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Biomechanical stress induces IL-6 expression in smooth muscle cells via Ras/Rac1-p38 MAPK-NF-kappaB signaling pathways.

IL-6, a proinflammatory cytokine, has been implicated in the development of vascular diseases. We previously demonstrated that mechanical stress can initiate signaling pathways leading to smooth muscle cell (SMC) proliferation and apoptosis, but little is known concerning cyclic stress-induced inflammatory response. To explore the role of stretch in the upregulation of cytokine expression in SMCs we performed RNase protection assay for a panel of cytokines and found that mechanical stress resulted in a time-dependent induction of IL-6 mRNA but not other cytokines, e.g., IL-1alpha, IL-1beta, IL-6, IL-10, IL-12p35, IL-12p40, IL-18, IFN-gamma, and macrophage migration inhibitory factor (MIF). This induction also correlated with elevated IL-6 protein levels in the supernatant. Pretreatment of the cells with NF-kappaB inhibitors inhibited NF-kappaB activity and resulted in marked inhibition (50%) of IL-6 protein. Moreover, SMC lines stably expressing dominant-negative Ras (RasN17) or Rac (RacN17) exhibited a remarkable decrease in p38 MAPK activity and IL-6 mRNA induction by mechanical stress. Furthermore, a significant inhibition of 30 and 40% in IL-6 protein was observed in SMCs pretreated with inhibitors of p38 MAPK and ERK1/2, respectively, but not JNK. Interestingly, SMCs isolated from PKC-delta-deficient mice exhibited higher levels of IL-6 compared with wild-type cells. Finally, high levels of IL-6 expression were observed in atherosclerotic lesions of vein bypass grafts, which are related to altered biomechanical stress. Our findings demonstrate that biomechanical stress-induced IL-6 expression occurs via a mechanism that involves Ras/Rac/p38 MAPK/NF-kappaB/NF-IL6 signaling pathways, which is downregulated by PKC-delta, and suggest that modulation of this event contributes to the pathogenesis of atherosclerosis.

Animals↗

Is leptin a mediator of adverse prognostic effects of obesity in breast cancer?

PURPOSE: Leptin, an adipocyte-derived cytokine that is elevated in obesity, has been associated with carcinogenesis, tumor migration and invasion, enhancement of angiogenesis, and increased aromatase activity. It has been suggested that leptin may mediate adverse prognostic effects of obesity in breast cancer. PATIENTS AND METHODS: Four hundred seventy-one women with surgically resected T1-3, N0-1, M0 breast cancer were studied. Leptin was assayed in stored fasting blood specimens obtained before adjuvant therapy. Women were followed prospectively for distant disease-free survival (DDFS) and overall survival (OS). RESULTS: Patients ranged from 26 to 74 years of age, and staging was as follows: T1 = 262, T2 = 151, T3 = 23, TX = 35, N0 = 323, and N1 = 148. Estrogen receptor was positive in 286 patients, and progesterone receptor was positive in 259 patients. One hundred forty-five patients received adjuvant chemotherapy, 146 received adjuvant tamoxifen, 46 received both, and 134 received neither. Mean leptin was 15.2 +/- 10.1 ng/mL. Univariately, leptin was associated with OS (overall P = .049; P = .014 postmenopausal). Leptin was not associated with DDFS overall or in any menopausal subgroup (P > or = .19). In multivariate Cox modeling, leptin was not significantly associated with DDFS or OS (P = .11 and 0.075, respectively). Adjustment for insulin or body mass index further reduced the association of leptin with outcome. CONCLUSION: Although leptin is strongly correlated with obesity and insulin, we could not show that it is independently associated with prognosis in early-stage breast cancer. Because we cannot rule out modest prognostic effects, we recommend additional research to explore this potential association, particularly in postmenopausal women.

Adult↗

Fooling a freshwater fish: how dietary salt transforms the rainbow trout gill into a seawater gill phenotype.

