Efficacy and safety of conversion of mycophenolate mofetil to enteric-coated mycophenolate sodium in Mexican renal transplant children

The aim of the study was to evaluate the efficacy and safety of the conversion of MMF to EC-MPS in pediatric renal transplant recipients. We included 12 patients with stable graft function who were receiving MMF treatment. In the first visit, a complete medical examination was performed, which included a GSRS, a nine-point pharmacokinetic profile, samples for renal, liver and hematological tests and evaluation of IMPDH2 gene expression. The patients were transferred to an equimolar dose of EC-MPS. Two wk later, a clinical evaluation and blood collection, as in the first visit were performed. There was no change in serum creatinine, leukocyte count, serum albumin, or transaminase levels, but we found a statistically significant reduction of hemoglobin after conversion (13.2 +/- 1.6 g/dL with MMF vs. 12.5 +/- 1.3 g/dL when receiving EC-MPS). The GSRS total mean score was 16 +/- 12 with MMF vs. 8 +/- 5 with EC-MPA (p < 0.05). There was no statistically significant difference between formulations in the gene expression of IMPDH 2, in the AUC(0-12h) or in C(max). However, peak concentration occurred later with EC-MPS.

Modeling metastasis biology and therapy in real time in the mouse lung

Pulmonary metastasis remains the leading ca use of death for cancer patients. Opportunities to improve treatment outcomes for patients require new methods to study and view the biology of metastatic progression. Here, we describe an ex vivo pulmonary metastasis assay (PuMA) in which the metastatic progression of GFP-expressing cancer cells, from a single cell to the formation of multicellular colonies, in the mouse lung microenvironment was assessed in real time for up to 21 days. The biological validity of this assay was confirmed by its prediction of the in vivo behavior of a variety of high- and low-metastatic human and mouse cancer cell lines and the discrimination of tumor microenvironments in the lung that were most permissive to metastasis. Using this approach, we provide what we believe to be new insights into the importance of tumor cell interactions with the stromal components of the lung microenvironment. Finally, the translational utility of this assay was demonstrated through its use in the evaluation of therapeutics at discrete time points during metastatic progression. We believe that this assay system is uniquely capable of advancing our understanding of both metastasis biology and therapeutic strategies.

Abstract 2359: Modeling the kinetics of metastatic progression

Background: Metastasis has previously been described as an inefficient process - that is, many tumor cells do not survive the process of early metastasis. Metastatic cells must survive exposure to a foreign microenvironment, which can induce cell death, and to the circulation, which provides mechanical sheer stress and immune cells. By observing the kinetics of tumor growth in both ex vivo and in vivo models of metastasis, we hope to determine the relative contributions of circulatory flow and a foreign microenvironment to metastatic inefficiency.

Methods: We have developed a novel Pulmonary Metastasis Assay (PuMA), in which we observe the progression of fluorescence-tagged tumor cells in an ex vivo whole organ lung culture. The PuMA model exposes metastatic cells to a foreign microenvironment, but not to the circulation. The intravital videomicroscopy (IVVM) model exposes tumor cells to both the circulation and a foreign microenvironment. We performed serial assessments of tumor burden for the first seven days after arrival of metastatic cells to the lungs, to compare kinetics of tumor growth in both circulation-dependent and circulation-independent models of metastasis.

Results: Both the PuMA and IVVM models displayed metastatic inefficiency. The kinetics of metastatic inefficiency and recovery in the PuMA is similar to that seen in IVVM, with periods of 1) decline in tumor burden, 2) a plateau of several days, and 3) an escape, in which tumor burden grows beyond its baseline value. The magnitude of the initial decline in tumor burden, however, is greater in the IVVM model (85% decrease from baseline, at 24 hours after metastasis), than in the PuMA model (43% decrease at 24 hours).

