1638 Decade-Long Trends in Surgery for Acute Type A Aortic Dissection

Background

Little is known about unwarranted variations in care and outcomes of patients who undergo surgical repair for type A acute aortic dissection(TAAD). We aim to investigate decade-long trends in TAAD surgical repair in England.

Method

Retrospective review of the National Institute for Cardiovascular Outcomes Research (NICOR) National Adult Cardiac Surgery Audit (NACSA) registry from January 2009 to December 2018 , which prospectively collects demographic and peri-operative clinical information for all adult cardiac surgery procedures in the UK.

Results

Over the 10-year period,3,686 TAAD patients underwent surgical repair in England. A steady doubling in the overall number of operations conducted in England was observed from 237 cases recorded in 2009 to 510 in 2018. Number of procedures per hospital per year also doubled, from 10 in 2009 to 21 in 2018. The risk profile of the operated patients remained unchanged. Overall, in-hospital mortality was 17.4% with a trend toward lower mortality in the most recent years (from 22.8% in 2009 to 14.7% in 2018). There was a significant variation in operative mortality across regions with a trend towards lower mortality in regions with a high-volume hospital.

Conclusions

Surgery is the only treatment for acute TAAD but is associated with high mortality. Prompt diagnosis and referral to a specialist center is paramount. The number of operations conducted in England has doubled in 10 years and the associated survival following surgery has improved. Regional variations exist in service provision with a trend towards better survival in high volume centers.

Association of Combination of Conformation-Specific KIT Inhibitors With Clinical Benefit in Patients With Refractory Gastrointestinal Stromal Tumors: A Phase 1b/2a Nonrandomized Clinical Trial

IMPORTANCE

Many cancer subtypes, including KIT-mutant gastrointestinal stromal tumors (GISTs), are driven by activating mutations in tyrosine kinases and may initially respond to kinase inhibitors but frequently relapse owing to outgrowth of heterogeneous subclones with resistance mutations. KIT inhibitors commonly used to treat GIST (eg, imatinib and sunitinib) are inactive-state (type II) inhibitors.

OBJECTIVE

To assess whether combining a type II KIT inhibitor with a conformation-complementary, active-state (type I) KIT inhibitor is associated with broad mutation coverage and global disease control.

DESIGN, SETTING, AND PARTICIPANTS

A highly selective type I inhibitor of KIT, PLX9486, was tested in a 2-part phase 1b/2a trial. Part 1 (dose escalation) evaluated PLX9486 monotherapy in patients with solid tumors. Part 2e (extension) evaluated PLX9486-sunitinib combination in patients with GIST. Patients were enrolled from March 2015 through February 2019; data analysis was performed from May 2020 through July 2020.

INTERVENTIONS

Participants received 250, 350, 500, and 1000 mg of PLX9486 alone (part 1) or 500 and 1000 mg of PLX9486 together with 25 or 37.5 mg of sunitinib (part 2e) continuously in 28-day dosing cycles until disease progression, treatment discontinuation, or withdrawal.

MAIN OUTCOMES AND MEASURES

Pharmacokinetics, safety, and tumor responses were assessed. Clinical efficacy end points (progression-free survival and clinical benefit rate) were supplemented with longitudinal monitoring of KIT mutations in circulating tumor DNA.

RESULTS

A total of 39 PLX9486-naive patients (median age, 57 years [range, 39-79 years]; 22 men [56.4%]; 35 [89.7%] with refractory GIST) were enrolled in the dose escalation and extension parts. The recommended phase 2 dose of PLX9486 was 1000 mg daily. At this dose, PLX9486 could be safely combined with 25 or 37.5 mg daily of sunitinib continuously. Patients with GIST who received PLX9486 at a dose of 500 mg or less, at the recommended phase 2 dose, and with sunitinib had median (95% CI) progression-free survivals of 1.74 (1.54-1.84), 5.75 (0.99-11.0), and 12.1 (1.34-NA) months and clinical benefit rates (95% CI) of 14% (0%-58%), 50% (21%-79%), and 80% (52%-96%), respectively.

