Sphingosine kinase 1 promotes tumor progression and confers malignancy phenotypes of colon cancer by regulating the focal adhesion kinase pathway and adhesion molecules

ZFHX2-AS1 interacts with DKC1 to regulate ARHGAP5 pseudouridylation and suppress ovarian cancer progression

Ovarian cancer (OCa) remains a highly lethal disease, largely due to late-stage diagnosis and limited treatment options for recurrent metastatic tumors. Long non-coding RNAs (lncRNAs) have been recognized as key regulators of cancer hallmarks, yet their specific roles in driving OCa progression are not fully understood. In this study, we employed an integrated approach combining clinical correlation, functional assays, and mechanistic investigations to reveal that lncRNA ZFHX2-AS1 is significantly downregulated in OCa tissues and cells, with its reduced expression associated with poor clinical outcomes. Using in vitro and in vivo models, we demonstrated that overexpression of ZFHX2-AS1 suppresses OCa cell proliferation, migration and invasion, whereas ZFHX2-AS1 knockdown enhances these malignant phenotypes. Mechanistically, we defined that ZFHX2-AS1 interacts with and attenuates the enzymatic activity of the pseudouridine synthase DKC1, thereby reducing pseudouridylation and stabilizing the oncogenic ARHGAP5 mRNA. Re-expression of ARHGAP5 could partially reverse the tumor-suppressive effects of ZFHX2-AS1. Further, we found that ARHGAP5 promotes epithelial-mesenchymal transition (EMT) by regulating Rho GTPases activities, and that ZFHX2-AS1 inhibits EMT in OCa by downregulating ARHGAP5 expression and suppressing the Rho GTPase signaling pathway. Taken together, our findings identify ZFHX2-AS1 as a potent tumor suppressor in OCa, acting through the modulation of DKC1-mediated pseudouridylation of ARHGAP5 and the inhibition of the Rho GTPase pathway, thus offering a potential therapeutic target for combating OCa progression.

High expression levels of S1PR3 and PDGFRB indicates unfavorable clinical outcomes in colon adenocarcinoma

Background

Studies verified that sphingosine kinase 1 (SPHK1)/sphingosine 1-phosphate receptors (S1PRs) and platelet-derived growth factor receptors (PDGFRs) play important roles in tumor occurrence and progression. However, the expression and clinical value of SPHK1/S1PRs and PDGFRs in colon adenocarcinoma (COAD) remains unclear. This study aimed to explore the expression of SPHK1/S1PRs and PDGFRs in COAD and further investigate their roles in predicting the prognosis of patients with COAD.

Methods

SPHK1/S1PRs and PDGFRs expression in tissues from patient with COAD were analyzed using The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases. Kaplan-Meier survival analysis was used to evaluate the prognostic roles of SPHK1/S1PRs and PDGFRs in patients with COAD. Spearman's correlation analysis was performed to assess the relationship between SPHK1/S1PRs and PDGFRs in COAD. Then, χ2 test was performed to analyze the correlation between SPHK1/S1PR3/PDGFRB and clinicopathological characteristics of the patients. Additionally, possible signaling pathways co-regulated by S1PR3 and PDGFRB were predicted using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analyses. Least absolute shrinkage and selection operator (LASSO) regression was used to identify hub genes that co-regulated S1PR3 and PDGFRB expression. A prognostic model based on hub genes was constructed for patients with COPD. Finally, the relationship between the hub genes and tumor immune cell infiltration was investigated.

Results

The expression levels of SPHK1 and PDGFRB were significantly upregulated in COAD patient tissues (P < 0.001 and P < 0.001, respectively). Moreover, Kaplan-Meier analysis showed that patients with COAD with high expression levels of SPHK1 and S1PR3 had shorter overall survival (OS) than those with low expression levels (P = 0.013 and P = 0.005, respectively). Spearman's correlation analysis verified a strong positive correlation (P < 0.001, r = 0.790) between the expression of S1PR3 and PDGFRB. In addition, we found that high SPHK1 and PDGGRB expression levels were associated with perineural invasion (P < 0.001 and P = 0.011, respectively). High expression of S1PR3 and PDGGRB was prominently associated with N stage (P = 0.002 and P = 0.021, respectively). High levels of SPHK1, S1PR3, and PDGFRB were associated with lymph node invasion. (P = 0.018, P = 0.004, and P = 0.001, respectively). GO and KEGG results revealed that S1PR3 and PDGFRB may participate in COAD cell extracellular matrix organization and cellular signal transduction. Five hub genes, SFRP2, GPRC5B, RSPO3, FGF14, and TCF7L1, were identified using LASSO regression. Survival analysis showed that the OS in the high-risk group was remarkably shorter than that in the low-risk group. The results indicated that tumor immune cells were significantly increased in the high-risk group compared to those in the low-risk group.

Conclusions

S1PR3 and PDGFRB may be important markers for predicting lymphatic metastasis and poor prognosis in patients with COAD. The underlying mechanisms may involve immune cell infiltration.

LC-MS-based serum metabolomics analysis for the screening and monitoring of colorectal cancer

Background

Colorectal Cancer (CRC) is a prevalent digestive system tumour with significant mortality and recurrence rates. Serum metabolomics, with its high sensitivity and high throughput, has shown potential as a tool to discover biomarkers for clinical screening and monitoring of the CRC patients.

Methods

Serum metabolites of 61 sex and age-matched healthy controls and 62 CRC patients (before and after surgical intervention) were analyzed using a ultra-performance liquid chromatography-high resolution mass spectrometer (UPLC-MS). Statistical methods and pathway enrichment analysis were used to identify potential biomarkers and altered metabolic pathways.

Results

Our analysis revealed a clear distinction in the serum metabolic profile between CRC patients and healthy controls (HCs). Pathway analysis indicated a significant association with arginine biosynthesis, pyrimidine metabolism, pantothenate, and CoA biosynthesis. Univariate and multivariate statistical analysis showed that 9 metabolites had significant diagnostic value for CRC, among them, Guanosine with Area Under the Curve (AUC) values of 0.951 for the training group and0.998 for the validation group. Furthermore, analysis of four specific metabolites (N-Phenylacetylasparticacid, Tyrosyl-Gamma-glutamate, Tyr-Ser and Sphingosine) in serum samples of CRC patients before and after surgery indicated a return to healthy levels after an intervention.

Conclusion

Our results suggest that serum metabolomics may be a valuable tool for the screening and monitoring of CRC patients.

Prognosis-related metabolic genes in the development of colorectal cancer progress and perspective

Colorectal cancer (CRC) is one of the most commonplace malignant tumors in the world. The occurrence and development of CRC are involved in numerous events. Metabolic reprogramming is one of the hallmarks of cancer and is convoluted and associated with carcinogenesis. Lots of metabolic genes are involved in the occurrence and progression of CRC. Study methods combining tumor genomics and metabolomics are more likely to explore this field in depth. In this mini-review, we make the latest progress and future prospects into the different molecular mechanisms of seven prognosis-related metabolic genes, we screened out in previous research, involved in the occurrence and development of CRC.

Roles of intercellular cell adhesion molecule-1 (ICAM-1) in colorectal cancer: expression, functions, prognosis, tumorigenesis, polymorphisms and therapeutic implications

Colorectal cancer (CRC) is a major global health problem and one of the major causes of cancer-related death worldwide. It is very important to understand the pathogenesis of CRC for early diagnosis, prevention strategies and identification of new therapeutic targets. Intercellular adhesion molecule-1 (ICAM-1, CD54) displays an important role in the the pathogenesis of CRC. It is a cell surface glycoprotein of the immunoglobulin (Ig) superfamily and plays an essential role in cell-cell, cell-extracellular matrix interaction, cell signaling and immune process. It is also expressed by tumor cells and modulates their functions, including apoptosis, cell motility, invasion and angiogenesis. The interaction between ICAM-1 and its ligand may facilitate adhesion of tumor cells to the vascular endothelium and subsequently in the promotion of metastasis. ICAM-1 expression determines malignant potential of cancer. In this review, we will discuss the expression, function, prognosis, tumorigenesis, polymorphisms and therapeutic implications of ICAM-1 in CRC.

