S-nitrosylated and non-nitrosylated COX2 have differential expression and distinct subcellular localization in normal and breast cancer tissue

Phototherapeutic activity of polypyridyl ruthenium(II) complexes through synergistic action of nitric oxide and singlet oxygen

In recent years, photodynamic therapy (PDT) and gas therapy (GT) have emerged as research hotspots due to their excellent cancer treatment efficacy. By combining the advantages of both, the simultaneous and controllable release of reactive oxygen species (ROS) and nitric oxide (NO) has become a possibility. This paper describes the design of two Ru(II) complexes, [Ru(bpy)2(NFIP)](PF6)2 (Ru1, bpy = 2,2'-bipyridine, NFIP = 4-nitro-3-trifluoromethylaniline-1H-imidazo[4,5-f][1,10]phenanthroline) and [Ru(phen)2(NFIP)](PF6)2 (Ru2, phen = 1,10-phenanthroline), through the integration of the polypyridyl ruthenium structure and a photoresponsive NO donor. The structures and purity of the complexes were confirmed by several methods, including 1H NMR, mass spectrometry, elemental analysis, high performance liquid chromatography (HPLC) and UV-Vis absorption spectra. Both complexes were demonstrated to efficiently generate singlet oxygen (1O2) (ΦΔ = 0.40 and 0.44 in phosphate buffered saline (PBS) for Ru1 and Ru2, respectively) and release NO under visible light irradiation. Upon light exposure, Ru2 exhibited significant phototoxicity against human cervical cancer HeLa cells. In vitro experiments indicated that Ru2 elevated the levels of ROS and NO in HeLa cells when exposed to light, resulting in mitochondrial impairment and caspase-mediated cell death. Overall, Ru2 proves to be a potent phototherapeutic compound, capable of producing ROS and NO, thus providing precision in cancer phototherapy.

Ex Vivo Patient-Derived Explant Model for Neurofibromatosis Type 1-Related Cutaneous Neurofibromas

Cutaneous neurofibromas (CNFs) are benign tumors that occur in the dermis of individuals with the inherited tumor predisposition disorder, neurofibromatosis type 1. CNFs cause disfigurement, pain, burning, and itching, resulting in substantially reduced QOL in patients with neurofibromatosis type 1. CNFs are benign tumors that exhibit cellular and molecular heterogeneity, making it difficult to develop tractable in vitro or in vivo models. As a result, CNF research and drug discovery efforts have been limited. To address this need, we developed a reproducible patient-derived explant (PDE) ex vivo culture model using CNF tumors from patients with neurofibromatosis type 1. CNF PDEs remain viable in culture for over 9 days and recapitulate the cellular composition and molecular signaling of CNFs. Using CNF PDEs as a model system, we found that proliferation was associated with increased T-cell infiltration. Furthermore, we identified a pattern of reciprocal inflammatory signaling in CNF PDEs in which tumors rely on prostaglandin or leukotriene-mediated signaling pathways. As proof of principle, we show that ex vivo glucocorticoid treatment reduced the expression of proinflammatory genes, confirming that CNF PDEs are a useful model for both mechanistic studies and preclinical drug testing.

Leveraging the redundancy of S-denitrosylases in response to S-nitrosylation of caspases: Experimental strategies and beyond

Redox-based protein posttranslational modifications, such as S-nitrosylation of critical, active site cysteine thiols have garnered significant clinical attention and research interest, reasoning for one of the crucial biological implications of reactive messenger molecule, nitric oxide in the cellular repertoire. The stringency of the S-(de)nitrosylation-based redox switch governs the activity and contribution of several susceptible enzymes in signal transduction processes and diverse pathophysiological settings, thus establishing it as a transient yet reasonable, and regulated mechanism of NO adduction and release. Notably, endogenous proteases like cytosolic and mitochondrial caspases with a molecular weight ranging from 33 to 55 kDa are susceptible to performing this biochemistry in the presence of major oxidoreductases, which further unveils the enormous redox-mediated regulational control of caspases in the etiology of diseases. In addition to advancing the progress of the current state of understanding of 'redox biochemistry' in the field of medicine and enriching the existing dynamic S-nitrosoproteome, this review stands as a testament to an unprecedented shift in the underpinnings for redundancy and redox relay between the major redoxin/antioxidant systems, fine-tuning of which can command the apoptotic control of caspases at the face of nitro-oxidative stress. These intricate functional overlaps and cellular backups, supported rationally by kinetically favorable reaction mechanisms suggest the physiological relevance of identifying and involving such cognate substrates for cellular S-denitrosylases that can shed light on the bigger picture of extensively proposing targeted therapies and redox-based drug designing to potentially alleviate the side effects of NOx/ROS in disease pathogenesis.

