低浓度哇巴因对负鼠肾小管上皮细胞增殖的影响

目的:用低血清培养液来模拟肾脏供血不足的营养不良状态,研究低浓度哇巴因对低血清培养下OK细胞(负鼠肾小管上皮细胞)增殖的影响。方法:用低浓度哇巴因(1-30n M)处理0.2%血清培养下OK细胞,MTT实验和Brdu掺入法检测哇巴因对OK细胞增殖的影响;Western blot检测Akt和ERK1/2的磷酸化水平;用LY294002和PD98059分别抑制PI3K/Akt和ERK1/2蛋白激酶活性,观察抑制PI3K/Akt和ERK1/2对哇巴因促进OK细胞增殖的影响。结果:低浓度哇巴因(1-30n M)促进OK细胞的增值,上调OK细胞中Akt和ERK1/2磷酸化水平。用LY294002和PD98059特异抑制Akt和ERK1/2的活化能够抑制哇巴因的促增殖作用。结论:低浓度哇巴因(1-10n M)能够促进OK细胞的增值,PI3K/Akt和ERK1/2信号通路参与哇巴因对OK细胞促增殖作用的调节。     

Regulation of Mammary Stem/Progenitor Cells by PTEN/Akt/β-Catenin Signaling

Recent evidence suggests that many malignancies, including breast cancer, are driven by a cellular subcomponent that displays stem cell-like properties. The protein phosphatase and tensin homolog (PTEN) is inactivated in a wide range of human cancers, an alteration that is associated with a poor prognosis. Because PTEN has been reported to play a role in the maintenance of embryonic and tissue-specific stem cells, we investigated the role of the PTEN/Akt pathway in the regulation of normal and malignant mammary stem/progenitor cell populations. We demonstrate that activation of this pathway, via PTEN knockdown, enriches for normal and malignant human mammary stem/progenitor cells in vitro and in vivo. Knockdown of PTEN in normal human mammary epithelial cells enriches for the stem/progenitor cell compartment, generating atypical hyperplastic lesions in humanized NOD/SCID mice. Akt-driven stem/progenitor cell enrichment is mediated by activation of the Wnt/β-catenin pathway through the phosphorylation of GSK3-β. In contrast to chemotherapy, the Akt inhibitor perifosine is able to target the tumorigenic cell population in breast tumor xenografts. These studies demonstrate an important role for the PTEN/PI3-K/Akt/β-catenin pathway in the regulation of normal and malignant stem/progenitor cell populations and suggest that agents that inhibit this pathway are able to effectively target tumorigenic breast cancer cells.     

cAMP-mediated induction of cyclin E sensitizes growth-arrested adipose stem cells to DNA damage-induced apoptosis

The differentiation capacity of mesenchymal stem cells has been extensively studied, but little is known on cell cycle–related events in the proliferation and differentiation phases of these cells. Here, we demonstrate that exposure to cAMP-increasing agents inhibits proliferation of adipose stem cells (ASCs). This antiproliferative effect is associated with both reduced cdk2 activity and pRB phosphorylation. Concomitantly, however, the level of cyclin E markedly increases upon cAMP induction, indicating that cyclin E may have cdk2-independent functions in these cells besides its role as a cdk2 activator. Indeed, we found indications of a cdk2-independent role of cyclin E in DNA damage–induced apoptosis. 8-CPT-cAMP sensitizes ASCs to γ-irradiation–induced apoptosis, an effect abolished by knockdown of cyclin E. Moreover, cAMP induces early activation of ERK, leading to reduced degradation of cyclin E. The cAMP-mediated up-regulation of cyclin E was blocked by knockdown of ERK or by an inhibitor of the ERK kinase MEK. We conclude that cAMP inhibits cdk2 activity and pRB phosphorylation, leading to reduced ASC proliferation. Concomitant with this growth inhibition, however, cyclin E levels are increased in a MEK/ERK-dependent manner. Our results suggest that cyclin E plays an important, cdk2-independent role in genotoxic stress–induced apoptosis in mesenchymal stem cells.     

