Abstract 44P
Background
Breast cancer is one of the most common malignancies among women. MCF-7 are hormone-dependent while MDA-MB-231 are triple-negative. Estrogen receptors (ERs) play a critical role in breast cancer progression, modulating thereby the expression of long non-coding RNA (H19) and telomerase (hTERT), regulating thereafter glycolytic enzymes as PKM2 and LDHA. miR-let-7a a tumor suppressor could be antagonized by high expression of H19. All-trans retinoic acid (ATRA) has a major role in cell proliferation and differentiation after solid tumors treatment, like breast cancer. The study aims to investigate a possible link among ATRA, H19, hTERT, and glycolytic metabolism as well as the variation of the expression of miR-let-7a in MCF-7 and MDA-MB-231.
Methods
MCF-7 and MDA-MB-231 were treated with 5μM ATRA for 48h. To investigate the role of ERs, cells were treated with 100 nM fulvestrant or combined with 5μM ATRA for 48h. siH19 transfection was performed with 20 nM for 72h. Cytotoxicity assay was achieved using WST-8. RNA expression was quantified by RT-qPCR. Protein expression was evaluated by western blot. PKM2 activity was measured by an LDH coupled assay.
Results
Following the treatment of MCF-7 with ATRA or fulvestrant, a significant decrease in the expression of ERα, H19, hTERT, PKM2, LDHA RNAs is detected; as well as, in the protein expression and activity of PKM2. However, the expression of miR-let-7a and ERβ RNAs increased significantly. Gene expression modulation is enhanced after treatment combination. As a primary result, after transfection of siH19 combined with ATRA in MCF-7, the expression of all mentioned genes was reduced except that of miR-let-7a and ERβ which increased compared to siH19 or ATRA treatment. As preliminary results, ATRA treatment of MDA-MB-231, increased the expression of H19 and LDHA RNAs, without significant variation on the others. Fulvestrant treatment leads to no significant change of all genes. RNA’s expression of LDHA increases and PKM2 decreases after the treatment combination. The protein expression and activity of PKM2 increase after co-treatment only.
Conclusions
Our study shows that ATRA modulates glycolytic enzymes PKM2 and LDHA, together with H19, hTERT, and miR-let-7a, in breast cancer cell lines.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Saint Joseph University.
Funding
Research Council of Saint Joseph University in Beirut.
Disclosure
All authors have declared no conflicts of interest.