Cancer cell motility--on the road from c-erbB-2 receptor steered signaling to actin reorganization

Phosphorylation of the NF2 tumor suppressor in Schwann cells is mediated by Cdc42-Pak and requires paxillin binding

Mutations in the Neurofibromatosis type 2 tumor suppressor gene that encodes Schwannomin causes formation of benign schwannomas. Schwannoma cells lose their characteristic bipolar shape and become rounded with excessive ruffling membranes. Schwannomin is phosphorylated at serine 518 (S518) by p21 activated kinase (Pak). Unphosphorylated schwannomin is associated with growth inhibition but little is known about the function of the phosphorylated form, or the molecular events leading to its phosphorylation. Here, we report in SCs that schwannomin S518 phosphorylation requires binding to paxillin and targeting to the plasma membrane. Phospho-S518-schwannomin is enriched in the peripheral-most aspects of membrane specializations where paxillin, activated Pak, Cdc42 but not Rac are highly expressed. Schwannomin and Pak phosphorylation levels are not reduced in response to lowering Rac-GTP levels with NSC23766. Expression of schwannomin S518A/D-GFP variants each distinctively altered Schwann cell shape and polarity. These results are consistent with tight spatial regulation of S518 phosphorylation at the plasma membrane in a paxillin and Cdc42-Pak dependent manner that leads to local reorganization of the SC cytoskeleton.

Whole genome expression analysis for biologic rational pathway modeling: application in cancer prognosis and therapy prediction

Using semi-quantitative microarray technology, almost every one of the approximately 30 000 human genes can be analyzed simultaneously with a low rate of false-positives, a high specificity, and a high quantification accuracy. This is supported by data from comparative studies of microarrays and reverse-transcription PCR for established cancer genes including those for epidermal growth factor receptor (EGFR), human epidermal growth factor receptor-2 (HER2/ERBB2), estrogen receptor (ESR1), progesterone receptor (PGR), urokinase-type plasminogen activator (PLAU), and plasminogen activator inhibitor-1 (SERPINE1). As such, semi-quantitative expression data provide an almost completely comprehensive background of biological knowledge that can be applied to cancer diagnostics. In clinical terms, expression profiling may be able to provide significant information regarding (i) the identification of high-risk patients requiring aggressive chemotherapy; (ii) the pathway control of therapy predictive parameters (e.g. ESR1 and HER2); (iii) the discovery of targets for biologically rational therapeutics (e.g. capecitabine and trastuzumab); (iv) additional support for decisions about switching therapy; (v) target discovery; and (vi) the prediction of the course of new therapies in clinical trials. In conclusion, whole genome expression analysis might be able to determine important genes related to cancer progression and adjuvant chemotherapy resistance, especially in the context of new approaches involving primary systemic chemotherapy. In this review, we will survey the current progress in whole genome expression analyses for cancer prognosis and prediction. Special emphasis is given to the approach of combining biostatistical analysis of expression data with knowledge of biochemical and genetic pathways.

8-Chloro-adenosine inhibits growth at least partly by interfering with actin polymerization in cultured human lung cancer cells

A key feature of actin is its ability to bind and hydrolyze ATP. 8-Chloro-adenosine (8-Cl-Ado), which can be phosphorylated to the moiety of 8-Cl-ATP in living cells, inhibits tumor cell proliferation. Therefore we tested the hypothesis that 8-Cl-Ado can interfere with the dynamic state of actin polymerization. We found that 8-Cl-Ado inhibited the growth of human lung cancer cell line A549 and H1299 in culture, and arrested the target cells in G2/M phase evidenced by fluorescence-activated cell sorting (FACS). Immunocytochemistry showed that the normal organization of microfilaments was disrupted in 8-Cl-Ado-exposed cells, which is accompanied by the decrease of cell size and the alteration of cell shape, and by aberrant mitosis and apoptosis in targeted cells. Furthermore, in vitro light scattering assays revealed that 8-Cl-ATP could directly inhibit the transition of G-actin to F-actin. DNase I inhibition assays showed that the G/F-actin ratio, a surrogate marker of actin polymerization status in living cells, was significantly increased in 8-Cl-Ado-exposed A549 and H1299 cells, compared to the G/F-actin ratio in unexposed cells. Taken together, these results indicate that 8-Cl-Ado exposure can alter the dynamic properties of actin polymerization, disrupt the dynamic instability or the rearrangement ability of actin filaments. Therefore, our data suggest that 8-Cl-Ado may exert its cytotoxicity at least partly by interfering with the dynamic instability of microfilaments, which may correlate with its inhibitory effects on cell proliferation and cell death.

