Regulation of STAT3 and NF-κB activations by S-nitrosylation in multiple myeloma

A coumarin-furoxan hybrid as novel nitric oxide donor induced cell apoptosis and ferroptosis in NSCLC by promoting S-nitrosylation of STAT3 and negative regulation of JAK2-STAT3 pathway

Non-small cell lung cancer (NSCLC) still lacks effective treatment because of its extensive mutation diversity and frequent drug resistance. Therefore, it is urgent to develop new therapeutic strategies for NSCLC. In this study, we evaluated the inhibitory effect of a new coumarin-furoxan hybrid compound 9, a nitric oxide (NO) donor drug, on NSCLC proliferation and its mechanism. Our results show that compound 9 can inhibit the growth of four NSCLC cell lines and H1975 xenograft model in a dose-dependent manner. Compound 9 effectively releases high concentrations of NO within the mitochondria, leading to cellular oxidative stress, mitochondrial dysfunction, and apoptosis. Moreover, compound 9 inhibits JAK2/STAT3 protein phosphorylation and induces S-nitrosylation modification of STAT3, ultimately resulting in endogenous apoptosis in NSCLC. Additionally, compound 9 significantly induces NSCLC ferroptosis by depleting intracellular GSH, elevating MDA levels, inhibiting SLC7A11/GSH protein expression, and negatively regulating the JAK2/STAT3 pathway. In summary, this study elucidates the inhibitory effects of compound 9 on NSCLC proliferation and provides insights into the underlying mechanisms, offering new possibilities for NSCLC treatment strategies.

Insights on the functional dualism of nitric oxide in the hallmarks of cancer

Nitric oxide (NO), a gaseous radical, governs a variety of physiological and pathological processes, including cancer, pro-inflammatory signalling, and vasodilation. The family of nitric oxide synthases (NOS), which comprises the constitutive forms, nNOS and eNOS, and the inducible form, iNOS, produces NO enzymatically. Additionally, NO can be generated non-enzymatically from the nitrate-nitrite-NO pathway. The anti- and pro-oxidant properties of NO and its functional dualism in cancer is due to its highly reactive nature. Numerous malignancies have NOS expression, which interferes with the tumour microenvironment to modulate the tumour's growth in both favourable and unfavourable ways. NO regulates a number of mechanisms in the tumour microenvironment, including metabolism, cell cycle, DNA repair, angiogenesis, and apoptosis/necrosis, depending on its concentration and spatiotemporal profile. This review focuses on the bi-modal impact of nitric oxide on the alteration of a few cancer hallmarks.

Regulation of macrophage activation by S-Nitrosothiols following ozone-induced lung injury

Acute exposure to ozone causes oxidative stress, characterized by increases in nitric oxide (NO) and other reactive nitrogen species in the lung. NO has been shown to modify thiols generating S-nitrosothiols (SNOs); this results in altered protein function. In macrophages this can lead to changes in inflammatory activity which impact the resolution of inflammation. As SNO formation is dependent on the redox state of both the NO donor and the recipient thiol, the local microenvironment plays a key role in its regulation. This dictates not only the chemical feasibility of SNO formation but also mechanisms by which they may form. In these studies, we compared the ability of the SNO donors, ethyl nitrite (ENO), which targets both hydrophobic and hydrophilic thiols, SNO-propanamide (SNOPPM) which targets hydrophobic thiols, and S-nitroso-N-acetylcysteine. (SNAC) which targets hydrophilic thiols. to modify macrophage activation following ozone exposure. Mice were treated with air or ozone (0.8 ppm, 3 h) followed 1 h later by intranasal administration of ENO, SNOPPM or SNAC (1-500 μM) or appropriate controls. Mice were euthanized 48 h later. Each of the SNO donors reduced ozone-induced inflammation and modified the phenotype of macrophages both within the lung lining fluid and the tissue. ENO and SNOPPM were more effective than SNAC. These findings suggest that the hydrophobic SNO thiol pool targeted by SNOPPM and ENO plays a major role in regulating macrophage phenotype following ozone induced injury.

