Epidermal Growth Factor Receptor Mutations.

Up to 20% of lung adenocarcinomas in the United States and Europe and 50% in Asia have activating mutations of the tyrosine kinase domain of the epidermal growth factor receptor (EGFR). The identification and subsequent targeting of mutations with EGFR-tyrosine kinase inhibitors (TKIs) led to significant advances in treatment of EGFR-mutant lung cancer. Newer-generation EGFR-TKIs resulted in improvement in outcomes, with less toxic side effects and better tolerability. Resistance to EGFR-TKIs remains a significant barrier, and better understanding of resistance mechanisms is needed. Efforts are ongoing to incorporate targeted therapy into treatment of patients with earlier-stage disease.

Evaluation of cardiomyopathy in acute myeloid leukemia patients treated with anthracyclines.

BACKGROUND: Acute myeloid leukemia patients receive anthracycline-containing induction chemotherapy. Anthracyclines cause cardiotoxicity; however, there is a paucity of data reflecting the risk of cardiotoxicity in the acute myeloid leukemia population, and risk factors for development of reduced left ventricular ejection fraction are not well established in this population. METHODS: A retrospective cohort study of adult acute myeloid leukemia patients receiving anthracycline-containing induction chemotherapy between March 2011 and August 2017 was performed. Baseline and all additional cardiac monitoring within one year of induction were collected. Home medications and new medication initiation were determined via the electronic health record and new outpatient prescriptions. RESULTS: Of 97 evaluable patients, 25 (25.8%) developed reduced left ventricular ejection fraction and 18 (18.6%) experienced clinical heart failure within one year of induction. The median difference from baseline to lowest left ventricular ejection fraction was -5.0 percentage points, with a range of +10.0 to -52.5. The median time to onset of reduced left ventricular ejection fraction was 27 days, at a median cumulative anthracycline dose of 270 mg/m2. No patient-specific or medication-specific factors were significantly associated with the risk of developing reduced left ventricular ejection fraction. Of 14 patients started on medical management for reduced left ventricular ejection fraction, 10 (71%) responded to therapy. CONCLUSIONS: In this retrospective analysis, we observed that acute myeloid leukemia patients experienced reduced left ventricular ejection fraction more quickly and at lower doses than previously reported in the solid tumor population. Reduced left ventricular ejection fraction was at least partially reversible in most patients started on medical management. Although no factors were significantly associated with decreased cardiomyopathy risk, future assessment of cardioprotective medications may be warranted.

Induced pluripotent stem cells with a mitochondrial DNA deletion.

In congenital mitochondrial DNA (mtDNA) disorders, a mixture of normal and mutated mtDNA (termed heteroplasmy) exists at varying levels in different tissues, which determines the severity and phenotypic expression of disease. Pearson marrow pancreas syndrome (PS) is a congenital bone marrow failure disorder caused by heteroplasmic deletions in mtDNA. The cause of the hematopoietic failure in PS is unknown, and adequate cellular and animal models are lacking. Induced pluripotent stem (iPS) cells are particularly amenable for studying mtDNA disorders, as cytoplasmic genetic material is retained during direct reprogramming. Here, we derive and characterize iPS cells from a patient with PS. Taking advantage of the tendency for heteroplasmy to change with cell passage, we isolated isogenic PS-iPS cells without detectable levels of deleted mtDNA. We found that PS-iPS cells carrying a high burden of deleted mtDNA displayed differences in growth, mitochondrial function, and hematopoietic phenotype when differentiated in vitro, compared to isogenic iPS cells without deleted mtDNA. Our results demonstrate that reprogramming somatic cells from patients with mtDNA disorders can yield pluripotent stem cells with varying burdens of heteroplasmy that might be useful in the study and treatment of mitochondrial diseases.

Genome-wide mapping of 5-hydroxymethylcytosine in embryonic stem cells.

