More than Just an Immunosuppressant: The Emerging Role of FTY720 as a Novel Inducer of ROS and Apoptosis

Fingolimod hydrochloride (FTY720) is a first-in-class of sphingosine-1-phosphate (S1P) receptor modulator approved to treat multiple sclerosis by its phosphorylated form (FTY720-P). Recently, a novel role of FTY720 as a potential anticancer drug has emerged. One of the anticancer mechanisms of FTY720 involves the induction of reactive oxygen species (ROS) and subsequent apoptosis, which is largely independent of its property as an S1P modulator. ROS have been considered as a double-edged sword in tumor initiation/progression. Intriguingly, prooxidant therapies have attracted much attention due to its efficacy in cancer treatment. These strategies include diverse chemotherapeutic agents and molecular targeted drugs such as sulfasalazine which inhibits the CD44v-xCT (cystine transporter) axis. In this review, we introduce our recent discoveries using a chemical genomics approach to uncover a signaling network relevant to FTY720-mediated ROS signaling and apoptosis, thereby proposing new potential targets for combination therapy as a means to enhance the antitumor efficacy of FTY720 as a ROS generator. We extend our knowledge by summarizing various measures targeting the vulnerability of cancer cells’ defense mechanisms against oxidative stress. Future directions that may lead to the best use of FTY720 and ROS-targeted strategies as a promising cancer treatment are also discussed

A genome-wide screen for FTY720-sensitive mutants reveals genes required for ROS homeostasis

Fingolimod hydrochloride (FTY720), a sphingosine-1-phosphate (S1P) analogue, is an approved immune modulator for the treatment of multiple sclerosis (MS). Notably, in addition to its well-known mode of action as an S1P modulator, accumulating evidence suggests that FTY720 induces apoptosis in various cancer cells via reactive oxygen species (ROS) generation. Although the involvement of multiple signaling molecules, such as JNK (Jun N-terminal kinase), Akt (alpha serine/threonine-protein kinase) and Sphk has been reported, the exact mechanisms how FTY720 induces cell growth inhibition and the functional relationship between FTY720 and these signaling pathways remain elusive. Our previous reports using the fission yeast Schizosaccharomyces pombe as a model system to elucidate FTY720-mediated signaling pathways revealed that FTY720 induces an increase in intracellular Ca2+ concentrations and ROS generation, which resulted in the activation of the transcriptional responses downstream of Ca2+/calcineurin signaling and stress-activated MAPK signaling, respectively. Here, we performed a genome-wide screening for genes whose deletion induces FTY720-sensitive growth in S. pombe and identified 49 genes. These gene products are related to the biological processes involved in metabolic processes, transport, transcription, translation, chromatin organization, cytoskeleton organization and intracellular signal transduction. Notably, most of the FTY720-sensitive deletion cells exhibited NAC-remedial FTY720 sensitivities and dysregulated ROS homeostasis. Our results revealed a novel gene network involving ROS homeostasis and the possible mechanisms of the FTY720 toxicity

Serum Mac-2-binding protein glycosylation isomer predicts esophagogastric varices in cirrhotic patients with chronic hepatitis C virus infection treated with IFN-free direct-acting antiviral agent: M2BPGi levels predict varices in SVR patients

Introduction and objectives: We examined whether Mac-2-binding protein glycosylation isomer (M2BPGi) levels could be a predictive marker for the presence of esophagogastric varices (EGV) in cirrhotic patients after hepatitis C virus (HCV) eradication with direct-acting antivirals (DAAs). Patients and methods: A total of 102 cirrhotic patients with HCV infection treated with DAAs were enrolled. Esophagogastroduodenoscopy was performed in 84 of the patients before treatment (Cohort A), in 66 after treatment (Cohort B), and in 48 at both time points (Cohort C). We examined factors associated with EGV before and after DAA treatment. Results: In Cohort A, M2BPGi levels and liver stiffness were significantly higher in the EGV-positive group than the EGV-negative group (p = 0.034, and p = 0.042, respectively). The proportion of EGV-positive patients with before-treatment levels of M2BPGi ≧ 7.3 C.O.I. was significantly higher than in patients with M2BPGi levels < 7.3 C.O.I. (p = 0.015). In Cohort B, M2BPGi levels were significantly higher in the EGV-positive group than EGV-negative group (p = 0.003). The proportion of EGV-positive patients with after-treatment levels of M2BPGi ≧ 3.4 C.O.I. was significantly higher than in patients with M2BPGi levels < 3.4 C.O.I. (p = 0.001). In Cohort C, M2BPGi levels decreased during DAA treatment regardless of EGV development, but there was no significant difference in the reduction of M2BPGi among the EGV-improvement, EGV-invariant, and EGV-exacerbation groups (p = 0.659). Conclusions: M2BPGi levels may be a novel serum marker for the presence of EGV before and after DAA treatment

