Parameters associated with metastatic dissemination are differentially modulated by specific isotypes of the retinoic acid receptor (RARs) in triple negative mammary cancer models

Natalia Amigo¹, Luciana Cañonero¹, Lizeth Ariza Bareño¹, Andrés Bechis¹, Alejandro Urtreger¹, Laura Todaro¹

Migration and adhesion are highly related to metastatic dissemination and retinoid system is implicated in their modulation. Objective: To evaluate the effect of activating each retinoic acid receptor (RAR) isotypes in migration, soluble MMPs activity, adhesion and metastatic potential in LM38LP and 4T1 triple negative murine cell lines. Both express all RAR isotypes except for RARβ in 4T1. Cells were treated with RARα agonist AM580 (200nM), RARβ agonist AC55649 (2μM), RARγ agonist BMS961 (50nM) or vehicle (DMSO). Migratory potential was evaluated by wound healing assay. AM580 and AC55649 reduced LM38LP migratory capacity (p<0.05) while AM580 increased migration in 4T1 (p<0.05). MMPs were analyzed by zymography. AM580, AC55649 and BMS961 decreased soluble MMP2 activity in LM38LP. On the contrary, AM580 increased MMP2 and MMP9 activity in 4T1. Besides, AM580 and AC55649 diminished LM38LP adhesive capacity while AC 55649 increased this in 4T1. In an experimental lung metastasis assay, cells treated with agonists where inoculated in BALB/c mice. The AC55649 pretreatment increased metastatic potential of LM38LP (p<0.05) while BMSS961 increased metastasis in 4T1 cell line (p<0.05). We hypothesize that the differences in RARβ expression between the cell lines could be responsible of opposite responses in biological effects studied. The increment in metastasis by RARβ/γ activation could be due to selection of a minority population with greater plasticity to colonize the metastatic site.