Numerous fish species, including rainbow trout (Oncorhynchus mykiss), are able to inhabit both freshwater and seawater and routinely migrate between the two environments. One of the most critical adjustments allowing such successful migrations is a remodelling of the gill in which a suite of morphological and molecular changes ensure optimal function in the face of reversing requirements for salt and water balance. The remodelling leads to specific freshwater and seawater gill phenotypes that are readily identified by the orientation and/or quantities of specific ion transporters and the presence or absence of specific cell types. The proximate cues promoting gill phenotypic plasticity are unknown. Here, by assessing the consequences of a salt-enriched diet (in the absence of any changes in external salinity) in the freshwater rainbow trout, we demonstrate that internal salt loading alone, is able to induce various elements of the seawater gill phenotype. Specifically, we show upregulation of three ion transport genes, cystic fibrosis transmembrane conductance regulator (CFTR), Na(+)/K(+)/2Cl(-) co-transporter (NKCC1) and Na(+)/K(+)-ATPase, which are essential for ionic regulation in seawater, and the appearance of chloride cell-accessory cell complexes, which are normally restricted to fish inhabiting seawater. These data provide compelling evidence that gill remodelling during migration from freshwater to seawater may involve sensing of elevated levels of internal salt.

Animal Feed↗

Endothelial microparticles as markers of endothelial dysfunction.

Endothelial microparticles (EMP) are small vesicles released from disturbed endothelial cells (EC). Owing to the central importance of EC injury in thrombotic and inflammatory conditions, assay of EMP as a marker of EC disturbance has come under intensive development by several laboratories. The review begins with established markers of EC injury, commonly soluble markers such as intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin, von Willebrand factor (vWF), etc., pointing out that many of these are in fact mixtures of true soluble molecules with membrane-bound forms, for example, EMP. Assays of EMP from different labs are reviewed and standardization of assay is recommended. EMP are heterogeneous: those released in activation vs. apoptosis are distinctive in phenotypic markers and procoagulant properties. Application of EMP phenotype analysis can distinguish EC state of activation from apoptosis. Some EMP carry functional vWF with properties different from soluble vWF. Certain EMP bind to and activate monocytes; EMP-monocyte conjugates were found to be a marker of inflammatory disease such as multiple sclerosis (MS), and to enhance transendothelial migration of leukocytes in vitro. Clinical studies have revealed elevated plasma levels of EMP in lupus anticoagulant (LA), multiple sclerosis (MS), thrombotic thrombocytopenic purpura (TTP), coronary artery disease (CAD), hypertension, preeclampsia, and diabetes. Further refinement of EMP assay could open new windows for evaluating and monitoring endothelial injury in thrombotic and inflammatory disorders.

Biomarkers↗

The incidence and clinical characteristics of bronchiolitis obliterans organizing pneumonia syndrome after radiation therapy for breast cancer.

STUDY OBJECTIVE: Bronchiolitis obliterans organizing pneumonia (BOOP) syndrome after adjuvant radiation therapy for breast cancer has been recently recognized. However, the precise incidence of this syndrome remains to be determined. The aim of this study was to clarify the incidence and clinical characteristics of radiation-induced BOOP syndrome. METHODS: We conducted a retrospective analysis of 206 consecutive patients wit breast cancer undergoing tangential-field radiation therapy at our institution from 1992 to 2002. RESULTS: Among the patients, five (2.4%) developed BOOP syndrome. These five patients began with flu-like symptoms 2-7 months after the completion of radiation therapy. Four of them had received tamoxifen, an estrogen receptor antagonist, and the other one underwent cytotoxic chemotherapy. Their chest radiographs revealed peripheral alveolar opacities with migration outside the irradiated fields. Increased lymphocyte counts and elevated CD4/CD8 ratios were observed in the bronchoalveolar lavage fluid. Transbronchial biopsy revealed organizing pneumonia. The serum levels of KL-6, a marker of interstitial pneumonia, did not increase in any patients. Treatment with corticosteroids resulted in a rapid improvement, but two patients relapsed after the cessation of corticosteroids. CONCLUSIONS: These results suggest that BOOP syndrome after tangential-field radiation therapy for breast cancer is not rare and more attention should be directed to this condition as a radiation-induced pulmonary toxicity.

Biopsy↗

Electromyographic study of the scapular rotators during arm abduction in the scapular plane.

In 20 healthy, young adult male subjects, the muscular activity of the upper, middle and lower trapezius and the lower digitations of the serratus anterior were studied electromyographically during arm abduction in the plane of the scapula. The patterns of electrical activity of the trapezius and lower serratus anterior muscles were observed to increase progressively during abduction of the arm; however, a plateau phase was demonstrated in all four of the muscle parts studied. Despite the presence of considerable individual variability, common trends were observed in muscular activity patterns. It is believed that the patterns of muscle activity may be closely related to mechanical factors such as scapulohumeral rhythm and a migrating scapular Instantaneous Centre of Rotation (ICR) during arm elevation.

