Sirt1 modulates H3 phosphorylation and facilitates osteosarcoma cell autophagy

AIF1 + CSF1R + MSCs, induced by TNF-α, act to generate an inflammatory microenvironment and promote hepatocarcinogenesis

BACKGROUND AND AIMS

Increasing evidence suggests that mesenchymal stem cells (MSCs) home to injured local tissues and the tumor microenvironment in the liver. Chronic inflammation is regarded as the major trait of primary liver cancer. However, the characteristics of endogenous MSCs in the inflammatory environment and their role in the occurrence of liver cancer remain obscure.

APPROACH AND RESULTS

Using single-cell RNA sequencing, we identified a distinct inflammation-associated subset of MSCs, namely AIF1 + CSF1R + MSCs, which existed in the microenvironment before the occurrence of liver cancer. Furthermore, we found that this MSC subgroup is likely to be induced by TNF-α stimulation through the TNFR1/SIRT1 (sirtuin 1) pathway. In a rat primary liver cancer model, we showed that MSCs with high SIRT1 expression (Ad-Sirt1-MSCs) promoted macrophage recruitment and synergistically facilitated liver cancer occurrence by secreting C-C motif chemokine ligand (CCL) 5. Interestingly, depletion of macrophages or knockdown of CCL5 expression in Ad-Sirt1-MSCs attenuated the promotive effect of Ad-Sirt1-MSCs on liver inflammation and hepatocarcinogenesis (HCG). Finally, we demonstrated that SIRT1 up-regulated CCL5 expression through activation of the AKT/HIF1α signaling axis in MSCs.

CONCLUSIONS

Together, our results show that MSCs, which are mobilized to the injured site, can be educated by macrophages. In turn, the educated MSCs are involved in generating a chronic inflammatory microenvironment and promoting HCG.

Epigenetic Changes Associated with Osteosarcoma: A Comprehensive Review

Osteosarcoma is the most common malignant primary bone tumor in children and adolescents. While clinical outcomes have improved, the 5-year survival rate is only around 60% if discovered early and can require debilitating treatments, such as amputations. A better understanding of the disease could lead to better clinical outcomes for patients with osteosarcoma. One promising avenue of osteosarcoma research is in the field of epigenetics. This research investigates changes in genetic expression that occur above the genome rather than in the genetic code itself. The epigenetics of osteosarcoma is an active area of research that is still not fully understood. In a narrative review, we examine recent advances in the epigenetics of osteosarcoma by reporting biomarkers of DNA methylation, histone modifications, and non-coding RNA associated with disease progression. We also show how cancer tumor epigenetic profiles are being used to predict and improve patient outcomes. The papers in this review cover a large range of epigenetic target genes and pathways that modulate many aspects of osteosarcoma, including but not limited to metastases and chemotherapy resistance. Ultimately, this review will shed light on the recent advances in the epigenetics of osteosarcoma and illustrate the clinical benefits of this field of research.

Sirtuins' control of autophagy and mitophagy in cancer

Mammalian cells use a specialized and complex machinery for the removal of altered proteins or dysfunctional organelles. Such machinery is part of a mechanism called autophagy. Moreover, when autophagy is specifically employed for the removal of dysfunctional mitochondria, it is called mitophagy. Autophagy and mitophagy have important physiological implications and roles associated with cellular differentiation, resistance to stresses such as starvation, metabolic control and adaptation to the changing microenvironment. Unfortunately, transformed cancer cells often exploit autophagy and mitophagy for sustaining their metabolic reprogramming and growth to a point that autophagy and mitophagy are recognized as promising targets for ongoing and future antitumoral therapies. Sirtuins are NAD+ dependent deacylases with a fundamental role in sensing and modulating cellular response to external stresses such as nutrients availability and therefore involved in aging, oxidative stress control, inflammation, differentiation and cancer. It is clear, therefore, that autophagy, mitophagy and sirtuins share many common aspects to a point that, recently, sirtuins have been linked to the control of autophagy and mitophagy. In the context of cancer, such a control is obtained by modulating transcription of autophagy and mitophagy genes, by post translational modification of proteins belonging to the autophagy and mitophagy machinery, by controlling ROS production or major metabolic pathways such as Krebs cycle or glutamine metabolism. The present review details current knowledge on the role of sirtuins, autophagy and mitophagy in cancer to then proceed to discuss how sirtuins can control autophagy and mitophagy in cancer cells. Finally, we discuss sirtuins role in the context of tumor progression and metastasis indicating glutamine metabolism as an example of how a concerted activation and/or inhibition of sirtuins in cancer cells can control autophagy and mitophagy by impinging on the metabolism of this fundamental amino acid.

Activation of sirtuin1 protects against ischemia/reperfusion-induced acute kidney injury

Sirtuin1 (SIRT1), a class III histone deacetylase, exerts a protective role against kidney injury. However, its functions in renal ischemia/reperfusion (I/R) injury remains unclear as yet. In this study, we established acute kidney injury (AKI) rat model through renal ischemia and reperfusion, and the role of SIRT1 in I/R-induced AKI was investigated both in vivo and in vitro. In in vivo study, SIRT1 was expressed in tubular epithelial cells (TECs) and its expression was upregulated after I/R treatment. Meanwhile, our in vitro experiment confirmed that the expression of SIRT1 was also elevated in human renal proximal tubular epithelial (HK2) cells treated with hypoxia and reoxygenation (H/R). Notably, activation of SIRT1 by resveratrol (Res, an activator of SIRT1) could significantly ameliorate renal function and reduce the TECs apoptosis in rats. Likewise, Res intervention also reduced the apoptosis and the production of reactive oxygen species in HK2 cells. Furthermore, we found that the autophagy level was upregulated in I/R injury, which could be raised further through resveratrol intervention; and chloroquine (CQ, an autophagy inhibitor) did reverse these protective effects of SIRT1 activation. Taken together, our results suggest that SIRT1 plays a protective role by autophagy induction in I/R- induced AKI. Its role might serve as a preventive approach in I/R-associated AKI.