High expression of phosphorylated focal adhesion kinase predicts a poor prognosis in human colorectal cancer

Background: Phosphorylated Focal adhesion kinase (FAK) has been reported to be intimately involved in various malignant tumors. The effect of p-FAK on colorectal cancer (CRC) is still disputable. The purpose of this study is to investigate the role of p-FAK in the prognosis of colorectal cancer. Methods: The clinical significance of p-FAK expression in CRC was evaluated by immunohistochemistry in a large cohort, including carcinoma and para-carcinoma tissues from 908 patients, and normal tissues, adenoma, and metastasis tissues. The correlation between p-FAK expression and CRC occurrence was investigated in tumor and other tissues. Factors contributing to prognosis were evaluated using Kaplan-Meier survival analysis and Cox regression model. Results: p-FAK is apparently overexpressed in CRC and metastasis tissues. Compared with low p-FAK expression, patients with high p-FAK expression had shorter overall survival [hazard ratio (HR), 2.200; 95% confidence interval (CI), 1.265-3.452; p < 0.01] and disease-free survival (HR, 2.004; 95% CI 1.262-3.382; p < 0.01) in multivariate Cox analysis after adjusting other prognostic factors. High p-FAK expression was also related to a worse chemotherapeutic response in patients who achieved adjuvant chemotherapy (p < 0.01). Conclusion: Expression level of p-FAK is an independent risk factor and can serve as a prognostic biomarker for CRC. High p-FAK expression predicts an unfavorable prognosis of CRC as well as poor chemotherapeutic response.

Increased Sphingosine Kinase 1 Expression Is Associated with Poor Prognosis in Human Solid Tumors: A Meta-Analysis

Methods

PubMed, Web of Science, Embase, CNKI, and Wanfang databases were thoroughly searched for eligible studies, in which the relationship between SPHK1 expression and cancer prognosis was evaluated. Hazard ratios (HRs) and 95% confidence intervals (CIs) were pooled to estimate the impact of SPHK1 expression on cancer patients' survival. Odds ratios (ORs) and 95% CIs were combined to assess the association between SPHK1 expression and clinicopathological characteristics of cancer patients. The certainty of evidence was evaluated by Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) criteria.

Results

Thirty studies comprising 32 cohorts with 5965 patients were included in this meta-analysis. The outcomes indicated that elevated SPHK1 expression was associated with worse overall survival (OS) (HR = 1.71, 95% CI: 1.45-2.01, P < 0.001) and disease-free survival (DFS) (HR = 1.34, 95% CI: 1.13-1.59, P = 0.001). What is more, SPHK1 overexpression was significantly correlated with certain phenotypes of tumor aggressiveness, such as clinical stage (OR = 2.07, 95% CI: 1.39-3.09, P < 0.001), tumor invasion (OR = 2.16, 95% CI: 1.47-3.18, P < 0.001), lymph node metastasis (OR = 2.04, 95% CI: 1.71-2.44, P < 0.001), and distant metastasis (OR = 3.16, 95% CI: 2.44-4.09, P < 0.001). The quality of the evidence for both OS and DFS was low.

Conclusions

Increased SPHK1 expression is related to poor prognosis in human cancers and may serve as a promising prognostic marker and therapeutic target for malignant patients. However, conclusions need to be treated with caution because of lack of high quality of evidence.

PCBP1 regulates the transcription and alternative splicing of metastasis‑related genes and pathways in hepatocellular carcinoma

PCBP1 is a multifunctional RNA-binding protein (RBP) expressed in most human cells and is involved in posttranscriptional gene regulation. PCBP1 regulates the alternative splicing, translation and RNA stability of many cancer-related genes and has been identified as a potential tumour suppressor gene. PCBP1 inhibits the invasion of hepatocellular carcinoma (HCC) cells, but there are few studies on the specific regulatory target and mechanism of RBPs in HCC, and it is unclear whether PCBP1 plays a role in tumour metastasis as a splicing factor. We analysed the regulation of gene expression by PCBP1 at the transcriptional level. We obtained and analysed PCBP1-knockdown RNA-seq data and eCLIP-seq data of PCBP1 in HepG2 cells and found that PCBP1 widely regulates the alternative splicing and expression of genes enriched in cancer-related pathways, including extracellular matrix, cell adhesion, small molecule metabolic process and apoptosis. We validated five regulated alternative splicing events affected by PCBP1 using RT-qPCR and found that there was a significant difference in the expression of APOC1 and SPHK1 between tumour and normal tissues. In this study, we provided convincing evidence that human PCBP1 profoundly regulates the splicing of genes associated with tumour metastasis. These findings provide new insight into potential markers or therapeutic targets for HCC treatment.

Differential Expression of the Sphingolipid Pathway Is Associated with Sensitivity to the PP2A Activator FTY720 in Colorectal Cancer Cell Lines

Protein phosphatase 2A (PP2A) is a ubiquitously expressed intracellular serine/threonine phosphatase. Deregulation of PP2A is a common event associated with adenocarcinomas of the colon and rectum. We have previously shown that breast cancer cell lines are sensitive to the PP2A activator FTY720, and that sensitivity is predicted by high Aurora kinase A (AURKA) mRNA expression. In this study, we hypothesized that high relative AURKA expression could predict sensitivity to FTY720-induced apoptosis in colorectal cancer (CRC). The CRC cell lines NCI H716, COLO320DM, DLD-1, SW480, and HT-29 show a high relative AURKA expression as compared to LS411N, T84, HCT116, SW48, and LOVO. Following viability assays, LS411N, T84, HCT116, and SW480 were shown to be sensitive to FTY720, whereas DLD-1 and HT-29 were non-sensitive. Hence, AURKA mRNA expression does not predict sensitivity to FTY720 in CRC cell lines. Differentially expressed genes (DEGs) were obtained by comparing the sensitive CRC cell lines (LS411N and HCT116) against the non-sensitive (HT-29 and DLD-1). We found that 253 genes were significantly altered in expression, and upregulation of CERS4, PPP2R2C, GNAZ, PRKCG, BCL2, MAPK12, and MAPK11 suggests the involvement of the sphingolipid signaling pathway, known to be activated by phosphorylated-FTY720. In conclusion, although AURKA expression did not predict sensitivity to FTY720, it is evident that specific CRC cell lines are sensitive to 5 µM FTY720, potentially because of the differential expression of genes involved in the sphingolipid pathway.

LINC00514 promotes lipogenesis and tumor progression in esophageal squamous cell carcinoma by sponging miR‑378a‑5p to enhance SPHK1 expression

Increasing evidence has demonstrated that long non‑coding RNAs serve pivotal roles in tumor development, progression, metastasis and metabolism. However, to the best of our knowledge, the roles and molecular mechanisms of long intergenic nonprotein‑coding RNA 00514 (LINC00514) in esophageal squamous cell carcinoma (ESCC) remain unknown. The present study found that LINC00514 and sphingosine kinase 1 (SPHK1) were both upregulated in ESCC tissues and cells, and their high expression levels were closely associated with Tumor‑Node‑Metastasis stage, lymph node metastasis and poor prognosis of patients with ESCC. Functionally, knockdown of LINC00514 inhibited cell proliferation and invasion, and led to the downregulation of lipogenesis‑related proteins, including SPHK1, fatty acid synthase, acetyl‑coenzyme (Co)A carboxylase α and stearoyl‑CoA desaturase 1, whereas LINC00514 overexpression promoted cell proliferation and invasion in ESCC KYSE150 and KYSE30 cells, and upregulated expression of lipogenesis‑related proteins. Mechanistically, LINC00514 functioned as a competing endogenous RNA by sponging microRNA (miR)‑378a‑5p, resulting in the upregulation of SPHK1, which was accompanied by the activation of lipogenesis‑related pathways, to promote ESCC cell proliferation and invasion. Taken together, these findings suggest that LINC00514 may participate in ESCC lipogenesis, and targeting the LINC00514/miR‑378a‑5p/SPHK1 signaling axis may be a novel and promising therapeutic strategy for management of patients with ESCC.

S1P signaling, its interactions and cross-talks with other partners and therapeutic importance in colorectal cancer

Sphingosine-1-Phosphate (S1P) plays an important role in normal physiology, inflammation, initiation and progression of cancer. Deregulation of S1P signaling causes aberrant proliferation, affects survival, leads to angiogenesis and metastasis. Sphingolipid rheostat is crucial for cellular homeostasis. Discrepancy in sphingolipid metabolism is linked to cancer and drug insensitivity. Owing to these diverse functions and being a potent mediator of tumor growth, S1P signaling might be a suitable candidate for anti-tumor therapy or combination therapy. In this review, with a focus on colorectal cancer we have summarized the interacting partners of S1P signaling pathway, its therapeutic approaches along with the contribution of S1P signaling to various cancer hallmarks.

