53BP1-mediated recruitment of RASSF1A to ribosomal DNA breaks promotes local ATM signaling.

DNA lesions occur across the genome and constitute a threat to cell viability; however, damage at specific genomic loci has a relatively greater impact on overall genome stability. The ribosomal RNA gene repeats (rDNA) are emerging fragile sites. Recent progress in understanding how the rDNA damage response is organized has highlighted a key role of adaptor proteins. Here, we show that the scaffold tumor suppressor RASSF1A is recruited to rDNA breaks. RASSF1A recruitment to double-strand breaks is mediated by 53BP1 and depends on RASSF1A phosphorylation at Serine 131 by ATM kinase. Employing targeted rDNA damage, we uncover that RASSF1A recruitment promotes local ATM signaling. RASSF1A silencing, a common epigenetic event during malignant transformation, results in persistent breaks, rDNA copy number alterations and decreased cell viability. Overall, we identify a novel role for RASSF1A at rDNA break sites, provide mechanistic insight into how the DNA damage response is organized in a chromatin context, and provide further evidence for how silencing of the RASSF1A tumor suppressor contributes to genome instability.

TET2 Drives 5hmc Marking of GATA6 and Epigenetically Defines Pancreatic Ductal Adenocarcinoma Transcriptional Subtypes.

BACKGROUND & AIMS: Pancreatic ductal adenocarcinoma (PDAC) is characterized by advanced disease stage at presentation, aggressive disease biology, and resistance to therapy, resulting in an extremely poor 5-year survival rate of <10%. PDAC is classified into transcriptional subtypes with distinct survival characteristics, although how these arise is not known. Epigenetic deregulation, rather than genetics, has been proposed to underpin progression, but exactly why is unclear and is hindered by the technical limitations of analyzing clinical samples. METHODS: We performed genome-wide epigenetic mapping of DNA modifications 5-methylcytosine and 5-hydroxymethylcytosine (5hmc) using oxidative bisulfite sequencing from formalin-embedded sections. We identified overlap with transcriptional signatures in formalin-fixed, paraffin-embedded tissue from resected patients, via bioinformatics using iCluster and mutational profiling and confirmed them in vivo. RESULTS: We found that aggressive squamous-like PDAC subtypes result from epigenetic inactivation of loci, including GATA6, which promote differentiated classical pancreatic subtypes. We showed that squamous-like PDAC transcriptional subtypes are associated with greater loss of 5hmc due to reduced expression of the 5-methylcytosine hydroxylase TET2. Furthermore, we found that SMAD4 directly supports TET2 levels in classical pancreatic tumors, and loss of SMAD4 expression was associated with reduced 5hmc, GATA6, and squamous-like tumors. Importantly, enhancing TET2 stability using metformin and vitamin C/ascorbic acid restores 5hmc and GATA6 levels, reverting squamous-like tumor phenotypes and WNT-dependence in vitro and in vivo. CONCLUSIONS: We identified epigenetic deregulation of pancreatic differentiation as an underpinning event behind the emergence of transcriptomic subtypes in PDAC. Our data showed that restoring epigenetic control increases biomarkers of classical pancreatic tumors that are associated with improved therapeutic responses and survival.

Circulating biomarkers and outcomes from a randomised phase 2 trial of gemcitabine versus capecitabine-based chemoradiotherapy for pancreatic cancer.

BACKGROUND: The Phase 2 SCALOP trial compared gemcitabine with capecitabine-based consolidation chemoradiotherapy (CRT) in locally advanced pancreatic cancer (LAPC). METHODS: Thirty-five systematically identified circulating biomarkers were analysed in plasma samples from 60 patients enroled in SCALOP. Each was measured in triplicate at baseline (prior to three cycles of gemcitabine-capecitabine induction chemotherapy) and, for a subset, prior to CRT. Association with overall survival (OS) was determined using univariable Cox regression and optimal thresholds delineating low to high values identified using time-dependent ROC curves. Independence from known prognostic factors was assessed using Spearman correlation and the Wilcoxon rank sum test prior to multivariable Cox regression modelling including independent biomarkers and known prognostic factors. RESULTS: Baseline circulating levels of C-C motif chemokine ligand 5 (CCL5) were significantly associated with OS, independent of other clinicopathological characteristics. Patients with low circulating CCL5 (CCL5low) had a median OS of 18.5 (95% CI 11.76-21.32) months compared to 11.3 (95% CI 9.86-15.51) months in CCL5high; hazard ratio 1.95 (95% CI 1.04-8.65; p = 0.037). CONCLUSIONS: CCL5 is an independent prognostic biomarker in LAPC. Given the known role of CCL5 in tumour invasion, metastasis and the induction of an immunosuppressive micro-environment, targeting of CCL5-mediated pathways may offer therapeutic potential in pancreatic cancer. CLINICAL TRIAL REGISTRATION: The SCALOP trial was registered with ISRCTN, number 96169987 (registered 29 May 2008).

