CUTL1 promotes tumor cell migration by decreasing proteasome-mediated Src degradation

Abstract

Recently, we identified the homeodomain transcription factor CUTL1 as important mediator of cell migration and tumor invasion downstream of transforming growth factor b (TGFb). The molecular mechanisms and effectors mediating the pro-migratory and pro-invasive phenotype induced by CUTL1 have not been elucidated so far. Therefore, the aim of this study was to identify signaling pathways downstream of CUTL1 which are responsible for its effects on tumor cell migration. We found that the reduced motility seen after knock down of CUTL1 by RNA interference is accompanied by a delay in tumor cell spreading. This spreading defect is paralleled by a marked reduction of Src protein levels. We show that CUTL1 leads to Src protein stabilization and activation of Srcregulated downstream signaling molecules such as RhoA, Rac1, Cdc42 and ROCK. In addition, we demonstrate that CUTL1 decreases proteasome-mediated Src protein degradation, possibly via transcriptionally upregulating Cterminal Src kinase (Csk). Based on experiments using Src knockout cells (SYF), we present evidence that Src plays a crucial role in CUTL1-induced tumor cell migration. In conclusion, our findings linking the pro-invasive transcription factor CUTL1 and the Src pathway provide important new insights in the molecular effector pathways mediating CUTL-induced migration and invasion.

p110 CUX1 Homeodomain Protein Stimulates Cell Migration and Invasion in Part through a Regulatory Cascade Culminating in the Repression of E-cadherin and Occludin

“…2). These results are in apparent contradiction with the observations made in a previous study where cell adhesion was not affected following the inhibition of CUX1 expression with siRNA (14). The discrepancy between these results could be attributed to the different substrates used in the two studies or more likely to the cells chosen for the experiments, as the PANC1 pancreatic cells adhered very rapidly and were almost completely spread after as little as 16 min, making it more difficult to see a difference in adhesion ability (14).…”

“…p110 CUX1 Stimulates Cell Spreading and Cell Adhesion-In a previous study, cell adhesion was not significantly altered following the knockdown of CUX1 expression with siRNA, although a spreading defect was observed (14). We therefore tested whether overexpression of p110 CUX1 would affect the ability of NMuMG-NYPD cells to adhere to plastic that was either un-coated or coated with Matrigel or collagen.…”

“…In a panel of human cancer cell lines, siRNA-mediated knockdown of CUX1 expression caused a decrease in cell motility and formation of lung metastasis as measured in a wound healing assay, an invasion assay through Matrigel, and in a pulmonary colonization assay after caudal vein injection (11). In addition, CUX1 silencing was later found to delay cell spreading, but not the adhesive properties of cells, upon seeding on a fibronectin-coated substrate (14).…”

CUX1, a haploinsufficient tumour suppressor gene overexpressed in advanced cancers

“…Many transcriptional targets and cellular functions of CUX1 readily suggest mechanisms by which increased p110 or p75 CUX1 expression might promote tumour development and progression, including acceleration of S phase entry 21,22,41,62,63 , stimulation of cell migration and invasion 13,42,[64][65][66] , resistance to apoptosis 14 , and promotion of bipolar mitosis in the presence of supernumerary centrosomes 19 (reviewed in REF. 67).…”

The roles of CUX1 homeodomain proteins in the establishment of a transcriptional program required for cell migration and invasion

“…Stable knockdown of CUX1 in two cell lines caused a reduction in the activity of RhoA, Cdc42 and Rac1. 25 In contrast, forced expression of p110 CUX1 lead to an increase in Rac and Cdc42 GTPase activity (Fig. 3).…”