Role of cystathionine β-synthase in human breast Cancer

Role of the 3-mercaptopyruvate sulfurtransferase in colon/colorectal cancers

The 3-mercaptopyruvate sulfurtransferase (MPST) is a protein persulfidase, occurring mainly in mitochondria. Although function of this protein in cancer cells has been already studied, no clear outcome can be postulated up to now. Therefore, we focused on the determination of function of MPST in colon (HCT116 cells)/colorectal (DLD1 cells) cancers. In silico analysis revealed that in gastrointestinal cancers, MPST together with its binding partners can be either of a high risk or might have a protective effect. Silencing of MPST gene resulted in decreased ATP, while acetyl-CoA levels were elevated. Increased apoptosis was detected in cells with silenced MPST gene, which was accompanied by decrease in mitochondrial membrane potential, but no changes in IP3 receptor's protein. Mitochondria underwent activation of fission and elevated DRP1 expression after MPST silencing. Proliferation and migration of DLD1 and HCT116 cells were markedly affected, showing the importance of MPST protein in colon/colorectal cancer development.

S-Allyl-L-Cysteine Affects Cell Proliferation and Expression of H2S-Synthetizing Enzymes in MCF-7 and MDA-MB-231 Adenocarcinoma Cell Lines

S-allyl-L-cysteine (SAC) is a sulfur compound present in fresh garlic. The reference literature describes its anticancer, antioxidant and neuroprotective effects. Breast cancer is infamously known as one of the most commonly diagnosed malignancies among women worldwide. Its morbidity and mortality make it reasonable to complete and expand knowledge on this cancer's characteristics. Hydrogen sulfide (H2S) and its naturally occurring donors are well-known investigation subjects for diverse therapeutic purposes. This study was conducted to investigate the SAC antiproliferative potential and effect on three enzymes involved in H2S metabolism: 3-mercaptopyruvate sulfurtransferase (MPST), cystathionine γ-lyase (CTH), and cystathionine β-synthase (CBS). We chose the in vitro cellular model of human breast adenocarcinomas: MCF-7 and MDA-MB-231. The expression of enzymes after 2, 4, 6, 8, and 24 h incubation with 2.24 mM, 3.37 mM, and 4.50 mM SAC concentrations was examined. The number of living cells was determined by the MTS assay. Changes in cellular plasma membrane integrity were measured by the LDH test. Expression changes at the protein level were analyzed using Western blot. A significant decrease in viable cells was registered for MCF-7 cells after all incubation times upon 4.50 mM SAC exposure, and after 6 and 24 h only in MDA-MB-231 upon 4.50 mM SAC. In both cell lines, the MPST gene expression significantly increased after the 24 h incubation with 4.50 mM SAC. S-allyl-L-cysteine had opposite effects on changes in CTH and CBS expression in both cell lines. In our research model, we confirmed the antiproliferative potential of SAC and concluded that our studies provided current information about the increase in MPST gene expression mediated by S-allyl-L-cysteine in the adenocarcinoma in vitro cellular model for the MCF-7 and MDA-MB-231 cell lines. Further investigation of this in vitro model can bring useful information regarding sulfur enzyme metabolism of breast adenocarcinoma and regulating its activity and expression (gene silencing) in anticancer therapy.

Role of Hydrogen Sulfide in Oncological and Non-Oncological Disorders and Its Regulation by Non-Coding RNAs: A Comprehensive Review

Recently, myriad studies have defined the versatile abilities of gasotransmitters and their synthesizing enzymes to play a "Maestro" role in orchestrating several oncological and non-oncological circuits and, thus, nominated them as possible therapeutic targets. Although a significant amount of work has been conducted on the role of nitric oxide (NO) and carbon monoxide (CO) and their inter-relationship in the field of oncology, research about hydrogen sulfide (H2S) remains in its infancy. Recently, non-coding RNAs (ncRNAs) have been reported to play a dominating role in the regulation of the endogenous machinery system of H2S in several pathological contexts. A growing list of microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are leading the way as upstream regulators for H2S biosynthesis in different mammalian cells during the development and progression of human diseases; therefore, their targeting can be of great therapeutic benefit. In the current review, the authors shed the light onto the biosynthetic pathways of H2S and their regulation by miRNAs and lncRNAs in various oncological and non-oncological disorders.

H2S-Synthesizing Enzymes Are Putative Determinants in Lung Cancer Management toward Personalized Medicine

Lung cancer is a lethal disease with no truly efficient therapeutic management despite the progresses, and metabolic profiling can be a way of stratifying patients who may benefit from new therapies. The present study is dedicated to profiling cysteine metabolic pathways in NSCLC cell lines and tumor samples. This was carried out by analyzing hydrogen sulfide (H2S) and ATP levels, examining mRNA and protein expression patterns of cysteine catabolic enzymes and transporters, and conducting metabolomics analysis using nuclear magnetic resonance (NMR) spectroscopy. Selenium-chrysin (SeChry) was tested as a therapeutic alternative with the aim of having an effect on cysteine catabolism and showed promising results. NSCLC cell lines presented different cysteine metabolic patterns, with A549 and H292 presenting a higher reliance on cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) to maintain H2S levels, while the PC-9 cell line presented an adaptive behavior based on the use of mercaptopyruvate sulfurtransferase (MST) and cysteine dioxygenase (CDO1), both contributing to the role of cysteine as a pyruvate source. The analyses of human lung tumor samples corroborated this variability in profiles, meaning that the expression of certain genes may be informative in defining prognosis and new targets. Heterogeneity points out individual profiles, and the identification of new targets among metabolic players is a step forward in cancer management toward personalized medicine.

Endogenous hydrogen sulfide inhibition suppresses tumor growth by promoting apoptosis and pyroptosis in esophageal cancer cells

BACKGROUND

Hydrogen sulfide (H2S) has been identified as the third gaseous signaling molecule. Endogenous H2S plays a key role in the progression of various types of cancer. However, the effect of endogenous H2S on the growth of esophageal cancer (EC) remains unknown.

METHODS

In this study, three kinds of H2S-producing enzymes inhibitors, DL-propargylglycine (PAG, inhibitor of cystathionine-γ-lyase), aminooxyacetic acid (AOAA, inhibitor of cystathionine-β-synthase), and L-aspartic acid (L-Asp, inhibitor of 3-mercaptopyruvate sulfurtransferase) were used to determine the role of endogenous H2S in the growth of EC9706 and K450 human EC cells.

RESULTS

The results indicated that the combination (PAG+AOAA+L-Asp) group showed higher inhibitory effects on the viability, proliferation, migration, and invasion of EC cells than PAG, AOAA, and L-Asp group. Inhibition of endogenous H2S promoted apoptosis via activation of mitogen-activated protein kinase pathway in EC cells. Endogenous H2S suppression triggered pyroptosis of EC cells by activating reactive oxygen species-mediated nuclear factor-κB signaling pathway. In addition, the combine group showed its more powerful growth-inhibitory effect on the growth of human EC xenograft tumors in nude mice without obvious toxicity.

CONCLUSION

Our results indicate that inhibition of endogenous H2S production can significantly inhibit human EC cell growth via promotion of apoptosis and pyroptosis. Endogenous H2S may be a promising therapeutic target in EC cells. Novel inhibitors for H2S-producing enzymes can be designed and developed for EC treatment.

Reactive Sulfur Species in Human Diseases

Significance: Reactive sulfur species (RSS) have been recently recognized as redox molecules no less important than reactive oxygen species or reactive nitrogen species. They possess regulatory and protective properties and are involved in various metabolic processes, thereby contributing to the maintenance of human health. It has been documented that many disorders, including neurological, cardiovascular, and respiratory diseases, diabetes mellitus (DM), and cancer, are related to the disruption of RSS homeostasis. Recent Advances: There is still a growing interest in the role of RSS in human diseases. Since a decrease in hydrogen sulfide or other RSS has been reported in many disorders, safe and efficient RSS donors have been developed and tested under in vitro conditions or on animal models. Critical Issues: Cardiovascular diseases and DM are currently the most common chronic diseases worldwide due to stressful and unhealthy lifestyles. In addition, because of high prevalence and aging of the population, neurological disorders including Parkinson's disease and Alzheimer's disease as well as respiratory diseases are a formidable challenge for health care systems. From this point of view, the knowledge of the role of RSS in these disorders and RSS modulation options are important and could be useful in therapeutic strategies. Future Directions: Improvement and standardization of analytical methods used for RSS estimation are crucial for the use of RSS as diagnostic biomarkers. Finding good, safe RSS donors applicable for therapeutic purposes could be useful as primary or adjunctive therapy in many common diseases. Antioxid. Redox Signal. 39, 1000-1023.

