hSSB1 phosphorylation is dynamically regulated by DNA-PK and PPP-family protein phosphatases

This work was supported by a National Health and Medical Research Council project grant [1066550], an Australian Research Council project grant [DP 120103099] and by a Queensland Health Senior Clinical Research Fellowship awarded to K.J.O. This work was also supported by the Wellcome Trust [094476/Z/10/Z], which funded the purchase of the TripleTOF 5600 mass spectrometer at the BSRC Mass Spectrometry and Proteomics Facility, University of St Andrews. NWA was supported by a scholarship awarded by Cancer Council Queensland. E.B. is supported by an Advance Queensland Research Fellowship.The maintenance of genomic stability is essential for cellular viability and the prevention of diseases such as cancer. Human single-stranded DNA-binding protein 1 (hSSB1) is a protein with roles in the stabilisation and restart of stalled DNA replication forks, as well as in the repair of oxidative DNA lesions and double-strand DNA breaks. In the latter process, phosphorylation of threonine 117 by the ATM kinase is required for hSSB1 stability and efficient DNA repair. The regulation of hSSB1 in other DNA repair pathways has however remained unclear. Here we report that hSSB1 is also directly phosphorylated by DNA-PK at serine residue 134. While this modification is largely suppressed in undamaged cells by PPP-family protein phosphatases, S134 phosphorylation is enhanced following the disruption of replication forks and promotes cellular survival. Together, these data thereby represent a novel mechanism for hSSB1 regulation following the inhibition of replication.Publisher PDFPeer reviewe

COMMD4 functions with the histone H2A-H2B dimer for the timely repair of DNA double-strand breaks

Genomic stability is critical for normal cellular function and its deregulation is a universal hallmark of cancer. Here we outline a previously undescribed role of COMMD4 in maintaining genomic stability, by regulation of chromatin remodelling at sites of DNA double-strand breaks. At break-sites, COMMD4 binds to and protects histone H2B from monoubiquitination by RNF20/RNF40. DNA damage-induced phosphorylation of the H2A-H2B heterodimer disrupts the dimer allowing COMMD4 to preferentially bind H2A. Displacement of COMMD4 from H2B allows RNF20/40 to monoubiquitinate H2B and for remodelling of the break-site. Consistent with this critical function, COMMD4-deficient cells show excessive elongation of remodelled chromatin and failure of both non-homologous-end-joining and homologous recombination. We present peptide-mapping and mutagenesis data for the potential molecular mechanisms governing COMMD4-mediated chromatin regulation at DNA double-strand breaks.</p

Does EGFR Mutation Type Influence Patient-Reported Outcomes in Patients with Advanced EGFR Mutation-Positive Non-Small-Cell Lung Cancer? Analysis of Two Large, Phase III Studies Comparing Afatinib with Chemotherapy (LUX-Lung 3 and LUX-Lung 6)

Introduction: In LUX-Lung 3 and LUX-Lung 6, afatinib significantly improved progression-free survival (PFS) versus chemotherapy in patients with tumors harboring common epidermal growth factor receptor (EGFR) mutations (Del19/L858R) and significantly improved overall survival (OS) in patients with tumors harboring Del19 mutations. Patient-reported outcomes stratified by EGFR mutation type are reported. Patients and Methods Lung cancer symptoms and health-related quality of life (QoL) were assessed every 21 days until progression using the EORTC Quality of Life Core Questionnaire C30 and its lung cancer-specific module, LC13. Analyses of cough, dyspnea, and pain were prespecified and included analysis of percentage of patients who improved on therapy, time to deterioration of symptoms, and change over time. Global health status (GHS)/QoL was also assessed. Analyses were conducted for all patients with tumors harboring Del19 or L858R mutations and were exploratory. Results: Compared with chemotherapy, afatinib more commonly improved symptoms of, delayed time to deterioration for, and was associated with better mean scores over time for cough and dyspnea in patients with Del19 or L858R mutations. All three prespecified analyses of pain showed a trend favoring afatinib over chemotherapy. In both Del19 and L858R mutations, afatinib was also associated with improvements in GHS/QoL. Longitudinal analyses demonstrated statistically significant improvements in GHS/QoL for afatinib over chemotherapy for patients with tumors harboring Del19 mutations or L858R mutations. Conclusions: These exploratory analyses suggest first-line afatinib improved lung cancer-related symptoms and GHS/QoL compared with chemotherapy in patients with non-small-cell lung cancer with tumors harboring common EGFR mutations, with benefits in both Del19 and L858R patients. When considered with OS (Del19 patients only) and PFS benefits, these findings substantiate the value of using afatinib over chemotherapy in these patient groups. Electronic supplementary material The online version of this article (10.1007/s40271-017-0287-z) contains supplementary material, which is available to authorized users