The emerging roles of nitric oxide in ferroptosis and pyroptosis of tumor cells

Tumor cells can develop resistance to cell death which is divided into necrosis and programmed cell death (PCD). PCD, including apoptosis, autophagy, ferroptosis, pyroptosis, and necroptosis. Ferroptosis and pyroptosis, two new forms of cell death, have gradually been of interest to researchers. Boosting ferroptosis and pyroptosis of tumor cells could be a potential cancer therapy. Nitric oxide (NO) is a ubiquitous, lipophilic, highly diffusible, free-radical signaling molecule that plays various roles in tumorigenesis. In addition, NO also has regulatory mechanisms through S-nitrosylation that do not depend on the classic NO/sGC/cGMP signaling. The current tumor treatment strategy for NO is to promote cell death through promoting S-nitrosylation-induced apoptosis while multiple drawbacks dampen this tumor therapy. However, numerous studies have suggested that suppression of NO is perceived to active ferroptosis and pyroptosis, which could be a better anti-tumor treatment. In this review, ferroptosis and pyroptosis are described in detail. We summarize that NO influences ferroptosis and pyroptosis and infer that S-nitrosylation mediates ferroptosis- and pyroptosis-related signaling pathways. It could be a potential cancer therapy different from NO-induced apoptosis of tumor cells. Finally, the information shows the drugs that manipulate endogenous production and exogenous delivery of NO to modulate the levels of S-nitrosylation.

Pillars and Gaps of S-Nitrosylation-Dependent Epigenetic Regulation in Physiology and Cancer

Nitric oxide (NO) is a diffusible signaling molecule produced by three isoforms of nitric oxide synthase, which release NO during the metabolism of the amino acid arginine. NO participates in pathophysiological responses of many different tissues, inducing concentration-dependent effect. Indeed, while low NO levels generally have protective effects, higher NO concentrations induce cytotoxic/cytostatic actions. In recent years, evidences have been accumulated unveiling S-nitrosylation as a major NO-dependent post-translational mechanism ruling gene expression. S-nitrosylation is a reversible, highly regulated phenomenon in which NO reacts with one or few specific cysteine residues of target proteins generating S-nitrosothiols. By inducing this chemical modification, NO might exert epigenetic regulation through direct effects on both DNA and histones as well as through indirect actions affecting the functions of transcription factors and transcriptional co-regulators. In this light, S-nitrosylation may also impact on cancer cell gene expression programs. Indeed, it affects different cell pathways and functions ranging from the impairment of DNA damage repair to the modulation of the activity of signal transduction molecules, oncogenes, tumor suppressors, and chromatin remodelers. Nitrosylation is therefore a versatile tool by which NO might control gene expression programs in health and disease.

Altitude acclimatization via hypoxia-mediated oxidative eustress involves interplay of protein nitrosylation and carbonylation: A redoxomics perspective

AIM

Hypoxia is an important feature of multiple diseases like cancer and obesity and also an environmental stressor to high altitude travelers. Emerging research suggests the importance of redox signaling in physiological responses transforming the notion of oxidative stress into eustress and distress. However, the behavior of redox protein post-translational modifications (PTMs), and their correlation with stress acclimatization in humans remains sketchy. Scant information exists about modifications in redoxome during physiological exposure to environmental hypoxia. In this study, we investigated redox PTMs, nitrosylation and carbonylation, in context of extended environmental hypoxia exposure.

METHODS

The volunteers were confirmed to be free of any medical conditions and matched for age and weight. The human global redoxome and the affected networks were investigated using TMT-labeled quantitative proteo-bioinformatics and biochemical assays. The percolator PSM algorithm was used for peptide-spectrum match (PSM) validation in database searches. The FDR for peptide matches was set to 0.01. 1-way ANOVA and Tukey's Multiple Comparison test were used for biochemical assays. p-value<0.05 was considered statistically significant. Three independent experiments (biological replicates) were performed. Results were presented as Mean ± standard error of mean (SEM).

KEY FINDINGS

This investigation revealed direct and indirect interplay between nitrosylation and carbonylation especially within coagulation and inflammation networks; interlinked redox signaling (via nitrosylation‑carbonylation); and novel nitrosylation and carbonylation sites in individual proteins.

SIGNIFICANCE

This study elucidates the role of redox PTMs in hypoxia signaling favoring tolerance and survival. Also, we demonstrated direct and indirect interplay between nitrosylation and carbonylation is crucial to extended hypoxia tolerance.

