PO-240 Targeting cancer stem cells in mammary triple negative cell line by retinoids and lapatinib treatments

Abstract

IntroductionCancer stem cells (CSC) are resistant to chemotherapy and radiation and they are also considered as ‘metastasis seed’.In order to suggest CSCs as a new therapeutic-intervention target, in this work we propose to study the effect of retinoid ATRA (differentiation therapy) and HER2 inhibitor Lapatinib treatment on:Expression profile of pluripotent genes, retinoid receptors system and E-Cadherin levels.In vitro growth, invasive capacity and in vivo metastatic potential.For this purpose, we use the triple negative murine cell line 4 T1 (tumorigenic and metastatic in BALB/c mice). Previously we corroborate that CSC from 4 T1, MCF7 and T47D (both these last, HER2 negative human breast cell lines), express HER2 only in that cell component.Material and methodsExperimental Model: triple negative murine cell line 4 T1 (tumorigenic and metastatic in BALB/c mice).Treatments: ATRA (1 µM) and Lapatinib (1 µM)RT-qPCR were used to evaluate retinoic acid receptors and pluripotential genes expression- Mammospheres culture was used to enrich in CSC component.Clonogenic assay was performed by seeding CSC in low densityInvasive capacity was evaluated using Matrigel-coated transwells.Results and discussionsThrough RT-qPCR, we could observe that ATRA (1 µM) and Lapatinib (1 µM) treatments, separately or in combination, were able to increase retinoic acid receptors RARα and RARγ and decrease RARβ receptor levels. Moreover, the same treatments induced an increment in E-Cadherin and reduced the expression of main pluripotential genes: NANOG, OCT4 and SOX2. Combination treatment induced growth inhibition in 4 T1 mammospheres and in their clonogenic capacity. Regarding parameters associated with malignant progression using Matrigel-coated transwells, we detect that combined treatment increase CSC invasive capacity, however in experimental metastases assays with pretreated-CSC, treatments separately or in combination significantly decreases lung colonisation.ConclusionTreatments with both ATRA and Lapatinib were able to induce CSC differentiation and reduced their lung nesting ability, leading to a less malignant phenotype.