Cytoplasmic localization of SETDB1‑induced Warburg effect via c‑MYC‑LDHA axis enhances migration and invasion in breast carcinoma

Estrogen increases Setdb1 cytoplasmic localization to stabilize Serpinh1 and improve protein homeostasis in osteoblasts

Estrogen regulates osteoblast activity at the epigenetic level. Setdb1 is an epigenetic regulator that functions in skeleton homeostasis maintenance. Setdb1 shows nuclear and cytoplasm localization in cells; however, the subcellular distribution of Setdb1 and the role of cytoplasmic Setdb1 in osteoblasts are largely unknown. Here, immunofluorescence staining and immunoblotting analysis showed that the distribution of Setdb1 in the cytoplasm increased upon β-estradiol treatment by increasing nuclear Setdb1 stability in osteoblasts. In β-estradiol-treated MC3T3-E1 cells, knocking-down Atf7ip expression enhanced Setdb1 cytoplasmic localization, but the cytoplasmic distribution of Setdb1 decreased in cells treated with the Setdb1 inhibitor (R,R)-59. Moreover, ovariectomized (OVX) mice lacking Atf7ip in mature osteoblasts showed better bone microstructure than the OVX controls. The proteomic analysis of the cytoplasmic binding of Setdb1 showed that cytoplasmic Setdb1 in osteoblasts mainly functioned to regulate protein homeostasis. Setdb1 binds to Serpinh1, a regulator of pro-collagen folding and maturation, and enhances Serpinh1 stability. Interrupting Setdb1 cytoplasmic localization by treating the cells with Leptomycin B (LMB) or (R,R)-59 led to an accumulation of unfolded protein and the elicitation of endoplasmic reticulum (ER) stress. The findings revealed a previously unrecognized role of cytoplasmic Setdb1 in the regulation of β-estradiol-mediated osteoblast homeostasis, which could enhance the understanding of estrogen's mechanism of action in regulating osteoblasts.

Research progress on the regulatory role of lactate and lactylation in tumor microenvironment

The tumor microenvironment (TME) arises from the dynamic interactions between tumor cells and the surrounding medium, including a variety of cell types and extracellular components, which have an important impact on the genesis and development of tumors. A key player in TME is lactate, a metabolic byproduct of glycolysis, which serves as a significant energy source. Lactate has direct implications on the survival and differentiation of immune cells, the metabolic reprogramming and progression of tumor cells. Moreover, lactylation, a unique post-translational modification, exerts a regulatory effect on TME by affecting gene transcription via adding lactate groups to both histone and non-histone proteins. This review systematically and comprehensively synthesizes emerging evidence on how the lactate-lactylation axis drives immune evasion, therapy resistance, and TME remodeling, highlighting the therapeutic targets related to lactate and lactylation that dismantle this metabolic-epigenetic crosstalk.

Lactate Dehydrogenase-A-Forming LDH5 Promotes Breast Cancer Progression

Background

Breast cancer (BC) has become the main malignant tumor threatening the health of women worldwide. Previous studies have reported that Lactate dehydrogenase-A (LDHA) has critical roles in cancer development and progression. We aimed to explore the roles of LDHA and LDH5 isoenzyme activity in BC, which provides a new insight into LDHA for the treatment of BC.

Methods

The expression of LDHA in BC and its relationship with clinicopathological features were obtained from various databases including The Cancer Genome Atlas (TCGA), Human Protein Atlas (HPA), Breast Cancer-Gene Expression Miner (bc-GenExMiner), TNMplot, UALCAN. The Kaplan‒Meier Plotter was used to evaluate the prognostic value of LDHA. Western blot was performed to detect LDHA expression. Agarose gel electrophoresis was performed to detect the activities of LDH isoenzymes. The in vitro proliferation, migration and invasion potentials of BC cells were evaluated using MTT assays, colony formation, wound-healing assay, matrix metalloproteinase assays and transwell assays, respectively. The activities of LDH isoenzymes in serum and tissues were measured in patients with BC and healthy controls.