S1P Lyase Regulates Intestinal Stem Cell Quiescence via Ki-67 and FOXO3

Background: Reduction of the Sphingosine-1-phosphate (S1P) degrading enzyme S1P lyase 1 (SGPL1) initiates colorectal cancer progression with parallel loss of colon function in mice. We aimed to investigate the effect of SGPL1 knockout on the stem cell niche in these mice. Methods: We performed immunohistochemical and multi-fluorescence imaging on tissue sections of wildtype and SGPL1 knockout colons under disease conditions. Furthermore, we generated SGPL1 knockout DLD-1 cells (SGPL1^−/−M.Ex1) using CRISPR/Cas9 and characterized cell cycle and AKT signaling pathway via Western blot, immunofluorescence, and FACS analysis. Results: SGPL1 knockout mice were absent of anti-Ki-67 staining in the stem cell niche under disease conditions. This was accompanied by an increase of the negative cell cycle regulator FOXO3 and attenuation of CDK2 activity. SGPL1^−/−M.Ex1 cells show a similar FOXO3 increase but no arrest of proliferation, although we found a suppression of the PDK1/AKT signaling pathway, a prolonged G1-phase, and reduced stem cell markers. Conclusions: While already established colon cancer cells find escape mechanisms from cell cycle arrest, in vivo SGPL1 knockout in the colon stem cell niche during progression of colorectal cancer can contribute to cell cycle quiescence. Thus, we propose a new function of the S1P lyase 1 in stemness.

Activation of SphK1 by adipocytes mediates epithelial ovarian cancer cell proliferation

Background

Adipocytes, active facilitators of epithelial ovarian cancer (EOC) growth, have been implicated in the link between obesity and EOC. However, the current understanding of the mechanisms underlying adipocyte-induced EOC cell proliferation remains incomplete.

Results

We provide the first evidence showing that sphingosine kinase (SphK) 1 is critical for adipocyte-induced EOC cell proliferation. Adipocytes are capable of activating SphK1, which then leads to extracellular signal-regulated kinase (ERK) phosphorylation. Moreover, adipocyte-induced SphK1 activation is ERK dependent. Furthermore, sphingosine 1-phosphate receptor (S1PR) 1 and S1PR3, key components of the SphK1 signalling pathway, participate in adipocyte-mediated growth-promoting action in EOC cells.

Conclusions

Our study reveals a previously unrecognized role of SphK1 in adipocyte-induced growth-promoting action in EOC, suggesting a new target for EOC therapy.

SphK1 Promotes Cancer Progression through Activating JAK/STAT Pathway and Up-Regulating S1PR1 Expression in Colon Cancer Cells

BACKGROUND

SphK1 is a conserved lipid kinase, which can catalyze formation of tumor promoting factor sphingosine phosphate-1 (S1P).

OBJECTIVE

To investigate effect of SphK1 on proliferation/migration of colon cancer cells and associated mechanisms.

METHODS

Transcription of SphK1 gene in colon cancer cells was detected. Gene transcription of SphK1 was inhibited by transfecting with si-SphK1 gene in colon cancer cells. Effects of SphK1 inhibition (si-SphK1) on cell migration/proliferation were detected using transwell system and MTS. Gene transcription of SIP, S1PR1, S1PR2, S1PR3, and activation of JAK/STAT3 pathway were examined using RT-PCR and western blot assay. S1PR1 over-expressing plasmid was constructed and transfected into cells. Effects of S1PR1 over-expression on migration/proliferation of si-SphK1 transfected colon cancer cells and activation of JAK/STAT3 pathway were determined using RT-PCR and western blotting.

RESULTS

Gene transcription of SphK1 in SW480 and HT-29 colon cancer cells was significantly inhibited by transfection of si-SphK1 gene. Transwell migration and MTS findings showed that si-SphK1 transfection (si-SphK1 group) could reduce migration quantity and cell viability of colon cancer cells compared to negative control (NC) (p<0.0001). SphK1 inhibition (si-SphK1 group) significantly down-regulated S1PR1 and S1PR3 gene transcription in SW480 and HT-29 cells (p<0.0001), and decreased activation level of JAKSTAT3 signaling pathway compared to NC group (p<0.05). Over-expression of S1PR1 reversed inhibitory effects of si-SphK1 on migration/proliferation of SW480 and activation of JAK/Stat3.

CONCLUSION

SphK1 promoted proliferation and migration of colon cancer cells through promoting JAK/STAT activation and up-regulating S1PR1 expression.

Discovery of core gene families associated with liver metastasis in colorectal cancer and regulatory roles in tumor cell immune infiltration

In this study, we aimed to uncover genes that drive the pathogenesis of liver metastasis in colorectal cancer (CRC), and identify effective genes that could serve as potential therapeutic targets for treating with colorectal liver metastasis patients based on two GEO datasets. Several bioinformatics approaches were implemented. First, differential expression analysis screened out key differentially expressed genes (DEGs) across the two GEO datasets. Based on gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, we identified the enrichment functions and pathways of the DEGs that were associated with liver metastasis in CRC. Second, immune infiltration analysis identified key immune signature gene sets associated with CRC liver metastasis, among which two key immune gene families (CD and CCL) identified as key DEGs were filtered by protein-protein interaction (PPI) network. Some of the members in these gene families were associated with disease free survival (DFS) or overall survival (OS) in two subtypes of CRC, namely COAD and READ. Finally, functional enrichment analysis of the two gene families and their neighboring genes revealed that they were closely associated with cytokine, leukocyte proliferation and chemotaxis. These results are valuable in comprehending the pathogenesis of liver metastasis in CRC, and are of seminal importance in understanding the role of immune tumor infiltration in CRC. Our study also identified potentially effective therapeutic targets for liver metastasis in CRC including CCL20, CCL24 and CD70.

Intestinal Epithelial Deletion of Sphk1 Prevents Colitis-Associated Cancer Development by Inhibition of Epithelial STAT3 Activation

BACKGROUND AND AIMS

Colitis-associated cancer (CAC) is one of the most serious complications in patients with inflammatory bowel disease. Sphingosine kinase 1 (Sphk1) is a key enzyme in the sphingolipid pathway and has oncogene potential for inducing both initiation and progression of tumors. The aim of this work is to characterize the role of epithelial Sphk1 in mouse colitis and CAC models.

METHODS

We investigated the roles of Sphk1 in CAC by conditional deletion of Sphk1 in intestinal epithelial cells (IECs).

RESULTS

CAC was induced in both Sphk1^ΔIEC/Apc^Min/+ and Sphk1^IEC/Apc^Min/+ mice by administration of 2% dextran sodium sulfate (DSS) for 7 days. Genetic deletion of Sphk1 significantly reduced the number and size of tumors in Apc^Min/+ mice. Histologic grade was more severe in Sphk1^ΔIEC/Apc^Min/+ mice compared with Sphk1^IEC/Apc^Min/+ mice (invasive carcinoma, 71% versus 13%, p < 0.05). Deletion of Sphk1 decreased mucosal proliferation and inhibited STAT3 activation and genetic expression of cyclin D1 and cMyc in tumor cells. Conditional deletion of Sphk1 using CRISPR-Cas9 in HCT 116 cells inhibited interleukin (IL)-6-mediated STAT3 activation.

CONCLUSIONS

Epithelial conditional deletion of Sphk1 inhibits CAC in Apc^Min/+-DSS models in mice by inhibiting STAT3 activation and its target signaling pathways.

Molecular signature of interleukin-22 in colon carcinoma cells and organoid models

Interleukin (IL)-22 activates STAT (signal transducer and activator of transcription) 3 and antiapoptotic and proproliferative pathways; but beyond this, the molecular mechanisms by which IL-22 promotes carcinogenesis are poorly understood. Characterizing the molecular signature of IL-22 in human DLD-1 colon carcinoma cells, we observed increased expression of 26 genes, including NNMT (nicotinamide N-methyltransferase, ≤10-fold) and CEA (carcinoembryonic antigen, ≤7-fold), both known to promote intestinal carcinogenesis. ERP27 (endoplasmic reticulum protein-27, function unknown, ≤5-fold) and the proinflammatory ICAM1 (intercellular adhesion molecule-1, ≤4-fold) were also increased. The effect on CEA was partly STAT3-mediated, as STAT3-silencing reduced IL-22-induced CEA by ≤56%. Silencing of CEA or NNMT inhibited IL-22-induced proliferation/migration of DLD-1, Caco-2, and SW480 colon carcinoma cells. To validate these results in primary tissues, we assessed IL-22-induced gene expression in organoids from human healthy colon and colon cancer patients, and from normal mouse small intestine and colon. Gene regulation by IL-22 was similar in DLD-1 cells and human and mouse healthy organoids. CEA was an exception with no induction by IL-22 in organoids, indicating the 3-dimensional organization of the tissue may produce signals absent in 2D cell culture. Importantly, augmentation of NNMT was 5-14-fold greater in human cancerous compared to normal organoids, supporting a role for NNMT in IL-22-mediated colon carcinogenesis. Thus, NNMT and CEA emerge as mediators of the tumor-promoting effects of IL-22 in the intestine. These data advance our understanding of the multifaceted role of IL-22 in the gut and suggest the IL-22 pathway may represent a therapeutic target in colon cancer.

