Single nucleotide polymorphism rs13042395 in the SLC52A3 gene as a biomarker for regional lymph node metastasis and relapse-free survival of esophageal squamous cell carcinoma patients

Brown-Vialetto-Van Laere syndrome patients with unusual phenotypes from Indian ethnicity: Functional analysis of clinical variants in SLC52A2 and SLC52A3 genes

BACKGROUND

BVVLS (Brown-Vialetto-Van Laere syndrome), a rare genetic condition characterized by progressive neuropathy, is caused by defects in SLC52A2 and SLC52A3 genes coding for hRFVT-2 and hRFVT-3.

METHODS

Five BVVLS cases were screened for disease-causing variants using exome sequencing and their functional contributions were evaluated by in silico analysis, riboflavin transport assay and confocal imaging.

RESULTS

Probands enrolled in this study were presented with unusual phenotypes like syndactyly, polydactyly, pedal edema and chronic osteomyelitis. Genetic testing disclosed heterozygous variants in all five cases including c.229G>A p.E77K, c.384G>A p.S128S, c.1245C>T p.G415G and c.843del p.L282Cfs*8 in SLC52A2 gene and c.833C>T p.T278M, c.907A>G p.I303V and c.62A>G p.N21S in SLC52A3 gene. Among them, p.L282Cfs*8 was diagnosed here for first-time, whereas p.E77K and p.S128S were reported previously with a variation at nucleotide position. Functional analysis of the variant p.E77K, p.S128S, p.T278M and p.I303V evidenced impairment in riboflavin transport, whereas p.G415G and p.L282Cfs*8 showed no significant changes. Despite of having reduction in riboflavin uptake, the presence of same polymorphic variant (p.T278M and p.I303V) in asymptomatic father suggests it as not likely associated with disease phenotypes. Meantime, membranous expression of hRFVT-2 variants p.S128S and p.E77K were abrogated and mostly internalized in cytoplasmic regions of transfected cells, whereas no change was observed with other variants than wild-type.

CONCLUSION

These results show for the first-time that BVVLS associated hRFVT-2 variants p.S128S and p.E77K affected riboflavin transport function due to abrogation in membranous localization and/or activity of the transporter. The polymorphic variants p.T278M and p.I303V of hRFVT-3 are unlikely to be implicated functionally in the pathogenesis of the disease.

Promotion of rs3746804 (p. L267P) polymorphism to intracellular SLC52A3a trafficking and riboflavin transportation in esophageal cancer cells

Riboflavin is an essential micronutrient for normal cellular growth and function. Lack of dietary riboflavin is associated with an increased risk for esophageal squamous cell carcinoma (ESCC). Previous studies have identified that the human riboflavin transporter SLC52A3a isoform (encoded by SLC52A3) plays a prominent role in esophageal cancer cell riboflavin transportation. Furthermore, SLC52A3 gene single nucleotide polymorphisms rs3746804 (T>C, L267P) and rs3746803 (C >T, T278M) are associated with ESCC risk. However, whether SLC52A3a (p.L267P) and (p.T278M) act in riboflavin transportation in esophageal cancer cell remains inconclusive. Here, we constructed the full-length SLC52A3a protein fused to green fluorescent protein (GFP-SLC52A3a-WT and mutants L267P, T278M, and L267P/T278M). It was confirmed by immunofluorescence-based confocal microscopy that SLC52A3a-WT, L267P, T278M, and L267P/T278M expressed in cell membrane, as well as in a variety of intracellular punctate structures. The live cell confocal imaging showed that SLC52A3a-L267P and L267P/T278M increased the intracellular trafficking of SLC52A3a in ESCC cells. Fluorescence recovery after photobleaching of GFP-tagged SLC52A3a meant that intracellular trafficking of SLC52A3a-L267P and L267P/T278M was rapid dynamics process, leading to its stronger ability to transport riboflavin. Taken together, the above results indicated that the rs3746804 (p.L267P) polymorphism promoted intracellular trafficking of SLC52A3a and riboflavin transportation in ESCC cells.

