TCDD causes suppression of growth and differentiation of MCF10A, human mammary epithelial cells by interfering with their insulin receptor signaling through c-Src kinase and ERK activation.
One of the proposed mechanisms of carcinogenic action of TCDD (=dioxin) on breast cells is that it causes significant inhibition of proper differentiation of mammary duct epithelial cells and thereby increases the number of terminal end buds, which are susceptible to other carcinogens (Fenton et al., Toxicol Sci 2002;67:63-74; Brown et al., Carcinogenesis 1998; 19:1623-1629; Lamartiniere, J Mammary Gland Biol Neoplasia 2002;7:67-76). To address this topic, we selected MCF10A, a line of immortalized normal human breast epithelial cells as an in vitro model. An initial effort was made to optimize the cultural condition of MCF10A cells to promote the cell differentiation effect of insulin. Under this condition, TCDD clearly antagonized the action of insulin only in the presence of cholera toxin that is known to promote the differentiation of normal human breast epithelial cells. To test the hypothesis that TCDD-induced c-Src kinase activation is casually related to this compound's antagonistic action against insulin, we treated MCF10A cells with two c-Src blocking agents, an anti-Src antisense oligonucleotides blocker and a known specific inhibitor of c-Src kinase, PP-2 and studied the effect of insulin and TCDD on cell proliferation. The results showed that, in cells treated with either of these two c-Src blocking agents, the antagonistic effect of TCDD disappeared. It was also found that agents which specifically block the activation of ERK could also abrogate the action of TCDD to suppress insulin signaling. Together, these results indicate that the mechanism of the antagonistic action of TCDD on insulin signaling is mainly mediated through c-Src signaling through activation of ERK.
Park
Sujin
S
Department of Environmental Toxicology and the Center for Environmental Health Sciences, University of California, Davis, CA 95616, USA.
Mazina
Olga
O
Kitagawa
Akira
A
Wong
Patrick
P
Matsumura
Fumio
F
D001483:Base Sequence; D000081247:CSK Tyrosine-Protein Kinase; D002454:Cell Differentiation / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects*; D002460:Cell Line; D017931:DNA Primers; D004789:Enzyme Activation; D006801:Humans; D042361:Mammary Glands, Human / Q000166:cytology / Q000187:drug effects*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011972:Receptor, Insulin / Q000187:drug effects* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects*; D019061:src-Family Kinases
D017931:DNA Primers; D000072317:Polychlorinated Dibenzodioxins; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human; D020928:Mitogen-Activated Protein Kinases