Histone lysine demethylase 4B regulates general and unique gene expression signatures in hypoxic cancer cells

Targeting inflammatory macrophages rebuilds therapeutic efficacy of DOT1L inhibition in hepatocellular carcinoma

Epigenetic reprogramming is a promising therapeutic strategy for aggressive cancers, but its limitations in vivo remain unclear. Here, we showed, in detailed studies of data regarding 410 patients with human hepatocellular carcinoma (HCC), that increased histone methyltransferase DOT1L triggered epithelial-mesenchymal transition-mediated metastasis and served as a therapeutic target for human HCC. Unexpectedly, although targeting DOT1L in vitro abrogated the invasive potential of hepatoma cells, abrogation of DOT1L signals hardly affected the metastasis of hepatoma in vivo. Macrophages, which constitute the major cellular component of the stroma, abrogated the anti-metastatic effect of DOT1L targeting. Mechanistically, NF-κB signal elicited by macrophage inflammatory response operated via a non-epigenetic machinery to eliminate the therapeutic efficacy of DOT1L targeting. Importantly, therapeutic strategy combining DOT1L-targeted therapy with macrophage depletion or NF-κB inhibition in vivo effectively and successfully elicited cancer regression. Moreover, we found that the densities of macrophages in HCC determined malignant cell DOT1L-associated clinical outcome of the patients. Our results provide insight into the crosstalk between epigenetic reprogramming and cancer microenvironments and suggest that strategies to influence the functional activities of inflammatory cells may benefit epigenetic reprogramming therapy.

Discovery of spirooxindole-derived small-molecule compounds as novel HDAC/MDM2 dual inhibitors and investigation of their anticancer activity

Simultaneous inhibition of more than one target is considered to be a novel strategy in cancer therapy. Owing to the importance of histone deacetylases (HDACs) and p53-murine double minute 2 (MDM2) interaction in tumor development and their synergistic effects, a series of MDM2/HDAC bifunctional small-molecule inhibitors were rationally designed and synthesized by incorporating an HDAC pharmacophore into spirooxindole skeletons. These compounds exhibited good inhibitory activities against both targets. In particular, compound 11b was demonstrated to be most potent for MDM2 and HDAC, reaching the enzyme inhibition of 68% and 79%, respectively. Compound 11b also showed efficient antiproliferative activity towards MCF-7 cells with better potency than the reference drug SAHA and Nutlin-3. Furthermore, western blot analysis revealed that compound 11b increased the expression of p53 and Ac-H4 in MCF-7 cells in a dose-dependent manner. Our results indicate that dual inhibition of HDAC and MDM2 may provide a novel and efficient strategy for the discovery of antitumor drug in the future.

Mechanism of histone deacetylases in cardiac hypertrophy and its therapeutic inhibitors

Cardiac hypertrophy is a key process in cardiac remodeling development, leading to ventricle enlargement and heart failure. Recently, studies show the complicated relation between cardiac hypertrophy and epigenetic modification. Post-translational modification of histone is an essential part of epigenetic modification, which is relevant to multiple cardiac diseases, especially in cardiac hypertrophy. There is a group of enzymes related in the balance of histone acetylation/deacetylation, which is defined as histone acetyltransferase (HAT) and histone deacetylase (HDAC). In this review, we introduce an important enzyme family HDAC, a key regulator in histone deacetylation. In cardiac hypertrophy HDAC I downregulates the anti-hypertrophy gene expression, including Kruppel-like factor 4 (Klf4) and inositol-5 phosphatase f (Inpp5f), and promote the development of cardiac hypertrophy. On the contrary, HDAC II binds to myocyte-specific enhancer factor 2 (MEF2), inhibit the assemble ability to HAT and protect against cardiac hypertrophy. Under adverse stimuli such as pressure overload and calcineurin stimulation, the HDAC II transfer to cytoplasm, and MEF2 can bind to nuclear factor of activated T cells (NFAT) or GATA binding protein 4 (GATA4), mediating inappropriate gene expression. HDAC III, also known as SIRTs, can interact not only to transcription factors, but also exist interaction mechanisms to other HDACs, such as HDAC IIa. We also present the latest progress of HDAC inhibitors (HDACi), as a potential treatment target in cardiac hypertrophy.

A targeted nanomodulator capable of manipulating tumor microenvironment against metastasis

Recently, lactate has been considered as an alternative direct energy substance to glucose for tumor proliferation and metastasis. Meanwhile, mitochondria, as important energy-supplying organelles, are also closely related to tumor progression. Consequently, a new research direction for lactate comprises lactate deprivation coupled with mitochondria-targeted phototherapy to achieve a safer and more effective strategy against tumor metastasis. Herein, linoleic acid-conjugated hyaluronic acid (HL), disulfide bond-rich nanovehicle (mesoporous silica, MOS), mitochondria-targeted IR780 (M780) and lactate oxidase (LOD) are rationally designed as a specific-targeting metabolism nanomodulator (HL/MOS@M780&LOD NPs), fulfilling the task of simultaneous depriving cells of lactate and damaging mitochondria to prevent tumor metastasis. Interestingly, M780-mediated photodynamic therapy (PDT) and LOD-mediated starvation therapy can effectively exacerbate the hypoxia state of tumor cells, thereby increasing the free iron levels to activate ferroptosis. On one hand, pyruvic acid and H₂O₂ generated by LOD-mediated lactate metabolism can provide powerful conditions for iron-catalyzed ferroptosis. On the other, the depleted GSH and increased reactive oxygen species (ROS) can oxidize linoleic acid into lipid peroxides (LPO) to further augment ferroptosis. The designed nanomodulator therefore shows great promise for fighting tumor metastasis by manipulating energy metabolism and the hypoxia microenvironment.

Histone lysine demethylase 4B regulates general and unique gene expression signatures in hypoxic cancer cells

The hypoxic tumor microenvironment promotes tumor survival by inducing the expression of genes involved in angiogenesis and metastasis. As a direct target of hypoxia-inducible factor, lysine demethylase 4B (KDM4B) is overexpressed in multiple cancers, suggesting that a general KDM4B regulatory mechanism may exist in these cancer types. In this study, we sought to further investigate the general and unique roles of KDM4B in ovarian, colon, and renal cancer cells. We first identified a set of potential KDM4B targets shared by SKOV3ip.1, HCT116, and RCC4 cell lines, as well as numerous genes specifically regulated in each cell line. Through Gene Ontology, KEGG, and Oncobox pathway analyses, we found that KDM4B primarily regulated biosynthetic and cell cycle pathways in normoxia, whereas in hypoxia, it regulated pathways associated with inflammatory response and migration. TCGA data analyses reveal high expression of KDM4B in multiple cancer types and differential expression across cancer stages. Kaplan-Meier plots suggest that elevated KDM4B expression may contribute to a better or worse prognosis in a manner specific to each cancer type. Overall, our findings suggest that KDM4B plays complex roles in regulating multiple cancer processes, providing a useful resource for the future development of cancer therapies that target KDM4B expression.