Post-Transcriptional Dysregulation by miRNAs Is Implicated in the Pathogenesis of Gastrointestinal Stromal Tumor [GIST]

peer-reviewedIn contrast to adult mutant gastrointestinal stromal tumors [GISTs], pediatric/wild-type GISTs remain poorly understood overall, given their lack of oncogenic activating tyrosine kinase mutations. These GISTs, with a predilection for gastric origin in female patients, show limited response to therapy with tyrosine kinase inhibitors and generally pursue a more indolent course, but still may prove fatal. Defective cellular respiration appears to underpin tumor development in these wild-type cases, which as a group lack expression of succinate dehydrogenase [SDH] B, a surrogate marker for respiratory chain metabolism. Yet, only a small subset of the wild-type tumors show mutations in the genes coding for the SDH subunits [SDHx]. To explore additional pathogenetic mechanisms in these wild-type GISTs, we elected to investigate posttranscriptional regulation of these tumors by conducting microRNA (miRNA) profiling of a mixed cohort of 73 cases including 18 gastric pediatric wild-type, 25 (20 gastric, 4 small bowel and 1 retroperitoneal) adult wild-type GISTs and 30 gastric adult mutant GISTs. By this approach we have identified distinct signatures for GIST subtypes which correlate tightly with clinico-pathological parameters. A cluster of miRNAs on 14q32 show strikingly different expression patterns amongst GISTs, a finding which appears to be explained at least in part by differential allelic methylation of this imprinted region. Small bowel and retroperitoneal wild-type GISTs segregate with adult mutant GISTs and express SDHB, while adult wildtype gastric GISTs are dispersed amongst adult mutant and pediatric wild-type cases, clustering in this situation on the basis of SDHB expression. Interestingly, global methylation analysis has recently similarly demonstrated that these wild-type, SDHB-immunonegative tumors show a distinct pattern compared with KIT and PDGFRA mutant tumors, which as a rule do express SDHB. All cases with Carney triad within our cohort cluster together tightly.Funding was obtained from the Medical Research Charities Group (http://www.mrcg.ie/) and Health Research Board of Ireland (http://www.hrb.ie) (MO’S), The Children’s Medical and Research Foundation (http://www.cmrf.org) (MO’S), the GIST Cancer Awareness Foundation [GCAF] (http://www. gistawareness.org/)(MO’S), and research grants from the Life Raft Group (http://www.liferaftgroup.org/)(MD-R) and from the Fonds voor Wetenschappelijk Onderzoek Vlaanderen (http://www.fwo.be/)(grant # G.0286.05 MD-R)

Global Chromatin Changes Resulting from Single-Gene Inactivation—The Role of SMARCB1 in Malignant Rhabdoid Tumor

Human cancer typically results from the stochastic accumulation of multiple oncogene-activating and tumor-suppressor gene-inactivating mutations. However, this process takes time and especially in the context of certain pediatric cancer, fewer but more ‘impactful’ mutations may in short order produce the full-blown cancer phenotype. This is well exemplified by the highly aggressive malignant rhabdoid tumor (MRT), where the only gene classically showing recurrent inactivation is SMARCB1, a subunit member of the BAF chromatin-remodeling complex. This is true of all three presentations of MRT including MRT of kidney (MRTK), MRT of the central nervous system (atypical teratoid rhabdoid tumor—ATRT) and extracranial, extrarenal rhabdoid tumor (EERT). Our reverse modeling of rhabdoid tumors with isogenic cell lines, either induced or not induced, to express SMARCB1 showed widespread differential chromatin remodeling indicative of altered BAF complex activity with ensuant histone modifications when tested by chromatin immunoprecipitation followed by sequencing (ChIP-seq). The changes due to reintroduction of SMARCB1 were preponderantly at typical enhancers with tandem BAF complex occupancy at these sites and related gene activation, as substantiated also by transcriptomic data. Indeed, for both MRTK and ATRT cells, there is evidence of an overlap between SMARCB1-dependent enhancer activation and tissue-specific lineage-determining genes. These genes are inactive in the tumor state, conceivably arresting the cells in a primitive/undifferentiated state. This epigenetic dysregulation from inactivation of a chromatin-remodeling complex subunit contributes to an improved understanding of the complex pathophysiological basis of MRT, one of the most lethal and aggressive human cancers

Impact of COVID-19 Pandemic on Caregivers of People with an Intellectual Disability, in Comparison to Carers of Those with Other Disabilities and with Mental Health Issues: A Multicountry Study

Carers supporting people with an intellectual disability often rely on others to manage the burden of care. This research aims to compare the differences between carer groups and understand the predictors of loneliness changes and burden for carers of people with an intellectual disability. Data from the international CLIC study were analysed. In total, 3930 carers responded from four groups; people who care for those with mental health difficulties (n = 491), dementia (n = 1888), physical disabilities (n = 1147), and Intellectual disabilities (n = 404). Cross tabulation and the chi-squared test were used to compare group compositions and binary logistic regression to model predictors within the intellectual disability group. A total of 65% of those caring for people with an intellectual disability experienced increased burden, and 35% of carers of people with an intellectual disability and another condition experienced more severe loneliness. Becoming severely lonely was predicted by feeling burdened by caring (AOR, 15.89) and worsening mental health (AOR, 2.13) Feeling burden was predicted by being aged between 35 and 44 (AOR, 4.24), poor mental health (AOR, 3.51), and feelings of severe loneliness prior to the pandemic (AOR, 2.45). These findings demonstrate that those who were already struggling with caring experienced the greatest difficulties during the COVID-19 lockdowns

miRNAs significantly differentially expressed in post-treatment high-risk cases [Post-HR] when compared to post-treatment intermediate-risk cases [Post-IR-NBl].

<p>miRNAs significantly differentially expressed in post-treatment high-risk cases [Post-HR] when compared to post-treatment intermediate-risk cases [Post-IR-NBl].</p

miRNAs significantly up-regulated within the blastemal component of post-treatment high risk cases [Post-HR] when compared to post-treatment intermediate risk cases [Post-IR-Bl].

<p>miRNAs significantly up-regulated within the blastemal component of post-treatment high risk cases [Post-HR] when compared to post-treatment intermediate risk cases [Post-IR-Bl].</p