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Supplementary material and supplementary tables

Melanoma is the deadliest skin cancer with a very poor prognosis in advanced stages. Although targeted and immune therapies have improved survival, not all patients benefit from these treatments. The mitogen-activated protein kinase ERK5 supports the growth of melanoma cells in vitro and in vivo. However, ERK5 inhibition results in cell-cycle arrest rather than appreciable apoptosis. To clarify the role of ERK5 in melanoma growth, we performed transcriptomic analyses following ERK5 knockdown in melanoma cells expressing BRAFV600E and found that cellular senescence was among the most affected processes. In melanoma cells expressing either wild-type or mutant (V600E) BRAF, both genetic and pharmacologic inhibition of ERK5 elicited cellular senescence, as observed by a marked increase in senescence-associated β-galactosidase activity and p21 expression. In addition, depletion of ERK5 from melanoma cells resulted in increased levels of CXCL1, CXCL8, and CCL20, proteins typically involved in the senescence-associated secretory phenotype. Knockdown of p21 suppressed the induction of cellular senescence by ERK5 blockade, pointing to p21 as a key mediator of this process. In vivo, ERK5 knockdown or inhibition with XMD8–92 in melanoma xenografts promoted cellular senescence. Based on these results, small-molecule compounds targeting ERK5 constitute a rational series of prosenescence drugs that may be exploited for melanoma treatment.Significance:This study shows that targeting ERK5 induces p21-mediated cellular senescence in melanoma, identifying a prosenescence effect of ERK5 inhibitors that may be exploited for melanoma treatment.

Combined treatment of metastatic melanoma with BRAF and MEK inhibitors has improved survival, but the emergence of resistance represents an important clinical challenge. Targeting ERK is a suitable strategy currently being investigated in melanoma and other cancers. To anticipate possible resistance to ERK inhibitors (ERKi), we used SCH772984 (SCH) as a model ERKi to characterize resistance mechanisms in two BRAF V600E melanoma cell lines. The ERKi-resistant cells were also resistant to vemurafenib (VMF), trametinib (TMT), and combined treatment with either VMF and SCH or TMT and SCH. Resistance to SCH involved stimulation of the IGF1R–MEK5–Erk5 signaling pathway, which counteracted inhibition of Erk1/2 activation and cell growth. Inhibition of IGF1R with linsitinib blocked Erk5 activation in SCH-resistant cells and decreased their growth in 3D spheroid growth assays as well as in NOD scid gamma (NSG) mice. Cells doubly resistant to VMF and TMT or to VMF and SCH also exhibited downregulated Erk1/2 activation linked to stimulation of the IGF1R–MEK5–Erk5 pathway, which accounted for resistance. In addition, we found that the decreased Erk1/2 activation in SCH-resistant cells involved reduced expression and function of TGFα. These data reveal an escape signaling route that melanoma cells use to bypass Erk1/2 blockade during targeted melanoma treatment and offer several possible targets whose disruption may circumvent resistance.Significance:Activation of the IGF1R–MEK5–Erk5 signaling pathway opposes pharmacologic inhibition of Erk1/2 in melanoma, leading to the reactivation of cell proliferation and acquired resistance.

Ex vivo effect of TG02 on primary myeloma cells analyzed in each of the patients separately.

Characterization of SCH-resistant, N-Ras mutant melanoma cells

Supplementary materials and methods and supplementary figure legends

Kinases inhibited by TG02 in the low nM range.

siRNAs and oligonucleotides used in qPCR experiments

Purpose: To analyze the antimyeloma potential of TG02, an ERK5/CDK inhibitory drug.Experimental Design: Utilizing different multiple myeloma cell lines we determined the effect of TG02 over viability by MTT assays. The apoptotic effect over multiple myeloma patient samples was studied ex vivo by cytometry. The mechanism of action of TG02 was analyzed in the cell line MM1S, studying its effect on the cell cycle, the induction of apoptosis, and the loss of mitochondrial membrane potential by cytometry and Western blot. Two models of multiple myeloma xenograft were utilized to study the in vivo action of TG02.Results: TG02 potently inhibited proliferation and survival of multiple myeloma cell lines, even under protective bone marrow niche conditions, and selectively induced apoptosis of primary patient-derived malignant plasma cells. TG02 displayed significant single-agent activity in two multiple myeloma xenograft models, and enhanced the in vivo activity of bortezomib and lenalidomide. Signaling analyses revealed that the drug simultaneously blocked the activity of CDKs 1, 2, and 9 as well as the MAP kinase ERK5 in MM1S cells, leading to cell-cycle arrest and rapid commitment to apoptosis. TG02 induced robust activation of both the intrinsic and extrinsic pathways of apoptosis, and depletion of XIAP and the key multiple myeloma survival protein Mcl-1.Conclusions: TG02 is a promising new antimyeloma agent that is currently in phase I clinical trials in leukemia and multiple myeloma patients. Clin Cancer Res; 19(10); 2677–87. ©2013 AACR.

2021 The Authors., Melanoma is the deadliest skin cancer with a very poor prognosis in advanced stages. Although targeted and immune therapies have improved survival, not all patients benefit from these treatments. The mitogen-activated protein kinase ERK5 supports the growth of melanoma cells in vitro and in vivo. However, ERK5 inhibition results in cell-cycle arrest rather than appreciable apoptosis. To clarify the role of ERK5 in melanoma growth, we performed transcriptomic analyses following ERK5 knockdown in melanoma cells expressing BRAFV600E and found that cellular senescence was among the most affected processes. In melanoma cells expressing either wild-type or mutant (V600E) BRAF, both genetic and pharmacologic inhibition of ERK5 elicited cellular senescence, as observed by a marked increase in senescence-associated β-galactosidase activity and p21 expression. In addition, depletion of ERK5 from melanoma cells resulted in increased levels of CXCL1, CXCL8, and CCL20, proteins typically involved in the senescence-associated secretory phenotype. Knockdown of p21 suppressed the induction of cellular senescence by ERK5 blockade, pointing to p21 as a key mediator of this process. In vivo, ERK5 knockdown or inhibition with XMD8–92 in melanoma xenografts promoted cellular senescence. Based on these results, small-molecule compounds targeting ERK5 constitute a rational series of prosenescence drugs that may be exploited for melanoma treatment., The work in E. Rovida’s lab was supported by grants from Associazione Italiana per la Ricerca sul Cancro (AIRC, IG-15282 and IG-21349), by Ente Fondazione Cassa di Risparmio di Firenze (ECRF), and Universita degli Studi di Firenze (Fondo di Ateneo ex-60%). A. Tubita was supported by a “Carlo Zanotti” Fondazione Italiana per la Ricerca sul Cancro (FIRC)-AIRC fellowship (ID-23847).

