CBP501-calmodulin binding contributes to sensitizing tumor cells to cisplatin and bleomycin.

Abstract

CBP501 is an anticancer drug currently in randomized phase II clinical trials for patients with non-small cell lung cancer and malignant pleural mesothelioma. CBP501 was originally described as a unique G(2) checkpoint-directed agent that binds to 14-3-3, inhibiting the actions of Chk1, Chk2, mitogen-activated protein kinase-activated protein kinase 2, and C-Tak1. However, unlike a G(2) checkpoint inhibitor, CBP501 clearly enhances the accumulation of tumor cells at G(2)-M phase that is induced by cisplatin or bleomycin at low doses and short exposure. By contrast, CBP501 does not similarly affect the accumulation of tumor cells at G(2)-M that is induced by radiation, doxorubicin, or 5-fluorouracil treatment. Our recent findings point to an additional mechanism of action for CBP501. The enhanced accumulation of tumor cells at G(2)-M upon combined treatment with cisplatin and CBP501 results from an increase in intracellular platinum concentrations, which leads to increased binding of platinum to DNA. The observed CBP501-enhanced platinum accumulation is negated in the presence of excess Ca(2+). Some calmodulin inhibitors behave similarly to, although less potently than, CBP501. Furthermore, analysis by surface plasmon resonance reveals a direct, high-affinity molecular interaction between CBP501 and CaM (K(d) = 4.62 × 10(-8) mol/L) that is reversed by Ca(2+), whereas the K(d) for the complex between CBP501 and 14-3-3 is approximately 10-fold weaker and is Ca(2+) independent. We conclude that CaM inhibition contributes to CBP501's activity in sensitizing cancer cells to cisplatin or bleomycin. This article presents an additional mechanism of action which might explain the clinical activity of the CBP501-cisplatin combination.

• Authors: Naoki Mine, Sayaka Yamamoto, Naoya Saito, Satoshi Yamazaki, Chikako Suda, Machiyo Ishigaki, Donald W Kufe, Daniel D Von Hoff, Takumi Kawabe
• Journal: Molecular cancer therapeutics (Mol Cancer Ther) Vol. 10 Issue 10 Pg. 1929-38 (Oct 2011) ISSN: 1538-8514 [Electronic] United States
• PMID: 21831962 (Publication Type: Journal Article)

Chemical References

• Calmodulin
• Cdc25C phosphatase (211-221)
• DNA Adducts
• Peptide Fragments
• cisplatin-DNA adduct
• Bleomycin
• cdc25 Phosphatases
• Calcium Chloride
• Cisplatin

Topics

• Antineoplastic Combined Chemotherapy Protocols (pharmacology)
• Bleomycin (administration & dosage, pharmacology)
• Calcium Chloride (pharmacology)
• Calmodulin (antagonists & inhibitors, metabolism)
• Cell Line, Tumor
• Cell Survival (drug effects)
• Cisplatin (administration & dosage, pharmacokinetics, pharmacology)
• DNA Adducts (biosynthesis)
• Drug Synergism
• Humans
• Neoplasms (drug therapy, metabolism, pathology)
• Peptide Fragments (pharmacokinetics, pharmacology)
• cdc25 Phosphatases (pharmacokinetics, pharmacology)