Dual targeting of H2S synthesizing enzymes; cystathionine β-synthase and cystathionine γ-lyase by miR-939-5p effectively curbs triple negative breast cancer

Introduction

Hydrogen sulfide (H2S) has been recently scrutinized for its critical role in aggravating breast cancer (BC) tumorigenicity. Several cancers aberrantly express H2S synthesizing enzymes; Cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE). However, their levels and interdependence in BC require further studies.

Objectives

Firstly, this study aimed to demonstrate a comparative expression profile of H2S synthesizing enzymes in BC vs normal tissue. Moreover, to investigate the reciprocal relationship between CBS and CSE and highlight the importance of dual targeting. Finally, to search for a valid dual repressor of the H2S synthesizing enzymes that could cease H2S production and reduce TNBC pathogenicity.

Methods

Pairwise analysis of tumor vs. normal tissues of 40 BC patients was carried out. The TNBC cell line MDA-MB-231 was transfected with oligonucleotides to study the H2S mediated molecular mechanisms. In silico screening was performed to identify dual regulator(s) for CBS and CSE. Gene expression analysis was performed using qRT-PCR and was confirmed on protein level using Western blot. TNBC hallmarks were evaluated using MTT, migration, and clonogenicity assays. H2S levels were detected using a AzMc fluorescent probe.

Results

BC tissues exhibited elevated levels of both CBS and CSE. Interestingly, upon CBS knockdown, CSE levels increased compensating for H2S production in TNBC cells, underlining the importance of dually targeting both enzymes in TNBC. In silico screening suggested miR-939-5p as a regulator of both CBS and CSE with high binding scores. Low expression levels of miR-939-5p were found in BC tissues, especially the aggressive subtypes. Ectopic expression of miR-939-5p significantly repressed CBS and CSE transcript and protein levels, diminished H2S production and attenuated TNBC hallmarks. Moreover, it improved the immune surveillance potency of TNBC cells through up regulating the NKG2D ligands, MICB and ULBP2 and reducing the immune suppressive cytokine IL-10.

Conclusion

This study sheds light on the reciprocal relationship between CBS and CSE and on the importance of their dual targeting, particularly in TNBC. It also postulates miR-939-5p as a potent dual repressor for CBS and CSE overcoming their redundancy in H2S production, a mechanism that can potentially attenuate TNBC oncogenicity and improves the immunogenic response.

The Triple Crown: NO, CO, and H2S in cancer cell biology

Nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) are three endogenously produced gases with important functions in the vasculature, immune defense, and inflammation. It is increasingly apparent that, far from working in isolation, these three exert many effects by modulating each other's activity. Each gas is produced by three enzymes, which have some tissue specificities and can also be non-enzymatically produced by redox reactions of various substrates. Both NO and CO share similar properties, such as activating soluble guanylate cyclase (sGC) to increase cyclic guanosine monophosphate (cGMP) levels. At the same time, H2S both inhibits phosphodiesterase 5A (PDE5A), an enzyme that metabolizes sGC and exerts redox regulation on sGC. The role of NO, CO, and H2S in the setting of cancer has been quite perplexing, as there is evidence for both tumor-promoting and pro-inflammatory effects and anti-tumor and anti-inflammatory activities. Each gasotransmitter has been found to have dual effects on different aspects of cancer biology, including cancer cell proliferation and apoptosis, invasion and metastasis, angiogenesis, and immunomodulation. These seemingly contradictory actions may relate to each gas having a dual effect dependent on its local flux. In this review, we discuss the major roles of NO, CO, and H2S in the context of cancer, with an effort to highlight the dual nature of each gas in different events occurring during cancer progression.

Recent advances in the role of endogenous hydrogen sulphide in cancer cells

Hydrogen sulphide (H2 S) is a gaseous neurotransmitter that can be self-synthesized by living organisms. With the deepening of research, the pathophysiological mechanisms of endogenous H2 S in cancer have been increasingly elucidated: (1) promote angiogenesis, (2) stimulate cell bioenergetics, (3) promote migration and proliferation thereby invasion, (4) inhibit apoptosis and (5) activate abnormal cell cycle. However, the increasing H2 S levels via exogenous sources show the opposite trend. This phenomenon can be explained by the bell-shaped pharmacological model of H2 S, that is, the production of endogenous (low concentration) H2 S promotes tumour growth while the exogenous (high concentration) H2 S inhibits tumour growth. Here, we review the impact of endogenous H2 S synthesis and metabolism on tumour progression, summarize the mechanism of action of H2 S in tumour growth, and discuss the possibility of H2 S as a potential target for tumour treatment.

Targeting Homocysteine and Hydrogen Sulfide Balance as Future Therapeutics in Cancer Treatment

A high level of homocysteine (Hcy) is associated with oxidative/ER stress, apoptosis, and impairment of angiogenesis, whereas hydrogen sulfide (H2S) has been found to reverse this condition. Recent studies have shown that cancer cells need to produce a high level of endogenous H2S to maintain cell proliferation, growth, viability, and migration. However, any novel mechanism that targets this balance of Hcy and H2S production has yet to be discovered or exploited. Cells require homocysteine metabolism via the methionine cycle for nucleotide synthesis, methylation, and reductive metabolism, and this pathway supports the high proliferative rate of cancer cells. Although the methionine cycle favors cancer cells for their survival and growth, this metabolism produces a massive amount of toxic Hcy that somehow cancer cells handle very well. Recently, research showed specific pathways important for balancing the antioxidative defense through H2S production in cancer cells. This review discusses the relationship between Hcy metabolism and the antiapoptotic, antioxidative, anti-inflammatory, and angiogenic effects of H2S in different cancer types. It also summarizes the historical understanding of targeting antioxidative defense systems, angiogenesis, and other protective mechanisms of cancer cells and the role of H2S production in the genesis, progression, and metastasis of cancer. This review defines a nexus of diet and precision medicine in targeting the delicate antioxidative system of cancer and explores possible future therapeutics that could exploit the Hcy and H2S balance.

Cystathionine β-synthase affects organization of cytoskeleton and modulates carcinogenesis in colorectal carcinoma cells

Background

Cystathionine β-synthase (CBS), one of three enzymes that endogenously produce hydrogen sulfide, is extensively studied for its relevance in the cells of various tumors. In our previous work, we observed that the immunofluorescence pattern of CBS is very similar to that of tubulin and actin. Therefore, we focused on the potential interaction of CBS with cytoskeletal proteins β-actin and β-tubulin and the functional relevance of the potential interaction of these proteins in colorectal carcinoma cell lines.

Methods

To study the potential interaction of CBS with cytoskeletal proteins and its functional consequences, a CBS-knockout DLD1 (DLDx) cell line was established by using the CRISPR/Cas9 gene editing method. The interaction of the selected cytoskeletal protein with CBS was studied by immunoprecipitation, Western blot analysis, immunofluorescence, and proximity ligation assay. The functional consequences were studied by proliferation and migration assays and by generation of xenografts in SCID/bg mice.

Results

We have found that CBS, an enzyme that endogenously produces H2S, binds to cytoskeletal β-tubulin and, to a lesser extent, also to β-actin in colorectal carcinoma-derived cells. When CBS was knocked out by the CRISPR/Cas9 technique (DLDx), we observed a de-arranged cytoskeleton compared to the unmodified DLD1 cell line. Treatment of these cells with a slow sulfide donor GYY4137 resulted in normal organization of the cytoskeleton, thus pointing to the role of CBS in microtubule dynamics. To evaluate the physiological importance of this observation, both DLD1 and DLDx cells were injected into SCID/bg mice, and the size and mass of the developed xenografts were evaluated. Significantly larger tumors developed from DLDx compared to the DLD1 cells, which correlated with the increased proliferation of these cells.

Conclusions

Taken together, in colorectal cancer DLD1 cells, CBS binds to the cytoskeleton, modulates microtubule dynamics, and thus affects the proliferation and migration in the colorectal carcinoma stable cell line.