Conclusions: These data indicate that there is a significant circulation-independent contribution to metastatic inefficiency (as seen in the decrease in tumor burden in our PuMA model), as well a circulation-dependent contribution (as seen in the greater decrease in our IVVM model). We believe that the PuMA model will be a valuable tool in studying signaling pathways that affect survival in foreign environment. Studies are now underway to use the PuMA, in combination with pharmaceutical and genetic targeting, to study the effect of individual signaling pathways on survival during early metastasis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2359.

Insulin-like growth factor-I regulates the liver microenvironment in obese mice and promotes liver metastasis

Among the mechanisms implicated in the tumor-promoting effects of obesity, signaling by insulin-like growth factor-I (IGF-I) and insulin has received considerable attention. However, the emerging realization that obesity is associated with chronic inflammation has prompted other consideration of how the IGF-I axis may participate in cancer progression. In the present study, we used two mouse models of chronic (LID) and inducible (iLID) igf-1 gene deficiency in the liver to investigate the role of IGF-I in regulating the host microenvironment and colorectal carcinoma growth and metastasis in obese mice. Obese mice had a heightened inflammatory response in the liver, which was abolished in mice with chronic IGF-I deficiency (LID). In control animals changes to the hepatic microenvironment associated with obesity sustained the presence of tumor cells in the liver and increased the incidence of hepatic metastases after intrasplenic/portal inoculation of colon carcinoma cells. These changes did not occur in LID mice with chronic IGF-1 deficiency. In contrast, these changes occurred in iLID mice with acute IGF-1 deficiency, in the same manner as the control animals, revealing a fundamental difference in the nature of the requirement for IGF-1 on tumor growth and metastasis. In the setting of obesity, our findings imply that IGF-1 is critical to activate and sustain an inflammatory response in the liver that is needed for hepatic metastasis, not only through direct, paracrine effect on tumor cell growth, but also through indirect effects involving the tumor microenvironment.

Identification of FGFR4-activating mutations in human rhabdomyosarcomas that promote metastasis in xenotransplanted models

Rhabdomyosarcoma (RMS) is a childhood cancer originating from skeletal muscle, and patient survival is poor in the presence of metastatic disease. Few determinants that regulate metastasis development have been identified. The receptor tyrosine kinase FGFR4 is highly expressed in RMS tissue, suggesting a role in tumorigenesis, although its functional importance has not been defined. Here, we report the identification of mutations in FGFR4 in human RMS tumors that lead to its activation and present evidence that it functions as an oncogene in RMS. Higher FGFR4 expression in RMS tumors was associated with advanced-stage cancer and poor survival, while FGFR4 knockdown in a human RMS cell line reduced tumor growth and experimental lung metastases when the cells were transplanted into mice. Moreover, 6 FGFR4 tyrosine kinase domain mutations were found among 7 of 94 (7.5%) primary human RMS tumors. The mutants K535 and E550 increased autophosphorylation, Stat3 signaling, tumor proliferation, and metastatic potential when expressed in a murine RMS cell line. These mutants also transformed NIH 3T3 cells and led to an enhanced metastatic phenotype. Finally, murine RMS cell lines expressing the K535 and E550 FGFR4 mutants were substantially more susceptible to apoptosis in the presence of a pharmacologic FGFR inhibitor than the control cell lines expressing the empty vector or wild-type FGFR4. Together, our results demonstrate that mutationally activated FGFR4 acts as an oncogene, and these are what we believe to be the first known mutations in a receptor tyrosine kinase in RMS. These findings support the potential therapeutic targeting of FGFR4 in RMS.

Conotruncal anomalies in fetal life: accuracy of diagnosis, associated defects and outcome

OBJECTIVES

To assess the accuracy of prenatal echocardiography, associated anomalies, and outcome of fetuses with conotruncal anomalies (CTA).

STUDY DESIGN

We searched our database for CTA prenatally diagnosed between 1990 and 2005. We included tetralogy of Fallot (TOF), transposition of the great arteries (TGA), double-outlet right ventricle (DORV), truncus arteriosus (TA), pulmonary atresia with ventricular septal defect (PA-VSD) and posterior malalignment type VSD with aortic arch obstruction (pmtVSD-AAO). Data of 144 fetuses with complete follow-up were retrieved and analyzed.

