Abstract 131: ALK oncogene regulates epithelial-mesenchymal transition (EMT) in ALK-rearranged non-small cell lung carcinoma through repression of the epithelial splicing regulatory proteins 1 and 2 (ESRP1 and ESRP2)

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA A subset of Non-Small Cell Lung Carcinoma (NSCLC) carries chromosomal rearrangements involving the Anaplastic Lymphoma Kinase (ALK) gene. More frequently ALK is juxtaposed to the echinoderm microtubule-associated protein-like 4 (EML4) gene on chromosome 2 and generates a constitutively active EML4-ALK fusion protein that triggers downstream oncogenic signals leading to increased cell proliferation and survival. The majority of ALK-rearranged NSCLC presents a peculiar histology characterized by a solid signet-ring cell and a mucinous cribriform pattern that is frequently associated with a metastatic phenotype. As the signet ring phenotype and metastasis are associated with epithelial-mesenchymal transition (EMT), a cellular reprogramming often activated in cancer cells during invasion and metastasis, we investigated whether ALK induces EMT in NSCLC. We performed RNA sequencing analysis on human ALK-rearranged NSCLC cell lines treated with ALK inhibitors or where EML4-ALK was knocked-down by shRNA. We found that EML-ALK regulated several genes related to EMT. In particular, the epithelial splicing regulatory proteins 1 and 2 (ESRP1 and ESRP2), key regulators of a splicing switch during EMT, were repressed in ALK-rearranged NSCLC cells and their repression was dependent on ALK activity. In keeping with these observations, H2228 and DFCI032 cells displayed a mesenchymal phenotype with almost complete suppression of the epithelial marker, E-cadherin, and a strong expression of the mesenchymal markers, vimentin and N-cadherin. In H2228 and DFCI032 cells, both E-cadherin suppression and vimentin up-regulation were dependent upon EML-ALK kinase activity because treatment with ALK inhibitors (TAE684 and crizotinib) or ALK knock-down reverted the phenotype of H2228 and DFCI032 from mesenchymal to epithelial and decreased their invasive potential. We excluded the involvement in EMT of ALK-rearranged NSCLC of other RTKs, such as EGFR or MET, because their inhibition did not have any effect on E-cadherin and vimentin expression. In ALK-rearranged NSCLC, the regulation of E-cadherin suppression was mainly transcriptional whereas vimentin regulation was post-transcriptional for both cell lines. Overexpression of ESRP1 led to up-regulation of E-cadherin, whereas ESRP1 knock-down impaired the reversion to an epithelial phenotype associated to inhibition of ALK activity. In conclusion, we showed that oncogenic ALK regulates EMT in NSCLC through ESRP repression. These findings could have implications for the biology of ALK-rearranged NSCLC in terms of metastatic potential and resistance to therapy. Citation Format: Claudia Voena, Lydia Varesio, Liye Zhang, Matteo Menotti, Teresa Poggio, Filomena Di Giacomo, Elena Panizza, Cristina Mastini, Mara Compagno, Stefano Monti, Roberto Chiarle. ALK oncogene regulates epithelial-mesenchymal transition (EMT) in ALK-rearranged non-small cell lung carcinoma through repression of the epithelial splicing regulatory proteins 1 and 2 (ESRP1 and ESRP2). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 131. doi:10.1158/1538-7445.AM2015-131