Exploiting S-nitrosylation for cancer therapy: facts and perspectives

S-nitrosylation, the post-translational modification of cysteines by nitric oxide, has been implicated in several cellular processes and tissue homeostasis. As a result, alterations in the mechanisms controlling the levels of S-nitrosylated proteins have been found in pathological states. In the last few years, a role in cancer has been proposed, supported by the evidence that various oncoproteins undergo gain- or loss-of-function modifications upon S-nitrosylation. Here, we aim at providing insight into the current knowledge about the role of S-nitrosylation in different aspects of cancer biology and report the main anticancer strategies based on: (i) reducing S-nitrosylation-mediated oncogenic effects, (ii) boosting S-nitrosylation to stimulate cell death, (iii) exploiting S-nitrosylation through synthetic lethality.

S-nitrosocysteine and glutathione depletion synergize to induce cell death in human tumor cells: Insights into the redox and cytotoxic mechanisms

Nitric oxide (NO)-dependent signaling and cytotoxic effects are mediated in part via protein S-nitrosylation. The magnitude and duration of S-nitrosylation are governed by the two main thiol reducing systems, the glutathione (GSH) and thioredoxin (Trx) antioxidant systems. In recent years, approaches have been developed to harness the cytotoxic potential of NO/nitrosylation to inhibit tumor cell growth. However, progress in this area has been hindered by insufficient understanding of the balance and interplay between cellular nitrosylation, other oxidative processes and the GSH/Trx systems. In addition, the mechanistic relationship between thiol redox imbalance and cancer cell death is not fully understood. Herein, we explored the redox and cellular effects induced by the S-nitrosylating agent, S-nitrosocysteine (CysNO), in GSH-sufficient and -deficient human tumor cells. We used l-buthionine-sulfoximine (BSO) to induce GSH deficiency, and employed redox, biochemical and cellular assays to interrogate molecular mechanisms. We found that, under GSH-sufficient conditions, a CysNO challenge (100-500 μM) results in a marked yet reversible increase in protein S-nitrosylation in the absence of appreciable S-oxidation. In contrast, under GSH-deficient conditions, CysNO induces elevated and sustained levels of both S-nitrosylation and S-oxidation. Experiments in various cancer cell lines showed that administration of CysNO or BSO alone commonly induce minimal cytotoxicity whereas BSO/CysNO combination therapy leads to extensive cell death. Studies in HeLa cancer cells revealed that treatment with BSO/CysNO results in dual inhibition of the GSH and Trx systems, thereby amplifying redox stress and causing cellular dysfunction. In particular, BSO/CysNO induced rapid oxidation and collapse of the actin cytoskeletal network, followed by loss of mitochondrial function, leading to profound and irreversible decrease in ATP levels. Further observations indicated that BSO/CysNO-induced cell death occurs via a caspase-independent mechanism that involves multiple stress-induced pathways. The present findings provide new insights into the relationship between cellular nitrosylation/oxidation, thiol antioxidant defenses and cell death. These results may aid future efforts to develop NO/redox-based anticancer approaches.

Extensive protein S-nitrosylation associated with human pancreatic ductal adenocarcinoma pathogenesis

NO (nitric oxide)-mediated protein S-nitrosylation has been established as one major signaling mechanism underlying cancer initiation and development, but its roles in PDAC (pancreatic ductal adenocarcinoma) pathogenesis still remain largely unexplored. In this study, we identified 585 unique S-nitrosylation sites among 434 proteins in PDAC patients and PANC-1 cell line by a site-specific proteomics. Larger number of S-nitrosylated proteins were identified in PDAC tissues and PANC-1 cells than adjacent non-cancerous tissues. These S-nitrosylated proteins are significantly enriched in a multitude of biological processes associated with tumorigenesis, including carbohydrate metabolism, cytoskeleton regulation, cell cycle, focal adhesion, adherent junctions, and cell migration. Components of the pancreatic cancer pathway were extensively S-nitrosylated, such as v-raf-1 murine leukemia viral oncogene homolog 1 (Raf-1) and Signal transducer and activator of transcription 3 (STAT3). Moreover, NOS (NO synthase) inhibitor significantly repressed STAT3 S-nitrosylation in PANC-1 cells, which caused significant increase of STAT3 phosphorylation and PANC-1 cell viability, suggesting important roles of protein S-nitrosylation in PDAC development. These results revealed extensive protein S-nitrosylation associated with PDAC pathogenesis, which provided a basis for protein modification-based cancer diagnosis and targeted therapy.