Sphingolipids in Non-Alcoholic Fatty Liver Disease and Hepatocellular Carcinoma: Ceramide Turnover

Non-alcoholic fatty liver disease (NAFLD) has emerged as one of the main causes of chronic liver disease worldwide. NAFLD comprises a group of conditions characterized by the accumulation of hepatic lipids that can eventually lead to non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma (HCC), the fifth most common cancer type with a poor survival rate. In this context, several works have pointed out perturbations in lipid metabolism and, particularly, changes in bioactive sphingolipids, as a hallmark of NAFLD and derived HCC. In the present work, we have reviewed existing literature about sphingolipids and the development of NAFLD and NAFLD-derived HCC. During metabolic syndrome, considered a risk factor for steatosis development, an increase in ceramide and sphigosine-1-phosphate (S1P) have been reported. Likewise, other reports have highlighted that increased sphingomyelin and ceramide content is observed during steatosis and NASH. Ceramide also plays a role in liver fibrosis and cirrhosis, acting synergistically with S1P. Finally, during HCC, metabolic fluxes are redirected to reduce cellular ceramide levels whilst increasing S1P to support tumor growth.

Furowanin A Exhibits Antiproliferative and Pro-Apoptotic Activities by Targeting Sphingosine Kinase 1 in Osteosarcoma

Osteosarcoma (OS) is one of the most common malignant bone tumors among children and young adults. Furowanin A (Fur A), one of the active ingredients of Millettia pachycarpa Benth, has been found to exert pro-apoptotic activity in human leukemia cells. This study is designed to evaluate the efficacy of Fur A against OS. The effect of Fur A on cell viability was assessed by Cell Counting Kit-8 (CCK-8) assay. Western blotting and quantitative real-time PCR (qRT-PCR) were performed to determine the protein and mRNA level of sphingosine kinase 1 (SphK1), respectively. To validate the role of SphK1 in the pro-apoptotic activity of Fur A, overexpressing SphK1 vector and siRNA targeting SphK1 were utilized to transfect OS cells. Moreover, an OS xenograft murine model was used to analyze the therapeutic efficacy of Fur A in vivo. Fur A treatment led to a dose-dependent decrease in the number of viable cells. It also exhibited antiproliferative activity and significantly promoted apoptotic cell death in OS cell lines. Our results showed that the anticancer activity of Fur A was associated with downregulation of SphK1 and inactivation of its downstream signaling. The mediatory role of SphK1 was validated when the pro-apoptotic activity of Fur A was significantly blocked by SphK1 overexpression, while SphK1 knockdown sensitized the OS cells to Fur A. We concluded that Fur A can exhibit anti-growth and pro-apoptotic activities in vitro and in vivo in OS by downregulating SphK1. Our study highlights the possibility of utilizing Fur A as a chemotherapeutic agent in the treatment of OS. Anat Rec, 302:1941-1949, 2019. © 2019 American Association for Anatomy.

Cancer-induced inflammation and inflammation-induced cancer in colon: a role for S1P lyase

A role of sphingolipids for inflammatory bowel disease and cancer is evident. However, the relative and separate contribution of sphingolipid deterioration in inflammation versus carcinogenesis for the pathophysiology of colitis-associated colon cancer (CAC) was unknown and therefore examined in this study. We performed isogenic bone marrow transplantation of inducible sphingosine-1-phosphate (S1P) lyase knockout mice to specifically modulate sphingolipids and associated genes and proteins in a compartment-specific way in a DSS/AOM mediated CAC model. 3D organoid cultures were used in vitro. S1P lyase (SGPL1) knockout in either immune cells or tissue, caused local sphingolipid accumulation leading to a dichotomic development of CAC: Immune cell SGPL1 knockout (I-SGPL^-/-) augmented massive immune cell infiltration initiating colitis with lesions and calprotectin increase. Pathological crypt remodeling plus extracellular S1P-signaling caused delayed tumor formation characterized by S1P receptor 1, STAT3 mRNA increase, as well as programmed cell death ligand 1 expression, accompanied by a putatively counter regulatory STAT1^S727 phosphorylation. In contrast, tissue SGPL1 knockout (T-SGPL^-/-) provoked immediate occurrence of epithelial-driven tumors with upregulated sphingosine kinase 1, S1P receptor 2 and epidermal growth factor receptor. Here, progressing carcinogenesis was accompanied by an IL-12 to IL-23 shift with a consecutive development of a T_h2/GATA3-driven, tumor-favoring microenvironment. Moreover, the knockout models showed distinct lymphopenia and neutrophilia, different from the full SGPL1 knockout. This study shows that depending on the initiating cellular S1P source, the pathophysiology of inflammation-induced cancer versus cancer-induced inflammation develops through separate, discernible molecular steps.

Soyasapogenol B exhibits anti-growth and anti-metastatic activities in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most common type of human malignancies of the urological system. Soyasapogenol B (Soy B), an ingredient of soybean, has been found to exert anti-proliferative activities in vitro in human breast cancer cells. Our current study aimed to evaluate the effectiveness of Soy B against ccRCC. The effect of Soy B on cell viability was assessed by Cell Counting Kit-8 (CCK-8) assay. The effect of Soy B on cell proliferation was determined by colony formation assay. Apoptotic percentage was determined by flow cytometry following annexin V-FITC/propidium iodide (PI) double staining. JC-1 staining was performed to examine the change in mitochondrial membrane potential. Western blotting was used to determine the level of relevant proteins. Isobaric tags for relative and absolute quantification (iTRAQ) was then performed to identify the potential targets of Soy B. Quantitative real-time PCR (qRT-PCR) was performed to determine the mRNA level of sphingosine kinase 1 (SphK1). The SphK1 expression in ccRCC tissue from patients was examined by immunohistochemistry (IHC) assay. To validate the role of SphK1 involved in the pro-apoptotic activities of Soy B, overexpressed SphK1 vectors and shRNA targeting of SphK1 were utilized to transfected ccRCC cells. Moreover, a ccRCC xenograft murine model was used to analyze the therapeutic efficacy of Soy B in vivo. Soy B incubation led to a decrease in the number of viable cells in ccRCC cell lines and primary ccRCC cells. Soy B also suppressed the proliferation of two model ccRCC cell lines. Soy B promoted apoptotic cell death in a caspase-dependent manner. Moreover, our results showed that both extrinsic and intrinsic apoptotic signaling pathways were involved in Soy B-induced apoptosis. ITRAQ analysis identified SphK1 as most profoundly altered after the treatment of Soy B in ACHN cells. The mediatory role of SphK1 was validated when the pro-apoptotic activity of Soy B was significantly blocked by SphK1 overexpression, while SphK1 knockdown sensitized the ccRCC cells to Soy B. Moreover, in vivo studies also showed that Soy B could exhibit anti-cancer activities against ccRCC. Soy B triggers apoptotic cell death in vitro and in vivo in ccRCC by down-regulating SphK1. Our results highlight the possibility of using Soy B as a chemotherapeutic agent in the prevention and treatment of ccRCC.

Pro-Inflammatory Stimuli Influence Expression of Intercellular Adhesion Molecule 1 in Human Anulus Fibrosus Cells through FAK/ERK/GSK3 and PKCδ Signaling Pathways

OBJECTIVE

Intervertebral disc (IVD) degeneration and disc herniation are major causes of lower back pain, which involve the presence of inflammatory mediators and tissue invasion by immune cells. Intercellular adhesion molecule 1 (ICAM1, also termed CD54) is an adhesion molecule that mediates cell-cell interactions, particularly between immune cells and target tissue. The aim of this study was to examine the intracellular signaling pathways involved in inflammatory stimuli-induced ICAM1 expression in human anulus fibrosus (AF) cells.

METHODS

Quantitative reverse transcription-polymerase chain reaction (qPCR), western blotting, and flow cytometry were performed to dissect the roles of different signaling pathways in inflammatory stimuli-mediated ICAM1 expression.

RESULTS

Using qPCR and western blot analyses, a significant increase in ICAM1 expression was observed in AF cells after stimulation of lipopolysaccharide (LPS) plus interferon-gamma (IFNγ) in a time-dependent manner. Flow cytometry revealed ICAM1 upregulation on the surface of AF cells. Importantly, LPS plus IFNγ treatment also significantly promoted Chemokine ligand (CCL)2 expression, but not CCL3. The enhanced ICAM1 expression was abolished after incubation with antibody against CCL2. In AF cells, treatment with LPS plus IFNγ activated the FAK/ERK/GSK3 signaling pathways, promoted a time-dependent increase in PKCδ phosphorylation, and promoted PKCδ translocation to the nucleus. Treatment with the pharmacological PKCδ inhibitor; rottlerin, effectively blocked the enhanced productions of ICAM1 and CCL2.