© The Author(s) 2021., Despite advances in its treatment, lung cancer still represents the most common and lethal tumor. Because of that, efforts to decipher the pathophysiological actors that may promote lung tumor generation/progression are being made, with the final aim of establishing new therapeutic options. Using a transgenic mouse model, we formerly demonstrated that the sole activation of the MEK5/ERK5 MAPK route had a pathophysiological role in the onset of lung adenocarcinomas. Given the prevalence of that disease and its frequent dismal prognosis, our findings opened the possibility of targeting the MEK5/ERK5 route with therapeutic purposes. Here we have explored such possibility. We found that increased levels of MEK5/ERK5 correlated with poor patient prognosis in lung cancer. Moreover, using genetic as well as pharmacological tools, we show that targeting the MEK5/ERK5 route is therapeutically effective in lung cancer. Not only genetic disruption of ERK5 by CRISPR/Cas9 caused a relevant inhibition of tumor growth in vitro and in vivo; such ERK5 deficit augmented the antitumoral effect of agents normally used in the lung cancer clinic. The clinical correlation studies together with the pharmacological and genetic results establish the basis for considering the targeting of the MEK5/ERK5 route in the therapy for lung cancer., This work was supported by grants from the Instituto de Salud Carlos III (PI15/01180 and PI19/00840, co-funded by European Union ERDF, “A way to make Europe”) to A. Esparís-Ogando. A. Sánchez-Fdez was supported by the Cancer Center Network Program from the ISCIII (RD12/0036/0003) and by a predoctoral fellowship from the Scientific Foundation of the Spanish Association Against Cancer (AECC). Our laboratory is supported by grants from the Ministry of Economy and Competitiveness of Spain (BFU2015-71371-R to A. Pandiella), the AECC and the CRIS Cancer Foundation. Our Cancer Research Institute, and the work carried out at our laboratory receive support from the European Community through the regional development funding program (FEDER). We are grateful to Nathanael S. Gray (Dana-Farber Cancer Institute, Boston, Massachusetts) for initially providing us with the compound JWG-071, and Dr. J. Lizcano (UAB, Barcelona, Spain) for advice on its in vivo use.

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar y los autores pertenecientes a la UAM, Sarcomas are a heterogeneous group of tumors in which the role of ERK5 is poorly studied. To clarify the role of this MAPK in sarcomatous pathology, we used a murine 3-methyl-cholanthrene (3MC)-induced sarcoma model. Our data show that 3MC induces pleomorphic sarcomas with muscle differentiation, showing an increased expression of ERK5. Indeed, this upregulation was also observed in human sarcomas of muscular origin, such as leiomyosarcoma or rhabdomyosarcoma. Moreover, in cell lines derived from these 3MC-induced tumors, abrogation of Mapk7 expression by using specific shRNAs decreased in vitro growth and colony-forming capacity and led to a marked loss of tumor growth in vivo. In fact, transcriptomic profiling in ERK5 abrogated cell lines by RNAseq showed a deregulated gene expression pattern for key biological processes such as angiogenesis, migration, motility, etc., correlating with a better prognostic in human pathology. Finally, among the various differentially expressed genes, Klf2 is a key mediator of the biological effects of ERK5 as indicated by its specific interference, demonstrating that the ERK5–KLF2 axis is an important determinant of sarcoma biology that should be further studied in human pathology, This work has been supported with Grant RTI2018-094093-B-I00 funded by MCIN/AEI/10.13039/501100011033, “ERDF A way of making Europe” to RSP. Also supported with funds from Fundación Leticia Castillejo Castillo, Roche España and ACEPAIN to RSP and MJRH. RSP and MJRH’s Research Institute and the work carried out in their laboratory, received partial support from the European Community through the FEDER. JJ and EAL hold a predoctoral research contract cofounded by the European Social Fund and UCLM. OR holds a contract for accessing the Spanish System of Science, Technology, and Innovation (SECTI) funded by the University of Castilla-La Mancha (UCLM) and received partial support from the European Social Fund (FSE) through its Operative Program for Castilla-La Mancha (2007–2013)

39 p.-7 fig., Combined treatment of metastatic melanoma with BRAF and MEK inhibitors has improved survival, but the emergence of resistance represents an important clinical challenge. Targeting ERK is a suitable strategy currently being investigated in melanoma and other cancers. To anticipate possible resistance to ERK inhibitors (ERKi), we used SCH772984 (SCH) as a model ERKi to characterize resistance mechanisms in two BRAF V600E melanoma cell lines. The ERKi-resistant cells were also resistant to vemurafenib (VMF), trametinib (TMT), and to combined treatment with either VMF and SCH or TMT and SCH. Resistance to SCH involved stimulation of the IGF-1R-MEK5-Erk5 signaling pathway, which counteracted inhibition of Erk1/2 activation and cell growth. Inhibition of IGF-1R with linsitinib blocked Erk5 activation in SCH-resistant cells and decreased their growth in 3D spheroid growth assays as well as in NOD scid gamma (NSG) mice. Cells doubly resistant to VMF and TMT or to VMF and SCH also exhibited downregulated Erk1/2 activation linked to stimulation of the IGF-1R-MEK5-Erk5 pathway, which accounted for resistance. In addition, we found that the decreased Erk1/2 activation in SCH-resistant cells involved reduced expression and function of TGF-alpha. These data reveal an escape signaling route that melanoma cells use to bypass Erk1/2 blockade during targeted melanoma treatment and offer several possible targets whose disruption may circumvent resistance., This work was supported by grants SAF2014-53059-R, SAF2017-85146-R and RD12/0036/0061 to J.T., and PI15/01180 to A.E-O.

The inhibition of bromo- and extraterminal domains (BET) has shown an anti-proliferative effect in triple negative breast cancer (TNBC). In this article we explore mechanisms of resistance to BET inhibitors (BETi) in TNBC, with the aim of identifying novel ways to overcome such resistance. Two cellular models of acquired resistance to the BET inhibitor JQ1 were generated using a pulsed treatment strategy. MTT, colony formation, and cytometry assays revealed that BETi-resistant cells were particularly sensitive to PLK1 inhibition. Targeting of the latter reduced cell proliferation, especially in resistant cultures. Quantitative PCR analysis of a panel of mitotic kinases uncovered an increased expression of AURKA, TTK, and PLK1, confirmed by Western blot. Only pharmacological inhibition of PLK1 showed anti-proliferative activity on resistant cells, provoking G2/M arrest, increasing expression levels of cyclin B, pH3 and phosphorylation of Bcl-2 proteins, changes that were accompanied by induction of caspase-dependent apoptosis. JQ1-resistant cells orthotopically xenografted into the mammary fat pad of mice led to tumours that retained JQ1-resistance. Administration of the PLK1 inhibitor volasertib resulted in tumour regression. These findings open avenues to explore the future use of PLK1 inhibitors in the clinical setting of BETi-resistant patients., This work has been supported by Instituto de Salud Carlos III (PI16/01121 and PI19/00808), ACEPAIN; Diputación de Albacete, CIBERONC and CRIS Cancer Foundation (to A. Ocaña). Ministry of Economy and Competitiveness of Spain (BFU2015-71371-R), the Instituto de Salud Carlos III through the Spanish Cancer Centers Network Program (RD12/0036/0003) and CIBERONC, the scientific foundation of the AECC and the CRIS Foundation (to A. Pandiella). The work carried out in our laboratories receive support from the European Community through the regional development funding program (FEDER). J.C. Montero is a recipient of a Miguel Servet fellowship program (CP12/03073 and CPII17/00015) and receives research support from the ISCIII (grants PI15/00684 and PI18/00796). E.M. Galan-Moya is funded by the implementation research program of the UCLM (UCLM resolution date: July 31, 2014), with a contract for accessing the Spanish System of Science, Technology and Innovation-SECTI (co-funded by the European Commission/FSE funds) and Council of Communities of Castilla-La Mancha (JCCM) (SBPLY/19/180501/000173). M. Burgos is funded by the Spanish Ministry for Science and Innovation, ref: BFU2015-69874-R and Castilla-La Mancha support grant for Biomedicine and Health Science Research ref: II-2018_11.