Dual-specificity protein phosphatase DUSP4 regulates response to MEK inhibition in BRAF wild-type melanoma.

BACKGROUND: Aiming to improve treatment options for BRAF wild-type melanoma, we previously conducted the DOC-MEK study of docetaxel with MEK inhibitor (MEKi) selumetinib or placebo, revealing trends to prolongation of progression-free survival (hazard ratio 0.75, P = 0.130), and improved response rates (32% vs 14%, P = 0.059) with docetaxel plus selumetinib. NRAS status did not associate with outcome. Here, the aim was to identify novel biomarkers of response to MEKi. METHODS: A MEK 6 gene signature was quantified using NanoString and correlated with clinical outcomes. Two components of the gene signature were investigated by gene silencing in BRAF/NRAS wild-type melanoma cells. RESULTS: In melanomas of patients on the selumetinib but not the placebo arm, two gene signature components, dual-specificity protein phosphatase 4 (DUSP4) and ETS translocation variant 4 (ETV4), were expressed more highly in responders than non-responders. In vitro, ETV4 depletion inhibited cell survival but did not influence sensitivity to MEKi selumetinib or trametinib. In contrast, DUSP4-depleted cells showed enhanced cell survival and increased resistance to both selumetinib and trametinib. CONCLUSIONS: ETV4 and DUSP4 associated with clinical response to docetaxel plus selumetinib. DUSP4 depletion induced MEKi resistance, suggesting that DUSP4 is not only a biomarker but also a mediator of MEKi sensitivity. CLINICAL TRIAL REGISTRATION: DOC-MEK (EudraCT no: 2009-018153-23).

Aruncin B: Synthetic Studies, Structural Reassignment and Biological Evaluation.

A ring-closing alkene metathesis (RCM)/ oxyselenation-selenoxide elimination sequence was established to the sodium salts E- and Z-25 of the originally proposed structure for the recently isolated cytotoxin aruncin B (1), as well as to the sodium salt Z-34 of a related ethyl ether regioisomer; however, none of their corresponding free acids could be obtained. Their acid sensitivity, together with detailed analysis of the spectroscopic data indicated that profound structural revision was necessary. This led to reassignment of aruncin B as a Z-γ-alkylidenebutenolide Z-36. Although a related RCM/ oxyselenation-selenoxide elimination sequence was used to confirm the γ-alkylidenebutenolide motif, a ß-iodo Morita-Baylis-Hillman reaction/ Sonogashira cross-coupling-5-exo-dig lactonisation sequence was subsequently developed, due to its brevity and flexibility for diversification. Aruncin B (36), together with 14 γ-alkylidenebutenolide analogues, were generated for biological evaluation.

Synthesis and bioactivity of fused- and spiro-ß-lactone-lactam systems.

An investigation of the formation of fused- and spiro-ß-lactone annulate to γ-lactams has shown that the fused systems are formed preferentially, under standard conditions, but that spiro systems are accessible only when the formation of the fused system is blocked and require careful optimisation of reaction conditions. These systems display both weak antibacterial activity and proteasome inhibition.

Development of human pancreatic cancer avatars as a model for dynamic immune landscape profiling and personalized therapy.

Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer, a disease with dismal overall survival. Advances in treatment are hindered by a lack of preclinical models. Here, we show how a personalized organotypic "avatar" created from resected tissue allows spatial and temporal reporting on a complete in situ tumor microenvironment and mirrors clinical responses. Our perfusion culture method extends tumor slice viability, maintaining stable tumor content, metabolism, stromal composition, and immune cell populations for 12 days. Using multiplexed immunofluorescence and spatial transcriptomics, we identify immune neighborhoods and potential for immunotherapy. We used avatars to assess the impact of a preclinically validated metabolic therapy and show recovery of stromal and immune phenotypes and tumor redifferentiation. To determine clinical relevance, we monitored avatar response to gemcitabine treatment and identify a patient avatar-predictable response from clinical follow-up. Thus, avatars provide valuable information for syngeneic testing of therapeutics and a truly personalized therapeutic assessment platform for patients.

Novel automated tracking analysis of particles subjected to shear flow: kindlin-3 role in B cells.

Shear flow assays are used to mimic the influence of physiological shear force in diverse situations such as leukocyte rolling and arrest on the vasculature, capture of nanoparticles, and bacterial adhesion. Analysis of such assays usually involves manual counting, is labor-intensive, and is subject to bias. We have developed the Leukotrack program that incorporates a novel (to our knowledge) segmentation routine capable of reliable detection of cells in phase contrast images. The program also automatically tracks rolling cells in addition to those that are more firmly attached and migrating in random directions. We demonstrate its use in the analysis of lymphocyte arrest mediated by one or more active conformations of the integrin LFA-1. Activation of LFA-1 is a multistep process that depends on several proteins including kindlin-3, the protein that is mutated in leukocyte adhesion deficiency-III patients. We find that the very first stage of LFA-1-mediated attaching is unable to proceed in the absence of kindlin-3. Our evidence indicates that kindlin-3-mediated high-affinity LFA-1 controls both the early transient integrin-dependent adhesions in addition to the final stable adhesions made under flow conditions.

Predicting Early Disease Recurrence of Pancreatic Cancer following Surgery: Determining the Role of NUDT15 as a Prognostic Biomarker.

Surgical resection remains the only curative treatment strategy for Pancreatic Ductal Adenocarcinoma (PDAC). A proportion of patients succumb to early disease recurrence post-operatively despite receiving adjuvant chemotherapy. The ability to identify these high-risk individuals at their initial diagnosis, prior to surgery, could potentially alter their treatment algorithm. This unique patient cohort may benefit from neo-adjuvant chemotherapy, even in the context of resectable disease, as this may secure systemic control over their disease burden. It may also improve patient selection for surgery. Using the Cancer Genome Atlas dataset, we first confirmed the poor overall survival associated with early disease recurrence (p < 0.0001). The transcriptomic profiles of these tumours were analysed, and we identified key aberrant signalling pathways involved in early disease relapse; downregulation across several immune signalling pathways was noted. Differentially expressed genes that could serve as biomarkers were identified (BPI, C6orf58, CD177, MCM7 and NUDT15). Receiver operating characteristic curves were constructed in order to identify biomarkers with a high diagnostic ability to identify patients who developed early disease recurrence. NUDT15 expression had the highest discriminatory capability as a biomarker (AUC 80.8%). Its expression was confirmed and validated in an independent cohort of patients with resected PDAC (n = 13). Patients who developed an early recurrence had a statistically higher tumour expression of NUDT15 when compared to patients who did not recur early (p < 0.01). Our results suggest that NUDT15 can be used as a prognostic biomarker that can stratify patients according to their risk of developing early disease recurrence.

RAPTOR up-regulation contributes to resistance of renal cancer cells to PI3K-mTOR inhibition.

The outlook for patients with advanced renal cell cancer (RCC) has been improved by targeted agents including inhibitors of the PI3 kinase (PI3K)-AKT-mTOR axis, although treatment resistance is a major problem. Here, we aimed to understand how RCC cells acquire resistance to PI3K-mTOR inhibition. We used the RCC4 cell line to generate a model of in vitro resistance by continuous culture in PI3K-mTOR kinase inhibitor NVP-BEZ235 (BEZ235, Dactolisib). Resistant cells were cross-resistant to mTOR inhibitor AZD2014. Sensitivity was regained after 4 months drug withdrawal, and resistance was partially suppressed by HDAC inhibition, supporting an epigenetic mechanism. BEZ235-resistant cells up-regulated and/or activated numerous proteins including MET, ABL, Notch, IGF-1R, INSR and MEK/ERK. However, resistance was not reversed by inhibiting or depleting these pathways, suggesting that many induced changes were passengers not drivers of resistance. BEZ235 blocked phosphorylation of mTOR targets S6 and 4E-BP1 in parental cells, but 4E-BP1 remained phosphorylated in resistant cells, suggesting BEZ235-refractory mTORC1 activity. Consistent with this, resistant cells over-expressed mTORC1 component RAPTOR at the mRNA and protein level. Furthermore, BEZ235 resistance was suppressed by RAPTOR depletion, or allosteric mTORC1 inhibitor rapamycin. These data reveal that RAPTOR up-regulation contributes to PI3K-mTOR inhibitor resistance, and suggest that RAPTOR expression should be included in the pharmacodynamic assessment of mTOR kinase inhibitor trials.

