A meta-analysis of reversion mutations in BRCA genes identifies signatures of DNA end-joining repair mechanisms driving therapy resistance.

BACKGROUND: Germline mutations in the BRCA1 or BRCA2 (BRCA) genes predispose to hereditary breast and ovarian cancer and, mostly in the case of BRCA2, are also prevalent in cases of pancreatic and prostate malignancies. Tumours from these patients tend to lose both copies of the wild-type BRCA gene, which makes them exquisitely sensitive to platinum drugs and poly(ADP-ribose) polymerase inhibitors (PARPi), treatments of choice in these disease settings. Reversion secondary mutations with the capacity of restoring BRCA protein expression have been documented in the literature as bona fide mechanisms of resistance to these treatments. PATIENTS AND METHODS: We analysed published sequencing data of BRCA genes (from tumour or circulating tumour DNA) in 327 patients with tumours harbouring mutations in BRCA1 or BRCA2 (234 patients with ovarian cancer, 27 with breast cancer, 13 with pancreatic cancer, 11 with prostate cancer and 42 with a cancer of unknown origin) that progressed on platinum or PARPi treatment. RESULTS: We describe 269 cases of reversion mutations in 86 patients in this cohort (26.0%). Detailed analyses of the reversion events highlight that most amino acid sequences encoded by exon 11 in BRCA1 and BRCA2 are dispensable to generate resistance to platinum or PARPi, whereas other regions are more refractory to sizeable amino acid losses. They also underline the key role of mutagenic end-joining DNA repair pathways in generating reversions, especially in those affecting BRCA2, as indicated by the significant accumulation of DNA sequence microhomologies surrounding deletions leading to reversion events. CONCLUSIONS: Our analyses suggest that pharmacological inhibition of DNA end-joining repair pathways could improve durability of drug treatments by preventing the acquisition of reversion mutations in BRCA genes. They also highlight potential new therapeutic opportunities when reversions result in expression of hypomorphic versions of BRCA proteins, especially with agents targeting the response to DNA replication stress.

RAD51 foci as a functional biomarker of homologous recombination repair and PARP inhibitor resistance in germline BRCA-mutated breast cancer.

Background: BRCA1 and BRCA2 (BRCA1/2)-deficient tumors display impaired homologous recombination repair (HRR) and enhanced sensitivity to DNA damaging agents or to poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi). Their efficacy in germline BRCA1/2 (gBRCA1/2)-mutated metastatic breast cancers has been recently confirmed in clinical trials. Numerous mechanisms of PARPi resistance have been described, whose clinical relevance in gBRCA-mutated breast cancer is unknown. This highlights the need to identify functional biomarkers to better predict PARPi sensitivity. Patients and methods: We investigated the in vivo mechanisms of PARPi resistance in gBRCA1 patient-derived tumor xenografts (PDXs) exhibiting differential response to PARPi. Analysis included exome sequencing and immunostaining of DNA damage response proteins to functionally evaluate HRR. Findings were validated in a retrospective sample set from gBRCA1/2-cancer patients treated with PARPi. Results: RAD51 nuclear foci, a surrogate marker of HRR functionality, were the only common feature in PDX and patient samples with primary or acquired PARPi resistance. Consistently, low RAD51 was associated with objective response to PARPi. Evaluation of the RAD51 biomarker in untreated tumors was feasible due to endogenous DNA damage. In PARPi-resistant gBRCA1 PDXs, genetic analysis found no in-frame secondary mutations, but BRCA1 hypomorphic proteins in 60% of the models, TP53BP1-loss in 20% and RAD51-amplification in one sample, none mutually exclusive. Conversely, one of three PARPi-resistant gBRCA2 tumors displayed BRCA2 restoration by exome sequencing. In PDXs, PARPi resistance could be reverted upon combination of a PARPi with an ataxia-telangiectasia mutated (ATM) inhibitor. Conclusion: Detection of RAD51 foci in gBRCA tumors correlates with PARPi resistance regardless of the underlying mechanism restoring HRR function. This is a promising biomarker to be used in the clinic to better select patients for PARPi therapy. Our study also supports the clinical development of PARPi combinations such as those with ATM inhibitors.

Does the Presence of Scrapie Affect the Ability of Current Statutory Discriminatory Tests To Detect the Presence of Bovine Spongiform Encephalopathy?

