Phosphorylation of chk1 at serine-345 affected by topoisomerase I poison SN-38

Gunnar Hapke; Ming-Biao Yin; Jiaxi Wu; Cheryl Frank; Youcef M Rustum

doi:10.3892/ijo.21.5.1059

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Journal article

Phosphorylation of chk1 at serine-345 affected by topoisomerase I poison SN-38

Gunnar Hapke, Ming-Biao Yin, Jiaxi Wu, Cheryl Frank and Youcef M Rustum

International journal of oncology, Vol.21(5), pp.1059-1066

11/2002

DOI: 10.3892/ijo.21.5.1059

PMID: 12370755

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Abstract

Human head and neck squamous carcinoma cell lines, A253 and FaDu, were utilized to identify mediators associated with response to topoisomerase I poison, SN-38, a metabolite of irinotecan. The drug sensitivity of FaDu cells to SN-38 was significantly higher than that of the A253 cells. In A253 cells, G2/M arrest following drug treatment (0.35 microM SN-38, 2-h exposure) was accompanied by DNA fragmentation in the 50-300 kb range, but FaDu cells accumulated in S-phase concurrently with induction of smaller DNA fragmentation in the 4-80 kb range. Because the critical regulatory step in activating cdc2 during progression into mitosis appears to be dephosphorylation of Tyrosine 15 (Tyr15), we examined the Tyr15 phosphorylation status of cdc2 in both cell lines. Slightly increased levels of cdc2 phosphorylation was observed in the A253 cells, while reduced levels of cdc2 phosphorylation was noted in the FaDu cells, corresponding to the abrogation of the G2-phase arrest. Increased chk1 phosphorylation at Ser345 induced by SN-38 was accompanied by the observed G2 phase arrest in the A253 cell line, while significant downregulation of chk1 and cdc25C phosphorylation, which resulted in the abrogation of G2/M checkpoint arrest, was noted in FaDu cells at this timepoint. These results suggest that alterations of chk1 signaling are associated with the response to topoisomerase I poison SN-38. Furthermore, A253 cells possess higher levels of endogenous hMLH1, compared to FaDu cells. A deficiency in G2 arrest was observed in FaDu cells, suggesting endogenous hMLH1 protein expression is associated with the abrogation of G2/M arrest, subsequently with the response to topoisomerase I poison SN-38.

14-3-3 Proteins

Adaptor Proteins, Signal Transducing

Antineoplastic Agents, Phytogenic - pharmacology

Camptothecin - analogs & derivatives

Camptothecin - pharmacology

Carrier Proteins

cdc25 Phosphatases - analysis

Cell Cycle Proteins - analysis

Checkpoint Kinase 1

DNA Damage

DNA Fragmentation - drug effects

DNA-Binding Proteins

Enzyme Inhibitors - pharmacology

G2 Phase - drug effects

Head and Neck Neoplasms - drug therapy

Head and Neck Neoplasms - metabolism

Head and Neck Neoplasms - pathology

Humans

MutL Protein Homolog 1

MutS Homolog 2 Protein

Neoplasm Proteins - analysis

Nuclear Proteins

Phosphorylation

Protein Kinases - metabolism

Proto-Oncogene Proteins - analysis

Serine - metabolism

Topoisomerase I Inhibitors

Tumor Cells, Cultured

Tyrosine 3-Monooxygenase - analysis

Details

Title: Subtitle: Phosphorylation of chk1 at serine-345 affected by topoisomerase I poison SN-38
Creators: Gunnar Hapke - Roswell Park Cancer Institute
Ming-Biao Yin
Jiaxi Wu
Cheryl Frank
Youcef M Rustum
Resource Type: Journal article
Publication Details: International journal of oncology, Vol.21(5), pp.1059-1066
DOI: 10.3892/ijo.21.5.1059
PMID: 12370755
ISSN: 1019-6439
eISSN: 1791-2423
Grant note: CA 16056 / NCI NIH HHS CA 65761 / NCI NIH HHS
Language: English
Date published: 11/2002
Academic Unit: Hematology, Oncology, and Blood & Marrow Transplantation; Internal Medicine
Record Identifier: 9984359665202771

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