PURPOSE: Colon cancer is the second leading cause of cancer death worldwide. Elevated expression of insulin-like growth factor-I receptor (IGF-IR) is a frequent genetic abnormality seen in this malignancy. For a better understanding of its role in maintaining the malignant phenotype, we used RNA interference (RNAi) directed against IGF-IR in our study. The aim of this study was to examine the anti-proliferation and chemosensitization effects elicited by a decrease in the transcription and protein levels of IGF-IR by RNAi in SW480 colon cancer cells. METHODS: A plasmid-based polymerase III promoter system was used to deliver and express short interfering RNA (siRNA) targeting IGF-IR to reduce its expression in SW480 cells. Western blot analysis was used to measure the protein level of IGF-IR. We assessed the effects of IGF-IR silencing on cancer cell growth by a cell growth curve. The effect of the 5-fluorouracil (5-FU)-induced cell death by knockdown of IGF-IR was also investigated by methyl thiazolyl tetrazolium assay. RESULTS: Transfection of siRNA targeting IGF-IR was shown to reduce IGF-IR messenger RNA levels by 95%. Western blotting detected a similar inhibition of IGF-IR protein levels in those cells. The cells transfected with PKD-short hairpin RNA-IGF-IR-V2 significantly decreased cell growth and rendered cells more sensitive to chemotherapy. The highest proliferation inhibitory and chemosensitization ratios were 53 +/- 2% and 1.78, respectively. CONCLUSION: This study indicates that downregulation of IGF-IR results in significant inhibition of tumor growth in vitro. It also provides a promising strategy to chemotherapy efficacy in human tumors and forming a basis for future in vivo trials.
PURPOSE:Colon cancer is the second leading cause of cancer death worldwide. Elevated expression of insulin-like growth factor-I receptor (IGF-IR) is a frequent genetic abnormality seen in this malignancy. For a better understanding of its role in maintaining the malignant phenotype, we used RNA interference (RNAi) directed against IGF-IR in our study. The aim of this study was to examine the anti-proliferation and chemosensitization effects elicited by a decrease in the transcription and protein levels of IGF-IR by RNAi in SW480 colon cancer cells. METHODS: A plasmid-based polymerase III promoter system was used to deliver and express short interfering RNA (siRNA) targeting IGF-IR to reduce its expression in SW480 cells. Western blot analysis was used to measure the protein level of IGF-IR. We assessed the effects of IGF-IR silencing on cancer cell growth by a cell growth curve. The effect of the 5-fluorouracil (5-FU)-induced cell death by knockdown of IGF-IR was also investigated by methyl thiazolyl tetrazolium assay. RESULTS: Transfection of siRNA targeting IGF-IR was shown to reduce IGF-IR messenger RNA levels by 95%. Western blotting detected a similar inhibition of IGF-IR protein levels in those cells. The cells transfected with PKD-short hairpin RNA-IGF-IR-V2 significantly decreased cell growth and rendered cells more sensitive to chemotherapy. The highest proliferation inhibitory and chemosensitization ratios were 53 +/- 2% and 1.78, respectively. CONCLUSION: This study indicates that downregulation of IGF-IR results in significant inhibition of tumor growth in vitro. It also provides a promising strategy to chemotherapy efficacy in humantumors and forming a basis for future in vivo trials.
Authors: Guangchao Sui; Christina Soohoo; El Bachir Affar; Frédérique Gay; Yujiang Shi; William C Forrester; Yang Shi Journal: Proc Natl Acad Sci U S A Date: 2002-04-16 Impact factor: 11.205
Authors: A V Gudkov; C R Zelnick; A R Kazarov; R Thimmapaya; D P Suttle; W T Beck; I B Roninson Journal: Proc Natl Acad Sci U S A Date: 1993-04-15 Impact factor: 11.205