WRN helicase is a synthetic lethal target in microsatellite unstable cancers.

Synthetic lethality-an interaction between two genetic events through which the co-occurrence of these two genetic events leads to cell death, but each event alone does not-can be exploited for cancer therapeutics1. DNA repair processes represent attractive synthetic lethal targets, because many cancers exhibit an impairment of a DNA repair pathway, which can lead to dependence on specific repair proteins2. The success of poly(ADP-ribose) polymerase 1 (PARP-1) inhibitors in cancers with deficiencies in homologous recombination highlights the potential of this approach3. Hypothesizing that other DNA repair defects would give rise to synthetic lethal relationships, we queried dependencies in cancers with microsatellite instability (MSI), which results from deficient DNA mismatch repair. Here we analysed data from large-scale silencing screens using CRISPR-Cas9-mediated knockout and RNA interference, and found that the RecQ DNA helicase WRN was selectively essential in MSI models in vitro and in vivo, yet dispensable in models of cancers that are microsatellite stable. Depletion of WRN induced double-stranded DNA breaks and promoted apoptosis and cell cycle arrest selectively in MSI models. MSI cancer models required the helicase activity of WRN, but not its exonuclease activity. These findings show that WRN is a synthetic lethal vulnerability and promising drug target for MSI cancers.

Transbronchial Lung Cryobiopsy Performed with Cone Beam Computed Tomography Guidance Versus Fluoroscopy: A Retrospective Cohort Review.

PURPOSE: Determining the cause of interstitial lung disease (ILD) remains challenging. While surgical lung biopsy remains the gold standard approach, risks associated with it may be prohibitive. Transbronchial lung cryobiopsy (TBLC) is a minimally invasive alternative with an improved safety profile and acceptable diagnostic accuracy. We retrospectively assessed whether the use of Cone Beam computed tomography guidance for TBLC (TBLC-CBCT) improves safety and diagnostic yield compared to performing TBLC with fluoroscopic guidance (TBLC-F). METHODS: A retrospective cohort review of 120 patients presenting for evaluation of newly diagnosed ILD was performed. Demographic data, pulmonary function test values, chest imaging pattern, procedural information, and final multidisciplinary discussion (MDD) diagnosis were recorded. RESULTS: 62 patients underwent TBLC-F and 58 underwent TBLC-CBCT. Patients undergoing TBLC-CBCT were older (67.86 ± 10.97 vs 61.45 ± 12.77 years, p = 0.004) and had a higher forced vital capacity percent predicted (73.80 ± 17.32% vs 66.00 ± 17.45%, p = 0.03) compared to the TBLC-F group. The average probe-to-pleura distance was 5.1 ± 2.3 mm in the TBLC-CBCT group with 4.0 ± 0.3 CBCT spins performed. Pneumothorax occurred more often in the TBLC-F group (n = 6, 9.7%) compared to the TBLC-CBCT group (n = 1, 1.7%, p = 0.06). Grade 2 bleeding only occurred in the TBLC-F group (n = 4, 6.5%). A final MDD diagnosis was obtained in 89% (n = 57) of TBLC-F patients and 95% (n = 57) of TBLC-CBCT patients. CONCLUSIONS: TBLC-CBCT appears to be safer compared to TBLC-F with both approaches facilitating an MDD diagnosis. Further studies from multiple institutions randomizing patients to each modality are needed to confirm these findings.

Immunomodulatory Roles of PARP-1 and PARP-2: Impact on PARP-Centered Cancer Therapies.

