Abstract 4897: Genetic variants and expression of AEG-1 in relation to clinical outcome and radiotherapy response in colorectal cancer patients and cell lines

Abstract

Abstract Background: Colorectal cancer (CRC) is the third most common cancer in men and the second in woman worldwide. The therapy of CRC has been critically improved during the past two decades, but the treatment response varies significantly between different treatments and patients. Therefore it is of need to search for biomarkers for more suitable prognosis and treatment. The aim of this study was to investigate genetic variants of the astrocyte elevated gene-1 (AEG-1), its expression in CRC patient samples and colon cancer cell lines and the potential correlation to clinicopathological variables and treatment response. Materials and Methods: We analysed genetic variants and the mRNA and protein expression of AEG-1 in 593 CRC patient samples by direct Sanger sequencing, qPCR and immunohistochemistry. Of the patients, 158 rectal cancer patients were enrolled in the Swedish clinical trial of preoperative radiotherapy (RT). AEG-1 expression in response to γ-irradiation was analysed by Western blot in 5 colon cancer cell lines. We inhibited the AEG-1 expression by siRNA in the cell lines, and their survival was analysed after γ-irradiation. Results: By direct sequencing we found 29 variants, of which 12 were novel. Six of the variants were exonic and 23 intronic. The variant c.1353G>A, rs2331652 was found only in 4 samples and the variant c.1679-6 T>C in only one sample. In the cell lines KM12C, KM12SM and KM12L4a we found a deletion in exon 4 (c.595_598delAGAG). AEG-1 mRNA and protein expression revealed a significant increased AEG-1 expression in the primary tumors and metastases compared to the normal mucosa in all patient cohorts (p<0.006) and on the mRNA level a higher expression in tumors located in the rectum compared to tumors in the colon (p=0.047). In the rectal cancer patients from the Swedish trail of preoperative RT, a high AEG-1 expression correlated with a higher risk of distant recurrence and disease free survival (p=0.001 respectively) independently of the tumor stage, only in patients receiving preoperative RT. AEG-1 knock-down in the radioresistant cell lines KM12L4a, SW480 and SW620 resulted in reduction of the survival after radiation, but not in the radiosensitive cell lines KM12C and HCT116. The AEG-1 expression was up-regulated shortly after 2 Gy γ-radiation in KM12C, KM12L4a and SW480, but not in SW620 and HCT116. Conclusion: We found several novel AEG-1 variants. The AEG-1 expression at the mRNA and/or protein level was up-regulated in the primary tumour and metastases compared to the normal mucosa. Furthermore we showed for the first time that the AEG-1 expression is an independent prognostic factor for distant recurrence and disease-free survival in rectal cancer patients after treatment with preoperative RT. The cell line studies suggest AEG-1 as a promising radiosensitizing target for rectal cancer. Citation Format: Sebastian Gnosa, Veronika Patcha Brodin, Ivana Ticha, Gunnar Adell, Gunnar Arbman, Hong Zhang, Xiao-Feng Sun. Genetic variants and expression of AEG-1 in relation to clinical outcome and radiotherapy response in colorectal cancer patients and cell lines. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4897. doi:10.1158/1538-7445.AM2014-4897