S1PR1 predicts patient survival and promotes chemotherapy drug resistance in gastric cancer cells through STAT3 constitutive activation.

BACKGROUND: S1PR1-STAT3 inter-regulatory loop was initially suggested to be oncogenic in several cancer cells. However, the clinical relevance of this mechanism in tumor progression, disease prognosis and drug response was not established. METHODS: The correlations between S1PR1 transcription, overall survival and chemotherapy response of GC patients were tested using a large clinical database. The relevance of S1PR1 expression and STAT3 activation in both tumor tissues and cancer cell lines was also tested. The effect of S1PR1 high expression achieved by persistent STAT3 activation on tumor cell drug resistance was investigated in vitro and in vivo. FINDINGS: An enhanced S1PR1 expression was highly related with a reduced overall survival time and a worse response to chemotherapy drug and closer correlation to STAT3 in gastric cancer patients. The issue chip analysis showed that the expressions of S1PR1 and STAT3 activation were increased in higher graded gastric cancer (GC) tissues. Cellular studies supported the notion that the high S1PR1 expression was responsible for drug resistance in GC cells through a molecular pattern derived by constitutive activation of STAT3. The disruption of S1PR1-STAT3 signaling significantly re-sensitized drug resistance in GC cells in vitro and in vivo. INTERPRETATION: S1PR1-STAT3 signaling may participate drug resistance in GC, thus could serve as a drug target to increase the efficacy of GC treatment. FUND: This work was supported by the National Natural Science Foundation of China (No. 81570775, 81471095), the grant from the research projects in traditional Chinese medicine industry of China (No. 201507004-2).

The transcription factor KLF2 restrains CD4⁺ T follicular helper cell differentiation.

T follicular helper (Tfh) cells are essential for efficient B cell responses, yet the factors that regulate differentiation of this CD4(+) T cell subset are incompletely understood. Here we found that the KLF2 transcription factor serves to restrain Tfh cell generation. Induced KLF2 deficiency in activated CD4(+) T cells led to increased Tfh cell generation and B cell priming, whereas KLF2 overexpression prevented Tfh cell production. KLF2 promotes expression of the trafficking receptor S1PR1, and S1PR1 downregulation is essential for efficient Tfh cell production. However, KLF2 also induced expression of the transcription factor Blimp-1, which repressed transcription factor Bcl-6 and thereby impaired Tfh cell differentiation. Furthermore, KLF2 induced expression of the transcription factors T-bet and GATA3 and enhanced Th1 differentiation. Hence, our data indicate KLF2 is pivotal for coordinating CD4(+) T cell differentiation through two distinct and complementary mechanisms: via control of T cell localization and by regulation of lineage-defining transcription factors.

Expression of sphingosine 1-phosphate 1-3 on penile cavernous tissue in hypertensive and normotensive rats.

OBJECTIVE: To investigate the expression of sphingosine 1-phosphate 1-3 (S1P1-3) on penile cavernous tissues in hypertensive and normotensive rats and its association with erectile function. METHODS: Ten 14-week-old male spontaneously hypertensive rats (SHRs) and 10 male age-matched normotensive Wistar-Kyoto rats were randomly designated as hypertensive rat group and normotensive control group, respectively. Mean blood pressure, serum testosterone, and maximum intracavernosal pressure/mean arterial pressure (ICPmax-to-MAP ratio) were measured. The expression of S1P1-3, endothelial nitric oxide synthase (eNOS), phosphorylated eNOS (P-eNOS), and rho-associated protein kinase 1-2 (ROCK1-2) was determined in the cavernous tissues of SHRs and Wistar-Kyoto rats by the immunohistochemical study and Western blot. RESULTS: There was no significant difference in body weight and serum testosterone levels between the 2 groups. The MAP in the hypertensive rat group was significantly increased compared with the control group. After 3- and 5-V electrostimulation, the ICPmax-to-MAP ratio in the control group was significantly increased compared with the hypertensive rat group. The protein expression of eNOS, P-eNOS, and S1P1 was significantly higher in the control group than in the hypertensive rat group (P <.05). The protein expression of S1P2, S1P3, and ROCK1-2 was significantly lower in the normotensive control group than in the hypertensive rat group (P <.05). CONCLUSION: Hypertension may impair the erectile function by means of downregulating the expression of S1P1 and upregulating the expression of S1P2-3 in cavernous tissues of SHRs.