RESULTS

The main reason for referral was suspected heart defect on a routine obstetric scan (72%). Most cases were detected < or =22 weeks (55%). The presence of a CTA was confirmed postnatally in 143 cases (99%), and the diagnosis of the first fetal echocardiography was correct in 126 (87.5%). Most diagnosis of TOF (33/36, 91.7%), TGA (34/38, 89.5%) and DORV (34/38, 89.5%) were proved correct. Inadequate assessment of the interventricular septum, the distal aortic arch and/or the severity of the right outflow tract obstruction accounted for most errors. The accuracy rate was lower in TA (11/14, 78.6%) and PA-VSD (4/7, 57.1%), with evaluation of the branch pulmonary arteries as the main source of discrepancies. In 7/18 incorrect cases subsequent scans allowed to obtain a correct diagnosis. Most fetuses (64%) had an isolated CTA. Thirty-seven had chromosomal anomalies (26%) but none were found in TGA. 22q11 deletion affected 8.7% of the tested patients. Nuchal translucency (NT) was above 95th centile in 19/104 cases (18%) in which NT were measured. Fifty cases were interrupted. The overall one-year survival rate was 71%, with differences between cases with and without associated defects (9/25, 36% vs. 57/68, 83.8%; p<0.01). The uncomplicated forms of TGA and TOF had the best survival rates (100%).

CONCLUSIONS

Most CTA can be diagnosed by fetal echocardiography with a high degree of accuracy. Chromosomal defects should always be ruled out, except for simple TGA. Current survival figures in many isolated CTA, especially simple TGA and TOF, support a change in the "classical" concept that congenital heart defects detected prenatally often have the worst outlook.

CONDENSATION

Most CTA can be diagnosed by fetal echocardiography with a high degree of accuracy. Isolated CTA are more common and most of these may have a favourable outcome.

Hypoplastic left heart syndrome diagnosed in fetal life: associated findings, pregnancy outcome and results of palliative surgery

OBJECTIVES

To analyze the main prenatal characteristics of hypoplastic left heart syndrome (HLHS), its association with extracardiac anomalies including increased nuchal translucency (NT) and the outcome of affected patients.

METHODS

We searched our database for classical forms of HLHS (aortic atresia, mitral and aortic atresia and critical aortic stenosis evolved to a severely hypoplastic left ventricle) prenatally diagnosed between 1998 and 2006. Data on 101 fetuses were retrieved and analyzed.

RESULTS

The main reason for referral was suspected heart defect on a routine ultrasound scan (82%). The mean gestational age at diagnosis was 21 weeks. Most cases were detected at < or = 22 weeks (72%), the upper limit for termination of pregnancy (TOP) in our country (Spain). An intact atrial septum was diagnosed in 11 of the 58 fetuses (19%) in which pulmonary vein blood flow was assessed, and this diagnosis was proved to be correct in the six liveborn babies. Most fetuses (68%) had an isolated HLHS. Fourteen fetuses (14%) were chromosomally abnormal and all had associated extracardiac defects. NT was above the 95th centile in 21 of the 74 cases (28%) in which this measurement was available. 79% (58/73) of the cases in which HLHS was detected at < or = 22 weeks were terminated, and no differences in the rate of TOP were found through the study period. Among the 43 continuing pregnancies, seven fetuses died in utero and there were 36 live births; in 12 cases the parents opted for compassionate care and 24 chose to have the infant surgically treated. In the cohort of intention-to-treat cases, the overall survival rate was 36% (9/25). This rate improved from 18% (2/11) in the period 1998-2002 to 50% (7/14) in 2003-2006. There were no survivors in cases with intact atrial septum or when there were associated defects. At follow-up, 2/9 survivors suffered from significant neurological morbidity.

