Role of Intra- and Extracellular Lipid Signals in Cancer Stemness and Potential Therapeutic Strategy

Metabolic adaptations in cancer stem cells: A key to therapy resistance

Cancer stem cells (CSCs) are a subset of tumor cells that can initiate and sustain tumor growth and cause recurrence and metastasis. CSCs are particularly resistant to conventional therapies compared to their counterparts, owing greatly to their intrinsic metabolic plasticity. Metabolic plasticity allows CSCs to switch between different energy production and usage pathways based on environmental and extrinsic factors, including conditions imposed by conventional cancer therapies. To cope with nutrient deprivation and therapeutic stress, CSCs can transpose between glycolysis and oxidative phosphorylation (OXPHOS) metabolism. The mechanism behind the metabolic pathway switch in CSCs is not fully understood, however, some evidence suggests that the tumor microenvironment (TME) may play an influential role mediated by its release of signals, such as Wnt/β-catenin and Notch pathways, as well as a background of hypoxia. Exploring the factors that promote metabolic plasticity in CSCs offers the possibility of eventually developing therapies that may more effectively eliminate the crucial tumor cell subtype and alter the disease course substantially.

The lipid droplet in cancer: From being a tumor-supporting hallmark to clinical therapy

INTRODUCTION

Abnormal lipid metabolism, one of the hallmarks in cancer, has gradually emerged as a novel target for cancer treatment. As organelles that store and release excess lipids, lipid droplets (LDs) resemble "gears" and facilitate cancer development in the body.

AIM

This review discusses the life cycle of LDs, the relationship between abnormal LDs and cancer hallmarks, and the application of LDs in theragnostic and clinical contexts to provide a contemporary understanding of the role of LDs in cancer.

METHODS

A systematic literature search was conducted in PubMed and SPORTDiscus. Retrieve and summarize clinical trials of drugs that target proteins associated with LD formation using the Clinical Trials website. Create a schematic diagram of lipid droplets in the tumor microenvironment using Adobe Illustrator.

CONCLUSION

As one of the top ten hallmarks of cancer, abnormal lipid metabolism caused by excessive generation of LDs interrelates with other hallmarks. The crosstalk between excessive LDs and intracellular free fatty acids (FFAs) promotes an inflammatory environment that supports tumor growth. Moreover, LDs contribute to cancer metastasis and cell death resistance in vivo. Statins, as HMGCR inhibitors, are promising to be the pioneering commercially available anti-cancer drugs that target LD formation.

Role of the bone marrow microenvironment in multiple myeloma treatment using CAR-T therapy

INTRODUCTION

Multiple myeloma (MM) is a malignant tumor caused by abnormal proliferation of bone marrow (BM) plasma cells and is the second most common hematologic malignancy. A variety of CAR-T cells targeting multiple myeloma-specific markers have shown good efficacy in clinical trials. However, CAR-T therapy still limits the insufficient duration of efficacy and recurrence of the disease.

AREAS COVERED

This article reviews the cell populations in the bone marrow of MM, and discusses the potential way to improve the efficiency of CAR-T cells in the treatment of MM by targeting the bone marrow microenvironment.

EXPERT OPINION

The limits of CAR-T therapy in MM may related to the impairment of T cell activity in the bone marrow microenvironment. This article reviews the cell populations of the immune microenvironment and nonimmune microenvironment in the bone marrow of multiple myeloma, and discusses the potential way to improve the efficiency of CAR-T cells in the treatment of MM by targeting the bone marrow. This may provides a new idea for the CAR-T therapy of multiple myeloma.

Evolving Diagnostic and Treatment Strategies for Pediatric CNS Tumors: The Impact of Lipid Metabolism

Pediatric neurological tumors are a heterogeneous group of cancers, many of which carry a poor prognosis and lack a "standard of care" therapy. While they have similar anatomic locations, pediatric neurological tumors harbor specific molecular signatures that distinguish them from adult brain and other neurological cancers. Recent advances through the application of genetics and imaging tools have reshaped the molecular classification and treatment of pediatric neurological tumors, specifically considering the molecular alterations involved. A multidisciplinary effort is ongoing to develop new therapeutic strategies for these tumors, employing innovative and established approaches. Strikingly, there is increasing evidence that lipid metabolism is altered during the development of these types of tumors. Thus, in addition to targeted therapies focusing on classical oncogenes, new treatments are being developed based on a broad spectrum of strategies, ranging from vaccines to viral vectors, and melitherapy. This work reviews the current therapeutic landscape for pediatric brain tumors, considering new emerging treatments and ongoing clinical trials. In addition, the role of lipid metabolism in these neoplasms and its relevance for the development of novel therapies are discussed.

Targeting autophagy and lipid metabolism in cancer stem cells

Cancer stem cells (CSCs) are a subset of cancer cells with self-renewal ability and tumor initiating properties. Unlike the other non-stem cancer cells, CSCs resist traditional therapy and remain a major cause of disease relapse. With the recent advances in metabolomics, various studies have demonstrated that CSCs have distinct metabolic properties. Metabolic reprogramming in CSCs contributes to self-renewal and maintenance of stemness. Accumulating evidence suggests that rewiring of energy metabolism is a key player that enables to meet energy demands, maintains stemness, and sustains cancer growth and invasion. CSCs use various mechanisms such as increased glycolysis, redox signaling and autophagy modulation to overcome nutritional deficiency and sustain cell survival. The alterations in lipid metabolism acquired by the CSCs support biomass production through increased dependence on fatty acid synthesis and β-oxidation and contribute to oncogenic signaling pathways. This review summarizes our current understanding of lipid metabolism in CSCs and how pharmacological regulation of autophagy and lipid metabolism influences CSC phenotype. Increased dependence on lipid metabolism appears as an attractive strategy to eliminate CSCs using therapeutic agents that specifically target CSCs based on their modulation of lipid metabolism.

