Antiangiogenic potential of the Mammalian target of rapamycin inhibitor temsirolimus

: Mammalian target of rapamycin (mTOR) is increasingly recognized as a master regulator of fundamental cellular functions, whose deregulation may underlie neoplastic transformation and progression. Hence, mTOR has recently emerged as a promising target for therapeutic anticancer interventions in several human tumors, including breast cancer. Here, we investigated the antiangiogenic potential of temsirolimus (also known as CCI-779), a novel mTOR inhibitor currently in clinical development for the treatment of breast cancer and other solid tumors. Consistent with previous reports, sensitivity to temsirolimus-mediated growth inhibition varied widely among different breast cancer cell lines and was primarily due to inhibition of proliferation with little, if any, effect on apoptosis induction. In the HER-2 gene-amplified breast cancer cell line BT474, temsirolimus inhibited vascular endothelial growth factor (VEGF) production in vitro under both normoxic and hypoxic conditions through inhibition of hypoxia-stimulated hypoxia-inducible factor (HIF)-1alpha expression and transcriptional activation. Interestingly, these effects were also observed in the MDA-MB-231 cell line, independent of its inherent sensitivity to the growth-inhibitory effects of temsirolimus. A central role for mTOR (and the critical regulator of cap-dependent protein translation, eIF4E) in the regulation of VEGF production by BT474 cells was further confirmed using a small interfering RNA approach to silence mTOR and eIF4E protein expression. In addition to its effect on HIF-1alpha-mediated VEGF production, temsirolimus also directly inhibited serum- and/or VEGF-driven endothelial cell proliferation and morphogenesis in vitro and vessel formation in a Matrigel assay in vivo. Overall, these results suggest that antiangiogenic effects may substantially contribute to the antitumor activity observed with temsirolimus in breast cancer

Trastuzumab down-regulates Bcl-2 expression and potentiates apoptosis induction by Bcl-2/Bcl-XL bispecific antisense oligonucleotides in HER-2 gene--amplified breast cancer cells

Purpose: To investigate the possible existence of an antiapoptotic cross-talk between HER-2 and antiapoptotic Bcl-2 family members. Experimental design: Bcl-2 and Bcl-XL expression and apoptosis induction were analyzed in HER-2 gene-amplified (BT474) and nonamplified (ZR 75-1) breast cancer cell lines exposed to trastuzumab, alone or in combination with either Bcl-2/Bcl-XL bispecific antisense oligonucleotides (AS-4625) or the small-molecule Bcl-2 antagonist HA14-1. Results: In addition to HER-2 and epidermal growth factor receptor, trastuzumab down-regulated Bcl-2, but not Bcl-XL, protein, and mRNA expression in BT474 cells. Interestingly, trastuzumab-induced down-regulation of HER-2 and Bcl-2 was also observed in three of five and two of three breast cancer patients undergoing trastuzumab treatment, respectively. Despite Bcl-2 down-regulation, however, trastuzumab only marginally increased the rate of apoptosis (7.3 +/- 3.5%). We therefore investigated whether a combination of AS-4625 and trastuzumab might increase proapoptotic efficiency. AS-4625 treatment of BT474 cells decreased both Bcl-2 and Bcl-XL expression, resulting in a 21 +/- 7% net apoptosis induction; the combination of AS-4625 followed by trastuzumab resulted in a significantly stronger induction of apoptosis (37 +/- 6%, P <0.01) that was not observed with the reverse treatment sequence (trastuzumab followed by AS-4625). Similar results were obtained with the Bcl-2 antagonist HA14-1; indeed, exposure of BT474 cells to HA14-1 followed by trastuzumab resulted in a striking proapoptotic synergism (combination index=0.58 +/- 0.18), as assessed by isobologram analysis. Conclusions: Altogether our findings suggest that combined targeting of HER-2 and Bcl-2 may represent a novel, rational approach to more effective breast cancer therapy

Therapeutic potential of MEK inhibition in acute myelogenous leukemia: rationale for "vertical" and "lateral" combination strategies

