New KAT6 inhibitors induce senescence and arrest cancer growth

Ageing microenvironment mediates lymphocyte carcinogenesis and lymphoma drug resistance: From mechanisms to clinical therapy (Review)

Cellular senescence has a complex role in lymphocyte carcinogenesis and drug resistance of lymphomas. Senescent lymphoma cells combine with immunocytes to create an ageing environment that can be reprogrammed with a senescence‑associated secretory phenotype, which gradually promotes therapeutic resistance. Certain signalling pathways, such as the NF‑κB, Wnt and PI3K/AKT/mTOR pathways, regulate the tumour ageing microenvironment and induce the proliferation and progression of lymphoma cells. Therefore, targeting senescence‑related enzymes or their signal transduction pathways may overcome radiotherapy or chemotherapy resistance and enhance the efficacy of relapsed/refractory lymphoma treatments. Mechanisms underlying drug resistance in lymphomas are complex. The ageing microenvironment is a novel factor that contributes to drug resistance in lymphomas. In terms of clinical translation, some senolytics have been used in clinical trials on patients with relapsed or refractory lymphoma. Combining immunotherapy with epigenetic drugs may achieve better therapeutic effects; however, senescent cells exhibit considerable heterogeneity and lymphoma has several subtypes. Extensive research is necessary to achieve the practical application of senolytics in relapsed or refractory lymphomas. This review summarises the mechanisms of senescence‑associated drug resistance in lymphoma, as well as emerging strategies using senolytics, to overcome therapeutic resistance in lymphoma.

EGCG promotes the sensory function recovery in rats after dorsal root crush injury by upregulating KAT6A and inhibiting pyroptosis

Dorsal root injury usually leads to irreversible sensory function loss and lacks effective treatments. (-)-epigallocatechin-3-gallate (EGCG) is reported to exert neuroprotective roles in the nervous systems. However, the function of EGCG in treating dorsal root injury remains unclear. Hence, we built the dorsal root crush injury (DRCI) rat model to be treated with EGCG, followed by the western blot, Enzyme-linked immunosorbent assay, and sensory behavior tests. We observed that EGCG can upregulate the Lysine acetyltransferase 6A (KAT6A) level and inhibit the pyroptosis, indicated by downregulated gasdermin-D, caspase-1, and interleukin 18 protein levels, and alleviate the neuropathic pain, indicated by the decreased paw withdraw threshold in Plantar test and decreased paw withdraw latency in von Frey test, and downregulated calcitonin gene-related peptide, nerve growth factor, and c-Fos protein levels. But EGCG cannot alleviate the neuropathic pain when the KAT6A was inhibited by CTX-0124143 and pyroptosis was activated by Miltirone. These combined results indicated that EGCG can promote the sensory function recovery in rats after DRCI via upregulating KAT6A and inhibiting pyroptosis, laying the foundation for EGCG to be a novel candidate for the treatment of dorsal root injury.

Matrix stiffness-induced upregulation of histone acetyltransferase KAT6A promotes hepatocellular carcinoma progression through regulating SOX2 expression

BACKGROUND

Lysine acetyltransferase 6 A (KAT6A) is a MYST-type histone acetyltransferase (HAT) enzyme, which contributes to histone modification and cancer development. However, its biological functions and molecular mechanisms, which respect to hepatocellular carcinoma (HCC), are still largely unknown.

METHODS

Immunohistochemical, western blot and qRT-PCR analysis of KAT6A were performed. A series of in vitro and in vivo experiments were conducted to reveal the role of KAT6A in the progression of HCC.

RESULTS

We demonstrated that KAT6A expression was upregulated in HCC tissues and cell lines. Clinical analysis showed that increased KAT6A was significantly associated with malignant prognostic features and shorter survival. Gain- and loss-of-function experiments indicated that KAT6A promoted cell viability, proliferation and colony formation of HCC cells in vitro and in vivo. We confirmed that KAT6A acetylates lysine 23 of histone H3 (H3K23), and then enhances the association of the nuclear receptor binding protein TRIM24 and H3K23ac. Consequently, TRIM24 functions as a transcriptional activator to activate SOX2 transcription and expression, leading to HCC tumorigenesis. Restoration of SOX2 at least partially abolished the biological effects of KAT6A on HCC cells. Overexpression of KAT6A acetyltransferase activity-deficient mutants or TRIM24 mutants lacking H3K23ac binding sites did not affect SOX2 expression and HCC biological function. Moreover, matrix stiffness can upregulate the expression of KAT6A in HCC cells.