[Background] Triple negative breast cancer (TNBC) is an incurable disease where novel therapeutic strategies are needed. Proteolysis targeting chimeric (PROTAC) are novel compounds that promote protein degradation by binding to an ubiquitin ligase. In this work, we explored the antitumoral activity of two novel BET-PROTACs, MZ1 and ARV-825, in TNBC, ovarian cancer and in a BET inhibitor resistant model., [Methods] OVCAR3, SKOV3, BT549, MDA-MB-231 cell lines and the JQ1 resistant cell line MDA-MB-231R were evaluated. MTTs, colony-forming assay, three-dimensional cultures in matrigel, flow cytometry, and western blots were performed to explore the anti-proliferative effect and biochemical mechanism of action of MZ1 and ARV-825. In vivo studies included BALB/c nu/nu mice engrafted with MDA-MB-231R cells., [Results] The BET-PROTACs MZ1 and ARV-825 efficiently downregulated the protein expression levels of the BET protein BRD4, in MDA-MB-231 and MDA-MB-231R. MZ1 and ARV-825 also showed an antiproliferative effect on sensitive and resistant cells. This effect was corroborated in other triple negative (BT549) and ovarian cancer (SKOV3, OVCAR3) cell lines. MZ1 provoked G2/M arrest in MDA-MB-231. In addition, a profound effect on caspase-dependent apoptosis was observed in both sensitive and resistant cells. No synergistic activity was observed when it was combined with docetaxel, cisplatin or olaparib. Finally, in vivo administration of MZ1 rescued tumor growth in a JQ1-resistant xenograft model, reducing the expression levels of BRD4., [Conclusions] Using both in vitro and in vivo approaches, we describe the profound activity of BET-PROTACs in parental and BETi-resistant TNBC models. This data provides options for further clinical development of these agents in TNBC., This work has been supported by Instituto de Salud Carlos III (PI16/01121), ACEPAIN; Diputación de Albacete, CIBERONC and CRIS Cancer Foundation (to A. Ocaña). Ministry of Economy and Competitiveness of Spain (BFU2015–71371-R and BFU2015–69874-r), the Instituto de Salud Carlos III through the Spanish Cancer Centers Network Program (RD12/0036/0003) and CIBERONC, the scientific foundation of the AECC and the CRIS Foundation (to A. Pandiella). The work carried out in our laboratories receive support from the European Community through the regional development funding program (FEDER). J.C. Montero is funded by the Instituto de Salud Carlos III through a Miguel Servet program (CPII17/00015) and receives research support from the same institution (PI15/00684 and PI18/00796). E.M. Galan-Moya is funded by the implementation research program of the UCLM (UCLM resolution date: 31/07/2014), with a contract for accessing the Spanish System of Science, Technology and Innovation-SECTI (co-funded by the European Commission/FSE funds). M. Burgos is funded by the Spanish Ministry for Science and Innovation, ref.: BFU2015–69874-R and Castilla-La Mancha support grant for Biomedicine and Health Science Research ref.: II-2018_11.

Lung cancer represents the leading cause of cancer death worldwide [1]. Because of that, intense efforts are being devoted to the development of novel therapeutic strategies to fight the disease [2]. In this respect, identification of new oncogenic drivers offers therapeutic opportunities in tumours in which those molecules or other cooperating elements play a pathophysiological role. Here, we show that the MEK5 mitogen-activated protein kinase kinase has a pivotal role in lung cancer., MEK5 acts as an oncogenic driver in mice lung cancer and is pivotal for human lung adenocarcinoma http://ow.ly/M9e830mZb8N

[Purpose]: To analyze the antimyeloma potential of TG02, an ERK5/CDK inhibitory drug. [Experimental Design]: Utilizing different multiple myeloma cell lines we determined the effect of TG02 over viability by MTT assays. The apoptotic effect over multiple myeloma patient samples was studied ex vivo by cytometry. The mechanism of action of TG02 was analyzed in the cell line MM1S, studying its effect on the cell cycle, the induction of apoptosis, and the loss of mitochondrial membrane potential by cytometry and Western blot. Two models of multiple myeloma xenograft were utilized to study the in vivo action of TG02. [Results]: TG02 potently inhibited proliferation and survival of multiple myeloma cell lines, even under protective bone marrow niche conditions, and selectively induced apoptosis of primary patient-derived malignant plasma cells. TG02 displayed significant single-agent activity in two multiple myeloma xenograft models, and enhanced the in vivo activity of bortezomib and lenalidomide. Signaling analyses revealed that the drug simultaneously blocked the activity of CDKs 1, 2, and 9 as well as the MAP kinase ERK5 in MM1S cells, leading to cell-cycle arrest and rapid commitment to apoptosis. TG02 induced robust activation of both the intrinsic and extrinsic pathways of apoptosis, and depletion of XIAP and the key multiple myeloma survival protein Mcl-1. [Conclusions]: TG02 is a promising new antimyeloma agent that is currently in phase I clinical trials in leukemia and multiple myeloma patients., This work was supported by grants from the Ministry of Science and Innovation of Spain (BFU2009-07728/BMC to A. Pandiella) and Instituto de Salud Carlos III (PS09/00868 to A. Esparís-Ogando). S. Álvarez-Fernández is supported by the Cancer Center Network Program from the ISCIII (RD06/0020/0041). Our Cancer Research Institute, and the work carried out at our laboratory, receive support from the European Community through the regional development funding program (FEDER), and from the Fundación Ramón Areces.

Receptor tyrosine kinases (RTKs) are a superfamily of transmembrane proteins that mediate intracellular signaling by phosphorylating substrate proteins involved in cell proliferation, survival, differentiation or migration. The Human Epidermal growth factor Receptor (HER) family belongs to the RTKs superfamily, and comprises four members: EGFR (epidermal growth factor receptor), HER2, HER3 and HER4. Physiologically, these receptors are activated by the ligands of the EGF family. In solid tumors other mechanisms of activation, such as overexpression or molecular alterations have been reported, and have been linked to tumour initiation/progression. Because of that, several strategies have been developed to target HER receptors and include i) antibody-based therapies using monoclonal antibodies against the extracellular domain of these receptors, and ii) small molecule tyrosine kinase inhibitors (TKIs) against the intracellular kinase domain. In this review we will provide basic information about biological aspects of HER receptors and their ligands as well as the therapeutic strategies to target them. We also summarize general mechanisms of resistance generated in patients to such anti-HER therapies.