Sip1, a conserved AP-1 accessory protein, is important for Golgi/endosome trafficking in fission yeast.

We had previously identified the mutant allele of apm1(+) that encodes a homolog of the mammalian μ 1A subunit of the clathrin-associated adaptor protein-1 (AP-1) complex and demonstrated that the AP-1 complex plays a role in Golgi/endosome trafficking, secretion, and vacuole fusion in fission yeast. Here, we isolated a mutant allele of its4(+)/sip1(+), which encodes a conserved AP-1 accessory protein. The its4-1/sip1-i4 mutants and apm1-deletion cells exhibited similar phenotypes, including sensitivity to the calcineurin inhibitor FK506, Cl(-) and valproic acid as well as various defects in Golgi/endosomal trafficking and cytokinesis. Electron micrographs of sip1-i4 mutants revealed vacuole fragmentation and accumulation of abnormal Golgi-like structures and secretory vesicles. Overexpression of Apm1 suppressed defective membrane trafficking in sip1-i4 mutants. The Sip1-green fluorescent protein (GFP) co-localized with Apm1-mCherry at Golgi/endosomes, and Sip1 physically interacted with each subunit of the AP-1 complex. We found that Sip1 was a Golgi/endosomal protein and the sip1-i4 mutation affected AP-1 localization at Golgi/endosomes, thus indicating that Sip1 recruited the AP-1 complex to endosomal membranes by physically interacting with each subunit of this complex. Furthermore, Sip1 is required for the correct localization of Bgs1/Cps1, 1,3-β-D-glucan synthase to polarized growth sites. Consistently, the sip1-i4 mutants displayed a severe sensitivity to micafungin, a potent inhibitor of 1,3-β-D-glucan synthase. Taken together, our findings reveal a role for Sip1 in the regulation of Golgi/endosome trafficking in coordination with the AP-1 complex, and identified Bgs1, required for cell wall synthesis, as the new cargo of AP-1-dependent trafficking

Outcomes for Cirrhotic Patients with Hepatitis C Virus 1b Treated with Asunaprevir and Daclatasvir Combination

Background: The efficacy and safety of asunaprevir + daclatasvir combination therapy for treatment of hepatitis C virus (HCV) in compensated cirrhotic patients was not fully evaluated in real-world. Outcomes were assessed in cirrhotic patients with sustained viral response (SVR). Material and methods: A total of 145 patients without resistance-associated substitutions (RASs) at L31 and Y93 in the nonstructural protein 5A of HCV genotype 1b, consisting of 49 hepatic cirrhotic and 96 non-cirrhotic patients, were enrolled to the therapy. The patients were treated with 100 mg asunaprevir twice daily plus 60 mg daclatasvir once daily for 24 weeks. The primary endpoint was SVR 24 weeks after completing treatment. In addition, we evaluated the improvement of liver function and development of HCC for 1 year from the end of treatment (EOT). Results: The SVR24 rate was 96% (47/49) in the cirrhotic group and 96% (91/95) in the non-cirrhotic group (p = 0.69). During treatment, grade III/IV adverse events occurred more frequently in cir-rhotic patients (10/49; 20.4%) than in non-cirrhotic patients (10/96; 10.4%) (p = 0.099). After EOT, alanine aminotransferase and AFP levels were significantly decreased in cirrhotic patients with SVR. In addition, serum levels of albumin and platelet counts were significantly increased. On the other hand, the rates of HCC recurrence (43%) and development (7.4%) were higher in cirrhotic patients than in the non-cirrhotic patients (12.5% and 1.1%, respectively). Conclusion: RAS-oriented asunaprevir/daclatasvir therapy has a strong anti-HCV effect in patients with HCV genotype 1b. However, careful management is necessary in patients with cirrhosis