Perfused Three-dimensional Organotypic Culture of Human Cancer Cells for Therapeutic Evaluation.

Pharmaceutical research requires pre-clinical testing of new therapeutics using both in-vitro and in-vivo models. However, the species specificity of non-human in-vivo models and the inadequate recapitulation of physiological conditions in-vitro are intrinsic weaknesses. Here we show that perfusion is a vital factor for engineered human tissues to recapitulate key aspects of the tumour microenvironment. Organotypic culture and human tumour explants were allowed to grow long-term (14-35 days) and phenotypic features of perfused microtumours compared with those in the static culture. Differentiation status and therapeutic responses were significantly different under perfusion, indicating a distinct biological response of cultures grown under static conditions. Furthermore, heterogeneous co-culture of tumour and endothelial cells demonstrated selective cell-killing under therapeutic perfusion versus episodic delivery. We present a perfused 3D microtumour culture platform that sustains a more physiological tissue state and increased viability for long-term analyses. This system has the potential to tackle the disadvantages inherit of conventional pharmaceutical models and is suitable for precision medicine screening of tumour explants, particularly in hard-to-treat cancer types such as brain cancer which suffer from a lack of clinical samples.

The Gαq/11 proteins contribute to T lymphocyte migration by promoting turnover of integrin LFA-1 through recycling.

The role of Gαi proteins coupled to chemokine receptors in directed migration of immune cells is well understood. In this study we show that the separate class of Gαq/11 proteins is required for the underlying ability of T cells to migrate both randomly and in a directed chemokine-dependent manner. Interfering with Gαq or Gα11 using dominant negative cDNA constructs or siRNA for Gαq causes accumulation of LFA-1 adhesions and stalled migration. Gαq/11 has an impact on LFA-1 expression at plasma membrane level and also on its internalization. Additionally Gαq co-localizes with LFA-1- and EEA1-expressing intracellular vesicles and partially with Rap1- but not Rab11-expressing vesicles. However the influence of Gαq is not confined to the vesicles that express it, as its reduction alters intracellular trafficking of other vesicles involved in recycling. In summary vesicle-associated Gαq/11 is required for the turnover of LFA-1 adhesion that is necessary for migration. These G proteins participate directly in the initial phase of recycling and this has an impact on later stages of the endo-exocytic pathway.

The insider's guide to leukocyte integrin signalling and function.

The activation of leukocyte integrins through diverse receptors results in transformation of the integrin from a bent, resting form to an extended conformation, which has at least two states of ligand-binding activity. This highly regulated activation process is essential for T cell migration and the formation of an immunological synapse. The signalling events that drive integrin activation are complex. Some key players have been well-characterized, but other aspects of the signalling mechanisms involved are still unclear. This Review focuses on the integrin lymphocyte function-associated antigen 1 (LFA1; also known as αLß2 integrin), which is expressed by T cells, and explores how disparate signalling pathways synergize to regulate LFA1 activity.

Kinetic analysis of the inhibition of matrix metalloproteinases: lessons from the study of tissue inhibitors of metalloproteinases.

Tissue inhibitors of metalloproteinases (TIMPs) are a group of highly potent inhibitors of matrix metalloproteinases (MMPs) and disintegrin metalloproteinases (ADAMs). The high affinity and "tight-binding" nature of the inhibition of MMPs or ADAMs by TIMPs presents challenges for the determination of both equilibrium and dissociation rate constants of these inhibitory events. Methodologies that enable some of these challenges to be overcome are described in this chapter and represent valuable lessons for the in vitro assessment of MMP or ADAM inhibitors within a drug discovery context.