Poly(ADP-ribose) polymerase-1 (PARP-1) and PARP-2 are enzymes which post-translationally modify proteins through poly(ADP-ribosyl)ation (PARylation)-the transfer of ADP-ribose chains onto amino acid residues-with a resultant modulation of protein function. Many targets of PARP-1/2-dependent PARylation are involved in the DNA damage response and hence, the loss of these proteins disrupts a wide range of biological processes, from DNA repair and epigenetics to telomere and centromere regulation. The central role of these PARPs in DNA metabolism in cancer cells has led to the development of PARP inhibitors as new cancer therapeutics, both as adjuvant treatment potentiating chemo-, radio-, and immuno-therapies and as monotherapy exploiting cancer-specific defects in DNA repair. However, a cancer is not just made up of cancer cells and the tumor microenvironment also includes multiple other cell types, particularly stromal and immune cells. Interactions between these cells-cancerous and non-cancerous-are known to either favor or limit tumorigenesis. In recent years, an important role of PARP-1 and PARP-2 has been demonstrated in different aspects of the immune response, modulating both the innate and adaptive immune system. It is now emerging that PARP-1 and PARP-2 may not only impact cancer cell biology, but also modulate the anti-tumor immune response. Understanding the immunomodulatory roles of PARP-1 and PARP-2 may provide invaluable clues to the rational development of more selective PARP-centered therapies which target both the cancer and its microenvironment.

Carbon dioxide laser versus cold-steel supraglottoplasty: A comparison of post-operative outcomes.

OBJECTIVE: Supraglottoplasty is the mainstay of surgical treatment for laryngomalacia, and is commonly performed via two methods: cold steel or carbon dioxide (CO2) laser. The degree of post-operative monitoring following supraglottoplasty varies, both within and between institutions. The aim of this study was to compare the post-operative monitoring and interventions required by patients undergoing cold-steel versus CO2 laser supraglottoplasty. DESIGN: Retrospective cohort of pediatric patients (age < 18 years) undergoing supraglottoplasty at a tertiary care pediatric hospital. The primary exposure was the surgical instrument(s) used during supraglottoplasty. The primary outcome was prolonged intensive care unit (ICU)-stay (defined as >24 h). RESULTS: 155 cases were eligible for inclusion. Fifty-eight (37.4%) patients had a comorbid condition. Common indications for surgery included feeding difficulty (56.1%), severe respiratory distress (33.5%), and obstructive sleep apnea (25.2%). CO2 laser was employed in 49 cases and cold-steel in 106 cases. Prolonged ICU-stay (>24 h) was observed in 14 CO2 laser cases (28.6%) and 11 cold-steel cases (10.4%) (adjusted OR 3.42; 95% CI 1.43, 8.33). CO2 laser cases were more likely to require post-operative intubation, non-invasive positive pressure ventilation, and nebulized racemic epinephrine. Concomitant neurological condition was associated with an increased risk of prolonged ICU-stay, while extent of surgery and age were not. CONCLUSIONS: CO2 laser supraglottoplasty is associated with an increased risk of prolonged ICU-stay and need for ICU-level airway intervention, compared to the cold-steel technique. While this association should not be misconstrued as a causal relationship, the current study demonstrates that specific surgical factors may influence the patient monitoring requirements following supraglottoplasty, particularly the choice of instrument and the extent of surgery.

Coordinated signals from PARP-1 and PARP-2 are required to establish a proper T cell immune response to breast tumors in mice.

Poly(ADP-ribose)-polymerase (PARP)-1 and PARP-2 play an essential role in the DNA damage response. Based on this effect of PARP in the tumor cell itself, PARP inhibitors have emerged as new therapeutic tools both approved and in clinical trials. However, the interactome of multiple other cell types, particularly T cells, within the tumor microenvironment are known to either favor or limit tumorigenesis. Here, we bypassed the embryonic lethality of dually PARP-1/PARP-2-deficient mice by using a PARP-1-deficient mouse with a Cd4-promoter-driven deletion of PARP-2 in T cells to investigate the understudied role of these PARPs in the modulation of T cell responses against AT-3-induced breast tumors. We found that dual PARP-1/PARP-2-deficiency in T cells promotes tumor growth while single deficiency of each protein limited tumor progression. Analysis of tumor-infiltrating cells in dual PARP-1/PARP-2-deficiency host-mice revealed a global change in immunological profile and impaired recruitment and activation of T cells. Conversely, single PARP-1 and PARP-2-deficiency tends to produce an environment with an active and partially upregulated immune response. Our findings pinpoint opposite effects of single and dual PARP-1 and PARP-2-deficiency in modulating the antitumor response with an impact on tumor progression, and will have implications for the development of more selective PARP-centered therapies.

