ORIGINAL ARTICLE

Treatment of murine breast cancer cells with antisense RNA to the type I insulin-like growth factor receptor decreases the level of plasminogen activator transcripts, inhibits cell growth in vitro, and reduces tumorigenesis in vivo

C L Chernicky, H Tan, L Yi, J R Loret de Mola, J Ilan

Department of Reproductive Biology, Case Western Reserve University School of Medicine, Cleveland, OH 44106–4943, USA

Correspondence to:
Correspondence to:
Dr J Ilan, Department of Reproductive Biology, Case Western Reserve University, University MacDonald Women's Hospital, 11100 Euclid Avenue, Cleveland, OH 44106–4943, USA;
cheryl.chernicky{at}uhhs.com

Aims: To establish that cells from the murine mammary carcinoma cell line, EMT6, express type I insulin-like growth factor receptor (IGF-IR), tissue-type plasminogen activator (tPA), and urokinase-type plasminogen activator (uPA). To investigate the role of IGF-IR in growth, transformation, and tumorigenesis in addition to its relation to tPA and uPA in EMT6 cells. To assess the suitability of the EMT6/syngeneic mouse model for studying the role of IGF-IR in tumorigenesis.

Methods: The presence of transcripts for IGF-IR, tPA, and uPA was determined by northern blot analysis using poly (A⁺) RNA derived from EMT6 cells transfected with an antisense IGF-IR construct or a construct lacking the antisense IGF-IR insert. Flow cytometry was used to measure IGF-IR protein. Assays were performed to determine cell proliferation, transformation, and the tumorigenicity of antisense IGF-IR transfected EMT6 cells and control transfected EMT6 cells.

Results: There was strong expression of IGF-IR, tPA, and uPA in EMT6 cells. EMT6 cells from clones carrying antisense IGF-IR displayed a significant decrease in cell proliferation and lost the ability to form colonies in soft agar. A decrease in tumour size occurred when cells carrying the antisense IGF-IR were injected into syngeneic mice. Reduced expression of tPA and uPA was seen in EMT6 cells carrying the antisense IGF-IR construct.

Conclusions: The IGF-IR plays a role in the progression, transformation, and tumorigenesis of EMT6 murine mammary carcinoma cells. The suppression of IGF-IR mRNA in EMT6 cells decreases tPA and uPA expression. EMT6 cells and the syngeneic mouse provide a suitable model for studying the role of IGF-IR in breast tumour progression.

Keywords: cell transfection; EMT6 cells; animal models; tissue-type plasminogen activator; urokinase-type plasminogen activator

Abbreviations: CMV, cytomegalovirus; FBS, fetal bovine serum; IGF-IR, type I insulin-like growth factor receptor; MEM, minimum essential medium ; PBS, phosphate buffered saline; PE, phycoerythrin; SDS, sodium dodecyl sulfate; SSC, saline sodium citrate; tPA, tissue-type plasminogen activator; uPA, urokinase-type plasminogen activator

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