An inhibitor of proteasome beta 2 sites sensitizes myeloma cells to immunoproteasome inhibitors

Bio-organic Synthesi

The Akt Pathway: Molecular Targets for Anti-Cancer Drug Development

The serine/threonine kinase Akt functions intracellularly as a cardinal nodal point for a constellation of converging upstream signaling pathways, which involve stimulation of receptor tyrosine kinases such as IGF-IR, HER2/Neu, VEGF-R, PDGF-R), and an assembly of membrane-localized complexes of receptor-PI-3K and activation of Akt through the second messenger PIP 3. The integration of these intracellular signals at the level of Akt and its kinase activity, regulates the phosphorylation of its several downstream effectors, such as NF-κB, mTOR, Forkhead, Bad, GSK-3 and MDM-2. These phosphorylation events in turn mediate the effects of Akt on cell growth, proliferation, protection from pro-apoptotic stimuli, and stimulation of neoangiogenesis. Because Akt and its upstream regulators are deregulated in a wide range of solid tumors and hematologic malignancies, and in view of the aforementioned biologic sequelae of this pathway, the Akt pathway is considered a key determinant of biologic aggressiveness of these tumors, and a major potential target for novel anti-cancer therapies. This review focuses on ongoing translational efforts to therapeutically target Akt and its biologic sequelae, either at the level of Akt itself or at the levels of its upstream regulators and downstream effectors. Because Akt is also important for proliferative and anti-apoptotic signaling pathways critical for normal cells, particular emphasis is placed on the fine-tuning the targeting of individual components of this pathway to maximize the therapeutic index of anti-cancer strategies based on the PI-3K/Akt pathway

Skin manifestations of cushing disease in children and adolescents before and after the resolution of hypercortisolemia

Cushing disease (CD) is a common cause of endogenous hypercortisolism in childhood. Its skin manifestations include striae, facial acne, hirsutism, acanthosis nigricans, fungal infections, hyperpigmentation and easy bruisability. We followed 36 children and adolescents with CD (14 boys and 22 girls), to define the natural history of skin disease in endogenous hypercortisolism. Physical examination and 24 hour urinary free cortisol (UFC) and 17-hydroxycorticosteroid (17-OHS) excretion values were obtained preoperatively and quarterly for 18 months. Preoperatively our patients exhibited purple subcutaneous striae (77.7%), steroid-induced acne (58.3%), hirsutism (63.7% of the 22 girls), acanthosis nigricans (27.7%), ecchymoses (27.7%), hyperpigmentation (16.6%), and fungal infections (11.1%). The levels of UFC and 17-OHS preoperatively were 351.84 ± 243.85 μg/m2/day (mean ± SD) and 17.92 ± 7.86 mg/g creatinine/day, respectively. No correlation was found between these levels and the severity of the lesions. All patients were cured. Symptoms decreased dramatically within the 3 postoperative months and progressively disappeared within the first year of the follow-up period with the exception of light-colored striae; they were present in 5.6% of the patients at 18 months postoperatively. No acanthosis nigricans or hyperpigmentation were observed at 3 months postoperatively. Hirsutism was not present at 9 months postoperatively. We conclude that in children with CD the skin is affected at multiple sites; however, the severity of the manifestations does not correlate with the biochemical indices of the disease. With the exception of striae, cutaneous effects of endogenous hypercortisolism completely heal within the first year after surgical cure of the disease

Management of Relapsed and Relapsed Refractory Myeloma

Studies of bortezomib, thalidomide, and lenalidomide have shown promising clinical activity in relapsed/refractory multiple myeloma (MM). Bortezomib alone and in combination with other agents is associated with high response rates, consistently high rates of complete response, and a predictable and manageable profile of adverse events. Thalidomide-based regimens have also shown substantial clinical activity. The accumulating experience from ongoing trials of bortezomib/lenalidomide/dexamethasone combinations in patients who have relapsed/refractory or newly diagnosed MM will provide critical information that will determine the possible role of this combination as the basic backbone for combination regimens for management of advanced MM. © 2007 Elsevier Inc. All rights reserved