CONCLUSIONS

Fetal echocardiography allows an accurate diagnosis of HLHS, which is made in most instances in the first half of pregnancy. Despite the advantage offered by the prenatal detection of HLHS, which provides the opportunity to plan perinatal management, our up-to-date results show that the outlook for these fetuses is still poor, and highlight the importance of presenting these figures when counseling parents with affected fetuses.

Murine osteosarcoma primary tumour growth and metastatic progression is maintained after marked suppression of serum insulin-like growth factor I

The insulin-like growth factor I (IGF-I) signaling pathway has been shown to play an important role in several aspects of cancer biology, including metastasis. The aim of this study was to define the contribution of serum (endocrine) and local (tumour microenvironment) IGF-I on osteosarcoma tumour growth and metastasis, a cancer that is known to be dependent on the IGF-I axis. To test this hypothesis, we evaluated the primary tumour growth and metastatic progression of K7M2 murine osteosarcoma cells injected to a genetically engineered mouse [liver-specific IGF-I deficient (LID)] in which serum IGF-I levels are reduced by 75%, while maintaining expression of IGF-I in normal tissues. We first demonstrated that IGF-I in the tumour and the tumour-microenvironment were maintained in the LID mice. Within this designed model, there was no difference in primary tumour growth or in pulmonary metastasis in LID mice compared to control mice. Furthermore, there was no difference in the number or localization of single metastatic cells immediately after their arrival in the lungs of LID mice and control mice, as analysed by single cell video microscopy. Collectively, these data suggest that marked reduction in serum IGF-I is not sufficient to slow the progression of either primary or metastatic models of osteosarcoma.

Inhibition of AP-1 transcriptional activity blocks the migration, invasion, and experimental metastasis of murine osteosarcoma

A well-characterized murine osteosarcoma model for metastasis and invasion was used in this study to determine the role of AP-1 in the progression of this disease. We analyzed K12 and K7M2 cells, two clonally related murine osteosarcoma cell lines that have been characterized as low metastatic or high metastatic, respectively, for AP-1 components and activity. AP-1 DNA binding was similar between the two cell lines; however AP-1 transcriptional activity was enhanced by 3- to 5-fold in K7M2 cells relative to that in K12 cells. The AP-1 complexes in K12 and K7M2 cells was composed primarily of cJun, JunD, FosB, Fra1, and Fra2, with the contribution of individual components in the complex varying between the two cell lines. In addition, an increase in phosphorylated cJun, JNK activity, and phosphorylated ERK1/2 was associated with the more metastatic osteosarcoma phenotype. The significance of AP-1 activation was confirmed by conditional expression of TAM67, a dominant negative mutant of cJun. Under conditions where TAM67 inhibited AP-1 activity in K7M2 cells, migration and invasion potential was significantly blocked. Tam67 expression in aggressive osteosarcoma cells decreased long-term in vivo experimental metastasis and increased survival of mice. This study shows that differences in metastatic activity can be due to AP-1 activation. The inhibition of AP-1 activity may serve as a therapeutic tool in the management of osteosarcoma.

Nm23-H1 suppresses metastasis by inhibiting expression of the lysophosphatidic acid receptor EDG2

