29P - XIST overrides the regulatory effect of miR-194 on its immunomodulatory target PD-L1 in breast cancer

Date 05 November 2016
Event ESMO Symposium on Immuno-Oncology 2016
Session Lunch and general poster viewing
Presenter Marwa Hamed
Citation Annals of Oncology (2016) 27 (suppl_8): viii4-viii17. 10.1093/annonc/mdw527
Authors M.M. Hamed1, R.A.E. Eissa2, L.A.A. Kassem3, H.M. El Tayebi1
  • 1Genetic Pharmacology Research Group, Department Of Pharmacology And Toxicology, German University in Cairo-GUC, 11835 - Cairo/EG
  • 2General Surgery Department, Faculty Of Medicine, Ain Shams University, 11566 - Cairo/EG
  • 3Physiology Unit, Department Of Pharmacology And Toxicology, German University in Cairo-GUC, 11835 - Cairo/EG

Abstract

Aim/Background

X inactive-specific transcript (XIST) expression has been found to be downregulated in many cancers such as ovarian cancer. miR-194 is expressed in a cancer-specific manner, where it showed anti-metastatic effect in liver cancer in contrast to colon cancer. Till date, implication of ncRNAs in immunotherapy is inadequately studied. Nevertheless, blockade of Immune Checkpoints especially programmed cell death receptor/ligand PD-1/PD-L1 in cancer became a principle approach in cancer therapy. PD-L1 targeted therapies are yet under investigation. This study aims to investigate the impact of miR-194 and XIST on the immunomodulatory ligand PD-L1 in Breast Cancer.

Methods

Bioinformatics were performed to predict targets of miR-194. BC as well as normal biopsies were surgically resected from 11 breast cancer patients. Total RNA extraction was performed using BIOZOL reagent followed by RealTime qPCR. In vitro manipulation of miR-194 was performed in MDA-MB-231 human breast cancer cells to analyze the expression of PD-L1 and XIST mRNA.

Results

In silico, miR-194 was found to target PD-L1 and XIST mRNAs. LncTar predicted XIST to target PD-L1 mRNA. The expression of miR-194 was markedly increased in BC than controls (P = 0.0323). PD-L1 mRNA expression was significantly increased in BC than controls (P = 0.0351) and XIST was dramatically downregulated in BC than controls (P = 0.0401). Manipulation of miR-194 in BC cells by miR-194 oligos markedly decreased in XIST expression (P = 0.0034). However, anti-miR-194 dramatically upregulated XIST (P = 0.0032). Mimicking of miR-194 significantly decreased PD-L1 mRNA expression (P = 0.0276), unexpectedly, anti-miR-194 markedly decreased PD-L1 mRNA expression by 400 folds more than miR-194 oligos.

Conclusions

This study reveals a competitive interaction between miR-194 and XIST in the regulation of PD-L1 through unraveling a novel immunomodulatory loop. The data showed that the elevated expression of XIST in BC cells potently overrides the stimulatory effect of anti-miR-194 on PD-L1. This suggests that XIST has a promising role in PD-L1-mediated immunotherapy in breast cancer.

Clinical trial identification

Legal entity responsible for the study

German University in Cairo-GUC, Cairo, Egypt

Funding

German University in Cairo-GUC, Cairo, Egypt

Disclosure

All authors have declared no conflicts of interest.