The effect of siRNA-Egr-1 and camptothecin on growth and chemosensitivity of breast cancer cell lines.
We have examined the effects of a siRNA targeting the Egr-1, alone or in combination with the breast cancer therapeutic camptothecin (Cpt), in suppressing breast cancer cell survival and anchorage-independent growth in the breast cancer cell lines SK-BR3 and MCF-7. In mammary and lung tumors, as well as most normal tissues, Egr-1 expression is low, suggesting a possible relation between the low levels of Egr-1 and the development of mammary neoplasias. However, analyses of the expression of Egr-1 in breast carcinoma cells, SK-BR3 and MCF-7 demonstrated a relatively high expression of the endogenous Egr-1 in these cells. To investigate the effect of the blocking of the endogenous Egr-1 in breast cancer cells, we used small interfering RNA (siRNA) against Egr-1 alone or in combination with Cpt, and expected that the cell sensitivity to chemotherapeutic drug would increase, when blocked with the Egr-1 gene and treated with Cpt. Thus, we performed in vitro experiment to clarify the effect of Egr-1 on tumor cell lines growth. We made control and siRNA-Egr-1 using vector plasmids and then transfected SK-BR3 and MCF-7 cells. After treating the cells with siRNA-Egr-1, the cell lines were assayed with Cpt to confirm the effect of Egr-1 siRNA using the cell expression of mRNA and protein, proliferation assay and anchorage activity with soft agar. Human SK-BR3 and MCF-7 breast carcinoma cell growth and capacity of anchorage transfected with siRNA-Egr-1 or treated with cpt was slower than that of the control group. This effect was increased when the cells were given simultaneously siRNA and camptothecin. The results strongly suggest that siRNA-Egr-1 alone or in combination with camptothecin could be a potent antineoplastic agent in suppressing the growth of breast tumor despite the known role of Egr-1 as a tumor-suppressor in several other types of human cancers.
Parra
Eduardo
E
Biomedical Experimental Laboratory, Department of Biology, Sciences Faculty, University of Tarapaca, Arica, Chile. eparra@uta.cl
Ferreira
Jorge
J
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D002166:Camptothecin / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics*; D051766:Early Growth Response Protein 1 / Q000037:antagonists & inhibitors / Q000235:genetics*; D005260:Female; D006801:Humans; D034622:RNA Interference; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
D000972:Antineoplastic Agents, Phytogenic; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D034741:RNA, Small Interfering; D002166:Camptothecin