5-hydroxymethylcytosine (5hmC) is a modified base present at low levels in diverse cell types in mammals. 5hmC is generated by the TET family of Fe(II) and 2-oxoglutarate-dependent enzymes through oxidation of 5-methylcytosine (5mC). 5hmC and TET proteins have been implicated in stem cell biology and cancer, but information on the genome-wide distribution of 5hmC is limited. Here we describe two novel and specific approaches to profile the genomic localization of 5hmC. The first approach, termed GLIB (glucosylation, periodate oxidation, biotinylation) uses a combination of enzymatic and chemical steps to isolate DNA fragments containing as few as a single 5hmC. The second approach involves conversion of 5hmC to cytosine 5-methylenesulphonate (CMS) by treatment of genomic DNA with sodium bisulphite, followed by immunoprecipitation of CMS-containing DNA with a specific antiserum to CMS. High-throughput sequencing of 5hmC-containing DNA from mouse embryonic stem (ES) cells showed strong enrichment within exons and near transcriptional start sites. 5hmC was especially enriched at the start sites of genes whose promoters bear dual histone 3 lysine 27 trimethylation (H3K27me3) and histone 3 lysine 4 trimethylation (H3K4me3) marks. Our results indicate that 5hmC has a probable role in transcriptional regulation, and suggest a model in which 5hmC contributes to the 'poised' chromatin signature found at developmentally-regulated genes in ES cells.

Telomere elongation in induced pluripotent stem cells from dyskeratosis congenita patients.

Patients with dyskeratosis congenita (DC), a disorder of telomere maintenance, suffer degeneration of multiple tissues. Patient-specific induced pluripotent stem (iPS) cells represent invaluable in vitro models for human degenerative disorders like DC. A cardinal feature of iPS cells is acquisition of indefinite self-renewal capacity, which is accompanied by induction of the telomerase reverse transcriptase gene (TERT). We investigated whether defects in telomerase function would limit derivation and maintenance of iPS cells from patients with DC. Here we show that reprogrammed DC cells overcome a critical limitation in telomerase RNA component (TERC) levels to restore telomere maintenance and self-renewal. We discovered that TERC upregulation is a feature of the pluripotent state, that several telomerase components are targeted by pluripotency-associated transcription factors, and that in autosomal dominant DC, transcriptional silencing accompanies a 3' deletion at the TERC locus. Our results demonstrate that reprogramming restores telomere elongation in DC cells despite genetic lesions affecting telomerase, and show that strategies to increase TERC expression may be therapeutically beneficial in DC patients.

Systematic molecular genetic analysis of congenital sideroblastic anemia: evidence for genetic heterogeneity and identification of novel mutations.

BACKGROUND: Sideroblastic anemias are heterogeneous congenital and acquired bone marrow disorders characterized by pathologic iron deposits in mitochondria of erythroid precursors. Among the congenital sideroblastic anemias (CSAs), the most common form is X-linked sideroblastic anemia, due to mutations in 5-aminolevulinate synthase (ALAS2). A novel autosomal recessive CSA, caused by mutations in the erythroid specific mitochondrial transporter SLC25A38, was recently defined. Other known etiologies include mutations in genes encoding the thiamine transporter SLC19A2, the RNA-modifying enzyme pseudouridine synthase 1 (PUS1), a mitochondrial ATP-binding cassette transporter (ABCB7), glutaredoxin 5 (GLRX5), as well as mitochondrial DNA deletions. Despite these known diverse causes, in a substantial portion of CSA cases a presumed genetic defect remains unknown. PROCEDURE: In the context of the recent discovery of SLC25A38 as a major novel cause, we systematically analyzed a large cohort of previously unreported CSA patients. Sixty CSA probands (28 females, 32 males) were examined for ALAS2, SLC25A38, PUS1, GLRX5, and ABCB7 mutations. SLC19A2 and mitochondrial DNA were only analyzed if characteristic syndromic features were apparent. RESULTS: Twelve probands had biallelic mutations in SLC25A38. Seven ALAS2 mutations were detected in eight sporadic CSA cases, two being novel. We also identified a novel homozygous null PUS1 mutation and novel mitochondrial DNA deletions in two patients with Pearson syndrome. No mutations were encountered in GLRX5, ABCB7, or SLC19A2. CONCLUSIONS: The remaining undefined probands (43%) can be grouped according to gender, family, and clinical characteristics, suggesting novel X-linked and autosomal recessive forms of CSA.