STAT3: A Promising Therapeutic Target in Multiple Myeloma

Multiple myeloma (MM) is an incurable plasma cell malignancy for which novel treatment options are required. Signal Transducer and Activator of Transcription 3 (STAT3) overexpression in MM appears to be mediated by a variety of factors including interleukin-6 signaling and downregulation of Src homology phosphatase-1 (SHP-1). STAT3 overexpression in MM is associated with an adverse prognosis and may play a role in microenvironment-dependent treatment resistance. In addition to its pro-proliferative role, STAT3 upregulates anti-apoptotic proteins and leads to microRNA dysregulation in MM. Phosphatase of regenerating liver 3 (PRL-3) is an oncogenic phosphatase which is upregulated by STAT3. PRL-3 itself promotes STAT-3 phosphorylation resulting in a positive feedback loop. PRL-3 is overexpressed in a subset of MM patients and may cooperate with STAT3 to promote survival of MM cells. Indirectly targeting STAT3 via JAK (janus associated kinase) inhibition has shown promise in early clinical trials. Specific inhibitors of STAT3 showed in vitro efficacy but have failed in clinical trials while several STAT3 inhibitors derived from herbs have been shown to induce apoptosis of MM cells in vitro. Optimising the pharmacokinetic profiles of novel STAT3 inhibitors and identifying how best to combine these agents with existing anti-myeloma therapy are key questions to be addressed in future clinical trials.

S-nitrosylation of the Peroxiredoxin-2 promotes S-nitrosoglutathione-mediated lung cancer cells apoptosis via AMPK-SIRT1 pathway

Protein S-nitrosylation, the redox-based posttranslational modification of a cysteine thiol by the attachment of a nitric oxide (NO) group, is responsible for a variety of signaling effects. Dysregulation of S-nitrosylation may be directly linked to cancer apoptotic resistance and cancer therapy outcomes, emphasizing the importance of S-nitrosylation in cancer. Peroxiredoxin-2 (Prdx2), an antioxidant enzyme, plays an important role in the protection of cancer cells from oxidative radical damage caused by hydrogen dioxide (H₂O₂), which is a potential target for cancer therapy. Our studies showed that, as an endogenous NO carrier, S-nitrosoglutathione (GSNO) induced apoptosis in lung cancer cells via nitrosylating Prdx2. The nitrosylation of Prdx2 at Cys51 and Cys172 sites disrupted the formation of Prdx2 dimer and repressed the Prdx2 antioxidant activity, causing the accumulation of endogenous H₂O₂. H₂O₂ activated AMPK, which then phosphorylated SIRT1 and inhibited its deacetylation activity toward p53 in A549 cells or FOXO1 in NCI-H1299 cells. Taken together, our results elucidate the roles and mechanisms of Prdx2 S-nitrosylation at Cys51 and Cys172 sites in lung cancer cells apoptosis and this finding provides an effective lung cancer treatment strategy for managing aberrant Prdx2 activity in lung cancers.

Regulation of ezrin tension by S-nitrosylation mediates non-small cell lung cancer invasion and metastasis

Cancer invasion and metastasis depend on accurate and rapid modulation of both chemical and mechanical activities. The S-nitrosylation (SNO) of membrane cytoskeletal cross-linker protein ezrin may regulate the malignant process in a tension-dependent manner. Methods: The level of nitrosylated ezrin in non-small cell lung cancer (NSCLC) tissues and A549 cell line were evaluated by biotin-switch assay. A few cysteine mutated plasmids of ezrin were used to identify active site for SNO. Newly designed ezrin or mutated-ezrin tension probes based on Förster resonance energy transfer (FRET) theory were applied to visually observe real-time tension changes. Cytoskeleton depolymerizing and motor molecular inhibiting experiments were performed to reveal the alternation of the mechanical property of ezrin after SNO. Transwell assays and xenograft mouse model were used to assess aggressiveness of A549 cells in different groups. Fluorescent staining was also applied to examine cellular location and structures. Results: High inducible nitric oxide synthase (iNOS) levels were observed to induce ezrin-SNO, and then promote malignant behaviors of NSCLC cells both in vitro and in vivo. Cys¹¹⁷ was identified as the only active site for ezrin-SNO. Meanwhile, an increased level of ezrin tension was observed after iNOS-induced SNO. Enhanced ezrin tension was positively correlated with aggressiveness of NSCLC. Moreover, Microfilament (MF) forces instead of microtubule (MT) forces played dominant roles in modulating ezrin tension, especially after ezrin nitrosylation. Conclusion: This study revealed a SNO-associated mechanism underlying the mechanical tension of ezrin. Ezrin-SNO promotes NSCLC cells invasion and metastasis through facilitating mechanical transduction from the cytoskeleton to the membrane. These studies implicate the therapeutic potential by targeting ezrin in the inhibition NSCLC invasion and metastasis.

