Inhibition of PGC-1α after chemotherapy-mediated insult confines multiple myeloma cell survival by affecting ROS accumulation

Modulation of Cellular Redox Parameters for Improving Therapeutic Responses in Multiple Myeloma

Raised oxidative stress and abnormal redox status are typical features of multiple myeloma cells, and the identification of the intimate mechanisms that regulate the relationships between neoplastic cells and redox homeostasis may reveal possible new anti-myeloma therapeutic targets to increase the effectiveness of anti-myeloma drugs synergistically or to eradicate drug-resistant clones while reducing toxicity toward normal cells. An alteration of the oxidative state is not only responsible for the onset of multiple myeloma and its progression, but it also appears essential for the therapeutic response and for developing any chemoresistance. Our review aimed to evaluate the literature’s current data on the effects of oxidative stress on the response to drugs generally employed in the therapy of multiple myeloma, such as proteasome inhibitors, immunomodulators, and autologous transplantation. In the second part of the review, we analyzed the possibility of using other substances, often of natural origin, to modulate the oxidative stress to interfere with the progression of myelomatous disease.

Heritable shifts in redox metabolites during mitochondrial quiescence reprogramme progeny metabolism

Changes in maternal diet and metabolic defects in mothers can profoundly affect health and disease in their progeny. However, the biochemical mechanisms that induce the initial reprogramming events at the cellular level have remained largely unknown owing to limitations in obtaining pure populations of quiescent oocytes. Here, we show that the precocious onset of mitochondrial respiratory quiescence causes a reprogramming of progeny metabolic state. The premature onset of mitochondrial respiratory quiescence drives the lowering of Drosophila oocyte NAD⁺ levels. NAD⁺ depletion in the oocyte leads to reduced methionine cycle production of the methyl donor S-adenosylmethionine in embryos and lower levels of histone H3 lysine 27 trimethylation, resulting in enhanced intestinal lipid metabolism in progeny. In addition, we show that triggering cellular quiescence in mammalian cells and chemotherapy-resistant human cancer cell models induces cellular reprogramming events identical to those seen in Drosophila, suggesting a conserved metabolic mechanism in systems reliant on quiescent cells.

SR18292 exerts potent antitumor effects in multiple myeloma via inhibition of oxidative phosphorylation

AIMS

Multiple myeloma (MM) was recently reported to rely on increased oxidative phosphorylation (OXPHOS) for survival, providing a potential opportunity for MM therapy. Herein, we aimed to propose a novel targeted drug for MM treatment, followed by the exploration of reason for OXPHOS enhancement in MM cells.

MATERIALS AND METHODS

The expression of OXPHOS genes and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) was analyzed using bioinformatics analyses, followed by verification in MM cell lines. The effects of SR18292 on OXPHOS were measured by qRT-PCR, Western blot, transmission electron microscopy, oxygen consumption rate and so on. The proliferation and apoptosis were evaluated by CCK-8, flow cytometry and Western blot. The efficiency and safety of SR18292 were assessed in a mouse model of MM.

KEY FINDINGS

The OXPHOS genes were generally overexpressed in MM cells, which was associated with poorer prognosis of MM patients. PGC-1α, a transcriptional coactivator, was upregulated in MM cells, and MM patients with higher PGC-1α expression exhibited increased enrichment of the OXPHOS gene set. Treatment with SR18292 (an inhibitor of PGC-1α) significantly impaired the proliferation and survival of MM cells due to OXPHOS metabolism dysfunction, which leads to energy exhaustion and oxidative damage. Besides, SR18292 potently inhibited tumor growth at a well-tolerated dose in MM model mice.

SIGNIFICANCE

The overexpression of OXPHOS gene set mediated by upregulated PGC-1α provides a structural basis for enhanced OXPHOS in MM cells, and SR18292 (a PGC-1α inhibitor) exerts potent antimyeloma effects, offering a potential tangible avenue for MM therapy.

Cisplatin resistance involves a metabolic reprogramming through ROS and PGC-1α in NSCLC which can be overcome by OXPHOS inhibition

BACKGROUND

Platinum-based chemotherapy remains the standard of care for most lung cancer cases. However chemoresistance is often developed during the treatment, limiting clinical utility of this drug. Recently, the ability of tumor cells to adapt their metabolism has been associated to resistance to therapies. In this study, we first described the metabolic reprogramming of Non-Small Cell Lung Cancer (NSCLC) in response to cisplatin treatment.

METHODS

Cisplatin-resistant versions of the A549, H1299, and H460 cell lines were generated by continuous drug exposure. The long-term metabolic changes, as well as, the early response to cisplatin treatment were analyzed in both, parental and cisplatin-resistant cell lines. In addition, four Patient-derived xenograft models treated with cisplatin along with paired pre- and post-treatment biopsies from patients were studied. Furthermore, metabolic targeting of these changes in cell lines was performed downregulating PGC-1α expression through siRNA or using OXPHOS inhibitors (metformin and rotenone).

RESULTS

Two out of three cisplatin-resistant cell lines showed a stable increase in mitochondrial function, PGC1-α and mitochondrial mass with reduced glycolisis, that did not affect the cell cycle. This phenomenon was confirmed in vivo. Post-treatment NSCLC tumors showed an increase in mitochondrial mass, PGC-1α, and a decrease in the GAPDH/MT-CO1 ratio. In addition, we demonstrated how a ROS-mediated metabolism reprogramming, involving PGC-1α and increased mitochondrial mass, is induced during short-time cisplatin exposure. Moreover, we tested how cells with increased PGC-1a induced by ZLN005 treatment, showed reduced cisplatin-driven apoptosis. Remarkably, the long-term metabolic changes, as well as the metabolic reprogramming during short-time cisplatin exposure can be exploited as an Achilles' heel of NSCLC cells, as demonstrated by the increased sensitivity to PGC-1α interference or OXPHOS inhibition using metformin or rotenone.

