Examination of thromboxane synthase as a prognostic factor and therapeutic target in non-small cell lung cancer

Background: Thromboxane synthase (TXS) metabolises prostaglandin H2 into thromboxanes, which are biologically active on cancer cells. TXS over-expression has been reported in a range of cancers, and associated with a poor prognosis. TXS inhibition induces cell death in-vitro, providing a rationale for therapeutic intervention. We aimed to determine the expression profile of TXS in NSCLC and if it is prognostic and/or a survival factor in the disease. Methods: TXS expression was examined in human NSCLC and matched controls by western analysis and IHC. TXS metabolite (TXB 2) levels were measured by EIA. A 204-patient NSCLC TMA was stained for COX-2 and downstream TXS expression. TXS tissue expression was correlated with clinical parameters, including overall survival. Cell proliferation/survival and invasion was examined in NSCLC cells following both selective TXS inhibition and stable TXS over-expression. Results: TXS was over-expressed in human NSCLC samples, relative to matched normal controls. TXS and TXB 2levels were increased in protein (p < 0.05) and plasma (p < 0.01) NSCLC samples respectively. TXS tissue expression was higher in adenocarcinoma (p < 0.001) and female patients (p < 0.05). No significant correlation with patient survival was observed. Selective TXS inhibition significantly reduced tumour cell growth and increased apoptosis, while TXS over-expression stimulated cell proliferation and invasiveness, and was protective against apoptosis. Conclusion: TXS is over-expressed in NSCLC, particularly in the adenocarcinoma subtype. Inhibition of this enzyme inhibits proliferation and induces apoptosis. Targeting thromboxane synthase alone, or in combination with conventional chemotherapy is a potential therapeutic strategy for NSCLC. © 2011 Cathcart et al; licensee BioMed Central Ltd.

Ran is a potential therapeutic target for cancer cells with molecular changes associated with activation of the PI3K/Akt/mTORC1 and Ras/MEK/ERK pathways

Purpose Cancer cells have been shown to be more susceptible to Ran knockdown than normal cells. We now investigate whether Ran is a potential therapeutic target of cancers with frequently found mutations that lead to higher Ras/MEK/ERK [mitogen-activated protein/extracellular signal-regulated kinase (ERK; MEK)] and phosphoinositide 3-kinase (PI3K)/Akt/mTORC1 activities. Experimental Design Apoptosis was measured by flow cytometry [propidium iodide (PI) and Annexin V staining] and MTT assay in cancer cells grown under different conditions after knockdown of Ran. The correlations between Ran expression and patient survival were examined in breast and lung cancers. Results Cancer cells with their PI3K/Akt/mTORC1 and Ras/MEK/ERK pathways inhibited are less susceptible to Ran silencing-induced apoptosis. K-Ras-mutated, c-Met-amplified, and Pten-deleted cancer cells are also more susceptible to Ran silencing-induced apoptosis than their wild-type counterparts and this effect is reduced by inhibitors of the PI3K/Akt/mTORC1 and MEK/ERK pathways. Overexpression of Ran in clinical specimens is significantly associated with poor patient outcome in both breast and lung cancers. This association is dramatically enhanced in cancers with increased c-Met or osteopontin expression, or with oncogenic mutations of K-Ras or PIK3CA, all of which are mutations that potentially correlate with activation of the PI3K/Akt/mTORC1 and/or Ras/MEK/ERK pathways. Silencing Ran also results in dysregulation of nucleocytoplasmic transport of transcription factors and downregulation of Mcl-1 expression, at the transcriptional level, which are reversed by inhibitors of the PI3K/Akt/mTORC1 and MEK/ERK pathways. Conclusion Ran is a potential therapeutic target for treatment of cancers with mutations/changes of expression in protooncogenes that lead to activation of the PI3K/Akt/mTORC1 and Ras/MEK/ERK pathways. ©2011 AACR.

KAT5 (Tip60) is a potential therapeutic target in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare aggressive cancer of the pleura. Asbestos exposure (through inhalation) is the most well established risk factor for mesothelioma. The current standard of care for patients suffering from MPM is a combination of cisplatin and pemetrexed (or alternatively cisplatin and raltitrexed). Most patients, however, die within 24 months of diagnosis. New therapies are therefore urgently required for this disease. Lysine acetyltransferases (KATs) including KAT5 have been linked with the development of cisplatin resistance. This gene may therefore be altered in MPM and could represent a novel candidate target for intervention. Using RT-PCR screening the expression of all known KAT5 variants was found to be markedly increased in malignant tumors compared to benign pleura. When separated according to histological subtype, KAT5 was significantly overexpressed in both the sarcomatoid and biphasic subgroups for all transcript variants. A panel of MPM cell lines including the normal pleural cells LP9 and Met5A was screened for expression of KAT5 variants. Treatment of cells with a small molecule inhibitor of KAT5 (MG-149) caused significant inhibition of cellular proliferation (p<0.0001), induction of apoptosis and was accompanied by significant induction of pro-inflammatory cytokines/chemokines.