CONCLUSIONS AND RELEVANCE

In this phase 1b/2a nonrandomized clinical trial, type I and type II KIT inhibitors PLX9486 and sunitinib were safely coadministered at the recommended dose of both single agents in patients with refractory GIST. Results suggest that cotargeting 2 complementary conformational states of the same kinase was associated with clinical benefit with an acceptable safety profile.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02401815.

Sustained microglial depletion with CSF1R inhibitor impairs parenchymal plaque development in an Alzheimer's disease model

Many risk genes for the development of Alzheimer's disease (AD) are exclusively or highly expressed in myeloid cells. Microglia are dependent on colony-stimulating factor 1 receptor (CSF1R) signaling for their survival. We designed and synthesized a highly selective brain-penetrant CSF1R inhibitor (PLX5622) allowing for extended and specific microglial elimination, preceding and during pathology development. We find that in the 5xFAD mouse model of AD, plaques fail to form in the parenchymal space following microglial depletion, except in areas containing surviving microglia. Instead, Aβ deposits in cortical blood vessels reminiscent of cerebral amyloid angiopathy. Altered gene expression in the 5xFAD hippocampus is also reversed by the absence of microglia. Transcriptional analyses of the residual plaque-forming microglia show they exhibit a disease-associated microglia profile. Collectively, we describe the structure, formulation, and efficacy of PLX5622, which allows for sustained microglial depletion and identify roles of microglia in initiating plaque pathogenesis.

BRD4 Profiling Identifies Critical Chronic Lymphocytic Leukemia Oncogenic Circuits and Reveals Sensitivity to PLX51107, a Novel Structurally Distinct BET Inhibitor

Bromodomain and extra-terminal (BET) family proteins are key regulators of gene expression in cancer. Herein, we utilize BRD4 profiling to identify critical pathways involved in pathogenesis of chronic lymphocytic leukemia (CLL). BRD4 is overexpressed in CLL and is enriched proximal to genes upregulated or de novo expressed in CLL with known functions in disease pathogenesis and progression. These genes, including key members of the B-cell receptor (BCR) signaling pathway, provide a rationale for this therapeutic approach to identify new targets in alternative types of cancer. Additionally, we describe PLX51107, a structurally distinct BET inhibitor with novel in vitro and in vivo pharmacologic properties that emulates or exceeds the efficacy of BCR signaling agents in preclinical models of CLL. Herein, the discovery of the involvement of BRD4 in the core CLL transcriptional program provides a compelling rationale for clinical investigation of PLX51107 as epigenetic therapy in CLL and application of BRD4 profiling in other cancers.Significance: To date, functional studies of BRD4 in CLL are lacking. Through integrated genomic, functional, and pharmacologic analyses, we uncover the existence of BRD4-regulated core CLL transcriptional programs and present preclinical proof-of-concept studies validating BET inhibition as an epigenetic approach to target BCR signaling in CLL. Cancer Discov; 8(4); 458-77. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 371.

Structure-Guided Blockade of CSF1R Kinase in Tenosynovial Giant-Cell Tumor

BACKGROUND

Expression of the colony-stimulating factor 1 (CSF1) gene is elevated in most tenosynovial giant-cell tumors. This observation has led to the discovery and clinical development of therapy targeting the CSF1 receptor (CSF1R).

METHODS

Using x-ray co-crystallography to guide our drug-discovery research, we generated a potent, selective CSF1R inhibitor, PLX3397, that traps the kinase in the autoinhibited conformation. We then conducted a multicenter, phase 1 trial in two parts to analyze this compound. In the first part, we evaluated escalations in the dose of PLX3397 that was administered orally in patients with solid tumors (dose-escalation study). In the second part, we evaluated PLX3397 at the chosen phase 2 dose in an extension cohort of patients with tenosynovial giant-cell tumors (extension study). Pharmacokinetic and tumor responses in the enrolled patients were assessed, and CSF1 in situ hybridization was performed to confirm the mechanism of action of PLX3397 and that the pattern of CSF1 expression was consistent with the pathological features of tenosynovial giant-cell tumor.

