Abstract 3062: Ablation of parathyroid hormone-related protein in the triple negative human breast cancer line MDA-MB-231 inhibits its cancer stem cell phenotype

Abstract

Abstract Parathyroid hormone-related protein (PTHrP) is a pleiotropic hormone involved in a wide range of developmental & physiological processes. It is also dysregulated in advanced cancers where it causes malignancy-associated hypercalcemia & plays a major role in the progression of bone metastases. We have shown previously that PTHrP ablation delays tumor initiation & that it is preferentially expressed in triple negative breast cancer (TNBC).Here we investigated how PTHrP can influence the phenotype of the human TNBC cell line MDA-MB231 using CRISPR/cas 9 knockout technology. We used U6G RNA-Cas9-2A-red fluorescence protein (RFP) vector with a human PTHrP specific guide RNA directed to exon 4(knockout/KO) or an empty vector as control. PTHrP KO cells (RFP+) were isolated using AutoMacs Pro Separator & single cells were exp&ed in 96 well plates. Positive clones were confirmed by DNA sequencing. Real time PCR & immunofluorescence staining confirmed that 5/96 KO clones had between 95-99% decrease in PTHrP expression compared to control cells. We then assessed cancer stem cell (CSC) characteristics of both KO & control cell lines. Mammosphere formation was reduced by over 60% in KO cells. Stem cell phenotype assessed by ALDH1 & CD44+/CD24 low using FACS analysis were significantly reduced by over 30% in KO cells. Cell morphology analysis showed a shift from a mesenchymal phenotype towards an epithelial phenotype. Overall our data show that PTHrP regulates TNBC towards a more aggressive phenotype & suggest that it could be targeted therapeutically. Citation Format: Jiarong Li, Louis Doré-Savard, Karine Sellin, Anne Camirand, Richard Kremer. Ablation of parathyroid hormone-related protein in the triple negative human breast cancer line MDA-MB-231 inhibits its cancer stem cell phenotype [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3062.