ALK and cancer: More generally, when interrogating the whole exome of the putative GBM CTC clusters, we found that they were carrying at total of 116 variants (possibly both driver and passenger mutations) comprised in a total of 58 cancer-associated genes (i.e., genes that were reported in the COSMIC database and whose corresponding substitutions were leading to either structural variants, premature STOP codon, or missense variants) including APC, XPO1, TFRC, JAK2, BRCA2, ERBB4 and ALK, in addition to the GBM-associated genes ATM, PMS2 and POLE (Supplementary Fig. 6c and Suppl.