CONCLUSIONS

Inflammatory stimuli in AF cells are part of a specific pathophysiology in IVD degeneration and disc herniation that modulates CCL2/ICAM1 activation through the FAK/ERK/GSK3 and PKCδ signaling pathways in AF cells.

Sphingosine kinase 1 promotes the metastasis of colorectal cancer by inducing the epithelial‑mesenchymal transition mediated by the FAK/AKT/MMPs axis

It was demonstrated that Sphingosine kinase 1 (SphK1) promotes tumor progression and confers the malignancy phenotype of colorectal cancer by activating the focal adhesion kinase (FAK) pathway. However, further clarification is required to determine if SphK1 promotes the metastasis of colorectal cancer by inducing epithelial‑mesenchymal transition (EMT), and its mechanisms have not been fully elucidated. Immunohistochemistry staining was used to detect protein expression in normal colonic mucosa tissues and colorectal cancer tissues. Cells were transfected to overexpress SphK1, downregulate SphK1 or downregulate FAK. An MTT assay was used to detect the drug toxicity to cells. Transwell and wound healing assays were used to detect cell migration ability. Reverse transcription‑polymerase chain reaction and western blot analysis were used to detect the expression of mRNA and protein, respectively. Scanning electron microscopy was used to observe the microvilli and pseudopodia of the cells. The analysis of protein expression in 114 human colorectal cancer tissues demonstrated that the expressions of SphK1, FAK, phosphorylated (p)‑FAK, E‑cadherin and vimentin were associated with the metastasis of colorectal cancer. Furthermore, the patients with colorectal cancer with SphK1‑positive cancer demonstrated poorer prognosis compared with SphK1‑negative cancer. FAK knockdown and SphK1 knockdown of human colon cancer RKO cells inhibited the EMT and migrational potency, along with the expression of p‑FAK, p‑protein kinase B (AKT) and matrix metalloproteinase (MMP)2/9. In contrast, SphK1 overexpression promoted EMT, migrational potency, and the expression of p‑FAK, p‑AKT and MMP2/9 in HT29 cells. Additionally, the EMT and migrational potency of SphK1‑overexpressing HT29 cells was suppressed by a FAK inhibitor, and the expression of p‑FAK, p‑AKT and MMP2/9 was suppressed by blocking the FAK pathway. In conclusion, SphK1 promoted the migration and metastasis of colon cancer by inducing EMT mediated by the FAK/AKT/MMPs axis.

Generation of sphingosine-1-phosphate is enhanced in biliary tract cancer patients and is associated with lymphatic metastasis

Lymphatic metastasis is known to contribute to worse prognosis of biliary tract cancer (BTC). Recently, sphingosine-1-phosphate (S1P), a bioactive lipid mediator generated by sphingosine kinase 1 (SPHK1), has been shown to play an important role in lymphangiogenesis and lymph node metastasis in several types of cancer. However, the role of the lipid mediator in BTC has never been examined. Here we found that S1P is elevated in BTC with the activation of ceramide-synthetic pathways, suggesting that BTC utilizes SPHK1 to promote lymphatic metastasis. We found that S1P, sphingosine and ceramide precursors such as monohexosyl-ceramide and sphingomyelin, but not ceramide, were significantly increased in BTC compared to normal biliary tract tissue using LC-ESI-MS/MS. Utilizing The Cancer Genome Atlas cohort, we demonstrated that S1P in BTC is generated via de novo pathway and exported via ABCC1. Further, we found that SPHK1 expression positively correlated with factors related to lymphatic metastasis in BTC. Finally, immunohistochemical examination revealed that gallbladder cancer with lymph node metastasis had significantly higher expression of phospho-SPHK1 than that without. Taken together, our data suggest that S1P generated in BTC contributes to lymphatic metastasis.

Hispidulin inhibits hepatocellular carcinoma growth and metastasis through AMPK and ERK signaling mediated activation of PPARγ

Hispidulin, a phenolic flavonoid, exerts potent cytotoxicity towards a variety of human cancers. However, the effects of hispidulin on hepatocellular carcinoma (HCC) and underlying molecular mechanisms of its action remain elusive. The present study investigated the effect of hispidulin on HCC in experimental models, including tumor cell lines and mouse tumor xenograft. Results demonstrated that hispidulin was cytotoxic and anti-proliferative to HCC cell lines (SMMC7721 and Bel7402). Hispidulin activated caspase-3 and triggered apoptosis in HCC cells. Moreover, hispidulin inhibited cell migration and invasion by inhibiting the expression of matrix metalloproteinases (MMP-2, MMP-9) and by inducing tissue inhibitor of metalloproteinase-3 (TIMP-3) expression. Hispidulin activated peroxisome proliferator-activated receptor γ (PPARγ) signaling which mainly contributed to its cytotoxicity in HCC cells. Remarkably, GW9662 (a PPARγ inhibitor) or PPARγ targeting siRNA significantly abrogated the anti-proliferative, pro-apoptotic, and anti-metastatic effects of hispidulin in HCC cells. Furthermore, hispidulin induced activation of PPARγ which was associated with increased phosphorylation of AMPK, ERK, JNK in HCC cells. Compound C (an AMPK inhibitor) or PD98059 (a MEK inhibitor) partly reversed the effects of hispidulin on PPARγ signaling in HCC cells. In contrast, no significant changes in PPARγ signaling were observed in HCC cells pretreated with SP600125 (a JNK inhibitor), while SP6000125 significantly inhibited the anti-cancer effects of hispidulin in HCC cells. Hispidulin administration effectively suppressed Bel7402 xenograft tumor growth and lung metastasis in vivo. Our findings indicate that PPARγ activation by hispidulin effectively suppressed HCC cell growth and metastasis both in vitro and in vivo.

SPHK1 (sphingosine kinase 1) induces epithelial-mesenchymal transition by promoting the autophagy-linked lysosomal degradation of CDH1/E-cadherin in hepatoma cells

SPHK1 (sphingosine kinase 1), a regulator of sphingolipid metabolites, plays a causal role in the development of hepatocellular carcinoma (HCC) through augmenting HCC invasion and metastasis. However, the mechanism by which SPHK1 signaling promotes invasion and metastasis in HCC remains to be clarified. Here, we reported that SPHK1 induced the epithelial-mesenchymal transition (EMT) by accelerating CDH1/E-cadherin lysosomal degradation and facilitating the invasion and metastasis of HepG2 cells. Initially, we found that SPHK1 promoted cell migration and invasion and induced the EMT process through decreasing the expression of CDH1, which is an epithelial marker. Furthermore, SPHK1 accelerated the lysosomal degradation of CDH1 to induce EMT, which depended on TRAF2 (TNF receptor associated factor 2)-mediated macroautophagy/autophagy activation. In addition, the inhibition of autophagy recovered CDH1 expression and reduced cell migration and invasion through delaying the degradation of CDH1 in SPHK1-overexpressing cells. Moreover, the overexpression of SPHK1 produced intracellular sphingosine-1-phosphate (S1P). In response to S1P stimulation, TRAF2 bound to BECN1/Beclin 1 and catalyzed the lysine 63-linked ubiquitination of BECN1 for triggering autophagy. The deletion of the RING domain of TRAF2 inhibited autophagy and the interaction of BECN1 and TRAF2. Our findings define a novel mechanism responsible for the regulation of the EMT via SPHK1-TRAF2-BECN1-CDH1 signal cascades in HCC cells. Our work indicates that the blockage of SPHK1 activity to attenuate autophagy may be a promising strategy for the prevention and treatment of HCC.

Activation of PPARγ mediates icaritin-induced cell cycle arrest and apoptosis in glioblastoma multiforme

BACKGROUND

Glioblastoma multiforme (GBM) is the most prevalent primary malignancy of the brain. This study was designed to investigate whether icaritin exerts anti-neoplastic activity against GBM in vitro.

MATERIALS AND METHODS

Cell Counting Kit-8 (CCK-8) assay was utilized to examine the viability of GBM cells. The apoptotic cell population was measured by flow cytometry analysis. Cell cycle distribution was detected by flow cytometry as well. Western blot analysis was performed to examine the level of biomarker proteins in GBM cells. Levels of PPARγ mRNA and protein were detected by qPCR and western blot analysis, respectively. To examine the role of PPARγ in the anti-neoplastic activity of icaritin, PPARγ antagonist GW9662 or PPARγ siRNA was used. The activity of PPARγ was determined by DNA binding and luciferase assays.

