Search

Radiotherapy (RT) plays a fundamental role in the treatment of glioblastoma (GBM). GBM are notoriously invasive and harbor a subpopulation of cells with stem-like features which exhibit upregulation of the DNA damage response (DDR) and are radioresistant. High radiation doses are therefore delivered to large brain volumes and are known to extend survival but also cause delayed toxicity with 50%–90% of patients developing neurocognitive dysfunction. Emerging evidence identifies neuroinflammation as a critical mediator of the adverse effects of RT on cognitive function. In addition to its well-established role in promoting repair of radiation-induced DNA damage, activation of poly(ADP-ribose) polymerase (PARP) can exacerbate neuroinflammation by promoting secretion of inflammatory mediators. Therefore, PARP represents an intriguing mechanistic link between radiation-induced activation of the DDR and subsequent neuroinflammation. PARP inhibitors (PARPi) have emerged as promising new agents for GBM when given in combination with RT, with multiple preclinical studies demonstrating radiosensitizing effects and at least 3 compounds being evaluated in clinical trials. We propose that concomitant use of PARPi could reduce radiation-induced neuroinflammation and reduce the severity of radiation-induced cognitive dysfunction while at the same time improving tumor control by enhancing radiosensitivity.

Purpose Previous work has shown that combining dynamic contrast‐enhanced (DCE)‐MRI and oxygen‐enhanced (OE)‐MRI binary enhancement maps can identify tumor hypoxia. The current work proposes a novel, data‐driven method for mapping tissue oxygenation and perfusion heterogeneity, based on clustering DCE/OE‐MRI data. Methods DCE‐MRI and OE‐MRI were performed on nine U87 (glioblastoma) and seven Calu6 (non‐small cell lung cancer) murine xenograft tumors. Area under the curve and principal component analysis features were calculated and clustered separately using Gaussian mixture modelling. Evaluation metrics were calculated to determine the optimum feature set and cluster number. Outputs were quantitatively compared with a previous non data‐driven approach. Results The optimum method located six robustly identifiable clusters in the data, yielding tumor region maps with spatially contiguous regions in a rim‐core structure, suggesting a biological basis. Mean within‐cluster enhancement curves showed physiologically distinct, intuitive kinetics of enhancement. Regions of DCE/OE‐MRI enhancement mismatch were located, and voxel categorization agreed well with the previous non data‐driven approach (Cohen's kappa = 0.61, proportional agreement = 0.75). Conclusion The proposed method locates similar regions to the previous published method of binarization of DCE/OE‐MRI enhancement, but renders a finer segmentation of intra‐tumoral oxygenation and perfusion. This could aid in understanding the tumor microenvironment and its heterogeneity. Magn Reson Med 79:2236–2245, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Prenylated sequences unlocks the development of new therapeutics as demonstrated for an anticancer agent., Natural prenylated indoles have been proposed as potential anticancer agents. To exploit this discovery for developing new peptide therapeutics, we report the first studies whereby incorporation of prenylated indoles into primary sequences has been achieved. We developed a route to synthesise Nα-Fmoc-protected tryptophan derivatives in which the prenyl group is linked to the N-indole core, using Pd(ii)-mediated C–H functionalisation of 2-methyl-2-butene. Based on the Substance P antagonist G (SPG), a well-known Small Cell Lung Cancer (SCLC) anticancer agent, we designed a new penta-peptide sequence to include a prenyl moiety on one of the tryptophan residues. The N-tert-prenylated tryptophan analogue was assembled into the pentameric peptide using standard solid phase peptide synthesis or liquid phase synthesis by fragment coupling. In vitro screening showed that the N-tert-prenylation of the indole ring on the tryptophan residue located near the C-terminal of the penta-peptide enhanced the cytotoxicity against H69 (IC50 = 2.84 ± 0.14 μM) and DMS79 (IC50 = 4.37 ± 0.44 μM) SCLC cell lines when compared with the unmodified penta-peptide (H69, IC50 = 30.74 ± 0.30 μM and DMS79, IC50 = 23.00 ± 2.07 μM) or the parent SPG sequence (IC50 > 30 μM, both cell lines). SCLC almost invariably relapses with therapy-resistant disease. The DMS79 cell line was established from a patient following treatment with a number of chemotherapeutics (cytoxan, vincristine and methotrexate) and radiation therapy. Treating DMS79 tumour-bearing nude mice provided a human xenograft model of drug resistance to test the efficacy of the prenylated peptide. A low dose (1.5 mg kg–1) of the prenylated peptide was found to reduce tumour growth by ∼30% (P < 0.05) at day 7, relative to the control group receiving vehicle only. We conclude that the availability of the Fmoc-Trp(N-tert-prenyl)-OH amino acid facilitates the synthesis of prenylated-tryptophan-containing peptides to explore their therapeutic potential.