S-Nitrosylation at the intersection of metabolism and autophagy: Implications for cancer

Metabolic plasticity, which determines tumour growth and metastasis, is now understood to be a flexible and context-specific process in cancer metabolism. One of the major pathways contributing to metabolic adaptations in eucaryotic cells is autophagy, a cellular degradation and recycling process that is activated during periods of starvation or stress to maintain metabolite and biosynthetic intermediate levels. Consequently, there is a close association between the metabolic adaptive capacity of tumour cells and autophagy-related pathways in cancer. Additionally, nitric oxide regulates protein function and signalling through S-nitrosylation, a post-translational modification that can also impact metabolism and autophagy. The primary objective of this review is to provide an up-to-date overview of the role of S-nitrosylation at the intersection of metabolism and autophagy in cancer. First, we will outline the involvement of S-nitrosylation in the metabolic adaptations that occur in tumours. Then, we will discuss the multifaceted role of autophagy in cancer, the interplay between metabolism and autophagy during tumour progression, and the contribution of S-nitrosylation to autophagic dysregulation in cancer. Finally, we will present insights into relevant therapeutic aspects and discuss prospects for the future.

Targeting Nitric Oxide: Say NO to Metastasis

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.

Repurposing [11C]MC1 for PET Imaging of Cyclooxygenase-2 in Colorectal Cancer Xenograft Mouse Models

PURPOSE

Cyclooxygenase-2 (COX-2) is a target for inflammation and colorectal cancer (CRC). This study evaluated the COX-2 neuro-PET radiopharmaceutical, [11C]MC1, in CRC xenograft mice.

PROCEDURES

[11C]MC1 was evaluated in ICRscid mice with HT-29 and HCT-116 CRC xenografts, with high and low COX-2 expression, respectively, by immunohistochemistry, cellular uptake, dynamic PET/MR imaging, ex vivo biodistribution, and radiometabolite analysis.

RESULTS

HT-29 xenografts were well visualized with [11C]MC1 using PET/MR. Time-activity curves revealed steady tumor radioactivity accumulation in HT-29 xenografts that plateaued from 40 to 60 min (3.07 ± 0.65 %ID/g) and was significantly reduced by pre-treatment with MC1 or celecoxib (1.62 ± 0.29 and 1.18 ± 0.21 %ID/g, respectively, p = 0.045 and p = 0.005). Radiometabolite analysis showed that [11C]MC1 accounted for >90 % of tumor radioactivity, with <10 % in plasma, at 40 min post-injection of the radiotracer.

CONCLUSIONS

[11C]MC1 is a promising PET imaging agent for COX-2 in CRC and translation for cancer research should be considered.

Nitric oxide favours tumour-promoting inflammation through mitochondria-dependent and -independent actions on macrophages

Production of nitric oxide (NO) has been demonstrated in several malignancies, however its role remains not fully understood, specifically in relation to the metabolic and functional implications that it may have on immune cells participating in tumorigenesis. Here, we show that inducible NO synthase (iNOS) is expressed in cancers of the colon and the prostate, mainly by tumour cells, and NO generation is evidenced by widespread nitrotyrosine (NT) staining in tumour tissue. Furthermore, presence of NT is observed in the majority of tumour-associated macrophages (TAMs), despite low iNOS expression by these cells, suggesting that NO from the tumour microenvironment affects TAMs. Indeed, using a co-culture model, we demonstrate that NO produced by colon and prostate cancer cells is sufficient to induce NT formation in neighbouring macrophages. Moreover, exposure to exogenous NO promotes mitochondria-dependent and -independent changes in macrophages, which orientate their polarity towards an enhanced pro-inflammatory phenotype, whilst decreasing antigen-presenting function and wound healing capacity. Abrogating endogenous NO generation in murine macrophages, on the other hand, decreases their pro-inflammatory phenotype. These results suggest that the presence of NO in cancer may regulate TAM metabolism and function, favouring the persistence of inflammation, impairing healing and subverting adaptive immunity responses.

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Nitric oxide (NO) from the cancer microenvironment acts on tumour-associated macrophages (TAMs).

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NO induces a phenotypic shift in macrophages through mitochondria-dependent and -independent pathways.

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NO favours pro-inflammatory cytokine production whilst decreasing macrophage function as antigen presenting cell.

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NO impairs repair function of macrophages.

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Presence of NO in cancer may regulate TAM metabolism and function, favouring tumour-promoting inflammation.

S-Nitrosylation in Tumor Microenvironment

S-nitrosylation is a selective and reversible post-translational modification of protein thiols by nitric oxide (NO), which is a bioactive signaling molecule, to exert a variety of effects. These effects include the modulation of protein conformation, activity, stability, and protein-protein interactions. S-nitrosylation plays a central role in propagating NO signals within a cell, tissue, and tissue microenvironment, as the nitrosyl moiety can rapidly be transferred from one protein to another upon contact. This modification has also been reported to confer either tumor-suppressing or tumor-promoting effects and is portrayed as a process involved in every stage of cancer progression. In particular, S-nitrosylation has recently been found as an essential regulator of the tumor microenvironment (TME), the environment around a tumor governing the disease pathogenesis. This review aims to outline the effects of S-nitrosylation on different resident cells in the TME and the diverse outcomes in a context-dependent manner. Furthermore, we will discuss the therapeutic potentials of modulating S-nitrosylation levels in tumors.