Ring chromosome 20

Ring Chromosome 20 syndrome is a rare chromosomal disorder characterized by refractory epilepsy, with seizures in wakefulness and sleep, behavioral problems and mild to severe cognitive impairment. Facial dysmorphism or other congenital malformations are rarely reported making it difficult to diagnose the syndrome based on clinical findings alone. Therefore, diagnosis requires cytogenetic testing. More than 100 cases have been published since the initial report in 1972. In some patients, the ring (20) is found in all cells analyzed and in these cases, the ring is almost always accompanied by deletions of 20pter and/or 20qter. However, in the majority of cases the ring is present in only a proportion of cells, with two normal 20's in the remaining cells (mosaicism), and in these cases, no deletions of chromosome 20 have been observed. Patients with supernumerary r(20) chromosomes have also been identified, but these individuals do not generally have seizures and are not discussed in this review. Characterization by fluorescence in situ hybridization and array-based analysis has shed insight into the molecular composition and possible mechanisms of ring formation, in both the mosaic and non-mosaic patients. The age of onset of seizures correlates with the percentage of cells with the ring in mosaic patients. While the underlying etiology of the phenotype is still not understood, evidence is accumulating which suggests the deletion of candidate genes on chromosome 20 is not responsible. Cytogenetic analysis, rather than chromosomal microarray analysis is recommended for diagnosis of this syndrome, as the mosaic cases do not have copy number alterations and are therefore not identified by array-based analysis

Tracking early lung cancer metastatic dissemination in TRACERx using ctDNA

Circulating tumour DNA (ctDNA) can be used to detect and profile residual tumour cells persisting after curative intent therapy1. The study of large patient cohorts incorporating longitudinal plasma sampling and extended follow-up is required to determine the role of ctDNA as a phylogenetic biomarker of relapse in early-stage non-small-cell lung cancer (NSCLC). Here we developed ctDNA methods tracking a median of 200 mutations identified in resected NSCLC tissue across 1,069 plasma samples collected from 197 patients enrolled in the TRACERx study2. A lack of preoperative ctDNA detection distinguished biologically indolent lung adenocarcinoma with good clinical outcome. Postoperative plasma analyses were interpreted within the context of standard-of-care radiological surveillance and administration of cytotoxic adjuvant therapy. Landmark analyses of plasma samples collected within 120 days after surgery revealed ctDNA detection in 25% of patients, including 49% of all patients who experienced clinical relapse; 3 to 6 monthly ctDNA surveillance identified impending disease relapse in an additional 20% of landmark-negative patients. We developed a bioinformatic tool (ECLIPSE) for non-invasive tracking of subclonal architecture at low ctDNA levels. ECLIPSE identified patients with polyclonal metastatic dissemination, which was associated with a poor clinical outcome. By measuring subclone cancer cell fractions in preoperative plasma, we found that subclones seeding future metastases were significantly more expanded compared with non-metastatic subclones. Our findings will support (neo)adjuvant trial advances and provide insights into the process of metastatic dissemination using low-ctDNA-level liquid biopsy