Rac-specific guanine nucleotide exchange factor DOCK1 is a critical regulator of HER2-mediated breast cancer metastasis

Abstract

Progression of solid tumors to the metastatic stage is accountable for the majority of cancer-related deaths. Further understanding of the molecular mechanisms governing metastasis is essential for the development of antimetastatic regimens. Here, we aimed to identify Rac activators that could promote metastasis downstream of human epithelial growth factor receptor 2 (HER2). We investigated if Dedicator of Cytokinesis 1 (DOCK1), based on its evolutionarily conserved role in receptor tyrosine kinases (RTKs)-mediated Rac activation and cell invasion, could be a regulator of metastasis. We report that high expression of DOCK1 in HER2 + and basal breast cancer subtypes inversely correlates with human patients' survival. Mechanistically, DOCK1 interacts with HER2 and promotes HER2-induced Rac activation and cell migration. To gain further insight, we developed a HER2 breast cancer mouse model with mammary-gland-specific inactivation of DOCK1. In this in vivo model, a significant decrease in tumor growth and metastasis in lungs was found in animals where DOCK1 is inactivated. Furthermore, we found that DOCK1 is required for maximal activation of two HER2 effectors, c-JUN and STAT3. Using an unbiased gene profiling approach, we identified a mammary tumor DOCK1-associated gene signature enriched for genes implicated in response to IFN type I. This analysis revealed a unique set of genes, including Receptor Transporter Protein 4 (RTP4) and STAT1, for which the expression levels can be used to independently predict breast cancer outcome in HER2 + patients. Our work demonstrates DOCK1-Rac signaling as an HER2 effector pathway essential for HER2-mediated breast cancer progression to metastasis and offers a therapeutic opportunity to limit the spread of metastatic breast cancers.ErbB2 | DOCK180 | RhoGEF | tumorigenesis D espite breakthroughs in the treatment of breast cancer, the most prevalent cancer in women, progression of the disease remains an important cause of death. Virtually all fatalities can be attributed to complications due to the appearance of secondary tumors at distant sites. The identification and therapeutic targeting of proteins regulating the metastatic step is therefore a priority for improving the lifespan of afflicted patients (1). Two major breast cancer subtypes, basal-like and HER2 + , are linked to aggressive and recurrent primary and metastatic tumors, and ultimately, to poor survival (2). HER2 is a member of the EGF receptor family of receptor tyrosine kinases (RTKs) also comprising HER1, HER3, and HER4 (3). Amplification of the HER2 locus, or aberrant expression of its protein product, is observed in nearly 20% of human breast cancers (4). Mouse models expressing various forms of HER2 in the mammary gland recapitulate most aspects of the human disease, including metastasis, and are powerful tools to gain insight into signaling pathways controlling tumorigenesis in vivo (5). Nonetheless, regulators of HER2-mediated metastasis remain poorly characterized.Metastasis is a complex and deadly, yet ine...

Enoxaparin Sensitizes Human Non–Small-Cell Lung Carcinomas to Gefitinib by Inhibiting DOCK1 Expression, Vimentin Phosphorylation, and Akt Activation

“…DOCK1 is essential in multiple biologic processes involving cell migration and cell survival (Raftopoulou and Hall, 2004;Jarzynka et al, 2007;Li et al, 2013). Furthermore, this effect of DOCK1 in promoting cell migration was shown to be driven by the oncogenic receptor tyrosine kinase, including EGFR (Laurin et al, 2013). In this study, we reconfirmed the inhibitory effect of enoxaparin 1 gefitinib on DOCK1 expression in vitro and in vivo and on the basis of proteomic and in silico studies.…”

“…When DOCK1 is recruited to the plasma membrane from a cytoplasmic reservoir, changes in cellular morphology occur. Besides this distribution of traffic to the membrane by DOCK1, the phosphorylation of DOCK1 is important to activate related downstream pathways (Laurin et al, 2013;Feng et al, 2014;Gadea and Blangy, 2014). The distribution of DOCK1 and phosphorylated DOCK1 in the membrane and cytoplasm of cancer cells will be clarified in our future work.…”

“…Therefore, it is possible for enoxaparin to exert its function through interaction with proteins present on the cell surface, including DOCK1, which could be translocated across the plasma membrane (Kobayashi et al, 2001). It has been reported that the DOCK1 inhibitor blocked Rac activation and migration, and is therefore implicated as a next-generation drug for clinical use in combination with EGFR-TKI regimens to limit metastasis (Laurin et al, 2013). Enoxaparin regulation of DOCK1, identified by proteomics and network analysis in the present study, is implicated as the key node-targeted protein in the gefitinib-sensitized effect.…”

“…Among them, DOCK1 was the only downregulated protein influenced by the combination of enoxaparin and gefitinib. This protein has previously been reported to play an important role in tumor cell growth, migration, and metastasis (Jarzynka et al, 2007;Laurin et al, 2013).…”

TGF-β/Smad signaling through DOCK4 facilitates lung adenocarcinoma metastasis

“…The DOCK180 family, of which a total of 11 mammalian members have been identified (termed DOCK1/DOCK180 to DOCK11) emerged as a novel class of Rac/Cdc42 GTPase guanine nucleotide exchange factors (GEFs) (Cote and Vuori 2002;Meller et al 2005). This class of proteins has been implicated in diverse cell type-specific processes (Laurin and Cote 2014), with some of its members (i.e., DOCK1, DOCK3, and DOCK10) playing distinct roles in the progression and/or metastasis of diverse tumor types-including melanoma, breast cancer, and glioblastoma-by engaging in different proteinprotein interactions Sanz-Moreno et al 2008;Feng et al 2012;Laurin et al 2013). Whether any of the DOCK proteins play a role in the progression and/or metastasis of lung ADC has not been previously investigated.…”