FIG 2.

Genetic alterations of ALK in patients with HR-NB. (A) Copy-number profile of case 536. Genomic coamplification of MYCN and ALK is observed on chromosome 2, encompassing the regions between position 15,440,477 and 16,822,999 and between 29,113,790 and 30,309,749 bp (human genome assembly hg19; UCSC Genome Browser Home³⁸). (B) Frequency distribution of mutated ALK alleles at the studied chromosome regions, encompassing the AA positions F1174, L1190, L1196, R1245, D1270, G1272, M1273, A1274, R1275, and Y1278 detected, in 762 samples. ALK mutations involved the common mutational hotspots (F1174, F1245, and R1275) in 12.5% (97 out of 772) of cases, at a clonal level (MAF 20%-93%) in 72 cases, and at a subclonal level (MAF < 20%) in 25 cases. At the F1174 hotspot (chr2: 29,443,695-29,443,697), alterations were observed in 44 cases: 42 cases harbored a mutation leading to the AA change F1174L, one case with F1174I, and one case with F1174S, with MAFs ranging from 0.12% to 78%. At the R1275 hotspot (chr2: 29,432,849-29,430,139), mutations were detected in 43 cases: 38 cases harbored a mutation leading to the AA change R1275Q and five cases with R1275L, with the MAFs ranging from 0.2% to 93%. Ten cases showed ALK mutations at the F1245 hotspot (chr2: 29,436,858-29,436,860) within exon 24. Three samples showed the F1245L mutation, three cases carried the F1245C mutation, three showed the F1245I mutation, and one showed mutation F1245V mutation (Fig 1 and Appendix Table A1). Other ALK mutations were detected at residues I1170, L1190 (two cases), L1196, D1270, G1272, M1273, A1274, and Y1278 within the explored regions, leading to a nonsynonymous AA change with a predicted functional impact. All these mutations were clonal (MAF > 20%) except for M1273I (MAF 0.2%) and I1170 (MAF 2.8%). AA, amino acid; aCGH, array comparative genomic hybridization; bp, base pair; HR-NB, high-risk neuroblastoma; MAF, mutated allele fraction; UCSC, University of California, Santa Cruz.