Calcium-binding protein 7 expressed in muscle negatively regulates age-related degeneration of neuromuscular junctions in mice.

The neuromuscular junction (NMJ) forms centrally in myotubes and, as the only synapse between motor neuron and myotube, are indispensable for motor activity. The midmuscle formation of NMJs, including midmuscle-restricted expression of NMJ-related genes, is governed by the muscle-specific kinase (MuSK). However, mechanisms underlying MuSK-mediated signaling are unclear. Here, we find that the Calcium-binding protein 7 (Cabp7) gene shows midmuscle-restricted expression, and muscle-specific depletion of Cabp7 in mice accelerated age-related NMJ degeneration, muscle weakness/atrophy, and motor dysfunction. Surprisingly, forced expression in muscle of CIP, an inhibitory peptide of the negative regulator of NMJ formation cyclin-dependent kinase 5 (Cdk5), restored NMJ integrity and muscle strength, and healed muscle atrophy in muscle-specific Cabp7-deficient mice, which showed increased muscle expression of the Cdk5 activator p25. These findings together demonstrate that MuSK-mediated signaling induces muscle expression of Cabp7, which suppresses age-related NMJ degeneration likely by attenuating p25 expression, providing insights into prophylactic/therapeutic intervention against age-related motor dysfunction.

Moyamoya disease patient mutations in the RING domain of RNF213 reduce its ubiquitin ligase activity and enhance NFκB activation and apoptosis in an AAA+ domain-dependent manner.

Moyamoya disease (MMD) is a cerebrovascular disease characterized by progressive occlusion of the internal carotid arteries. Genetic studies originally identified RNF213 as an MMD susceptibility gene that encodes a large 591 kDa protein with a functional RING domain and dual AAA+ ATPase domains. As the functions of RNF213 and its relationship to MMD onset are unknown, we set out to characterize the ubiquitin ligase activity of RNF213, and the effects of MMD patient mutations on these activities and on other cellular processes. In vitro ubiquitination assays, using the RNF213 RING domain, identified Ubc13/Uev1A as a key ubiquitin conjugating enzyme that together generate K63-linked polyubiquitin chains. However, nearly all MMD patient mutations in the RING domain greatly reduced this activity. When full-length proteins were overexpressed in HEK293T cells, patient mutations that abolished the ubiquitin ligase activities conversely enhanced nuclear factor κB (NFκB) activation and induced apoptosis accompanied with Caspase-3 activation. These induced activities were dependent on the RNF213 AAA+ domain. Our results suggest that the NFκB- and apoptosis-inducing functions of RNF213 may be negatively regulated by its ubiquitin ligase activity and that disruption of this regulation could contribute towards MMD onset.

Overexpression of Dok-7 in skeletal muscle enhances neuromuscular transmission with structural alterations of neuromuscular junctions: Implications in robustness of neuromuscular transmission.

Neuromuscular junctions (NMJs) are cholinergic synapses characterized by ultrastructural specializations, including the presynaptic active zones, the acetylcholine (ACh) release sites of the motor nerve terminal, and the postsynaptic junctional folds of muscle membrane, where ACh receptors (AChRs) cluster for efficient neuromuscular transmission. The formation and maintenance of NMJs are governed by the muscle-specific receptor tyrosine kinase MuSK. We had previously demonstrated that the muscle cytoplasmic protein Dok-7 is an essential activator of MuSK, and its activation and NMJ formation are enhanced in the Dok-7 transgenic (Tg) mice, in which Dok-7 is specifically overexpressed in skeletal muscle. Although Dok-7 Tg mice develop abnormally large NMJs but show normal motor function, the forced expression of Dok-7 in the muscle improves impaired motor activity in mouse models of neuromuscular disorders with NMJ defects. However, the effect of Dok-7 overexpression in skeletal muscle on ultrastructure and neuromuscular transmission of NMJs is yet to be studied. Here, we investigated the structural and electrophysiological properties of NMJs in the diaphragm muscle of 8-week-old Dok-7 Tg mice. The areas of the presynaptic motor nerve terminals and postsynaptic muscle membrane of NMJs were 2.7 and 4.3 times greater in Dok-7 Tg mice than in WT mice, respectively. Electrophysiological analyses revealed that neuromuscular transmission via NMJs in Dok-7 Tg mice was significantly enhanced but not proportionally with the increased size of the synaptic contact. Consistent with this, the densities of active zones and synaptic vesicles (ACh carriers) in the presynaptic motor nerve terminals were reduced. In addition, the density and size of postsynaptic junctional folds in the muscle membrane were also reduced. Moreover, terminal Schwann cells exhibited significantly greater penetration of their processes into the synaptic clefts, which connect the pre- and post-synaptic specializations. Together, our findings demonstrate that transgenic overexpression of Dok-7 in the skeletal muscle enhances neuromuscular transmission with significant enlargement and ultrastructural alterations of NMJs, the latter of which might prevent toxic overactivation of AChRs at the abnormally enlarged NMJs.

