CRISPR/Cas9 mutagenesis invalidates a putative cancer dependency targeted in on-going clinical trials.
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.
Cold Spring Harbor Laboratory, Cold Spring Harbor, United States.|Stony Brook University, Stony Brook, United States.
Ann
0000-0002-4618-8120
A
Lin
Cold Spring Harbor Laboratory, Cold Spring Harbor, United States.|Stony Brook University, Stony Brook, United States.
Christopher J
0000-0002-0586-6095
CJ
Giuliano
Cold Spring Harbor Laboratory, Cold Spring Harbor, United States.
Nicole M
0000-0001-7460-9095
NM
Sayles
Cold Spring Harbor Laboratory, Cold Spring Harbor, United States.
Jason M
0000-0003-1381-1323
JM
Sheltzer
D064113:CRISPR-Cas Systems; D045744:Cell Line, Tumor; D002470:Cell Survival; D055786:Gene Knockout Techniques; D018390:Gene Targeting; D006801:Humans; D016296:Mutagenesis; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism*
C484610:MELK protein, human; D017346:Protein Serine-Threonine Kinases
CRISPR; cancer biology; chromosomes; genes; genetic dependency; human; mitosis; protein kinase; triple-negative breast cancer