Cytochrome P4504f, a potential therapeutic target limiting neuroinflammation

Inflammatory processes are involved in the pathogenesis and/or progression of acute central nervous system (CNS) infection, traumatic brain injury and neurodegenerative disorders among others indicating the need for novel strategies to limit neuroinflammation. Eicosanoids including leukotrienes, particularly leukotriene B-4 (LTB4) are principle mediator(s) of inflammatory response, initiating and amplifying the generation of cytokines and chemokines. Cytochrome P450 (Cyp), a family of heme proteins mediate metabolism of xenobiotics and endogenous compounds, such as eicosanoids and leukotrienes. Cytochrome P4504F (Cyp4f) subfamily includes five functional enzymes in mouse. We cloned and expressed the mouse Cyp4f enzymes, assayed their relative expression in brain and examined their ability to hydroxylate the inflammatory cascade prompt LTB4 to its inactive 20-hydroxylated product. We then examined the role of Cyp4fs in regulating inflammatory response in vitro, in microglial cells and in vivo, in mouse brain using lipopolysacharide (LPS), as a model compound to generate inflammatory response. We demonstrate that mouse brain Cyp4fs are expressed ubiquitously in several cell types in the brain, including neurons and microglia, and modulate inflammatory response triggered by LPS, in vivo and in microglial cells, in vitro through metabolism of LTB4 to the inactive 20-hydroxy LTB4. Chemical inhibitor or shRNA to Cyp4fs enhance and inducer of Cyp4fs attenuates inflammatory response. Further, induction of Cyp4f expression lowers LTB4 levels and affords neuroprotection in microglial cells or mice exposed to LPS. Thus, catalytic activity of Cyp4fs is a novel target for modulating neuroinflammation through hydroxylation of LTB4. (C) 2011 Elsevier Inc. All rights reserved.

RAD51 as a potential biomarker and therapeutic target for pancreatic cancer

Chemotherapy is a very important therapeutic strategy for cancer treatment. The failure of conventional and molecularly targeted chemotherapeutic regimes for the treatment of pancreatic cancer highlights a desperate need for novel therapeutic interventions. Chemotherapy often fails to eliminate all tumor cells because of intrinsic or acquired drug resistance, which is the most common cause of tumor recurrence. Overexpression of RAD51 protein, a key player in DNA repair/recombination has been observed in many cancer cells and its hyperexpression is implicated in drug resistance. Recent studies suggest that RAD51 overexpression contributes to the development, progression and drug resistance of pancreatic cancer cells. Here we provide a brief overview of the available pieces of evidence in support of the role of RAD51 in pancreatic tumorigenesis and drug resistance, and hypothesize that RAD51 could serve as a potential biomarker for diagnosis of pancreatic cancer. We discuss the possible involvement of RAD51 in the drug resistance associated with epithelial to mesenchymal transition and with cancer stem cells. Finally, we speculate that targeting RAD51 in pancreatic cancer cells may be a novel approach for the treatment of pancreatic cancer. (C) 2011 Elsevier B.V. All rights reserved.

Modulation of heat shock transcription factor 1 as a therapeutic target for small molecule intervention in neurodegenerative disease.

Neurodegenerative diseases such as Huntington disease are devastating disorders with no therapeutic approaches to ameliorate the underlying protein misfolding defect inherent to poly-glutamine (polyQ) proteins. Given the mounting evidence that elevated levels of protein chaperones suppress polyQ protein misfolding, the master regulator of protein chaperone gene transcription, HSF1, is an attractive target for small molecule intervention. We describe a humanized yeast-based high-throughput screen to identify small molecule activators of human HSF1. This screen is insensitive to previously characterized activators of the heat shock response that have undesirable proteotoxic activity or that inhibit Hsp90, the central chaperone for cellular signaling and proliferation. A molecule identified in this screen, HSF1A, is structurally distinct from other characterized small molecule human HSF1 activators, activates HSF1 in mammalian and fly cells, elevates protein chaperone expression, ameliorates protein misfolding and cell death in polyQ-expressing neuronal precursor cells and protects against cytotoxicity in a fly model of polyQ-mediated neurodegeneration. In addition, we show that HSF1A interacts with components of the TRiC/CCT complex, suggesting a potentially novel regulatory role for this complex in modulating HSF1 activity. These studies describe a novel approach for the identification of new classes of pharmacological interventions for protein misfolding that underlies devastating neurodegenerative disease.

Ran Is a Potential Therapeutic Target for Cancer Cells with Molecular Changes Associated with Activation of the PI3K/Akt/mTORC1 and Ras/MEK/ERK Pathways

Purpose: Cancer cells have been shown to be more susceptible to Ran knockdown than normal cells. We nowinvestigate whether Ran is a potential therapeutic target of cancers with frequently found mutations that lead to higher Ras/MEK/ERK [mitogen-activated protein/extracellular signal-regulated kinase (ERK; MEK)] and phosphoinositide 3-kinase (PI3K)/Akt/mTORC1 activities.

Nuclear factor-kappaB as a potential therapeutic target for the novel cytotoxic agent LC-1 in acute myeloid leukaemia

Nuclear factor-kappaB (NF-kappaB) has been implicated in a number of malignancies and has been suggested to be a potential molecular target in the treatment of leukaemia. This study demonstrated the constitutive activation of NF-kappaB in human myeloid blasts and a clear correlation between NF-kappaB expression and in vitro cytoprotection. High NF-kappaB expression was found in many of the poor prognostic acute myeloid leukaemia (AML) subtypes, such as French-American-British classification M0 and M7, and the poor cytogenetic risk group. The in vitro effects of LC-1, a novel dimethylamino-parthenolide analogue, were assessed in 62 primary untreated AML samples. LC-1 was found to be cytotoxic to AML cells in a dose-dependent manner, mediated through the induction of apoptosis. The median drug concentration necessary to kill 50% of the cells was 4.5 micromol/l for AML cells, compared with 12.8 micromol/l for normal marrow cells. LC-1 was shown to reduce the five individual human NF-kappaB Rel proteins in a dose-dependent manner. The subsequent inhibition of many NF-kappaB-regulated cytokines was also demonstrated. Importantly, sensitivity to LC-1 was correlated with the basal NF-kappaB activity. Consequently, LC-1 treatment provides a proof of principle for the use of NF-kappaB inhibitors in the treatment of AML.