Results

Compared to normal tissues, LDHA expression was significantly higher in BC tissues. Patients' nodal status, histological types, TP53 mutation status and PAM50 subtypes were significant factors influencing the LDHA expression. By overexpressing or silencing LDHA gene in BT549 cells, it was confirmed that LDHA promoted cell proliferation, migration and invasion. LDH5 isoenzyme activity in patients with BC was higher than healthy controls. The increased activity of LDH5 isoenzymes was induced by overexpression of LDHA in BC. High expression of LDHA was found to be associated with poor prognosis in BC.

Conclusion

LDHA plays a critical role in the progression of BC through the regulation of the activity of LDH5 isoenzyme, indicating that LDHA may serve as a valuable target for BC treatment.

Deciphering the oncogenic network: how C1QTNF1-AS1 modulates osteosarcoma through miR-34a-5p and glycolytic pathways

Introduction

Osteosarcoma (OS), a prevalent metastatic cancer among young individuals, is associated with a grim prognosis. Long non-coding RNAs (lncRNAs), including C1QTNF1-AS1, are pivotal regulators of cancer cell proliferation and motility. As an oncogene, C1QTNF1-AS1 is implicated in various tumor types, such as colorectal, pancreatic, hepatocellular carcinomas, and OS. The aim of this study was to investigate the functions and underlying mechanisms of C1QTNF1-AS1 in the progression of osteosarcoma.

Methods

This investigation focused on elucidating the functional roles and mechanisms of C1QTNF1-AS1 in OS cells. Bioinformatics tools were utilized to identify the interaction between microRNA miR-34a-5p and C1QTNF1-AS1, as well as the targeting of LDHA and PDK3 by miR-34a-5p. Dual-luciferase reporter assays and RNA immunoprecipitation were employed to validate these interactions. Expression profiles of C1QTNF1-AS1, miR-34a-5p, LDHA, and PDK3 in osteosarcoma cells were analyzed using RT-PCR and western blot analyses, revealing their intricate relationships. The impact of these molecules on OS cell proliferation, invasion, and migration was assessed through CCK-8, Transwell, and Cell scratch assay. Moreover, the effects on aerobic glycolysis in OS cells were examined by quantifying ATP levels, lactate production, glucose uptake capacity, and the extracellular acidification rate.

Results

The findings indicated a significant decrease in C1QTNF1-AS1 expression levels in OS cells compared to normal osteoblasts. A parallel downregulation trend of miR-34a-5p was also observed in OS cells. Silencing C1QTNF1-AS1 led to a marked upregulation of LDHA and PDK3 in OS cells, which was partially attenuated by miR-34a-5p mimics. Functional evaluations demonstrated that suppression of C1QTNF1-AS1 accelerated OS cell growth, motility, invasiveness, and the Warburg effect. Conversely, the overexpression of miR-34a-5p mitigated these stimulatory effects, suggesting a regulatory role in modulating OS progression.

Discussion

Our research emphasizes the critical role of C1QTNF1-AS1 in the pathogenesis of osteosarcoma (OS). We discovered that the downregulation of C1QTNF1-AS1 indirectly upregulates the expression of LDHA and PDK3 by suppressing miR-34a-5p, which functions as a regulator of the Warburg effect. This cascade of events promotes OS progression by enhancing glycolytic metabolism and supplying energy for cancer cell growth, migration, and invasion. These findings suggest a potential therapeutic target and highlight the importance of understanding the regulatory network involving lncRNAs in cancer metabolism and progression.

SETDB1, an H3K9-specific methyltransferase: An attractive epigenetic target to combat cancer

SET domain bifurcated histone lysine methyltransferase 1 (SETDB1) is an important epigenetic regulator catalyzing histone H3 lysine 9 (H3K9) methylation, specifically di-/tri-methylation. This regulation promotes gene silencing through heterochromatin formation. Aberrant SETDB1 expression, and its oncogenic role is evident in many cancers. Thus, SETDB1 is a valid target with novel therapeutic benefits. In this review, we explore the structural and biochemical features of SETDB1, its regulatory mechanisms, and its role in various cancers. We also discuss recent discoveries in small molecules targeting SETDB1 and provide suggestions for future research.