Adolescent↗

Nocturnal elevation of plasma melatonin and urinary 5-hydroxyindoleacetic acid in young men: attempts at modification by brief changes in environmental lighting and sleep and by autonomic drugs.

In order to determine whether the human pattern of circulating melatonin resembles that previously described in lower animals, men 19-32 years old were exposed to a light-dark cycle with 14 hours of light per day (L:D 14:10). In whites and blacks, nocturnal (dark phase, sleeping) melatonin levels were almost always elevated to 0.05-0.1 ng/ml plasma compared with lower or undetectable levels during the day, measured by the tadpole bioassay. Thin-layer migration of bioactive material was identical to that for melatonin standard. A rhythm with nocturnal elevation of urinary 5-hydroxyindoleacetic acid (5-HIAA) was observed. Nocturnal (sleep phase) rise in blood melatonin (but not urinary 5-HIAA) continued during 21/2 day-night cycle lengths after the onset of constant light. Though the dark phase plasma melatonin rise was less marked after reversal of the sleep-wake cycle (no change in the light cycle), dark phase rise in urinary 5-HIAA continued. Though marked cardiovascular and other effects were produced by intravenous isoproterenol or scopolamine, no definite effect on melatonin levels was observed after either drug during the light phase in waking subjects.

Adult↗

Porewater evidence of metal (Cu, Ni, Co, Zn, Cd) mobilization in an acidic, ombrotrophic bog impacted by a smelter, Harjavalta, Finland and comparison with reference sites.

Porewaters were collected from three Finnish peat bogs subjected to varying inputs of atmospheric trace metals: Hietajärvi (HIJ), a low-background site, Outokumpu (OUT), near a Cu-Ni mine, and Harjavalta (HAR), near a Cu-Ni smelter. Samples for metal analyses were collected at depths ranging from 10 to 70 cm using a purpose-built syringe-type sampler. Metal concentrations were determined using inductively coupled plasma-sector field-mass spectrometry (ICP-SF-MS). Porewater concentrations at HIJ and OUT (Cd <0.3 nM, Co <1.4 nM, Cu, Ni <8 nM, Zn <250 nM) are independent of metal concentrations in the solid phase (peat). At OUT there is a limited release of Ni to the porewaters, but concentrations in the aqueous phase are generally below 0.3% of the total concentration in any given peat sample. These data are consistent with the immobility of these metals after deposition from the air. In contrast, porewaters at HAR are enriched in trace metals compared to the other sites by a factor of 2 (Zn), 10 (Cd), 20 (Co), and 100 (Cu and Ni) with dissolved fractions of Cu and Ni accounting for ca. 20% of the metal inventories in the cores. The elevated release of metals from solid phases at HAR is consistent with the postdepositional migration of metals at this site and reflects the predominance of oxide phases supplied to the bog surface and the much lower pH values (<3.4). The elevated proton concentrations not only promote mineral dissolution but also compete with cation exchange processes and hinder the formation of metal complexes with organic ligands.

Acids↗

Enhanced neutrophil migratory activity following major blunt trauma.

BACKGROUND: Neutrophil migration into the lung is a critical, but poorly understood step in the pathogenesis of post-traumatic, acute respiratory distress syndrome (ARDS). We investigated changes in interleukin-8 (IL-8) mediated neutrophil migration and associated changes in receptor expression, of the IL-8 receptors CXCR1, the integrins CD11b/CD18 and platelet endothelial cell adhesion molecule-1 (PECAM-1) in patients sustaining major trauma. METHODS: Eleven patients with major trauma, injury severity score (ISS), median 22 (range 18-41), were followed prospectively. Eleven normal volunteers were used as controls. Blood samples were obtained within 4+/-2 h of injury, at 24 h, day 3 and day 5. Neutrophils migration was assessed by an in vitro IL-8 assay and neutrophil surface receptor expression by FACS analysis. RESULTS: IL-8 mediated neutrophil migration was significantly increased on admission following major trauma and remained elevated for 3 days (p<0.05). This was associated with up-regulation of CXCR1 (p<0.01) and down-regulation of PECAM-1 (p<0.05). CD11b and CD18 although initially unchanged, became down-regulated on day 3 (p<0.05). CONCLUSIONS: These data show that major trauma primes circulating neutrophils for increased migration in response to IL-8. This response is sustained for 72 h and is associated with changes in neutrophil surface receptor expression.

Adult↗

An analysis of culmination in Dictyostelium using prestalk and stalk-specific cell autonomous markers.

