mTORC1 inhibition and ECM-cell adhesion-independent drug resistance via PI3K-AKT and PI3K-RAS-MAPK feedback loops

Karina Galoian, H. Thomas Temple, Armen Galoyan

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Mammalian target of rapamycin (mTOR) serine threonine kinase is the enzyme that regulates cancer cell growth by altering nutrient supplies to cancer cells. The neuropeptide (proline-rich peptide 1 (PRP-1)), galarmin, produced by the brain neurosecretory cells is a mTOR kinase inhibitor with powerful 80% antiproliferative cytostatic effect in a high-grade chondosarcoma and other mesenchymal tumors. However, the negative feedback loop of phosphatidylinositol 3 kinase-Protein kinase B (PKB), PI3K-AKT and PI3K-rat sarcoma (RAS)-mitogen-activated protein kinase (MAPK) activation is well documented for mTOR inhibitors. This study explored the involvement of those loops in drug resistance after the treatment with mTOR complex 1 (mTORC1) inhibitor, PRP-1. Multidrug resistance assay (MDR) demonstrated that this cytokine did not inhibit permeability glycoprotein-mediated MDR in chondrosarcoma. Phospho-MAPK array in human chondrosarcoma cell line treated with galarmin (10 ìg/ml,) showed a strong upregulation of phosphorylated glycogen synthase kinase 3â (GSK3â) via activation of PI3K-AKT and MAPK feedback loops. Such GSK3â inactivation leads to â-catenin accumulation that entails drug resistance. The ability of cells to metastasize is reflected in their capacity to adhere to extracellular matrix and endothelium. Laminin cell adhesion assay demonstrated that PRP-1 in the same concentrations that inhibit mTOR kinase inhibited JJ012 chondrosarcoma cell adhesion. The neuropeptide did not have any effect on the expression of total focal adhesion kinase and its phosphorylated form. Thus, it was not accompanied by total HAT downregulation and total HDAC upregulation. Combinatorial treatments of PRP-1 withMAPK and PI3K/AKT inhibitors most probably will lead to full cytotoxicity overcoming drug resistance.

Original languageEnglish
Pages (from-to)885-890
Number of pages6
JournalTumor Biology
Volume33
Issue number3
DOIs
StatePublished - Jun 1 2012

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PRP-1 peptide
Sirolimus
Mitogen-Activated Protein Kinases
Phosphatidylinositol 3-Kinases
Drug Resistance
Proline
Cell Adhesion
Sarcoma
Chondrosarcoma
Glycogen Synthase Kinase 3
Peptides
Multiple Drug Resistance
Neuropeptides
Phosphotransferases
Up-Regulation
Phosphatidylinositol 3-Kinase
Catenins
Focal Adhesion Protein-Tyrosine Kinases
Neoplasms
Protein Array Analysis

Keywords

  • Chondrosarcoma
  • ECM-cell adhesion
  • mTORC1
  • Multidrug resistance

ASJC Scopus subject areas

  • Cancer Research
  • Medicine(all)

Cite this

mTORC1 inhibition and ECM-cell adhesion-independent drug resistance via PI3K-AKT and PI3K-RAS-MAPK feedback loops. / Galoian, Karina; Thomas Temple, H.; Galoyan, Armen.

In: Tumor Biology, Vol. 33, No. 3, 01.06.2012, p. 885-890.

Research output: Contribution to journalArticle

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abstract = "Mammalian target of rapamycin (mTOR) serine threonine kinase is the enzyme that regulates cancer cell growth by altering nutrient supplies to cancer cells. The neuropeptide (proline-rich peptide 1 (PRP-1)), galarmin, produced by the brain neurosecretory cells is a mTOR kinase inhibitor with powerful 80{\%} antiproliferative cytostatic effect in a high-grade chondosarcoma and other mesenchymal tumors. However, the negative feedback loop of phosphatidylinositol 3 kinase-Protein kinase B (PKB), PI3K-AKT and PI3K-rat sarcoma (RAS)-mitogen-activated protein kinase (MAPK) activation is well documented for mTOR inhibitors. This study explored the involvement of those loops in drug resistance after the treatment with mTOR complex 1 (mTORC1) inhibitor, PRP-1. Multidrug resistance assay (MDR) demonstrated that this cytokine did not inhibit permeability glycoprotein-mediated MDR in chondrosarcoma. Phospho-MAPK array in human chondrosarcoma cell line treated with galarmin (10 {\`i}g/ml,) showed a strong upregulation of phosphorylated glycogen synthase kinase 3{\^a} (GSK3{\^a}) via activation of PI3K-AKT and MAPK feedback loops. Such GSK3{\^a} inactivation leads to {\^a}-catenin accumulation that entails drug resistance. The ability of cells to metastasize is reflected in their capacity to adhere to extracellular matrix and endothelium. Laminin cell adhesion assay demonstrated that PRP-1 in the same concentrations that inhibit mTOR kinase inhibited JJ012 chondrosarcoma cell adhesion. The neuropeptide did not have any effect on the expression of total focal adhesion kinase and its phosphorylated form. Thus, it was not accompanied by total HAT downregulation and total HDAC upregulation. Combinatorial treatments of PRP-1 withMAPK and PI3K/AKT inhibitors most probably will lead to full cytotoxicity overcoming drug resistance.",
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