Nm23-H1 transcriptionally down-regulates expression of the lysophosphatidic acid receptor EDG2 and this down-regulation is critical for Nm23-H1-mediated motility suppression in vitro. We investigated the effect of altered EDG2 expression on Nm23-H1-mediated metastasis suppression in vivo. Clonal MDA-MB-435-derived tumor cell lines transfected with Nm23-H1 together with either a vector control or EDG2 had similar anchorage-dependent and anchorage-independent growth rates in vitro. However, a 45- and 300-fold inhibition of motility and invasion (P < 0.0001), respectively, was observed in Nm23-H1/vector lines, whereas coexpression of EDG2 restored activity to levels observed in the parental line. Using fluorescently labeled cells and ex vivo microscopy, the capacity of these cells to adhere, arrest, extravasate, and survive in the murine lung over a 24-h time course was measured. Only 5% of Nm23-H1/vector-transfected cells were retained in the murine lung 6 h following tail vein injection; coexpression of EDG2 enhanced retention 8- to 13-fold (P < 0.01). In a spontaneous metastasis assay, the primary tumor size of Nm23-H1/vector and Nm23-H1/EDG2 clones was not significantly different. However, restoration of EDG2 expression augmented the incidence of pulmonary metastasis from 51.9% to 90.4% (P = 2.4 x 10(-5)), comparable with parental MDA-MB-435 cells. To determine the relevance of this model system to human breast cancer, a cohort of breast carcinomas was stained for Nm23-H1 and EDG2 and a statistically significant inverse correlation between these two proteins was revealed (r = -0.73; P = 0.004). The data indicate that Nm23-H1 down-regulation of EDG2 is functionally important to suppression of tumor metastasis.

Fas-negative osteosarcoma tumor cells are selected during metastasis to the lungs: the role of the Fas pathway in the metastatic process of osteosarcoma

Low expression of Fas by different tumors including osteosarcoma, correlates with poor prognosis. We found that osteosarcoma lung metastases from patients expressed negligible amounts of Fas, but primary tumors often expressed high Fas levels. The reason for this discrepancy is unknown. We hypothesized that because FasL is constitutively expressed in the lungs, Fas-positive (Fas(+)) tumor cells entering the lungs would bind with FasL and die from Fas-induced apoptosis, resulting in the "selection" of Fas-negative (Fas(-)) cells, which would eventually form metastases. To test this hypothesis, we injected K7 osteosarcoma cells, which express functional Fas in vitro, into mice and confirmed that its bone tumors were Fas(+), but lung metastases were Fas(-). Next, to inhibit Fas signaling without affecting Fas expression, we transfected these cells with a FADD-dominant negative (FDN) plasmid and developed K7/FDN cells. Metastases formed by K7/FDN cells contained Fas(+) tumor cells. Moreover, K7/FDN cells were retained in the lungs longer and formed more lung metastases than K7 cells. In addition, the incidence of lung metastases in FasL-deficient mice injected with K7 cells was higher than that in wild-type mice. Metastases from FasL-deficient mice but not from wild-type mice contained Fas(+) tumor cells. Based on that, we conclude that Fas(-) osteosarcoma cells are selected during lung metastases formation and that inhibition of Fas signaling in tumors or lack of FasL in the host environment allows the proliferation of Fas(+) osteosarcoma cells in the lungs and promotes metastases growth. Therefore, Fas may be considered as a new therapeutic target for osteosarcoma treatment.

Corruption of the Fas pathway delays the pulmonary clearance of murine osteosarcoma cells, enhances their metastatic potential, and reduces the effect of aerosol gemcitabine

PURPOSE

Pulmonary metastases continue to be a significant problem in osteosarcoma. Apoptosis dysfunction is known to influence tumor development. Fas (CD95, APO-1)/FasL is one of the most extensively studied apoptotic pathways. Because FasL is constitutively expressed in the lung, cells that express Fas should be eliminated by lung endothelium. Cells with low or no cell surface Fas expression may be able to evade this innate defense mechanism. The purpose of these studies was to evaluate Fas expression in osteosarcoma lung metastases and the effect of gemcitabine on Fas expression and tumor growth.

EXPERIMENTAL DESIGN AND RESULTS

Using the K7M2 murine osteosarcoma model, Fas expression was quantified using immunohistochemistry. High levels of Fas were present in primary tumors, but no Fas expression was present in actively growing lung metastases. Blocking the Fas pathway using Fas-associated death domain dominant-negative delayed tumor cell clearance from the lung and increased metastatic potential. Treatment of mice with aerosol gemcitabine resulted in increased Fas expression and subsequent tumor regression.