A bio-friendly biotin-coupled and azide-functionalized naphthalimide for real-time endogenous hydrogen sulfide analysis in living cells

Hydrogen sulfide (H₂S) is involved in various biological processes. Thereby, abnormal levels of H₂S are reported to be related to various human diseases including cancer. Currently, many fluorescent probes are pioneered to detect H₂S by taking advantages of naphthalimides' unique internal charge transfer (ICT) property. However, most probes often require a high content of organic solvents or surfactants, and are limited to the analysis of exogenous H₂S treated externally in live cell studies, and have difficulties in analyzing endogenous H₂S, thus limiting their practical use. In this study, we developed a bio-friendly biotin-coupled and azide-functionalized naphthalimide (1) as a fluorescent probe enabling real-time analysis of H₂S in living system. Probe was able to provide a fluorescence at 545 nm via H₂S-mediated azide reduction selectively without interference by biologically abundant constituents and pH effects. In a biological study using A549 cells, probe readily penetrated living cells without cytotoxicity, and unreacted probes showed almost no fluorescence, enabling real-time detection of H₂S in living cells without requiring separate washing process. More importantly, under stimulation with various H₂S inducers and inhibitors, probe was able to provide an effective fluorescence response against fluctuations in endogenous H₂S, a key requirement for H₂S studies. Probe 1 can be applied as a useful chemical tool and enables the analysis of H₂S and the study of H₂S-related cell functions in a variety of environments.

Role of Cystathionine β-Synthase and 3-Mercaptopyruvate Sulfurtransferase in the Regulation of Proliferation, Migration, and Bioenergetics of Murine Breast Cancer Cells

Cystathionine β-synthase (CBS), CSE (cystathionine γ-lyase) and 3-mercaptopyruvate sulfurtransferase (3-MST) have emerged as three significant sources of hydrogen sulfide (H2S) in various forms of mammalian cancer. Here, we investigated the functional role of CBS’ and 3-MST’s catalytic activity in the murine breast cancer cell line EO771. The CBS/CSE inhibitor aminooxyacetic acid (AOAA) and the 3-MST inhibitor 2-[(4-hydroxy-6-methylpyrimidin-2-yl)sulfanyl]-1-(naphthalen-1-yl)ethan-1-one (HMPSNE) were used to assess the role of endogenous H2S in the modulation of breast cancer cell proliferation, migration, bioenergetics and viability in vitro. Methods included measurements of cell viability (MTT and LDH assays), cell proliferation and in vitro wound healing (IncuCyte) and cellular bioenergetics (Seahorse extracellular flux analysis). CBS and 3-MST, as well as expression were detected by Western blotting; H2S production was measured by the fluorescent dye AzMC. The results show that EO771 cells express CBS, CSE and 3-MST protein, as well as several enzymes involved in H2S degradation (SQR, TST, and ETHE1). Pharmacological inhibition of CBS or 3-MST inhibited H2S production, suppressed cellular bioenergetics and attenuated cell proliferation. Cell migration was only inhibited by the 3-MST inhibitor, but not the CBS/CSE inhibitor. Inhibition of CBS/CSE of 3-MST did not significantly affect basal cell viability; inhibition of 3-MST (but not of CBS/CSE) slightly enhanced the cytotoxic effects of oxidative stress (hydrogen peroxide challenge). From these findings, we conclude that endogenous H2S, generated by 3-MST and to a lower degree by CBS/CSE, significantly contributes to the maintenance of bioenergetics, proliferation and migration in murine breast cancer cells and may also exert a minor role as a cytoprotectant.

Employing machine learning using ferroptosis-related genes to construct a prognosis model for patients with osteosarcoma

Identifying effective biomarkers in osteosarcoma (OS) is important for predicting prognosis. We investigated the prognostic value of ferroptosis-related genes (FRGs) in OS. Transcriptome and clinical data were obtained from The Cancer Genome Atlas and Gene Expression Omnibus. FRGs were obtained from the ferroptosis database. Univariate COX regression and LASSO regression screening were performed and an FRG-based prognostic model was constructed, which was validated using the Gene Expression Omnibus cohort. The predictive power of the model was assessed via a subgroup analysis. A nomogram was constructed using clinical markers with independent prognostic significance and risk score results. The CIBERSORT algorithm was used to detect the correlation between prognostic genes and 22 tumor-infiltrating lymphocytes. The expression of prognostic genes in erastin-treated OS cell lines was verified via real-time PCR. Six prognostic FRGs (ACSL5, ATF4, CBS, CDO1, SCD, and SLC3A2) were obtained and used to construct the risk prognosis model. Subjects were divided into high- and low-risk groups. Prognosis was worse in the high-risk group, and the model had satisfactory prediction performance for patients younger than 18 years, males, females, and those with non-metastatic disease. Univariate COX regression analysis showed that metastasis and risk score were independent risk factors for patients with OS. Nomogram was built on independent prognostic factors with superior predictive power and patient benefit. There was a significant correlation between prognostic genes and tumor immunity. Six prognostic genes were differentially expressed in ferroptosis inducer-treated OS cell lines. The identified prognostic genes can regulate tumor growth and progression by affecting the tumor microenvironment.

Metabolism of Selenium, Selenocysteine, and Selenoproteins in Ferroptosis in Solid Tumor Cancers

A potential target of precision nutrition in cancer therapeutics is the micronutrient selenium (Se). Se is metabolized and incorporated as the amino acid selenocysteine (Sec) into 25 human selenoproteins, including glutathione peroxidases (GPXs) and thioredoxin reductases (TXNRDs), among others. Both the processes of Se and Sec metabolism for the production of selenoproteins and the action of selenoproteins are utilized by cancer cells from solid tumors as a protective mechanism against oxidative damage and to resist ferroptosis, an iron-dependent cell death mechanism. Protection against ferroptosis in cancer cells requires sustained production of the selenoprotein GPX4, which involves increasing the uptake of Se, potentially activating Se metabolic pathways such as the trans-selenation pathway and the TXNRD1-dependent decomposition of inorganic selenocompounds to sustain GPX4 synthesis. Additionally, endoplasmic reticulum-resident selenoproteins also affect apoptotic responses in the presence of selenocompounds. Selenoproteins may also help cancer cells adapting against increased oxidative damage and the challenges of a modified nutrient metabolism that result from the Warburg switch. Finally, cancer cells may also rewire the selenoprotein hierarchy and use Se-related machinery to prioritize selenoproteins that are essential to the adaptations against ferroptosis and oxidative damage. In this review, we discuss both the evidence and the gaps in knowledge on how cancer cells from solid tumors use Se, Sec, selenoproteins, and the Se-related machinery to promote their survival particularly via resistance to ferroptosis.

Endogenous and exogenous hydrogen sulfide modulates urothelial bladder carcinoma development in human cell lines

The role of H₂S in urothelial carcinoma (UC) is still unclear. Here we have evaluated the expression of H₂S producing enzymes as well as the effect of endogenous and exogenous H₂S on human bladder UC cells. In human UC cells the expression of cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MST); is significantly lower as compared to healthy cells. A modulatory role for the H₂S pathway is supported by the finding that, the overexpression of CSE or CBS, but not 3-MST, inhibits cell proliferation and promotes apoptosis. A similar effect is obtained by using exogenous H₂S. Diallyl trisulfide (DATS), which is a fully characterized H₂S donor, inhibits the proliferation of UC cells in a time and concentration-dependent manner as well as promotes apoptosis. Moreover, DATS also induces autophagy, as determined by transcriptomic and western blot analysis. Finally, DATS inhibits mRNA expression levels of canonical markers of epithelial-mesenchymal transition by limiting migration and clonogenic ability of human UC cells in vitro. In conclusion, in urothelial carcinoma, there is an impairment of H₂S pathway that involves CSE and CBS- derived hydrogen sulfide. Thus, targeting H₂S signaling pathway in urothelial carcinoma could represent a novel therapeutic strategy.

Carbon Monoxide Signaling: Examining Its Engagement with Various Molecular Targets in the Context of Binding Affinity, Concentration, and Biologic Response

Carbon monoxide (CO) has been firmly established as an endogenous signaling molecule with a variety of pathophysiological and pharmacological functions, including immunomodulation, organ protection, and circadian clock regulation, among many others. In terms of its molecular mechanism(s) of action, CO is known to bind to a large number of hemoproteins with at least 25 identified targets, including hemoglobin, myoglobin, neuroglobin, cytochrome c oxidase, cytochrome P450, soluble guanylyl cyclase, myeloperoxidase, and some ion channels with dissociation constant values spanning the range of sub-nM to high μM. Although CO's binding affinity with a large number of targets has been extensively studied and firmly established, there is a pressing need to incorporate such binding information into the analysis of CO's biologic response in the context of affinity and dosage. Especially important is to understand the reservoir role of hemoglobin in CO storage, transport, distribution, and transfer. We critically review the literature and inject a sense of quantitative assessment into our analyses of the various relationships among binding affinity, CO concentration, target occupancy level, and anticipated pharmacological actions. We hope that this review presents a picture of the overall landscape of CO's engagement with various targets, stimulates additional research, and helps to move the CO field in the direction of examining individual targets in the context of all of the targets and the concentration of available CO. We believe that such work will help the further understanding of the relationship of CO concentration and its pathophysiological functions and the eventual development of CO-based therapeutics. SIGNIFICANCE STATEMENT: The further development of carbon monoxide (CO) as a therapeutic agent will significantly rely on the understanding of CO's engagement with therapeutically relevant targets of varying affinity. This review critically examines the literature by quantitatively analyzing the intricate relationships among targets, target affinity for CO, CO level, and the affinity state of carboxyhemoglobin and provide a holistic approach to examining the molecular mechanism(s) of action for CO.

