Mixed lineage kinase 3 gene mutations in mismatch repair deficient gastrointestinal tumours

IPATIMUP-Institute of Molecular Pathology and Immunology of the University of Porto, 4200-465 Porto, Portugal.
Human Molecular Genetics (Impact Factor: 6.39). 12/2009; 19(4):697-706. DOI: 10.1093/hmg/ddp536
Source: PubMed


Mixed lineage kinase 3 (MLK3) is a serine/threonine kinase, regulating MAPkinase signalling, in which cancer-associated mutations have never been reported. In this study, 174 primary gastrointestinal cancers (48 hereditary and 126 sporadic forms) and 7 colorectal cancer cell lines were screened for MLK3 mutations. MLK3 mutations were significantly associated with MSI phenotype in primary tumours (P = 0.0005), occurring in 21% of the MSI carcinomas. Most MLK3 somatic mutations identified were of the missense type (62.5%) and more than 80% of them affected evolutionarily conserved residues. A predictive 3D model points to the functional relevance of MLK3 missense mutations, which cluster in the kinase domain. Further, the model shows that most of the altered residues in the kinase domain probably affect MLK3 scaffold properties, instead of its kinase activity. MLK3 missense mutations showed transforming capacity in vitro and cells expressing the mutant gene were able to develop locally invasive tumours, when subcutaneously injected in nude mice. Interestingly, in primary tumours, MLK3 mutations occurred in KRAS and/or BRAF wild-type carcinomas, although not being mutually exclusive genetic events. In conclusion, we have demonstrated for the first time the presence of MLK3 mutations in cancer and its association to mismatch repair deficiency. Further, we demonstrated that MLK3 missense mutations found in MSI gastrointestinal carcinomas are functionally relevant.

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Available from: Arsenio M Fialho
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    • "Our group reported the occurrence of MLK3 mutations in microsatellite unstable (MSI) gastrointestinal tumors (both sporadic and hereditary forms) in a frequency of about 20%. Using in vitro transforming assays, we demonstrated that several MLK3 mutations affecting different domains of the protein had transforming potential when compared to cells expressing the wild-type and the kinase-dead forms of the protein [15]. These results were further supported by in vivo studies in which one of the two most transforming mutations (P252H – located in the kinase domain) was found to be tumorigenic and to give rise to highly invasive tumors when subcutaneously injected in nude mice. "
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    • "Merlin inhibits MLK3 activation by directly interfering with MLK3 binding to Cdc42, a major MLK3 activator; thus providing a critical link between previous reports describing merlin suppression of Rac1 or MAPK activity (Chadee et al., 2006; Morrison et al., 2007). MLK3 is required for cell proliferation in normal and neoplastic cells, and a number of studies have demonstrated that exogenous expression of members of the MLK family is sufficient to promote neoplastic transformation (Cho et al., 2004; Hartkamp et al., 1999; Velho et al., 2010). However, deregulated MLK3 kinase activity in tumor-derived cells has not been previously reported. "
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