[Background]: Neuregulins (NRG) are a family of epidermal growth factor ligands which act through binding to HER3 and HER4 receptors. NRGs are widely expressed in solid tumors. Their prognostic significance or their role as predictors of benefit from anti-HER3 therapy is not known. [Results]: Of 29 included studies, 7 studies reported the association between NRG and outcome. NRG was most commonly expressed in breast, prostate, colon and bladder cancers. NRG expression was not associated with either OS or PFS (HR: 3.47, 95% CI 0.78-15.47, p = 0.10 and HR: 1.64, 95% CI 0.94-2.86, p = 0.08, respectively). In 4 placebo controlled trials of anti-HER3 therapy, the addition of anti-HER3 antibodies to control therapy in unselected patients was not associated with improved PFS (HR: 0.88, 95% CI 0.75-1.04. p = 0.14). However, in patients with high NRG expression, there was significantly delayed progression (HR: 0.35, 95% CI 0.23-0.52, p < 0.001). Anti-HER3 antibodies were associated with increased risk of diarrhea, nausea and rash. [Methods]: A search of electronically available databases identified studies exploring clinical outcomes based on NRG expression, as well as placebo-controlled trials of HER3- directed therapy reporting results based on NRG expression status. Data were combined in a meta-analysis using generic inverse variance and random effects modeling for studies reporting the hazard ratio (HR) for overall (OS) or progression-free survival (PFS). Mantel-Haenszel random-effect modeling was used for odds ratio (OR) for 3-year and 5-year OS and PFS. [Conclusions]: NRG expression is not associated with either OS or PFS, but is a predictor of benefit from anti-HER3 antibodies., Instituto de Salud Carlos III (PI13/01444), ACEPAIN; Diputación de Albacete and CRIS Foundation (to AO). Ministry of Economy and Competitiveness of Spain (BFU2012–39151), the Instituto de Salud Carlos III through the Spanish Cancer Centers Network Program (RD12/0036/0003), the scientific foundation of the AECC and the CRIS Foundation (to AP). Instituto de Salud Carlos III (PI15/01180) (to AE-O). JCM is a recipient of a Miguel Servet fellowship program (CP12/03073). The work carried out in the EU laboratories receive support from the European Community through the regional development funding program (FEDER).

Long-term survival remains low for most patients with glioblastoma (GBM), which reveals the need for markers of disease outcome and novel therapeutic targets. We describe that ODZ1 (also known as TENM1), a type II transmembrane protein involved in fetal brain development, plays a crucial role in the invasion of GBM cells. Differentiation of glioblastoma stem-like cells drives the nuclear translocation of an intracellular fragment of ODZ1 through proteolytic cleavage by signal peptide peptidase-like 2a. The intracellular fragment of ODZ1 promotes cytoskeletal remodelling of GBM cells and invasion of the surrounding environment both in vitro and in vivo. Absence of ODZ1 by gene deletion or downregulation of ODZ1 by small interfering RNAs drastically reduces the invasive capacity of GBM cells. This activity is mediated by an ODZ1-triggered transcriptional pathway, through the E-box binding Myc protein, that promotes the expression and activation of Ras homolog family member A (RhoA) and subsequent activation of Rho-associated, coiled-coil containing protein kinase (ROCK). Overexpression of ODZ1 in GBM cells reduced survival of xenografted mice. Consistently, analysis of 122 GBM tumour samples revealed that the number of ODZ1-positive cells inversely correlated with overall and progression-free survival. Our findings establish a novel marker of invading GBM cells and consequently a potential marker of disease progression and a therapeutic target in GBM., This work was supported by the Instituto de Salud Carlos III (ISCIII), grants PI13/01760 (JLF-L), PI12/00775 (PS-G) and SAF2014-53526-R (JL), and program Red Temática de Investigación Cooperativa en Cáncer (RTICC) grants RD12/0036/0022 (JLF-L), RD12/0036/0027 (PS-G), RD12/0036/0063 (JAM-C), RD12/0036/0003 (AP) and RD12-0036-0033 (JL), Instituto de Investigación Valdecilla (IDIVAL) grant APG/03 to JLF-L, and Cancer Research UK C33043/A12065 and Royal Society RG110591 to VS-M.

Background Breast cancer is the most common neoplasia in women. Formerly, we reported that the MAPK Erk5 participates in the proliferation of breast cancer cells in vitro, it is overexpressed in the tumours of a number of breast cancer patients, and its overexpression is an independent prognostic marker for disease-free survival. In addition, inhibition of Erk5 sensitized cells to treatments commonly used in the breast cancer clinic. Therefore, Erk5 may represent a novel therapeutic target in breast cancer. Here we describe the preclinical activity of TG02, a novel multi-kinase inhibitor being developed by Tragara Pharmaceuticals, in triple negative breast cancer (TNBC). TG02 presents a unique kinase inhibitory spectrum, combining Erk5 inhibitory properties with inhibition of CDKs and certain receptor tyrosine kinases. Material and methods: The action of TG02 on cell proliferation of TNBC cell lines was carried out by the MTT-based assay, and its action on cell death and cell cycle progression was analyzed by flow cytometry. The expression of different kinases and other proteins implicated in cell cycle, apoptosis and DNA damage responses were analyzed by western blotting. Studies on the action of TG02 in combination with chemotherapy were performed in MDAMB231 and HBL100 cells, and the potency of the combination was quantitated with the Calcusyn software. In vivo studies on the action of TG02 were performed in mice xenografted with the TNBC cell line MDA-MB231. Results: The TNBC cell lines analyzed showed high levels of Erk5 expression, and Erk5 was active under resting conditions in some of them. TG02 inhibited the kinase activity of Erk5 even though TG02 did not affect the Erk5 upstream activating kinase Mek5. TG02 showed an inhibitory effect of phosphorylation of residue Thr732 in the C-terminal tail of Erk5 without affecting the phosphorylation of the activation loop TEY motif. Cell proliferation studies indicated that one group of TNBC cells were very sensitive to the action of this compound (IC50 ≤100 nM) and another group were more resistant. TG02 induced cell cycle arrest at the early G1 and G2 phases of cell cycle, and triggered cell death in MDAMB231 (representative cell line of the most resistant group), and induced a strong effect of apoptosis and a DNA damage response in HCC1187(representative of the most sensitive group). In vitro studies indicated that TG02 sensitizes TNBC cells to chemotherapy, showing additive or synergistic effects depending of the doses. In vivo studies indicated that TG02 exerted a strong antitumoral action in mice bearing MDA-MB231-derived tumours. Conclusions: TNBC cells are very sensitive to TG02, both in vitro and in vivo. The inhibits the kinase activity of Erk5, which, together with the targeting of other kinases, may contribute to the induction of cell cycle arrest or apoptosis in response to the compound in TNBC cells. TG02 synergized with chemotherapy, supporting the possibility of using this drug in combination therapy. Taken together, these preclinical studies establish the bases for the clinical development of this compound for the treatment of TNBC. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-16-14.

Background: Intracellular signalling pathways associated with the oncogenesis of basal-like breast cancer are relatively unknown. Basal-like breast cancer constitutes 15% of all breast tumors. Although chemotherapy is the only treatment, no data support the use of one agent over others. Furthermore, combinations of chemotherapies with targeted agents against activated signalling pathways have not been explored. Here we have analyzed the action of the dual PI3K-AKT-mTOR pathway inhibitor BEZ235 on a panel of basal-like breast cancer cell lines. Methods: We used several triple negative breast cancer cell lines, and analyzed the action of BEZ235 on their proliferation and cell survival using MTT metabolization and other apoptosis assays. Biochemical experiments were performed to investigate the molecular bases of the action of BEZ235. Experiments in combination with chemotherapies were also performed to identify synergic combinations. Results: PI3K-AKT pathway was activated in most of the cell lines studied. Administration of the dual PI3K-mTOR inhibitor BEZ235 decreased AKT phosphorylation in a dose dependent manner. It also reduced signalling through the mTORC1 and mTORC2 complexes. BEZ235 also decreased proliferation of most cell lines with IC50 values Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-15-19.

