Abstract
Background: The expression and activity of ribonucleotide reductase (RR) has been associated with resistance to multiple drugs in human cancer. The use of antisense oligonucleotide drug, GTI-2040, a 20-mer phosphorothioate oligonucleotide complemented to the human RR M2 subunit mRNA, represents an effective strategy for inhibiting RR. The increased specificity due to the anti-resistance effect of GTI-2040 may also lead to a more favorable therapeutic outcome. Materials and Methods: To understand the molecular mechanism underlying RR inhibition, patients' blood samples were analyzed using multiple dimensional proteomics technology via matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) mass spectrometry. Results: A major difference occurred at 5k m/z in the MALDI profile, which appeared only in the non-responsive group and diminished after GTI-2040 treatment. This specific peptide peak remained at the basal level in responsive patients. The peak was identified to represent the F-box/LLR-repeat protein 17 (FBXL17) through nanoelectrospray ionization liquid chromatography-tandem mass spectrometry (nanoESI LC-MS/MS). Further characterization revealed that FBXL17/SKP2 directly interacts with the human RR M2 (RRM2) subunit to promote hRRM2 overexpression in the breast cancer cell line MCF-7. Conclusion: Validation of this protein using real-time RT-PCR indicates the F-box protein 17 (FBXL17) can serve as a therapeutic target and surrogate marker for breast cancer therapy.
Footnotes
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Abbreviations: RR, ribonucleotide reductase; RRM2, human ribonucleotide reductase M2 subunit; FBXL17, F-box/LLR-repeat protein 17; Skp2, S-phase kinase-like protein 2; WBCs, white blood cells; DBD, DNA-binding domain; MTH, Mammalian two hybridization, HUR, hydroxyurea resistant; CBB, coomassie bright blue.
- Received January 9, 2008.
- Revision received March 24, 2008.
- Accepted March 27, 2008.
- Copyright© 2008 International Institute of Anticaner Research (Dr. John G. Delinassios), All rights reserved