CONCLUSION

These results describe a new cisplatin resistance mechanism in NSCLC based on a metabolic reprogramming that is therapeutically exploitable through PGC-1α downregulation or OXPHOS inhibitors.

Pterostilbene inhibits nutrient metabolism and induces apoptosis through AMPK activation in multiple myeloma cells

Multiple myeloma (MM) cells are characterized by an abnormal nutrient metabolism that is distinct from normal plasma cells. Pterostilbene (PTE), a bioactive component of blueberries, has been demonstrated to induce apoptosis in multiple types of cancer cell. The present study evaluated whether PTE treatment affected the survival of MM cells from a metabolic perspective, and the potential mechanisms of this. It was observed that the administration of PTE induced apoptosis, which was mediated by the increased activation of AMP‑activated protein kinase (AMPK). Once activated, AMPK decreased the expression and/or activity of key lipogenic enzymes, including fatty acid synthase and acetyl‑CoA carboxylase. In addition, the activation of AMPK suppressed the downstream substrate, mechanistic target of rapamycin, which dephosphorylated eukaryotic initiation factor 4E‑binding protein 1, leading to a general decrease in mRNA translation. Pre‑treatment with the AMPK inhibitor compound C prior to PTE treatment compromised the anti‑myeloma apoptosis effect, suggesting the critical role of AMPK in mediating PTE‑induced cell toxicity. Consistent results were obtained in vivo. Finally, autophagy was adaptively upregulated subsequent to PTE treatment; the pro‑apoptotic efficacy of PTE was potentiated once autophagic flux was inhibited by 3‑methyladenine. Taken together, these data demonstrated that PTE exerts anti‑tumor effects on MM cells via AMPK‑induced nutrient suppression.

PGC-1 Coactivators: Shepherding the Mitochondrial Biogenesis of Tumors

As coordinators of energy demands and nutritional supplies, the PGC-1 family of transcriptional coactivators regulates mitochondrial biogenesis to control the cellular bioenergetic state. Aside from maintaining normal and adapted cell physiology, recent studies indicate that PGC-1 coactivators also serve important functions in cancer cells. In fact, by balancing mitochondrial energy production with demands for cell proliferation, these factors are involved in almost every step of tumorigenesis. In this review, we discuss the interplay between PGC-1 coactivators and cancer pathogenesis, including tumor initiation, metastatic spread, and response to treatment. Given their involvement in the functional biology of cancers, identification of regulatory targets that influence PGC-1 expression and activity may reveal novel strategies suitable for mono- or combinatorial cancer therapies.

Thymoquinone Inhibits Angiotensin II-Induced Proliferation and Migration of Vascular Smooth Muscle Cells Through the AMPK/PPARγ/PGC-1α Pathway

The proliferation and migration of vascular smooth muscle cells (VSMCs) play crucial roles in the pathogenesis of diabetes and its complications. Thymoquinone (TQ) is the primary bioactive component of Nigella sativa L. seed oil, which exhibits antihyperglycemic effect in diabetic rats, but its role in VSMC proliferation and migration has not been investigated. The results of MTT assay and flow cytometry assay indicated that TQ dose-dependently inhibited angiotensin II (Ang II)-induced VSMCs' cell cycle progression, as well as cyclin D1 expression, whereas p21 expression was altered conversely. TQ dose-dependently suppressed Ang II-induced VSMC migration accompanied by reduced MMP-9 expression. In addition, we observed the elevated reactive oxygen species (ROS) generation and NADPH oxidase activity and reduced superoxide dismutase activity in Ang II-treated VSMCs, which were dose-dependently reversed by TQ. Western blot analysis indicated that TQ dose-dependently restored Ang II-inhibited expression of p-AMPK, PPARγ, and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) proteins. Furthermore, adenosine monophosphate-activated protein kinase (AMPK) inhibitor Compound C and PGC-1α siRNA transfection abrogated the activation of TQ on Ang II-inhibited AMPK/PPARγ/PGC-1α signaling, but abolished the inhibitory effects of TQ on Ang II-induced VSMC proliferation and migration, as well as ROS generation. Taken together, these results demonstrated that TQ inhibited Ang II-induced VSMC proliferation and migration through the AMPK/PPARγ/PGC-1α pathway.

Redox modulation of adipocyte differentiation: hypothesis of "Redox Chain" and novel insights into intervention of adipogenesis and obesity

In view of the global prevalence of obesity and obesity-associated disorders, it is important to clearly understand how adipose tissue forms. Accumulating data from various laboratories implicate that redox status is closely associated with energy metabolism. Thus, biochemical regulation of the redox system may be an attractive alternative for the treatment of obesity-related disorders. In this work, we will review the current data detailing the role of the redox system in adipocyte differentiation, as well as identifying areas for further research. The redox system affects adipogenic differentiation in an extensive way. We propose that there is a complex and interactive "redox chain," consisting of a "ROS-generating enzyme chain," "combined antioxidant chain," and "transcription factor chain," which contributes to fine-tune the regulation of ROS level and subsequent biological consequences. The roles of the redox system in adipocyte differentiation are paradoxical. The redox system exerts a "tridimensional" mechanism in the regulation of adipocyte differentiation, including transcriptional, epigenetic, and posttranslational modulations. We suggest that redoxomic techniques should be extensively applied to understand the biological effects of redox alterations in a more integrated way. A stable and standardized "redox index" is urgently needed for the evaluation of the general redox status. Therefore, more effort should be made to establish and maintain a general redox balance rather than to conduct simple prooxidant or antioxidant interventions, which have comprehensive implications.