Cystathionine-β-synthase is essential for AKT-induced senescence and suppresses the development of gastric cancers with PI3K/AKT activation

Hyperactivation of oncogenic pathways downstream of RAS and PI3K/AKT in normal cells induces a senescence-like phenotype that acts as a tumor-suppressive mechanism that must be overcome during transformation. We previously demonstrated that AKT-induced senescence (AIS) is associated with profound transcriptional and metabolic changes. Here, we demonstrate that human fibroblasts undergoing AIS display upregulated cystathionine-β-synthase (CBS) expression and enhanced uptake of exogenous cysteine, which lead to increased hydrogen sulfide (H₂S) and glutathione (GSH) production, consequently protecting senescent cells from oxidative stress-induced cell death. CBS depletion allows AIS cells to escape senescence and re-enter the cell cycle, indicating the importance of CBS activity in maintaining AIS. Mechanistically, we show this restoration of proliferation is mediated through suppressing mitochondrial respiration and reactive oxygen species (ROS) production by reducing mitochondrial localized CBS while retaining antioxidant capacity of transsulfuration pathway. These findings implicate a potential tumor-suppressive role for CBS in cells with aberrant PI3K/AKT pathway activation. Consistent with this concept, in human gastric cancer cells with activated PI3K/AKT signaling, we demonstrate that CBS expression is suppressed due to promoter hypermethylation. CBS loss cooperates with activated PI3K/AKT signaling in promoting anchorage-independent growth of gastric epithelial cells, while CBS restoration suppresses the growth of gastric tumors in vivo. Taken together, we find that CBS is a novel regulator of AIS and a potential tumor suppressor in PI3K/AKT-driven gastric cancers, providing a new exploitable metabolic vulnerability in these cancers.

Hydrogen sulfide decreases photodynamic therapy outcome through the modulation of the cellular redox state

Photodynamic therapy (PDT) is a non-surgical treatment that has been approved for its human medical use in many cancers. PDT involves the interaction of a photosensitizer (PS) with light. The amino acid 5- aminolevulinic acid (ALA) can be used as a pro-PS, leading to the synthesis of Protoporphyrin IX. Hydrogen sulfide (H₂S) is an endogenously produced gas that belongs to the gasotransmitter family, which can diffuse through biological membranes and have relevant physiological effects such as cardiovascular functions, vasodilatation, inflammation, cell cycle and neuro-modulation. It was also proposed to have cytoprotective effects. We aimed to study the modulatory effects of H₂S on ALAPDT in the mammary adenocarcinoma cell line LM2. Exposure of the cells to NaHS (donor of H₂S) in concentrations up to 10 mM impaired the response to ALA-PDT in a dose-dependent manner. The addition of 3 doses of NaHS showed the highest effect. This decreased response to the photodynamic treatment was correlated to an increase in the GSH levels, catalase activity, a dose dependent reduction of PpIX and increased intracellular ALA, decreased levels of oxidized proteins and a decrease of PDT-induced ROS. NaHS also reduced the levels of singlet oxygen in an in vitro assay. H₂S also protected other cells of different origins against PDT mediated by ALA and other PSs. These results suggest that H₂S has a role in the modulation of the redox state of the cells, and thus impairs the response to ALA-PDT through multifactor pathways. These findings could contribute to developing new strategies to improve the effectiveness of PDT particularly mediated by ALA or other ROS-related treatments.

Identification of 8-Hydroxyquinoline Derivatives That Decrease Cystathionine Beta Synthase (CBS) Activity

CBS encodes a pyridoxal 5′-phosphate-dependent enzyme that catalyses the condensation of homocysteine and serine to form cystathionine. Due to its implication in some cancers and in the cognitive pathophysiology of Down syndrome, the identification of pharmacological inhibitors of this enzyme is urgently required. However, thus far, attempts to identify such molecules have only led to the identification of compounds with low potency and limited selectivity. We consequently developed an original, yeast-based screening method that identified three FDA-approved drugs of the 8-hydroxyquinoline family: clioquinol, chloroxine and nitroxoline. These molecules reduce CBS enzymatic activity in different cellular models, proving that the molecular mechanisms involved in yeast phenotypic rescue are conserved in mammalian cells. A combination of genetic and chemical biology approaches also revealed the importance of copper and zinc intracellular levels in the regulation of CBS enzymatic activity—copper promoting CBS activity and zinc inhibiting its activity. Taken together, these results indicate that our effective screening approach identified three new potent CBS inhibitors and provides new findings for the regulation of CBS activity, which is crucial to develop new therapies for CBS-related human disorders.

Hydrogen Sulfide Biology and Its Role in Cancer

Hydrogen sulfide (H₂S) is an endogenous biologically active gas produced in mammalian tissues. It plays a very critical role in many pathophysiological processes in the body. It can be endogenously produced through many enzymes analogous to the cysteine family, while the exogenous source may involve inorganic sulfide salts. H₂S has recently been well investigated with regard to the onset of various carcinogenic diseases such as lung, breast, ovaries, colon cancer, and neurodegenerative disorders. H₂S is considered an oncogenic gas, and a potential therapeutic target for treating and diagnosing cancers, due to its role in mediating the development of tumorigenesis. Here in this review, an in-detail up-to-date explanation of the potential role of H₂S in different malignancies has been reported. The study summarizes the synthesis of H₂S, its roles, signaling routes, expressions, and H₂S release in various malignancies. Considering the critical importance of this active biological molecule, we believe this review in this esteemed journal will highlight the oncogenic role of H₂S in the scientific community.

Emerging roles of cystathionine β-synthase in various forms of cancer

The expression of the reverse transsulfuration enzyme cystathionine-β-synthase (CBS) is markedly increased in many forms of cancer, including colorectal, ovarian, lung, breast and kidney, while in other cancers (liver cancer and glioma) it becomes downregulated. According to the clinical database data in high-CBS-expressor cancers (e.g. colon or ovarian cancer), high CBS expression typically predicts lower survival, while in the low-CBS-expressor cancers (e.g. liver cancer), low CBS expression is associated with lower survival. In the high-CBS expressing tumor cells, CBS, and its product hydrogen sulfide (H₂S) serves as a bioenergetic, proliferative, cytoprotective and stemness factor; it also supports angiogenesis and epithelial-to-mesenchymal transition in the cancer microenvironment. The current article reviews the various tumor-cell-supporting roles of the CBS/H₂S axis in high-CBS expressor cancers and overviews the anticancer effects of CBS silencing and pharmacological CBS inhibition in various cancer models in vitro and in vivo; it also outlines potential approaches for biomarker identification, to support future targeted cancer therapies based on pharmacological CBS inhibition.

Therapeutic implication of carbon monoxide in drug resistant cancers

Drug resistance is the major obstacle that undermines effective cancer treatment. Recently, the application of gas signaling molecules, e.g., carbon monoxide (CO), in overcoming drug resistance has gained significant attention. Growing evidence showed that CO could inhibit mitochondria respiratory effect and glycolysis, two major ATP production pathways in cancer cells, and suppress angiogenesis and inhibit the activity of cystathionine β-synthase that is important in regulating cancer cells homeostasis, leading to synergistic effects when combined with cisplatin, doxorubicin, or phototherapy, etc. in certain resistant cancer cells. In the current review, we attempted to have a summary of these research conducted in the past decade using CO in treating drug resistant cancers, and have a detailed interpretation of the underlying mechanisms. The critical challenges will be discussed and potential solutions will also be provided. The information collected in this work will hopefully evoke more effects in using CO for the treatment of drug resistant cancers.

The CBS-H2S axis promotes liver metastasis of colon cancer by upregulating VEGF through AP-1 activation

BACKGROUND

The main therapy for colon cancer with liver metastasis is chemotherapy based on 5-fluorouracil combined with targeted drugs. However, acquired drug resistance and severe adverse reactions limit patients' benefit from standard chemotherapy. Here, we investigate the involvement of endogenous hydrogen sulfide (H₂S) in liver metastasis of colon cancer and its potential value as a novel therapeutic target.