CONCLUSIONS

We conclude that corruption of the Fas pathway is critical to the ability of osteosarcoma cells to grow in the lung. Agents such as gemcitabine that up-regulate cell surface Fas expression may therefore be effective in treating osteosarcoma lung metastases. These data also suggest that an additional mechanism by which gemcitabine induces regression of osteosarcoma lung metastases is mediated by enhancing the sensitivity of the tumor cells to the constitutive FasL in the lung.

Preclinical studies of treosulfan demonstrate potent activity in Ewing's sarcoma

OBJECTIVES

High-dose chemotherapy with the alkylating agent busulfan has been widely used in the treatment of patients with high-risk Ewing's sarcoma. Because of risks for toxicity, busulfan and radiotherapy can not be applied together, leading to the omission of one effective therapy component. Treosulfan is a derivative of busulfan which has a lower side effect profile than busulfan and which can be used together with radiotherapy. We investigated the effect of treosulfan in a panel of Ewing's sarcoma cell lines on cell survival, cell cycle and apoptosis in vitro and compared it to busulfan. Furthermore, the anti-tumor effect of treosulfan was studied in an orthotopic Ewing's sarcoma mouse xenograft model.

METHODS

Cell survival was measured by MTT assay and cell cycle analysis by flow cytometry. Apoptosis was analyzed via detection of DNA fragmentation, Hoechst 33258 staining, Annexin V, and cleavage of caspases-3 and 9. The effect of treosulfan and busulfan on primary tumor growth was assessed in Ewing's sarcoma xenografts in NOD/SCID mice (10 mice per group), pharmacokinetics of treosulfan were analyzed in nude mice.

RESULTS

Treosulfan inhibited cell growth to at least 70% in all cell lines at concentrations achievable in vivo. Treosulfan had a greater effect on the inhibition of cell growth at equivalent concentrations compared to busulfan. The growth inhibitory effect of treosulfan at low concentrations was mainly due to a G2 cell cycle arrest, whereas at higher concentrations it was due to apoptosis. Apoptosis was induced at lower concentrations compared to busulfan. In contrast to busulfan, treosulfan induced cell death in an apoptosis-deficient cell line at concentrations achievable in vivo. In mice, treosulfan suppressed tumor growth at dosages of 2,500 and 3,000 mg/kg. Pharmacokinetic exposures of treosulfan in mice were similar to previous reports in human patients. At maximal tolerated dosages treosulfan had a higher anti-tumor activity than busulfan.

CONCLUSIONS

Our results suggest that treosulfan has efficacy against Ewing's sarcoma cells in vitro and in mice. Therefore, controlled trials examining the role of treosulfan in patients with Ewing's sarcoma are warranted.

CCI-779 inhibits rhabdomyosarcoma xenograft growth by an antiangiogenic mechanism linked to the targeting of mTOR/Hif-1alpha/VEGF signaling

Angiogenesis is one of the critical steps in tumor growth and metastasis. The goal of this study was to evaluate whether the antitumor activity of CCI-779 is related to antiangiogenic effects in vivo in tumors of mice bearing human rhabdomyosarcoma (RMS) xenografts. We now demonstrate that CCI-779 rapidly inhibits mTOR activity, as indicated by S6 reduction and eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) phosphorylation in two xenograft models of RMS within 24 hours of treatment. Treatment with a single 20-mg/kg dose of CCI-779 suppressed S6 phosphorylation for more than 72 hours and 4E-BP1 phosphorylation for more than 96 hours. Based on these data, an intermittent treatment schedule (every 3 days for 30 days) was chosen and displayed a significant suppression of both tumor growth and mTOR signaling. Western blot analysis and immunohistochemical studies demonstrated that the antitumor activity of CCI-779 was associated with antiangiogenesis, as indicated by impaired levels of hypoxia-inducible factor-1alpha (Hif-1alpha) and vascular endothelial growth factor (VEGF) protein expression and by decreased microvessel density in Rh30 and RD xenografts. Together, these data suggest that CCI-779 inhibits human RMS xenograft growth by an antiangiogenic mechanism associated with the targeting of mTOR/Hif-1alpha/VEGF signaling.