The ecmA (pDd63) and ecmB (pDd56) genes encode extracellular matrix proteins of the slime sheath and stalk tube of Dictyostelium discoideum. Using fusion genes containing the promoter of one or other gene coupled to an immunologically detectable reporter, we previously identified two classes of prestalk cells in the tip of the migrating slug; a central core of pstB cells, which express the ecmB gene, surrounded by pstA cells, which express the ecmA gene. PstB cells lie at the position where stalk tube formation is initiated at culmination and we show that they act as its founders. As culmination proceeds, pstA cells transform into pstB cells by activating the ecmB gene as they enter the stalk tube. The prespore region of the slug contains a population of cells, termed anterior-like cells (ALC), which have the characteristics of prestalk cells. We show that the ecmA and ecmB genes are expressed at a low level in ALC during slug migration and that their expression in these cells is greatly elevated during culmination. Previous observations have shown that ALC sort to surround the prespore cells during culmination (Sternfeld and David, 1982 Devl Biol. 93, 111-118) and we find just such a distribution for pstB cells. We believe that the ecmB protein plays a structural role in the stalk tube and its presence, as a cradle around the spore head, suggests that it may play a further function, perhaps in ensuring integrity of the spore mass during elevation. If this interpretation is correct, then a primary role of anterior-like cells may be to form these structures at culmination. We previously identified a third class of prestalk cells, pstO cells, which lie behind pstA cells in the slug anterior and which appeared to express neither the ecmA nor the ecmB gene. Using B-galactosidase fusion constructs, which give more sensitive detection of gene expression, we now find that these cells express the ecmA gene but at a much lower level than pstA cells. We also show that expression of the ecmA gene becomes uniformly high throughout the prestalk zone when slugs are allowed to migrate in the light. Overhead light favours culmination and it may be that increased expression of the ecmA gene in the pst 'O' region is a preparatory step in the process.

Cell Movement↗

Immunological investigations in acute and chronic human pancreatitis.

Follow-up immunological studies in 27 patients with acute pancreatitis of known etiology showed a significant elevation in the level of circulating immune complexes (IC), a significant inhibition in migration of leukocytes (with direct LMT) of patients and a significant decrease in the percentage of T-active, T-total peripheral lymphocytes and in the absolute count of peripheral T cells. Elevated circulating IC levels could been detected 3-4 weeks after the onset of acute pancreatitis. These immunological changes have still been demonstrated in a number of patients 7-14 months after recovery. We have found similar immunological alterations in patients with chronic pancreatitis as well. The possible causes and role of these long-term existing immunologic abnormalities are discussed.

Adult↗

Hyperactivation of p21ras and PI3K cooperate to alter murine and human neurofibromatosis type 1-haploinsufficient osteoclast functions.

Individuals with neurofibromatosis type 1 (NF1) have a high incidence of osteoporosis and osteopenia. However, understanding of the cellular and molecular basis of these sequelae is incomplete. Osteoclasts are specialized myeloid cells that are the principal bone-resorbing cells of the skeleton. We found that Nf1(+/-) mice contain elevated numbers of multinucleated osteoclasts. Both osteoclasts and osteoclast progenitors from Nf1(+/-) mice were hyperresponsive to limiting concentrations of M-CSF and receptor activator of NF-kappaB ligand (RANKL) levels. M-CSF-stimulated p21(ras)-GTP and Akt phosphorylation was elevated in Nf1(+/-) osteoclasts associated with gains of function in survival, proliferation, migration, adhesion, and lytic activity. These gains of function are associated with more severe bone loss following ovariectomy as compared with that in syngeneic WT mice. Intercrossing Nf1(+/-) mice and mice deficient in class 1(A) PI3K (p85alpha) restored elevated PI3K activity and Nf1(+/-) osteoclast functions to WT levels. Furthermore, in vitro-differentiated osteoclasts from NF1 patients also displayed elevated Ras/PI3K activity and increased lytic activity analogous to those in murine Nf1(+/-) osteoclasts. Collectively, our results identify a what we believe to be a novel cellular and biochemical NF1-haploinsufficient phenotype in osteoclasts that has potential implications for the pathogenesis of NF1 bone disease.

Animals↗

MCP-1 levels are elevated in peritonitis fluid from CAPD patients due to secretion by peritoneal macrophages.