METHODS

We used the CRISPR/Cas9 system to knockdown CBS gene expression in colon cancer cell lines. PCR arrays and proteome arrays were applied to detect the transcription and protein expression levels, respectively, of angiogenesis-related genes after knockdown. The molecular mechanism was investigated by western blot analysis, RT-qPCR, immunofluorescence staining, ChIP assays and dual-luciferase reporter assays. A liver metastasis mouse model was adopted to investigate the effect of targeting CBS on tumour metastasis in vivo.

RESULTS

Knockdown of CBS decreased the metastasis and invasion of colon cancer cells and inhibited angiogenesis both in vivo and in vitro. Tissue microarray analysis showed a positive correlation between CBS and VEGF expression in colon cancer tissues. Further analysis at the molecular level validated a positive feedback loop between the CBS-H₂S axis and VEGF.

CONCLUSIONS

Endogenous H₂S promotes angiogenesis and metastasis in colon cancer, and targeting the positive feedback loop between the CBS-H₂S axis and VEGF can effectively intervene in liver metastasis of colon cancer.

C. elegans as a model organism to study female reproductive health

Female reproductive health has been historically understudied and underfunded. Here, we present the advantages of using a free-living nematode, Caenorhabditis elegans, as an animal system to study fundamental aspects of female reproductive health. C. elegans is a powerful high-throughput model organism that shares key genetic and physiological similarities with humans. In this review, we highlight areas of pressing medical and biological importance in the 21st century within the context of female reproductive health. These include the decline in female reproductive capacity with increasing chronological age, reproductive dysfunction arising from toxic environmental insults, and cancers of the reproductive system. C. elegans has been instrumental in uncovering mechanistic insights underlying these processes, and has been valuable for developing and testing therapeutics to combat them. Adopting a convenient model organism such as C. elegans for studying reproductive health will encourage further research into this field, and broaden opportunities for making advancements into evolutionarily conserved mechanisms that control reproductive function.

Tumor-Associated Macrophages: Critical Players in Drug Resistance of Breast Cancer

Drug resistance is one of the most critical challenges in breast cancer (BC) treatment. The occurrence and development of drug resistance are closely related to the tumor immune microenvironment (TIME). Tumor-associated macrophages (TAMs), the most important immune cells in TIME, are essential for drug resistance in BC treatment. In this article, we summarize the effects of TAMs on the resistance of various drugs in endocrine therapy, chemotherapy, targeted therapy, and immunotherapy, and their underlying mechanisms. Based on the current overview of the key role of TAMs in drug resistance, we discuss the potential possibility for targeting TAMs to reduce drug resistance in BC treatment, By inhibiting the recruitment of TAMs, depleting the number of TAMs, regulating the polarization of TAMs and enhancing the phagocytosis of TAMs. Evidences in our review support it is important to develop novel therapeutic strategies to target TAMs in BC to overcome the treatment of resistance.

Hydrogen Sulfide: An Emerging Precision Strategy for Gas Therapy

Advances in nanotechnology have enabled the rapid development of stimuli-responsive therapeutic nanomaterials for precision gas therapy. Hydrogen sulfide (H₂ S) is a significant gaseous signaling molecule with intrinsic biochemical properties, which exerts its various physiological effects under both normal and pathological conditions. Various nanomaterials with H₂ S-responsive properties, as new-generation therapeutic agents, are explored to guide therapeutic behaviors in biological milieu. The cross disciplinary of H₂ S is an emerging scientific hotspot that studies the chemical properties, biological mechanisms, and therapeutic effects of H₂ S. This review summarizes the state-of-art research on H₂ S-related nanomedicines. In particular, recent advances in H₂ S therapeutics for cancer, such as H₂ S-mediated gas therapy and H₂ S-related synergistic therapies (combined with chemotherapy, photodynamic therapy, photothermal therapy, and chemodynamic therapy) are highlighted. Versatile imaging techniques for real-time monitoring H₂ S during biological diagnosis are reviewed. Finally, the biosafety issues, current challenges, and potential possibilities in the evolution of H₂ S-based therapy that facilitate clinical translation to patients are discussed.

Reduced RBPMS Levels Promote Cell Proliferation and Decrease Cisplatin Sensitivity in Ovarian Cancer Cells

Worldwide, the number of cancer-related deaths continues to increase due to the ability of cancer cells to become chemotherapy-resistant and metastasize. For women with ovarian cancer, a staggering 70% will become resistant to the front-line therapy, cisplatin. Although many mechanisms of cisplatin resistance have been proposed, the key mechanisms of such resistance remain elusive. The RNA binding protein with multiple splicing (RBPMS) binds to nascent RNA transcripts and regulates splicing, transport, localization, and stability. Evidence indicates that RBPMS also binds to protein members of the AP-1 transcription factor complex repressing its activity. Until now, little has been known about the biological function of RBPMS in ovarian cancer. Accordingly, we interrogated available Internet databases and found that ovarian cancer patients with high RBPMS levels live longer compared to patients with low RBPMS levels. Similarly, immunohistochemical (IHC) analysis in a tissue array of ovarian cancer patient samples showed that serous ovarian cancer tissues showed weaker RBPMS staining when compared with normal ovarian tissues. We generated clustered regularly interspaced short palindromic repeats (CRISPR)-mediated RBPMS knockout vectors that were stably transfected in the high-grade serous ovarian cancer cell line, OVCAR3. The knockout of RBPMS in these cells was confirmed via bioinformatics analysis, real-time PCR, and Western blot analysis. We found that the RBPMS knockout clones grew faster and had increased invasiveness than the control CRISPR clones. RBPMS knockout also reduced the sensitivity of the OVCAR3 cells to cisplatin treatment. Moreover, β-galactosidase (β-Gal) measurements showed that RBPMS knockdown induced senescence in ovarian cancer cells. We performed RNAseq in the RBPMS knockout clones and identified several downstream-RBPMS transcripts, including non-coding RNAs (ncRNAs) and protein-coding genes associated with alteration of the tumor microenvironment as well as those with oncogenic or tumor suppressor capabilities. Moreover, proteomic studies confirmed that RBPMS regulates the expression of proteins involved in cell detoxification, RNA processing, and cytoskeleton network and cell integrity. Interrogation of the Kaplan-Meier (KM) plotter database identified multiple downstream-RBPMS effectors that could be used as prognostic and response-to-therapy biomarkers in ovarian cancer. These studies suggest that RBPMS acts as a tumor suppressor gene and that lower levels of RBPMS promote the cisplatin resistance of ovarian cancer cells.

A naphthalimide-based peptide conjugate for concurrent imaging and apoptosis induction in cancer cells by utilizing endogenous hydrogen sulfide

The excessive production of endogenous hydrogen sulfide (H2S) in cancer cells leads to enhanced tumor growth and metastasis. On the other hand, decreased endogenous H2S suppresses tumor growth. The reported approaches for inhibiting tumor growth are selective silencing of the tumor-promoting genes and pharmacological inhibition of these proteins. To enhance the antitumor efficacy of frontline chemotherapeutic agents, herein, we synthesized a highly sensitive endogenous H2S responsive fluorescent probe, i.e., a hydrogen sulfide-sensing naphthalimide-based peptide conjugate (HSNPc), which showed selective inhibition of proliferation of cancer cells due to apoptosis induction. Furthermore, HSNPc suppressed the glycolytic reserve, a critical energy source for the proliferation of cancer cells. HSNPc also decreased the Young's modulus of HeLa cells compared to the control cells, which demonstrated a direct relation between cell apoptosis and cell stiffness. Taken together, we demonstrated the dual function of detection and killing of cancer cells by HSNPc that can be likened to a theranostic role.

Molecular characterization and immune protection by cystathionine β-synthase from Eimeria tenella

Eimeria tenella is an obligate intracellular apicomplexan parasite that causes avian coccidiosis and leads to severe economic losses in the global poultry industry. Cystathionine β-synthase (CBS) and cystathionine γ-lyase (CGL) act together to generate H2S in the reverse transsulfuration pathway. In this study, E. tenella Cystathionine β-synthase (EtCBS) was cloned using rapid amplification of cDNA 5'-ends (5'RACE) and characterized, and its immunoprotective effects were evaluated. The recombinant EtCBS protein (rEtCBS) was expressed and successfully recognized by anti-sporozoites (Spz) protein rabbit serum. EtCBS mRNA levels were highest in Spz by qPCR, and the protein expression levels were higher in unsporulated oocysts (UO) than in other stages by Western blot. Indirect immunofluorescence showed that EtCBS protein was found on the surface of Spz and second-generation merozoites (Mrz). The invasion inhibition assays showed that rabbit anti-rEtCBS polyclonal antibodies effectively inhibited parasite invasion host cells. Chickens immunized with rEtCBS protein showed prominently increased weight gains and decreased oocyst output compared to nonimmunized and infected control group. The results suggest that EtCBS could be a potential vaccine candidate against E. tenella.