RESULTS

Our findings revealed that icaritin markedly suppresses cell growth in a dose-dependent and time-dependent fashion. The cell population at the G0/G1 phase of the cell cycle was significantly increased following icaritin treatment. Meanwhile, icaritin promoted apoptotic cell death in T98G and U87MG cells. Further investigation showed upregulation of PPARγ played a key role in the anti-neoplastic activities of icaritin. Moreover, our result demonstrated activation of AMPK signaling by icaritin mediated the modulatory effect of icaritin on PPARγ.

CONCLUSION

Our results suggest the PPARγ may mediate anti-neoplastic activities against GBM.

Hispidulin mediates apoptosis in human renal cell carcinoma by inducing ceramide accumulation

Hispidulin, a polyphenolic flavonoid extracted from the traditional Chinese medicinal plant S involucrata, exhibits anti-tumor effects in a wide array of human cancer cells, mainly through growth inhibition, apoptosis induction and cell cycle arrest. However, its precise anticancer mechanisms remain unclear. In this study, we investigated the molecular mechanisms that contribute to hispidulin-induced apoptosis of human clear-cell renal cell carcinoma (ccRCC) lines Caki-2 and ACHN. Hispidulin (10, 20 μmol/L) decreased the viability of ccRCC cells in dose- and time-dependent manners without affecting that of normal tubular epithelial cells. Moreover, hispidulin treatment dose-dependently increased the levels of cleaved caspase-8 and caspase-9, but the inhibitors of caspase-8 and caspase-9 only partly abrogated hispidulin-induced apoptosis, suggesting that hispidulin triggered apoptosis via both extrinsic and intrinsic pathways. Moreover, hispidulin treatment significantly inhibited the activity of sphingosine kinase 1 (SphK1) and consequently promoted ceramide accumulation, thus leading to apoptosis of the cancer cells, whereas pretreatment with K6PC-5, an activator of SphK1, or overexpression of SphK1 significantly attenuated the anti-proliferative and pro-apoptotic effects of hispidulin. In addition, hispidulin treatment dose-dependently activated ROS/JNK signaling and led to cell apoptosis. We further demonstrated in Caki-2 xenograft nude mice that injection of hispidulin (20, 40 mg·kg^-1·d^-1, ip) dose-dependently suppressed tumor growth accompanied by decreased SphK1 activity and increased ceramide accumulation in tumor tissues. Our findings reveal a new explanation for the anti-tumor mechanisms of hispidulin, and suggest that SphK1 and ceramide may serve as potential therapeutic targets for the treatment of ccRCC.

Sphingosine Kinase 1 and Sphingosine-1-Phosphate Signaling in Colorectal Cancer

Sphingosine kinase 1 (Sphk1) is a highly conserved lipid kinase that phosphorylates sphingosine to form sphingosine-1-phosphate (S1P). Growing studies have demonstrated that Sphk1 is overexpressed in various types of solid cancers and can be induced by growth factors, cytokines, and carcinogens, leading to the increase of S1P production. Subsequently, the increased Sphk1/S1P facilitates cancer cell proliferation, mobility, angiogenesis, invasion, and metastasis. Therefore, Sphk1/S1P signaling plays oncogenic roles. This review summarizes the features of Sphk1/S1P signaling and their functions in colorectal cancer cell growth, tumorigenesis, and metastasis, as well as the possible underlying mechanisms.

Overexpression of sphingosine kinase 1 is predictive of poor prognosis in human breast cancer

Sphingosine kinase 1 (SPHK1) is a bioactive lipid mediator that has been identified as a biomarker in various cancers and is considered to play an important role in tumor progression. In the present study, the expression level of SPHK1 was examined in breast cancer clinical specimens, and its association with patient survival was investigated to clarify the clinical significance of SPHK1 in breast cancer. SPHK1 mRNA expression was increased in breast cancer tissues compared with that in matched adjacent breast tissues in 19 of 32 paired tissue specimens (59.4%). Immunohistochemical analysis of 122 breast cancer cases revealed that the expression levels of SPHK1 were upregulated in 64 tumor tissues (52.5%), and increased expression levels of the protein were significantly associated with the presence of lymph node metastasis (P=0.0016), number of positive lymph nodes (P=0.0268) and presence of distant metastasis (P=0.0097). Increased SPHK1 protein expression was also associated with human epidermal growth factor receptor 2 status (P=0.0100), initial symptoms (P=0.0025) and tumor location (P=0.0457). Patients with increased SPHK1 protein expression had shorter overall survival and disease-free survival times compared with patients with lower SPHK1. Univariate and multivariate analyses indicated that high SPHK1 expression may be a poor prognostic factor. These results indicated that SPHK1 may perform an important role in breast cancer and may be a predictive factor in patients with breast cancer.

SphK1 modulates cell migration and EMT-related marker expression by regulating the expression of p-FAK in colorectal cancer cells

Sphingosine kinase 1 (SphK1) plays an important role in colorectal carcinoma metastasis. However, whether SphK1 modulates epithelial-mesenchymal transition (EMT)-related marker expression and the underlying mechanisms remain unclear. In this study, in order to clarify this issue, we used various colorectal cancer (CRC) cell lines, Caco2, HT29, RKO and HCT116. Each of the cell lines was divided into 3 groups as follows: the control group, SKI-Ⅱ (SphK1 inhibitor) group and PF-562271 [focal adhesion kinase (FAK) inhibitor] group. The migratory ability of the cells was examined by Transwell chamber assay. The mRNA and protein expression levels of SphK1, FAK (p-FAK), Slug, vimentin, N-cadherin and E-cadherin were detected by PCR and western blot analysis, respectively. The results revealed that the suppression of SphK1 reduced the cell migratory ability, and decreased the expression of Slug, vimentin and N-cadherin; however, the expression of E-cadherin was increased. Moreover, the inhibition of SphK1 reduced the expression of p-FAK. The inhibition of FAK (p-FAK) also decreased the cell migratory ability, and decreased the expression of Slug, vimentin and N-cadherin, whereas the expression of E-cadherin was increased. Thus, our data suggest that SphK1 modulates the expression of EMT-related markers and cell migration by regulating the expression of p-FAK in CRC cells. Thus, SphK1 may play a functional role in mediating the EMT process in CRC.

Autophagy Protects from Raddeanin A-Induced Apoptosis in SGC-7901 Human Gastric Cancer Cells

Raddeanin A (RA) is an extractive from Anemone raddeana Regel, a traditional Chinese medicine. The aim of this study is to assess the efficacy of RA against human gastric cancer (GC) cells (SGC-7901) and explore its mechanism. MTT assay showed that RA inhibition of proliferation of SGC-7901 cells increased in a dose-dependent manner. Flow cytometry analysis and Hoechst 33258 staining showed that RA induced apoptosis on SGC-7901 cells. Meanwhile, it induced autophagy. Western blotting analysis showed that the RA induces apoptosis and autophagy by activating p38 MAPK pathway and inhibiting mTOR pathway. Further studies showed that autophagy inhibition could protect from RA-induced apoptosis in SGC-7901 cells. In conclusion, RA can induce SGC-7901 cell apoptosis and autophagy by activating p38 MAPK pathway. And autophagy can protect SGC-7901 cells from apoptosis induced by RA.

DNA damage response and sphingolipid signaling in liver diseases

Patients with unresectable hepatocellular carcinoma (HCC) cannot generally be cured by systemic chemotherapy or radiotherapy due to their poor response to conventional therapeutic agents. The development of novel and efficient targeted therapies to increase their treatment options depends on the elucidation of the molecular mechanisms that underlie the pathogenesis of HCC. The DNA damage response (DDR) is a network of cell-signaling events that are triggered by DNA damage. Its dysregulation is thought to be one of the key mechanisms underlying the generation of HCC. Sphingosine-1-phosphate (S1P), a lipid mediator, has emerged as an important signaling molecule that has been found to be involved in many cellular functions. In the liver, the alteration of S1P signaling potentially affects the DDR pathways. In this review, we explore the role of the DDR in hepatocarcinogenesis of various etiologies, including hepatitis B and C infection and non-alcoholic steatohepatitis. Furthermore, we discuss the metabolism and functions of S1P that may affect the hepatic DDR. The elucidation of the pathogenic role of S1P may create new avenues of research into therapeutic strategies for patients with HCC.

