Heidi Ledford, Nature News, 05 April 2017, http://www.nature.com/news/crispr-studies-muddy-results-of-older-gene-research-1.21763
Researchers at Cold Spring Harbor Laboratory set out to study genes involved in tumor growth using the CRISPR/Cas9 system. For a control gene they chose MELK which many studies had implicated in cancer-cell proliferation. In fact, clinical trials are under way to test MELK inhibitors. Surprisingly, CRISPR knockout of MELK did not alter tumor growth. These results have now been published in eLife (https://www.ncbi.nlm.nih.gov/pubmed/28337968) and raise questions about the validity of previous screens which have predominantly used RNAi. This problem is not limited to cancer researchers but has also been identified in zebrafish and plants such as Arabidopsis. These conflicting results have researchers scrambling to repeat past experiments in an effort to re-evaluate previously identified gene functions.