Purpose: Previous work has shown that combining dynamic contrast-enhanced (DCE)-MRI and oxygen-enhanced (OE)-MRI binary enhancement maps can identify tumor hypoxia. The current work proposes a novel, data-driven method for mapping tissue oxygenation and perfusion heterogeneity, based on clustering DCE/OE-MRI data. Methods: DCE-MRI and OE-MRI were performed on nine U87 (glioblastoma) and seven Calu6 (non-small cell lung cancer) murine xenograft tumors. Area under the curve and principal component analysis features were calculated and clustered separately using Gaussian mixture modelling. Evaluation metrics were calculated to determine the optimum feature set and cluster number. Outputs were quantitatively compared with a previous non data-driven approach. Results: The optimum method located six robustly identifiable clusters in the data, yielding tumor region maps with spatially contiguous regions in a rim-core structure, suggesting a biological basis. Mean within-cluster enhancement curves showed physiologically distinct, intuitive kinetics of enhancement. Regions of DCE/OE-MRI enhancement mismatch were located, and voxel categorization agreed well with the previous non data-driven approach (Cohen's kappa = 0.61, proportional agreement = 0.75). Conclusion: The proposed method locates similar regions to the previous published method of binarization of DCE/OE-MRI enhancement, but renders a finer segmentation of intra-tumoral oxygenation and perfusion. This could aid in understanding the tumor microenvironment and its heterogeneity. Magn Reson Med 79:2236–2245, 2018.

Anaplastic (ATC) and certain follicular thyroid-carcinomas (FTCs) are radioresistant. The Phosphatidylinositide 3-kinase (PI3K) pathway is commonly hyperactivated in thyroid-carcinomas. PI3K can modify the PI3K-related kinases (PIKKs) in response to radiation: How PIKKs interact with PI3K and contribute to radioresistance in thyroid-carcinomas is unknown. Further uncertainties exist in how these interactions function under the radioresistant hypoxic microenvironment.Under normoxia/anoxia, ATC (8505c) and FTC (FTC-133) cells were irradiated, with PI3K-inhibition (via GDC-0941 and PTEN-reconstitution into PTEN-null FTC-133s) and effects on PIKK-activation, DNA-damage, clonogenic-survival and cell cycle, assessed. FTC-xenografts were treated with 5 × 2 Gy, ± 50 mg/kg GDC-0941 (twice-daily; orally) for 14 days and PIKK-activation and tumour-growth assessed. PIKK-expression was additionally assessed in 12 human papillary thyroid-carcinomas, 13 FTCs and 12 ATCs.GDC-0941 inhibited radiation-induced activation of Ataxia-telangiectasia mutated (ATM), ATM-and Rad3-related (ATR) and DNA-dependent protein kinase catalytic subunit (DNA-PKcs). Inhibition of ATM and DNA-PKcs was PI3K-dependent, since activation was reduced in PTEN-reconstituted FTC-133s. Inhibition of PIKK-activation was greater under anoxia: Consequently, whilst DNA-damage was increased and prolonged under both normoxia and anoxia, PI3K-inhibition only reduced clonogenic-survival under anoxia. GDC-0941 abrogated radiation-induced cell cycle arrest, an effect most likely linked to the marked inhibition of ATR-activation. Importantly, GDC-0941 inhibited radiation-induced PIKK-activation in FTC-xenografts leading to a significant increase in time taken for tumours to triple in size: 26.5 ± 5 days (radiation-alone) versus 31.5 ± 5 days (dual-treatment). PIKKs were highly expressed across human thyroid-carcinoma classifications, with ATM scoring consistently lower. Interestingly, some loss of ATM and DNA-PKcs was observed. These data provide new insight into the mechanisms of hypoxia-associated radioresistance in thyro{id-carcinoma.

Therapeutic inhibition of poly(ADP-ribose) polymerase (PARP), as monotherapy or to supplement the potencies of other agents, is a promising strategy in cancer treatment. We previously reported that the first PARP inhibitor to enter clinical trial, rucaparib (AG014699), induced vasodilation in vivo in xenografts, potentiating response to temozolomide. We now report that rucaparib inhibits the activity of the muscle contraction mediator myosin light chain kinase (MLCK) 10-fold more potently than its commercially available inhibitor ML-9. Moreover, rucaparib produces additive relaxation above the maximal degree achievable with ML-9, suggesting that MLCK inhibition is not solely responsible for dilation. Inhibition of nitric oxide synthesis using L-NMMA also failed to impact rucaparib's activity. Rucaparib contains the nicotinamide pharmacophore, suggesting it may inhibit other NAD+-dependent processes. NAD+ exerts P2 purinergic receptor-dependent inhibition of smooth muscle contraction. Indiscriminate blockade of the P2 purinergic receptors with suramin abrogated rucaparib-induced vasodilation in rat arterial tissue without affecting ML-9-evoked dilation, although the specific receptor subtypes responsible have not been unequivocally identified. Furthermore, dorsal window chamber and real time tumor vessel perfusion analyses in PARP-1-/- mice indicate a potential role for PARP in dilation of tumor-recruited vessels. Finally, rucaparib provoked relaxation in 70% of patient-derived tumor-associated vessels. These data provide tantalising evidence of the complexity of the mechanism underlying rucaparib-mediated vasodilation.