Identifying a Ferroptosis-Related Gene Signature for Predicting Biochemical Recurrence of Prostate Cancer

Ferroptosis induced by lipid peroxidation is closely related to cancer biology. Prostate cancer (PCa) is not only a malignant tumor but also a lipid metabolic disease. Previous studies have identified ferroptosis as an important pathophysiological pathway in PCa development and treatment, but its role in the prognosis of PCa is less well known. In this study, we constructed a nine-ferroptosis-related gene risk model that demonstrated strong prognostic and therapeutic predictive power. The higher risk score calculated by the model was significantly associated with a higher ferroptosis potential index, higher Ki67 expression, higher immune infiltration, higher probability of biochemical recurrence, worse clinicopathological characteristics, and worse response to chemotherapy and antiandrogen therapy in PCa. The mechanisms identified by the gene set enrichment analysis suggested that this signature can accurately distinguish high- and low-risk populations, which is possibly closely related to variations in steroid hormone secretion, regulation of endocrine processes, positive regulation of humoral immune response, and androgen response. Results of this study were confirmed in two independent PCa cohorts, namely, The Cancer Genome Atlas cohort and the MSK-IMPACT Clinical Sequencing Cohort, which contributed to the body of scientific evidence for the prediction of biochemical recurrence in patients with PCa. In addition, as the main components of this signature, the effects of the AIFM2 and NFS1 genes on ferroptosis were evaluated and verified by in vivo and in vitro experiments, respectively. The above findings provided new insights and presented potential clinical applications of ferroptosis in PCa.

Reprogrammed transsulfuration promotes basal-like breast tumor progression via realigning cellular cysteine persulfidation

Basal-like breast cancer (BLBC) is the most aggressive subtype of breast tumors with poor prognosis and limited molecular-targeted therapy options. We show that BLBC cells have a high Cys demand and reprogrammed Cys metabolism. Patient-derived BLBC tumors from four different cohorts exhibited elevated expression of the transsulfuration enzyme cystathione β-synthetase (CBS). CBS silencing (shCBS) made BLBC cells less invasive, proliferate slower, more vulnerable to oxidative stress and cystine (CySSCy) deprivation, prone to ferroptosis, and less responsive to HIF1-α activation under hypoxia. shCBS xenograft tumors grew slower than controls and exhibited impaired angiogenesis and larger necrotic areas. Sulfur metabolite profiling suggested that realigned sulfide/persulfide-inducing functions of CBS are important in BLBC tumor progression. Supporting this, the exclusion of serine, a substrate of CBS for producing Cys but not for producing sulfide/persulfide, did not exacerbate CySSCy deprivation-induced ferroptosis in shCBS BLBC cells. Impaired Tyr phosphorylation was detected in shCBS cells and xenografts, likely due to persulfidation-inhibited phosphatase functions. Overexpression of cystathione γ-lyase (CSE), which can also contribute to cellular sulfide/persulfide production, compensated for the loss of CBS activities, and treatment of shCBS xenografts with a CSE inhibitor further blocked tumor growth. Glutathione and protein-Cys levels were not diminished in shCBS cells or xenografts, but levels of Cys persulfidation and the persulfide-catabolizing enzyme ETHE1 were suppressed. Finally, expression of enzymes of the oxidizing Cys catabolism pathway was diminished, but expression of the persulfide-producing CARS2 was elevated in human BLBC tumors. Hence, the persulfide-producing pathways are major targetable determinants of BLBC pathology that could be therapeutically exploited.

Molecular Functions of Hydrogen Sulfide in Cancer

Hydrogen sulfide (H₂S) is a gasotransmitter that exerts a multitude of functions in both physiologic and pathophysiologic processes. H₂S-synthesizing enzymes are increased in a variety of human malignancies, including colon, prostate, breast, renal, urothelial, ovarian, oral squamous cell, and thyroid cancers. In cancer, H₂S promotes tumor growth, cellular and mitochondrial bioenergetics, migration, invasion, angiogenesis, tumor blood flow, metastasis, epithelia–mesenchymal transition, DNA repair, protein sulfhydration, and chemotherapy resistance Additionally, in some malignancies, increased H₂S-synthesizing enzyme expression correlates with a worse prognosis and a higher tumor stage. Here we review the role of H₂S in cancer, with an emphasis on the molecular mechanisms by which H₂S promotes cancer development, progression, dedifferentiation, and metastasis.

The Interleukin-6/Signal Transducer and Activator of Transcription-3/Cystathionine γ-Lyase Axis Deciphers the Transformation Between the Sensitive and Resistant Phenotypes of Breast Cancer Cells

Drug resistance of cancer cells is associated with redox homeostasis. The mechanism of acquired resistance of cancer cells to antitumor drugs is not well understood. Our previous studies revealed that drug resistance and highly expressed P-glycoprotein (P-gp) of MCF-7 breast cancer cells was dependent on intracellular redox homeostasis and declined capacity for scavenging reactive oxygen species (ROS). Recently, we observed that, unlike nontumorigenic cells MCF-10A, three tumorigenic breast cancer cells (MCF-7S, BT474, MDA-MB-231) reprogrammed their metabolism, highly expressed cystathionine-γ-lyase (CTH), and acquired a particular specialty to use methionine (Met) to synthesize glutathione (GSH) through the transsulfuration pathway. Interestingly, doxorubicin (adriamycin) further reprogrammed metabolism of MCF-7 cells sensitive to adriamycin (MCF-7S) and induced them to be another MCF-7 cell line resistant to adriamycin (MCF-7R) with dramatically downregulated CTH. The two MCF-7 cell lines showed distinctly different phenotypes in terms of intracellular GSH, ROS levels, expression and activity of P-gp and CTH, and drug resistance. We showed that CTH modulation or the methionine supply brought about the interconversion between MCF-7S and MCF-7R. Methionine deprivation or CTH silencing induced a resistant MCF-7R and lowered paclitaxel activity, yet methionine supplementation or CTH overexpression reversed the above effects, induced a sensitive phenotype of MCF-7S, and significantly increased the cytotoxicity of paclitaxel both in vitro and in vivo. Interleukin-6 (IL-6)/signal transducer and activator of transcription-3 (STAT3) initiated CTH expression and activity, and the effect on the resistant phenotype was exclusively dependent on CTH and ROS. This study suggests that the IL-6/STAT3/CTH axis plays a key role in the transformation between sensitive and resistant MCF-7 cells. SIGNIFICANCE STATEMENT: Cystathionine γ-lyase (CTH) plays a key role in transformation between the sensitive and resistant phenotypes of MCF-7 cells and is dependent on the interleukin-6 (IL-6)/signal transducer and activator of transcription-3 (STAT3) signaling axis. Modulation of the transsulfuration pathway on CTH or IL-6/STAT3 or methionine supplementation is beneficial for reversing the resistance of MCF-7 cells, which indicates a clinical translation potential.

Low CBS expression can identify patients who benefit from adjuvant chemotherapy in gastric cancer

Aim: To explore the clinical significance of Cystathionine beta-synthase (CBS) expression in gastric cancer (GC).Research design and methods: CBS expression and clinicopathological/follow-up information of patients with gastric cancer undergoing operation were collected from The Cancer Genome Atlas (TCGA) database. The association of CBS expression with patients' overall survival (OS) was determined in the entire cohort and different subgroups. Validation was performed in two external cohorts from NCBI Gene Expression Omnibus (GEO) database. The estimated drug response of the tumors with different CBS expressions was characterized. The potential CBS-related cellular pathways in chemoresistance were explored.Results: High CBS was associated with poor OS in patients receiving adjuvant chemotherapy (ACT) but not those without ACT. And ACT was associated with favorable OS in patients with low CBS expression but not those with high CBS expression. The results were verified in two external cohorts. Drug response prediction suggested that patients with low CBS expression showed high sensitivity to 5-Fluorouracil. Gene Set Enrichment Analysis (GSEA) suggested that CBS might contribute to GC chemoresistance via modulating many cellular pathways, including down-regulating apoptosis and P53 pathways while up-regulating DNA repair pathway.Conclusion: Low CBS expression can predict the benefit from ACT in GC.

