Hypoxia Promotes Tumor Growth in Linking Angiogenesis to Immune Escape

Despite the impressive progress over the past decade, in the field of tumor immunology, such as the identification of tumor antigens and antigenic peptides, there are still many obstacles in eliciting an effective immune response to eradicate cancer. It has become increasingly clear that tumor microenvironment plays a crucial role in the control of immune protection. Tumors have evolved to utilize hypoxic stress to their own advantage by activating key biochemical and cellular pathways that are important in progression, survival, and metastasis. Hypoxia-inducible factor (HIF-1) and vascular endothelial growth factor (VEGF) play a determinant role in promoting tumor cell growth and survival. Hypoxia contributes to immune suppression by activating HIF-1 and VEGF pathways. Accumulating evidence suggests a link between hypoxia and tumor tolerance to immune surveillance through the recruitment of regulatory cells (regulatory T cells and myeloid derived suppressor cells). In this regard, hypoxia (HIF-1α and VEGF) is emerging as an attractive target for cancer therapy. How the microenvironmental hypoxia poses both obstacles and opportunities for new therapeutic immune interventions will be discussed

Cytokeratin 18 expression pattern correlates with renal cell carcinoma progression: Relationship with Snail

Renal cell carcinoma (RCC) is the most common type of kidney cancer and recent developments in the molecular biology of RCC have identified multiple pathways associated with the development of this cancer. This study aimed at analyzing the expression pattern of cytokeratin 18 (CK18) in RCC patients and its prognostic relevance. We quantified CK18 mRNA expression and protein using real-time reverse transcription quantitative polymerase chain reaction (RT-QPCR) and immunohistochemistry, respectively, in paired tumor and non-tumor samples from 42 patients. Our data indicate that CK18 mRNA and proteins levels increased with advanced stage and grade of the disease. Using primary (RCC5) and metastatic renal cell carcinoma (RCC5 met) cell lines, we demonstrated that CK18 expression was 5-fold higher in the metastatic as compared to the primary RCC cell line and correlated with a migratory phenotype characterized by a distinct elongated morphology as revealed by Phalloidin staining. In addition, RCC5 met cells displayed an increased capacity to attach to fibronectin and collagen which was lost following CK18 knock-down. Our data also indicate that the expression of CK18 was associated with increased Snail expression which correlated positively with advanced disease in RCC patients. The present findings suggest that CK18 may play an important role in the progression of RCC and it may be used as a new predictor for RCC

Attenuation of Soft-Tissue Sarcomas Resistance to the Cytotoxic Action of TNF-α by Restoring p53 Function

BACKGROUND: Isolated limb perfusion with TNF-α and melphalan is used with remarkable efficiency to treat unresectable limb sarcomas. Here we tested the ability of TNF-α to directly induce apoptosis of sarcoma cells. In addition, we investigated the impact of p53 in the regulation of such effect. METHODOLOGY/PRINCIPAL FINDINGS: We first analysed the ability of TNF-α to induce apoptosis in freshly isolated tumour cells. For this purpose, sarcoma tumours (n = 8) treated ex vivo with TNF-α were processed for TUNEL staining. It revealed substantial endothelial cell apoptosis and levels of tumour cell apoptosis that varied from low to high. In order to investigate the role of p53 in TNF-α-induced cell death, human sarcoma cell lines (n = 9) with different TP53 and MDM2 status were studied for their sensitivity to TNF-α. TP53(Wt) cell lines were sensitive to TNF-α unless MDM2 was over-expressed. However, TP53(Mut) and TP53(Null) cell lines were resistant. TP53 suppression in TP53(Wt) cell lines abrogated TNF-α sensitivity and TP53 overexpression in TP53(Null) cell lines restored it. The use of small molecules that restore p53 activity, such as CP-31398 or Nutlin-3a, in association with TNF-α, potentiated the cell death of respectively TP53(Mut) and TP53(Wt)/MDM2(Ampl). In particular, CP-31398 was able to induce p53 as well as some of its apoptotic target genes in TP53(Mut) cells. In TP53(Wt)/MDM2(Ampl) cells, Nutlin-3a effects were associated with a decrease of TNF-α-induced NF-κB-DNA binding and correlated with a differential regulation of pro- and anti-apoptotic genes such as TP53BP2, GADD45, TGF-β1 and FAIM. CONCLUSION/SIGNIFICANCE: More effective therapeutic approaches are critically needed for the treatment of unresectable limb sarcomas. Our results show that restoring p53 activity in sarcoma cells correlated with increased sensitivity to TNF-α, suggesting that this strategy may be an important determinant of TNF-α-based sarcomas treatment

L’hypoxie tumorale

L’hypoxie est une caractéristique majeure de la plupart des tumeurs solides. Les cellules s’adaptent à la baisse de l’apport en oxygène en stabilisant les facteurs de transcription HIF (hypoxia-inducible factor) qui, à leur tour, activent l’expression de nombreux gènes résultant en la survie et le maintien des fonctions cellulaires. Dans les cellules tumorales, l’exposition au stress hypoxique active, via les facteurs HIF, une série de molécules qui leur permettent de résister à la lyse dépendante des cellules tueuses du système immunitaire. L’hypoxie tissulaire régule également les fonctions des cellules de l’immunité et leur différenciation. Cette revue décrit les mécanismes de résistance tumorale aux effecteurs cytotoxiques induits par l’hypoxie, et les conséquences fonctionnelles de l’hypoxie sur les cellules immunes

Hypoxia: a key player in antitumor immune response. A Review in the Theme: Cellular Responses to Hypoxia

International audienceThe tumor microenvironment is a complex system, playing an important role in tumor development and progression. Besides cellular stromal components, extracellular matrix fibers, cytokines, and other metabolic mediators are also involved. In this review we outline the potential role of hypoxia, a major feature of most solid tumors, within the tumor microenvironment and how it contributes to immune resistance and immune suppression/tolerance and can be detrimental to antitumor effector cell functions. We also outline how hypoxic stress influences immunosuppressive pathways involving macrophages, myeloid-derived suppressor cells, T regulatory cells, and immune checkpoints and how it may confer tumor resistance. Finally, we discuss how microenvironmental hypoxia poses both obstacles and opportunities for new therapeutic immune interventions

PD-L1 is a novel direct target of HIF-1α, and its blockade under hypoxia enhanced MDSC-mediated T cell activation

International audienc

Improving Cancer Immunotherapy by Targeting the Hypoxic Tumor Microenvironment: New Opportunities and Challenges

Initially believed to be a disease of deregulated cellular and genetic expression, cancer is now also considered a disease of the tumor microenvironment. Over the past two decades, significant and rapid progress has been made to understand the complexity of the tumor microenvironment and its contribution to shaping the response to various anti-cancer therapies, including immunotherapy. Nevertheless, it has become clear that the tumor microenvironment is one of the main hallmarks of cancer. Therefore, a major challenge is to identify key druggable factors and pathways in the tumor microenvironment that can be manipulated to improve the efficacy of current cancer therapies. Among the different tumor microenvironmental factors, this review will focus on hypoxia as a key process that evolved in the tumor microenvironment. We will briefly describe our current understanding of the molecular mechanisms by which hypoxia negatively affects tumor immunity and shapes the anti-tumor immune response. We believe that such understanding will provide insight into the therapeutic value of targeting hypoxia and assist in the design of innovative combination approaches to improve the efficacy of current cancer therapies, including immunotherapy