: In hematological malignancies, constitutive activation of the RAF/MEK/ERK pathway is frequently observed, conveys a poor prognosis, and constitutes a promising target for therapeutic intervention. Here, we investigated the molecular and functional effects of pharmacological MEK inhibition in cell line models of acute myeloid leukemia (AML) and freshly isolated primary AML samples. The small-molecule, ATP-non-competitive, MEK inhibitor PD0325901 markedly inhibited ERK phosphorylation and growth of several AML cell lines and approximately 70 % of primary AML samples. Growth inhibition was due to G(1)-phase arrest and induction of apoptosis. Transformation by constitutively active upstream pathway elements (HRAS, RAF-1, and MEK) rendered FDC-P1 cells exquisitely prone to PD0325901-induced apoptosis. Gene and protein expression profiling revealed a selective effect of PD0325901 on ERK phosphorylation and compensatory upregulation of the RAF/MEK and AKT/p70( S6K ) kinase modules, potentially mediating resistance to drug-induced growth inhibition. Consequently, in appropriate cellular contexts, both "vertical" (i.e., inhibition of RAF and MEK along the MAPK pathway) and "lateral" (i.e., simultaneous inhibition of the MEK/ERK and mTOR pathways) combination strategies may result in synergistic anti-leukemic effects. Overall, MEK inhibition exerts potent growth inhibitory and proapoptotic activity in preclinical models of AML, particularly in combination with other pathway inhibitors. Deeper understanding of the molecular mechanisms of action of MEK inhibitors will likely translate into more effective targeted strategies for the treatment of AML

Broadly directed virus-specific CD4+ T cell responses are primed during acute hepatitis C infection, but rapidly disappear from human blood with viral persistence

Vigorous proliferative CD4+ T cell responses are the hallmark of spontaneous clearance of acute hepatitis C virus (HCV) infection, whereas comparable responses are absent in chronically evolving infection. Here, we comprehensively characterized the breadth, specificity, and quality of the HCV-specific CD4+ T cell response in 31 patients with acute HCV infection and varying clinical outcomes. We analyzed in vitro T cell expansion in the presence of interleukin-2, and ex vivo staining with HCV peptide-loaded MHC class II tetramers. Surprisingly, broadly directed HCV-specific CD4+ T cell responses were universally detectable at early stages of infection, regardless of the clinical outcome. However, persistent viremia was associated with early proliferative defects of the HCV-specific CD4+ T cells, followed by rapid deletion of the HCV-specific response. Only early initiation of antiviral therapy was able to preserve CD4+ T cell responses in acute, chronically evolving infection. Our results challenge the paradigm that HCV persistence is the result of a failure to prime HCV-specific CD4+ T cells. Instead, broadly directed HCV-specific CD4+ T cell responses are usually generated, but rapid exhaustion and deletion of these cells occurs in the majority of patients. The data further suggest a short window of opportunity to prevent the loss of CD4+ T cell responses through antiviral therapy

Asthme allergique de l'adulte : prise en charge

Asthma is one of the most common chronic diseases in Switzerland. Its prevalence is between 7% and 10% in Western countries and almost half of all asthma patients are sensitized to one or more allergens. It is important to identify this particular group of allergic patients in order to be able to propose a targeted treatment. Due to recent scientific advances, allergologists have gained novel tests to precisely diagnose sensitizations to allergens as well as new treatment options beside allergen avoidance, bronchodilators, topical steroids and desensitization. Here, we summarize the current diagnostic and treatment guidelines for the general practitioner

Identification of an expanded population of activated CD4(+) CD25(+) T cells expressing CD45RO and IL-7R in kidney transplant recipients

Recent studies have shown that CD4+ CD25+ T cells belong to two functionally different T lymphocytes, i.e. regulatory T cells (Treg) or activated T cells (Tact), which can be distinguished based on the expression of CD45RO and IL-7R: Treg (FoxP3+) are CD45RO+ IL-7R- , whereas Tact (FoxP3- ) are CD45RO+ IL- 7R+. In order to determine if a CD4+ CD25+ CD45RO+ IL-7R+ activated T cell population might be identified in kidney transplant recipients, we studied 27 healthy subjects (HS) and 23 kidney recipients, of whom 17 had stable graft function under standard immunosuppression (IS), 5 had biopsy-proven chronic humoral rejection (CHR), and one was a stable "tolerant" patient who had discontinued IS for more than 2 years. Phenotypical analysis by flow cytometry and functional assays by MLR were performed. Overall, the Tact population was found to be significantly increased in 87% of the transplant recipients (mean: 18.8±10.1% of CD4+ CD25+ T cells) compared to HS (mean: 4.5±2.0%; P<0.0001). In the 5 patients with CHR, this Tact population was highly expanded (31.3±9.3%; P<0.0001), whereas it was comparable to HS in the "tolerant" recipient (4.7%). Intermediate levels (16.0±6.9%; P<0.0001) were found in the 17 stable recipients. In CHR, the proliferative capacity of the Tact population was found to be 5-fold higher when stimulated by irradiated donor PBMC as compared to a stimulation by irradiated 3rd party PBMC. After kidney transplantation, an expanded circulating CD4+ CD25+ T cell population characterized by the expression of CD45RO and IL-7R was found in most recipients, particularly in those with CHR. In a patient with long-term operational tolerance, this Tact population was similar to HS. Measuring circulating Tact may become a useful monitoring tool after transplantation

