Abstract B19: Fetal lung adenocarcinoma: Characterization of primary cell culture and in vitro drug response

Abstract

Abstract Purpose: Fetal lung adenocarcinoma (FLAC) is an extremely rare subtype of pulmonary adenocarcinoma estimated to be the 0.5% of all lung cancers. Therefore a standardized model of FLAC primary cell culture and evidence-based treatment guidelines are not available. The aim of this study is to characterize FLAC primary cell culture, to evaluate the biological features of this uncommon tumor and the in vitro drug response. Methods: FLAC specimen was obtained from a 59-years-old female patient, cultured in vitro with DMEM-F12 medium supplemented with 5% FBS and maintained in culture for more than 6 passages. Primary cells from a lung adenocarcinoma specimen were as well cultured and used as control for all the in vitro experiments. Immunohistochemistry for β-catenin, TTF-1, Ki67, cKit, MDM2, p53, S-100, EGFR, E-cadherin, cytokeratin 7 and 8/18 was performed on paraffin-fixed specimen. Immunofluorescence on cells in culture was assessed for MDM2, p53, CD133. Specimen and cells in culture were analyzed by real time PCR for oncogenic mutations (KRAS, EGFR) and for a stem cells gene panel. In vitro tumorigenicity was tested by plating efficency and soft agar colony formation assays. Cell proliferation was determined and a cell viability test was performed after treatment of FLAC cells with tyrosine kinase inhibitors (erlotinib and gefitinib), temozolomide (TMZ), cisplatin, gemcitabine and cysplatin+gemcitabine by MTS assay. Results: A primary cell culture of human FLAC was characterized and standardized. FLAC histotype was confirmed by immunohistochemistry. Immunofluorescence showed a positivity for MDM2, but not for p53 and CD133. By molecular analysis, DNA from both specimen and cells in culture was found to harbor epidermal growth factor receptor (EGFR) kinase domain non-sense mutation in exon 20 and no mutations in the K-ras gene. Primary FLAC cells showed a colony formation activity and the soft agar assay revealed an anchorage-indipendent growth. At 48 hours FLAC cells proliferation was inhibited of 56% and 41% by erlotinib and gefitinib respectively, with an IC50 value of 10 μM, compared with the control proliferation (lung adenocarcinoma cells) inhibited of 25% and 60% by erlotinib and gefitinib respectively (p=0,17; p=0,005). However, FLAC cell viability at 48 hours after being treated with cisplatin 10 μM was 3%, compared with the control viability that was 16% (p=0,007). Conclusion: This well-characterized FLAC primary cell culture provide a unique model for future studies in lung cancer biology and drug response. Although chemosensitivity to cisplatin was determined, erlotinib and gefitinib were effective against FLAC cells and appear to represent a novel targeting approach for the treatment of this rare tumor.