RESULTS

A total of 41 patients were enrolled in the dose-escalation study, and an additional 23 patients were enrolled in the extension study. The chosen phase 2 dose of PLX3397 was 1000 mg per day. In the extension study, 12 patients with tenosynovial giant-cell tumors had a partial response and 7 patients had stable disease. Responses usually occurred within the first 4 months of treatment, and the median duration of response exceeded 8 months. The most common adverse events included fatigue, change in hair color, nausea, dysgeusia, and periorbital edema; adverse events rarely led to discontinuation of treatment.

CONCLUSIONS

Treatment of tenosynovial giant-cell tumors with PLX3397 resulted in a prolonged regression in tumor volume in most patients. (Funded by Plexxikon; ClinicalTrials.gov number, NCT01004861.).

Characterizing and Overriding the Structural Mechanism of the Quizartinib-Resistant FLT3 "Gatekeeper" F691L Mutation with PLX3397

Tyrosine kinase domain mutations are a common cause of acquired clinical resistance to tyrosine kinase inhibitors (TKI) used to treat cancer, including the FLT3 inhibitor quizartinib. Mutation of kinase "gatekeeper" residues, which control access to an allosteric pocket adjacent to the ATP-binding site, has been frequently implicated in TKI resistance. The molecular underpinnings of gatekeeper mutation-mediated resistance are incompletely understood. We report the first cocrystal structure of FLT3 with the TKI quizartinib, which demonstrates that quizartinib binding relies on essential edge-to-face aromatic interactions with the gatekeeper F691 residue, and F830 within the highly conserved Asp-Phe-Gly motif in the activation loop. This reliance makes quizartinib critically vulnerable to gatekeeper and activation loop substitutions while minimizing the impact of mutations elsewhere. Moreover, we identify PLX3397, a novel FLT3 inhibitor that retains activity against the F691L mutant due to a binding mode that depends less vitally on specific interactions with the gatekeeper position.

SIGNIFICANCE

We report the first cocrystal structure of FLT3 with a kinase inhibitor, elucidating the structural mechanism of resistance due to the gatekeeper F691L mutation. PLX3397 is a novel FLT3 inhibitor with in vitro activity against this mutation but is vulnerable to kinase domain mutations in the FLT3 activation loop.

The BDGP gene disruption project: single transposon insertions associated with 40% of Drosophila genes

The Berkeley Drosophila Genome Project (BDGP) strives to disrupt each Drosophila gene by the insertion of a single transposable element. As part of this effort, transposons in >30,000 fly strains were localized and analyzed relative to predicted Drosophila gene structures. Approximately 6300 lines that maximize genomic coverage were selected to be sent to the Bloomington Stock Center for public distribution, bringing the size of the BDGP gene disruption collection to 7140 lines. It now includes individual lines predicted to disrupt 5362 of the 13,666 currently annotated Drosophila genes (39%). Other lines contain an insertion at least 2 kb from others in the collection and likely mutate additional incompletely annotated or uncharacterized genes and chromosomal regulatory elements. The remaining strains contain insertions likely to disrupt alternative gene promoters or to allow gene misexpression. The expanded BDGP gene disruption collection provides a public resource that will facilitate the application of Drosophila genetics to diverse biological problems. Finally, the project reveals new insight into how transposons interact with a eukaryotic genome and helps define optimal strategies for using insertional mutagenesis as a genomic tool.

All delays before radiotherapy risk progression of Merkel cell carcinoma

Prolonged waiting times for radiotherapy have resulted in many centres assigning priorities to various patient or diagnostic groups. A high risk of progression on a waiting list is one factor that would reasonably influence the priority. The present descriptive study of 27 patients with Merkel cell carcinoma (MCC) found that a median wait of 24 days for radiotherapy is associated with a high risk of progression. Eleven (41%) of 27 patients developed progressive disease, including five (45%) of 11 patients waiting for adjuvant radiotherapy. Patients treated adjuvantly also had longer waiting times prior to their initial radiotherapy consultation (median 41 days), which may have contributed to the rate of progression. Merkel cell carcinoma is an aggressive but curable malignancy and appropriate management should include efforts to minimize all potential delays prior to the commencement of radiotherapy.

