Paola Bendinelli

Molecular basis of anti-inflammatory action of platelet-rich plasma on human chondrocytes: mechanisms of NF-κB inhibition via HGF.

Loss of articular cartilage through injury or disease presents major clinical challenges also because cartilage has very poor regenerative capacity, giving rise to the development of biological approaches. As autologous blood product, platelet‐rich plasma (PRP) provides a promising alternative to surgery by promoting safe and natural healing. Here we tested the possibility that PRP might be effective as an anti‐inflammatory agent, providing an attractive basis for regeneration of articular cartilage, and two principal observations were done. First, activated PRP in chondrocytes reduced the transactivating activity of NF‐κB, critical regulator of the inflammatory process, and decreased the expression of COX‐2 and CXCR4 target genes. By analyzing a panel of cytokines with different biological significance, in activated PRP we observed increases in hepatocyte growth factor (HGF), interleukin‐4 and tumor necrosis factor‐α (TNF‐α). HGF and TNF‐α, by disrupting NF‐κB‐transactivating activity, were important for the anti‐inflammatory function of activated PRP. The key molecular mechanisms involved in PRP‐inhibitory effects on NF‐κB activity were for HGF the enhanced cellular IkBα expression, that contributed to NF‐κB‐p65 subunit retention in the cytosol and nucleo‐cytoplasmic shuttling, and for TNF‐α the p50/50 DNA‐binding causing inhibition of target‐gene expression. Second, activated PRP in U937‐monocytic cells reduced chemotaxis by inhibiting chemokine transactivation and CXCR4‐receptor expression, thus possibly controlling local inflammation in cartilage. In conclusion, activated PRP is a promising biological therapeutic agent, as a scaffold in micro‐invasive articular cartilage regeneration, not only for its content of proliferative/differentiative growth factors, but also for the presence of anti‐inflammatory agents including HGF. J. Cell. Physiol. 225: 757–766, 2010.

Vitamin E dietary supplementation inhibits transforming growth factor β1 gene expression in the rat liver

Overexpression of transforming growth factor β1 (TGFβ1) and increased transcription of pro‐collagen type I, are known to represent major events implicated in the development of liver fibrosis under either experimental or clinical conditions. Here we report that long‐term dietary vitamin E supplementation in animals undergoing an experimental model of liver fibrosis (induced by chronic treatment of rats with carbon tetrachloride) results in a net inhibition of both hepatic TGFβ1 and α2 (I) procollagen mRNA levels. Moreover, of striking interest is the observation that vitamin E supplementation per so down‐modulates basal levels of TGFβ1 mRNA in the liver of untreated animals, suggesting that a dietary regimen rich in vitamin E may potentially interfere with both the initiation and progression of the fibrosclerotic processes.

Interaction between human-breast cancer metastasis and bone microenvironment through activated hepatocyte growth factor/Met and β-catenin/Wnt pathways

To clarify the reciprocal interaction between human-breast cancer metastatic cells and bone microenvironment, we studied the influence of HGF/Met system on a proposed-prognostic marker of aggressiveness, the beta-catenin/Wnt pathway. For in vitro and in vivo experiments we used 1833-bone metastatic clone, derived from human-MDA-MB231 cells. In osteolytic bone metastases and in metastatic cells, Met was expressed in nuclei and at plasma membrane, and abnormally co-localised at nuclear level with beta-catenin and the tyrosine phosphorylated c-Src kinase. Thus, in 1833 cells nuclear-Met COOH-terminal fragment and beta-catenin-TCF were constitutively activated, possibly by receptor and non-receptor tyrosine kinases. The activity of the gene reporter TOPFLASH (containing multiple TCF/LEF-consensus sites) was measured, as index of beta-catenin functionality. In 1833 cells, human and mouse HGF increased Met and beta-catenin tyrosine phosphorylation and expression in nuclear and perinuclear compartments, beta-catenin nuclear translocation via Kank and TOPFLASH transactivation. Human HGF was autocrine/intracrine in bone metastasis, and mouse HGF originating from the adjacent host-bone marrow, was found inside the metastatic nuclei. Parental MDA-MB231 cell nuclei did not show functional beta-catenin, for TCF-transactivating activity, and the regulation by HGF. Our study highlighted the importance of the metastasis-stroma interaction in human-breast cancer metastatisation and first identified the HGF/nuclear Met/phospho-c-Src/beta-catenin-TCF/Wnt pathway as a potential-therapeutic target to delay establishment/progression of bone metastases by affecting the aggressive phenotype.

The MAP kinase cascades are activated during post-ischemic liver reperfusion

We have investigated the involvement of MAP kinase cascades in the response of the liver to post‐ischemic reperfusion. Both JNKs and ERKs are activated but the duration and magnitude of the increase in their activities appear to be different. JNK activation is more marked but shorter than that of ERKs. The increase observed in the phosphotyrosine content of the 52 kDa Shc protein, accompanied by an increased amount of co‐immunoprecipitated Grb2, and the activation of Raf‐1 kinase provide evidence of the involvement of a Ras‐Raf‐dependent pathway, with a time course that is similar to that of ERK activation. The treatment of rats with IL‐1 receptor antagonist modified all of the described effects, suggesting that IL‐1 plays a role in the response of the liver to reperfusion.

