Tumour progression is dependent on the interaction between tumour cells and cells of the surrounding microenvironment. The tumour is a dynamic milieu consisting of various cell types such as ...endothelial cells, fibroblasts, cells of the immune system and mesenchymal stem cells (MSCs). MSCs are multipotent stromal cells that are known to reside in various areas such as the bone marrow, fat and dental pulp. MSCs have been found to migrate towards inflammatory sites and studies have shown that they also migrate towards and incorporate into the tumour. The key question is how they interact there. MSCs may interact with tumour cells through paracrine signalling. On the other hand, MSCs have the capacity to differentiate to various cell types such as osteocytes, chondrocytes and adipocytes and it is possible that MSCs differentiate at the site of the tumour. More recently it has been shown that cross-talk between tumour cells and MSCs has been shown to increase metastatic potential and promote epithelial-to-mesenchymal transition. This review will focus on the role of MSCs in tumour development at various stages of progression from growth of the primary tumour to the establishment of distant metastasis.
Nitric oxide (NO) is a key player in both the development and suppression of tumourigenesis depending on the source and concentration of NO. In this review, we discuss the mechanisms by which NO ...induces DNA damage, influences the DNA damage repair response, and subsequently modulates cell cycle arrest. In some circumstances, NO induces cell cycle arrest and apoptosis protecting against tumourigenesis. NO in other scenarios can cause a delay in cell cycle progression, allowing for aberrant DNA repair that promotes the accumulation of mutations and tumour heterogeneity. Within the tumour microenvironment, low to moderate levels of NO derived from tumour and endothelial cells can activate angiogenesis and epithelial-to-mesenchymal transition, promoting an aggressive phenotype. In contrast, high levels of NO derived from inducible nitric oxide synthase (iNOS) expressing M1 and Th1 polarised macrophages and lymphocytes may exert an anti-tumour effect protecting against cancer. It is important to note that the existing evidence on immunomodulation is mainly based on murine iNOS studies which produce higher fluxes of NO than human iNOS. Finally, we discuss different strategies to target NO related pathways therapeutically. Collectively, we present a picture of NO as a master regulator of cancer development and progression.
Nitric oxide (NO) is a short-lived, pleiotropic molecule that affects numerous critical functions in the body. Presently, there are markedly conflicting findings in the literature regarding NO and ...its role in carcinogenesis and tumor progression. NO has been shown to have dichotomous effects on cellular proliferation, apoptosis, migration, invasion, angiogenesis and many other important processes in cancer biology. It has been shown to be both pro- and antitumorigenic, depending on the concentration and the tumor microenvironment in question. NO is generated by three isoforms of NO synthase (NOS) that are widely expressed and sometimes upregulated in human tumors. Due to its vast array of physiological functions, it presents a huge challenge to researchers to discover its true potential in cancer biology and consequently, its use in anticancer therapies. In this study, we review the current knowledge in this area, with an emphasis placed on NO modulation as an anticancer therapy, focusing on NO-donating drugs and NOS inhibitors.
Inflammation is widely recognized as an inducer of cancer progression. The inflammation-associated enzyme, inducible nitric oxide synthase (NOS2), has emerged as a candidate oncogene in estrogen ...receptor (ER)-negative breast cancer, and its increased expression is associated with disease aggressiveness and poor survival. Although these observations implicate NOS2 as an attractive therapeutic target, the mechanisms of both NOS2 induction in tumors and nitric oxide (NO)-driven cancer progression are not fully understood. To enhance our mechanistic understanding of NOS2 induction in tumors and its role in tumor biology, we used stimulants of NOS2 expression in ER ⁻ and ER ⁺ breast cancer cells and examined downstream NO-dependent effects. Herein, we show that up-regulation of NOS2 occurs in response to hypoxia, serum withdrawal, IFN-γ, and exogenous NO, consistent with a feed-forward regulation of NO production by the tumor microenvironment in breast cancer biology. Moreover, we found that key indicators of an aggressive cancer phenotype including increased S100 calcium binding protein A8, IL-6, IL-8, and tissue inhibitor matrix metalloproteinase-1 are up-regulated by these NOS2 stimulants, whereas inhibition of NOS2 in MDA-MB-231 breast cancer cells suppressed these markers. Moreover, NO altered cellular migration and chemoresistance of MDA-MB-231 cells to Taxol. Most notably, MDA-MB-231 tumor xenographs and cell metastases from the fat pad to the brain were significantly suppressed by NOS2 inhibition in nude mice. In summary, these results link elevated NOS2 to signals from the tumor microenvironment that arise with cancer progression and show that NO production regulates chemoresistance and metastasis of breast cancer cells.
