Phosphorylation / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays; D020687:cdc25 Phosphatases / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; C517976:Cdc25C phosphatase (211-221); D018797:Cell Cycle Proteins; D010446:Peptide Fragments; D010455:Peptides; D001761:Bleomycin; C517009:CDC25C protein, human; C517010:Cdc25c protein, mouse; D020687:cdc25 Phosphatases; D002945:Cisplatin