The hot tumor nature of triple-negative breast cancer (TNBC) tumors serves as a key player in the prognosis of such patients. Giving a strong rational to support the immune-based therapeutic approaches for this hard-to-treat group of patients. Immune checkpoint blockades (ICBs) have been extensively studied especially PDL1/PD1 blockers. Yet, the number of resistant cases started to escalate. Therefore, it became crucial to probe for molecular engines regulating PDL1 expression. Currently, unveiling novel networks between non-coding RNAs (ncRNAs) and their roles in regulating TNBC has become a research hotspot. Our group has recently reported that miR-17-5p represses the immune suppressive IL-10 production. However, its role in regulating PDL1 is still unprobed in TNBC. CCAT1 is an oncogenic long ncRNA. CCAT1 acts as a sponge for several tumor suppressor miRNAs affecting it is downstream targets. Therefore, the aim of this study is to investigate part of the interactive ncRNA network regulating PDL1 in TNBC patients.
BC patients (n=35) were recruited. Bioinformatics analysis was executed. TNBC cell lines were cultured and transfected with different oligonucleotides using HiPerFect Transfection Reagent. Total RNA was extracted, reverse transcribed and quantified using qRT-PCR. Cellular viability, colony forming ability and migration were measured using MTT, colony forming and scratch assays, respectively.
In-silico analysis revealed that PDL1 is a potential target for miR-17-5p and CCAT1. miR-17-5p was found to be under-expressed in PDL1+/CCAT+ TNBC tissues compared to its normal counterparts. Ectopic expression of miR-17-5p and/or knocking down of CCAT1 resulted in a prominent reduction PDL1. On the other hand, a mutual interactive loop was observed between miR-17-5p and CCAT1 in TNBC cells; miR-17-5p mimics repressed CCAT1 levels while CCAT1 siRNAs resulted in an induction of miR-17-5p levels. Functionally, CCAT1 siRNAs and miR-17-5p mimics markedly halted TNBC hallmarks.
This study highlights a novel ncRNA circuit regulating PDL1 in TNBC patients. Thus, targeting CCAT1/miR-17-5p axis might provide a potential solution in overcoming the ICBs resistance arises in some TNBC patients.
German University in Cairo.
Has not received any funding.
All authors have declared no conflicts of interest.