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Abstract 2490: Silencing of TCF7L2 sensitizes Wnt/β-catenin signaling-dependent colorectal cancer cells to radiation
- Source :
- Cancer Research. 71:2490-2490
- Publication Year :
- 2011
- Publisher :
- American Association for Cancer Research (AACR), 2011.
-
Abstract
- Background: The clinical response of locally advanced rectal cancers to preoperative chemoradiotherapy is very heterogeneous. We recently profiled a series of responsive and resistant rectal carcinomas using gene expression microarrays and identified TCF7L2, the main downstream effector of the Wnt/β-catenin pathway, as over-expressed in the resistant tumors. The aim of this study was to explore the relevance of TCF7L2 for resistance to radiation and to study the underlining mechanisms. Methods: We transfected three microsatellite-stable colorectal cancer cell lines (SW837, SW480 and HT-29) with two different shRNA-vectors targeting TCF7L2 and a non-silencing. Next, we established single cell clone (SCC) populations, and after confirming the reduction of TCF7L2 protein levels by Western blotting, we irradiated the SCCs at 0, 1, 2, 4, 6 and 8 Gy and calculated survival fractions. To gain functional insight, we chose SW837 and HT-29 for further experiments. Using γH2AX staining we evaluated DNA double strand repair after irradiation at 2 Gy and analyzed cell cycle changes before and after radiation. Furthermore, we studied Wnt/β-catenin pathway activity using the TOPFLASH/FOPFLASH reporter assay. Results: RNAi-mediated silencing of TCF7L2 led to a pronounced reduction in TCF7L2 protein levels. In radiation experiments we observed a highly significant radiosensitization in SW837 and SW480 SCCs, whereas no effect was observed in HT-29 SCCs. Well-fitting, we observed significantly more γH2AX foci 24h after radiation in SW837 SCCs compared to HT-29 SCCs, pointing to impaired DNA damage repair in the SCCs from SW837. Furthermore, in SW837 SCCs but not in HT-29 SCCs we noticed a change in the cell cycle distribution towards radiosensitive cell cycle phases before radiation and compromised cell cycle control after radiation. Finally, using the TOPFLASH/FOPFLASH reporter assay we found SW837 wild-type cells to show high Wnt/β-catenin pathway activity, while HT-29 wild-type cells only showed very low activity. Conclusion: TCF7L2 was found to be over-expressed in resistant rectal carcinomas, and its RNAi-mediated silencing caused a significant radiosensitization, mediated by DNA damage repair deficiencies and impaired cell cycle control. Interestingly, radiosensitization effetcts were only observed in cell lines showing Wnt/β-catenin pathway activity. Thus, we have uncovered a novel role of Wnt/β-catenin signaling for mediating resistance to multimodal cancer therapy. Moreover, these data suggest that TCF7L2 is a potential molecular target for sensitizing Wnt/β-catenin-dependent tumor cells to radiation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2490. doi:10.1158/1538-7445.AM2011-2490
- Subjects :
- 0303 health sciences
Cancer Research
Reporter gene
Colorectal cancer
Wnt signaling pathway
Cancer
Transfection
Cell cycle
Biology
medicine.disease
3. Good health
03 medical and health sciences
0302 clinical medicine
Oncology
Cell culture
030220 oncology & carcinogenesis
Immunology
medicine
Cancer research
Gene silencing
030304 developmental biology
Subjects
Details
- ISSN :
- 15387445 and 00085472
- Volume :
- 71
- Database :
- OpenAIRE
- Journal :
- Cancer Research
- Accession number :
- edsair.doi...........a6c91984582782c0d4d5757d43979c36