Novel human-derived EML4-ALK fusion cell lines identify ribonucleotide reductase RRM2 as a target of activated ALK in NSCLC.

INTRODUCTION: Echinoderm microtubule-associated protein-like 4 (EML4)-Anaplastic Lymphoma Kinase (ALK) rearrangements occur in 3% to 7% of lung adenocarcinomas and are targets for treatment with tyrosine kinase inhibitors (TKIs). Here we have developed three novel EML4-ALK-positive patient-derived Non-Small-Cell-Lung-Cancer (NSCLC) cancer cell lines, CUTO8 (variant 1), CUTO9 (variant 1) and CUTO29 (variant 3) and included a fourth ALK-positive cell line YU1077 (variant 3) to study ALK-positive signaling and responses. Variants 1 and 3 are the most common EML4-ALK variants expressed in ALK-positive NSCLC, and currently cell lines representing these EML4-ALK variants are limited. MATERIALS AND METHODS: Resazurin assay was performed to evaluate cell viability. Protein levels were determined using western blotting. RNA sequencing was performed in all four cell lines to identify differentially expressed genes. Whole-genome sequencing was performed to determine the presence of EML4-ALK fusion and ALK tyrosine kinase inhibitor resistance mutations. RESULTS: In this study, we have confirmed expression of the corresponding ALK fusion protein and assessed their sensitivity to a range of ALK tyrosine kinase inhibitors. These patient derived cell lines exhibit differential sensitivity to lorlatinib, brigatinib and alectinib, with EML4-ALK variant 3 containing cell lines exhibiting increased sensitivity to lorlatinib and brigatinib as compared to alectinib. These cell lines were further characterized by whole genome sequencing and RNA-seq analysis that identified the ribonucleotide reductase regulatory subunit 2 (RRM2) as a downstream and potential therapeutic target in ALK-positive NSCLC. CONCLUSION: We provide a characterization of four novel EML4-ALK-positive NSCLC cell lines, highlighting genomic heterogeneity and differential responses to ALK TKI treatment. The RNA-Seq characterization of ALK-positive NSCLC CUTO8, CUTO9, CUTO29 and YU1077 cell lines reported here, has been compiled in an interactive ShinyApp resource for public data exploration (https://ccgg.ugent.be/shiny/nsclc_rrm2_2022/).

Comparative genetic study of intratumoral heterogenous MYCN amplified neuroblastoma versus aggressive genetic profile neuroblastic tumors.

Intratumoral heterogeneous MYCN amplification (hetMNA) is an unusual event in neuroblastoma with unascertained biological and clinical implications. Diagnosis is based on the detection of MYCN amplification surrounded by non-amplified tumor cells by fluorescence in situ hybridization (FISH). To better define the genetic features of hetMNA tumors, we studied the Spanish cohort of neuroblastic tumors by FISH and single nucleotide polymorphism arrays. We compared hetMNA tumors with homogeneous MNA (homMNA) and nonMNA tumors with 11q deletion (nonMNA w11q-). Of 1091 primary tumors, 28 were hetMNA by FISH. Intratumoral heterogeneity of 1p, 2p, 11q and 17q was closely associated with hetMNA tumors when analyzing different pieces for each case. For chromosome 2, 16 cases showed 2p intact, 4 focal gain at 2p24.3 and 8 MNA. The lengths of the smallest regions of overlap (SROs) for 2p gains and 1p deletions were between the SRO lengths observed in homMNA and nonMNA w11q- tumors. Co-occurrence of 11q- and +17q was frequently found with the largest SROs for both aberrations. The evidence for and frequency of different genetic subpopulations representing a hallmark of the hetMNA subgroup of NB indicates, on one hand, the presence of a considerable genetic instability with different SRO of either gains and losses compared with those of the other NB groups and highlights and, on the other hand, the need for multiple sampling from distant and macroscopically and microscopically distinct tumor areas. Narrowing down the different SRO for both deletions and gains in NB groups would be crucial to pinpointing the candidate gene(s) and the critical gene dosage with prognostic and therapeutic significance. This complexity of segmental chromosomal aberration patterns reinforces the necessity for a larger cohort study using FISH and pangenomic techniques to develop a suitable therapeutic strategy for these patients.

Anaplastic Lymphoma Kinase (ALK) regulates initiation of transcription of MYCN in neuroblastoma cells.

Neuroblastoma is a neural crest-derived embryonal tumour of the postganglionic sympathetic nervous system and a disease with several different chromosomal gains and losses, which include MYCN-amplified neuroblastoma on chromosome 2, deletions of parts of the chromosomes 1p and 11q, gain of parts of 17q and triploidy. Recently, activating mutations of the ALK (Anaplastic Lymphoma Kinase) RTK (Receptor Tyrosine Kinase) gene have been described in neuroblastoma. A meta-analysis of neuroblastoma cases revealed that ALK mutations (49 of 709 cases) in relation to genomic subtype were most frequently observed in MYCN amplified tumours (8.9%), correlating with a poor clinical outcome. MYCN proteins target proliferation and apoptotic pathways, and have an important role in the progression of neuroblastoma. Here, we show that both wild-type and gain-of-function mutants in ALK are able to stimulate transcription at the MYCN promoter and initiate mRNA transcription of the MYCN gene in both neuronal and neuroblastoma cell lines. Further, this stimulation of MYCN gene transcription and de novo MYCN protein expression is abrogated by specific ALK inhibitors, such as crizotinib (PF-2341066), NVP-TAE684, and by small interfering RNA to ALK resulting in a decrease in proliferation rate. Finally, co-transfection of ALK gain-of-function mutations together with MYCN leads to an increase in transformation potential. Taken together, our results indicate that ALK signalling regulates initiation of transcription of the MYCN gene providing a possible explanation for the poor clinical outcome observed when MYCN is amplified together with activated ALK.