Transcription profiling by array of human NSCLC U1810 residual clones 9 days after a one-hour pulse treatment with cisplatin

Background: The platinum compounds cisplatin and carboplatin are the mainstay of chemotherapy for lung cancer; however, treatment failure remains a critical issue since about 60% of all non-small cell lung cancer (NSCLC) patients display intrinsic platinum resistance. Methods: We analyzed global gene expression profiles in NSCLC clones surviving a pulse treatment with cisplatin by microarray and mapped deregulated signaling networks in silico by Ingenuity Pathway Analysis (IPA). Results: Cisplatin-surviving NSCLC clones were demonstrated to have heterogeneous gene expression patterns both in terms of the number and the identity of the altered genes. Genes involved in Wnt signaling pathway (DKK1), DNA repair machinery (XRCC2) and cell-cell/ cell-matrix interaction (FMN1 and LGALS9) were among the top deregulated genes by microarray and were subsequently validated by q-RT-PCR. We focused on DKK1, which was previously reported to be overexpressed in NSCLC. IPA network analysis revealed coordinate up-regulation of several DKK1 transcriptional regulators (TCF4, EZH2, DNAJB6 and HDAC2) in cisplatin-surviving clones. Knockdown of DKK1 by siRNA sensitized untreated NSCLC cells to cisplatin, illustrating a putative role of DKK1 in intrinsic platinum resistance. Conclusions: Gene expression analysis identified DKK1 as a putative cisplatin resistance marker and a potential novel therapeutic target to overcome platinum resistance in NSCLC. U1810 cells were sparsely seeded for clonogenic survival assay in three separate experiments (replicate 1-3), left untreated or treated with cisplatin for 1 h and then kept for 9 days to assay long-term effects of a single pulse treatment.