[Background]: Receptor tyrosine kinases play an important role in breast cancer. One of them, the type I insulin-like growth factor, has been linked to resistance to trastuzumab (Herceptin), an agent that targets human epidermal growth factor receptor 2. Here, we show that the insulin-like growth factor-I receptor (IGF-IR) antagonist NVP-AEW541 inhibits proliferation of breast cancer cells and synergizes with trastuzumab. [Patients and methods]: Patient samples and breast cancer cell lines were evaluated for IGF-IR expression or activation by western blotting. 1-(4,5-Dimethylthiazol-2-yl)-3,5-diphenylformazan (MTT) uptake assays and Annexin V staining were used for the analyses of cell proliferation/ apoptosis. Biochemical and genomic studies were carried out to gain insights into the mechanism of action of NVP-AEW541. [Results]: The IGF-IR was expressed above normal levels in a number of breast cancer samples. Activation of this receptor was inhibited by NVP-AEW541 that also decreased cell proliferation and increased apoptosis. NVP-AEW541 decreased the amount of pAkt and increased the level of p27. Combination studies with several drugs used in the breast cancer clinic showed that NVP-AEW541 synergistically increased the action of trastuzumab. Conclusions: Our results show the anti-breast cancer action of NVP-AEW541 and support the clinical development of anti-IGF-IR agents, especially in combination with trastuzumab. © The Author 2008. Published by Oxford University Press on behalf of the European Society for Medical Oncology. All rights reserved., Ministry of Science and Technology of Spain (BFU2006-01813/ BMC to A.P.); Scientific Foundation of the Spanish Association for Cancer Research (AECC); Instituto de Salud Carlos III (PI061552 and CP04/00045 to A.E.O.); Spanish Cancer Centers Network Program (RD06/0020/0041); European Community through the regional development funding program (FEDER) to Cancer Research Institute.

[Objective]: The extracellular signal-regulated kinase 5 (ERK5 or BMK1) is involved in tumour development. The ERK5 gene may be amplified in hepatocellular carcinoma (HCC), but its biological role has not been clarified. In this study, we explored the role of ERK5 expression and activity in HCC in vitro and in vivo. [Design]: ERK5 expression was evaluated in human liver tissue. Cultured HepG2 and Huh-7 were studied after ERK5 knockdown by siRNA or in the presence of the specific pharmacological inhibitor, XMD8-92. The role of ERK5 in vivo was assessed using mouse Huh-7 xenografts. [Results]: In tissue specimens from patients with HCC, a higher percentage of cells with nuclear ERK5 expression was found both in HCC and in the surrounding cirrhotic tissue compared with normal liver tissue. Inhibition of ERK5 decreased HCC cell proliferation and increased the proportion of cells in G0/G1 phase. These effects were associated with increased expression of p27 and p15 and decreased CCND1. Treatment with XMD8-92 or ERK5 silencing prevented cell migration induced by epidermal growth factor or hypoxia and caused cytoskeletal remodelling. In mouse xenografts, the rate of tumour appearance and the size of tumours were significantly lower when Huh-7 was silenced for ERK5. Moreover, systemic treatment with XMD8-92 of mice with established HCC xenografts markedly reduced tumour growth and decreased the expression of the protooncogene c-Rel. [Conclusions]: ERK5 regulates the biology of HCC cells and modulates tumour development and growth in vivo. This pathway should be investigated as a possible therapeutic target in HCC.

Receptor tyrosine kinases of the ErbB family have been implicated in the onset/progression of a number of neoplasias. In these diseases, ErbB receptor expression may be accompanied by constitutive activation caused by molecular alterations, overexpression, or ligand binding. An important signaling route activated by these recep-tors that has been linked to the stimulation of cell proliferation is the Ras route. Here we have investigated the action of a mutant Ras form, H-RasN17, on the proliferation of the breast cancer epithelial cell line MCF7 cells. In these cells expression of RasN17 failed to affect serum or ErbB receptor-stimulated proliferation. Analysis of the action of RasN17 indicated that overexpression of this mutant form of Ras did not affect neuregulin or protein kinase C-induced activation of Erk1/2. In addition, RasN17 failed to prevent activation of endogenous N-Ras and H-Ras even though the levels of the latter were much lower than those of the RasN17 form. The failure of RasN17 to prevent endogenous Ras activation did not appear to be due to deficient processing or sorting of the mutated form. These data indicated that the action of RasN17 as a bona fide inhibitor of Ras depends on the cell type and requires detailed analysis of the biochemical and biological properties of RasN17, particularly with respect to the activation of endogenous Ras. © 2005 The Japanese Biochemical Society., We acknowledge funding from the Instituto de Salud Carlos III through project 01/1060. L.Y. was supported by a predoctoral fellowship from the Ministry of Science and Technology. AEO was supported by the Spanish Association Against Cancer (AECC).

Licensed under a Creative Commons Attribution 3.0 License., Triple negative breast cancers (TNBCs) account for 15% of all breast cancers, and represent one of the most aggressive forms of the disease, exhibiting short relapse-free survival. In contrast to other breast cancer subtypes, the absence of knowledge about the etiopathogenic alterations that cause TNBCs force the use of chemotherapeutics to treat these tumors. Because of this, efforts have been devoted with the aim of incorporating novel therapies into the clinical setting. Kinases play important roles in the pathophysiology of several tumors, including TNBC. Since expression of the MAP kinase ERK5 has been linked to patient outcome in breast cancer, we analyzed the potential value of its targeting in TNBC. ERK5 was frequently overexpressed and active in samples from patients with TNBC, as well as in explants from mice carrying genetically-defined TNBC tumors. Moreover, expression of ERK5 was linked to a worse prognosis in TNBC patients. Knockdown experiments demonstrated that ERK5 supported proliferation of TNBC cells. Pharmacological inhibition of ERK5 with TG02, a clinical stage inhibitor which targets ERK5 and other kinases, inhibited cell proliferation by blocking passage of cells through G1 and G2, and also triggered apoptosis in certain TNBC cell lines. TG02 had significant antitumor activity in a TNBC xenograft model in vivo, and also augmented the activity of chemotherapeutic agents commonly used to treat TNBC. Together, these data indicate that ERK5 targeting may represent a valid strategy against TNBC, and support the development of trials aimed at evaluating the clinical effectiveness of drugs that block this kinase., This work was supported by a grant from the Instituto de Salud Carlos III (PS09/00868) and from the Consejería de Sanidad de la Junta de Castilla y León to AEO. MJOR was supported by Junta de Castilla y León and SAF by the Cancer Center Network Program from the ISCIII (RD06/0020/0041). Support by a grant from the Asociación de Mujeres “Santa Águeda” of Puertollano, Spain is acknowledged. Our Cancer Research Institute, and the work carried out at our laboratory receive support from the European Community through the regional development funding program (FEDER), and from the Fundación Ramón Areces.