Evaluation of the sensitivity of R1ρ MRI to pH and macromolecular density.

The tumor microenvironment is characteristically acidic and this extracellular acidosis is known to play a role in carcinogenesis and metastasis and can affect tumor chemosensitivity and radiosensitivity. Intracellular pH has been used as a possible biomarker of salvageable tissue in ischemic stroke. A non-invasive MRI-based approach for the determination and imaging of cerebral pH would be a powerful tool in cancer diagnosis and monitoring, as well as stroke treatment planning. Several pH-based MRI imaging approaches have been proposed but for these to be useful, disentangling the effects of pH from other parameters which may affect the measured MRI signal is crucial to ensure accuracy and specificity. R1 relaxation in the rotating frame (R1ρ) is an example of a method that has been proposed to probe pH in vivo using MRI. In this study, we have investigated the relationship between R1ρ, pH, and macromolecular density in vitro using phantoms and in human volunteers. Here we show that the rate of R1ρ relaxation (=1/T1ρ) varies with pH but only in the presence of macromolecules. At constant pH, phantom macromolecular density inversely correlated with R1ρ. R1ρ imaging of the normal human brain demonstrated regional heterogeneity with significant differences between structurally distinct regions, which are likely to be independent of pH. For example, R1ρ was higher in the basal ganglia compared to grey matter and higher in grey matter compared to white matter. We conclude that R1ρ cannot be reliably used to image tissue pH without deconvolution from the effects of local tissue macromolecular composition.

Early surgical intervention for fulminant pseudomembranous colitis.

The objective of this study of a retrospective case series was to determine factors associated with survival after surgical intervention in pseudomembranous colitis (PMC). The study was conducted at a tertiary care medical center and comprised 36 patients who underwent colectomy for fulminant PMC from 1995 to 2006. Patients including 21 females ranged from 40 to 89 years of age (mean, 70 years). Comorbidities included diabetes (39%), cardiovascular disease (77%), chronic obstructive pulmonary disease (47%), and intake of immunosuppressive medications (45%). Seventy-two per cent received antibiotics in the previous 2 months. Only patients with a confirmation of PMC on pathology specimens were included in the study. All patients underwent colectomy. Patients were stratified into two groups: survivors and nonsurvivors. Various clinical factors/ parameters used in the management of patients with PMC were studied in these two groups. Survival was correlated with mean white blood cell count (23,000 survivors versus 40,000 nonsurvivors, P < 0.01); multisystem organ failure (16 per cent survivors versus 47 per cent nonsurvivors, P < 0.05); and preoperative pressors (16 per cent survivors versus 47 per cent nonsurvivors, P < 0.05). Overall mortality for the study period was 47 per cent. Mortality rate analysis revealed a lower rate for the more recent years (32 per cent for 2000 to 2006 versus 65 per cent for 1995 to 1999, P < 0.05). In the more recent years, the time elapsing before colectomy was also lower (1.4 days versus 2.5 days, nonsignificant), and patients had less preoperative hemodynamic instability (70 per cent versus 31 per cent, P < 0.03). In one institution, survival after surgery for PMC was found to be associated with a mean white blood cell count (< 37,000), nondependence on preoperative vasopressors, and surgical intervention before the onset of hemodynamic instability.

Physiological Roles of DNA Double-Strand Breaks.

Genomic integrity is constantly threatened by sources of DNA damage, internal and external alike. Among the most cytotoxic lesions is the DNA double-strand break (DSB) which arises from the cleavage of both strands of the double helix. Cells boast a considerable set of defences to both prevent and repair these breaks and drugs which derail these processes represent an important category of anticancer therapeutics. And yet, bizarrely, cells deploy this very machinery for the intentional and calculated disruption of genomic integrity, harnessing potentially destructive DSBs in delicate genetic transactions. Under tight spatiotemporal regulation, DSBs serve as a tool for genetic modification, widely used across cellular biology to generate diverse functionalities, ranging from the fundamental upkeep of DNA replication, transcription, and the chromatin landscape to the diversification of immunity and the germline. Growing evidence points to a role of aberrant DSB physiology in human disease and an understanding of these processes may both inform the design of new therapeutic strategies and reduce off-target effects of existing drugs. Here, we review the wide-ranging roles of physiological DSBs and the emerging network of their multilateral regulation to consider how the cell is able to harness DNA breaks as a critical biochemical tool.

