Abstract 4648: Cellular senescence and transformation induced by an oncogenic EML4-ALK fusion gene in normal and immortalized human cells

Background: Chromosomal inversions involving Anaplastic lymphoma kinase (ALK) and Echinoderm Microtubule Associated Protein Like 4 (EML4) generate a fusion protein EML4-ALK with the constitutive ALK kinase activity in non-small cell lung carcinoma (NSCLC). The basic understanding of EML4-ALK remains insufficient due to the lack of functional studies using normal human cells. Material and Method: We investigate the activities of EML4-ALK in mortal and immortalized normal human cells. Results: The expression of EML4-ALK in normal, mortal human fibroblasts caused, through its ALK kinase activity, the early induction of cellular senescence with senescence-associated β-galactosidase activity, upregulation of p16INK4A and p21WAF1, telomere shortening and fusions, and accumulated DNA damage. In contrast, when EML4-ALK was expressed in telomerase reverse transcriptase (hTERT)-immortalized normal human fibroblasts, the cells showed accelerated proliferation and anchorage-independent growth, revealing its transformation activity. No chromosome aberration, no mutation or loss of p53, nor impairment of the p16INK4A response was associated with this transformation, likely reflecting clinical features of EML4-ALK-positive NSCLC. In both mortal and immortalized cells, EML4-ALK induced the phosphorylation of STAT3, which is involved in both cellular senescence and transformation. EML4-ALK was also able to transform hTERT-immortalized human bronchial epithelial cells, a cell type relevant to NSCLC. Conclusions: Our data not only validate that EML4-ALK functions as an oncogene in human cells, but also suggest that telomerase-mediated immortalization manifests the oncogenic activity of EML4-ALK, switching from its senescence-inducing activity. This study also provides the isogenic pairs of human cell lines with and without EML4-ALK as an in vitro model for screening and testing candidate drugs. Citation Format: Akihiko Miyanaga, Izumi Horikawa, Masaru Matsumoto, Takahiro Oike, Jessica Beck, Hiromi Tanaka, Ana I. Robles, Masahiro Seike, Akihiko Gemma, Curtis C. Harris. Cellular senescence and transformation induced by an oncogenic EML4-ALK fusion gene in normal and immortalized human cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4648.