The migration of leukocytes, including polymorphonuclear neutrophils and monocytes, into the peritoneal cavity is a key event of intraperitoneal inflammation. We investigated the levels of two members of the chemokine family, interleukin 8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1), in the dialysate effluent of 18 continuous ambulatory peritoneal dialysis (CAPD) patients with peritonitis and compared them with chemokine levels in noninfected CAPD effluent. Being a major source of inflammatory cytokines, we also isolated peritoneal macrophages from peritonitis effluent to determine the mRNA expression directly after isolation. The mean (SEM) concentrations of IL-8 and MCP-1 were significantly higher in the effluent of peritonitis patients than in noninfected effluents MCP-1: 22.5 +/- (6.27) versus 0.37 +/- (0.1) ng/mL and IL-8: 2.39 +/- (1.15) versus 0.04 +/- (0.01) ng/mL. Northern blot analysis of isolated effluent macrophages revealed strong signals for MCP-1 and IL-8. Our findings showed that CAPD effluent from patients with peritonitis contains markedly elevated MCP-1 and IL-8 levels, suggesting that these chemokines participate in leukocyte recruitment during CAPD peritonitis. Isolation of mRNA of peritonitis-derived peritoneal macrophages revealed strong signals for MCP-1 and IL-8, suggesting that macrophages are a major source of these inflammatory mediators.

Ascitic Fluid↗

Enhanced cell surface CD44 variant (v6, v9) expression by osteopontin in breast cancer epithelial cells facilitates tumor cell migration: novel post-transcriptional, post-translational regulation.

Osteopontin (OPN) is a glycosylated, secreted phosphoprotein that functions both as a cell attachment and chemotactic factor. Elevated expression of OPN confers enhanced metastatic ability on transformed cells, suggesting that OPN may contribute to the malignant progression of tumors. Migration of mammary carcinoma cells is stimulated by OPN via interactions with integrins and CD44 cell surface receptors. We hypothesized that OPN modulates specific CD44 isoform expression to facilitate breast cancer cell migration. The 21NT tumorigenic human breast cancer cell line was examined for regulation of CD44 expression at both the mRNA and protein levels in response to an engineered increase in OPN expression under CMV promoter control. Significant up-regulation of CD44s isoform mRNA expression was observed, but no change in CD44v6, v8, v9 or v10 mRNA levels. While there were elevated levels of CD44s, v6 and v9 protein at the cell surface, at the level of total cellular protein only CD44s and v6 were markedly increased. This suggests that OPN can regulate CD44 expression at both transcriptional and post-transcriptional (both amount and localization of protein) levels. To validate the functional consequence of OPN regulation of CD44 expression, we demonstrate that OPN-mediated cell migration was reduced by exposure to a anti-pan CD44 antibody, and to anti-CD44v6 and anti-CD44v9 function-blocking antibodies. Our data provide evidence that in 21NT cells OPN enhances CD44s mRNA expression, increases cell surface expression of CD44 variant forms without a change in mRNA levels, and stimulates cell migration.

Base Sequence↗

Establishment of a T cell-dependent nude mouse liver injury model induced by Propionibacterium acnes and LPS.

Normal ICR mice developed severe liver injury when they were given intravenous injections of Propionibacterium acnes and lipopolysaccharide (LPS) with a 7 day interval. In contrast, T cell-deficient ICR nude mice were resistant to P. acnes and LPS-induced liver injury. However, athymic ICR nude mice, which were treated with cell transfer of normal ICR mouse spleen cells (10(8) cells) or ICR mouse nylon-wool passed splenic T-enriched cells (over 10(7) cells), showed severe liver injury as assessed by elevation of serum transaminase activities. Histological analyses also demonstrated that the transferred cells migrated into the liver of nude mice to induce liver injury. However, depletion of both CD4+ T cells and CD8+ T cells from transferred cell populations caused a marked decrease in the elevation of serum transaminase, indicating the actual involvement of T cells in liver injury. Moreover, in vivo administration of anti-LFA-1 mAb blocked P. acnes and LPS-induced liver injury in nude mice following T cell transfer. Thus, this model will provide a new strategy to investigate T cell-dependent cell-cell interaction during the induction of liver damage.

Animals↗

Angiopoietin-4 inhibits angiogenesis and reduces interstitial fluid pressure.