Specific peptide ligand for Grb7 signal transduction protein and pancreatic cancer metastasis

BACKGROUND

Pancreatic cancer is one of the most aggressive malignancies, with high rates of invasion and metastasis and with generally poor prognosis. We previously found that metastasis was strongly associated with the expression of growth factor receptor-bound protein 7 (Grb7), which contains a Src homology 2 (SH2) domain. In this study, we evaluated Grb7 protein as a molecular target of therapy for metastatic pancreatic cancer.

METHODS

Grb7 protein expression was measured by immunohistochemistry in 36 human pancreatic cancer specimens and adjacent normal pancreatic tissue. We synthesized a nonphosphorylated peptide inhibitor that binds specifically to the SH2 domain of Grb7. Intracellular signaling was assessed by immunoprecipitation and immunoblot assays in cultured human pancreatic cancer cells. Cell migration was measured with a modified Boyden chamber method. Peritoneal metastasis of the pancreatic cancer cells was measured with a mouse model. All statistical tests were two-sided.

RESULTS

We found that 22 (61%) of 36 pancreatic cancer specimens had higher levels of Grb7 protein than their corresponding normal pancreatic tissue specimens. Grb7 expression was statistically significantly different between specimens from patients without lymph node metastasis (stage N0; two of the 10 patients) and patients with lymph node metastasis (stages N1 + N2; 20 of the 26 patients) (P = .006). The Grb7 peptide inhibitor selectively blocked the interaction between Grb7 and focal adhesion kinase and blocked the phosphorylation of Grb7 protein. In vivo Grb7 peptide inhibitor statistically significantly attenuated cell migration (for control peptide, 87.5 cells migrated, 95% confidence interval [CI] = 82.6 to 92.4 cells; for Grb7 peptide, 5.7 cells migrated, 95% CI = 2.3 to 9.0 cells; P < .001) and peritoneal metastasis of the pancreatic cancer cells in a mouse model, as assessed by the number of nodules (control = 72.6 nodules, 95% CI = 55.8 to 89.4 nodules; and for Grb7 peptide = 3.2 nodules, 95% CI = 1.6 to 4.8 nodules; P < .001, t test) and their weight (control = 4.13 g, 95% CI = 3.40 to 4.86 g; Grb7 peptide = 0.19 g, 95% CI = 0.06 to 0.32 g; P < .001, t test).

CONCLUSIONS

The Grb7 peptide inhibitor appears to be a promising molecularly targeted therapeutic agent against metastatic pancreatic cancer.

FAK signaling is critical for ErbB-2/ErbB-3 receptor cooperation for oncogenic transformation and invasion

The overexpression of members of the ErbB tyrosine kinase receptor family has been associated with cancer progression. We demonstrate that focal adhesion kinase (FAK) is essential for oncogenic transformation and cell invasion that is induced by ErbB-2 and -3 receptor signaling. ErbB-2/3 overexpression in FAK-deficient cells fails to promote cell transformation and rescue chemotaxis deficiency. Restoration of FAK rescues both oncogenic transformation and invasion that is induced by ErbB-2/3 in vitro and in vivo. In contrast, the inhibition of FAK in FAK-proficient invasive cancer cells prevented cell invasion and metastasis formation. The activation of ErbB-2/3 regulates FAK phosphorylation at Tyr-397, -861, and -925. ErbB-induced oncogenic transformation correlates with the ability of FAK to restore ErbB-2/3–induced mitogen-activated protein kinase (MAPK) activation; the inhibition of MAPK prevented oncogenic transformation. In contrast, the inhibition of Src but not MAPK prevented ErbB–FAK-induced chemotaxis. In migratory cells, activated ErbB-2/3 receptors colocalize with activated FAK at cell protrusions. This colocalization requires intact FAK. In summary, distinct FAK signaling has an essential function in ErbB-induced oncogenesis and invasiveness.

The ErbB2 signaling network as a target for breast cancer therapy

Overexpression of the ErbB2/Her2 receptor tyrosine kinase in breast cancers is associated with the most aggressive tumors. Experimental studies have revealed that ErbB2 shows many features of a therapeutic target: ErbB2 is able to confer many of the characteristics of a cancerous cell, including uncontrolled proliferation, resistance to apoptosis and increased motility; ErbB2 overexpression is specific to tumor cells; as a cell surface-associated protein, it is easily accessible to drugs and as a kinase it is amenable to targeted inhibition by small molecules. Recent clinical results demonstrate the efficacy of ErbB2-targeting therapy and promise an expanding use of ErbB2-targeting drugs for breast cancer treatment. However, as only a fraction of patients responds successfully to therapy and risks of recurrence are still high, further investigation is required for an improved understanding of the complex network of signaling pathways underlying ErbB2-driven cancer progression.