Anti-sphingosine-1-phosphate monoclonal antibodies inhibit angiogenesis and sub-retinal fibrosis in a murine model of laser-induced choroidal neovascularization.

The efficacy of novel monoclonal antibodies that neutralize the pro-angiogenic mediator, sphingosine-1-phosphate (S1P), were tested using in vitro and in vivo angiogenesis models, including choroidal neovascularization (CNV) induced by laser disruption of Bruch's membrane. S1P receptor levels in human brain choroid plexus endothelial cells (CPEC), human lung microvascular endothelial cells, human retinal vascular endothelial cells, and circulating endothelial progenitor cells were examined by semi-quantitative PCR. The ability of murine or humanized anti-S1P monoclonal antibodies (mAbs) to inhibit S1P-mediated microvessel tube formation by CPEC on Matrigel was evaluated and capillary density in subcutaneous growth factor-loaded Matrigel plugs was determined following anti-S1P treatment. S1P promoted in vitro capillary tube formation in CPEC consistent with the presence of cognate S1P(1-5) receptor expression by these cells and the S1P antibody induced a dose-dependent reduction in microvessel tube formation. In a murine model of laser-induced rupture of Bruch's membrane, S1P was detected in posterior cups of mice receiving laser injury, but not in uninjured controls. Intravitreous injection of anti-S1P mAbs dramatically inhibited CNV formation and sub-retinal collagen deposition in all treatment groups (p<0.05 compared to controls), thereby identifying S1P as a previously unrecognized mediator of angiogenesis and subretinal fibrosis in this model. These findings suggest that neutralizing S1P with anti-S1P mAbs may be a novel method of treating patients with exudative age-related macular degeneration by reducing angiogenesis and sub-retinal fibrosis, which are responsible for visual acuity loss in this disease.

Sphingosine 1-phosphate (S1P) signaling is required for maintenance of hair cells mainly via activation of S1P2.

Hearing requires the transduction of vibrational forces by specialized epithelial cells in the cochlea known as hair cells. The human ear contains a finite number of terminally differentiated hair cells that, once lost by noise-induced damage or toxic insult, can never be regenerated. We report here that sphingosine 1-phosphate (S1P) signaling, mainly via activation of its cognate receptor S1P2, is required for the maintenance of vestibular and cochlear hair cells in vivo. Two S1P receptors, S1P2 and S1P3, were found to be expressed in the cochlea by reverse transcription-PCR and in situ hybridization. Mice that are null for both these receptors uniformly display progressive cochlear and vestibular defects with hair cell loss, resulting in complete deafness by 4 weeks of age and, with complete penetrance, balance defects of increasing severity. This study reveals the previously unknown role of S1P signaling in the maintenance of cochlear and vestibular integrity and suggests a means for therapeutic intervention in degenerative hearing loss.

The immune modulator FTY720 targets sphingosine-kinase-dependent migration of human monocytes in response to amyloid beta-protein and its precursor.

Accumulation of inflammatory mononuclear phagocytes in Alzheimer's senile plaques, a hallmark of the innate immune response to beta-amyloid fibrils, can initiate and propagate neurodegeneration characteristic of Alzheimer's disease. Phagocytes migrate toward amyloid beta-protein involving formyl peptide receptor like-1-dependent signaling. Using human peripheral blood monocytes in Boyden chamber micropore filter assays, we show that the amyloid beta-protein- and amyloid beta-precursor protein-induced migration was abrogated by dimethylsphingosine, a sphingosine kinase inhibitor. Amyloid beta-protein stimulated in monocytes the gene expression for sphingosine-1-phosphate receptors 2 and 5, but not 1, 3, and 4. FTY720 that acts as a sphingosine-1-phosphate receptor agonist after endogenous phosphorylation by sphingosine kinase, as well as various neuropeptides that are known to be monocyte chemoattractants, dose-dependently inhibited amyloid beta-protein-induced migration. These data demonstrate that the migratory effects of beta-amyloid in human monocytes involve spingosine-1-phosphate signaling. Whereas endogenous neuropeptides may arrest and activate monocytes at sites of high beta-amyloid concentrations, interference with the amyloid beta-protein-dependent sphingosine-1-phosphate pathway in monocytes by FTY720, a novel immunomodulatory drug, suggests that FTY720 may be efficacious in beta-amyloid-related inflammatory diseases.