Defining MAP3 kinases required for MDA-MB-231 cell tumor growth and metastasis

Abstract

Analysis of patient tumors suggests multiple MAP3kinases (MAP3Ks) are critical for growth and metastasis of cancer cells. MAP3Ks selectively control the activation of ERK1/2, JNK, p38 and ERK5 in response to receptor tyrosine kinases and GTPases. We used MDA-MB-231 cells because of their ability to metastasize from the breast fat pad to distant lymph nodes for an orthotopic xenograft model to screen the function of seven MAP3Ks in controlling tumor growth and metastasis. Stable shRNA knockdown was used to inhibit the expression of each of the seven MAP3Ks, which were selected for their differential regulation of the MAPK network. The screen identified two MAP3Ks, MEKK2 and MLK3, whose shRNA knockdown caused significant inhibition of both tumor growth and metastasis. Neither MEKK2 nor MLK3 have been previously shown to regulate tumor growth and metastasis in vivo. These results demonstrated that MAP3Ks, which differentially activate JNK, p38 and ERK5 are necessary for xenograft tumor growth and metastasis of MDA-MB-231 tumors. The requirement for MAP3Ks signaling through multiple MAPK pathways explains why several members of the MAPK network are activated in cancer. MEKK2 was required for EGF receptor and Her2/Neu activation of ERK5, with ERK5 being required for metastasis. Loss of MLK3 expression increased mitotic infidelity and apoptosis in vitro. Knockdown of MEKK2 and MLK3 resulted in increased apoptosis in orthotopic xenografts relative to control tumors in mice, inhibiting both tumor growth and metastasis; MEKK2 and MLK3 represent untargeted kinases in tumor biology for potential therapeutic development.

MLK3 Regulates Paxillin Phosphorylation in Chemokine-Mediated Breast Cancer Cell Migration and Invasion to Drive Metastasis

“…7), in agreement with findings that MLK3 knockdown reduced lymph node metastases of MDA-MB-231 cells (50). Although MLK3 has been shown to promote cell survival (16,50), which might contribute to formation of metastases, we propose that an important mechanism through which MLK3 promotes metastasis is through facilitating cancer cell migration and invasion.…”

The MEK5/ERK5 signalling pathway in cancer: a promising novel therapeutic target

“…In fact, ERK5 activation leads to cell proliferation through modulation of CDKs and cyclin D1 [32,33], the epithelial-mesenchymal transition (EMT) [34,35], MET/HGF-induced migration [36], and integrin/FAK-mediated metastasis [37]. Remarkably, following knockdown of the MEK5/ERK5 pathway, tumour xenograft growth, metastasis, and the generation of tumour circulating cells was significantly reduced [35,38]. Nevertheless, in contrast with this body of data, a recent study reported that ERK5 expression was reduced in breast cancer tumour samples, correlating with a worse disease prognosis, and that ERK5 inhibition in MDA-MB-231 and Hs578 T breast cancer cell lines contributed to increased cell migration and invasion [39].…”

Domain Specificity of MAP3K Family Members, MLK and Tak1, for JNK Signaling inDrosophila

“…Genetic analyses in model organisms and biochemical studies in cultured cells have revealed that different JNK-dependent responses require selective use of various MAP3K proteins (Chen et al 2002;Stronach 2005;Cuevas et al 2007;Craig et al 2008;Cronan et al 2012). Figure 7 Tak1-dependent antibacterial defense in the absence or presence of ectopic chimera protein expression.…”

“…MLK family members mediate MAPK-dependent responses to cytokines, ceramide, fatty acids, and other stresses (Sathyanarayana et al 2002;Jaeschke and Davis 2007;Korchnak et al 2009;Kant et al 2011). Consequently, they are implicated in metabolic and neurodegenerative diseases, epithelial migration and healing, and tumor growth and metastasis, reflecting their broad tissue distribution in epithelia and the nervous system (Silva et al 2005;Jaeschke and Davis 2007;Chen et al 2010;Velho et al 2010;Cronan et al 2012;Stark et al 2012;Zhan et al 2012). Their roles in development have been more difficult to ascertain, as single and double gene knockouts in mice are viable (Brancho et al 2005;Bisson et al 2008).…”