Angiopoietins (Ang) are involved in the remodeling, maturation, and stabilization of the vascular network. Ang-4 was discovered more recently; thus, its effect on angiogenesis and its interplay with other angiogenic factors have not been equivocally established. The role of Ang-4 in angiogenesis was tested in Matrigel chambers implanted into the subcutaneous space of nude mice. Ang-4 inhibited the angiogenic response of basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and GLC19 tumor cells. In Matrigel chambers with Ang-4-transfected cells, the mean response was significantly lower than that of mock cells. Subcutaneous tumor interstitial fluid pressure (IFP) was significantly lower in Ang-4-transfected GLC19 tumors than in mock-transfected tumors. IFP reduction in Ang-4-transfected tumors was comparable to the reduction seen after bevacizumab treatment. In vitro, we examined the effect of recombinant Ang-4 on endothelial cell migration in Boyden chambers. Human umbilical vein endothelial cell (HUVEC) migration induced by bFGF and VEGF was inhibited by Ang-4 to control levels. In conclusion, we show that rhAng-4, as well as transfection with Ang-4, inhibits angiogenesis induced by GLC19 tumor cells and that Ang-4 expression reduces elevated tumor IFP. In addition, we demonstrate that rhAng-4 inhibits HUVEC migration and growth factor-induced angiogenesis.

Angiopoietins↗

Thiamine reverses hyperglycemia-induced dysfunction in cultured endothelial cells.

BACKGROUND: High levels of glucose have previously been shown to inhibit endothelial cell migration and increase secretion of the von Willebrand factor (vWF), a marker of endothelial cell damage. This study investigates whether thiamine, an important coenzyme in intracellular glucose metabolism, improves endothelial cell migration and decreases von Willebrand factor secretion under hyperglycemic conditions. METHODS: Bovine aortic endothelial cells (BAECs) were grown under physiological glucose (5.5 mmol/L) and hyperglycemic (13.8 mmol/L and 27.7 mmol/L) conditions with or without thiamine (200 micromol/L) supplementation. Endothelial cell migration was investigated in monolayers of BAECs that were wounded by scraping. The distance of migration, the number of migrating cells, and the surface area covered by the migrating cells were measured. Secretion of vWF by BAECs under physiological glucose and high glucose conditions with or without thiamine (200 micromol/L) supplementation was studied with enzyme-linked immunosorbent assay. RESULTS: Under hyperglycemic conditions, there was a significant decrease in the number of endothelial cells and an increase in the secretion of vWF (P <.001). Thiamine treatment limited this inhibitory effect of elevated glucose levels on BAECs. Glucose (27.7 mmol/L) significantly decreased the migration distance of BAECs into the wounded area to 4.0 +/- 1.4 cm, as compared with 6.2 +/- 0.3 cm in the control. Thiamine supplementation restored the migration distance by BAECs (6.94 +/- 0.7 cm) and the wound surface area covered (47.7 +/- 5.6 cm(2)) (P <.001). CONCLUSIONS: Hyperglycemia activates BAECs and promotes secretion of vWF, a marker of endothelial cell damage. Thiamine inhibits this endothelial cell activation and the effects of hyperglycemia on endothelial cell migration. This beneficial effect of thiamine limiting endothelial cell dysfunction is possibly through the diversion of glucose flux from anaerobic to aerobic pathways. The data from this study lead to the speculation that thiamine intake may mitigate or delay vascular complications of diabetes.

Animals↗

Calpain activity is generally elevated during transformation but has oncogene-specific biological functions.

Several oncogene and tumor-suppressor gene products are known substrates for the calpain family of cysteine proteases, and calpain is required for transformation by v-src and tumor invasion. Thus, we have now addressed whether calpain is generally associated with transformation and how calpain contributes to oncogene function. Our results demonstrate that calpain activity is enhanced upon transformation induced by the v-Src, v-Jun, v-Myc, k-Ras, and v-Fos oncoproteins. Furthermore, elevated calpain activity commonly promotes focal adhesion remodelling, disruption of actin cytoskeleton, morphological transformation, and cell migration, although proteolysis of target substrates (such as focal adhesion kinase, talin, and spectrin) is differently specified by individual oncoproteins. Interestingly, v-Fos differs from other common oncoproteins in not requiring calpain activity for actin/adhesion remodelling or migration of v-Fos transformed cells. However, anchorage-independent growth of all transformed cells is sensitive to calpain inhibition. In addition, elevated calpain activity contributes to oncogene-induced apoptosis associated with transformation by v-Myc. Taken together, these studies demonstrate that calpain activity is necessary for full cellular transformation induced by common oncoproteins, but has distinct roles in oncogenic events induced by individual transforming proteins. Thus, targeting calpain activity may represent a useful general strategy for interfering with activated proto-oncogenes in cancer cells.

Animals↗