DOK7 gene therapy enhances motor activity and life span in ALS model mice.

Amyotrophic lateral sclerosis (ALS) is a progressive, multifactorial motor neurodegenerative disease with severe muscle atrophy. The glutamate release inhibitor riluzole is the only medication approved by the FDA, and prolongs patient life span by a few months, testifying to a strong need for new treatment strategies. In ALS, motor neuron degeneration first becomes evident at the motor nerve terminals in neuromuscular junctions (NMJs), the cholinergic synapse between motor neuron and skeletal muscle; degeneration then progresses proximally, implicating the NMJ as a therapeutic target. We previously demonstrated that activation of muscle-specific kinase MuSK by the cytoplasmic protein Dok-7 is essential for NMJ formation, and forced expression of Dok-7 in muscle activates MuSK and enlarges NMJs. Here, we show that therapeutic administration of an adeno-associated virus vector encoding the human DOK7 gene suppressed motor nerve terminal degeneration at NMJs together with muscle atrophy in the SOD1-G93A ALS mouse model. Ultimately, we show that DOK7 gene therapy enhanced motor activity and life span in ALS model mice.

[Molecular mechanisms underlying the formation and maintenance of neuromuscular junctions and a possible therapeutic approach.]

The mammalian neuromuscular junction(NMJ), a cholinergic synapse between a motor neuron and a skeletal muscle fiber, is essential for neural control of muscle contraction. Impaired formation and/or maintenance of NMJs results in disorders of neuromuscular transmission such as myasthenia gravis(MG)and congenital myasthenic syndromes(CMSs). The formation and maintenance of NMJs are orchestrated by the muscle-specific receptor tyrosine kinase MuSK. Activation of MuSK involves its essential cytoplasmic activator Dok-7, the MuSK co-receptor Lrp4, and the motor neuron-derived MuSK activator agrin. Indeed, CMS-associated mutations are identified in the genes encoding these 4 proteins, and autoantibodies against MuSK, Lrp4, or agrin are found in MG patients, demonstrating the pathophysiological significance of the MuSK activation machinery. However, Lrp4 and agrin also play crucial roles separate from MuSK activation in NMJ formation and maintenance. Based on the finding that forced expression of Dok-7 in muscle activates MuSK and enlarges NMJs, we recently developed DOK7 gene therapy as a therapy aimed at enlarging the NMJ, which has potential for treating various neuromuscular disorders with defective NMJ structure.

The carboxyl-terminal region of Dok-7 plays a key, but not essential, role in activation of muscle-specific receptor kinase MuSK and neuromuscular synapse formation.

As the synapse between a motor neuron and skeletal muscle, the neuromuscular junction (NMJ) is required for muscle contraction. The formation and maintenance of NMJs are controlled by the muscle-specific receptor kinase MuSK. Dok-7 is the essential cytoplasmic activator of MuSK, and indeed mice lacking Dok-7 form no NMJs. Moreover, DOK7 gene mutations underlie DOK7 myasthenia, an NMJ synaptopathy. Previously, we failed to detect MuSK activation in myotubes by Dok-7 mutated in the N-terminal pleckstrin homology (PH) or phosphotyrosine binding (PTB) domain or that lacked the C-terminal region (Dok-7-ΔC). Here, we found by quantitative analysis that Dok-7-ΔC marginally, but significantly, activated MuSK in myotubes, unlike the PH- or PTB-mutant. Purified, recombinant Dok-7-ΔC, but not other mutants, also showed marginal ability to activate MuSK's cytoplasmic portion, carrying the kinase domain. Consistently, forced expression of Dok-7-ΔC rescued Dok-7-deficient mice from neonatal lethality caused by the lack of NMJs, indicating restored MuSK activation and NMJ formation. However, these mice showed only marginal activation of MuSK and died by 3 weeks of age apparently due to an abnormally small number and size of NMJs. Thus, Dok-7's C-terminal region plays a key, but not fully essential, role in MuSK activation and NMJ formation.

