Cool-1-mediated inhibition of c-Cbl modulates multiple critical properties of glioblastomas, including the ability to generate tumors in vivo

Stem Cells. 2014 May;32(5):1124-35. doi: 10.1002/stem.1644.

Abstract

We discovered that glioblastoma (GBM) cells use Cool-1/β-pix to inhibit normal activation of the c-Cbl ubiquitin ligase via the redox/Fyn/c-Cbl pathway and that c-Cbl inhibition is critical for GBM cell function. Restoring normal c-Cbl activity by Cool-1 knockdown in vitro reduced GBM cell division, almost eliminated generation of adhesion-independent spheroids, reduced the representation of cells expressing antigens thought to identify tumor initiating cells (TICs), reduced levels of several proteins of critical importance in TIC function (such as Notch-1 and Sox2), and increased sensitivity to BCNU (carmustine) and temozolomide (TMZ). In vivo, Cool-1 knockdown greatly suppressed the ability of GBM cells to generate tumors, an outcome that was c-Cbl dependent. In contrast, Cool-1 knockdown did not reduce division or increase BCNU or TMZ sensitivity in primary glial progenitor cells and Cool-1/c-Cbl complexes were not found in normal brain tissue. Our studies provide the first evidence that Cool-1 may be critical in the biology of human tumors, that suppression of c-Cbl by Cool-1 may be critical for generation of at least a subset of GBMs and offer a novel target that appears to be selectively necessary for TIC function and modulates chemoresistance in GBM cells. Targeting such proteins that inhibit c-Cbl offers potentially attractive opportunities for therapeutic development.

Keywords: Glioblastoma c-Cbl; Redox; Redox/Fyn/c-Cbl pathway; Tumor initiating cell; Tumor initiation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Antineoplastic Agents, Alkylating / pharmacology
  • Blotting, Western
  • Carmustine / pharmacology
  • Cell Line, Tumor
  • Cell Proliferation*
  • Cell Survival / drug effects
  • Cell Survival / genetics
  • Dacarbazine / analogs & derivatives
  • Dacarbazine / pharmacology
  • Flow Cytometry
  • Glioblastoma / genetics
  • Glioblastoma / metabolism*
  • Glioblastoma / pathology
  • HEK293 Cells
  • Humans
  • Male
  • Mice, Inbred NOD
  • Mice, SCID
  • Neoplastic Stem Cells / metabolism
  • Protein Binding / drug effects
  • Protein Binding / genetics
  • Proto-Oncogene Proteins c-cbl / metabolism*
  • RNA Interference
  • Rho Guanine Nucleotide Exchange Factors / genetics
  • Rho Guanine Nucleotide Exchange Factors / metabolism*
  • Signal Transduction / drug effects
  • Signal Transduction / genetics
  • Spheroids, Cellular / metabolism
  • Temozolomide
  • Transplantation, Heterologous
  • Tumor Burden / genetics
  • Tumor Cells, Cultured

Substances

  • ARHGEF7 protein, human
  • Antineoplastic Agents, Alkylating
  • Rho Guanine Nucleotide Exchange Factors
  • Dacarbazine
  • Proto-Oncogene Proteins c-cbl
  • CBL protein, human
  • Carmustine
  • Temozolomide