An Analysis of the Multifaceted Roles of Heme in the Pathogenesis of Cancer and Related Diseases

Heme is an essential prosthetic group in proteins and enzymes involved in oxygen utilization and metabolism. Heme also plays versatile and fascinating roles in regulating fundamental biological processes, ranging from aerobic respiration to drug metabolism. Increasing experimental and epidemiological data have shown that altered heme homeostasis accelerates the development and progression of common diseases, including various cancers, diabetes, vascular diseases, and Alzheimer's disease. The effects of heme on the pathogenesis of these diseases may be mediated via its action on various cellular signaling and regulatory proteins, as well as its function in cellular bioenergetics, specifically, oxidative phosphorylation (OXPHOS). Elevated heme levels in cancer cells intensify OXPHOS, leading to higher ATP generation and fueling tumorigenic functions. In contrast, lowered heme levels in neurons may reduce OXPHOS, leading to defects in bioenergetics and causing neurological deficits. Further, heme has been shown to modulate the activities of diverse cellular proteins influencing disease pathogenesis. These include BTB and CNC homology 1 (BACH1), tumor suppressor P53 protein, progesterone receptor membrane component 1 protein (PGRMC1), cystathionine-β-synthase (CBS), soluble guanylate cyclase (sGC), and nitric oxide synthases (NOS). This review provides an in-depth analysis of heme function in influencing diverse molecular and cellular processes germane to disease pathogenesis and the modes by which heme modulates the activities of cellular proteins involved in the development of cancer and other common diseases.

Cysteine Boosts Fitness Under Hypoxia-Mimicked Conditions in Ovarian Cancer by Metabolic Reprogramming

Among gynecologic malignancies, ovarian cancer is the third most prevalent and the most common cause of death, especially due to diagnosis at an advanced stage together with resistance to therapy. As a solid tumor grows, cancer cells in the microenvironment are exposed to regions of hypoxia, a selective pressure prompting tumor progression and chemoresistance. We have previously shown that cysteine contributes to the adaptation to this hypoxic microenvironment, but the mechanisms by which cysteine protects ovarian cancer cells from hypoxia-induced death are still to be unveiled. Herein, we hypothesized that cysteine contribution relies on cellular metabolism reprogramming and energy production, being cysteine itself a metabolic source. Our results strongly supported a role of xCT symporter in energy production that requires cysteine metabolism instead of hydrogen sulfide (H2S) per se. Cysteine degradation depends on the action of the H2S-synthesizing enzymes cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and/or 3-mercaptopyruvate sulfurtransferase (MpST; together with cysteine aminotransferase, CAT). In normoxia, CBS and CSE inhibition had a mild impact on cysteine-sustained ATP production, pointing out the relevance of CAT + MpST pathway. However, in hypoxia, the concomitant inhibition of CBS and CSE had a stronger impact on ATP synthesis, thus also supporting a role of their hydrogen sulfide and/or cysteine persulfide-synthesizing activity in this stressful condition. However, the relative contributions of each of these enzymes (CBS/CSE/MpST) on cysteine-derived ATP synthesis under hypoxia remains unclear, due to the lack of specific inhibitors. Strikingly, NMR analysis strongly supported a role of cysteine in the whole cellular metabolism rewiring under hypoxia. Additionally, the use of cysteine to supply biosynthesis and bioenergetics was reinforced, bringing cysteine to the plateau of a main carbon sources in cancer. Collectively, this work supports that sulfur and carbon metabolism reprogramming underlies the adaptation to hypoxic microenvironment promoted by cysteine in ovarian cancer.

Efficacy of Novel Aminooxyacetic Acid Prodrugs in Colon Cancer Models: Towards Clinical Translation of the Cystathionine β-Synthase Inhibition Concept

Upregulation of hydrogen sulfide (H₂S) biosynthesis, at least in part related to the upregulation of cystathionine β-synthetase (CBS) in cancer cells, serves as a tumor-promoting factor and has emerged as a possible molecular target for antitumor drug development. To facilitate future clinical translation, we have synthesized a variety of novel CBS-targeting, esterase-cleavable prodrugs based on the structure of the prototypical CBS inhibitor aminooxyacetic acid (AOAA). The pharmacological properties of these compounds were evaluated in cell-free assays with recombinant human CBS protein, the human colon cancer cell line HCT116, and in vivo using various tumor-bearing mice models. The prodrug YD0251 (the isopropyl ester derivative of AOAA) was selected for detailed characterization. YD0251 exhibits improved antiproliferative efficacy in cell culture models when compared to AOAA. It is up to 18 times more potent than AOAA at suppressing HCT116 tumor growth in vivo and is effective when administered to tumor-bearing mice either via subcutaneous injection or oral gavage. Patient-derived xenografts (PDTXs) with higher levels of CBS protein grew significantly larger than tumors with lower levels, and YD0251 treatment inhibited the growth of PDTXs with elevated CBS, whereas it had no significant effect on PDTXs with low CBS protein levels. The toxicity of YD0251 was assessed in mice subjected to subchronic administration of supratherapeutic doses the inhibitor; no significant alteration in circulating markers of organ injury or histopathological alterations were noted, up to 60 mg/kg/day × 5 days. In preparation to a future theranostic concept (to match CBS inhibitor therapy to high-CBS expressors), we identified a potential plasma marker of CBS-expressing tumors. Colon cancer cells produced significant levels of lanthionine, a rare metabolic intermediate of CBS-mediated H₂S biosynthesis; forced expression of CBS into non-transformed epithelial cells increased lanthionine biogenesis in vitro and in vivo (measured in the urine of tumor-bearing mice). These current results may be useful to facilitate the translation of a CBS inhibition-based antitumor concept into the clinical space.

The Hidden Role of Hydrogen Sulfide Metabolism in Cancer

Hydrogen Sulfide (H₂S), an endogenously produced gasotransmitter, is involved in various important physiological and disease conditions, including vasodilation, stimulation of cellular bioenergetics, anti-inflammation, and pro-angiogenesis. In cancer, aberrant up-regulation of H₂S-producing enzymes is frequently observed in different cancer types. The recognition that tumor-derived H₂S plays various roles during cancer development reveals opportunities to target H₂S-mediated signaling pathways in cancer therapy. In this review, we will focus on the mechanism of H₂S-mediated protein persulfidation and the detailed information about the dysregulation of H₂S-producing enzymes and metabolism in different cancer types. We will also provide an update on mechanisms of H₂S-mediated cancer progression and summarize current options to modulate H₂S production for cancer therapy.

Hydrogen Sulfide (H2S) and Polysulfide (H2Sn) Signaling: The First 25 Years

Since the first description of hydrogen sulfide (H₂S) as a toxic gas in 1713 by Bernardino Ramazzini, most studies on H₂S have concentrated on its toxicity. In 1989, Warenycia et al. demonstrated the existence of endogenous H₂S in the brain, suggesting that H₂S may have physiological roles. In 1996, we demonstrated that hydrogen sulfide (H₂S) is a potential signaling molecule, which can be produced by cystathionine β-synthase (CBS) to modify neurotransmission in the brain. Subsequently, we showed that H₂S relaxes vascular smooth muscle in synergy with nitric oxide (NO) and that cystathionine γ-lyase (CSE) is another producing enzyme. This study also opened up a new research area of a crosstalk between H₂S and NO. The cytoprotective effect, anti-inflammatory activity, energy formation, and oxygen sensing by H₂S have been subsequently demonstrated. Two additional pathways for the production of H₂S with 3-mercaptopyruvate sulfurtransferase (3MST) from l- and d-cysteine have been identified. We also discovered that hydrogen polysulfides (H₂S_n, n ≥ 2) are potential signaling molecules produced by 3MST. H₂S_n regulate the activity of ion channels and enzymes, as well as even the growth of tumors. S-Sulfuration (S-sulfhydration) proposed by Snyder is the main mechanism for H₂S/H₂S_n underlying regulation of the activity of target proteins. This mini review focuses on the key findings on H₂S/H₂S_n signaling during the first 25 years.

The Role of Hydrogen Sulfide in Respiratory Diseases

Respiratory diseases are leading causes of death and disability around the globe, with a diverse range of health problems. Treatment of respiratory diseases and infections has been verified to be thought-provoking because of the increasing incidence and mortality rate. Hydrogen sulfide (H₂S) is one of the recognized gaseous transmitters involved in an extensive range of cellular functions, and physiological and pathological processes in a variety of diseases, including respiratory diseases. Recently, the therapeutic potential of H₂S for respiratory diseases has been widely investigated. H₂S plays a vital therapeutic role in obstructive respiratory disease, pulmonary fibrosis, emphysema, pancreatic inflammatory/respiratory lung injury, pulmonary inflammation, bronchial asthma and bronchiectasis. Although the therapeutic role of H₂S has been extensively studied in various respiratory diseases, a concrete literature review will have an extraordinary impact on future therapeutics. This review provides a comprehensive overview of the effective role of H₂S in respiratory diseases. Besides, we also summarized H₂S production in the lung and its metabolism processes in respiratory diseases.

