MLK3 gene alterations affect WNT signaling

This work follows the one published in 2010 by Sérgia Velho from Professor Raquel Seruca’s group at IPATIMUP, in which MLK3 mutations were for the first described to occur in gastric and colorectal cancers. These mutations were associated with the induction of invasive potential of cancer cells. In the present work, the authors performed expression microarray analysis in order to determine the signaling pathways underlying the oncogenic properties of mutant MLK3. Besides describing the signaling pathways affected by mutant MLK3, this study also brings up a new mechanism of regulation of WNT signaling in cancer that might be responsible for the induction of colorectal cancer cell invasion.

Authors and Affiliations:

Sérgia Velho - Instituto de Patologia e Imunologia Molecular da Universidade do Porto, Portugal

Ana Pinto - New Therapies Group, INEB-Institute for Biomedical Engineering, Porto, Portugal

Danilo Licastro - CBM S.c.r.l. AREA SCIENCE PARK, Trieste, Italy

Maria José Oliveira - New Therapies Group, INEB-Institute for Biomedical Engineering, Porto, Portugal

Filipa Sousa - Instituto de Patologia e Imunologia Molecular da Universidade do Porto, Portugal

Elia Stupka - Center for Translational Genomics and Bioinformatics, San Raffaele Scientific Institute, Milano, Italy

Raquel Seruca - Instituto de Patologia e Imunologia Molecular da Universidade do Porto, Portugal; Medical Faculty of the University of Porto, Portugal

Abstract:

MLK3 gene mutations were described to occur in about 20% of microsatellite unstable gastrointestinal cancers and to harbor oncogenic activity. In particular, mutation P252H, located in the kinase domain, was found to have a strong transforming potential, and to promote the growth of highly invasive tumors when subcutaneously injected in nude mice. Nevertheless, the molecular mechanism underlying the oncogenic activity of P252H mutant remained elusive.

In this work, we performed Illumina Whole Genome arrays on three biological replicas of human HEK293 cells stably transfected with the wild-type MLK3, the P252H mutation and with the empty vector (Mock) in order to identify the putative signaling pathways associated with P252H mutation.

Our microarray results showed that mutant MLK3 deregulates several important colorectal cancer- associated signaling pathways such as WNT, MAPK, NOTCH, TGF-beta and p53, helping to narrow down the number of potential MLK3 targets responsible for its oncogenic effects.  A more detailed analysis of the alterations affecting the WNT signaling pathway revealed a down-regulation of molecules involved in the canonical pathway, such as DVL2, LEF1, CCND1 and c-Myc, and an up-regulation of DKK, a well-known negative regulator of canonical WNT signaling, in MLK3 mutant cells. Additionally, FZD6 and FZD10 genes, known to act as negative regulators of the canonical WNT signaling cascade and as positive regulators of the planar cell polarity (PCP) pathway, a non-canonic WNT pathway, were found to be up-regulated in P252H cells.

The results provide an overall view of the expression profile associated with mutant MLK3, and they support the functional role of mutant MLK3 by showing a deregulation of several signaling pathways known to play important roles in the development and progression of colorectal cancer. The results also suggest that mutant MLK3 may be a novel modulator of WNT signaling, and pinpoint the activation of PCP pathway as a possible mechanism underlying the invasive potential of MLK3 mutant cells.

Journal:

BMC Cancer

Link:

http://www.biomedcentral.com/1471-2407/14/182