Current European Commission (EC) surveillance regulations require discriminatory testing of all transmissible spongiform encephalopathy (TSE)-positive small ruminant (SR) samples in order to classify them as bovine spongiform encephalopathy (BSE) or non-BSE. This requires a range of tests, including characterization by bioassay in mouse models. Since 2005, naturally occurring BSE has been identified in two goats. It has also been demonstrated that more than one distinct TSE strain can coinfect a single animal in natural field situations. This study assesses the ability of the statutory methods as listed in the regulation to identify BSE in a blinded series of brain samples, in which ovine BSE and distinct isolates of scrapie are mixed at various ratios ranging from 99% to 1%. Additionally, these current statutory tests were compared with a new in vitro discriminatory method, which uses serial protein misfolding cyclic amplification (sPMCA). Western blotting consistently detected 50% BSE within a mixture, but at higher dilutions it had variable success. The enzyme-linked immunosorbent assay (ELISA) method consistently detected BSE only when it was present as 99% of the mixture, with variable success at higher dilutions. Bioassay and sPMCA reported BSE in all samples where it was present, down to 1%. sPMCA also consistently detected the presence of BSE in mixtures at 0.1%. While bioassay is the only validated method that allows comprehensive phenotypic characterization of an unknown TSE isolate, the sPMCA assay appears to offer a fast and cost-effective alternative for the screening of unknown isolates when the purpose of the investigation was solely to determine the presence or absence of BSE.

The influence of mechanical Circulatory support on post-transplant outcomes in pediatric patients: A multicenter study from the International Society for Heart and Lung Transplantation (ISHLT) Registry.

BACKGROUND: Mechanical circulatory support (MCS) is increasingly being used as a bridge to transplant in pediatric patients. We compare outcomes in pediatric patients bridged to transplant with MCS from an international cohort. METHODS: This retrospective cohort study of heart-transplant patients reported to the International Society for Heart and Lung Transplantation (ISHLT) registry from 2005-2017 includes 5,095 patients <18 years. Pretransplant MCS exposure and anatomic diagnosis were derived. Outcomes included mortality, renal failure, and stroke. RESULTS: 26% of patients received MCS prior to transplant: 240 (4.7%) on extracorporeal membrane oxygenation (ECMO), 1,030 (20.2%) on ventricular assist device (VAD), and 54 (1%) both. 29% of patients were <1 year, and 43.8% had congenital heart disease (CHD). After adjusting for clinical characteristics, compared to no-MCS and VAD, ECMO had higher mortality during their transplant hospitalization [OR 3.97 & 2.55; 95% CI 2.43-6.49 & 1.42-4.60] while VAD mortality was similar [OR 1.55; CI 0.99-2.45]. Outcomes of ECMO+VAD were similar to ECMO alone, including increased mortality during transplant hospitalization compared to no-MCS [OR 4.74; CI 1.81-12.36]. Patients with CHD on ECMO had increased 1 year, and 10 year mortality [HR 2.36; CI 1.65-3.39], [HR 1.82; CI 1.33-2.49]; there was no difference in survival in dilated cardiomyopathy (DCM) patients based on pretransplant MCS status. CONCLUSION: Survival in CHD and DCM is similar in patients with no MCS or VAD prior to transplant, while pretransplant ECMO use is strongly associated with mortality after transplant particularly in children with CHD. In children with DCM, long term survival was equivalent regardless of MCS status.

Regions of cerebral ischemia located by pyridine nucleotide fluorescence.

The fluorescence of the reduced form of the endogenous pyridine nucleotide nicotinamide adenine dinucleotide was used to map regions of ischemia in cat brain. A remarkably microheterogeneous pattern of increased fluorescence resulted from a critical level of incomplete cerebral ischemia. The fluorescence pattern suggests that ischemia occurs initially in microwatershed zones between penetrating cerebral arteries.

Premature twins of a mother with Graves' disease with discordant thyroid function: a case report.

Thyroid dysfunction is recognized in the newborns of mothers affected by Graves' disease during pregnancy. We describe the development of concurrent hyperthyroidism and hypothyroidism in the twin infants of a mother with Graves' disease diagnosed during pregnancy.

Long term follow up of nasolacrimal intubation in adults.

BACKGROUND/AIMS: The authors have previously reported a short term mean 15 month follow up of nasolacrimal intubation in adults. The effectiveness of this procedure for long term (mean 78 months) control of epiphoria is assessed here. METHODS: 65 eyes from 40 patients who underwent nasolacrimal intubation were followed. Mean age at intubation was 59.2 years. The mean follow up period was 6.2 years. The results were based on long term symptomatic improvement. RESULTS: Complete long term resolution of symptoms was reported in 50.7%. A partial improvement was reported in 38.5%, and no improvement in 10.7%. A better outcome was associated with a canalicular than nasolacrimal duct obstruction. On long term follow up 16.9% required dacrocysto-rhinostomy (DCR). CONCLUSION: Nasolacrimal intubation, a minimally invasive procedure is successful in the long term control of epiphora. Selection of patients with canalicular duct obstruction gives higher success rates with fewer patients subsequently requiring the DCR procedure.

Presurgical electroencephalographic patterns and outcome from anterior temporal lobectomy.

We reviewed data from 48 patients after anterior temporal lobe resection for medically intractable epilepsy. All had ictal electro-encephalographic (EEG) evidence of unilateral temporal lobe onset. Depth electrodes were used in 19 patients. Successful surgical outcome correlated significantly with factors that suggested a temporal lobe focus, particularly in the interictal scalp EEG. The most successful outcome occurred in patients with well-localized unilateral interictal temporal spikes (100% improved). The group with well-localized bilateral temporal spikes also did well (76% improved). Patients with extratemporal spread of the interictal spike on scalp EEG, either unilaterally or bilaterally, did less well. Only one third improved, despite extensive extracranial and intracranial monitoring, when indicated. The interictal scalp EEG may be the only EEG necessary for the presurgical evaluation of selected patients with intractable temporal lobe epilepsy.

Comparison of depth and subdural electrodes in recording temporal lobe seizures.

Intracranial EEG recording is often required to identify an area of the brain for resective surgery for intractable epilepsy. We simultaneously compared bilaterally placed depth and limited subdural electrode EEG to determine the most effective method of recording seizures from the temporal lobes. Localized complex partial seizures usually appeared earlier in hippocampal depth electrodes and spread later to subdural recording sites. In 3 patients, hippocampal recordings showed localized seizure origin but subdural recording was nonlocalizing due to rapid bilateral seizure propagation. In 1 patient with nonlocalized seizures presumably of extratemporal origin, subdural electrodes incorrectly lateralized seizure origin to a temporal lobe. Auras and subclinical seizures detected by depth electrode recording were often not evident with subdural electrodes. We conclude that EEG recording with hippocampal depth electrodes correctly identifies and lateralizes temporal lobe seizures more often than with limited subdural electrodes.

Cardiac rhythm during temporal lobe seizures.

We studied the neuroanatomic correlates of ictal tachycardia in 27 seizures from five patients with unilateral temporal lobe epilepsy being evaluated with bilateral temporal lobe depth electrodes and orbitofrontal subdural electrodes. There were 11 complex partial seizures, three simple partial seizures, and 13 subclinical seizures. For all seizures, heart rate (HR) increased in a graded fashion as new cortical regions anywhere in the brain were recruited into the seizure. HR plateaued at the new level despite EEG frequency changes until the next region became involved. Increases in HR did not correlate with increased duration of seizures but rather with volume of brain involved. Restricted amygdaloid seizure activity was generally insufficient to alter HR. We conclude that the amygdala has a limited role in modulating HR during seizures, and ictal tachycardia depends principally on the volume of cerebral structures recruited into a seizure.

The syndrome of frontal lobe epilepsy: characteristics and surgical management.

We reviewed the historical features, preoperative diagnostic evaluation, operative procedure, and surgical outcome in 16 patients with refractory frontal lobe epilepsy. Clinical expression of the epilepsy varied widely, particularly with respect to seizure characteristics, although high monthly seizure frequency and absence of a risk factor for epilepsy before age 5 occurred more often than in reported in temporal lobe epilepsy patients. Seizures often caused early bilateral movements, were brief, and lacked oroalimentary automatisms and a prolonged postictal state. Both the interictal and ictal scalp EEGs had relatively poor sensitivity and specificity and often either contained no epileptiform abnormalities or were misleading. MRI usually identified structural lesions when these were present, although it was negative in two patients with tumors. In the absence of an MRI lesion, intracranial EEG usually identified the area to be resected, although it too provided misleading information in one case. Surgical procedures consisted of focal resections with or without anterior corpus callosotomy, or of corpus callosotomy alone. Nearly all patients improved after surgery, with a majority (67%) becoming seizure-free (average follow-up, 46 months). Preoperative seizure frequency correlated with seizure relief after surgery, as did age of seizure onset, whereas presence of tumor did not. We conclude that frontal lobe epilepsy warrants aggressive investigation and that surgical treatment often can be successful.