The oncogene AAMDC links PI3K-AKT-mTOR signaling with metabolic reprograming in estrogen receptor-positive breast cancer

Adipogenesis associated Mth938 domain containing (AAMDC) represents an uncharacterized oncogene amplified in aggressive estrogen receptor-positive breast cancers. We uncover that AAMDC regulates the expression of several metabolic enzymes involved in the one-carbon folate and methionine cycles, and lipid metabolism. We show that AAMDC controls PI3K-AKT-mTOR signaling, regulating the translation of ATF4 and MYC and modulating the transcriptional activity of AAMDC-dependent promoters. High AAMDC expression is associated with sensitization to dactolisib and everolimus, and these PI3K-mTOR inhibitors exhibit synergistic interactions with anti-estrogens in IntClust2 models. Ectopic AAMDC expression is sufficient to activate AKT signaling, resulting in estrogen-independent tumor growth. Thus, AAMDC-overexpressing tumors may be sensitive to PI3K-mTORC1 blockers in combination with anti-estrogens. Lastly, we provide evidence that AAMDC can interact with the RabGTPase-activating protein RabGAP1L, and that AAMDC, RabGAP1L, and Rab7a colocalize in endolysosomes. The discovery of the RabGAP1L-AAMDC assembly platform provides insights for the design of selective blockers to target malignancies having the AAMDC amplification.

Therapeutic potential of endogenous hydrogen sulfide inhibition in breast cancer (Review)

Hydrogen sulfide (H₂S), the third gas signal molecule, is associated with the modulation of various physiological and pathological processes. Recent studies have reevealed that endogenous H₂S may promote proliferation, induce angiogenesis and inhibit apoptosis, thereby stimulating oncogenesis. Conversely, decreased endogenous H₂S release suppresses growth of various tumors including breast cancer. This observation suggests an alternative tumor therapy strategy by inhibiting H₂S-producing enzymes to reduce the release of endogenous H₂S. Breast cancer is the most common type of cancer in women. Due to the lack of approved targeted therapy, its recurrence and metastasis still affect its clinical treatment. In recent years, significant progress has been made in the control of breast cancer by using inhibitors on H₂S-producing enzymes. This review summarized the roles of endogenous H₂S-producing enzymes in breast cancer and the effects of the enzyme inhibitors on anticancer and anti-metastasis, with the aim of providing new insights for the treatment of breast cancer.

Cysteine metabolic circuitries: druggable targets in cancer

To enable survival in adverse conditions, cancer cells undergo global metabolic adaptations. The amino acid cysteine actively contributes to cancer metabolic remodelling on three different levels: first, in its free form, in redox control, as a component of the antioxidant glutathione or its involvement in protein s-cysteinylation, a reversible post-translational modification; second, as a substrate for the production of hydrogen sulphide (H2S), which feeds the mitochondrial electron transfer chain and mediates per-sulphidation of ATPase and glycolytic enzymes, thereby stimulating cellular bioenergetics; and, finally, as a carbon source for epigenetic regulation, biomass production and energy production. This review will provide a systematic portrayal of the role of cysteine in cancer biology as a source of carbon and sulphur atoms, the pivotal role of cysteine in different metabolic pathways and the importance of H2S as an energetic substrate and signalling molecule. The different pools of cysteine in the cell and within the body, and their putative use as prognostic cancer markers will be also addressed. Finally, we will discuss the pharmacological means and potential of targeting cysteine metabolism for the treatment of cancer.

Inhibition of cystathionine β-synthase promotes apoptosis and reduces cell proliferation in chronic myeloid leukemia

Increased endogenous hydrogen sulfide (H₂S) level by cystathionine β-synthase (CBS) has been shown to closely relate tumorigenesis. H₂S promotes angiogenesis, stimulates bioenergy metabolism and inhibits selective phosphatases. However, the role of CBS and H₂S in chronic myeloid leukemia (CML) remains elusive. In this study, we found that CBS and H₂S levels were increased in the bone marrow mononuclear cells of pediatric CML patients, as well as in the CML-derived K562 cells and CBS expression levels were correlated with different disease phases. Inhibition of CBS reduced the proliferation of the CML primary bone marrow mononuclear cells and induced growth inhibition, apoptosis, cell cycle arrest, and migration suppression in K562 cells and tumor xenografts. The knockdown of CBS expression by shRNA and inhibiting CBS activity by AOAA decreased the endogenous H₂S levels, promoted mitochondrial-related apoptosis and inhibited the NF-κB-mediated gene expression. Our study suggests that inhibition of CBS induces cell apoptosis, as well as limits cell proliferation and migration, a potential target for the treatment of chronic myeloid leukemia.

Pharmacological induction of mesenchymal-epithelial transition via inhibition of H2S biosynthesis and consequent suppression of ACLY activity in colon cancer cells

Hydrogen sulfide (H₂S) is an important endogenous gaseous transmitter mediator, which regulates a variety of cellular functions in autocrine and paracrine manner. The enzymes responsible for the biological generation of H₂S include cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST). Increased expression of these enzymes and overproduction of H₂S has been implicated in essential processes of various cancer cells, including the stimulation of metabolism, maintenance of cell proliferation and cytoprotection. Cancer cell identity is characterized by so-called "transition states". The progression from normal (epithelial) to transformed (mesenchymal) state is termed epithelial-to-mesenchymal transition (EMT) whereby epithelial cells lose their cell-to-cell adhesion capacity and gain mesenchymal characteristics. The transition process can also proceed in the opposite direction, and this process is termed mesenchymal-to-epithelial transition (MET). The current project was designed to determine whether inhibition of endogenous H₂S production in colon cancer cells affects the EMT/MET balance in vitro. Inhibition of H₂S biosynthesis in HCT116 human colon cancer cells was achieved either with aminooxyacetic acid (AOAA) or 2-[(4-hydroxy-6-methylpyrimidin-2-yl)sulfanyl]-1-(naphthalen-1-yl)ethan-1-one (HMPSNE). These inhibitors induced an upregulation of E-cadherin and Zonula occludens-1 (ZO-1) expression and downregulation of fibronectin expression, demonstrating that H₂S biosynthesis inhibitors can produce a pharmacological induction of MET in colon cancer cells. These actions were functionally reflected in an inhibition of cell migration, as demonstrated in an in vitro "scratch wound" assay. The mechanisms involved in the action of endogenously produced H₂S in cancer cells in promoting (or maintaining) EMT (or tonically inhibiting MET) relate, at least in part, in the induction of ATP citrate lyase (ACLY) protein expression, which occurs via upregulation of ACLY mRNA (via activation of the ACLY promoter). ACLY in turn, regulates the Wnt-β-catenin pathway, an essential regulator of the EMT/MET balance. Taken together, pharmacological inhibition of endogenous H₂S biosynthesis in cancer cells induces MET. We hypothesize that this may contribute to anti-cancer / anti-metastatic effects of H₂S biosynthesis inhibitors.

Cost-effective diagnostic kits for selective detection of gaseous H2S

Unsymmetrical tri-functionalized perylene diimide dyes were explored for making solution- and solid-state-based colorimetric kits for the detection of gaseous and aqueous H2S.

Increased expression of cystathionine beta-synthase and chemokine ligand 21 is closely associated with poor prognosis in extrahepatic cholangiocarcinoma

The expression of Cystathionine beta-synthase (CBS) and Chemokine ligand 21 (CCL21) is associated with the tumorigenesis and progression of a variety of tumors, but whether alterations in their expression levels correlates with the carcinogenesis and progression of EHCC is still unknown. This study investigated the clinicopathological significance of CBS and CCL21 expression in EHCC.We investigated the correlations between the expression of CBS and CCL21 and clinicopathological characteristics in EHCC using EnVision immunohistochemistry.The expression of CBS and CCL21 was significantly higher in EHCC tumors than in nontumor tissues (P < .05 and P < .01). EHCC patients with CBS and CCL21 expression combined with lymph node metastasis, tumor cell invasion, and TNM III/IV stage had more severe conditions than those with no lymph node metastasis, distant invasion and TNM I/II stage (P < .01). Kaplan-Meier survival analysis showed that the overall survival rates for EHCC patients with negative CBS or CCL21 reaction were significantly higher than those for patients with positive CBS or CCL21 reaction((P < .01). CBS or CCL21 expression was revealed as an independent poor prognostic factor for EHCC patients by Cox multivariate analysis.The present study indicates that CBS and CCL21 expression is closely associated with the pathogenesis of clinical, pathological and biological behaviors and poor prognosis in EHCC.