Molecular mechanisms of invadopodium formation

Abstract

Invadopodia are actin-rich membrane protrusions with a matrix degradation activity formed by invasive cancer cells. We have studied the molecular mechanisms of invadopodium formation in metastatic carcinoma cells. Epidermal growth factor (EGF) receptor kinase inhibitors blocked invadopodium formation in the presence of serum, and EGF stimulation of serum-starved cells induced invadopodium formation. RNA interference and dominant-negative mutant expression analyses revealed that neural WASP (N-WASP), Arp2/3 complex, and their upstream regulators, Nck1, Cdc42, and WIP, are necessary for invadopodium formation. Time-lapse analysis revealed that invadopodia are formed de novo at the cell periphery and their lifetime varies from minutes to several hours. Invadopodia with short lifetimes are motile, whereas long-lived invadopodia tend to be stationary. Interestingly, suppression of cofilin expression by RNA interference inhibited the formation of long-lived invadopodia, resulting in formation of only short-lived invadopodia with less matrix degradation activity. These results indicate that EGF receptor signaling regulates invadopodium formation through the N-WASP–Arp2/3 pathway and cofilin is necessary for the stabilization and maturation of invadopodia.

Arp2/3 complex-deficient mouse fibroblasts are viable and have normal leading-edge actin structure and function

“…Drosophila S2 cells depleted of the p20-Arc subunit of the Arp2͞3 complex as part of an extensive screen of cytoskeletal proteins had abnormal shapes and defects in spreading (16). Cultured carcinoma cells depleted by RNA interference of the p34-Arc subunit of the Arp2͞3 complex, although generally normal in appearance, had impaired protrusion of actin-rich nodules (''invadopodia'') associated with metastatic behavior (17). HeLa cells depleted of the p21-Arc subunit of the Arp2͞3 demonstrated defective cell growth (18).…”

LKB1 loss in melanoma disrupts directional migration toward extracellular matrix cues

“…Given the potent effect of LKB1 loss on invasion and metastasis, we expected that LKB1 loss would promote the formation of invadopodia, the matrix-degrading organelles often formed by metastatic cancer cells (Chen, 1989;Yamaguchi et al, 2005). Loss of LKB1 disrupts haptotaxis • Chan et al (1 mg/ml: null, n = 22; addback, n = 24.…”

Mapping proteolytic cancer cell-extracellular matrix interfaces

“…Whereas podosomes mostly appear in non-cancer cells, such as monocytes, endothelial cells, and Src-transformed fibroblasts, invadopodia are preferentially found in transformed cells, i.e. breast cancer, adenocarcinoma, and melanoma cells [13,23,25]. In summary, these different proteolytic structures are distinct in morphology, location, and life-time but they share membrane dynamics, cell surface adhesion receptors focalized towards the substrate, an underlying submembraneous dynamic actin network with actin-associated structural and signalling proteins, as well as the presence of proteases (Table 2).…”

“…Isolated decellularized basement membrane from in vivo tissue [3] Collagen I degradation in polymerized 3D collagen lattice stained with degradataion epitope-specific COL2 C short Ab [7,9] Collagen I, II and IV degradation epitope in histological sections stained with COL2C short Ab [67,68] or HUIV26 Ab [69] Clin Exp Metastasis (2009) 26:289-298 291 [23][24][25][26][27] (Fig. 1b).…”