Postnatal knockdown of dok-7 gene expression in mice causes structural defects in neuromuscular synapses and myasthenic pathology.

The neuromuscular junction (NMJ) is a synapse between a motor neuron and skeletal muscle and is required for muscle contraction. The formation and maintenance of NMJs are governed by the muscle-specific receptor tyrosine kinase MuSK. We previously showed that the muscle cytoplasmic protein Dok-7 is an essential activator of MuSK. Indeed, mice lacking either Dok-7 or MuSK form no NMJs, and defects in the human DOK7 gene underlie a congenital myasthenic syndrome (an NMJ disorder). However, it remains unproven whether Dok-7 is required for the postnatal maintenance of NMJs. In this study, we generated recombinant adeno-associated virus (AAV) vectors encoding short hairpin RNAs targeting the mouse dok-7 gene (AAV-shD7). Systemic administration of AAV-shD7 into 2-week-old mice down-regulated dok-7 expression in muscle and induced myasthenic symptoms including reduction in body weight and motor function. Moreover, AAV-shD7 treatment suppressed MuSK-dependent gene expression of NMJ components and reduced the size of NMJs. These results demonstrate that correct, physiological levels of dok-7 expression are required for the postnatal maintenance of NMJs.

The MuSK activator agrin has a separate role essential for postnatal maintenance of neuromuscular synapses.

The motoneural control of skeletal muscle contraction requires the neuromuscular junction (NMJ), a midmuscle synapse between the motor nerve and myotube. The formation and maintenance of NMJs are orchestrated by the muscle-specific receptor tyrosine kinase (MuSK). Motor neuron-derived agrin activates MuSK via binding to MuSK's coreceptor Lrp4, and genetic defects in agrin underlie a congenital myasthenic syndrome (an NMJ disorder). However, MuSK-dependent postsynaptic differentiation of NMJs occurs in the absence of a motor neuron, indicating a need for nerve/agrin-independent MuSK activation. We previously identified the muscle protein Dok-7 as an essential activator of MuSK. Although NMJ formation requires agrin under physiological conditions, it is dispensable for NMJ formation experimentally in the absence of the neurotransmitter acetylcholine, which inhibits postsynaptic specialization. Thus, it was hypothesized that MuSK needs agrin together with Lrp4 and Dok-7 to achieve sufficient activation to surmount inhibition by acetylcholine. Here, we show that forced expression of Dok-7 in muscle enhanced MuSK activation in mice lacking agrin or Lrp4 and restored midmuscle NMJ formation in agrin-deficient mice, but not in Lrp4-deficient mice, probably due to the loss of Lrp4-dependent presynaptic differentiation. However, these NMJs in agrin-deficient mice rapidly disappeared after birth, and postsynaptic specializations emerged ectopically throughout myotubes whereas exogenous Dok-7-mediated MuSK activation was maintained. These findings demonstrate that the MuSK activator agrin plays another role essential for the postnatal maintenance, but not for embryonic formation, of NMJs and also for the postnatal, but not prenatal, midmuscle localization of postsynaptic specializations, providing physiological and pathophysiological insight into NMJ homeostasis.

Neuromuscular disease. DOK7 gene therapy benefits mouse models of diseases characterized by defects in the neuromuscular junction.

The neuromuscular junction (NMJ) is the synapse between a motor neuron and skeletal muscle. Defects in NMJ transmission cause muscle weakness, termed myasthenia. The muscle protein Dok-7 is essential for activation of the receptor kinase MuSK, which governs NMJ formation, and DOK7 mutations underlie familial limb-girdle myasthenia (DOK7 myasthenia), a neuromuscular disease characterized by small NMJs. Here, we show in a mouse model of DOK7 myasthenia that therapeutic administration of an adeno-associated virus (AAV) vector encoding the human DOK7 gene resulted in an enlargement of NMJs and substantial increases in muscle strength and life span. When applied to model mice of another neuromuscular disorder, autosomal dominant Emery-Dreifuss muscular dystrophy, DOK7 gene therapy likewise resulted in enlargement of NMJs as well as positive effects on motor activity and life span. These results suggest that therapies aimed at enlarging the NMJ may be useful for a range of neuromuscular disorders.