The neuregulins (NRGs) are a family of EGF-like factors that activate receptor tyrosine kinases of the ErbB/HER type. Some NRGs are membrane anchored and are released upon cleavage of the ectodomain. Here we have investigated the characteristics of the cleavage of different transmembrane NRG isoforms (proNRG) that diverge in domains that have been implicated in the regulation of the cleavage of other membrane-anchored growth factors. We show that cleavage of proNRGs is complex and generates several cell-bound truncated fragments. Comparison of the resting generation of these truncated fragments between proNRG forms that diverge in the linker region that connects the EGF-like module to the transmembrane domain revealed that proNRGβ2a was relatively resistant to processing compared to proNRGβ4a which was processed more efficiently than proNRGα2a. An important role for this linker in proNRG cleavage was supported by deletion analysis of this region that prevented NRG solubilization. Studies aimed at the identification of the proteolytic machinery responsible for proNRG processing indicated that metalloproteases were involved in proNRG processing. This was further supported by the fact that cleavage of proNRGα2c was defective in fibroblasts derived from TACE(-/-) animals that express an inactive form of the metalloprotease TACE., We thank the funding from the European Community, the Fundación Ramón Areces, and the Spanish Ministry of Education and Culture. A.E.-O. was supported by a psotdoctoral contract from the Spanish Ministry of Education and Culture. E.D.-R. and L.Y were supported by a predoctoral fellowship from the same Ministry.

Alterations that affect the ectodomain of receptor tyrosine kinases are often associated with constitutive activation of the enzymic activity of the mutant cell-associated receptor. Since the ectodomain of the ErbB2 receptor tyrosine kinase has been detected as a soluble fragment in the culture supernatant of cells and serum from patients with advanced breast cancer, the possible presence of cell-associated truncated forms of ErbB2 in cancer cells was investigated. Several cell-bound N-terminal truncated forms of ErbB2 were identified in breast cancer cells overexpressing this receptor. The presence of the truncated fragments was independent of lysosomal/proteasomal activity, indicating that classical receptor tyrosine kinase degradation systems were not involved in the N-terminal cleavages. The presence of these truncated forms of ErbB2 was up-regulated by protein kinase C and neuregulin; and down-regulated by phosphatidylinositol 3-kinase, and monoclonal antibodies that target the ectodomain of ErbB2, indicating that N-terminal cleavages of ErbB2 were regulated by multiple mechanisms. The truncated fragments were tyrosine-phosphorylated under resting conditions, and associated with the signalling intermediates Shc and Grb2. It is therefore likely that these truncated forms may be endowed with constitutive activity that allows them to permanently signal.

Work in our lab was supported by grant PB94–0075 from the Spanish Ministry of Science and Education; by the BIOTECH Program (BIO4-CT96–0058) from the European Community; and by the Fundacion Ramon Areces. E.D.-R. was supported by a predoctoral fellowship from the Spanish Ministry of Science and Education; and N.C. holds a fellowship from the Scientific Foundation of the Spanish Association Against Cancer (AECC). A.E-O holds a postdoctoral contract from the Spanish Ministry of Education and Science.

Plasma cell leukemia (PCL) represents the most aggressive form of monoclonal gammopathy for which new treatment approaches are needed. Here we report the effect of Bortezomib on cells from 4 patients with PCL, as well as the in vivo efficacy on a patient with secondary PCL. Bortezomib reduced PCL numbers and was more efficient in cell growth inhibition than dexamethasone or doxorubicin. Treatment with Bortezomib induced procaspase-3 and poly(ADP-ribose) polymerase cleavage and decreased the amount of extracellular signal regulated kinase (Erk1/2) and phospho-Erk1/2. However, Bortezomib did not substantially affect the levels of the Erk1/2 upstream activating kinase (MEK1), p27 or p21. Finally, we had the opportunity to use Bortezomib in a heavily pretreated patient with overt secondary PCL and severe anemia and thrombocytopenia. Following Bortezomib treatment, circulating plasma cells disappeared; what is more striking, the peripheral blood counts returned to normal, becoming transfusion-independent. These data support the inclusion of Bortezomib in the therapeutic armamentarium of PCL.

Glioblastoma (GBM) is associated with infiltration of peritumoral (PT) parenchyma by isolated tumor cells that leads to tumor regrowth. Recently, GBM stem-like or initiating cells (GICs) have been identified in the PT area, but whether these GICs have enhanced migratory and invasive capabilities compared with GICs from the tumor mass (TM) is presently unknown. We isolated GICs from the infiltrated PT tissue and the TM of three patients and found that PT cells have an advantage over TM cells in two-dimensional and three-dimensional migration and invasion assays. Interestingly, PT cells display a high plasticity in protrusion formation and cell shape and their migration is insensitive to substrate stiffness, which represent advantages to infiltrate microenvironments of different rigidity. Furthermore, mouse and chicken embryo xenografts revealed that only PT cells showed a dispersed distribution pattern, closely associated to blood vessels. Consistent with cellular plasticity, simultaneous Rac and RhoA activation are required for the enhanced invasive capacity of PT cells. Moreover, Rho GTPase signaling modulators αVβ3 and p27 play key roles in GIC invasiveness. Of note, p27 is upregulated in TM cells and inhibits RhoA activity. Gene silencing of p27 increased the invasive capacity of TM GICs. Additionally, β3 integrin is upregulated in PT cells. Blockade of dimeric integrin αVβ3, a Rac activator, reduced the invasive capacity of PT GICs in vitro and abrogated the spreading of PT cells into chicken embryos. Thus, our results describe the invasive features acquired by a unique subpopulation of GICs that infiltrate neighboring tissue.

Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer. Despite response to chemotherapy, relapses are frequent and resistance to available treatments is often seen in the metastatic setting. Therefore, identification of new therapeutic targets is required. With this aim, we have profiled the activation status of 44 receptor tyrosine kinases (RTKs) and their major signaling pathways in patient-derived TNBC tumors. Frequent co-activation of several RTKs as well as the extracellular signal-regulated protein kinases 1 and 2 (Erk1/2) and mammalian target of rapamycin (mTOR) routes was found. Pharmacologic targeting of the activated kinases indicated that agents that attack the mTOR route are more potent and efficient antitumoral treatments than agents targeting RTKs. mTOR signals through two multiprotein complexes, mTORC1 and mTORC2. We used a genetic approach to explore the contribution of each of the two mTOR branches to the regulation of cell number of TNBC cells. RNA interference experiments indicated that mTORC1 predominated over mTORC2 in the control of TNBC cell proliferation. Moreover, RNA interference of mTOR had a superior antiproliferative action than separately acting on mTORC1 or mTORC2. To analyze the relevance of mTOR targeting in vivo, we used mice with TNBC. Treatment of these mice with BEZ235, a drug that targets mTOR, slowed tumor growth. Mechanistically, BEZ235 delayed cell cycle progression without affecting cell viability. Our results show that TNBCs are particularly sensitive to inhibition of the mTOR pathway, and indicate that mTOR targeting may be a more efficient anti-TNBC therapy than exclusively acting on the mTORC1 branch of the pathway. This is relevant as most mTOR inhibitors used in the clinic act on mTORC1. Collectively with the fact that BEZ235 synergized with drugs commonly used in the treatment of TNBC, our data support the clinical development of agents that act on mTOR as a therapy for this disease., This work was supported by grants from the Ministry of Science and Innovation of Spain (BFU2009–07728/BMC to AP, and PS09/00868 to AE-O). JCM and SS were supported by the Cancer Center Network Program from the ISCIII (RD06/0020/0041). The Cancer Research Institute, and the work carried out at AP and AE-O laboratories, receive support from the European Community through the regional development funding program (FEDER), and from the Fundación Ramón Areces. AO receives research support from the FISCAM (Grant PI2010/017) and from the ISCIII (Grant PS09/02144).

