American Association for Cancer Research
Browse
00085472can076487-sup-t1_and_figs_1-2.pdf (209.85 kB)

Supplementary Table 1, Figures 1-2 from A New Pharmacologic Action of CCI-779 Involves FKBP12-Independent Inhibition of mTOR Kinase Activity and Profound Repression of Global Protein Synthesis

Download (209.85 kB)
journal contribution
posted on 2023-03-30, 18:11 authored by Boris Shor, Wei-Guo Zhang, Lourdes Toral-Barza, Jessica Lucas, Robert T. Abraham, James J. Gibbons, Ker Yu
Supplementary Table 1, Figures 1-2 from A New Pharmacologic Action of CCI-779 Involves FKBP12-Independent Inhibition of mTOR Kinase Activity and Profound Repression of Global Protein Synthesis

History

ARTICLE ABSTRACT

The mammalian target of rapamycin (mTOR) inhibitor CCI-779 (temsirolimus) is a recently Food and Drug Administration–approved anticancer drug with efficacy in certain solid tumors and hematologic malignancies. In cell culture studies, CCI-779 at the commonly used nanomolar concentrations generally confers a modest and selective antiproliferative activity. Here, we report that, at clinically relevant low micromolar concentrations, CCI-779 completely suppressed proliferation of a broad panel of tumor cells. This “high-dose” drug effect did not require FKBP12 and correlated with an FKBP12-independent suppression of mTOR signaling. An FKBP12-rapamycin binding domain (FRB) binding–deficient rapamycin analogue failed to elicit both the nanomolar and micromolar inhibitions of growth and mTOR signaling, implicating FRB binding in both actions. Biochemical assays indicated that CCI-779 and rapamycin directly inhibited mTOR kinase activity with IC50 values of 1.76 ± 0.15 and 1.74 ± 0.34 μmol/L, respectively. Interestingly, a CCI-779–resistant mTOR mutant (mTOR-SI) displayed an 11-fold resistance to the micromolar CCI-779 in vitro (IC50, 20 ± 3.4 μmol/L) and conferred a partial protection in cells exposed to micromolar CCI-779. Treatment of cancer cells with micromolar but not nanomolar concentrations of CCI-779 caused a marked decline in global protein synthesis and disassembly of polyribosomes. The profound inhibition of protein synthesis was accompanied by rapid increase in the phosphorylation of translation elongation factor eEF2 and the translation initiation factor eIF2α. These findings suggest that high-dose CCI-779 inhibits mTOR signaling through an FKBP12-independent mechanism that leads to profound translational repression. This distinctive high-dose drug effect could be directly related to the antitumor activities of CCI-779 and other rapalogues in human cancer patients. [Cancer Res 2008;68(8):2934–43]

Usage metrics

    Cancer Research

    Categories

    Keywords

    Licence

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC