Abstract 1214: TP53 affects SOX2 copy number alterations and expression in non-small cell lung cancer

Abstract

Abstract Background: Amplifications of the transcription factor, SRY (sex determining region Y)-box 2 (SOX2), are common in non-small cell lung cancer (NSCLC). SOX2-signaling is important in maintaining the stem cell-like phenotype of cancer cells and contributes to the pathogenesis of lung cancer. TP53 is recognized as a critical regulator of stem cell pluripotency, and it is known that TP53 represses many stem cell associated genes following DNA damage. We hypothesized that SOX2 copy number alterations in lung tumors could be correlated to mutational status of TP53 gene in tumors and that TP53 played a role in regulation of SOX2 gene expression. Material and Methods: Early-stage lung cancer cases (n = 258) of Norwegian Caucasians origin were recruited when admitted to Haukeland University Hospital in Bergen, Norway between 1986 and 1994. Samples of adjacent histologically non-tumorous lung tissue were collected in the lobectomi specimens at the time of surgery. Tumor histology was confirmed by an experienced pathologist and samples containing >80% of tumor cells were analyzed in this study. After resection tumor and non-tumorous tissues were snap-frozen in liquid nitrogen and kept at -80oC until further processing. All subjects gave written consent, and the study was approved by the regional ethical committee in accordance with the Helsinki Declaration. SOX2 copy number alterations were evaluated by quantitative RT- PCR using SYBR Green I Technology. The TP53 and SOX2 expression levels were assessed by q-PCR in the tumors where mRNA was available. Furthermore, to understand mechanisms, TP53 and SOX2 genes were knocked down by siRNA in the A427 human lung adenocarcinoma cell line. Additionally, some miRNAs were also analyzed by q-PCR. TP53 mutations in tumors were analyzed by sequencing and PAH-DNA adduct levels were determined in non-tumorous lung tissue by 382P-postlabelling. Results: SOX2 copy number alterations were more frequent in tumor tissues (34%) than in the adjacent non-tumorous tissues (3%) and TP53 mutations were associated with an increased risk of acquiring a SOX2 copy number alteration (OR = 2.08, 95% CI: 1.14-3.79, p = 0.017). SOX2 and TP53 expressions were strongly correlated in lung tumors and reduction in TP53 decreased SOX2 expression in lung adenocarcinoma cells. TP53 knockdown also reduced the miRNA hsa-miR-145, which has previously been shown to regulate SOX2 expression. We propose that SOX2 may be an important target of TP53 signaling in lung cancer and that hsa-miR-145-5p may be one potential driver miRNA involved in this regulation requiring further studies on the mechanisms behind the TP53-induced regulation of SOX2 expression and the possible importance of hsa-miR-145 in lung cancer. Citation Format: Johanna Samulin-Erdem, Vidar Skaug, Per Bakke, Amund Gulsvik, Aage Haugen, Shanbeh Zienolddiny. TP53 affects SOX2 copy number alterations and expression in non-small cell lung cancer. [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 1214. doi:10.1158/1538-7445.AM2015-1214