Modulation of glioma BK channels via erbB2

Glioma cells show up-regulation and constitutive activation of erbB2, and its expression correlates positively with increased malignancy. A similar correlation has been demonstrated for the expression of gBK, a calcium-sensitive, large-conductance K(+) channel. We show here that glioma BK channels are a downstream target of erbB2/neuregulin signaling. Tyrphostin AG825 was able to disrupt the constituitive erbB2 activation in a dose-dependent manner, causing a 30-mV positive shift in gBK channel activation in cell-attached patches. Conversely, maximal stimulation of erbB2 with a recombinant neuregulin (NRG-1beta) caused a 12-mV shift in the opposite direction. RT-PCR studies reveal no change in the BK splice variants expressed in treated glioma cells. Furthermore, isolation of surface proteins through biotinylation did not show a change in gBK channel expression, and probing with phospho-specific antibodies showed no alteration in channel phosphorylation. However, fura-II Ca(2+) fluorescence imaging revealed a 35% decrease in the free intracellular Ca(2+) concentration after erbB2 inhibition and an increase in NRG-1beta-treated cells, suggesting that the observed changes most likely were due to alterations in [Ca(2+)](i). Consistent with this conclusion, neither tyrphostin AG825 nor NRG-1beta was able to modulate gBK channels under inside-out or whole-cell recording conditions when intracellular Ca(2+) was fixed. Thus, gBK channels are a downstream target for the abundantly expressed neuregulin-1 receptor erbB2 in glioma cells. However, unlike the case in other systems, this modulation appears to occur via changes in [Ca(2+)](i) without changes in channel expression or phosphorylation. The enhanced sensitivity of gBK channels in glioma cells to small, physiological Ca(2+) changes appears to be a prerequisite for this modulation.

MUC1 Mediates Transendothelial Migration in vitro by Ligating Endothelial Cell ICAM-1

MUC1 is a transmembrane glycoprotein expressed by normal breast epithelium and virtually all breast cancers. MUC1 is normally restricted to the apical surface of epithelia and loss of this polarized distribution in breast carcinomas is associated with lymph node metastasis. Our previous work found that MUC1 can bind intercellular adhesion molecule-1 (ICAM-1), mediating adhesion of breast cancer cells to a simulated blood vessel wall, and also triggering a calcium-based signal in the MUC1-bearing cells. It is possible that the depolarized membrane distribution of MUC1 in breast carcinomas may facilitate interactions with stromal/endothelial ICAM-1 leading to adhesion and subsequent migration through the vessel wall. In the current study, we provide evidence that ICAM-1 can influence the migration of cells that express endogenous or transfected MUC1. Migration across a gelatin-coated Transwell membrane could be increased in a step-wise manner by the sequential addition of ICAM-1-expressing cells (endothelial cells and fibroblasts), and ICAM-1-inducing inflammatory cytokines (tumour necrosis factor-alpha and interleukin-1 beta). Antibodies against MUC1 or ICAM-1, but not a control antibody, could abrogate migratory increases. Cells that did not express MUC1 were unresponsive to ICAM-1. Our current findings build on our earlier work, by suggesting that the end result of the MUC1/ICAM-1-mediated cell-cell adhesion and calcium-based signal is migration. This has implications for the exit of circulating tumour cells from the vasculature, as well as tumour cell migration through fibroblast-containing stroma underlying the endothelial wall.

In vitro and in vivo imaging of cell migration: Two interdepending methods to unravel metastasis formation

Metastasis development requires the migratory activity of tumor cells. It is therefore important to understand the molecular mechanisms of this migration in order to prevent metastasis development, which is the pernicious step in most solid tumor diseases. A lot of methods have been invented to investigate tumor cell migration, but not all are equally suited and no method alone is able to deliver a complete picture of tumor cell migration. We herein suggest a combination of three-dimensional in vitro and in vivo methods for the investigation of tumor cell migration and summarize the knowledge, which has been reached so far.