Hypoxia Enhances Proliferation of Human Adipose-Derived Stem Cells via HIF-1ɑ Activation

BackgroundAdipose tissue-derived stem cells (ASCs) have been recently isolated from human subcutaneous adipose tissue. ASCs may be useful in regenerative medicine as an alternative to bone marrow-derived stem cells. Changes in the oxygen concentration influence physiological activities, such as stem cell proliferation. However, the effects of the oxygen concentration on ASCs remain unclear. In the present study, the effects of hypoxia on ASC proliferation were examined.MethodsNormal human adipose tissue was collected from the lower abdomen, and ASCs were prepared with collagenase treatment. The ASCs were cultured in hypoxic (1%) or normoxic (20%) conditions. Cell proliferation was investigated in the presence or absence of inhibitors of various potentially important kinases. Hypoxia inducible factor (HIF)-1α expression and MAP kinase phosphorylation in the hypoxic culture were determined with western blotting. In addition, the mRNA expression of vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF)-2 in hypoxic or normoxic conditions were determined with real-time RT-PCR. The effects of these growth factors on ASC proliferation were investigated. Chromatin immunoprecipitation (ChIP) of the HIF–1α-binding hypoxia responsive element in FGF–2 was performed. HIF–1α was knocked down by siRNA, and FGF–2 expression was investigated.ResultsASC proliferation was significantly enhanced in the hypoxic culture and was inhibited by ERK and Akt inhibitors. Hypoxia for 5–15 minutes stimulated the phosphorylation of ERK1/2 among MAP kinases and induced HIF–1α expression. The levels of VEGF and FGF–2 mRNA and protein in the ASCs were significantly enhanced in hypoxia, and FGF–2 increased ASC proliferation. The ChIP assay revealed an 8-fold increase in the binding of HIF–1α to FGF–2 in hypoxia. HIF–1α knockdown by siRNA partially inhibited the FGF–2 expression of ASCs induced by hypoxia.ConclusionASC proliferation was enhanced by hypoxia. HIF–1α activation, FGF–2 production, and the ERK1/2 and Akt pathway were involved in this regulatory mechanism.     

Cell Signaling and Differential Protein Expression in Neuronal Differentiation of Bone Marrow Mesenchymal Stem Cells with Hypermethylated Salvador/Warts/Hippo (SWH) Pathway Genes

Human mesenchymal stem cells (MSCs) modified by targeting DNA hypermethylation of genes in the Salvador/Warts/Hippo pathway were induced to differentiate into neuronal cells in vitro. The differentiated cells secreted a significant level of brain-derived neurotrophy factor (BDNF) and the expression of BDNF receptor tyrosine receptor kinase B (TrkB) correlated well with the secretion of BDNF. In the differentiating cells, CREB was active after the binding of growth factors to induce phosphorylation of ERK in the MAPK/ERK pathway. Downstream of phosphorylated CREB led to the functional maturation of differentiated cells and secretion of BDNF, which contributed to the sustained expression of pERK and pCREB. In summary, both PI3K/Akt and MAPK/ERK signaling pathways play important roles in the neuronal differentiation of MSCs. The main function of the PI3K/Akt pathway is to maintain cell survival during neural differentiation; whereas the role of the MAPK/ERK pathway is probably to promote the maturation of differentiated MSCs. Further, cellular levels of protein kinase C epsilon type (PKC-ε) and kinesin heavy chain (KIF5B) increased with time of induction, whereas the level of NME/NM23 nucleoside diphosphate kinase 1 (Nm23-H1) decreased during the time course of differentiation. The correlation between PKC-ε and TrkB suggested that there is cross-talk between PKC-ε and the PI3K/Akt signaling pathway.     

Cartducin stimulates mesenchymal chondroprogenitor cell proliferation through both extracellular signal-regulated kinase and phosphatidylinositol 3-kinase/Akt pathways

Cartducin, a paralog of Acrp30/adiponectin, is a secretory protein produced by both chondrogenic precursors and proliferating chondrocytes, and belongs to a novel C1q family of proteins. We have recently shown that cartducin promotes the growth of both mesenchymal chondroprogenitor cells and chondrosarcoma-derived chondrocytic cells in vitro. However, the cartducin-signaling pathways responsible for the regulation of cell proliferation have not been documented. In this study, we examined whether cartducin exists in serum and further investigated the intracellular signaling pathways stimulated by cartducin in mesenchymal chondroprogenitor cells. Western blot analysis showed that, unlike Acrp30/adiponectin, cartducin was undetectable in mouse serum. Next, mesenchymal chondroprogenitor N1511 cells were stimulated with cartducin, and three major groups of mitogen-activated protein kinase (MAPK) pathways and the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway were examined. Cartducin activated extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt, but not c-jun N-terminal kinase (JNK) nor p38 MAPK. The MEK1/2 inhibitor, U0126, blocked cartducin-stimulated ERK1/2 phosphorylation and suppressed the DNA synthesis induced by cartducin in N1511 cells. The PI3K inhibitor, LY294002, blocked cartducin-stimulated Akt phosphorylation and a decrease in cartducin-induced DNA synthesis in N1511 cells was also observed. These data suggest that cartducin is a peripheral skeletal growth factor, and that the proliferation of mesenchymal chondroprogenitor cells stimulated by cartducin is associated with activations of the ERK1/2 and PI3K/Akt signaling pathways.     

