A truncated and catalytically inactive isoform of KDM5B histone demethylase accumulates in breast cancer cells and regulates H3K4 tri-methylation and gene expression

To Erase or Not to Erase: Non-Canonical Catalytic Functions and Non-Catalytic Functions of Members of Histone Lysine Demethylase Families

Histone lysine demethylases (KDMs) play an essential role in biological processes such as transcription regulation, RNA maturation, transposable element control, and genome damage sensing and repair. In most cases, their action requires catalytic activities, but non-catalytic functions have also been shown in some KDMs. Indeed, some strictly KDM-related proteins and some KDM isoforms do not act as histone demethylase but show other enzymatic activities or relevant non-enzymatic functions in different cell types. Moreover, many studies have reported on functions potentially supported by catalytically dead mutant KDMs. This is probably due to the versatility of the catalytical core, which can adapt to assume different molecular functions, and to the complex multi-domain structure of these proteins which encompasses functional modules for targeting histone modifications, promoting protein-protein interactions, or recognizing nucleic acid structural motifs. This rich modularity and the availability of multiple isoforms in the various classes produced variants with enzymatic functions aside from histone demethylation or variants with non-catalytical functions during the evolution. In this review we will catalog the proteins with null or questionable demethylase activity and predicted or validated inactive isoforms, summarizing what is known about their alternative functions. We will then go through some experimental evidence for the non-catalytical functions of active KDMs.

The emerging roles of histone demethylases in cancers

Modulation of histone methylation status is regarded as an important mechanism of epigenetic regulation and has substantial clinical potential for the therapy of diseases, including cancer and other disorders. The present study aimed to provide a comprehensive introduction to the enzymology of histone demethylases, as well as their cancerous roles, molecular mechanisms, therapeutic possibilities, and challenges for targeting them, in order to advance drug design for clinical therapy and highlight new insight into the mechanisms of these enzymes in cancer. A series of clinical trials have been performed to explore potential roles of histone demethylases in several cancer types. Numerous targeted inhibitors associated with immunotherapy, chemotherapy, radiotherapy, and targeted therapy have been used to exert anticancer functions. Future studies should evaluate the dynamic transformation of histone demethylases leading to carcinogenesis and explore individual therapy.

KDM5 family as therapeutic targets in breast cancer: Pathogenesis and therapeutic opportunities and challenges

Breast cancer (BC) is the most frequent malignant cancer diagnosis and is a primary factor for cancer deaths in women. The clinical subtypes of BC include estrogen receptor (ER) positive, progesterone receptor (PR) positive, human epidermal growth factor receptor 2 (HER2) positive, and triple-negative BC (TNBC). Based on the stages and subtypes of BC, various treatment methods are available with variations in the rates of progression-free disease and overall survival of patients. However, the treatment of BC still faces challenges, particularly in terms of drug resistance and recurrence. The study of epigenetics has provided new ideas for treating BC. Targeting aberrant epigenetic factors with inhibitors represents a promising anticancer strategy. The KDM5 family includes four members, KDM5A, KDM5B, KDM5C, and KDMD, all of which are Jumonji C domain-containing histone H3K4me2/3 demethylases. KDM5 proteins have been extensively studied in BC, where they are involved in suppressing or promoting BC depending on their specific upstream and downstream pathways. Several KDM5 inhibitors have shown potent BC inhibitory activity in vitro and in vivo, but challenges still exist in developing KDM5 inhibitors. In this review, we introduce the subtypes of BC and their current therapeutic options, summarize KDM5 family context-specific functions in the pathobiology of BC, and discuss the outlook and pitfalls of KDM5 inhibitors in this disease.

Entecavir: A Review and Considerations for Its Application in Oncology

Entecavir (ETV) is a drug used as a first-line treatment for chronic hepatitis B (CHB) virus infection because it is a guanosine nucleoside analogue with activity against the hepatitis B virus polymerase. The ETV dosage can range from 0.5 mg to 1 mg once a day and the most common side effects include headache, insomnia, fatigue, dizziness, somnolence, vomiting, diarrhea, nausea, dyspepsia, and increased liver enzyme levels. In addition to its conventional use, ETV acts as an inhibitor of lysine-specific demethylase 5B (KDM5B), an enzyme that is overexpressed in breast, lung, skin, liver, and prostate tumors and is involved in the hormonal response, stem cell regeneration, genomic stability, cell proliferation, and differentiation. The KDM5B enzyme acts as a transcriptional repressor in tumor suppressor genes, silencing them, and its overexpression leads to drug resistance in certain tumor types. Furthermore, the literature suggests that KDM5B activates the PI3K/AKT signaling pathway, while reducing KDM5B expression decreases AKT signaling, resulting in decreased tumor cell proliferation. In silico studies have demonstrated that ETV can inhibit tumor cell proliferation and induce apoptosis by reducing KDM5B expression. ETV also appears to inhibit PARP-1, has a high genetic barrier, reducing the chance of resistance development, and can also prevent the reactivation of the hepatitis B virus in cancer patients, which have proven to be significant advantages regarding its use as a repurposed drug in oncology. Therefore, ETV holds promise beyond its original therapeutic indication.

Knockdown of KDM5B Leads to DNA Damage and Cell Cycle Arrest in Granulosa Cells via MTF1

KDM5B is essential for early embryo development, which is under the control of maternal factors in oocytes. Granulosa cells (GCs) play a critical role during oocyte mature. However, the role of KDM5B in GCs remains to be elucidated. In the current study, we found that KDM5B expressed highly in the ovaries and located in goat GCs. Using an RNA sequence, we identified 1353 differentially expressed genes in the KDM5B knockdown GCs, which were mainly enriched in cell cycle, cell division, DNA replication and the cellular oxidative phosphorylation regulation pathway. Moreover, we reported a decrease in the percentage of proliferated cells but an increase in the percentage of apoptotic cells in the KDM5B knockdown GCs. In addition, in the KDM5B knockdown GCs, the percentage of GCs blocked at the S phase was increased compared to the NC group, suggesting a critical role of KDM5B in the cell cycle. Moreover, in the KDM5B knockdown GCs, the reactive oxygen species level, the mitochondrial depolarization ratio, and the expression of intracellular phosphorylated histone H2AX (γH2AX) increased, suggesting that knockdown of KDM5B leads to DNA damage, primarily in the form of DNA double-strand breaks (DSBs). Interestingly, we found a down-regulation of MTF1 in the KDM5B knockdown GCs, and the level of cell proliferation, as well as the cell cycle block in the S phase, was improved. In contrast, in the group with both KDM5B knockdown and MTF1 overexpression, the level of ROS, the expression of γH2AX and the number of DNA DSB sites decreased. Taken together, our results suggest that KDM5B inhibits DNA damage and promotes the cell cycle in GCs, which might occur through the up-regulation of MTF1.