INTERACTION OF TGFβ2 AND HEREGULIN FOR RAC ACTIVATION AND CELL MIGRATION IN BREAST CANCER CELLS.

GONZALEZ AGUSTIN; LARA ANGELA; WERTHEIMER EVA

Buenos Aires

Congreso; LXII ANNUAL MEETING OF ARGENTINE SOCIETY OF CLINICAL INVESTIGATION (SAIC); 2017

SAIC

Current therapies for breast cancer often fail attacking the main focus that directs it. Rac1 is a Rho-GTPase that promotes migration of breast cancer cells. We aim to study different signaling pathways that converge in Rac1 for breast cancer progression. Heregulin (HRG) is an ErbB ligand that activates Rac1 in a time-dependent manner. To determine whether a short exposure to HRG is necessary and sufficient for maintaining Rac activation over time, T-47D cells were stimulated for 5, 15 or 30min, washed to remove the stimulus and assayed for Rac activation at 1h. When HRG was supplied for 5min, Rac activation significantly decreased at 1h compared to control (p 0.05). Addition of HRG immediately after washing was sufficient to recover Rac activation. When HRG was removed at 15min, slight changes on Rac activation were observed. However, removal of the conditioned medium after 30min suppressed the maintenance of Rac activation, and a second addition of HRG failed to recover the effect. We conclude that HRG is necessary for initial Rac activation and, subsequently, cells start producing autocrine factors that are necessary for maintenance of HRG-initiated Rac activation. Previous data showed that Rac activation by HRG leads to an increase in TGFβ2 expression in breast cancer cells. In fact, the TGFβ family is involved in cell migration and metastasis. Here, we show that the increase of TGFβ2 mRNA after HRG stimulation is time-dependent: it significantly increases (p 0.05) after 30min, with maximum at 2h. Wound healing assays reveled that TGFβ2 itself induce migration of MCF7 cells in a dose-dependent manner, with maximum at 10ng/ml. Combined addition of HRG and TGFβ2 produced the same increase on cell migration as HRG alone. These results suggest that there is a sequential relationship between the Rac1 activation peak and the maximal increase of TGFβ2. We propose that this cytokine is necessary for the maintenance of HRG-triggered phenotype of breast cancer cells.