High density lipoprotein cholesterol promotes the proliferation of bone-derived mesenchymal stem cells via binding scavenger receptor-B type I and activation of PI3K/Akt, MAPK/ERK1/2 pathways

High-density lipoprotein (HDL) possesses protective properties in cardiovascular diseases. However, the effect of HDL on the mesenchymal stem cells (MSCs), which could be mobilized to the damaged myocardial tissue, has not been well elucidated yet. In the current study, we investigated the effect of HDL on the proliferation of MSCs so as to reveal its molecular mechanisms. MSCs derived from rats were treated with HDL in different concentrations and for different periods. The proliferation of MSCs was measured with MTT and BrdU cell proliferation assay. The phosphorylation of Akt, ERK1/2 and the expression of p21 were evaluated by Western blotting. After the activity of respective pathways was down-regulated by the specific inhibitor and the gene of scavenger receptor-B type I (SR-BI) was knocked down by RNA interference, BrdU assay was performed to examine this effect of HDL on MSCs. We found that the proliferation of MSCs induced by HDL, in a time- and concentration-dependent manner, was the phosphorylation of Akt- and ERK1/2-dependent, which was significantly attenuated by the specific inhibitor to respective pathways. Moreover, MAPK/ERK1/2 pathway exerted a more dominating effect on this process. SR-BI contributed to HDL-induced proliferation of MSCs, which was effectively abolished by the silencing of SR-BI. The results suggested that HDL was capable of improving MSCs proliferation, in which MAPK/ERK1/2 and PI3K/Akt pathways involved and SR-BI played a critical role as well.     

Real-time imaging reveals that noninvasive mammary epithelial acini can contain motile cells

To determine how extracellular signal–regulated kinases (ERK) 1/2 promote mammary tumorigenesis, we examined the real-time behavior of cells in an organotypic culture of the mammary glandular epithelium. Inducible activation of ERK1/2 in mature acini elicits cell motility and disrupts epithelial architecture in a manner that is reminiscent of ductal carcinoma in situ; however, motile cells do not invade through the basement membrane and branching morphogenesis does not take place. ERK1/2-induced motility causes cells to move both within the cell monolayer that contacts the basement membrane surrounding the acinus and through the luminal space of the acinus. E-cadherin expression is reduced after ERK1/2 activation, but motility does not involve an epithelial–mesenchymal transition. Cell motility and the disruption of epithelial architecture require a Rho kinase– and myosin light chain kinase–dependent increase in the phosphorylation of myosin light chain 2. Our results identify a new mechanism for the disruption of architecture in epithelial acini and suggest that ERK1/2 can promote noninvasive motility in preinvasive mammary tumors.     

Digoxin exerts anticancer activity on human nonsmall cell lung cancer cells by blocking PI3K/Akt pathway

Lung cancer remains the leading cause of cancer mortality because of its metastatic potential and high malignancy. The discovery of new applications for old drugs is a shortcut for cancer therapy. We recently investigated the antitumor effect of digoxin, a well-established drug for treating heart failure, against nonsmall cell lung cancer A549 and H1299 cells. Digoxin inhibited the proliferation and colony-forming ability of the two cell lines and arrested the cell cycle at the G0/G1 phase in A549 cells and the G2/M phase in H1299 cells. Mitochondria-mediated apoptosis was induced in A549 cells but not in H1299 cells after treatment with digoxin. Moreover, digoxin inhibited the migration, invasion, adhesion and epithelial–mesenchymal transition of A549 and H1299 cells. Autophagy was induced in both cell lines after treatment with digoxin, with an increase in autophagosome foci. In addition, digoxin inhibited the phosphorylation of Akt, mTOR and p70S6K, signaling molecules of the PI3K/Akt pathway that are known to be involved in tumor cell survival, proliferation, metastasis and autophagy. Our findings suggest that digoxin has the potential to be used for therapy for human nonsmall cell lung cancer, but further evidence is required.     