Metabolic Regulation of Apoptosis in Cancer

Apoptosis is a cellular suicide program that plays a critical role in development and human diseases, including cancer. Cancer cells evade apoptosis, thereby enabling excessive proliferation, survival under hypoxic conditions, and acquired resistance to therapeutic agents. Among various mechanisms that contribute to the evasion of apoptosis in cancer, metabolism is emerging as one of the key factors. Cellular metabolites can regulate functions of pro- and antiapoptotic proteins. In turn, p53, a regulator of apoptosis, also controls metabolism by limiting glycolysis and facilitating mitochondrial respiration. Consequently, with dysregulated metabolism and p53 inactivation, cancer cells are well-equipped to disable the apoptotic machinery. In this article, we review how cellular apoptosis is regulated and how metabolism can influence the signaling pathways leading to apoptosis, especially focusing on how glucose and lipid metabolism are altered in cancer cells and how these alterations can impact the apoptotic pathways.

Interstitial Fluid Sphingosine-1-Phosphate in Murine Mammary Gland and Cancer and Human Breast Tissue and Cancer Determined by Novel Methods

The tumor microenvironment is a determining factor for cancer biology and progression. Sphingosine-1-phosphate (S1P), produced by sphingosine kinases (SphKs), is a bioactive lipid mediator that regulates processes important for cancer progression. Despite its critical roles, the levels of S1P in interstitial fluid (IF), an important component of the tumor microenvironment, have never previously been measured due to a lack of efficient methods for collecting and quantifying IF. The purpose of this study is to clarify the levels of S1P in the IF from murine mammary glands and its tumors utilizing our novel methods. We developed an improved centrifugation method to collect IF. Sphingolipids in IF, blood, and tissue samples were measured by mass spectrometry. In mice with a deletion of SphK1, but not SphK2, levels of S1P in IF from the mammary glands were greatly attenuated. Levels of S1P in IF from mammary tumors were reduced when tumor growth was suppressed by oral administration of FTY720/fingolimod. Importantly, sphingosine, dihydro-sphingosine, and S1P levels, but not dihydro-S1P, were significantly higher in human breast tumor tissue IF than in the normal breast tissue IF. To our knowledge, this is the first reported S1P IF measurement in murine normal mammary glands and mammary tumors, as well as in human patients with breast cancer. S1P tumor IF measurement illuminates new aspects of the role of S1P in the tumor microenvironment.

High levels of sphingolipids in human breast cancer

BACKGROUND

Sphingolipids, including sphingosine-1-phosphate (S1P) and ceramide, have emerged as key regulatory molecules that control various aspects of cell growth and proliferation in cancer. Although important roles of sphingolipids in breast cancer progression have been reported in experimental models, their roles in human patients have yet to be determined. The aims of this study were to determine the levels of sphingolipids including S1P, ceramides, and other sphingolipids, in breast cancer and normal breast tissue and to compare the difference in levels of each sphingolipid between the two tissues.

MATERIALS AND METHODS

Tumor and noncancerous breast tissue were obtained from 12 patients with breast cancer. Sphingolipids including S1P, ceramides, and their metabolites of sphingosine, sphingomyelin, and monohexosylceramide were measured by liquid chromatography-electrospray ionization-tandem mass spectrometry.

RESULTS

The levels of S1P, ceramides, and other sphingolipids in the tumor were significantly higher than those in normal breast tissue. There was a relatively strong correlation in the levels of S1P between the tumor and those of normal breast tissue from the same person. On the other hand, there was no correlation in the levels of most of the ceramide species between the tumor and those of normal breast tissue from the same person.

CONCLUSIONS

To our knowledge, this is the first study to reveal that levels of sphingolipids in cancer tissue are generally higher than those of normal breast tissue in patients with breast cancer. The correlation of S1P levels in these tissues implicates the role of S1P in interaction between cancer and the tumor microenvironment.

Significance of TNF-α and the Adhesion Molecules: L-Selectin and VCAM-1 in Papillary Thyroid Carcinoma

Circulating levels of TNF-α and the adhesion molecules L-Selectin and VCAM-1 as well as their expression in the primary tumors of patients with benign thyroid diseases and papillary thyroid carcinoma (PTC) have been determined in this study. The serum levels of TNF-α, L-Selectin, and VCAM-1 were significantly higher in patients with both benign thyroid diseases and PTC as compared to the healthy individuals. However, the levels of only TNF-α and L-Selectin, and not VCAM-1, were significantly higher in patients with PTC in comparison to those observed in patients with benign thyroid diseases. Further the expression of TNF-α and L-Selectin was also significantly higher in the primary tumors of PTC patients, relative to the benign thyroid diseases. The expression of L-Selectin and VCAM-1 significantly correlated with aggressive tumor behavior. In PTC patients, the circulating TNF-α levels significantly positively correlated with the levels of L-Selectin, while TNF-α immunoreactivity was significantly associated with VCAM-1 expression. Serum TNF-α was found to be a significant prognosticator for OS in PTC patients. Overall the results signify that the interaction between TNF-α and the adhesion molecules may have a role in thyroid carcinogenesis and understanding this complexity may offer potential therapeutic targets for better management of thyroid cancer.

Hepatitis B virus X protein promotes human hepatoma cell growth via upregulation of transcription factor AP2α and sphingosine kinase 1

AIM

Sphingosine kinase 1 (SPHK1) is involved in various cellular functions, including cell growth, migration, apoptosis, cytoskeleton architecture and calcium homoeostasis, etc. As an oncogenic kinase, SPHK1 is associated with the development and progression of cancers. The aim of this study was to investigate whether SPHK1 was involved in hepatocarcinogenesis induced by the hepatitis B virus X protein (HBx).

METHODS

The expression of SPHK1 in hepatocellular carcinoma (HCC) tissue and hepatoma cells were measured using qRT-PCR and Western blot analysis. HBx expression levels in hepatoma cells were modulated by transiently transfected with HBx or psi-HBx plasmids. The SPHK1 promoter activity was measured using luciferase reporter gene assay, and the interaction of the transcription factor AP2α with the SPHK1 promoter was studied with chromatin immunoprecipitation assay. The growth of hepatoma cells was evaluated in vitro using MTT and colony formation assays, and in a tumor xenograft model.

RESULTS

A positive correlation was found between the mRNA levels of SPHK1 and HBx in 38 clinical HCC samples (r=+0.727, P<0.01). Moreover, the expression of SPHK1 was markedly increased in the liver cancer tissue of HBx-transgenic mice. Overexpressing HBx in normal liver cells LO2 and hepatoma cells HepG2 dose-dependently increased the expression of SPHK1, whereas silencing HBx in HBx-expressing hepatoma cells HepG2-X and HepG2.2.15 suppressed SPHK1 expression. Furthermore, overexpressing HBx in HepG2 cells dose-dependently increased the SPHK1 promoter activity, whereas silencing HBx in HepG2-X cells suppressed this activity. In HepG2-X cells, AP2α was found to directly interact with the SPHK1 promoter, and silencing AP2α suppressed the SPHK1 promoter activity and SPHK1 expression. Silencing HBx in HepG2-X cells abolished the HBx-enhanced proliferation and colony formation in vitro, and tumor growth in vivo.

CONCLUSION

HBx upregulates SPHK1 through the transcription factor AP2α, which promotes the growth of human hepatoma cells.

Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: focus on the cancer hallmark of tumor angiogenesis

One of the important 'hallmarks' of cancer is angiogenesis, which is the process of formation of new blood vessels that are necessary for tumor expansion, invasion and metastasis. Under normal physiological conditions, angiogenesis is well balanced and controlled by endogenous proangiogenic factors and antiangiogenic factors. However, factors produced by cancer cells, cancer stem cells and other cell types in the tumor stroma can disrupt the balance so that the tumor microenvironment favors tumor angiogenesis. These factors include vascular endothelial growth factor, endothelial tissue factor and other membrane bound receptors that mediate multiple intracellular signaling pathways that contribute to tumor angiogenesis. Though environmental exposures to certain chemicals have been found to initiate and promote tumor development, the role of these exposures (particularly to low doses of multiple substances), is largely unknown in relation to tumor angiogenesis. This review summarizes the evidence of the role of environmental chemical bioactivity and exposure in tumor angiogenesis and carcinogenesis. We identify a number of ubiquitous (prototypical) chemicals with disruptive potential that may warrant further investigation given their selectivity for high-throughput screening assay targets associated with proangiogenic pathways. We also consider the cross-hallmark relationships of a number of important angiogenic pathway targets with other cancer hallmarks and we make recommendations for future research. Understanding of the role of low-dose exposure of chemicals with disruptive potential could help us refine our approach to cancer risk assessment, and may ultimately aid in preventing cancer by reducing or eliminating exposures to synergistic mixtures of chemicals with carcinogenic potential.