Fas signaling in thyroid carcinomas is diverted from apoptosis to proliferation

Purpose: The death receptor Fas is present in thyroid carcinomas, yet fails to trigger apoptosis. Interestingly, Fas has been reported to be actually overexpressed in papillary thyroid carcinomas, suggesting that it may confer a survival advantage. Experimental Design: We investigated the expression and activation status of Fas pathway mediators in thyroid carcinoma cell lines and tumor specimens. Results: All cell lines tested express Fas-associated death domain, procaspase-8, procaspase-9, and procaspase-3; resistance to Fas-mediated apoptosis could not be attributed to lack of any of these apoptosis mediators. Moreover, Fas death domain mutations were not found in our study. The proteasome inhibitors MG132 and PS-341 (bortezomib, Velcade), which lead to accumulation of the nuclear factor κB (NF-κB) inhibitor IκB, did not sensitize SW579 cells to Fas-mediated apoptosis, suggesting that resistance to Fas-mediated apoptosis is not due to proteasome or NF-κB activity. Cross-linking of Fas in vitro induced recruitment of Fas-associated death domain-like interleukin-1β-converting enzyme inhibitory protein (FLIP) instead of procaspase-8. Inhibition of FLIP expression with a FLIP antisense oligonucleotide resulted in significant sensitization to Fas-mediated apoptosis. Fas cross-linking promoted BrdUrd incorporation; activated the mitogen-activated protein kinase/extracellular signal-regulated kinase kinase/extracellular signal-regulated kinase, NF-κB, and activator protein-1 pathways in thyroid carcinoma cells in vitro; and protected cells from tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis. We also found that good prognosis papillary thyroid carcinoma specimens exhibited higher immunoreactivity for cleaved (activated) caspase-8 than poor prognosis tumors. Conclusions: In thyroid carcinomas, the proteolytic cleavage and activation of caspase-8 depends on the balance between expression levels for procaspase-8 and FLIP and correlates with favorable clinical prognosis. Fas may actually stimulate proliferation and confer a survival advantage to thyroid cancer cells. © 2006 American Association for Cancer Research

Epidermal growth factor receptor as a therapeutic target in human thyroid carcinoma: Mutational and functional analysis

Context: The epidermal growth factor receptor (EGFR), a transmembrane tyrosine kinase (TK) receptor that mediates proliferation and survival signaling, is expressed in a wide variety of normal and neoplastic tissues. EGFR inhibitors have produced objective responses in patients with non-small-cell lung carcinomas harboring activating EGFR TK domain somatic mutations. Objective and Methods: Because the EGFR pathway has been reported to be important for the pathophysiology of thyroid carcinoma, we investigated the expression and mutational status of EGFR in 14 thyroid carcinoma cell lines as well as its functional role by evaluating their in vitro sensitivity to AEE788, a new dual-family EGFR/ErbB2 and vascular endothelial growth factor receptor TK inhibitor. We also evaluated the mutational status, mRNA and protein expression, as well as phosphorylation status of EGFR in a panel of thyroid carcinoma specimens. Results: EGFR expression and phosphorylation in the thyroid carcinoma cell lines and tissue specimens were present but not stronger than in noncancerous thyroid tissue. EGFR TK domain mutations were detected in two of 62 histological specimens (3.2%) but not in cell lines. All thyroid carcinoma cell lines were significantly less sensitive (IC50 at least 25-fold higher) in vitro to AEE788 than a primary culture of EGFR-mutant lung carcinoma cells. Conclusions: Thyroid carcinoma cells overall are poorly responsive to clinically relevant concentrations of AEE788 in vitro. The presence of EGFR-activating TK domain mutations may identify a small minority of thyroid cancer patients that may benefit from EGFR inhibitors, but additional preclinical evidence of efficacy is needed. Copyright © 2006 by The Endocrine Society

Antitumor effects of the proteasome inhibitor bortezomib in medullary and anaplastic thyroid carcinoma cells in vitro

Context: The ubiquitin-proteasome pathway is a major pathway for degradation of intracellular proteins. Proteasome inhibitors constitute a novel class of antitumor agents with preclinical and clinical evidence of activity against hematological malignancies and solid tumors. The proteasome inhibitor bortezomib (PS-341, Velcade) has been approved by the Food and Drug Administration for the treatment of multiple myeloma and is being studied intensely in several other malignancies. Its mechanism of action is complex but appears to include the inhibition of inhibitory-κB degradation, which leads to inactivation of the transcriptional factor nuclear factor-κB (NF-κB). NF-κB has been implicated in the pathophysiology of the most aggressive forms of thyroid carcinoma, i.e. medullary and anaplastic. Objective and Methods: We evaluated the effect of bortezomib on a panel of thyroid carcinoma cell lines, originating from papillary, follicular, anaplastic, and medullary carcinomas. Results: Bortezomib induced apoptosis in medullary and anaplastic cell lines with IC50 values well within the range of clinically achievable concentrations and much lower than respective IC50 values for other solid malignancies. Bortezomib inhibited NF-κB activity; increased p53, p21, and jun expression; and induced caspase-dependent apoptosis. Sensitivity of thyroid carcinoma cells to bortezomib was partially decreased by overexpression of Bcl-2 or treatment with IGF-I, whereas the combination of bortezomib with chemotherapy (doxorubicin) was synergistic. Conclusions: These data provide both insights into the molecular mechanisms of antitumor activity of proteasome inhibitors and the rationale for future clinical trials of bortezomib, alone or in combination with conventional chemotherapy, to improve patient outcome in medullary and anaplastic thyroid carcinomas. Copyright © 2006 by The Endocrine Society