METTL14-regulated PI3K/Akt signaling pathway via PTEN affects HDAC5-mediated epithelial–mesenchymal transition of renal tubular cells in diabetic kidney disease

Histone deacetylase 5 (HDAC5) belongs to class II HDAC subfamily and is reported to be increased in the kidneys of diabetic patients and animals. However, little is known about its function and the exact mechanism in diabetic kidney disease (DKD). Here, we found that HDAC5 was located in renal glomeruli and tubular cells, and significantly upregulated in diabetic mice and UUO mice, especially in renal tubular cells and interstitium. Knockdown of HDAC5 ameliorated high glucose-induced epithelial–mesenchymal transition (EMT) of HK2 cells, indicated in the increased E-cadherin and decreased α-SMA, via the downregulation of TGF-β1. Furthermore, HDAC5 expression was regulated by PI3K/Akt signaling pathway and inhibition of PI3K/Akt pathway by LY294002 treatment or Akt phosphorylation mutation reduced HDAC5 and TGF-β1 expression in vitro high glucose-cultured HK2 cells. Again, high glucose stimulation downregulated total m6A RNA methylation level of HK2 cells. Then, m6A demethylase inhibitor MA2 treatment decreased Akt phosphorylation, HDAC5, and TGF-β1 expression in high glucose-cultured HK2 cells. In addition, m6A modification-associated methylase METTL3 and METTL14 were decreased by high glucose at the levels of mRNA and protein. METTL14 not METTL3 overexpression led to PI3K/Akt pathway inactivation in high glucose-treated HK2 cells by enhancing PTEN, followed by HDAC5 and TGF-β1 expression downregulation. Finally, in vivo HDACs inhibitor TSA treatment alleviated extracellular matrix accumulation in kidneys of diabetic mice, accompanied with HDAC5, TGF-β1, and α-SMA expression downregulation. These above data suggest that METTL14-regulated PI3K/Akt signaling pathway via PTEN affected HDAC5-mediated EMT of renal tubular cells in diabetic kidney disease.Subject terms: Epithelial-mesenchymal transition, Insulin signalling, Diabetes complications     

NHERF2 increases platelet-derived growth factor-induced proliferation through PI-3-kinase/Akt-, ERK-, and Src family kinase-dependent pathway

Platelet-derived growth factor (PDGF) has multiple functions including inhibition of apoptosis and promotion of cell proliferation. In this study, we show that Na(+)/H(+) exchanger regulatory factor 2 (NHERF2) binds to the carboxyl-terminal PDZ domain-binding motif of the PDGF receptor through a PDZ domain-mediated interaction, and evaluate the consequence on PDGF-induced proliferation. Stable transfection with NHERF2 increased the PDGF-induced phosphorylation of ERK and Akt in Rat1 embryonic fibroblasts. The phosphorylation of Akt was blocked by pretreatment with LY294002, a PI-3-kinase inhibitor, in both Rat1/NHERF2 and Rat1/vector cells. In Rat1/vector cells, PDGF-induced phosphorylation of ERK was completely inhibited by pretreatment with PD98059, a MEK inhibitor. In contrast, the NHERF2-dependent increase of ERK phosphorylation was not affected by pretreatment with PD98059 in Rat1/NHERF2 cells. Thus, the NHERF2-dependent increase of ERK phosphorylation occurs in a MEK-independent fashion. Pretreatment with PP2, a specific inhibitor of Src family tyrosine kinase, completely blocked the NHERF2-dependent increase of the phosphorylation of ERK and Akt, suggesting that NHERF2 up-regulates Erk phosphorylation through a Src family kinase-dependent pathway. Consistent with these results, the PDGF-induced thymidine incorporation was increased in Rat1/NHERF2 cells, and the NHERF2-dependent increase of thymidine incorporation was prevented by treatment with LY294002 and PP2 but not with PD98059. These results suggest that NHERF2 stimulates PDGF-induced proliferation by increasing PI-3-kinase/Akt, MEKindependent ERK, and Src family kinase-mediated signaling pathways.     