A novel role of sphingosine kinase-1 in the invasion and angiogenesis of VHL mutant clear cell renal cell carcinoma

Sphingosine kinase 1 (SK1), the enzyme responsible for sphingosine 1-phosphate (S1P) production, is overexpressed in many human solid tumors. However, its role in clear cell renal cell carcinoma (ccRCC) has not been described previously. ccRCC cases are usually associated with mutations in von Hippel-Lindau (VHL) and subsequent normoxic stabilization of hypoxia-inducible factor (HIF). We previously showed that HIF-2α up-regulates SK1 expression during hypoxia in glioma cells. Therefore, we hypothesized that the stabilized HIF in ccRCC cells will be associated with increased SK1 expression. Here, we demonstrate that SK1 is overexpressed in 786-0 renal carcinoma cells lacking functional VHL, with concomitant high S1P levels that appear to be HIF-2α mediated. Moreover, examining the TCGA RNA seq database shows that SK1 expression was ∼2.7-fold higher in solid tumor tissue from ccRCC patients, and this was associated with less survival. Knockdown of SK1 in 786-0 ccRCC cells had no effect on cell proliferation. On the other hand, this knockdown resulted in an ∼3.5-fold decrease in invasion, less phosphorylation of focal adhesion kinase (FAK), and an ∼2-fold decrease in angiogenesis. Moreover, S1P treatment of SK1 knockdown cells resulted in phosphorylation of FAK and invasion, and this was mediated by S1P receptor 2. These results suggest that higher SK1 and S1P levels in VHL-defective ccRCC could induce invasion in an autocrine manner and angiogenesis in a paracrine manner. Accordingly, targeting SK1 could reduce both the invasion and angiogenesis of ccRCC and therefore improve the survival rate of patients.

Relationship between expression of NIBP and noncanonical NF-κB signaling: Clinical significance in colon carcinoma

AIM: To investigate the expression of NIK, IKKβ binding protein (NIBP), phosphorylated p100 (p-p100), p52, CD44, Vimentin and E-cadherin in colon carcinoma and to explore their clinical significance.

METHODS: Immunohistochemistry was used to detect the expression of NIBP, p-p100, p52, CD44, E-cadherin and Vimentin in 114 paraffin-embedded colon carcinoma tissues, 20 colon adenoma tissues and 50 normal colon mucosa tissues.

RESULTS: The positive expression of NIBP, p-p100, p52, CD44 and Vimentin in colon cancer tissues with metastasis was much higher than that in colon cancer tissues without metastasis, colon adenoma tissues and normal colon mucosa tissues, while the expression of E-cadherin showed a reverse trend (P < 0.05). The expression of NIBP, p-p100, p52, CD44, Vimentin and E-cadherin in colon cancer tissues was related with depth of invasion, TNM stage, lymph node metastasis and distant metastasis (P < 0.05). There were significant correlations between the expression of p-p100 and p52 or NIBP, and between the expression of CD44 and p52, E-cadherin, or Vimentin.

CONCLUSION: NIBP may regulate the epithelial-mesenchymal transition process by activating the noncanonical nuclear factor-κB (NF-κB) signal pathway and thus play an important role in the development, invasion and metastasis of colon cancer.

The sphingosine kinase 1/sphingosine-1-phosphate pathway in pulmonary arterial hypertension

RATIONALE

Sphingosine kinases (SphKs) 1 and 2 regulate the synthesis of the bioactive sphingolipid sphingosine-1-phosphate (S1P), an important lipid mediator that promotes cell proliferation, migration, and angiogenesis.

OBJECTIVES

We aimed to examine whether SphKs and their product, S1P, play a role in the development of pulmonary arterial hypertension (PAH).

METHODS

SphK1(-/-), SphK2(-/-), and S1P lyase heterozygous (Sgpl1(+/-)) mice, a pharmacologic SphK inhibitor (SKI2), and a S1P receptor 2 (S1PR2) antagonist (JTE013) were used in rodent models of hypoxia-mediated pulmonary hypertension (HPH). S1P levels in lung tissues from patients with PAH and pulmonary arteries (PAs) from rodent models of HPH were measured.

MEASUREMENTS AND MAIN RESULTS

mRNA and protein levels of SphK1, but not SphK2, were significantly increased in the lungs and isolated PA smooth muscle cells (PASMCs) from patients with PAH, and in lungs of experimental rodent models of HPH. S1P levels were increased in lungs of patients with PAH and PAs from rodent models of HPH. Unlike SphK2(-/-) mice, SphK1(-/-) mice were protected against HPH, whereas Sgpl1(+/-) mice were more susceptible to HPH. Pharmacologic SphK1 and S1PR2 inhibition prevented the development of HPH in rodent models of HPH. Overexpression of SphK1 and stimulation with S1P potentially via ligation of S1PR2 promoted PASMC proliferation in vitro, whereas SphK1 deficiency inhibited PASMC proliferation.

CONCLUSIONS

The SphK1/S1P axis is a novel pathway in PAH that promotes PASMC proliferation, a major contributor to pulmonary vascular remodeling. Our results suggest that this pathway is a potential therapeutic target in PAH.

STAT3 and sphingosine-1-phosphate in inflammation-associated colorectal cancer

Accumulated evidences have demonstrated that signal transducer and activator of transcription 3 (STAT3) is a critical link between inflammation and cancer. Multiple studies have indicated that persistent activation of STAT3 in epithelial/tumor cells in inflammation-associated colorectal cancer (CRC) is associated with sphingosine-1-phosphate (S1P) receptor signaling. In inflammatory response whereby interleukin (IL)-6 production is abundant, STAT3-mediated pathways were found to promote the activation of sphingosine kinases (SphK1 and SphK2) leading to the production of S1P. Reciprocally, S1P encourages the activation of STAT3 through a positive autocrine-loop signaling. The crosstalk between IL-6, STAT3 and sphingolipid regulated pathways may play an essential role in tumorigenesis and tumor progression in inflamed intestines. Therapeutics targeting both STAT3 and sphingolipid are therefore likely to contribute novel and more effective therapeutic strategies against inflammation-associated CRC.

Sphingosine-1-phosphate transporters as targets for cancer therapy

Sphingosine-1-phosphate (S1P) is a pleiotropic lipid mediator that regulates cell survival, migration, the recruitment of immune cells, angiogenesis, and lymphangiogenesis, all of which are involved in cancer progression. S1P is generated inside cancer cells by sphingosine kinases then exported outside of the cell into the tumor microenvironment where it binds to any of five G protein coupled receptors and proceeds to regulate a variety of functions. We have recently reported on the mechanisms underlying the "inside-out" signaling of S1P, its export through the plasma membrane, and its interaction with cell surface receptors. Membrane lipids, including S1P, do not spontaneously exchange through lipid bilayers since the polar head groups do not readily go through the hydrophobic interior of the plasma membrane. Instead, specific transporter proteins exist on the membrane to exchange these lipids. This review summarizes what is known regarding S1P transport through the cell membrane via ATP-binding cassette transporters and the spinster 2 transporter and discusses the roles for these transporters in cancer and in the tumor microenvironment. Based on our research and the emerging understanding of the role of S1P signaling in cancer and in the tumor microenvironment, S1P transporters and S1P signaling hold promise as new therapeutic targets for cancer drug development.

Telmisartan exerts anti-tumor effects by activating peroxisome proliferator-activated receptor-γ in human lung adenocarcinoma A549 cells

Telmisartan, a member of the angiotensin II type 1 receptor blockers, is usually used for cardiovascular diseases. Recent studies have showed that telmisartan has the property of PPARγ activation. Meanwhile, PPARγ is essential for tumor proliferation, invasion and metastasis. In this work we explore whether telmisartan could exert anti-tumor effects through PPARγ activation in A549 cells. MTT and trypan blue exclusion assays were included to determine the survival rates and cell viabilities. RT-PCR and western blotting were used to analyze the expression of ICAM-1, MMP-9 and PPARγ. DNA binding activity of PPARγ was evaluated by EMSA. Our data showed that the survival rates and cell viabilities of A549 cells were all reduced by telmisartan in a time- and concentration-dependent manner. Meanwhile, our results also demonstrated that telmisartan dose-dependently inhibited the expression of ICAM-1 and MMP-9. Moreover, the cytotoxic and anti-proliferative effects, ICAM-1 and MMP-9 inhibitive properties of telmisartan were totally blunted by the PPARγ antagonist GW9662. Our findings also showed that the expression of PPARγ was up-regulated by telmisartan in a dose dependent manner. And, the EMSA results also figured out that DNA binding activity of PPARγ was dose-dependently increased by telmisartan. Additionally, our data also revealed that telmisartan-induced PPARγ activation was abrogated by GW9662. Taken together, our results indicated that telmisartan inhibited the expression of ICAM-1 and MMP-9 in A549 cells, very likely through the up-regulation of PPARγ synthesis.