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Ducker GS, Atreya CE, Simko JP, Hom YK, Matli MR, Benes CH, Hann B, Nakakura EK, Bergsland EK, Donner DB, Settleman J, Shokat KM, Warren RS. Incomplete inhibition of phosphorylation of 4E-BP1 as a mechanism of primary resistance to ATP-competitive mTOR inhibitors. Oncogene 2013; 33:1590-600. [PMID: 23542178 PMCID: PMC3982880 DOI: 10.1038/onc.2013.92] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 12/19/2012] [Accepted: 01/25/2013] [Indexed: 12/12/2022]
Abstract
The mammalian target of rapamycin (mTOR) regulates cell growth by integrating nutrient and growth factor signaling and is strongly implicated in cancer. But mTOR is not an oncogene, and which tumors will be resistant or sensitive to new ATP-competitive mTOR inhibitors now in clinical trials remains unknown. We screened a panel of over 600 human cancer cell lines to identify markers of resistance and sensitivity to the mTOR inhibitor PP242. RAS and PIK3CA mutations were the most significant genetic markers for resistance and sensitivity to PP242, respectively; colon origin was the most significant marker for resistance based on tissue type. Among colon cancer cell lines, those with KRAS mutations were most resistant to PP242, while those without KRAS mutations most sensitive. Surprisingly, cell lines with co-mutation of PIK3CA and KRAS had intermediate sensitivity. Immunoblot analysis of the signaling targets downstream of mTOR revealed that the degree of cellular growth inhibition induced by PP242 was correlated with inhibition of phosphorylation of the translational repressor 4E-BP1, but not ribosomal protein S6. In a tumor growth inhibition trial of PP242 in patient-derived colon cancer xenografts, resistance to PP242 induced inhibition of 4E-BP1 phosphorylation and xenograft growth was again observed in KRAS mutant tumors without PIK3CA co-mutation, compared to KRAS WT controls. We show that, in the absence of PIK3CA co-mutation, KRAS mutations are associated with resistance to PP242 and that this is specifically linked to changes in the level of phosphorylation of 4E-BP1.
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Affiliation(s)
- G S Ducker
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA
| | - C E Atreya
- Department of Medicine, University of California, San Francisco, San Francisco, CA, USA
| | - J P Simko
- Department of Pathology, University of California, San Francisco, San Francisco, CA, USA
| | - Y K Hom
- 1] Preclinical Therapeutics Core, University of California, San Francisco, San Francisco, CA, USA [2] Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA, USA
| | - M R Matli
- 1] Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA, USA [2] Section of Surgical Oncology, Department of Surgery, University of California, San Francisco, San Francisco, CA, USA
| | - C H Benes
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA, USA
| | - B Hann
- 1] Preclinical Therapeutics Core, University of California, San Francisco, San Francisco, CA, USA [2] Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA, USA
| | - E K Nakakura
- 1] Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA, USA [2] Section of Surgical Oncology, Department of Surgery, University of California, San Francisco, San Francisco, CA, USA
| | - E K Bergsland
- Department of Medicine, University of California, San Francisco, San Francisco, CA, USA
| | - D B Donner
- 1] Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA, USA [2] Section of Surgical Oncology, Department of Surgery, University of California, San Francisco, San Francisco, CA, USA
| | - J Settleman
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA, USA
| | - K M Shokat
- 1] Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA [2] Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA, USA [3] Howard Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA
| | - R S Warren
- 1] Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA, USA [2] Section of Surgical Oncology, Department of Surgery, University of California, San Francisco, San Francisco, CA, USA
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