CRISPR/Cas9 mutagenesis invalidates a putative cancer dependency targeted in on-going clinical trials

Elife. 2017 Mar 24;6:e24179. doi: 10.7554/eLife.24179.

Abstract

The Maternal Embryonic Leucine Zipper Kinase (MELK) has been reported to be a genetic dependency in several cancer types. MELK RNAi and small-molecule inhibitors of MELK block the proliferation of various cancer cell lines, and MELK knockdown has been described as particularly effective against the highly-aggressive basal/triple-negative subtype of breast cancer. Based on these preclinical results, the MELK inhibitor OTS167 is currently being tested as a novel chemotherapy agent in several clinical trials. Here, we report that mutagenizing MELK with CRISPR/Cas9 has no effect on the fitness of basal breast cancer cell lines or cell lines from six other cancer types. Cells that harbor null mutations in MELK exhibit wild-type doubling times, cytokinesis, and anchorage-independent growth. Furthermore, MELK-knockout lines remain sensitive to OTS167, suggesting that this drug blocks cell division through an off-target mechanism. In total, our results undermine the rationale for a series of current clinical trials and provide an experimental approach for the use of CRISPR/Cas9 in preclinical target validation that can be broadly applied.

Keywords: CRISPR; cancer biology; chromosomes; genes; genetic dependency; human; mitosis; protein kinase; triple-negative breast cancer.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • CRISPR-Cas Systems
  • Cell Line, Tumor
  • Cell Survival
  • Gene Knockout Techniques
  • Gene Targeting*
  • Humans
  • Mutagenesis*
  • Protein-Serine-Threonine Kinases / genetics*
  • Protein-Serine-Threonine Kinases / metabolism*

Substances

  • MELK protein, human
  • Protein-Serine-Threonine Kinases