The dynamic side of the Warburg effect: glycolytic intermediate storage as buffer for fluctuating glucose and O 2 supply in tumor cells

Pyruvate Kinase Differentially Alters Metabolic Signatures during Head and Neck Carcinogenesis

During glycolysis, the muscle isoform of pyruvate kinase PKM2 produces ATP in exchange for dephosphorylation of phosphoenolpyruvate (PEP) into pyruvate. PKM2 has been considered as a tumor-promoting factor in most cancers, whereas the regulatory role of PKM2 during head and neck carcinogenesis remained to be delineated. PKM2 mRNA and protein expression was examined in head and neck tumorous specimens. The role of PKM2 in controlling cellular malignancy was determined in shRNA-mediated PKM2-deficient head and neck squamous cell carcinoma (HNSC) cells. In agreement with the results in other cancers, PKM2 expression is enriched in both mouse and human HNSC tissues. Nevertheless, PKM2 mRNA expression reversely correlated with tumor stage, and greater recurrence-free survival rates are evident in the PKM2high HNSC population, arguing that PKM2 may be tumor-suppressive. Multifaceted analyses showed a greater in vivo xenografic tumor growth and an enhanced cisplatin resistance in response to PKM2 loss, whereas PKM2 silencing led to reduced cell motility. At the molecular level, metabolic shifts towards mitochondrial metabolism and activation of oncogenic Protein kinase B (PKB/Akt) and extracellular signal-regulated kinase (ERK) signals were detected in PKM2-silencing HNSC cells. In sum, our findings demonstrated that PKM2 differentially modulated head and neck tumorigenicity via metabolic reprogramming.

Construction and evaluation of curcumin upconversion nanocarriers decorated with MnO2 for tumor photodynamic therapy

The limited tissue penetration depth and tumor hypoxic microenvironment have become the two pivotal obstacles that alleviate the antineoplastic efficacy in tumor photodynamic therapy (PDT). In the research, MnO₂-decorated upconversion nanoparticles (UCSMn) have been designed to generate certain oxygen within the solid tumor, and also increase the light penetrating depth due to the optical conversion ability derived from upconversion nanoparticles. Furthermore, upconversion nanoparticles as the inner core are coated by mesoporous silica for the loading of curcumin as photosensitizer and chemotherapeutics, and then a MnO₂ shell is proceeding to grow via redox method. When reaching the tumor tissue, the MnO₂ nanoshells of UCSMn could be rapidly degraded into manganese ions (Mn²⁺) owing to the reaction with H₂O₂ in acidic tumor microenvironment, meanwhile producing oxygen and facilitating curcumin release. Once the tumor is illuminated by 980 nm light, the upconversion nanoparticles can transform the infrared light to visible light of 450 nm and 475.5 nm, which can be efficiently absorbed by curcumin, and then produce singlet oxygen to induce tumor cell apoptosis. Curcumin played a dual role which can not only be acted as a photosensitizer, but also a chemotherapeutic agent to further reinforce the antitumor activity. In short, the intelligent nanostructure has the potential to overcome the above-mentioned shortcomings existed in PDT and eventually do work well in the hypoxia tumors. MnO₂-decorated upconversion nanoparticle to solve the tissue penetration and tumor hypoxic microenvironment for tumor photodynamic therapy.

Acidic and Hypoxic Microenvironment in Melanoma: Impact of Tumour Exosomes on Disease Progression

The mechanisms of melanoma progression have been extensively studied in the last decade, and despite the diagnostic and therapeutic advancements pursued, malignant melanoma still accounts for 60% of skin cancer deaths. Therefore, research efforts are required to better define the intercellular molecular steps underlying the melanoma development. In an attempt to represent the complexity of the tumour microenvironment (TME), here we analysed the studies on melanoma in acidic and hypoxic microenvironments and the interactions with stromal and immune cells. Within TME, acidity and hypoxia force melanoma cells to adapt and to evolve into a malignant phenotype, through the cooperation of the tumour-surrounding stromal cells and the escape from the immune surveillance. The role of tumour exosomes in the intercellular crosstalk has been generally addressed, but less studied in acidic and hypoxic conditions. Thus, this review aims to summarize the role of acidic and hypoxic microenvironment in melanoma biology, as well as the role played by melanoma-derived exosomes (Mexo) under these conditions. We also present a perspective on the characteristics of acidic and hypoxic exosomes to disclose molecules, to be further considered as promising biomarkers for an early detection of the disease. An update on the use of exosomes in melanoma diagnosis, prognosis and response to treatment will be also provided and discussed.

Lactate Metabolism and Signaling in Tuberculosis and Cancer: A Comparative Review

Infection with Mycobacterium tuberculosis (Mtb) leading to tuberculosis (TB) disease continues to be a major global health challenge. Critical barriers, including but not limited to the development of multi-drug resistance, lack of diagnostic assays that detect patients with latent TB, an effective vaccine that prevents Mtb infection, and infectious and non-infectious comorbidities that complicate active TB, continue to hinder progress toward a TB cure. To complement the ongoing development of new antimicrobial drugs, investigators in the field are exploring the value of host-directed therapies (HDTs). This therapeutic strategy targets the host, rather than Mtb, and is intended to augment host responses to infection such that the host is better equipped to prevent or clear infection and resolve chronic inflammation. Metabolic pathways of immune cells have been identified as promising HDT targets as more metabolites and metabolic pathways have shown to play a role in TB pathogenesis and disease progression. Specifically, this review highlights the potential role of lactate as both an immunomodulatory metabolite and a potentially important signaling molecule during the host response to Mtb infection. While long thought to be an inert end product of primarily glucose metabolism, the cancer research field has discovered the importance of lactate in carcinogenesis and resistance to chemotherapeutic drug treatment. Herein, we discuss similarities between the TB granuloma and tumor microenvironments in the context of lactate metabolism and identify key metabolic and signaling pathways that have been shown to play a role in tumor progression but have yet to be explored within the context of TB. Ultimately, lactate metabolism and signaling could be viable HDT targets for TB; however, critical additional research is needed to better understand the role of lactate at the host-pathogen interface during Mtb infection before adopting this HDT strategy.