STAT3, STAT5A AND STAT5B REGULATION IN HC11 MAMMARY EPITHELIUM CELLS

AGUSTINA RODRIGUEZ GRANILLO, JUAN CARLOS BOFFI, LINO BARAÑAO, EDITH KORDON, ADALI PECCI Y ALEJANDRA GUBERMAN

Pinamar, Buenos Aires, Argentina

Congreso; X PABMB Congress; 2005

SAIB

Signal transducer and activator of transcription (STATs)-mediated gene regulation has been implicated in cellular functions with relevance to a variety of processes. Stat proteins play a crucial role in normal and tumoral mammary epithelium. Stat5 is strongly activated towards the end of pregnancy and persists in an activated state until cessation of suckling. Contrary, Stat3 activation is hardly detectable during lactation, but is strongly induced at the onset of involution.  The aim of our work is to study the regulation of the activation of Stat3 and Stats5 to determine if exists crosstalk between them. Here, we study the levels of p-Stat3, p-Stat5a and p-Stat5b in HC11 cells, treated with different hormones pretending the cellular context in the distincts phases of the mammary epithelium. We confirmed that LIF activates Stat3 and found that in this context, there is a decrease in the levels of p-Stat5b. The levels of p-Stat3 were not increased with prolactin treatment, that induced b-casein expression in competent cells. As in transient transfection assays, we determined that Stat5a, Stat5b and Stat5a/Stat5b heterodimer repressed bcl-X promoter 1 (P1), we determined the levels of transcription from P1 by RT-PCR in the different conditions. We did not find any difference respect to the basal control. This is not in accordance with the levels of the p-Stats analyzed, but this could reflect the presence of another factor/s regulating P1. We are now studying the levels of p-STATs in cells treated with both stimulus, lactogenic hormones and LIF.