Brief Report: Human Mesenchymal Stem-Like Cells Facilitate Floating Tumorigenic Cell Growth via Glutamine-Ammonium Cycle

Insights into the tumor-stromal-immune cell metabolism cross talk in ovarian cancer

The ovarian cancer tumor microenvironment (TME) consists of a constellation of abundant cellular components, extracellular matrix, and soluble factors. Soluble factors, such as cytokines, chemokines, structural proteins, extracellular vesicles, and metabolites, are critical means of noncontact cellular communication acting as messengers to convey pro- or antitumorigenic signals. Vast advancements have been made in our understanding of how cancer cells adapt their metabolism to meet environmental demands and utilize these adaptations to promote survival, metastasis, and therapeutic resistance. The stromal TME contribution to this metabolic rewiring has been relatively underexplored, particularly in ovarian cancer. Thus, metabolic activity alterations in the TME hold promise for further study and potential therapeutic exploitation. In this review, we focus on the cellular components of the TME with emphasis on 1) metabolic signatures of ovarian cancer; 2) understanding the stromal cell network and their metabolic cross talk with tumor cells; and 3) how stromal and tumor cell metabolites alter intratumoral immune cell metabolism and function. Together, these elements provide insight into the metabolic influence of the TME and emphasize the importance of understanding how metabolic performance drives cancer progression.

Concise Review: Therapeutic Potential of the Mesenchymal Stem Cell Derived Secretome and Extracellular Vesicles for Radiation-Induced Lung Injury: Progress and Hypotheses

Radiation-induced lung injury (RILI) is a common complication in radiotherapy of thoracic tumors and limits the therapeutic dose of radiation that can be given to effectively control tumors. RILI develops through a complex pathological process, resulting in induction and activation of various cytokines, infiltration by inflammatory cells, cytokine-induced activation of fibroblasts, and subsequent tissue remodeling by activated fibroblasts, ultimately leading to impaired lung function and respiratory failure. Increasing evidence shows that mesenchymal stem cells (MSCs) may play a main role in modulating inflammation and immune responses, promoting survival and repair of damaged resident cells and enhancing regeneration of damaged tissue through soluble paracrine factors and therapeutic extracellular vesicles. Therefore, the use of the MSC-derived secretome and exosomes holds promising potential for RILI therapy. Here, we review recent progress on the potential mechanisms of MSC therapy for RILI, with an emphasis on soluble paracrine factors of MSCs. Hypotheses on how MSC derived exosomes or MSC-released exosomal miRNAs could attenuate RILI are also proposed. Problems and translational challenges of the therapies based on the MSC-derived secretome and exosomes are further summarized and underline the need for caution on rapid clinical translation. Stem Cells Translational Medicine 2019;8:344-354.

High expression of C-C chemokine receptor 2 associates with poor overall survival in gastric cancer patients after surgical resection

BACKGROUND

Being a critical chemokine receptor in chemoattracting myeloid cells into tumor tissues, C-C chemokine receptor 2 (CCR2) has been detected in many malignant tumors. This study aims to evaluate the prognostic value of CCR2 expression in patients with gastric cancer after surgery.

RESULTS

CCR2 expression was detected in the accessory cells around gastric cancer cells in a diffused manner. CCR2 high expression was correlated with tumor invasion depth (P=0.006 and P=0.004, respectively), lymph node metastasis (P=0.038 and P=0.011, respectively) and TNM stage (P=0.003 and P=0.001, respectively) in the two independent sets. Multivariate Cox regression analysis identifies CCR2 high expression was an independent poor prognostic factor for OS of patients with gastric cancer in the two sets (P=0.013 and P=0.006, respectively). Integration of CCR2 expression and TNM stage could provide additional prognostic value for OS than TNM stage alone in the two sets (P=0.038 and P=0.002, respectively).

METHODS

Two independent sets comprising a total of 474 patients who received standard gastrectomy were enrolled in the study. The expression level of CCR2 was detected by immunohistochemistry. The correlations between CCR2 expression and clinicopathological factors were explored, and the prognostic significance for overall survival (OS) was determined by Kaplan-Meier analysis.

CONCLUSIONS

CCR2 high expression in the tumor microenvironment is a novel independent unfavorable prognostic factor for patients with gastric cancer. Combination of CCR2 expression and TNM stage could provide a better prognostic model for OS of gastric cancer patients.

Metabolic Plasticity of Stem Cells and Macrophages in Cancer

In addition to providing essential molecules for the overall function of cells, metabolism plays an important role in cell fate and can be affected by microenvironmental stimuli as well as cellular interactions. As a specific niche, tumor microenvironment (TME), consisting of different cell types including stromal/stem cells and immune cells, is characterized by distinct metabolic properties. This review will be focused on the metabolic plasticity of mesenchymal stromal/stem cells (MSC) and macrophages in TME, as well as on how the metabolic state of cancer stem cells (CSC), as key drivers of oncogenesis, affects their generation and persistence. Namely, heterogenic metabolic phenotypes of these cell populations, which include various levels of dependence on glycolysis or oxidative phosphorylation are closely linked to their complex roles in cancer progression. Besides well-known extrinsic factors, such as cytokines and growth factors, the differentiation and activation states of CSC, MSC, and macrophages are coordinated by metabolic reprogramming in TME. The significance of mutual metabolic interaction between tumor stroma and cancer cells in the immune evasion and persistence of CSC is currently under investigation.

Chemotherapeutic tumor microparticles combining low-dose irradiation reprogram tumor-promoting macrophages through a tumor-repopulating cell-curtailing pathway

Stem cell-like tumor-repopulating cells (TRCs) have a critical role in establishing a tumor immunosuppressive microenvironment. However, means to enhance antitumor immunity by disrupting TRCs are absent. Our previous studies have shown that tumor cell-derived microparticles (T-MPs) preferentially abrogate TRCs by delivering antitumor drugs into nuclei of TRCs. Here, we show that low dose irradiation (LDI) enhances the effect of cisplatin-packaging T-MPs (Cis-MPs) on TRCs, leading to inhibiting tumor growth in different tumor models. This antitumor effect is not due to the direct killing of tumor cells but is T cell-dependent and relies on macrophages for their efficacy. The underlying mechanism is involved in therapeutic reprograming macrophages from tumor-promotion to tumor-inhibition by disrupting TRCs and curtailing their vicious education on macrophages. These findings provide a novel strategy to reset macrophage polarization and confer their function more like M1 than M2 types with highly promising potential clinical applications.