Drosophila melanogaster MNK/Chk2 and p53 regulate multiple DNA repair and apoptotic pathways following DNA damage

We have used genetic and microarray analysis to determine how ionizing radiation (IR) induces p53-dependent transcription and apoptosis in Drosophila melanogaster. IR induces MNK/Chk2-dependent phosphorylation of p53 without changing p53 protein levels, indicating that p53 activity can be regulated without an Mdm2-like activity. In a genome-wide analysis of IR-induced transcription in wild-type and mutant embryos, all IR-induced increases in transcript levels required both p53 and the Drosophila Chk2 homolog MNK. Proapoptotic targets of p53 include hid, reaper, sickle, and the tumor necrosis factor family member EIGER: Overexpression of Eiger is sufficient to induce apoptosis, but mutations in Eiger do not block IR-induced apoptosis. Animals heterozygous for deletions that span the reaper, sickle, and hid genes exhibited reduced IR-dependent apoptosis, indicating that this gene complex is haploinsufficient for induction of apoptosis. Among the genes in this region, hid plays a central, dosage-sensitive role in IR-induced apoptosis. p53 and MNK/Chk2 also regulate DNA repair genes, including two components of the nonhomologous end-joining repair pathway, Ku70 and Ku80. Our results indicate that MNK/Chk2-dependent modification of Drosophila p53 activates a global transcriptional response to DNA damage that induces error-prone DNA repair as well as intrinsic and extrinsic apoptosis pathways.

Drosophila p53 binds a damage response element at the reaper locus

The tumor suppressor gene p53 regulates multiple cellular responses to DNA damage, but the transcriptional targets that specify these responses are incompletely understood. We describe a Drosophila p53 homolog and demonstrate that it can activate transcription from a promoter containing binding sites for human p53. Dominant-negative forms of Drosophila p53 inhibit both transactivation in cultured cells and radiation-induced apoptosis in developing tissues. The cis-regulatory region of the proapoptotic gene reaper contains a radiation-inducible enhancer that includes a consensus p53 binding site. Drosophila p53 can activate transcription from this site in yeast and a multimer of this site is sufficient for radiation induction in vivo. These results indicate that reaper is a direct transcriptional target of Drosophila p53 following DNA damage.

mus304 encodes a novel DNA damage checkpoint protein required during Drosophila development

Checkpoints block cell cycle progression in eukaryotic cells exposed to DNA damaging agents. We show that several Drosophila homologs of checkpoint genes, mei-41, grapes, and 14-3-3epsilon, regulate a DNA damage checkpoint in the developing eye. We have used this assay to show that the mutagen-sensitive gene mus304 is also required for this checkpoint. mus304 encodes a novel coiled-coil domain protein, which is targeted to the cytoplasm. Similar to mei-41, mus304 is required for chromosome break repair and for genomic stability. mus304 animals also exhibit three developmental defects, abnormal bristle morphology, decreased meiotic recombination, and arrested embryonic development. We suggest that these phenotypes reflect distinct developmental consequences of a single underlying checkpoint defect. Similar mechanisms may account for the puzzling array of symptoms observed in humans with mutations in the ATM tumor suppressor gene.

An exploration of the sequence of a 2.9-Mb region of the genome of Drosophila melanogaster: the Adh region