Analysis methods of human cell migration

The autonomous migration of specialized cells is an essential characteristic in both physiological and pathological functions in the adult human organism. Leukocytes, fibroblasts, and stem cells, but also tumor cells, are thus the subject of intense investigation in a broad range of research fields. A wide spectrum of methods have therefore been established to analyze chemokinetic and chemotactic cell migration, ranging from easy-to-handle two-dimensional surface migration assays to highly specialized three-dimensional and intravital analysis methods. It is now manifest that the results obtained with these various migration assays substantially differ. This review therefore gives an overview of the migration assays which are currently in use, describes the methods, and critically enlightens the particular advantages and disadvantages of each method.

A neural Wiskott-Aldrich Syndrome protein-mediated pathway for localized activation of actin polymerization that is regulated by cortactin

Activation of the epidermal growth factor (EGF) receptor can stimulate actin polymerization via the Arp2/3 complex using a number of signaling pathways, and specific stimulation conditions may control which pathways are activated. We have previously shown that localized stimulation of EGF receptor with EGF bound to beads results in localized actin polymerization and protrusion. Here we show that the actin polymerization is dependent upon activation of the Arp2/3 complex by neural Wiskott-Aldrich Syndrome protein (N-WASP) via Grb2 and Nck2. Suppression of Grb2 or Nck2 results in loss of localization of N-WASP at the activation site and reduced actin polymerization. Although cortactin has been found to synergize with N-WASP for Arp2/3-dependent actin polymerization in vitro, we find that cortactin can restrict N-WASP localization around EGF-bead-induced protrusions. In addition, cortactin-deficient cells have increased lamellipod dynamics but show reduced net translocation, suggesting that cortactin can contribute to cell polarity by controlling the extent of Arp2/3 activation by WASP family members and the stability of the F-actin network.

The ErbB2/Neu/HER2 receptor is a new calmodulin-binding protein

We have demonstrated previously that the EGFR (epidermal growth factor receptor) is a calmodulin (CaM)-binding protein. To establish whether or not the related receptor ErbB2/Neu/HER2 also binds CaM, we used human breast adenocarcinoma SK-BR-3 cells, because these cells overexpress this receptor thus facilitating the detection of this interaction. In the present paper, we show that ErbB2 could be pulled-down using CaM-agarose beads in a Ca2+-dependent manner, as detected by Western blot analysis using an anti-ErbB2 antibody. ErbB2 was also isolated by Ca2+-dependent CaM-affinity chromatography. We also demonstrate using an overlay technique with biotinylated CaM that CaM binds directly to the immunoprecipitated ErbB2. The binding of biotinylated CaM to ErbB2 depends strictly on the presence of Ca2+, since it was prevented by the presence of EGTA. Moreover, the addition of an excess of free CaM prevents the binding of its biotinylated form, demonstrating that this was a specific process. We excluded any interference with the EGFR, as SK-BR-3 cells express considerably lower levels of this receptor, and no detectable EGFR signal was observed by Western blot analysis in the immunoprecipitated ErbB2 preparations used to perform the overlay assays with biotinylated CaM. We also demonstrate that treating living cells with W7 [N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide], a cell-permeant CaM antagonist, down-regulates ErbB2 phosphorylation, and show that W7 does not interfere non-specifically with the activity of ErbB tyrosine kinases. We also show that W7 inhibits the phosphorylation (activation) of both ERK1/2 (extracellular-signal-regulated kinases 1 and 2) and Akt/PKB (protein kinase B), in accordance with the inhibition observed in ErbB2 phosphorylation. In contrast, W7 treatment increased the phosphorylation (activation) of CREB (cAMP-response-element-binding protein) and ATF1 (activating transcription factor-1), two Ca2+-sensitive transcription factors that operate downstream of these ErbB2 signalling pathways, most likely because of the absence of calcineurin activity. We conclude that ErbB2 is a new CaM-binding protein, and that CaM plays a role in the regulation of this receptor and its downstream signalling pathways in vivo.

A Role for Drosophila IAP1-Mediated Caspase Inhibition in Rac-Dependent Cell Migration

Border cell migration in the Drosophila ovary is a relatively simple and genetically tractable model for studying the conversion of epithelial cells to migratory cells. Like many cell migrations, border cell migration is inhibited by a dominant-negative form of the GTPase Rac. To identify new genes that function in Rac-dependent cell motility, we screened for genes that when overexpressed suppressed the migration defect caused by dominant-negative Rac. Overexpression of the Drosophila inhibitor of apoptosis 1 (DIAP1), which is encoded by the thread (th) gene, suppressed the migration defect. Moreover, loss-of-function mutations in th caused migration defects but, surprisingly, did not cause apoptosis. Mutations affecting the Dark protein, an activator of the upstream caspase Dronc, also rescued RacN17 migration defects. These results indicate an apoptosis-independent role for DIAP1-mediated Dronc inhibition in Rac-mediated cell motility.