HCV infection after liver transplantation is associated with lower levels of alloreactive CD4+CD25+CD45RO+IL-7R+high+ T cells

Aim: Expression of IL-7R discriminates alloreactive CD4 T cells (Foxp3 negative), from IL-7Rlow regulatory CD4 T cells (Foxp3 positive). Chronic hepatitis C virus infection (HCV) reduces expression of IL-7R on T cells thus promoting persistence of infection. The aim of this study was to analyze the effect of HCV infection on the expression of IL-7R of activated CD4+ T cells in liver transplant patients. Patients and methods: We analyzed PBMC from liver transplant recipients for the expression of CD4, CD25, FoxP3, IL-7R (24 HCV negative and 29 HCV-chronically infected). We compared these data with non-transplanted individuals (52 HCV-chronically infected patients and 38 healthy donors). Results: In HCV-infected liver transplant recipients, levels of CD4+CD25+CD45RO+IL-7R+ T cells were significantly reduced (10.5+/-0.9%) when compared to non-HCV-infected liver transplant recipients (17.6+/-1.4%) (P<0.001), while both groups (HCV-infected and negative transplant recipients) had significantly higher levels than healthy individuals (6.6+/-0.9%) (P<0.0001). After successful antiviral therapy (sustained antiviral response), 6 HCV-infected transplant recipients showed an increase of CD4+CD25+CD45RO+IL-7R+ T cells, reaching levels similar to that of non-HCVinfected recipients (10.73+/-2.63% prior therapy versus 21.7+/-6.3% after clearance of HCV). (P<0.05) In 4 non-responders (i.e. HCVRNA remaining present in serum), levels of CD4+CD25+CD45RO+IL-7R+ T cells remained unmodified during and after antiviral treatment (11.8+/- 3.3% versus 11.3+/-3.3% respectively). Conclusions: Overall, these data indicate that CD4+CD25+CD45RO+IL-7R+ T cells appear to be modulated by chronic HCV infection after liver transplantation. Whether lower levels of alloreactive T cells in HCV-infected liver transplant recipients are associated with a tolerogenic profile remains to be studied

Treatment of primary HIV-1 infection with cyclosporin A coupled with highly active antiretroviral therapy

Primary HIV-1 infection causes extensive immune activation, during which CD4(+) T cell activation supports massive HIV-1 production. We tested the safety and the immune-modulating effects of combining cyclosporin A (CsA) treatment with highly active antiretroviral therapy (HAART) during primary HIV-1 infection. Nine adults with primary HIV-1 infection were treated with CsA along with HAART. At week 8, all patients discontinued CsA but maintained HAART. Viral replication was suppressed to a comparable extent in the CsA + HAART cohort and in 29 control patients whose primary infection was treated with HAART alone. CsA restored normal CD4(+) T cell levels, both in terms of percentage and absolute numbers. The increase in CD4(+) T cells was apparent within a week and persisted throughout the study period. CsA was not detrimental to virus-specific CD8(+) or CD4(+) T cell responses. At week 48, the proportion of IFN-γ–secreting CD4(+) and CD4(+)CCR7(–) T cells was significantly higher in the CsA + HAART cohort than in the HAART-alone cohort. In conclusion, rapid shutdown of T cell activation in the early phases of primary HIV-1 infection can have long-term beneficial effects and establish a more favorable immunologic set-point. Appropriate, immune-based therapeutic interventions may represent a valuable complement to HAART for treating HIV infection