Background Breast cancer is the most common neoplasia in women. Even though advances in its treatment have improved disease outcome, some patients relapse. Therefore, attempts to better define the molecular determinants that drive breast cancer cell proliferation may help in defining potential therapeutic targets. Mitogen-activated protein kinases (MAPK) play important roles in tumorigenesis. One of them, Erk5, has been linked to the proliferation of breast cancer cells in vitro. Here we have investigated the expression and prognostic value of Erk5 in human breast cancer. Methodology/Principal Findings Animal and cellular models were used to study Erk5 expression and function in breast cancer. In 84 human breast tumours the expression of Erk5 was analyzed by immunohistochemistry. Active Erk5 (pErk5) was studied by Western blotting. Correlation of Erk5 with clinicopathological parameters and with disease-free survival in early stage breast cancer patients was analyzed. Expression of Erk5 was detected in most patients, and overexpression was found in 20%. Active Erk5 was present in a substantial number of samples, as well as in tumours from an animal breast cancer model. Overexpression of Erk5 was associated with a decrease in disease-free survival time, which was independent of other clinicopathological parameters of prognosis. Transient transfection of a short hairpin RNA (shRNA) targeting Erk5, and a stable cell line expressing a dominant negative form of Erk5 (Erk5AEF), were used to investigate the influence of Erk5 on drugs used in the clinic to treat breast tumours. We found that inhibition of Erk5 decreased cancer cell proliferation and also sensitized these cells to the action of anti-HER2 therapies. Conclusions/Significance Overexpression of Erk5 is an independent predictor of disease-free survival in breast cancer, and may represent a future therapeutic target.

10 páginas, 6 figuras.-- This is an open-access article distributed under the terms of the Creative Commons Attribution License.-- et al., Resistance to Imatinib Mesylate (IM) is a major problem in Chronic Myelogenous Leukaemia management. Most of the studies about resistance have focused on point mutations on BCR/ABL. However, other types of resistance that do not imply mutations in BCR/ABL have been also described. In the present report we aim to study the role of several MAPK in IM resistance not associate to BCR/ABL mutations. Therefore we used an experimental system of resistant cell lines generated by co-culturing with IM (K562, Lama 84) as well as primary material from resistant and responder patient without BCR/ABL mutations. Here we demonstrate that Erk5 and p38MAPK signaling pathways are not implicated in the acquired resistance phenotype. However, Erk2, but not Erk1, is critical for the acquired resistance to IM. In fact, Bcr/Abl activates preferentially Erk2 in transient transfection in a dose dependent fashion through the c-Abl part of the chimeric protein. Finally, we present evidences demonstrating how constitutive activation of Erk2 is a de novo mechanism of resistance to IM. In summary our data support the use of therapeutic approaches based on Erk2 inhibition, which could be added to the therapeutic armamentarium to fight CML, especially when IM resistance develops secondary to Erk2 activation., This work was supported by grants from Fundación Mutua Madrileña del Automóvil, Fundación Leticia Castillejo Castillo and Ministerio de Educación y Ciencia. (SAF/2006/0179 and BFU2006-01813/BMC). RSP and AP Research Institutes, and the work carried out in their laboratories receive support from the European Community through the regional development funding program (FEDER). AEO is supported by the ISCIII (PI061552 and CP04/00045 contract).

The neuregulins represent the largest subclass of polypeptide factors of the epidermal growth factor family of ligands. These molecules are synthesized as membrane-bound, biologically active growth factors that act by binding to the HER/ErbB receptor tyrosine kinases. Preclinical data have indicated that increased expression and function of neuregulins may provoke cancer. Furthermore, neuregulin expression has been detected in several neoplasias, and their presence may correlate with response to treatments that target the HER receptors such as trastuzumab. In addition, the neuregulins have also been implicated in resistance to anti-HER therapies. Therefore, targeting of the neuregulins may be helpful in neoplastic diseases in which these polypeptide factors contribute to tumor generation and/or maintenance. © 2008 American Association for Cancer Research., Grant support: Ministry of Science and Education of Spain (BFU2006-01813/ BMC) and an Institutional Cancer Center Network program from the ISCIII (RD06/ 0020/0041), the Scientific Foundation of the Spanish Association for Cancer Research (J.C. Montero), a fellowship from the Ministry of Science and Education (R. Rodríguez-Barrueco), the Instituto de Salud Carlos III (A. Esparís-Ogando), and the I3PProgramfrom the CSIC (E. Díaz-Rodríguez). Our Cancer Research Institute, and the work carried out at our laboratory, receives support from the European Community through the regional development funding program (FEDER).

Purpose Human epidermal growth factor receptor 2 (HER-2) overexpression has been associated with the genesis and progression of a subset of breast cancers. The function of HER-2 may be upregulated by overexpression or by the availability of neuregulins (NRGs), a group of transmembrane growth factors. Transmembrane NRGs strongly activated HER-2 and cell proliferation in breast cancer cells that did not overexpress HER-2, and treatment with trastuzumab prevented the proliferative action of transmembrane NRG. This raised the relevant clinical question of whether patients considered as HER-2 negative, but expressing transmembrane NRG, may benefit from treatment with trastuzumab. Patients and Methods MCF7 cells expressing transmembrane NRG (MCF7-NRGα2c) were injected into mice, and their sensitivity to trastuzumab was assessed. A retrospective study of 124 patients with early-stage or metastatic breast cancer was conducted. Expression of transmembrane NRG was evaluated by immunohistochemistry. In 11 patients, Western blot for NRGs was also carried out. Statistics were performed to analyze possible correlations between NRG expression and response to trastuzumab-based therapies, event-free survival, and overall survival (OS). Results Trastuzumab inhibited tumor growth in mice injected with MCF7-NRGα2c cells. Transmembrane NRG was frequently expressed in breast cancer patients. Overexpression of transmembrane NRG significantly correlated with a longer event-free survival and OS in patients with low or normal HER-2 expression who were treated with trastuzumab-based therapies but not in patients with HER-2 overexpression. Conclusion We suggest that the spectrum of patients who may benefit from trastuzumab-based therapies may be widened to include patients with metastatic breast cancer without HER-2 amplification but who express transmembrane NRGs.

Nucleocytoplasmic shuttling of multiple signalling proteins is critical in the control of processes such as cell proliferation, differentiation, or apoptosis. One group of proteins whose activity depends on this nucleocytoplasmic traffic includes the mitogen-activated protein kinases. Usually, these kinases reside in the cytoplasm and move to the nucleus upon dual phosphorylation. One of these kinases, Erk5, has been found to reside in the nucleus of breast cancer cells that overexpress the ErbB2 receptor. This raises questions with respect to the mechanisms implicated in Erk5 nuclear location in these cells, as well as the biological consequences of this nuclear residency. In breast cancer cells overexpressing ErbB2, Erk5 dual phosphorylation required ErbB2 tyrosine kinase activity; however, Erk5 nuclear residency did not require ErbB2 activity. Furthermore, translocation of Erk5 from the cytosol to the nucleus occurred in the absence of dual phosphorylation. Nuclear residency of Erk5 in these cells depended on the integrity of a nuclear localization signal present in the unique C-terminus of Erk5. The Erk5 form expressed by these breast cancer cells included the N- and C-terminal cytoplasmic targeting signals, yet Erk5 was nuclear, and remained at this location throughout the interphase without being tightly bound to DNA. Biological studies using a mutant Erk5 that accumulates in the nucleus indicate that nuclear Erk5 favours MEF2-dependent transcriptional activity, and inhibits TRAIL-induced cell death. © 2007 Elsevier Inc. All rights reserved., This work was supported by grants from the Ministry of Science and Technology of Spain (BMC2003-01192 and BFU2006-01813/BMC), and by an Institutional Cancer Center Network program from the ISCIII. AEO was initially supported by the Scientific Foundation of the Spanish Association for Cancer Research (AECC), and later by the Instituto de Salud Carlos III (PI061552 and CP04/00045). JB was supported by a Fundação para a Ciência e a Tecnologia (FCT/FSEIII), Quadro Comunitário de Apoio. Our Cancer Research Institute, and the work carried out at our laboratory, receive support from the European Community through the regional development funding program (FEDER).