Magnetic resonance imaging after corpus callosotomy.

Magnetic resonance imaging (MRI) can visualize the extent of corpus callosotomy performed for medically intractable epilepsy not amenable to focal surgery. Five patients underwent complete callosotomy and one an anterior callosotomy, aged 19 to 24 years, 21 to 53 months (prior to scanning). T1 images showed complete absence of the callosal shadow in five cases and visualization of the genu and splenium in the sixth case. T2-weighted pulse sequence spin-echo MRI showed intense image throughout the region of the entire callosum in the two cases with the longest postoperative course. The two middle cases showed intense T2 signal from the splenium, and the two latest showed no increase in T2 signal. We believe the increase in T2 signal in the transected callosum may represent an in vivo example of anisomorphic gliosis. T1 images demonstrate the anatomic extent of transection, while T2 images demonstrate the chemical and pathophysiologic sequence of transection. Thus, MRI is the imaging test of choice to evaluate callosotomy patients.

Occupational outcome after temporal lobectomy for refractory epilepsy.

We evaluated employment after temporal lobectomy for refractory epilepsy in 86 patients (3.5 to 8 years of follow-up). Seventy-three patients qualified for the work force before and after surgery. Unemployment rates declined after surgery (18 patients [25%] unemployed before surgery, eight patients [11%] unemployed after surgery), and underemployment also tended to diminish. Improvement in occupational status related strongly to the degree of postoperative seizure relief. Seizure-free patients fared better (no unemployment, little underemployment) than patients with some seizure-free years and some years with seizures after surgery, whose high underemployment level persisted. Patients with seizures in each year after surgery fared worst (despite reduced seizure frequency), with increased unemployment after surgery. Age at surgery also influenced vocational outcome in patients who were unemployed before surgery. Historical, educational, cognitive, and behavioral measures did not correlate with vocational outcome. Employment gains came slowly; unemployed patients took up to 6 years to obtain work after surgery. Of 13 students at the time of surgery, 11 have graduated and nine are now employed. We conclude that seizures play a large role in limiting employment, and that by alleviating seizures, temporal lobectomy improves employability in people with refractory epilepsy. Surgery thereby provides benefit to individuals with epilepsy by increasing financial independence and to society by reducing unemployment.

Seizures in temporal lobe epilepsy: I. Reliability of scalp/sphenoidal ictal recording.

We determined both (1) the reliability (reproducibility) of seizure onset location in patients with temporal lobe recorded with extracranial EEG and (2) if interictal spike (IIS) location influences that reliability. EEGs were recorded with the 10-20 system and sphenoidal electrodes. Between 1985 and 1993, 166 patients with suspected temporal lobe epilepsy were eligible for inclusion with a total of 734 seizures recorded. Each seizure onset was classified as either localized, lateralized, or nonlocalized. Individual patients were then grouped according to interictal spike location (i.e., unilateral, bilateral, or none) as well as by ictal onset reproducibility patterns (i.e., concordant, semiconcordant, conflicting, or nonlocalized) based on each patient's monitoring session. Seizure onset location was reproducible in 68% of the cases and variable patterns of seizure onset were seen in 32% of patients. Patients with unilateral IIS (68%) were more likely to have consistent ictal onset patterns than patients with bilateral IIS (27%). The first seizure more often predicted subsequent seizure onset patterns when it was localized than when it was nonlocalized. Of 18 patients with conflicting temporal lobe seizures, up to four seizures were necessary to detect independent bilateral temporal lobe seizures.

Temporal lobectomy outcome in older versus younger adults.

A total of 340 patients age 50 years and older were compared with 30 patients younger than 50 years, all of whom had anterior temporal lobectomy for refractory epilepsy. Seizure outcome, neuropsychological test scores, and change in driving status were analyzed. Age and duration of epilepsy were related independently to outcome, but laterality of interictal sharp waves (an early epilepsy risk factor) and presence of tumor were not. Sixteen patients (52%) in the older group and 257 patients (75.6%) in the younger group (p < 0.008) were seizure free. Postoperative neuropsychological outcome and driving status were similar in older and younger patients.

Hemispheric control of the writing hand: the effect of callosotomy in a left-hander.