Antitumor effect of 1, 8-cineole against colon cancer.

Several essential oils possess pharmacological effects. Among the various constituents of essential oils, 1, 8-cineole has been shown to possess pharmacological effects such as anti-bacterial and anti-inflammatory effects. The effect of 1, 8-cineole on human colorectal cancer cells, however, has not reported previously. In this study, we have investigated the anti-proliferative effect of 1, 8-cineole on human colon cancer cell lines HCT116 and RKO by WST-8 and BrdU assays. The cytotoxicity of 1, 8-cineole was investigated by LDH activity and TUNEL staining. The mechanism of apoptosis by 1, 8-cineole was determined by western blot analyses. In in vivo study, RKO cells were injected into the SCID mice and the effect of 1, 8-cineole was investigated. Specific induction of apoptosis, not necrosis, was observed in human colon cancer cell lines HCT116 and RKO by 1, 8-cineole. The treatment with 1, 8-cineole was associated with inactivation of survivin and Akt and activation of p38. These molecules induced cleaved PARP and caspase-3, finally causing apoptosis. In xenotransplanted SCID mice, the 1, 8-cineole group showed significantly inhibited tumor progression compared to the control group. These results indicated 1, 8-cineole suppressed human colorectal cancer proliferation by inducing apoptosis. Based on these studies 1, 8-cineole would be an effective strategy to treat colorectal cancer.

Mesdc2 plays a key role in cell-surface expression of Lrp4 and postsynaptic specialization in myotubes.

Low-density lipoprotein receptor-related protein 4 (Lrp4) is essential for pre- and post-synaptic specialization at the neuromuscular junction (NMJ), an indispensable synapse between a motor nerve and skeletal muscle. Muscle-specific receptor tyrosine kinase MuSK must form a complex with Lrp4 to organize postsynaptic specialization at NMJs. Here, we show that the chaperon Mesdc2 binds to the intracellular form of Lrp4 and promotes its glycosylation and cell-surface expression. Furthermore, knockdown of Mesdc2 suppresses cell-surface expression of Lrp4, activation of MuSK, and postsynaptic specialization in muscle cells. These results suggest that Mesdc2 plays an essential role in NMJ formation by promoting Lrp4 maturation.

Phase II clinical study of modified FOLFOX7 (intermittent oxaliplatin administration) plus bevacizumab in patients with unresectable metastatic colorectal cancer-CRAFT study.

PURPOSE: Continuous treatment with FOLFOX therapy is associated with peripheral nerve toxicity, and to improve this inconvenient side effect various methods of administration are being investigated. A regimen of intermittent oxaliplatin administration by continuous infusion therapy, i.e., modified FOLFOX7 (mFOLFOX7) + bevacizumab, was designed with the goal of alleviating severe peripheral nerve disorders and hematological toxicity. A phase II clinical study was conducted to evaluate the efficacy and safety of this regimen. METHODS: Previously untreated patients were assigned to mFOLFOX7 (oxaliplatin 85 mg/m(2), levofolinate [l-LV] 200 mg/m(2), 5-fluorouracil [5-FU] 2400 mg/m(2)) + bevacizumab (5 mg/kg) administered every 2 weeks for 8 cycles, maintenance without oxaliplatin for 8 cycles, and reintroduction of mFOLFOX7 + bevacizumab for 8 cycles or until disease progression. Progression free survival (PFS) following the first dose (PFS 1) and following reintroduction of oxaliplatin (PFS 2) were used as indices for assessing the efficacy of intermittent administration. RESULTS: Fifty-two patients were enrolled, with median age of 64 years (range, 36-74). Median PFS 1 was 11.8 months (95 % confidence interval [CI], 9.5 to 13.7), median time to treatment failure was 10.3 months (95 % CI, 5.6 to 12.1), percentage of patients with neutropenia of grade 3 or higher was 7.8 %, and percentage with peripheral nerve disorders was 3.9 %. Response rate was 50 %, and 84.4 % of patients who started modified simplified LV5FU2 + bevacizumab were reintroduced to oxaliplatin. CONCLUSION: By excluding 5-FU bolus administration and administering bevacizumab continuously the mFOLFOX7 + bevacizumab regimen with preplanned withdrawal of oxaliplatin showed high tolerability and prevented severe peripheral neuropathy and neutropenia without reducing efficacy.