MUC1 Initiates a Calcium Signal after Ligation by Intercellular Adhesion Molecule-1

The MUC1 mucin is normally restricted to the apical surface of breast epithelial cells. In tumors, it is frequently overexpressed and underglycosylated. The MUC1 peptide core mediates firm adhesion of tumor cells to adjacent cells via binding to intercellular adhesion molecule-1 (ICAM-1). There is increasing evidence that MUC1 is involved in signaling, with current reports focusing on phosphorylation of the MUC1 cytoplasmic tail after indirect or artificial modes of stimulation. ICAM-1 is the only known direct ligand of the MUC1 extracellular domain. The data presented herein show that MUC1 expressed on the surface of breast cancer cell lines or transfected 293T cells can initiate a calcium-based oscillatory signal on contact with ICAM-1-transfected NIH 3T3 cells, and we present a novel method of quantifying and comparing calcium oscillations. The MUC1-induced signal appears to be distinct from those previously described, and may involve a Src family kinase, phosphoinositol 3-kinase, phospholipase C, and lipid rafts, but not mitogen-activated protein kinase. As calcium signaling has been associated with cytoskeletal change and motility, it is possible that the functions of MUC1 include heterotypic cell-cell adhesion followed by a calcium-based promigratory signal within tumor cells, thus facilitating metastasis.

Association with membrane protrusions makes ErbB2 an internalization-resistant receptor

In contrast to the epidermal growth factor (EGF) receptor, ErbB2 is known to remain at the plasma membrane after ligand binding and dimerization. However, why ErbB2 is not efficiently down-regulated has remained elusive. Basically, two possibilities exist: ErbB2 is internalization resistant or it is efficiently recycled after internalization. By a combination of confocal microscopy, immunogold labeling electron microscopy, and biochemical techniques we show that ErbB2 is preferentially associated with membrane protrusions. Moreover, it is efficiently excluded from clathrin-coated pits and is not seen in transferrin receptor-containing endosomes. This pattern is not changed after binding of EGF, heregulin, or herceptin. The exclusion from coated pits is so pronounced that it cannot just be explained by lack of an internalization signal. Although ErbB2 is a raft-associated protein, the localization of ErbB2 to protrusions is not a result of raft binding. Also, an intact actin cytoskeleton is not required for keeping ErbB2 away from coated pits. However, after efficient cross-linking, ErbB2 is removed from protrusions to occur on the bulk membrane, in coated pits, and in endosomes. These data show that ErbB2 is a remarkably internalization-resistant receptor and suggest that the mechanism underlying the firm association of ErbB2 with protrusions also is the reason for this resistance.

Biologic and therapeutic role of HER2 in cancer

Overexpression of the human epidermal growth factor-2 (HER2) oncogene in human breast carcinomas has been associated with a more aggressive course of disease. The reason for this association is still unclear, although it has been suggested to rest in increased proliferation, vessel formation, and/or invasiveness. Alternatively, prognosis may not be directly related to the presence of the oncoprotein on the cell membrane, but instead to the breast carcinoma subset identified by HER2 overexpression and characterized by a peculiar gene expression profile. HER2 has also been associated with sensitivity to anthracyclins and resistance to endocrine therapy, suggesting that tyrosine kinase receptor and hormone receptor pathways represent two major proliferation pathways exclusively active in breast carcinomas, one sensitive to chemotherapeutic drugs and the other to antiestrogens. HER2 currently represents one of the most appropriate targets for specific therapy. Indeed, trastuzumab, a monoclonal antibody directed against the extracellular domain of HER2, is therapeutically active in HER2-positive breast carcinomas. However, a consistent number of HER2-positive tumors is not responsive to HER2-driven therapy, indicating the need for a better understanding of the mechanism of action of this new biological drug in vivo. While preclinical studies suggest antibody-dependent cell cytotoxicity as the major mechanism, determination of NK activity at the time of treatment remains mandatory, especially in patients treated with immunosuppressive drugs. The efficacy of prophylactic vaccination has been fully demonstrated in preclinical models, whereas ongoing studies of active immunotherapy using a variety of vaccination regimens against HER2 in tumor-bearing mice and patients have met with only moderate success.

