The investigation of lipoxygenases as therapeutic targets in malignant pleural mesothelioma

Advanced malignant pleural mesothelioma (MPM) has an extremely poor prognosis with limited chemotherapy options, therefore the identification of new therapeutic targets would aid in disease management. Arachidonic acid is metabolised by cyclooxygenase and lipoxygenase enzymes. The lipoxygenase isoenzymes 5-LOX and 12-LOX have been implicated in carcinogenesis. We aimed to examine 5-LOX and 12-LOX protein expression in a large retrospective series of mesothelioma samples. Further to this, the in vitro cytotoxic effects of lipoxygenase pathway inhibitors were investigated in mesothelioma cells. Archival samples from 83 patients with MPM were examined by immunohistochemistry for expression of the 5-LOX and 12-LOX proteins. The MTS assay was used to assess cell viability following 72h treatment with the lipoxygenase pathway inhibitors baicalein, licofelone, MK-886 and zileuton in the MPM cell lines NCI-H2052, NCI-H2452 and MSTO-211H. Positive 12-LOX protein expression was recorded in 69/83 (83%) and positive 5-LOX expression was observed in 56/77 (73%) of MPM tissue samples. Co-expression of 5-LOX with 12-LOX was seen in 46/78 (58%) of MPM samples. Positive expression of 5-LOX, 12-LOX and COX-2 proteins was identified in the NCI-H2052, NCI-H2452 and MSTO-211H MPM cell lines. Baicalein (12-LOX and 15-LOX inhibitor) was effective in 3/3 MPM cell lines at low concentrations with an IC50 range of 9.6μM to 20.7μM. We have demonstrated that the 5-LOX and 12-LOX proteins are expressed in a significant proportion of MPM samples (73% and 83% respectively) and may represent novel therapeutic targets in this disease. We have demonstrated that the inhibition of the LOX pathway using baicalein may be effective as a novel treatment for MPM, however further human pharmacokinetic studies are required in order to establish whether the concentration used in vitro is clinically achievable

Clinical response to primary letrozole therapy in elderly patients with early breast cancer : possible role for p53 as a biomarker

Primary tamoxifen therapy has been widely used to treat elderly women with ER-positive breast cancer in the past. Aromatase inhibitors may be more beneficial than tamoxifen when used as primary endocrine therapy in elderly patients. We aimed to retrospectively evaluate a series of elderly women with ER-positive breast cancer treated with primary letrozole therapy as sole therapy with a minimum of 5 years follow up. To identify possible predictive biomarkers a pilot immunohistochemical analysis was performed to assess the expression of PR, HER2, EGFR, BCL2 and p53. A total of 45 women, aged more than 70 years with a diagnosis of ER-positive breast cancer that was treated with primary letrozole therapy were identified. A case note review was undertaken to obtain clinical information. Formalin fixed paraffin embedded tumour tissue from diagnostic core biopsies was available for all patients. Immunohistochemical analysis was performed to establish the protein expression status of p53, PR, HER2, EGFR and BCL2. The mean age of the 45 patients was 87 years (range 70–101). Clinical benefit was seen in 60% of the patients. Median progression free survival was 53 months (95% CI – 34–72) and the median time to progression was 43 months (95% CI – 22–64). BCL2 was expressed in 45/45 (100%); PR in 38/45 (84%); EGFR in 13/45 (28%); HER2 in 9/45 (20%) and p53 in 5/45 (11%) of tissue samples. Positive expression of p53 was associated with poor progression free survival (p = 0.03) in this pilot study. This study demonstrates that letrozole as sole treatment appears to be a suitable treatment option for elderly patients with ER-positive breast cancer who are not fit for, or decline, surgery. The analysis of p53 in a larger study is warranted in order to assess its role as a biomarker in this patient group

Telomere dysfunction accurately predicts clinical outcome in chronic lymphocytic leukaemia, even in patients with early stage disease

© 2014 John Wiley & Sons Ltd. Defining the prognosis of individual cancer sufferers remains a significant clinical challenge. Here we assessed the ability of high-resolution single telomere length analysis (STELA), combined with an experimentally derived definition of telomere dysfunction, to predict the clinical outcome of patients with chronic lymphocytic leukaemia (CLL). We defined the upper telomere length threshold at which telomere fusions occur and then used the mean of the telomere 'fusogenic' range as a prognostic tool. Patients with telomeres within the fusogenic range had a significantly shorter overall survival (P  <  0·0001; Hazard ratio [HR] = 13·2, 95% confidence interval [CI]  = 11·6-106·4) and this was preserved in early-stage disease patients (P  <  0·0001, HR=19·3, 95% CI = 17·8-802·5). Indeed, our assay allowed the accurate stratification of Binet stage A patients into those with indolent disease (91% survival at 10 years) and those with poor prognosis (13% survival at 10 years). Furthermore, patients with telomeres above the fusogenic mean showed superior prognosis regardless of their IGHV mutation status or cytogenetic risk group. In keeping with this finding, telomere dysfunction was the dominant variable in multivariate analysis. Taken together, this study provides compelling evidence for the use of high-resolution telomere length analysis coupled with a definition of telomere dysfunction in the prognostic assessment of CLL

Lck is a relevant target in chronic lymphocytic leukaemia cells whose expression variance is unrelated to disease outcome.