Nuclear localization of active HGF receptor Met in aggressive MDA-MB231 breast carcinoma cells

Hepatocyte growth factor (HGF)/Met system is deregulated in tumors and is implicated in different aspects of invasive growth. Here, we report that in the highly aggressive MDA-MB231 breast carcinoma cells, Met cytosolic fragments [C-terminal fragment (CTF)] were present in the nuclei. They were constitutively active because tyrosine phosphorylated at regulatory and catalytic domains and endowed with transactivating activity independently of HGF exposure. In fact, various constructs containing juxtamembrane (Jxtm) Met fragments, fused with Gal4 DNA-binding domain, transactivated Gal4Luc activity. MDA-MB231 cells were devoid of WW domain-containing oxidoreductase (Wwox) tumor suppressor. Exogenous Wwox protein expression negatively regulated Jxtm3-transactivating activity and decreased spontaneous migration of MDA-MB231 cells. Also, we demonstrate that the lack of endogenous Wwox in MDA-MB231 cells represented a molecular mechanism for intranuclear Met-CTF accumulation and for the decrease of full-length Met stability. Yes-associated proteins maintained constitutively activated nuclear Met fragments that played a role as transcription factors regulating genes probably including those for motile phenotype. The difference with low invasive MCF-7 cells was evident because the latter did not show intranuclear Met and the transfected constructs-containing Jxtm fragments were inactive also in the presence of HGF. The constitutive activation of nuclear Met-signaling pathway in MDA-MB231 cells, possibly determined at genetic or epigenetic levels of WWOX gene, might participate in breast carcinoma progression influencing invasive/metastatic phenotype. Wwox/Met system can be suggested as a potential target to impair breast carcinoma progression.

The PPAR-γ agonist troglitazone antagonizes survival pathways induced by STAT-3 in recombinant interferon-β treated pancreatic cancer cells.

We have previously shown that cancer cells can protect themselves from apoptosis induced by type I interferons (IFNs) through a ras→MAPK-mediated pathway. In addition, since IFN-mediated signalling components STATs are controlled by PPAR gamma we studied the pharmacological interaction between recombinant IFN-β and the PPAR-γ agonist troglitazone (TGZ). This combination induced a synergistic effect on the growth inhibition of BxPC-3, a pancreatic cancer cell line, through the counteraction of the IFN-β-induced activation of STAT-3, MAPK and AKT and the increase in the binding of both STAT-1 related complexes and PPAR-γ with specific DNA responsive elements. The synergism on cell growth inhibition correlated with a cell cycle arrest in G0/G1 phase, secondary to a long-lasting increase of both p21 and p27 expressions. Blockade of MAPK activation and the effect on p21 and p27 expressions, induced by IFN-β and TGZ combination, were due to the decreased activation of STAT-3 secondary to TGZ. IFN-β alone also increased p21 and p27 expression through STAT-1 phosphorylation and this effect was attenuated by the concomitant activation of IFNbeta-induced STAT-3-activation. The combination induced also an increase in autophagy and a decrease in anti-autophagic bcl-2/beclin-1 complex formation. This effect was mediated by the inactivation of the AKT→mTOR-dependent pathway. To the best of our knowledge this is the first evidence that PPAR-γ activation can counteract STAT-3-dependent escape pathways to IFN-β-induced growth inhibition through cell cycle perturbation and increased autophagic death in pancreatic cancer cells.

Early intracellular events induced by in vivo leptin treatment in mouse skeletal muscle

Experimental evidence suggests that leptin may exert direct effects on peripheral tissues. In this study we investigated some transductional molecules in skeletal muscle, after intraperitoneal leptin injection in wild-type and ob/ob mice. By immunoprecipitation and immunoblotting with anti-phosphotyrosine antibodies, we observed a modified pattern of phosphotyrosine proteins. We then identified an increase in JAK2, IRS1 and IRS2 tyrosine-phosphorylation and in their association with p85, a subunit of PI3K. The increase in PI3K activity in immunoprecipitated p85 did not reach statistical significance, however, both Akt and GSK3 resulted significantly hyper-phosphorylated. Bad, an Akt substrate involved in cell survival, appeared modified in its phosphorylation. ERK1, ERK2 and p38 MAP kinase phosphorylation significantly increased, even if the latter only in wild-type animals. Finally, by EMSA experiments, we documented that leptin increased the DNA binding capacity of Stat3 homodimers and AP-1. Thus, leptin appears to activate, within minutes, some insulin signalling molecules. Stat3 and AP-1 activation by gene expression remodelling could subsequently trigger more leptin-specific effects. Further, leptin might play a still underestimated role in cell survival.