USP15 inhibits multiple myeloma cell apoptosis through activating a feedback loop with the transcription factor NF-κBp65

USP15 has been shown to stabilize transcription factors, to be amplified in many cancers and to mediate cancer cell survival. However, the underlying mechanism by which USP15 regulates multiple myeloma (MM) cell proliferation and apoptosis has not been established. Here, our results showed that USP15 mRNA expression was upregulated in MM patients. USP15 silencing induced MM cell proliferation inhibition, apoptosis, and the expression of nuclear and cytoplasmic NF-κBp65, while USP15 overexpression exhibited an inverse effect. Moreover, in vivo experiments indicated that USP15 silencing inhibited MM tumor growth and NF-κBp65 expression. PDTC treatment significantly inhibited USP15 overexpression-induced cell proliferation, apoptosis inhibition, and NF-κBp65 expression. USP15 overexpression promoted NF-κBp65 expression through inhibition of its ubiquitination, whereas NF-κBp65 promoted USP15 expression as a positive regulator. Taken together, the USP15-NF-κBp65 loop is involved in MM tumorigenesis and may be a potential therapeutic target for MM.

Researchers may have found a new target for treatment of multiple myeloma (MM), a common type of blood cancer. MM develops in plasma cells, white blood cells that fight infection, and is very difficult to treat. Ubiquitins, small regulatory proteins which tag proteins for destruction, have been implicated in development of many cancers. Jian Hou at Ren Ji Hospital and Weijun Fu at Changzheng Hospital, both in Shanghai, China, investigated how one ubiquitin, USP15, is involved in MM. Patients with MM showed higher levels of USP15, and MM cells supplied with additional USP15 multiplied more rapidly. Treating MM mice with USP15 inhibitors slowed tumor growth. Further investigation showed that USP15 interacts with another molecule known to be involved in development of many cancers. These results may help to develop alternative treatments for multiple myeloma.

S-nitrosoglutathione reductase (GSNOR) inhibitor as an immune modulator in experimental autoimmune encephalomyelitis

We previously reported that S-nitrosoglutathione (GSNO), an endogenous nitric oxide carrier, attenuated T_H17-mediated immune responses in experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis (MS). Cellular GSNO homeostasis is regulated via its synthesis by reaction between nitric oxide and glutathione and its enzymatic catabolism by GSNO reductase (GSNOR). In this study, we evaluated potential of reversible inhibitor of GSNOR (N6022) in comparison with exogenous GSNO in immunopathogenesis of EAE. Daily treatment of EAE mice with N6022 or exogenous GSNO significantly attenuated the clinical disease of EAE, but N6022 treatment showed greater efficacy than GSNO. Both N6022 and exogenous GSNO treatments increased the spleen levels of GSNO, as documented by increased protein-associated S-nitrosothiols, and inhibited polarization and CNS effector function of proinflammatory T_H17 cells while inducing the polarization and CNS effector function of anti-inflammatory CD4⁺ CD25⁺ FOXP3^- regulatory T (Treg) cells. Moreover, N6022 further attenuated T_H1 while inducing T_H2 and CD4⁺ CD25⁺ FOXP3⁺ Treg in their polarization and CNS effector functions. Similar to GSNO, the N6022 treatment protected against the EAE disease induced demyelination. However, neither exogenous GSNO nor N6022 treatment did not cause significant systemic lymphopenic effect as compared to FTY720. Taken together, these data document that optimization of cellular GSNO homeostasis by GSNOR inhibitor (N6022) in NO metabolizing cells attenuates EAE disease via selective inhibition of pro-inflammatory subsets of CD4⁺ cells (T_H1/T_H17) while upregulating anti-inflammatory subsets of CD4⁺ cells (T_H2/Treg) without causing lymphopenic effects and thus offers a potential treatment option for MS/EAE.

