Down-regulation of Cx43 by retroviral delivery of small interfering RNA promotes an aggressive breast cancer cell phenotype

• Published in: Cancer research (Chicago, Ill.) Vol. 65; no. 7; pp. 2705 - 2711
• Main Authors: QING SHAO, HONGLING WANG, MCLACHLAN, Elizabeth, VEITCH, Gregory I. L, LAIRD, Dale W
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 01.04.2005
• Subjects: Animals; Antineoplastic agents; Biological and medical sciences; Breast Neoplasms - blood supply; Breast Neoplasms - genetics; Breast Neoplasms - pathology; Cell Growth Processes - genetics; Cell Line, Tumor; Cell Movement - genetics; Connexin 43 - antagonists & inhibitors; Connexin 43 - biosynthesis; Connexin 43 - genetics; Down-Regulation; Gene Expression Regulation, Neoplastic; Genetic Vectors - genetics; Humans; Medical sciences; Neovascularization, Pathologic - genetics; Neovascularization, Pathologic - pathology; Pharmacology. Drug treatments; Rats; Retroviridae - genetics; RNA, Small Interfering - administration & dosage; RNA, Small Interfering - genetics; Thrombospondin 1 - biosynthesis; Thrombospondin 1 - genetics; Transfection; Vascular Endothelial Growth Factor A - biosynthesis; Vascular Endothelial Growth Factor A - genetics; Virus; Mammary gland diseases; Phenotype; Regulation(control); Retroviridae; Small Interference RNA; Breast cancer; Malignant tumor; Gene therapy; Tumor cell; High malignancy
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.can-04-2367

Connexins are gap junction proteins that assemble into channels that mediate direct intercellular communication. Connexins are well-documented tumor suppressors and are thought to regulate both cell growth and differentiation. As previously reported, most human breast tumors and cell lines down-regulate gap junctions or have defective gap junctional intercellular communication. Furthermore, overexpression of connexins in breast cancer cells inhibits tumor growth in vivo. In this study, we hypothesize that controlled Cx43 down-regulation would induce breast tumor cells to acquire a more aggressive phenotype. Here we report that Cx43 was down-regulated in both normal rat kidney (NRK) cells and human breast cancer cell lines (MDA-MB-231 and Hs578T) by transfection with chemically synthesized small interfering RNA (siRNA) or short hairpin RNA generated from a retroviral infection. Furthermore, we show that retroviral delivery and expression of siRNA directed to different coding regions of Cx43 resulted in differential levels of Cx43 silencing and impaired gap junctional intercellular communication. Cx43-silenced Hs578T cells grew faster and were more migratory. Finally, Western blot analysis revealed that down-regulation of Cx43 resulted in decreased expression of thrombospondin-1, an antiangiogenesis molecule, and increased expression of vascular endothelial growth factor. Taken together, these results suggest that Cx43 is required for maintaining cell differentiation and the regulation of molecules important in angiogenesis.