Enhanced antitumor activity of cerulenin combined with oxaliplatin in human colon cancer cells.

Fatty acid synthase is highly expressed in many types of human cancers. Cerulenin, a natural inhibitor of fatty acid synthase, induced apoptosis in the human colon cancer cell lines HCT116 and RKO. Oxaliplatin also induced cell death in these cell lines. Cerulenin treatment was associated with reduced levels of phosphorylated Akt, activation of p38 and induced caspase-3 cleavage and finally caused apoptosis. Oxaliplatin induced activation of the p53-p21 pathway and p38. In combination with cerulenin and oxaliplatin, activation of the p53-p21 pathway and p38 occurred in a smaller concentration and finally induced caspase-3 cleavage in a smaller concentration of cerulenin and oxaliplatin. In xenotransplanted SCID mice, the cerulenin + oxaliplatin group significantly inhibited tumor progression compared to the control, cerulenin and oxaliplatin groups. Based on these studies, inhibiting fatty acid synthase would be an effective strategy to treat unresectable colorectal cancer tumors in combination with oxaliplatin. Fatty acid synthase inhibitor would be one of the best counterparts of oxaliplatin, which reduces the dose and side-effects of oxaliplatin and would make it possible to endure the chemotherapy over a longer period.

Protocadherin 17 regulates presynaptic assembly in topographic corticobasal Ganglia circuits.

Highly topographic organization of neural circuits exists for the regulation of various brain functions in corticobasal ganglia circuits. Although neural circuit-specific refinement during synapse development is essential for the execution of particular neural functions, the molecular and cellular mechanisms for synapse refinement are largely unknown. Here, we show that protocadherin 17 (PCDH17), one of the nonclustered δ2-protocadherin family members, is enriched along corticobasal ganglia synapses in a zone-specific manner during synaptogenesis and regulates presynaptic assembly in these synapses. PCDH17 deficiency in mice causes facilitated presynaptic vesicle accumulation and enhanced synaptic transmission efficacy in corticobasal ganglia circuits. Furthermore, PCDH17(-/-) mice exhibit antidepressant-like phenotypes that are known to be regulated by corticobasal ganglia circuits. Our findings demonstrate a critical role for PCDH17 in the synaptic development of specific corticobasal ganglia circuits and suggest the involvement of PCDH17 in such circuits in depressive behaviors.

Adaptor protein complex of FRS2ß and CIN85/CD2AP provides a novel mechanism for ErbB2/HER2 protein downregulation.

Overexpression of the ErbB2/HER2 receptor tyrosine kinase contributes to tumorigenesis. However, mechanisms regulating ErbB2 protein levels remain largely unclear. Here, we identified novel mechanisms of ErbB2 downregulation. ErbB2 constitutively binds to an adaptor protein FRS2ß. We found that FRS2ß bound to CD2AP and CIN85, which induces endosomal trafficking that targets lysosomes. FRS2ß colocalized with CIN85 in the cytoplasm. Expression of wild type FRS2ß but not its CIN85 non-binding mutant, downregulated the ErbB2 protein and inhibited anchorage-independent cell growth. Moreover, the E3 ubiquitin-protein ligase Cbl was contained within a complex of FRS2ß and CIN85. Knockdown of both CIN85 and CD2AP or of Cbl, or treatment with lysosomal degradation inhibitors diminished FRS2ß downregulation of ErbB2. In addition, knockdown of endogenous FRS2ß caused upregulation of ErbB2 in primary neural cells. Finally, immunohistochemical analysis showed that human breast cancer tissues that overexpress ErbB2 expressed low levels of FRS2ß. Thus, an FRS2ß-CIN85/CD2AP-Cbl axis for downregulation of ErbB2 may regulate ErbB2 protein levels in physiological and pathological settings. Molecular targeting drugs that can increase or stabilize the ErbB2-FRS2ß-CIN85/CD2AP-Cbl axis may have promise for the control of ErbB2-overexpressing tumors.

Structural flexibility regulates phosphopeptide-binding activity of the tyrosine kinase binding domain of Cbl-c.