Combination Therapy With Histone Deacetylase Inhibitors (HDACi) for the Treatment of Cancer: Achieving the Full Therapeutic Potential of HDACi

Genetic and epigenetic changes in DNA are involved in cancer development and tumor progression. Histone deacetylases (HDACs) are key regulators of gene expression that act as transcriptional repressors by removing acetyl groups from histones. HDACs are dysregulated in many cancers, making them a therapeutic target for the treatment of cancer. Histone deacetylase inhibitors (HDACi), a novel class of small-molecular therapeutics, are now approved by the Food and Drug Administration as anticancer agents. While they have shown great promise, resistance to HDACi is often observed and furthermore, HDACi have shown limited success in treating solid tumors. The combination of HDACi with standard chemotherapeutic drugs has demonstrated promising anticancer effects in both preclinical and clinical studies. In this review, we summarize the research thus far on HDACi in combination therapy, with other anticancer agents and their translation into preclinical and clinical studies. We additionally highlight the side effects associated with HDACi in cancer therapy and discuss potential biomarkers to either select or predict a patient’s response to these agents, in order to limit the off-target toxicity associated with HDACi

A rare case of omentum invasive prostate cancer: Staging with PSMA PET/CT imaging and response to systemic therapy

The omentum is a rare metastatic site for prostatic adenocarcinoma. We present a case of metastatic castrate-resistant prostate cancer, with progressive omentum invasive prostate cancer identified on prostate-specific membrane antigen (PSMA) PET/CT scan. Omental biopsy revealed metastatic prostate adenocarcinoma, and cabazitaxel chemotherapy was instituted with a prostate-specific antigen biochemical response. Repeat PSMA PET/CT imaging revealed increased avidity in omental metastasis. Despite prostate-specific antigen response, PSMA PET/CT did not correlate with a therapeutic response

Combination Therapy With Histone Deacetylase Inhibitors (HDACi) for the Treatment of Cancer: Achieving the Full Therapeutic Potential of HDACi

Genetic and epigenetic changes in DNA are involved in cancer development and tumor progression. Histone deacetylases (HDACs) are key regulators of gene expression that act as transcriptional repressors by removing acetyl groups from histones. HDACs are dysregulated in many cancers, making them a therapeutic target for the treatment of cancer. Histone deacetylase inhibitors (HDACi), a novel class of small-molecular therapeutics, are now approved by the Food and Drug Administration as anticancer agents. While they have shown great promise, resistance to HDACi is often observed and furthermore, HDACi have shown limited success in treating solid tumors. The combination of HDACi with standard chemotherapeutic drugs has demonstrated promising anticancer effects in both preclinical and clinical studies. In this review, we summarize the research thus far on HDACi in combination therapy, with other anticancer agents and their translation into preclinical and clinical studies. We additionally highlight the side effects associated with HDACi in cancer therapy and discuss potential biomarkers to either select or predict a patient’s response to these agents, in order to limit the off-target toxicity associated with HDACi