Resveratrol suppresses lung cancer by targeting cancer stem-like cells and regulating tumor microenvironment

Increasing evidence indicate that cancer stem cells (CSCs) are the key driver of tumor initiation and recurrence. The cellular and soluble components of the tumor microenvironment (TME) impact on cancer initiation and progression, such as cytokines and chemokines. Thus, targeting CSCs and TME is a novel anti-cancer approach. Resveratrol (RES), a bioactive phytochemical extracted from various plants, exhibits tumor-suppressing activities in lung cancer, yet the mechanism remains poorly understood. Our data showed that the expression level of IL-6 was positively correlated with the presence of lung cancer stem-like cells (LCSCs) in human lung cancer tissues. In vitro results showed that IL-6 was highly elevated in lung cancer sphere-forming cells and could enhance the stemness of LCSCs, including tumor sphere formation ability, the percentage of CD133 positive cells, and the expression of LCSC specific markers (CD133, ALDH1A1 and Nanog). Simultaneously, our results confirmed that RES effectively inhibited LCSC properties, downregulated Wnt/β-catenin signaling and reduced IL-6 level in vitro and in vivo. Furthermore, we found RES treatment attenuated the activation of Wnt/β-catenin signaling by LiCl (GSK3β agonist). IL-6-promoted LCSC properties and Wnt/β-catenin signaling was also reversed by RES. Taken together, these data illustrated that RES inhibited lung cancer by targeting LCSCs and IL-6 in TME. The novel findings from this study provided evidence that RES exhibited multi-target effects on suppression of lung cancer and could be a novel potent cancer-preventive compound.

Metabolic Reprogramming in Cancer Cells: Emerging Molecular Mechanisms and Novel Therapeutic Approaches

The constant changes in cancer cell bioenergetics are widely known as metabolic reprogramming. Reprogramming is a process mediated by multiple factors, including oncogenes, growth factors, hypoxia-induced factors, and the loss of suppressor gene function, which support malignant transformation and tumor development in addition to cell heterogeneity. Consequently, this hallmark promotes resistance to conventional anti-tumor therapies by adapting to the drastic changes in the nutrient microenvironment that these therapies entail. Therefore, it represents a revolutionary landscape during cancer progression that could be useful for developing new and improved therapeutic strategies targeting alterations in cancer cell metabolism, such as the deregulated mTOR and PI3K pathways. Understanding the complex interactions of the underlying mechanisms of metabolic reprogramming during cancer initiation and progression is an active study field. Recently, novel approaches are being used to effectively battle and eliminate malignant cells. These include biguanides, mTOR inhibitors, glutaminase inhibition, and ion channels as drug targets. This review aims to provide a general overview of metabolic reprogramming, summarise recent progress in this field, and emphasize its use as an effective therapeutic target against cancer.

Mechanism of cancer stemness maintenance in human liver cancer

Primary liver cancer mainly includes the following four types: hepatocellular carcinoma (HCC), cholangiocarcinoma (CCA), hepatoblastoma (HB), and combined hepatocellular carcinoma and cholangiocarcinoma (cHCC-CCA). Recent studies have indicated that there are differences in cancer stem cell (CSC) properties among different types of liver cancer. Liver cancer stem cells (LCSCs), also called liver tumor-initiating cells, have been viewed as drivers of tumor initiation and metastasis. Many mechanisms and factors, such as mitophagy, mitochondrial dynamics, epigenetic modifications, the tumor microenvironment, and tumor plasticity, are involved in the regulation of cancer stemness in liver cancer. In this review, we analyze cancer stemness in different liver cancer types. Moreover, we further evaluate the mechanism of cancer stemness maintenance of LCSCs and discuss promising treatments for eradicating LCSCs.

Effects of the Combined Treatment with a G-Quadruplex-Stabilizing Ligand and Photon Beams on Glioblastoma Stem-like Cells: A Magnetic Resonance Study

Glioblastoma multiforme is a malignant primary brain tumor with a poor prognosis and high rates of chemo-radiotherapy failure, mainly due to a small cell fraction with stem-like properties (GSCs). The mechanisms underlying GSC response to radiation need to be elucidated to enhance sensitivity to treatments and to develop new therapeutic strategies. In a previous study, two GSC lines, named line #1 and line #83, responded differently to carbon ions and photon beams, with the differences likely attributable to their own different metabolic fingerprint rather than to radiation type. Data from the literature showed the capability of RHPS4, a G-quadruplex stabilizing ligand, to sensitize the glioblastoma radioresistant U251MG cells to X-rays. The combined metabolic effect of ligand #190, a new RHPS4-derivative showing reduced cardiotoxicity, and a photon beam has been monitored by magnetic resonance (MR) spectroscopy for the two GSC lines, #1 and #83, to reveal whether a synergistic response occurs. MR spectra from both lines were affected by single and combined treatments, but the variations of the analysed metabolites were statistically significant mainly in line #1, without synergistic effects due to combination. The multivariate analysis of ten metabolites shows a separation between control and treated samples in line #1 regardless of treatment type, while separation was not detected in line #83.