It is known that hypoxia-inducible factor 1 (HIF-1) activity results in the coordinated up-regulation of a large number of proteins that facilitate cell survival in tumours; however, the effect of HIF-1 on cancer metabolism is less well characterised. With knowledge of the specific effect of HIF-1 on cancer metabolism, biomarkers could be identified for which new drugs could be targeted. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) offers the potential to analyse intact cells in situ and has a mass spectral coverage that is applicable to metabolic profiling. It has been used to analyse the effects of HIF-1 on multicellular tumour models. Multicellular tumour spheroids (MTSs) have been cultured from human colon carcinoma cells with and without the expression of HIF-1, and the surface of the cross sections of each MTS has been analysed. Because metabolic profiling is an emerging field in ToF-SIMS, there is a requirement to determine which metabolites can be detected using this technique and which of those can be identified in complex mixtures within biological samples. For this, a selection of metabolites have been analysed, and the ToF-SIMS standard spectra acquired have been used to localise metabolites in MTS sections. The comparison of metabolic profiles of MTSs with and without the expression of HIF-1 has elucidated potential biomarkers for tumour survival in hypoxia, some of which may be HIF-1 regulated. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.

Intratumoural hypoxia (low oxygen tension) is associated with aggressive disease and poor prognosis. Hypoxia-inducible factor-1 is a transcription factor activated by hypoxia that regulates the expression of genes that promote tumour cell survival, progression, metastasis, and resistance to chemo/radiotherapy. In addition to hypoxia, HIF-1 can be activated by growth factor-signalling pathways such as the mitogen-activated protein kinases- (MAPK-) and phosphatidylinositol-3-OH kinases- (PI3K-) signalling cascades. Mutations in these pathways are common in thyroid carcinoma and lead to enhanced HIF-1 expression and activity. Here, we summarise current data that highlights the potential role of both hypoxia and MAPK/PI3K-induced HIF-1 signalling in thyroid carcinoma progression, metastatic characteristics, and the potential role of HIF-1 in thyroid carcinoma response to radiotherapy. Direct or indirect targeting of HIF-1 using an MAPK or PI3K inhibitor in combination with radiotherapy may be a new potential therapeutic target to improve the therapeutic response of thyroid carcinoma to radiotherapy and reduce metastatic burden.

BACKGROUND: Regions within solid tumours often experience oxygen deprivation, which is associated with resistance to chemotherapy and irradiation. The aim of this study was to evaluate the radiosensitising effect of gemcitabine and its main metabolite dFdU under normoxia versus hypoxia and to determine whether hypoxia-inducible factor 1 (HIF-1) is involved in the radiosensitising mechanism. METHODS: Stable expression of dominant negative HIF-1α (dnHIF) in MDA-MB-231 breast cancer cells, that ablated endogenous HIF-1 transcriptional activity, was validated by western blot and functionality was assessed by HIF-1α activity assay. Cells were exposed to varying oxygen environments and treated with gemcitabine or dFdU for 24 h, followed by irradiation. Clonogenicity was then assessed. Using radiosensitising conditions, cells were collected for cell cycle analysis. RESULTS: HIF-1 activity was significantly inhibited in cells stably expressing dnHIF. A clear radiosensitising effect under normoxia and hypoxia was observed for both gemcitabine and dFdU. No significant difference in radiobiological parameters between HIF-1 proficient and HIF-1 deficient MDA-MB-231 cells was demonstrated. CONCLUSIONS: For the first time, radiosensitisation by dFdU, the main metabolite of gemcitabine, was demonstrated under low oxygen conditions. No major role for functional HIF-1 protein in radiosensitisation by gemcitabine or dFdU could be shown.

Imaging biomarkers (IBs) are integral to the routine management of patients with cancer. IBs used daily in oncology include clinical TNM stage, objective response and left ventricular ejection fraction. Other CT, MRI, PET and ultrasonography biomarkers are used extensively in cancer research and drug development. New IBs need to be established either as useful tools for testing research hypotheses in clinical trials and research studies, or as clinical decision-making tools for use in healthcare, by crossing 'translational gaps' through validation and qualification. Important differences exist between IBs and biospecimen-derived biomarkers and, therefore, the development of IBs requires a tailored 'roadmap'. Recognizing this need, Cancer Research UK (CRUK) and the European Organisation for Research and Treatment of Cancer (EORTC) assembled experts to review, debate and summarize the challenges of IB validation and qualification. This consensus group has produced 14 key recommendations for accelerating the clinical translation of IBs, which highlight the role of parallel (rather than sequential) tracks of technical (assay) validation, biological/clinical validation and assessment of cost-effectiveness; the need for IB standardization and accreditation systems; the need to continually revisit IB precision; an alternative framework for biological/clinical validation of IBs; and the essential requirements for multicentre studies to qualify IBs for clinical use.