Inhibiting autophagy enhances sulforaphane-induced apoptosis via targeting NRF2 in esophageal squamous cell carcinoma

Sulforaphane (SFN), a natural anti-tumor compound from cruciferous vegetables, has been reported to induce protective autophagy to cancer cells, which might impair the anti-tumor efficiency of SFN. However, the accurate function and mechanism of SFN inducing autophagy in cancers are still obscure, especially in esophageal squamous cell carcinoma (ESCC), one of malignancies with high incidence in North China. Here, we mainly explored the potential function of autophagy upon SFN treatment in ESCC and molecular mechanism. We demonstrated that SFN could inhibit cell proliferation and induce apoptosis by activating caspase pathway. Moreover, we found activation of NRF2 pathway by SFN was responsible for the induction of autophagy and also a disadvantage element to the anti-tumor effects of SFN on ESCC, indicating that SFN might induce protective autophagy in ESCC. We, therefore, investigated effects of autophagy inhibition on sensitivity of ESCC cells to SFN and found that chloroquine (CQ) could neutralize the activation of SFN on NRF2 and enhance the activation of SFN on caspase pathway, thus improved the anti-tumor efficiency of SFN on ESCC in vitro and in vivo. Our study provides a preclinical rationale for development of SFN and its analogs to the future treatment of ESCC.

Functional variation of SLC52A3 rs13042395 predicts survival of Chinese gastric cancer patients

The solute carrier family 52 member 3 (SLC52A3) gene encodes riboflavin transporter protein which is essential to maintain mitochondrial function in cells. In our research, we found that SLC52A3 rs13042395 C > T variation was significantly associated with poor survival in a 926 Chinese gastric cancer (GCa) patients cohort (CC/CT genotype versus TT genotype, HR = 0.57, 95%CI (0.40-0.82), log-rank P = 0.015). The SLC52A3 rs13042395 C > T change led to its increased mRNA expression according to expression quantitative trait loci analysis (P = 0.0029). In vitro, it was revealed that rs13042395 C allele had higher binding affinity to inhibitory transcription factor Meis homeobox 1 (MEIS1) compared with T allele, knock-down of MEIS1 could up-regulate SLC52A3, and overexpression of SLC52A3 contributed to the increased ability of proliferation, colony formation, migration and invasion in GCa cells. Subsequently, the bioinformatics analysis combined with experiments in vitro suggested that Gap junction protein alpha 1 (GJA1) was the downstream effector of SLC52A3, SLC52A3 may promote the GCa cells aggressiveness by down-regulating the GJA1 expression. Overall, SLC52A3 genetic variant rs13042395 C > T change was associated with poorer survival in Chinese GCa patients and increased SLC52A3 expression by interaction with MEIS1. SLC52A3 promoted the GCa cells aggressiveness by down-regulating the GJA1 expression.

Genome-wide Discovery of a Novel Gene-expression Signature for the Identification of Lymph Node Metastasis in Esophageal Squamous Cell Carcinoma

OBJECTIVE

This study aimed to develop a gene-expression signature for identification of lymph node (LN) metastasis in esophageal squamous cell carcinoma (ESCC) patients.

SUMMARY OF BACKGROUND DATA

LN metastasis is recognized as the most important independent risk factor for therapeutic decision-making of ESCC patients.

METHODS

A bioinformatic approach was used to analyze RNA sequencing profiles of ESCC patients, and to develop a gene-expression signature for identifying LN metastasis. The robustness of this panel was assessed in 2 independent patient cohorts (n = 56 and 224).

RESULTS

We initially prioritized a 16-gene signature out of the total 20,531 mRNAs. The model estimated by these 16 genes discriminated LN status with an area under the curve (AUC) of 0.77 [95% confidence interval (95% CI), 0.68-0.87, 5-fold cross-validation]. Subsequently, a reduced and optimized 5-gene panel was trained in a clinical cohort, which effectively distinguished ESCC patients with LN metastasis (cohort-1: AUC, 0.74; 95% CI, 0.58-0.89; cohort-2, T1-T2: AUC, 0.74; 95% CI, 0.63-0.86), and was significantly superior to preoperative computed tomography (AUC, 0.61; 95% CI, 0.50-0.72). Furthermore, a combination signature comprising of the 5-gene panel together with the lymphatic vessel invasion (LVI) and venous invasion (VI) demonstrated a significantly improved diagnostic performance compared with individual clinical variables, in both cohorts (cohort-1: AUC, 0.87; 95% CI, 0.78-0.96; cohort-2: AUC, 0.76; 95% CI, 0.65-0.88).

