PROPRANOLOL BEHAVES AS A BETA-ADRENERGIC AGONIST REORGANIZING ACTIN CYTOSKELETON ON MCF-10A BREAST CELL LINE

GARGIULO L; RIVERO E; DI SERVI N; DAVIO C; BUFFONE M; LUTHY IA; BRUZZONE A

Buenos Aires

Jornada; XX Jornadas anuales de la SAB y XVII Jornadas anuales de sociedad uruguaya de biociencias; 2018

SAB (Argentina)-SUB (Uruguay)

Propranolol (PROP) has been classically classified as a β-blocker, antagonizing β-adrenergic signaling in the cardiovascular system. In the last decade, based on retrospective studies, PROP has been proposed as a repurposed drug against breast cancer. However, little is known about the possible mechanism of action. Moreover, PROP has been recently suggested as a biased agonist. Our previous results support the hypothesis that PROP is able to mimic the agonist Isoproterenol (ISO) in breast models. The aim of the present research was to compare the effects of PROP with those of ISO using the non-tumorigenic breast cell line MCF-10A. PROP (1μM) and ISO (1µM) diminished cell proliferation and increased cell adhesion. PROP was not able to reverse the effect ofthe agonist. Moreover, the effect of PROP and ISO on cell proliferation and cell adhesion was reverted by 10 μM ICI-118551, a pure β2-antagonist, suggesting an agonist effect of PROP via β2-adrenergic receptor subtype. In order to study the agonist action of PROP regarding cell adhesion, we analyzed the molecular signaling pathways involved in actin cytoskeleton reorganization. The incubation with both ISO and PROP quickly reorganized actin cytoskeleton, increasing the fibrillar form of actin. The phosphorylation of LIMK and COFILIN was implied in this effect. The phosphorylation of the lattercauses its inactivation, stabilizing in this way actin filaments. This correlates with the enhancement of actin filaments observed by immunofluorescence.The incubation with the LIMK inhibitor (BMS-3) or PAK4 inhibitor (PF3758309), a protein involved in LIMK activation, abrogated the effect of ISO and PROP on cell adhesion, demonstrating that both drugs regulate this parameter through cytoskeleton reorganization.On the other hand, ISO and PROP phosphorylated members of the protein family ERM, although their kinetics differed. ISO but not PROP was able to phosphorylate VASP in Ser157, a site phosphorylated by protein kinase A. Even if the mechanisms downstream of β-adrenergic receptor in this pathway have not been yet uncovered, certain analogs of cAMP are able to activate the same pathways. Concomitantly, ISO was able to enhance cAMP levels, while PROP was not. Together, these results suggest that PROP behaves as an agonist on MCF-10A cells, suggesting a biased agonism mechanism, independent of the PKA pathway.