Bavachin induces the apoptosis of multiple myeloma cell lines by inhibiting the activation of nuclear factor kappa B and signal transducer and activator of transcription 3

Bavachin is a phytoestrogen purified from natural herbal plants such as Psoralea corylifolia. In this study, we examined the effect of bavachin in multiple myeloma (MM) cell lines. We found that bavachin decreased the viability of MM cell lines, but was not cytotoxic towards normal cells. It inhibited the activation of nuclear factor kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT3). Furthermore, bavachin increased the expression of p53 and NOXA, and decreased the expression of X-linked inhibitor of apoptosis protein (XIAP), survivin, B cell lymphoma-extra large (Bcl-xL), and Bcl-2. Additionally, bavachin induced apoptosis by the activation of caspase-3 and caspase-9, implicating the involvement of the mitochondrial pathway. Our results suggest that bavachin induces apoptosis through the inhibition of NF-κB and STAT3 activation in MM cell lines. Most importantly, few NF-κB and STAT3 inhibitors with high efficiency, specificity, and safety are currently available for clinical cancer therapy. Hence, bavachin, which targets NF-κB and STAT3, is a potential anticancer agent for the treatment of MM.

Troxerutin (TXN) potentiated 5-Fluorouracil (5-Fu) treatment of human gastric cancer through suppressing STAT3/NF-κB and Bcl-2 signaling pathways

Gastric cancer still presents a significant problem for public health worldwide. Troxerutin (TXN), a flavonoid present in tea, coffee, cereal grains, and a variety of fruits and vegetables, exhibits various pharmacological and biological activities in vitro and in vivo. We investigated the ability of TXN to reverse the in vitro and in vivo drug resistance of human gastric cancer cells, which were resistant to treatment of 5-Fluorouracil (5-FU). 5-Fu is a pyrimidine analog, which is widely used in the treatment of cancers. Here, we found the growth inhibitory effects of TXN on human gastric cancer cell, resistant to 5-FU. TXN and 5-FU co-treatment resulted in a dose-dependent suppression of the cell proliferation. Decreasing of phosphorylated signal transducers and activation of transcription 3 (STAT3) was included in suppression of p65 by TXN with 5-FU in combination. Additionally, the presence of TXN sensitized gastric cancer cells resistant to 5-FU to 5-FU-induced apoptosis by suppressing Bcl-2. The pro-apoptotic proteins of Bax and Bid were up-regulated, accompanied with Caspase cleavage, leading to apoptosis. Moreover, in mice xenograft models, the combined therapy inhibited tumor growth compared to the TXN or 5-FU treatment alone. Our data indicated a novel therapeutic strategy to potentiate 5-FU-induced anti-tumor effect in gastric cancer cells with resistance to 5-FU by TXN through suppression of p-STAT3/NF-κB (p65 and p50) and Bcl-2.

Crocin Suppresses Constitutively Active STAT3 Through Induction of Protein Tyrosine Phosphatase SHP-1

The aim of the present study is to investigate the effect of a natural compound crocin, one of the active components of saffron, on human multiple myeloma cells. Crocin effectively suppressed constitutive STAT3 activation, translocation of STAT3 to the nucleus, and its target gene expression. The suppression of STAT3 was mediated through the inhibition of activation of protein tyrosine kinases JAK1, JAK2, and c-Src. We found that crocin induced the expression of SHP-1, a tyrosine protein phosphatase, and pervanadate treatment reversed the crocin-induced downregulation of STAT3, suggesting the involvement of a protein tyrosine phosphatase. Moreover, suppression of SHP-1 by its inhibitor overturned the effect of crocin on induction of SHP-1 and the inhibition of STAT3 activation. Finally, crocin downregulated the expression of STAT3-mediated gene products including anti-apoptotic (Bcl-2), pro-apoptotic (BAX), invasive (CXCR4), angiogenic (VEGF), and cell cycle regulator (cyclin D1), which are correlated with suppression of proliferation, the accumulation of cells in sub-G1 phase of cell cycle, and induction of apoptosis. Overall, our results suggested that crocin is a novel inhibitor of STAT3 activation pathway and thus may have potential in prevention and treatment of human multiple myeloma. J. Cell. Biochem. 118: 3290-3298, 2017. © 2017 Wiley Periodicals, Inc.