Pathogenesis of chronic lymphocytic leukaemia (CLL) is contingent upon antigen receptor (BCR) expressed by malignant cells of this disease. Studies on somatic hypermutation of the antigen binding region, receptor expression levels and signal capacity have all linked BCR on CLL cells to disease prognosis. Our previous work showed that the src-family kinase Lck is a targetable mediator of BCR signalling in CLL cells, and that variance in Lck expression associated with ability of BCR to induce signal upon engagement. This latter finding makes Lck similar to ZAP70, another T-cell kinase whose aberrant expression in CLL cells also associates with BCR signalling capacity, but also different because ZAP70 is not easily pharmacologically targetable. Here we describe a robust method of measuring Lck expression in CLL cells using flow cytometry. However, unlike ZAP70 whose expression in CLL cells predicts prognosis, we find Lck expression and disease outcome in CLL are unrelated despite observations that its inhibition produces effects that biologically resemble the egress phenotype taken on by CLL cells treated with idelalisib. Taken together, our findings provide insight into the pathobiology of CLL to suggest a more complex relationship between expression of molecules within the BCR signalling pathway and disease outcome

The proteomic analysis of resistance to anticancer therapy in human breast cancer

Resistance to anticancer therapy represents a major barrier in the successful management of human breast cancer. The identification of novel biomarkers that correlate with treatment response would increase our understanding of the resistance mechanisms and may allow therapy to be tailored on an individual patient basis. Those patients unlikely to respond to a particular treatment strategy would be spared the serious life-threatening side effects for no therapeutic gain. The immediate implementation of a more appropriate treatment strategy may also prevent disease progression and such biomarkers would also suggest new drug targets and/or sensitising agents for future therapeutic intervention. The primary aim of this thesis was to establish and optimise two-dimensional gel electrophoresis (2DE) and matrix-assisted laser desorption/ ionisation time-of-flight mass spectrometry (MALDI-TOF MS) and to exploit this global proteomics approach to identify molecular markers associated with resistance to anticancer therapy in human breast cancer cells. This technique was applied to compare the MCF7 cell line with novel derivatives displaying significant resistance to cisplatin (MCF7CR) and radiotherapy (MCF740Gy). Differentially expressed proteins were identified by MALDI-TOF MS analysis. Several molecular markers have been identified, which may play a role in resistance to anticancer therapy. Western blotting was used to confirm the expression of selected targets and to ensure the accuracy of protein identification. Examples of those targets which were confirmed by western blotting include GST-M3, cytokeratin 17, peroxiredoxin 4 and HSP27 (which were associated with cisplatin resistance) and L-Plastin, GST-M3 and cytokeratin 17 (which were associated with radio-resistance). These provide interesting targets and are worthy of further studies. Although 2DE-MALDI-TOF MS remains the gold standard for the global analysis of protein expression this technique is associated with several drawbacks. The antibody microarray is a powerful new technique designed to overcome many of these drawbacks and provides complementary information. Antibody microarrays were applied to identify further molecular markers associated with resistance to anticancer therapy in human breast cancer cells. The MDA-MB-231 cell line and a novel derivative (MDAMB- 231DR) displaying significant resistance to doxorubicin were analysed using Panorama Cell Signalling antibody microarrays (Sigma-Aldrich) comprised of 224 antibodies. Several proteins were associated with resistance to doxorubicin and some proteins were confirmed by western blotting. These targets included p-ERK, cyclin D2 and cyclin B 1. The technique was subsequently extended using the Labvision Antibody Microarray Kit (Neomarkers) to analyse the MCF7 parental cell line and the derivative (MCF740Gy) displaying significant resistance to radiotherapy. The Labvision antibody microarrays were comprised of 720 antibodies. Results indicated that this kit requires further optimisation and a preliminary analysis of the data revealed that further developmental and statistical work is required for interpretation of the results. This thesis has generated a list of potential candidate proteins, which may play a role in the development of resistance to anticancer therapy. Some of these targets overlap between different treatment modalities and have been confirmed by western blotting. Further work is now required in order to determine the functional relevance of these interesting targets. Ultimately, overcoming resistance to both chemotherapy and radiotherapy would represent a major advance in the effective management of breast cancer today.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Targeted epidermal growth factor receptor therapy in malignant pleural mesothelioma: where do we stand?

The median survival for patients with malignant pleural mesothelioma remains extremely poor and there is a need for the development of more effective treatment modalities. The epidermal growth factor receptor is frequently over-expressed in malignant pleural mesothelioma samples and therefore may be a potential therapeutic target. Targeted EGFR therapy has been successful in non-small cell lung cancer using small molecule tyrosine kinase inhibitors and in colorectal cancer using monoclonal anti-EGFR antibodies. However, phase II clinical trials based on EGFR tyrosine kinase inhibitor therapy have so far not shown promise in mesothelioma. This review includes a background to targeted EGFR treatment strategies, explores putative therapy resistance mechanisms, including the role of predictive biomarkers, and describes the current status of targeted EGFR therapeutic strategies for mesothelioma patients

The kinin–kallikrein system: physiological roles, pathophysiology and its relationship to cancer biomarkers

The kinin–kallikrein system (KKS) is an endogenous multiprotein cascade, the activation of which leads to triggering of the intrinsic coagulation pathway and enzymatic hydrolysis of kininogens with the consequent release of bradykinin-related peptides. This system plays a crucial role in inflammation, vasodilation, smooth muscle contraction, cardioprotection, vascular permeability, blood pressure control, coagulation and pain. In this review, we will outline the physiology and pathophysiology of the KKS and also highlight the association of this system with carcinogenesis and cancer progression