Through their ubiquitin ligase activity, Cbl-family proteins suppress signalling mediated by protein-tyrosine kinases (PTKs), but can also function as adaptor proteins to positively regulate signalling. The tyrosine kinase binding (TKB) domain of this family is critical for binding with tyrosine-phosphorylated target proteins. Here, we analysed the crystal structure of the TKB domain of Cbl-c/Cbl-3 (Cbl-c TKB), which is a distinct member of the mammalian Cbl-family. In comparison with Cbl TKB, Cbl-c TKB showed restricted structural flexibility upon phosphopeptide binding. A mutation in Cbl-c TKB augmenting this flexibility enhanced its binding to target phosphoproteins. These results suggest that proteins, post-translational modifications or mutations that alter structural flexibility of the TKB domain of Cbl-family proteins could regulate their binding to target phosphoproteins and thereby, affect PTK-mediated signalling.

[Evaluation of modified OPTIMOX1 plus bevacizumab as the neoadjuvant therapy for highly advanced rectal cancers].

UNLABELLED: We evaluated the efficacy and safety of neoadjuvant chemotherapy using modified OPTIMOX1 plus bevacizumab for advanced rectal cancer. PATIENTS AND METHODS: Nine cases with highly advanced rectal cancer for which curative surgery was potentially difficult were enrolled(clinical T4 in 7 cases, lateral node metastasis in 3 cases, M1 in 2 cases). RESULTS: The number of courses of modified OPTIMOX1(mFOLFOX6 and sLV5FU2, alternating administration)plus bevacizumab ranged from 1 to 21(median: 10). Surgical procedures consisted of internal sphincter resection(ISR)in 4 patients, ultra-low anterior resection(ULAR)in 2 patients, pelvic exenteration(TPE)in 2 patients, and Hartmann's procedure in 1 patient. Liver resection was conducted in 2 patients. RM1 was confirmed in 2 patients, but curative surgery was performed in the other patients. Histological efficacy of grade x/1a/1b/2were seen in the above 1/4/2/2 cases, respectively. Neurotoxicity associated with oxaliplatin was mild; no grade 3 neurotoxicity was noted. Recurrence has been confirmed in 5 patients at the median follow-up period of 650 days. CONCLUSION: It was suggested that modified OPTIMOX1 plus bevacizumab is effective and safe to administer as a neoadjuvant chemotherapy for curative resection or anus-preserving surgery in patients with highly advanced rectal cancer.

NMDAR2B tyrosine phosphorylation is involved in thermal nociception.

Previous studies found that the NMDA receptor-mediated signaling regulates thermal nociception, though the underlying molecular mechanism remains unclear. The GluN2B subunit of the NMDA receptor is tyrosine-phosphorylated, Tyr-1472 being the major phosphorylation site. In this study, we have found that homozygous knock-in mice that express a Tyr-1472-Phe mutant of GluN2B display defects in the nociceptive response in the hot plate test. Expression of the neurotensin receptor subtype 2 (NTSR2), which is relevant to the regulation of thermal nociception, is decreased in the amygdala of GluN2B Tyr-1472-Phe knock-in mice. In addition, NTSR2-mediated c-fos induction is impaired in the amygdala of these mice. These data suggest that Tyr-1472 phosphorylation on GluN2B is involved in thermal nociception through regulating the NTSR2 mRNA expression in the amygdala.

Activation of receptor protein-tyrosine kinases from the cytoplasmic compartment.

It is widely accepted that receptor protein-tyrosine kinases (RTKs) are activated upon dimerization by binding to their extracellular ligands. However, EGF receptor (EGFR) dimerization per se does not require ligand binding. Instead, its cytoplasmic kinase domains have to form characteristic head-to-tail asymmetric dimers to become active, where one 'activator' domain activates the other 'receiver' domain. The non-catalytic, cytoplasmic regions of RTKs, namely the juxtamembrane and carboxy terminal portions, also regulate kinase activity. For instance, the juxtamembrane region of the RTK MuSK inhibits the kinase domain probably together with a cellular factor(s). These findings suggest that RTKs could be activated by cytoplasmic proteins. Indeed, Dok-7 and cytohesin have recently been identified as such activators of MuSK and EGFR, respectively. Given that failure of Dok-7 signaling causes myasthenia, and inhibition of cytohesin signaling reduces the proliferation of EGFR-dependent cancer cells, cytoplasmic activators of RTKs may provide new therapeutic targets.