Inflammation and Cancer: Role of Annexin A1 and FPR2/ALX in Proliferation and Metastasis in Human Laryngeal Squamous Cell Carcinoma

The anti-inflammatory protein annexin A1 (ANXA1) has been associated with cancer progression and metastasis, suggesting its role in regulating tumor cell proliferation. We investigated the mechanism of ANXA1 interaction with formylated peptide receptor 2 (FPR2/ALX) in control, peritumoral and tumor larynx tissue samples from 20 patients, to quantitate the neutrophils and mast cells, and to evaluate the protein expression and co-localization of ANXA1/FPR2 in these inflammatory cells and laryngeal squamous cells by immunocytochemistry. In addition, we performed in vitro experiments to further investigate the functional role of ANXA1/FPR2 in the proliferation and metastasis of Hep-2 cells, a cell line from larynx epidermoid carcinoma, after treatment with ANXA1_2–26 (annexin A1 N-terminal-derived peptide), Boc2 (antagonist of FPR) and/or dexamethasone. Under these treatments, the level of Hep-2 cell proliferation, pro-inflammatory cytokines, ANXA1/FPR2 co-localization, and the prostaglandin signalling were analyzed using ELISA, immunocytochemistry and real-time PCR. An influx of neutrophils and degranulated mast cells was detected in tumor samples. In these inflammatory cells of peritumoral and tumor samples, ANXA1/FPR2 expression was markedly exacerbated, however, in laryngeal carcinoma cells, this expression was down-regulated. ANXA1_2–26 treatment reduced the proliferation of the Hep-2 cells, an effect that was blocked by Boc2, and up-regulated ANXA1/FPR2 expression. ANXA1_2–26 treatment also reduced the levels of pro-inflammatory cytokines and affected the expression of metalloproteinases and EP receptors, which are involved in the prostaglandin signalling. Overall, this study identified potential roles for the molecular mechanism of the ANXA1/FPR2 interaction in laryngeal cancer, including its relationship with the prostaglandin pathway, providing promising starting points for future research. ANXA1 may contribute to the regulation of tumor growth and metastasis through paracrine mechanisms that are mediated by FPR2/ALX. These data may lead to new biological targets for therapeutic intervention in human laryngeal cancer.     

miR-375 Mediated Acquired Chemo-Resistance in Cervical Cancer by Facilitating EMT

Acquired chemo-resistance is one of the key causal factors in cancer death. Emerging evidences suggest that miRNA and epithelial–mesenchymal transition play critical roles in the chemo-resistance in cancers. Here, we showed the association of paclitaxel-resistance with miR-375 over-expression and epithelial–mesenchymal transition inducement in cervical cancer. Using different cervical cancer cell models, we found that paclitaxel transiently induced up-regulation of miR-375 expression, proliferation inhibition, transition from epithelial to mesenchymal phenotype, and consequently impaired paclitaxel sensitivity. Forced over-expression of miR-375 may suppress Ecadherin expression by a directly targeting pathway, which led to paclitaxel resistance. Contrarily, re-expression of Ecadherin partly reversed epithelial–mesenchymal transition phenotype and miR-375 induced paclitaxel-resistance. Our findings suggest that paclitaxel-induced miR-375 over-expression facilitates epithelial–mesenchymal transition process via directly targeting Ecadherin, proliferation inhibition, and consequently results in chemo-resistance in cervical cancer cells. A reversion of miR-375 or Ecadherin expression may be a novel therapeutic approach for overcoming chemo-resistance in cervical cancer.     

白藜芦醇通过下调MEK/ERK/c-Jun信号通路抑制H2O2诱导的肺癌细胞增殖

目的:探讨白藜芦醇(Res)是否通过下调ERK激酶/胞外信号调节激酶/原癌基因(MEK/ERK/c-Jun)信号通路抑制小剂量过氧化氢(H2O2)诱导肺癌细胞增殖。方法:采用MTS实验检测小剂量20μM H2O2以及分别加入MEK阻断剂U0126和Res后H2O2对肺癌细胞NCI-H1395增殖的影响,采用Western Blot检测H2O2对ERK1/2和Akt蛋白磷酸化水平以及加入Res后H2O2对MEK、ERK1/2和c-Jun蛋白磷酸化水平的影响。结果:小剂量H2O2对肺癌细胞NCI-H1395具有促增殖作用,H2O2通过活化ERK1/2和Akt蛋白的磷酸化水平促进肺癌细胞NCI-H1395增殖,加入MEK阻断剂U0126后H2O2对肺癌细胞NCI-H1395增殖作用降低(P<0.05)。Res可抑制H2O2诱导的肺癌细胞NCI-H1395增殖,加入Res后,H2O2引起的MEK、ERK1/2和c-Jun蛋白磷酸化水平均降低(P<0.05)。结论:小剂量H2O2对肺癌细胞NCI-H1395具有促增殖作用,Res通过抑制MEK/ERK/c-Jun信号通路来抑制H2O2对肺癌细胞NCI-H1395的促增殖作用,其具体机制还需进一步研究。     

