Recovery of cellular E-cadherin precedes replenishment of estrogen receptor and estrogen-dependent proliferation of breast cancer cells rescued from a death stimulus.
Loss of estrogen-responsiveness and impaired E-cadherin expression/function has been linked to increased metastatic potential of breast cancer cells. In this study, we report that proliferation of breast cancer cells can resume following removal of a toxic stimulus causing severe impairment of cell adhesion and estrogen responsiveness. This type of response was induced by okadaic acid (OA) in MCF-7 cells, and was accompanied by an almost complete block of DNA synthesis, loss of cell-cell contact and cell detachment from culture dishes, loss of estrogen receptor (ER), progesterone receptor (PR) and E-cadherin, whereas only a weak, if any, inhibition of protein synthesis could be observed. These responses were detected in MCF-7 cells after a 1-day treatment with 50 nM OA, and could be reversed if OA-treated cells were recovered in a culture medium devoid of the toxin, so that rescued cells resumed growth 8-12 days after replating. By pulse-chase experiments, we found that protein synthesis was not significantly affected in rescued cells, whose DNA synthesis, instead, was almost completely blocked during the first days of MCF-7 cell rescue from OA treatment. We also analyzed E-cadherin, mitogen activated protein kinase isoforms ERK1 and ERK2, Bcl-2 and BAX proteins during the rescue of MCF-7 cells from OA-induced cell death, and found that their expression followed temporally defined patterns. Cellular levels of E-cadherin returned to control levels within the first days of the rescue, followed by ER, ERK1, and ERK2, and finally by Bcl-2 and BAX proteins. Under our experimental conditions, restoration of cell adhesion did not require a functional ER system, but recovery of a normal ER pool accompanied resumption of estrogen-dependent proliferation of OA-treated MCF-7 cells.
Malaguti
Claudia
C
Dipartimento di Scienze Biomediche, Sezione di Chimica Biologica, Università di Modena e Reggio Emilia, Modena, Italy.
Rossini
Gian Paolo
GP
D001943:Breast Neoplasms / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D004967:Estrogens / Q000378:metabolism*; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019319:Okadaic Acid / Q000494:pharmacology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism; D014407:Tumor Cells, Cultured; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; D015820:Cadherins; D004967:Estrogens; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D051028:bcl-2-Associated X Protein; D019319:Okadaic Acid; D004247:DNA; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases