Long non-coding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), also known as nuclear-enriched transcript 2 (NEAT2), is highly conserved among mammals and highly expressed in the nucleus. It was first identified in lung cancer as a prognostic marker for metastasis but is also associated with several other solid tumors. In hepatocellular carcinoma (HCC), MALAT1 is a novel biomarker for predicting tumor recurrence after liver transplantation. The mechanism of overexpression in tumor progression remains unclear. In the present study, we investigated the role of specificity protein 1/3 (Sp1/3) in regulation of MALAT1 transcription in HCC cells. The results showed a high expression of Sp1, Sp3 and MALAT1 in HCC vs. paired non-tumor liver tissues, which was associated with the AFP level (Sp1, r=7.44, P=0.0064; MALAT1, r=12.37, P=0.0004). Co-silencing of Sp1 and Sp3 synergistically repressed MALAT1 expression. Sp1 binding inhibitor, mithramycin A (MIT), also inhibited MALAT1 expression in HCC cells. In conclusion, the upstream of MALAT1 contains five Sp1/3 binding sites, which may be responsible for MALAT1 transcription. Inhibitors, such as MIT, provide a potential therapeutic strategy for HCC patients with MALAT1 overexpression.

Abstract. MicroRNAs (miRNAs) are short, non-proteincoding RNAs and transcripts that are 18-24 nt in length. miR-204 was first identified as an anti-oncogene and is reported to be downregulated in non-small cell lung cancer, glioma, gastric and thyroid cancer. Recent studies have proposed that a low level of miR-204 expression is associated with tumor progression and disease outcome in breast cancer. Forkhead box A1 (FOXA1), a transcription factor, plays a crucial role in breast cancer and has been predicted as a target of miR-204. In the present study, we integrated the results of microarray analyses of breast cancer tissues obtained from an online database with our own determination of the expression of miR-204 in breast cancer MCF-7 cells using real-time qPCR (RT-qPCR). The proliferative capacity of the cells was assessed using MTT assays, and cell mobility and invasiveness were evaluated using cell migration and invasion assays, respectively. Flow cytometry was used to analyze apoptosis. FOXA1 levels were detected using RT-qPCR and western blot analysis. Luciferase assays were performed to confirm that FOXA1 is directly targeted by miR-204. The results showed that miR-204 was downregulated in breast cancer cells, and we found that miR-204 was expressed at a lower level in MCF-7 cells than that observed in normal breast epithelial HBL-100 cells. Overexpression of miR-204 inhibited cell proliferation, migration and invasion and promoted apoptosis. Western blot analysis revealed that the expression of FOXA1 at the protein level was significantly reduced after cells were transfected with miR-204-expressing viruses. Luciferase assays demonstrated that FOXA1 is a direct target of miR-204, which binds to FOXA1 in a complementary region. In conclusion, miR-204 regulates the biological behavior of breast cancer cells, including cell proliferation, invasion, metastasis and apoptosis, by directly targeting FOXA1. Thus, miR-204 may act as a tumor-suppressor, and the results of the present study provide a reference for future research into the potential mechanisms underlying breast cancer progression.