MAPK/ERK and Wnt/β-Catenin pathways are synergistically involved in proliferation of Sca-1 positive hepatic progenitor cells

Hepatic progenitor cells (HPCs) persist in adulthood and have the potential to play a major role in regenerating diseased liver. However, the signaling pathways that both directly and indirectly regulate HPCs’ self-renewal and differentiation remain elusive. Previously, we identified a bipotent, stem cell antigen-1 (Sca-1) positive HPC population from naïve adult liver tissue. In the present study, we aimed to investigate the involvement of various signaling pathways in Sca-1⁺ HPC proliferation. Epidermal growth factor (EGF) supplementation shows a significant increase in Sca-1⁺ HPC proliferation and colony formation while stimulating phosphorylation of ERK1/2 and activating the induction of Cyclin D1. There were no demonstrable effects of EGF on Akt. The MEK inhibitor, PD0325901, inhibits proliferation and ERK1/2 phosphorylation while also suppressing the expression of Cyclin D1. In addition, activation of either IL-6/STAT3 or Wnt/β-Catenin pathway did not independently support cell proliferation and colony formation of HPCs. The Wnt/β-Catenin pathway can cooperate with EGF to significantly promote HPC colony formation ratio and maintain long-term HPC in vitro. The data indicates that the MAPK/ERK pathway is both essential and critical for HPC proliferation, and the Wnt signaling pathway is not sufficient, while it works synergistically with the MAPK/ERK signaling pathway to promote HPC proliferation.     

AnnexinA7 promotes epithelial–mesenchymal transition by interacting with Sorcin and contributes to aggressiveness in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and metastasis is the major cause of the high mortality of HCC. In this study, we identified that AnnexinA7 (ANXA7) and Sorcin (SRI) are overexpressed and interacting proteins in HCC tissues and cells. In vitro functional investigations revealed that the interaction between ANXA7 and SRI regulated epithelial–mesenchymal transition (EMT), and then affected migration, invasion, and proliferation in HCC cells. Furthermore overexpression/knockdown of ANXA7 was remarkably effective in promoting/inhibiting tumorigenicity and EMT in vivo. Altogether, our study unveiled a mechanism that ANXA7 promotes EMT by interacting with SRI and further contributes to the aggressiveness in HCC, which provides a novel potential therapeutic target for preventing recurrence and metastasis in HCC.Subject terms: Medical research, Genetics research     

Fluvastatin attenuates IGF-1-induced ERK1/2 activation and cell proliferation by mevalonic acid depletion in human mesangial cells

AimsInsulin-like growth factor (IGF)-1 is a major mitogenic growth factor for mesangial cells (MCs). Statins slow the progression of chronic kidney disease by affecting inflammatory cell signaling pathways, in addition to improving lipid profile, however, no studies have investigated the effects of fluvastatin on mitogen-activated protein (MAP) kinase activity or MC proliferation in kidney cells. We investigated the effects of fluvastatin on IGF-1-induced activation of intracellular signal pathways and MC proliferation, and examined the inhibitory mechanisms of fluvastatin.Main methodsWestern blotting and cell proliferation assay were used.Key findingsIGF-1 induced phosphorylation of extracellular-related kinase (ERK)1/2, MAP or ERK kinase (MEK)1/2, and Akt, expression of cyclin D1, and MC proliferation in cultured human MCs. Fluvastatin or PD98059, an MEK1 inhibitor, completely abolished IGF-1-induced MEK1/2 and ERK1/2 phosphorylation and MC proliferation, whereas inhibition of Akt had no effect on MC proliferation. Mevalonic acid prevented fluvastatin inhibition of IGF-1-induced MEK1/2 and ERK1/2 phosphorylation, cyclin D1 expression, and MC proliferation.SignificanceFluvastatin inhibits IGF-1-induced activation of the MAP kinase pathway and MC proliferation by mevalonic acid depletion, and might have renoprotective effects by inhibiting IGF-1-mediated MC proliferation.