Effect of retinoic acid (ATRA) treatment on growth and malignant progression of human mammary tumor cells overexpressing protein kinase C alpha (PKCa)

MARIA I. DIAZ BESSONE; DAMIAN E. BERARDI; STÉFANO M. CIRIGLIANO; AGUSTINA TARUSELLI; AGOSTINA CAMMARATA; LAURA B. TODARO; ALEJANDRO J. URTREGER

Cdad Autonoma de Buenos Aires

Congreso; Segunda Reunión Conjunta de Sociedades de BioCiencias; 2017

Sociedad Argentina de Investigación Clínica (SAIC)

PKC enzymes constitute a family of serine-threonine kinases that control numerous cellular functions, such as growth, apoptosis and malignant transformation, whereas the retinoid system is involved in cell differentiation.In this work, we studied the effect of retinoid treatment on characteristics associated with tumor progression of MDA-MB231 and T47D cell lines overexpressing PKCa.PKCa overexpression was unable to alter the proliferative capacity of both cell lines in vitro. When we assess the effect of ATRA, T47D-PKCa cells significantly decrease their proliferative capacity, whereas MDA-MB231-PKCa did not respond to retinoid treatment. Cell cycle analysis, by flow cytometry, showed that ATRA induces an arrest in the G1 phase, only in the T47D subline.Next, we analyzed the functionality of Retinoic Acid Response Elements (RARE) by a gene reporter assay. Both T47D and MDA-MB231 derived sublines responded to ATRA increasing RARE activity. Then, we studied AP1 sites since retinoids effects also involve the trans-repression of this element. Although T47D sublines showed a decrease in AP1 activity when treated with ATRA, no effect was observed in MDA-MB231.Retinoid receptors expression (analyzed by RT-qPCR) showed that MDA-MB231 cells were unable to increase RARb and RARg levels in response to retinoid treatment, as it was observed in T47D cells. As the repression of AP1 sites, induced by ATRA, has been assigned to RARb we overexpress this receptor in MDA-MB231 cells. Now a clear trans-repression of AP1 sites was observed after ATRA treatment.Our results suggest that PKCa sensitize T47D cell to retinoid treatment, which correlates our previous observations in murine lines. On the other hand, the lack of response to retinoid treatment of MDA-MB231 could be due to the inability to trans-repress AP1 sites, due the lack of RARb expression.