Mutational analysis of the BRAF, RAS and EGFR genes in human adrenocortical carcinomas

The serine/threonine kinase B-Raf plays a key role in the Ras/Raf/MEK/ ERK pathway that relays extracellular signals for cell proliferation and survival. Several types of human malignancies harbor activating BRAF mutations, most frequently a V600E substitution. The epidermal growth factor receptor (EGFR), a transmembrane tyrosine kinase (TK) receptor that mediates proliferation and survival signaling, is expressed in a wide variety of normal and neoplastic tissues. EGFR inhibitors have produced objective responses in patients with non-small cell lung carcinomas harboring activating EGFR TK domain somatic mutations. We evaluated the presence of mutations in BRAF (exons 11 and 15), KRAS (exons 1 and 2), NRAS (exons 1 and 2), and EGFR (exons 18-21) in adrenal carcinomas (35 tumor specimens and two cell lines) by DNA sequencing. BRAF mutations were found in two carcinomas (5.7%). Four carcinomas (11.4%) carried EGFR TK domain mutations. One specimen carried a KRAS mutation, and another carried two NRAS mutations. No mutations were found in the two adrenocortical cell lines. BRAF- and EGFR-mutant tumor specimens exhibited stronger immunostaining for the phosphorylated forms of the MEK and ERK kinases than their wild-type counterparts. EGFR-mutant carcinomas exhibited increased phosphorylation of EGFR (Tyr 992) compared with wild-type carcinomas. We conclude that BRAF, RAS, and EGFR mutations occur in a subset of human adrenocortical carcinomas. Inhibitors of the Ras/Raf/MEK/ERK and EGFR pathways represent candidate targeted therapies for future clinical trials in carefully selected patients with adrenocortical carcinomas harboring respective activating mutations. © 2009 Society for Endocrinology

Human retinoblastoma cells are resistant to apoptosis induced by death receptors: Role of caspase-8 gene silencing

PURPOSE. Fas ligand (FasL) and TNF-related apoptosis-inducing ligand (TRAIL)/Apo2L are members of the TNFα family that can trigger apoptosis in susceptible cells via respective death receptors (DRs). FasL cross-links its receptor Fas, resulting in recruitment and proteolytic activation of caspase-8, which initiates the downstream apoptotic cascade. TRAIL signals through its receptors DR4 and DR5, which can activate caspase-8 as well. This study was undertaken to investigate the functional status of the FasL and TRAIL apoptotic pathways in retinoblastoma (Rb) cells. METHODS. The human Rb cell lines Y79 and WERI-Rb1 were evaluated for their response to the Fas cross-linking antibody CH11 and recombinant TRAIL, as well as for cell surface presence and mutational status of Fas, DR4, and DR5 by flow cytometry and genomic DNA sequencing, respectively. The expression of caspase-8 and its inhibitor FLIP, as well as their recruitment to the DR signaling complex were studied by immunoblot analysis. RESULTS. Rb cells express Fas, DR4, and DR5 on their surfaces, yet were resistant to DR-mediated apoptosis. This was not due to DR mutations or secretion of the soluble decoy Fas, anti-apoptotic NF-κB activity, or FLIP overexpression, but to the absence of caspase-8 expression. The demethylating agent 5-aza-2′-deoxycytidine restored caspase-8 expression and sensitivity to DR-mediated apoptosis. CONCLUSIONS. Rb cells are resistant to DR-mediated apoptosis because of a deficiency in caspase-8 expression secondary to epigenetic gene silencing by overmethylation. The data help delineate the apoptotic pathways in Rb cells and suggest that the combination of demethylating agents with DR-activating modalities, such as TRAIL receptor monoclonal antibodies, may benefit patients with retinoblastoma