We report a case of a left-hander with left hemispheric language. After callosotomy, he could use the left hand to write only random letters and digits, and he became right-handed for writing. Therefore, writing by left-handers with left hemispheric language dominance may be accomplished by transcallosal transmission of the linguistic content from the left hemisphere to the right.

Memory during subclinical hippocampal seizures.

We performed neuropsychological testing in 2 patients during subclinical hippocampal seizures recorded with depth electrodes. Neither subject showed impairment of consciousness, orientation, motor skills, or verbal fluency. The rapidity of recall of a well-learned word list was impaired in 1 subject during ictal fast spiking in the left hippocampus. Subclinical seizure activity may be responsible for a portion of the memory deficits found in patients with epilepsy.

Predictors of outcome after anterior temporal lobectomy: the intracarotid amobarbital test.

The intracarotid amobarbital test (IAT) examines hemispheric memory and language. We set out to determine whether memory performance on the IAT correlated with seizure relief after anterior temporal lobectomy in 117 patients with refractory epilepsy. The IAT assessed recognition memory performance for nine items with correction for false-positive recognitions. We then compared performance of one hemisphere with that of the other, defining a correctly lateralized memory deficit as worse performance when using the hemisphere containing the operated temporal lobe than when using the other hemisphere. The analysis included concurrent factors that might also affect outcome, such as age at first risk for epilepsy, presence or absence of tumor, and Full Scale IQ. A discriminant function analysis demonstrated that patients with a correctly lateralized memory deficit on the IAT had an increased probability of being seizure-free following surgery after controlling for other predictors. The performance of the nonoperated temporal lobe related to outcome, although less strongly. The magnitude of the difference in performance between the two hemispheres and the performance of the operated hemisphere did not relate to outcome. Patients who became seizure-free had an earlier age at first risk than did those with persistent seizures, and tumor presence weakly correlated with postoperative outcome. IQ did not correlate with outcome. We conclude that the IAT predicts seizure relief after anterior temporal lobectomy independent of other known risk factors we examined.

Predictors of outcome after anterior temporal lobectomy: positron emission tomography.

We assessed the relationship between temporal lobe metabolism measured quantitatively and qualitatively with PET using [18F]-fluorodeoxyglucose (FDG) and postoperative seizure frequency after anterior temporal lobectomy. Forty-three patients with refractory partial epilepsy had anterior temporal lobectomy and preoperative assessment with PET-FDG. Qualitative PET analysis was performed visually by two blinded observers, and quantitative PET analysis was performed using an anatomic template for six control and six temporal lobe subregions, deriving an asymmetry index for each region. Seizure outcome was assessed 1 year after surgery; patients were classified as being seizure-free or as having persistent seizures. Qualitative data were analyzed using Fisher's exact test and the t test, and quantitative data were analyzed using a repeated-measures ANOVA. Thirty-two patients (74%) were seizure-free at follow-up, and 11 had persistent seizures, although most improved. Twenty-nine of 35 patients (83%) with restricted temporal lobe hypometabolism by visual analysis were seizure-free, compared with three of eight patients (37.5%) with normal scans or multilobar hypometabolism. Quantitative analysis revealed that an asymmetry of mesial temporal lobe glucose consumption (uncal region) correlated with improved surgical outcome (p < 0.02). We developed a logistic regression model to predict individual outcome based on the asymmetry in uncal metabolism. Lateral temporal metabolism did not correlate with outcome. We conclude that both visual PET analysis and quantitative PET analysis predict outcome after temporal lobectomy, although quantitative measures offer more precise information.

A noninvasive protocol for anterior temporal lobectomy.

We report the results of a protocol for choosing candidates for temporal lobectomy using a standard battery of objective tests without intracranial electrodes. We assigned each test a level of importance, and an algorithm was used to determine whether temporal lobectomy could be performed. Fifty-one patients (total pool, 103 patients) met protocol requirements and had an anterior temporal lobectomy with a mean follow-up of 39.4 months (range, 21 to 64 months), most remaining on anticonvulsant therapy. Eighty percent are seizure free, 12% have less than 3 seizures per year or only nocturnal seizures, and 8% have greater than 80% reduction in seizure frequency. One-third of patients who failed protocol criteria did not have temporal lobe seizures when studied with intracranial electrodes. We analyzed and modified the algorithm after comparing these patients with others who were poor candidates for temporal lobectomy. We conclude that this protocol is effective and recommend using such an objective algorithm.