A contiguous sequence of nearly 3 Mb from the genome of Drosophila melanogaster has been sequenced from a series of overlapping P1 and BAC clones. This region covers 69 chromosome polytene bands on chromosome arm 2L, including the genetically well-characterized "Adh region." A computational analysis of the sequence predicts 218 protein-coding genes, 11 tRNAs, and 17 transposable element sequences. At least 38 of the protein-coding genes are arranged in clusters of from 2 to 6 closely related genes, suggesting extensive tandem duplication. The gene density is one protein-coding gene every 13 kb; the transposable element density is one element every 171 kb. Of 73 genes in this region identified by genetic analysis, 49 have been located on the sequence; P-element insertions have been mapped to 43 genes. Ninety-five (44%) of the known and predicted genes match a Drosophila EST, and 144 (66%) have clear similarities to proteins in other organisms. Genes known to have mutant phenotypes are more likely to be represented in cDNA libraries, and far more likely to have products similar to proteins of other organisms, than are genes with no known mutant phenotype. Over 650 chromosome aberration breakpoints map to this chromosome region, and their nonrandom distribution on the genetic map reflects variation in gene spacing on the DNA. This is the first large-scale analysis of the genome of D. melanogaster at the sequence level. In addition to the direct results obtained, this analysis has allowed us to develop and test methods that will be needed to interpret the complete sequence of the genome of this species. Before beginning a Hunt, it is wise to ask someone what you are looking for before you begin looking for it. Milne 1926

Comparison of primary coronary artery bypass surgery in a British Indo-Asian and white Caucasian population

AIM

To compare the clinical characteristics, at the time of admission and after coronary revascularization by bypass surgery, among British patients of Indo-Asian and white Caucasian descent.

METHOD

One hundred and ninety-four pairs of patients admitted between November 1994 and January 1997 were matched for age (within 3 years), sex and date of admission (within 3 months). Their clinical characteristics at the time of admission for coronary artery bypass grafting surgery, and the incidence of hospital morbidity, hospital mortality and length of stay in the intensive therapy unit or hospital following coronary artery bypass grafting were determined.

RESULTS

A higher proportion of Indo-Asian patients underwent coronary revascularization on a non-elective basis (43% vs 32% white Caucasian patients, P =0.018), had a higher prevalence of diabetes (39% vs 12%, P =0.0001), a lower prevalence of smoking (36% vs 80%, P =0.0001) and a lower rate of previous myocardial infarction (47% vs 62%, P =0.012). As regards revascularization, although there was no significant difference in the number of vessels revascularized, there was a lower use of the arterial conduit (internal mammary artery) in the Indo-Asian patients (72% vs 81%, P =0.028) particularly for those undergoing emergency/urgent surgery (59% vs 72%, P =0.001) and with a previous myocardial infarction (65% vs 81%;P =0.01) when compared with their white Caucasian counterparts. Following surgery there were no differences in the types of support required for vital functions. There was no significant difference in the proportion of major post-operative complications, that is, haemorrhage, cerebrovascular accident, renal failure requiring dialysis or respiratory failure. Similarly, there were no differences in the length of intensive therapy unit stay (median stay 1 day vs 1 day, P =0.4) and hospital stay following surgery (median stay 6 days vs 6 days, P =0.5) between the two groups. Although there was a trend towards a higher in-hospital (30 day) mortality (6.7% [95% confidence intervals CI 3.18-10.21] vs 2.6% [CI 0.35-4.9;P =0.0618]), in Indo-Asians compared to white Caucasians this trend disappeared when patients in the two groups undergoing non-elective surgery only were compared (9% vs 7%;P =0.7).

CONCLUSIONS

A higher proportion of Indo-Asians underwent non-elective coronary revascularization, with a significantly lower use of the arterial conduit and a relatively higher in-hospital mortality. Following coronary revascularization the medical management, length of stay and hospital morbidity in Indo-Asian patients was no different from that of their white Caucasian counterparts. This is despite a perceived poorer outcome in Indo-Asians compared to white Caucasians.

Is there a role for video-assisted thoracoscopy in the staging of non-small cell lung cancer?

OBJECTIVE

To evaluate the role of video-assisted thoracoscopy (VAT) in the staging of non-small cell lung cancer (NSCLC).

METHODS

In 30 patients (18 male, 12 female, median age 62 (50-78) years) VAT was used to assess the operability of NSCLC in cases where doubt existed after conventional staging investigations had been performed.