CONCLUSION

Our novel 5-gene panel is a robust diagnostic tool for LN metastasis, especially in early-T stage ESCC patients, with a promising clinical potential.

Prognostic alternative splicing signatures and underlying regulatory network in esophageal carcinoma

Alternative splicing (AS) has been widely reported to play an important role in cancers, including esophageal carcinoma (ESCA). However, no study has comprehensively investigated the clinical use of combination of prognostic AS events and clinicopathological parameters. Therefore, we collected 165 ESCA patients including 83 esophageal adenocarcinoma (EAC) and 82 esophageal squamous cell carcinoma (ESCC) patients from The Cancer Genome Atlas to explore the survival rate associated with seven types of AS events. Prognostic predictors for the clinical outcomes of ESCA patients were built. Predictive prognosis models of the alternative acceptor site in ESCA (area under the curve [AUC] = 0.83), alternative donor site in EAC (AUC = 0.99), and alternative terminator site in ESCC (AUC = 0.974) showed the best predictive efficacy. A novel combined prognostic model of AS events and clinicopathological parameters in ESCA was also constructed. Combined prognostic models of ESCA all showed better predictive efficacy than independent AS models or clinicopathological parameters model. Through constructing splicing regulatory network, the expression of AS factor was found to be negatively correlated with the most favorable AS events. Moreover, gene amplification, mutation, and copy number variation of AS genes were commonly observed, which may indicate the molecular mechanism of how the AS events influence survival. Conclusively, the constructed prognostic models based on AS events, especially the combined prognostic models of AS signatures and clinicopathological parameters could be used to predict the outcome of ESCA patients. Moreover, the splicing regulatory network and genomic alteration in ESCA could be used for illuminating the potential molecular mechanism.

Triptolide prevents proliferation and migration of Esophageal Squamous Cell Cancer via MAPK/ERK signaling pathway

Triptolide, the component of traditional Chinese herb, has been used as an inflammatory medicine and reported to be anti-tumor for various cancers recently. However, the effect of triptolide on Esophageal Squamous Cell Cancer (ESCC) has not yet been elucidated. In the study, we found that triptolide significantly inhibited cell proliferation, invasion, migration and survivability of ESCC cells. Moreover, we observed that triptolide induced ESCC cell cycle arrest at the G1/S phase and apoptosis through cyclin D1-CDK4/6 regulation and caspases activation. In addition, we revealed that triptolide regulates cell apoptosis and metastasis by p53 and mitogen-activated protein kinases/extracellular signal-regulated kinase (MAPK/ERK) signaling pathway, respectively. Meanwhile, the inhibitory effect of triptolide on ESCC was validated in mouse xenograft model. So, we propose that triptolide may be a candidate drug for ESCC.

An Association and Meta-Analysis of Esophageal Squamous Cell Carcinoma Risk Associated with PLCE1 rs2274223, C20orf54 rs13042395 and RUNX1 rs2014300 Polymorphisms