Tumor Hypoxia Drives Genomic Instability

Cancer is a leading cause of death worldwide. As a common characteristic of cancer, hypoxia is associated with poor prognosis due to enhanced tumor malignancy and therapeutic resistance. The enhanced tumor aggressiveness stems at least partially from hypoxia-induced genomic instability. Therefore, a clear understanding of how tumor hypoxia induces genomic instability is crucial for the improvement of cancer therapeutics. This review summarizes recent developments highlighting the association of tumor hypoxia with genomic instability and the mechanisms by which tumor hypoxia drives genomic instability, followed by how hypoxic tumors can be specifically targeted to maximize efficacy.</p

Beyond PARP1: The Potential of Other Members of the Poly (ADP-Ribose) Polymerase Family in DNA Repair and Cancer Therapeutics

The proteins within the Poly-ADP Ribose Polymerase (PARP) family encompass a diverse and integral set of cellular functions. PARP1 and PARP2 have been extensively studied for their roles in DNA repair and as targets for cancer therapeutics. Several PARP inhibitors (PARPi) have been approved for clinical use, however, while their efficacy is promising, tumours readily develop PARPi resistance. Many other members of the PARP protein family share catalytic domain homology with PARP1/2, however, these proteins are comparatively understudied, particularly in the context of DNA damage repair and tumourigenesis. This review explores the functions of PARP4,6-16 and discusses the current knowledge of the potential roles these proteins may play in DNA damage repair and as targets for cancer therapeutics.</p

P2.01-081 CDCA3 is a novel prognostic cell cycle protein and target for therapy in non-small cell lung cancer

Background: Lung cancer is the leading cause of cancerrelated mortality worldwide with a 5 year survival rate of 15%. Non-small cell lung cancer (NSCLC) is the most commonly diagnosed form of lung cancer. Cisplatin-based regimens are currently the most effective chemotherapy for NSCLC, however, chemoresistance poses a major therapeutic problem. New and reliable strategies are required to avoid drug resistance in NSCLC. Cell division cycle associated 3 (CDCA3) is a key regulator of the cell cycle. CDCA3 modulates this process by enabling cell entry into mitosis through degradation of the mitosis-inhibitory factor WEE1. CDCA3 itself is also degraded in G1 yet reexpressed in G2/M phase, to allow successful progression through the cell cycle. Herein, we describe CDCA3 as a novel prognostic factor in NSCLC and target to delay or prevent cisplatin resistance in NSCLC. Methods: CDCA3 expression was investigated in squamous and non-squamous NSCLC using several approaches including bioinformatic analysis of publicly available datasets, immunohistochemistry of a tissue microarray and western blot analysis of matched tumor and normal tissue and NSCLC cell lines. CDCA3 function in NSCLC was determined using several in vitro assays by siRNA depleting CDCA3 in a panel of three immortalized bronchial epithelial cell lines (HBEC) and seven NSCLC cell lines. Results: CDCA3 transcripts and protein levels are elevated in NSCLC patient tissue and highly expressed in tumor cells relative to proximal normal cells. High mRNA levels are associated with poor survival in resected NSCLC. Depletion of CDCA3 in vitro markedly impairs proliferation in seven NSCLC cell lines by inducing a mitotic cell cycle arrest, ultimately resulting in p21- dependent cellular senescence. Importantly, silencing of CDCA3 also greatly sensitizes NSCLC cell lines to cisplatin. In line with these in vitro data, NSCLC patients that have elevated levels of CDCA3 and are treated with cisplatin have a poorer outcome than patients with reduced levels of the protein. To improve patient response to cisplatin, we are exploring novel strategies to suppress CDCA3 expression in tumor cells. Conclusion: Our data highlight CDCA3 as a novel factor in mediating NSCLC. We propose that evaluating novel strategies to target CDCA3 may prove a useful strategy is enhancing the anti-tumor activity of platinum-based chemotherapy and may ultimately benefit patient outcomes by preventing cisplatin resistance