Reduction of murine osteosarcoma lung metastases using the dipeptidyl peptidase inhibitor talabostat

9009

Background: Dipeptidyl peptidases comprise a family of serine proteases that includes the genes dipeptidyl peptidase IV (DPP-IV) and fibroblast activation protein (FAP). FAP is expressed in stromal fibroblasts that surround sites of metastatic carcinomas, but not in the tumor cells themselves. Talabostat (valine-proline-boronic acid) is a potent and long-acting inhibitor of dipeptidyl peptidases. It has previously been shown to have anti-tumor activity in preclinical studies. We utilized this compound to determine whether inhibition of dipeptidyl peptidases leads to a decrease in lung metastases using a murine model of osteosarcoma metastasis. Methods: 1×106 K7M3-luciferase murine osteosarcoma cells were injected by tail vein into female Balb/C mice. Mice were then treated by gavage with talabostat (20 ug/dose) twice daily, talabostat once daily, or normal saline twice daily, 5 days on and 2 days off. Half of the mice were analyzed once a week using luminescent imaging. All animals were euthanized on day 24 and the number of lung metastases counted. Results: For the control mice, the average number of surface lung nodules was 75.6 (SD 45.4). Mice treated with talabostat had a ten-fold reduction in the number of nodules (twice daily - average 7.0, SD 6.1, p-value <0.01, once daily - average 3.4, SD 2.4, p-value <0.01). The number of resulting metastatic nodules correlated with luminescent intensity. Conclusions: Mice treated with the dipeptidyl peptidase inhibitor, talabostat, had a ten-fold decrease in the number of visible metastatic lung nodules. Experiments to elucidate the mechanism that links treatment with talabostat and inhibition of metastases are currently being performed.

[Table: see text]

CD1d-Restricted Natural Killer T Cells Can Down-regulate Tumor Immunosurveillance Independent of Interleukin-4 Receptor-Signal Transducer and Activator of Transcription 6 or Transforming Growth Factor-β

It has been shown previously that the suppression of tumor immunosurveillance may be a mechanism by which tumors resist immune detection and elimination. In this study, we evaluated the role of the immunoregulatory natural killer T (NKT) cells in the biology of immunosurveillance of osteosarcoma. The K7M2 mouse osteosarcoma cell line was implanted orthotopically into wild-type and NKT cell-deficient CD1d knockout (KO) BALB/c mice, and mice were monitored for growth of primary tumors. Further, we examined the role of CD4(+) and/or CD8(+) cells by depleting the cells in vivo and measuring CTL activity in vitro. We also asked the role of interleukin (IL)-4 receptor alpha (IL-4Ralpha)-signal transducer and activator of transcription 6 (STAT6) signaling, including IL-13, and transforming growth factor beta (TGF-beta) by using gene-disrupted mice or treating mice with cytokine antagonists. We were surprised to find a high rate of rejection of osteosarcoma primary tumors in 88% (14 of 16) of CD1d KO mice compared with syngeneic wild-type BALB/c mice that showed rejection of tumor in <24% of mice. Further studies suggested that the rejection of tumor in CD1d KO mice was dependent on CD8(+) lymphocytes. Distinct from other murine tumor models, the negative regulation induced by CD1d-restricted NKT cells was not dependent on IL-4Ralpha-STAT6 signaling, including IL-13, or on TGF-beta. These data suggest that a novel CD1d-restricted NKT cell-mediated mechanism for tumor immunosuppression is active in the K7M2 osteosarcoma model and that NKT cells can regulate immunosurveillance through more than one pathway.