One of the highest risk of esophageal squamous cell carcinoma (ESCC) in the world has been reported in Iran, which is located in the Asian esophageal cancer belt. ESCC constitutes 90% of the esophageal cancer cases in Iran. Genome wide association studies (GWASs) in Chinese have identified a number of candidate variants, of which PLCE1rs2274223, C20orf54rs13042395 and RUNX1rs2014300 are studied in high risk populations including Chinese, Caucasians and Africans. However, results are inconsistent and it is unknown whether similar associations exist in Iranian population. We evaluated association of three GWAS identified variants with risk of ESCC in an Iranian cohort consisted of 200 ESCC patients and 300 healthy controls and conducted meta-analysis of ESCC risk associated with rs2274223 (involving 9810 cases and 13,128 controls) and rs13042395 (involving 2363 cases and 5329 controls). Logistic regression analysis showed that rs2274223 was associated with ESCC under codominant [GG/AA, 2.47(1.17-5.23), P:0.021], dominant [AG + GG/AA, 1.57(1.09-2.27), P:0.016], recessive [GG/AA+AG, 2.18(1.04-4.56), P:0.036] and log-additive models [1.51(1.12-2.02), P:0.006]. C20orf54 rs13042395 was not associated with ESCC under any genetic model. RUNX1 rs2014300 was associated with risk of ESCC assuming codominant [AG/GG, 0.63(0.41-0.97), P:0.018], dominant [AG + AA/GG, 0.59 (0.39-0.89), P:0.010] and log-additive models [0.61 (0.42-0.87), P: 0.005]. Meta-analysis found significant associations between rs2274223 and ESCC under all analyzed genetic models. However, meta-analysis stratified by ethnicity showed a significant association in Asians but not non-Asian populations. No significant association was found for rs13042395 in meta-analysis. This study provided first evidence for association of GWAS-identified variants with risk of ESCC in an Iranian cohort.

FLI-06 suppresses proliferation, induces apoptosis and cell cycle arrest by targeting LSD1 and Notch pathway in esophageal squamous cell carcinoma cells

Aberrant activation of the Notch signaling plays an important role in progression of esophageal squamous cell carcinoma (ESCC) and may represent a potential therapeutic target for ESCC. FLI-06 is a novel Notch inhibitor, preventing the early secretion of Notch signaling. However, little information about the antitumor activity of FLI-06 has been reported so far. To evaluate the anti-tumor activity and possible molecular mechanism of FLI-06 to ESCC cells, the effects of FLI-06 on cell viability, apoptosis and cell cycle were evaluated by CCK-8 and flow cytometry assays, respectively, in ESCC cell lines ECa109 and EC9706, and the expressions of proteins in Notch signaling pathway and LSD1 were investigated after cells were treated with FLI-06 by Western blotting. The results showed that FLI-06 blocked proliferation, induced apoptosis and G₁ phase arrest of ESCC cells in a dose-dependent manner. Mechanistically, we found FLI-06 could inhibit Notch signaling pathway by decreasing the expressions of Notch3, DTX1 and Hes1. Interestingly, we also found that the expression of LSD1 (histone lysine specific demethylase 1), which is dysregulated in multiple tumors, was also inhibited by FLI-06. In addition, inhibition of Notch pathway by γ-secretase inhibitor GSI-DAPT could also inhibit LSD1 expression. The current study demonstrated that FLI-06 exerts antitumor activity on ESCC by inhibiting both LSD1 and Notch pathway, which provides the theory support for the treatment of ESCC with FLI-06.

SLC52A3 expression is activated by NF-κB p65/Rel-B and serves as a prognostic biomarker in esophageal cancer

The human riboflavin transporter-3 (encoded by SLC52A3) plays a prominent role in riboflavin absorption. Interestingly, abnormal expression patterns of SLC52A3 in multiple types of human cancers have been recently noted. However, the molecular mechanisms underlying its dysregulation remain unclear. In this study, we find that SLC52A3 has two transcript variants that differ in the transcriptional start site, and encode different proteins: SLC52A3a and SLC52A3b. Importantly, aberrant expressions of SLC52A3 are associated with stepwise development of esophageal squamous cell carcinoma (ESCC) as well as the survival rates of ESCC patients. Functionally, SLC52A3a, but not SLC52A3b, strongly promotes the proliferation and colony formation of ESCC cells. Furthermore, SLC52A3 5'-flanking regions contain NF-κB p65/Rel-B-binding sites, which are crucial for mediating SLC52A3 transcriptional activity in ESCC cells. Chromatin immunoprecipitation and electrophoretic mobility shift assay reveal that p65/Rel-B bind to 5'-flanking regions of SLC52A3. Accordingly, NF-κB signaling upregulates SLC52A3 transcription upon TNFα stimulation. Taken together, these results elucidate the mechanisms underlying SLC52A3 overexpression in ESCC. More importantly, our findings identify SLC52A3 as both a predictive and prognostic biomarker for this deadly cancer.