Breast cancer is the second leading cause of cancer-related deaths among women in the United States. Development and progression of malignancy are associated with diverse cell signaling pathways that ...control cell proliferation, survival, motility, invasion, and metastasis. Recent Advances: An increasing number of clinical studies have implicated a strong relationship between elevated tumor nitric oxide synthase-2 (NOS2) expression and poor patient survival.
Herein, we review what we believe to be key mechanisms in the role(s) of NOS2-derived nitric oxide (NO) as a driver of breast cancer disease progression. High NO increases cyclooxygenase-2 activity, hypoxia inducible factor-1 alpha protein stabilization, and activation of important cell signaling pathways, including phosphoinositide 3-kinase/protein kinase B, mitogen-activated protein kinase, epidermal growth factor receptor, and Ras, through post-translational protein modifications. Moreover, dysregulated NO flux within the tumor microenvironment has other important roles, including the promotion of angiogenesis and modulation of matrix metalloproteinase/tissue inhibitor matrix metalloproteinase associated with tumor progression.
The elucidation of these and other NO-driven pathways implicates NOS2 as a key driver of breast cancer disease progression and provides a new perspective in the identification of novel targets that may be therapeutically beneficial in the treatment of estrogen receptor-negative disease. Antioxid. Redox Signal. 26, 1044-1058.
Proinflammatory signaling pathways are commonly up-regulated in breast cancer. In estrogen receptor-negative (ER⁻) and triple-negative breast cancer (TNBC), nitric oxide synthase-2 (NOS2) and ...cyclooxygenase-2 (COX2) have been described as independent predictors of disease outcome. We further explore these findings by investigating the impact of their coexpression on breast cancer survival. Elevated coexpression of NOS2/COX2 proteins is a strong predictor of poor survival among ER⁻ patients (hazard ratio: 21). Furthermore, we found that the key products of NOS2 and COX2, NO and prostaglandin E2 (PGE2), respectively, promote feed-forward NOS2/COX2 crosstalk in both MDA-MB-468 (basal-like) and MDA-MB-231 (mesenchymal-like) TNBC cell lines in which NO induced COX2 and PGE2 induced NOS2 proteins. COX2 induction by NO involved TRAF2 activation that occurred in a TNFα-dependent manner in MDA-MB-468 cells. In contrast, NO-mediated TRAF2 activation in the more aggressive MDA-MB-231 cells was TNFα independent but involved the endoplasmic reticulum stress response. Inhibition of NOS2 and COX2 using amino-guanidine and aspirin/indomethacin yielded an additive reduction in the growth of MDA-MB-231 tumor xenografts. These findings support a role of NOS2/COX2 crosstalk during disease progression of aggressive cancer phenotypes and offer insight into therapeutic applications for better survival of patients with ER⁻ and TNBC disease.
Targeting Nitric Oxide: Say NO to Metastasis Reddy, Tejaswini P; Glynn, Sharon A; Billiar, Timothy R ...
Clinical cancer research,
05/2023, Volume:
29, Issue:
10
Journal Article
Peer reviewed
Open access
Utilizing targeted therapies capable of reducing cancer metastasis, targeting chemoresistant and self-renewing cancer stem cells, and augmenting the efficacy of systemic chemo/radiotherapies is vital ...to minimize cancer-associated mortality. Targeting nitric oxide synthase (NOS), a protein within the tumor microenvironment, has gained interest as a promising therapeutic strategy to reduce metastatic capacity and augment the efficacy of chemo/radiotherapies in various solid malignancies. Our review highlights the influence of nitric oxide (NO) in tumor progression and cancer metastasis, as well as promising preclinical studies that evaluated NOS inhibitors as anticancer therapies. Lastly, we highlight the prospects and outstanding challenges of using NOS inhibitors in the clinical setting.
Human endogenous retroviruses (HERV), ancient integrations of exogenous viruses, make up 8% of our genome. Long thought of as mere vestigial genetic elements, evidence is now accumulating to suggest ...a potential functional role in numerous pathologies including neurodegenerative diseases, autoimmune disorders, and multiple cancers. The youngest member of this group of transposable elements is HERV-K (HML-2). Like the majority of HERV sequences, significant post-insertional mutations have disarmed HERV-K (HML-2), preventing it from producing infectious viral particles. However, some insertions have retained limited coding capacity, and complete open reading frames for all its constituent proteins can be found throughout the genome. For this reason HERV-K (HML-2) has garnered more attention than its peers. The tight epigenetic control thought to suppress expression in healthy tissue is lost during carcinogenesis. Upregulation of HERV-K (HML-2) derived mRNA and protein has been reported in a variety of solid and liquid tumour types, and while causality has yet to be established, progressively more data are emerging to suggest this phenomenon may contribute to tumour growth and metastatic capacity. Herein we discuss its potential utility as a diagnostic tool and therapeutic target in light of the current
in vitro
,
in vivo
and clinical evidence linking HERV-K (HML-2) to tumour progression.
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