The neuregulins (NRGs) play important roles in animal physiology, and their disregulation has been linked to diseases such as cancer or schizophrenia. The NRGs may be produced as transmembrane proteins (proNRGs), even though they lack an N-terminal signal sequence. This raises the question of how NRGs are sorted to the plasma membrane. It is also unclear whether in their transmembrane state, the NRGs are biologically active. During studies aimed at solving these questions, we found that deletion of the extracellular juxtamembrane region termed the linker, decreased cell surface exposure of the mutant proNRG ΔLinker, and caused its entrapment at the cis-Golgi. We also found that cell surface-exposed transmembrane NRG forms retain biological activity. Thus, a mutant whose cleavage is impaired but is correctly sorted to the plasma membrane activated ErbB receptors in trans and also stimulated proliferation. Because the linker is implicated in surface sorting and the regulation of the cleavage of transmembrane NRGs, our data indicate that this region exerts multiple important roles in the physiology of NRGs. © 2007 by The American Society for Cell Biology., This work was supported by a grant from the Ministry of Science and Technology of Spain (BMC2003-01192). R.R.-B. and L.Y. were supported by fellowships from the Ministry of Education and Culture, and A.E.O. was initially supported by the Scientific Foundation of the Spanish Association for Cancer Research (AECC), and later by the Instituto de Salud Carlos III. J.B. was supported by a Fundaçcâo para a Ciência e a Tecnologia (FCT/FSEIII), Quadro Comunitario de Apoio III.

7 Figures, Multiple myeloma is characterized by the accumulation of terminally differentiated B cells in the bone marrow, due to increased proliferation and restricted apoptosis of the myelomatous clone. Here we have studied the participation of a novel mitogen-activated protein kinase (MAPK) route, the extracellular signal-regulated kinase 5 (Erk5) pathway, in the regulation of myeloma cell proliferation and apoptosis. Erk5 was expressed in cells isolated from patients and in myeloma cell lines. The myeloma growth factor interleukin 6 (IL-6) activated Erk5, and this activation was independent of Ras and Src. Expression of a dominant-negative form of Erk5 restricted the proliferation of myeloma cells and inhibited IL-6–dependent cell duplication. This dominant-negative form also sensitized myeloma cells to the proapoptotic action of dexamethasone and PS341. The latter compound caused a profound decrease in the amount of endogenous Erk5 and was less effective in inducing apoptosis when the level of Erk5 was increased by transfection of Erk5. These results place the Erk5 route as a new regulatory signaling pathway that affects multiple myeloma proliferation and apoptosis., From the Centro de Investigación del Cáncer, CSIC-Universidad de Salamanca, Spain; Hospital Universitario de Salamanca, Spain; and Centro de Investigaciones Biológicas, Madrid, Spain.

The ligands of the epidermal growth factor family and their receptors, the ErbB proteins, have been linked to the development of different types of cancer. Particular attention has focused on ErbB2, whose activation may occur by receptor overexpression or by ligand-induced oligomerization with other ErbB receptors. Whether these two modes of ErbB2 activation cause the same biological responses is unknown. Here, we uncovered important differences in the signaling, proliferation rates, and the response to anti-ErbB2 antibodies when comparing MCF7 cells expressing the ligand neuregulin, to MCF7 cells overexpressing ErbB2. Expression of neuregulin caused higher proliferation than ErbB2 overexpression. Transmembrane neuregulin expression was accompanied by constitutive activation of ErbB2, ErbB3, and ErbB4 receptors. ErbB2 overexpression caused tyrosine phosphorylation of ErbB2, whereas ErbB3 and ErbB4 were only slightly tyrosine phosphorylated. Autocrine transmembrane neuregulin also caused constitutive activation of several signaling pathways, such as the Erk1/2, Erk5, and Akt routes, which have been linked to breast cancer cell proliferation. Interestingly, expression of neuregulin increased p21 levels and this was required for the proliferation of MCF7 cells. Treatment with the anti-ErbB2 receptor antibody Herceptin had an inhibitory effect on proliferation only in cells expressing neuregulin but not on cells overexpressing ErbB2, and its inhibitory activity was accompanied by a decrease in p21. These results suggest that Herceptin may also be of help in the treatment of tumors in which neuregulin feeds the tumoral tissue. © 2005 American Association for Cancer Research., Grant support: FISS grant 01/1060, Ministry of Science and Technology of Spain grant BMC2003-01192, Ministry of Education and Culture (L. Yuste), and Scientific Foundation of the Spanish Association for Cancer Research, AECC (A. Esparís-Ogando).

Plasma cell leukemia (PCL) represents the most aggressive form of monoclonal gammopathy for which new treatment approaches are needed. Here we report the effect of Bortezomib on cells from 4 patients with PCL, as well as the in vivo efficacy on a patient with secondary PCL. Bortezomib reduced PCL numbers and was more efficient in cell growth inhibition than dexamethasone or doxorubicin. Treatment with Bortezomib induced procaspase-3 and poly(ADP-ribose) polymerase cleavage and decreased the amount of extracellular signal regulated kinase (Erk1/2) and phospho-Erk1/2. However, Bortezomib did not substantially affect the levels of the Erk1/2 upstream activating kinase (MEK1), p27 or p21. Finally, we had the opportunity to use Bortezomib in a heavily pretreated patient with overt secondary PCL and severe anemia and thrombocytopenia. Following Bortezomib treatment, circulating plasma cells disappeared; what is more striking, the peripheral blood counts returned to normal, becoming transfusion-independent. These data support the inclusion of Bortezomib in the therapeutic armamentarium of PCL.

The ectodomain of certain transmembrane proteins can be released by the action of cell surface proteases, termed secretases. Here we have investigated how mitogen-activated protein kinases (MAPKs) control the shedding of membrane proteins. We show that extracellular signal-regulated kinase (Erk) acts as an intermediate in protein kinase C-regulated TrkA cleavage. We report that the cytosolic tail of the tumor necrosis factor α-converting enzyme (TACE) is phosphorylated by Erk at threonine 735. In addition, we show that Erk and TACE associate. This association is favored by Erk activation and by the presence of threonine 735. In contrast to the Erk route, the p38 MAPK was able to stimulate TrkA cleavage in cells devoid of TACE activity, indicating that other proteases are also involved in TrkA shedding. These results demonstrate that secretases are able to discriminate between the different stimuli that trigger membrane protein ectodomain cleavage and indicate that phosphorylation by MAPKs may regulate the proteolytic function of membrane secretases.