Rapamycin inhibits ezrin-mediated metastatic behavior in a murine model of osteosarcoma

Osteosarcoma is the most frequent primary malignant tumor of bone with a high propensity for metastasis. We have previously showed that ezrin expression is necessary for metastatic behavior in a murine model of osteosarcoma (K7M2). In this study, we found that a mechanism of ezrin-related metastatic behavior is linked to an Akt-dependent mammalian target of rapamycin (mTOR)/p70 ribosomal protein S6 kinase (S6K1)/eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) pathway. Suppression of ezrin expression either by antisense transfection or by small interfering RNAs or disruption of ezrin function by transfection of a dominant-negative ezrin-T567A mutant led to decreased expression and decreased phosphorylation of both S6K1 and 4E-BP1. Proteosomal inhibition by MG132 reversed antisense-mediated decrease of S6K1 and 4E-BP1 protein expression, but failed to affect the effect of ezrin on phosphorylation of S6K1 and 4E-BP1. Blockade of the mTOR pathway with rapamycin or its analog, cell cycle inhibitor-779 led to significant inhibition of experimental lung metastasis in vivo. These results suggest that blocking the mTOR/S6K1/4E-BP1 pathway may be an appropriate target for strategies to reduce tumor cell metastasis.

The in vitro and in vivo effects of re-expressing methylated von Hippel-Lindau tumor suppressor gene in clear cell renal carcinoma with 5-aza-2'-deoxycytidine

PURPOSE

Clear cell renal carcinoma (ccRCC) is strongly associated with loss of the von Hippel-Lindau (VHL) tumor suppressor gene. The VHL gene is functionally lost through hypermethylation in up to 19% of sporadic ccRCC cases. We theorized that re-expressing VHL silenced by methylation in ccRCC cells, using a hypo-methylating agent, may be an approach to treatment in patients with this type of cancer. We test the ability of two hypo-methylating agents to re-express VHL in cell culture and in mice bearing human ccRCC and evaluate the effects of re-expressed VHL in these models.

EXPERIMENTAL DESIGN

Real-time reverse transcription-PCR was used to evaluate the ability of zebularine and 5-aza-2'-deoxycytidine (5-aza-dCyd) to re-express VHL in four ccRCC cell lines with documented VHL gene silencing through hypermethylation. We evaluated if the VHL re-expressed after hypo-methylating agent treatment could recreate similar phenotypic changes in ccRCC cells observed when the VHL gene is re-expressed via transfection in cell culture and in a xenograft mouse model. Finally we evaluate global gene expression changes occurring in our cells, using microarray analysis.

RESULTS

5-Aza-dCyd was able to re-express VHL in our cell lines both in culture and in xenografted murine tumors. Well described phenotypic changes of VHL expression including decreased invasiveness into Matrigel, and decreased vascular endothelial growth factor and glucose transporter-1 expression were observed in the treated lines. VHL methylated ccRCC xenografted tumors were significantly reduced in size in mice treated with 5-aza-dCyd. Mice bearing nonmethylated but VHL-mutated tumors showed no tumor shrinkage with 5-aza-dCyd treatment.

CONCLUSION

Hypo-methylating agents may be useful in the treatment of patients having ccRCC tumors consisting of cells with methylated VHL.

Effect of the M(s) transformation temperature on the wear behaviour of NiTi shape memory alloys for articular prosthesis

The main objective of this work has been the characterisation and correlation of the wear behaviour of the NiTi shape memory alloys in their different phases. The weight losses for the different alloys in function of the present phase, and of the M(s) transformation temperature are studied. Adhesive wear tests, Pin-on-Disk, according to the ASTM-G99 standard have been carried out. The thermoelastic martensitic transformations that cause the super-elastic effect, the reorientation and coalescence of martensitic plates and the damping effect promotes a high ability to accommodate large deformations without generating permanent damages that causes the wear. The resulting plastic deformation may be accumulated during wear process without generating fracture. The results show that the wear resistance is mainly dependent of the M(s) transformation temperature for both alloys. For the NiTi alloys also the Ni atomic percentage and the hardness of the alloys are important parameters in the wear behavior.