RESULTS

VAT was used to assess direct tumour invasion of adjacent organs in 17 patients (mediastinal invasion in 14 and chest wall invasion in 3 patients). In 4 patients with limited respiratory reserve, VAT confirmed the need only for lobectomy prior to thoracotomy. Mediastinal lymph node biopsy was performed in 5 patients with significant (> 1.5 cm) lymphadenopathy on CT scan. VAT was also used to assess bilateral lesions in 4 patients with suspected synchronous tumours. Conversion to thoracotomy was necessary in 4 patients for technical reasons. Successful resection was possible in 17 of the remaining 26 cases, while unnecessary thoracotomy was avoided in 9 patients (30%) with unresectable or benign disease. In 4 patients deemed inoperable on CT scan, VAT staging enabled subsequent resection.

CONCLUSIONS

Video-assisted thoracoscopy appears to have a complementary role in staging NSCLC when other methods are equivocal. It has the potential for increased sensitivity over conventional staging methods.

Sports causing most injuries in Hong Kong

A prospective survey was carried out on 2293 patients attending the Sports Injury Clinic in the Prince of Wales Hospital between May 1984 and December 1990. A Sports Injury Report Form was completed for each patient. Subjects in this study represent a group of nonprofessional and non-élite athletes in a metropolitan area. Soccer, basketball, volleyball, long-distance running and cycling in descending order were the five most common sports causing injury. Different sports produced different injury patterns. In four of the five sports, the knee (27.27-50.47%) and the ankle (16.78-24.67%) were the commonest sites of injury. In cycling, the face (19.46%) was the commonest site of injury. There was a higher injury rate to the lower than the upper limb in soccer, basketball, volleyball and long-distance running, with a ratio of upper- to lower-limb injury ranging from 1:1.13 to 1:46.10. In cycling, upper limb injury was more frequent (upper- to lower-limb injury ratio was 1:0.53). Sprain was the commonest injury overall (44.60%). It was also the commonest injury condition in volleyball (55.15%), basketball (55.34%), soccer (51.41%) and long-distance running (39.33%). In cycling, abrasion (24.83%) was commonest.

Respiratory changes and structure of sleep in young high-altitude dwellers in the Andes of Peru

Sleep organisation in eight young [mean (SD); 20.9 (2.6) years] Peruvian high-altitude residents was studied in a laboratory in Cerro de Pasco at 4300 m. Electroencephalograms, electromyograms, electro-oculograms, electrocardiograms, respiratory movements and arterial oxygen saturation were recorded on an 8-channel Medilog recorder and analysed later in England. Haematocrits ranged from 48% to 64% [57.9 (5.6)%]. The amount of slow wave rapid eye movement (REM) sleep was similar to that reported in young lowlanders sleeping at sea level but very different to the disturbed sleep in visitors sleeping at high altitude. All the Peruvians showed episodes of periodic breathing and respiratory apnoeas [29 (15) night-1] resulting in marked arterial oxygen desaturation [81 (4.5)%; changes of 6 (2.5)%]. These events occurred either during stage 2 or REM sleep and were more frequent in those with lower haematocrits. The amount of wakefulness during the night was 2-3 times greater than would be expected in an age-matched lowland population at sea level. The awakenings were strongly associated with apnoeas (P < 0.02) but were negatively correlated with haematocrit, although this was only significant for seven of the subjects (P < 0.05).

Sleep of Andean high altitude natives

The structure of sleep in lowland visitors to altitudes greater than 4000 m is grossly disturbed. There are no data on sleep in long-term residents of high altitudes. This paper describes an electroencephalographic study of sleep in high altitude dwellers who were born in and are permanent residents of Cerro de Pasco in the Peruvian Andes, situated at 4330 m. Eight healthy male volunteers aged between 18 and 69 years were studied. Sleep was measured on three consecutive nights for each subject. Electroencephalographs, submental electromyographs and electro-oculograms were recorded. Only data from the third night were used in the analysis. The sleep patterns of these subjects resembled the normal sleep patterns described by others in lowlanders at sea level. There were significant amounts of slow wave sleep in the younger subjects and rapid eye movement sleep seemed unimpaired.