The formin-homology-domain-containing protein FHOD1 enhances cell migration

Formin-homology-domain-containing proteins interact with Rho-family GTPases and regulate actin cytoskeleton organization and gene transcription. FHOD1 is a member of this family, interacts with Rac1 and induces transcription from the serum response element. In this study, we examined the effects of FHOD1 expression on cytoskeletal organization and function in mammalian cells. FHOD1 proteins were stably expressed in WM35 melanoma cells and NIH-3T3 fibroblasts. Cells expressing full-length FHOD1 demonstrated an elongated phenotype compared with vector-transfected cells and cells expressing a truncated FHOD1 (1-421) that lacks the conserved FH1 and FH2 domains. Full-length FHOD1 co-localized with filamentous actin at cell peripheries. Cells transiently expressing a C-terminal FHOD1 truncation mutant (DeltaC, residues 1-1010), which lacks an autoinhibitory protein-protein interaction domain, displayed prominent stress fibers. FHOD1 (1-421) did not induce stress fibers but localized to membrane ruffles in a manner similar to the full-length protein, indicating that the FH1 and FH2 domains are required for stress fiber appearance. FHOD1 DeltaC (1-1010)-dependent stress fibers were sensitive to dominant-negative RacN17 and the RhoA and ROCK inhibitors, C3 transferase and Y-27632. Stable overexpression of full-length FHOD1 enhanced the migration of WM35 and NIH-3T3 cells to type-I collagen and fibronectin, respectively. Cells expressing FHOD1 (1-421) migrated similar to control cells. Integrin expression and activation were not affected by FHOD1 expression. Moreover, FHOD1 overexpression did not alter integrin usage during adhesion or migration. These data demonstrate that FHOD1 interacts with and regulates the structure of the cytoskeleton and stimulates cell migration in an integrin-independent manner.

The interface between ErbB and non-ErbB receptors in tumor invasion: clinical implications and opportunities for target discovery

The molecular switches by which malignant cancer cells evolve from a confined to an invasive state are poorly understood, but seem to involve a progressive activation of a signaling network shared by several growth factor receptors and non-receptor molecules. Abnormal expression of ErbB tyrosine kinase receptors, commonly seen in cancer, is an early event in the invasive process, which makes these receptors exciting targets for drug discovery. The past few years have been full of promise for ErbB targeting in the context of receptor overexpression, but also fraught with disappointment as clinical efficacy has often been hampered by potential problems such as the heterogeneity of receptor expression within the same tumor, and the extensive cooperative signaling among ErbB and non-ErbB receptors. Cooperative signaling is a common characteristic of invasive cancer cells, and is believed to dictate the genetic program that controls invasion switches. Molecular studies on the combinatorial signaling involved in tumor invasion are becoming a fertile area for target discovery in cancer. This review discusses how cooperative signaling between ErbB and non-ErbB receptors regulates tumor invasion and hence provides multiple opportunities for drug discovery, and how current therapies and investigational drugs could pave the way to even more potent alternative combinatorial therapeutic approaches for invasive cancers.

Induction of cancer cell migration by epidermal growth factor is initiated by specific phosphorylation of tyrosine 1248 of c-erbB-2 receptor via EGFR

Induction of tumor cell migration is a key step in invasion and metastasis. Here we report that the epidermal growth factor (EGF)-induced cell migration of breast cancer cells is attributed to a transient, rather than a sustained, activation of phospholipase C (PLC)-gamma1 due to c-erbB-2 signaling. EGF stimulation of EGF receptor (EGFR) overexpressing cells resulted in long-term PLC-gamma1 tyrosine phosphorylation and sustained levels of inositol-1,4,5-triphosphate (IP3) and diacylglycerol (DAG) producing sinusoidal calcium oscillations. In contrast, c-erbB-2/EGFR expressing cells displayed baseline transient calcium oscillations after EGF treatment due to short-term PLC-gamma1 tyrosine phosphorylation and short-term IP3 and DAG turnover. A third cell line expressing a point-mutated c-erbB-2 receptor that lacks the autophosphorylation Y1248 was generated to investigate whether the different PLC-gamma1 activation was attributed to this structure. Neither PLC-gamma1 tyrosine phosphorylation nor IP3 and DAG turnover and calcium oscillations were observed in this cell line, indicating the modulation of the PLC-g1 activation time course by c-erbB-2 signaling. Induction of cell migration was solely observable in the c-erbB-2-positive cell line as proved by the mode of actin reorganization and a cell migration assay, using a 3D-collagen lattice. In summary, c-erbB-2 up-regulation switches on the cell migration program by modulating the time course of PLC-gamma1 activation.