Understanding specific functions of PARP-2: new lessons for cancer therapy.

Poly(ADP-ribosyl)ation (PARylation) is a widespread and highly conserved post-translational modification catalysed by a large family of enzymes called poly(ADP-ribose) polymerases (PARPs). PARylation plays an essential role in various cardinal processes of cellular physiology and recent approvals and breakthrough therapy designations for PARP inhibitors in cancer therapy have sparked great interest in pharmacological targeting of PARP proteins. Although, many PARP inhibitors have been developed, existing compounds display promiscuous inhibition across the PARP superfamily which could lead to unwanted off-target effects. Thus the prospect of isoform-selective inhibition is being increasingly explored and research is now focusing on understanding specific roles of PARP family members. PARP-2, alongside PARP-1 and PARP-3 are the only known DNA damage-dependent PARPs and play critical roles in the DNA damage response, DNA metabolism and chromatin architecture. However, growing evidence shows that PARP-2 plays specific and diverse regulatory roles in cellular physiology, ranging from genomic stability and epigenetics to proliferative signalling and inflammation. The emerging network of PARP-2 target proteins has uncovered wide-ranging functions of the molecule in many cellular processes commonly dysregulated in carcinogenesis. Here, we review novel PARP-2-specific functions in the hallmarks of cancer and consider the implications for the development of isoform-selective inhibitors in chemotherapy. By considering the roles of PARP-2 through the lens of tumorigenesis, we propose PARP-2-selective inhibition as a potentially multipronged attack on cancer physiology.

Case reports: cutaneous small vessel vasculitis due to famciclovir therapy.

Cutaneous hypersensitivity vasculitis is often idiopathic, but may be the result of therapeutic drugs. It is important to be aware of previously unreported drugs that may be associated with this complication. We report a case of cutaneous hypersensitivity vasculitis due to famciclovir therapy. To our knowledge, this is the first report of this interaction in the medical literature in English.

Clinical indications and results after chest wall resection for recurrent mesothelioma.

OBJECTIVE: The ipsilateral hemithorax is the most common site of recurrence after surgical resection for malignant pleural mesothelioma. Salvage treatment has generally been ineffective. We reviewed the outcomes after resection of isolated ipsilateral chest recurrence after cytoreductive surgery in patients with malignant pleural mesothelioma. METHODS: Patients with malignant pleural mesothelioma who underwent initial surgical resection at our institution from 1988 to 2011 and were subsequently treated for localized recurrence with an additional chest resection were identified and their data retrospectively reviewed. RESULTS: A total of 1142 patients underwent either extrapleural pneumonectomy (n = 794) or pleurectomy/decortication (n = 348). Of the patients who returned for follow-up, 47 (4.1%) had chest wall recurrence amenable to resection. The location of recurrence was predominantly incisional (49%) and/or costophrenic (38%). The median time to recurrence after either extrapleural pneumonectomy or pleurectomy/decortication was 16.1 months (range, 2.7-58.2). No 30-day mortality was found for chest wall resection, and the median length of stay in the hospital was 3 days (range, 0-12). The median overall survival duration after chest wall resection correlated positively with the time to recurrence (epithelial: median, 8.9, 17.2, and 35.8 months for a time to recurrence of <12, 12 to <24, and ≥24 months, respectively; biphasic: median, 2.7 and 15.9 months for a time to recurrence of <10 and ≥10 months, respectively). CONCLUSIONS: Chest wall resection is a safe and effective therapeutic option in the management of localized chest wall recurrence of malignant pleural mesothelioma. The time to recurrence appears to be predictive of the expected survival benefit in both epithelial and biphasic malignant pleural mesothelioma.