Hint from an Enzymatic Reaction: Superoxide Dismutase Models Efficiently Suppress Colorectal Cancer Cell Proliferation.

Superoxide dismutases (SODs) are essential antioxidant enzymes that prevent massive superoxide radical production and thus protect cells from damage induced by free radicals. However, this concept has rarely been applied to directly impede the function of driver oncogenes, thus far. Here, leveraging efforts from SOD model complexes, we report the novel finding of biomimetic copper complexes that efficiently scavenge intracellularly generated free radicals and, thereby, directly access the core consequence of colorectal cancer suppression. We conceived four structurally different SOD-mimicking copper complexes that showed distinct disproportionation reaction rates of intracellular superoxide radical anions. By replenishing SOD models, we observed a dramatic reduction of intracellular reactive oxygen species (ROS) and adenine 5'-triphosphate (ATP) concentrations that led to cell cycle arrest at the G2/M stage and induced apoptosis in vitro and in vivo. Our results showcase how nature-mimicking models can be designed and fine-tuned to serve as a viable chemotherapeutic strategy for cancer treatment.

Bioinspired nonheme iron complex that triggers mitochondrial apoptotic signalling pathway specifically for colorectal cancer cells.

The activation of dioxygen is the keystone of all forms of aerobic life. Many biological functions rely on the redox versatility of metal ions to perform reductive activation-mediated processes entailing dioxygen and its partially reduced species including superoxide, hydrogen peroxide, and hydroxyl radicals, also known as reactive oxygen species (ROS). In biomimetic chemistry, a number of synthetic approaches have sought to design, synthesize and characterize reactive intermediates such as the metal-superoxo, -peroxo, and -oxo species, which are commonly found as key intermediates in the enzymatic catalytic cycle. However, the use of these designed complexes and their corresponding intermediates as potential candidates for cancer therapeutics has scarcely been endeavored. In this context, a series of biomimetic first-row transition metal complexes bearing a picolylamine-based water-soluble ligand, [M(HN3O2)]2+ (M = Mn2+, Fe2+, Co2+, Cu2+; HN3O2 = 2-(2-(bis(pyridin-2-ylmethyl)amino)ethoxy)ethanol) were synthesized and characterized by various spectroscopic methods including X-ray crystallography and their dioxygen and ROS activation reactivity were evaluated in situ and in vitro. It turned out that among these metal complexes, the iron complex, [Fe(HN3O2)(H2O)]2+, was capable of activating dioxygen and hydrogen peroxide and produced the ROS species (e.g., hydroxyl radical). Upon the incubation of these complexes with different cancer cells, such as cervical, breast, and colorectal cancer cells (MDA-MB-231, AU565, SK-BR-3, HeLa S3, HT-29, and HCT116 cells), only the iron complex triggered cellular apoptosis specifically for colorectal cancer cells; the other metal complexes show negligible anti-proliferative activity. More importantly, the biomimetic complexes were harmless to normal cells and produced less ROS therein. The use of immunocytochemistry combined with western blot analysis strongly supported that apoptosis occurred via the intrinsic mitochondrial pathway; in the intracellular network, [Fe(HN3O2)(H2O)]2+ resulted in (i) the activation and/or production of ROS species, (ii) the induction of intracellular impaired redox balance, and (iii) the promotion of the mitochondrial apoptotic signaling pathway in colorectal cancer cells. The results have implications for developing novel biomimetic complexes in cancer treatments and for designing potent candidates with cancer-specific antitumor activity.

Epigenetic Upregulation of MAGE-A Isoforms Promotes Breast Cancer Cell Aggressiveness.

After decades-long efforts to diagnose and treat breast cancer, the management strategy that has proved most successful to date is molecular-subtype-specific inhibition of the hormone receptors and HER2 that are expressed by individual cancers. Melanoma-associated antigen (MAGE) proteins comprise >40 highly conserved members that contain the MAGE homology domain. They are often overexpressed in multiple cancers and contribute to cancer progression and metastasis. However, it remains unclear whether the biological activity arising from MAGE gene expression is associated with breast cancer subtypes. In this study, we analyzed the RNA-sequencing (RNA-seq) data of 70 breast cancer cell lines and found that MAGEA12 and MAGEA3 were highly expressed in a subset of these lines. Significantly, MAGEA12 and MAGEA3 expression levels were independent of hormone receptor expression levels but were closely associated with markers of active histone modifications. This indicates that overexpression of these genes is attributable to epigenetic deregulation. RNA-seq of MAGEA12-depleted cells was then used to identify 382 candidate targets of MAGEA12 that were downregulated by MAGEA12 depletion. Furthermore, our gain-of-function experiments showed that MAGEA12 overexpression promoted aggressive behaviors of malignant breast cancer cells, including enhancing their cell migration and invasion. These changes were associated with increased epigenetic deregulation of the MAGEA12 signature genes. Thus, MAGEA12 may play an important role in breast cancer malignancy. Taken together, our findings suggest that MAGEA12 could be a promising therapeutic target in breast cancer, and its overexpression and epigenetic changes could serve as subtype classification biomarkers.

Targeting the Epigenome as a Novel Therapeutic Approach for Breast Cancer.

Breast cancer is one of complex diseases that are influenced by environment. Various genetic and epigenetic alterations are provoking causes of breast carcinogenesis. Dynamic epigenetic regulation including DNA methylation and histone modification induces dysregulation of genes related to proliferation, apoptosis, and metastasis in breast cancer. DNA methylation is strongly associated with the repression of transcription through adding to the methyl group by DNA methyltransferases (DNMTs), and tumor suppressor genes such as CCND2 and RUNX3 have been investigated to undergo hypermethylation at promoter region in breast cancer. In addition, histone deacetylases (HDACs) contribute to transcriptional repression by removing acetyl group at lysine residues leading to tumorigenesis. Since epigenetic changes are reversible, therapeutic approaches have been applied with epigenetic modification drugs such as DNMT inhibitors and HDAC inhibitors. In this chapter, we will summarize the feature of epigenetic markers in breast cancer cells and the effect of single or combination of epigenetic reagents for breast cancer therapy.

Functional roles of CTCF in breast cancer.

CTCF, Zinc-finger protein, has been identified as a multifunctional transcription factor that regulates gene expression through various mechanisms, including recruitment of other co-activators and binding to promoter regions of target genes. Furthermore, it has been proposed to be an insulator protein that contributes to the establishment of functional threedimensional chromatin structures. It can disrupt transcription through blocking the connection between an enhancer and a promoter. Previous studies revealed that the onset of various diseases, including breast cancer, could be attributed to the aberrant expression of CTCF itself or one or more of its target genes. In this review, we will describe molecular dysfunction involving CTCF that induces tumorigenesis and summarize the functional roles of CTCF in breast cancer. [BMB Reports 2017; 50(9): 445-453].