NF-κB Activation, Dependent on Acetylation/Deacetylation, Contributes to HIF-1 Activity and Migration of Bone Metastatic Breast Carcinoma Cells

Here, we show that NF-κB-HIF-1 interaction contributed to breast cancer metastatic capacity by means of an incomplete epithelial/mesenchymal transition and influencing migration, as shown in 1833 (human) and 4T1 (mouse) metastatic cells after different stimuli. The 1833 and the transforming growth factor-β1–exposed 4T1 cells showed both epithelial (E-cadherins) and mesenchymal (N-cadherins and vimentin) markers, and common mechanisms contributed to the retention of certain epithelial characteristics and the control of migration. The complex NF-κB-HIF-1 reciprocal regulation and the enhanced c-Jun expression played a functional role in exacerbating the invasiveness of 1833 cells after p50/p65 transfection and of 4T1 cells exposed to transforming growth factor-β1. Twist expression seemed to exert a permissive role also regulating epithelial/mesenchymal transition markers. After c-Src wild-type (Srcwt) transfection, c-Src-signal transducer overexpression in 1833 cells increased HIF-1 transactivating activity and invasiveness, and changed E-cadherin/N-cadherin ratio versus mesenchymal phenotype. The transcription factor pattern and the motile phenotype of metastatic 1833 cells were influenced by p65-lysine acetylation and HDAC-dependent epigenetic mechanisms, which positively regulated basal NF-κB and HIF-1 activities. However, HDAC3 acted as a corepressor of NF-κB activity in parental MDA-MB231 cells, thus explaining many differences from the derived 1833 clone, including reduced HIF-1α and c-Jun expression. Invasiveness was differently affected by HDAC knockdown in 1833 and MDA-MB231 cells. We suggest that acetylation/deacetylation are critical in establishing the bone-metastatic gene signature of 1833 cells by regulating the activity of NF-κB and HIF-1, and further clarify the epigenetic control of transcription factor network in the motile phenotype of 1833 cells. (Mol Cancer Res 2009;7(8):1328–41)

Leptin activates Stat3, Stat1 and AP-1 in mouse adipose tissue

Intraperitoneal leptin administration to wild-type and ob/ob mice caused a prompt activation of Stat1 and Stat3, the former to a lesser extent, in epididymal adipose tissue. Immunoblot experiments showed that tyrosine phosphorylation of Stat3 increased in total cellular extracts and that the phosphorylated protein translocated into the nucleus upon leptin treatment. Tyrosine phosphorylation and nuclear translocation of Stat1 were evident only in ob/ob mice. Gel shift and supershift analyses showed that leptin activated sis-inducible element (SIE) binding activity of adipose nuclear extracts, with Stat3 homodimer as the predominant complex. Stat1/3 heterodimers and Stat1 homodimers take part as well in the response in wild-type and ob/ob mice, although to a lesser degree. AP-1 binding activity was also induced in adipose tissue by in vivo leptin treatment with a time course that suggests a post-transcriptional inductive mechanism. This effect was greater in the ob/ob than in wild-type mice. Our data indicate that leptin operates in vivo directly on adipose tissue by triggering responses that modulate gene expression.

Hypoxia inducible factor-1 is activated by transcriptional co-activator with PDZ-binding motif (TAZ) versus WWdomain-containing oxidoreductase (WWOX) in hypoxic microenvironment of bone metastasis from breast cancer

The hypoxic microenvironment of bone marrow favours the bone metastasis process. Hypoxia inducible factor (HIF)-1α is hallmark for hypoxia, correlating with poor prognosis and radio/chemotherapy resistance of primary-breast carcinoma. For bone metastasis, the molecular mechanisms involved in HIF-1α expression and HIF-1 (α/β heterodimer)-transcription factor activity are scarcely known. We studied the role played by HIF-1 in the cross-talk between neoplastic and supportive-microenvironmental cells. Also, WWdomain-containing oxidoreductase (Wwox) and transcriptional co-activator with PDZ-binding motif (TAZ) were taken into consideration evaluating whether these Hippo-pathway effectors affect bone-metastatic phenotype through HIF-1 activity. Considering bone-metastasis specimens, nuclear HIF-1α-TAZ co-localisation occurred in neoplastic and supportive cells, such as fibroblasts and endotheliocytes. Based on these data, the functional importance was verified using 1833-bone metastatic clone under hypoxia: nuclear HIF-1α and TAZ expression increased and co-immunoprecipitated, activating HIF-1-DNA binding and transactivation. In contrast, Wwox localised at perinuclear level in neoplastic cells of bone metastasis, being almost absent in supportive cells, and Wwox-protein expression diminished in hypoxic-1833 cells. Thus, TAZ regulation of HIF-1 activity might be important for bone-secondary growth, participating in metastasis-stroma cross-talk. Further, TAZ and HIF-1α-protein levels seemed correlated. In fact, blocking cyclooxygenase-2 with NS398 in hypoxic-1833 cells, not only HIF-1α decreased but also molecular-mechanism(s) upstream of the Hippo pathway were triggered: LATS-dependent TAZ phosphorylation seemed responsible for TAZ nucleus/cytoplasm translocation and degradation. In the 1833-xenograft model, NS398 largely prevented the outgrowth of bone-metastatic cells, probably related to remarkable-extracellular matrix assembly. We gained clinical insight into HIF-1α and TAZ as candidate biomarkers for bone avidity, relevant for early-therapeutic intervention against bone metastasis.