CONCLUSIONS

Our data support the first evidence that KAT6A plays an oncogenic role in HCC through H3K23ac/TRIM24-SOX2 pathway, and represents a promising therapeutic strategy for HCC patients.

Low Expression of KAT6B May Affect Prognosis in Hepatocellular Carcinoma

Aims:

Lysine acetyltransferase 6B (KAT6B), is a histone acetyltransferase implicated to have a role in tumor suppression. However, the relationship between KAT6B and hepatocellular carcinoma (HCC) is unclear. The purpose of this study was to detect the expression of KAT6B in HCC tissues and analyze its connection with the clinicopathological features of HCC.

Methods:

First, we performed immunohistochemical staining on 250 HCC tissues and 222 non-tumor liver tissues to examine the expression of KAT6B.Then the relation between KAT6B expression and clinicopathological parameters was analyzed by chi-square test, and the overall survival analysis was conducted by Kaplan-Meier survival method. In addition, based on the Oncomine expression array online and the UALCAN database, we compared KAT6B expression differences between normal liver tissues and HCC tissues more broadly.

Results:

Compared with normal tissues, KAT6B expression was significantly lower in HCC tissues. Low KAT6B expression was found to be related to gender, AFP level, and tumor size. According to the online database, KAT6B expression was found to be decreased in HCC tissues and high in normal tissues.

Conclusions:

Lower expression of KAT6B is associated with poor prognosis of HCC, and KAT6B may be a potential tumor suppressor in liver cancer.

The key roles of the lysine acetyltransferases KAT6A and KAT6B in physiology and pathology

Histone modifications and more specifically ε-lysine acylations are key epigenetic regulators that control chromatin structure and gene transcription, thereby impacting on various important cellular processes and phenotypes. Furthermore, lysine acetylation of many non-histone proteins is involved in key cellular processes including transcription, DNA damage repair, metabolism, cellular proliferation, mitosis, signal transduction, protein folding, and autophagy. Acetylation affects protein functions through multiple mechanisms including regulation of protein stability, enzymatic activity, subcellular localization, crosstalk with other post-translational modifications as well as regulation of protein-protein and protein-DNA interactions. The paralogous lysine acetyltransferases KAT6A and KAT6B which belong to the MYST family of acetyltransferases, were first discovered approximately 25 years ago. KAT6 acetyltransferases acylate both histone H3 and non-histone proteins. In this respect, KAT6 acetyltransferases play key roles in regulation of transcription, various developmental processes, maintenance of hematopoietic and neural stem cells, regulation of hematopoietic cell differentiation, cell cycle progression as well as mitosis. In the current review, we discuss the physiological functions of the acetyltransferases KAT6A and KAT6B as well as their functions under pathological conditions of aberrant expression, leading to several developmental syndromes and cancer. Importantly, both upregulation and downregulation of KAT6 proteins was shown to play a role in cancer formation, progression, and therapy resistance, suggesting that they can act as oncogenes or tumor suppressors. We also describe reciprocal regulation of expression between KAT6 proteins and several microRNAs as well as their involvement in cancer formation, progression and resistance to therapy.

Role of histone acetyltransferase inhibitors in cancer therapy

The development of cancer is a complex phenomenon driven by various extrinsic as well as intrinsic risk factors including epigenetic modifications. These post-translational modifications are encountered in diverse cancer cells and appear for a relatively short span of time. These changes can significantly affect various oncogenic genes and proteins involved in cancer initiation and progression. Histone lysine acetylation and deacetylation processes are controlled by two opposing classes of enzymes that modulate gene regulation either by adding an acetyl moiety on a histone lysine residue by histone lysine acetyltransferases (KATs) or via removing it by histone deacetylases (KDACs). Deregulated KAT activity has been implicated in the development of several diseases including cancer and can be targeted for the development of anti-neoplastic drugs. Here, we describe the predominant epigenetic changes that can affect key KAT superfamily members during carcinogenesis and briefly highlight the pharmacological potential of employing lysine acetyltransferase inhibitors (KATi) for cancer therapy.