Flavonoids exhibit health-promoting benefits against multiple chronic diseases, including cancer. Apigenin (4\',5,7-trihydroxyflavone), one flavonoid present in fruits and vegetables, is potentially applicable to chemoprevention. Despite considerable progress in the therapeutic regimen of liver cancer, its prognosis remains poor. MED28, a Mediator subunit for transcriptional activation, is implicated in the development of several types of malignancy; however, its role in liver cancer is unknown at present. In liver cancer, the AKT/mammalian target of rapamycin (mTOR) is one major pathway involved in the oncogenic process. The aim of this study is to investigate the role of apigenin and MED28 in AKT/mTOR signaling in liver cancer. We first identified a connectivity score of 92.77 between apigenin treatment and MED28 knockdown in several cancer cell lines using CLUE, a cloud-based software platform to assess connectivity among compounds and genetic perturbagens. Higher expression of MED28 predicted a poorer survival prognosis; MED28 expression in liver cancer tissue was significantly higher than that of normal tissue, and it was positively correlated with tumor stage and grade in The Cancer Genome Atlas Liver Cancer (TCGA-LIHC) data set. Knockdown of MED28 induced cell cycle arrest and suppressed the AKT/mTOR signaling in two human liver cancer cell lines, HepG2 and Huh 7, accompanied by less lipid accumulation and lower expression and nuclear localization of sterol regulatory element binding protein 1 (SREBP1). Apigenin inhibited the expression of MED28, and the effect of apigenin mimicked that of the MED28 knockdown. On the other hand, the AKT/mTOR signaling was upregulated when MED28 was overexpressed. These data indicated that MED28 was associated with the survival prognosis and the progression of liver cancer by regulating AKT/mTOR signaling and apigenin appeared to inhibit cell growth through MED28-mediated mTOR signaling, which may be applicable as an adjuvant of chemotherapy or chemoprevention in liver cancer.

BACKGROUND: Mediator is a multiprotein complex that acts as an essential transcriptional coactivator in eukaryotic cells for successful transcription. In this study, we aimed to explore the expression profile of 33 mediator subunit genes in oral cavity squamous cell carcinoma (OCSCC) and the functional role of MED28 in cellular behaviors of OCSCC cells.
METHODS: Single-cell (sc)RNA-seq data from OCSCC cells (Puram 2017\'s dataset) and bulk-seq data of the OCSCC subgroup of TCGA-head and neck squamous cell carcinoma (HNSC) were used for bioinformatic analysis. SCC9 cells were used in in-vitro and in-vivo analysis.
RESULTS: Among the 33 genes subjected to screening, MED28 showed the best prognostic value and its upregulation might independently predict shorter OS (HR: 3.699, 95% CI: 1.383-9.892, P = .009) and PFS (HR: 2.769, 95% CI: 1.462-5.244, P = .002). MED28 expression was positively correlated with cancer stem cell (CSC)-like properties of SCC9 cells, including colony/sphere formation, and the expression of CSC markers (CD44, KLF4, NANOG, and OCT4). RCOR1 could suppress the CSC-like properties of SCC9 cells and had direct interaction with MED28. Its overexpression partly abrogated MED28-induced expression of CSC markers. RCOR1 expression was associated with promoter hypermethylation, while MED28 expression was positively correlated with its MED28 copy number (Pearson\'s r = .44) in OCSCC tissues.
CONCLUSIONS: Among the mediator complex subunits, MED28 might serve as a potential biomarker of unfavorable survival. Its overexpression increased CSC-like activity of OCSCC cells, the effect of which could be abrogated by RCOR1 via direct interaction.

Non-small-cell lung cancer (NSCLC) accounts for the majority of the lung cancer cases that have become a leading cause of cancer deaths worldwide. Overexpression of transcription factor forkhead box M1 (FOXM1) is involved in the inauspicious development of several types of cancer, including lung tumor aggressiveness. Our laboratory has previously found that MED28, a Mediator subunit for transcriptional activation, modulates cell growth, epithelial-mesenchymal transition, migration, and invasion in human breast cancer cells. The objective of the current study is to investigate the potential role of MED28 and FOXM1 in NSCLC. In addition to A549 and PC9 cells, we also used a doxycycline-inducible system to generate FOXM1-overexpressed A549-DN cells, and we explored the connection of MED28 with FOXM1 and their effect on migration. Herein, we report that the increased expression levels of both MED28 and FOXM1 elevated the expression of matrix metalloproteinase 2 (MMP2), a metastasis marker, which enhanced cell migration and matrigel invasion of NSCLC cells. Furthermore, MED28 interacted with FOXM1, and both exhibited a mutual effect on the expression and subcellular localization. Moreover, MED28 small interfering RNA-mediated MMP2 gene suppression could be attenuated by inducible expression of a constitutively active form of FOXM1, which consequently restored the migration and invasion ability of NSCLC cells. Our data indicate that MED28 interacts with FOXM1, and each affects the expression and localization of the other, and, more importantly, both regulate MMP2-dependent migration and invasion in human lung cancer cells.

The evolutionarily conserved Mediator complex is a critical player in regulating transcription. Comprised of approximately two dozen proteins, the Mediator integrates diverse regulatory signals through direct protein-protein interactions that, in turn, modulate the influence of Mediator on RNA Polymerase II activity. One Mediator subunit, MED28, is known to interact with cytoplasmic structural proteins, providing a potential direct link between cytoplasmic dynamics and the control of gene transcription. Although identified in many animals and plants, MED28 is not present in yeast; no bona fide MED28 has been described previously in Caenorhabditis elegans. Here, we identify bioinformatically F28F8.5, an uncharacterized predicted protein, as the nematode homologue of MED28. As in other Metazoa, F28F8.5 has dual nuclear and cytoplasmic localization and plays critical roles in the regulation of development. F28F8.5 is a vital gene and its null mutants have severely malformed gonads and do not reproduce. F28F8.5 interacts on the protein level with the Mediator subunits MDT-6 and MDT-30. Our results indicate that F28F8.5 is an orthologue of MED28 and suggest that the potential to link cytoplasmic and nuclear events is conserved between MED28 vertebrate and nematode orthologues.