SEC11A contributes to tumour progression of head and neck squamous cell carcinoma.

Background: Head and neck squamous cell carcinoma (HNSCC) is a prevalent disease that has a low survival rate and high recurrence risk. Our study aims to investigate the expression and role of SEC11A in HNSCC. Methods: The expression of SEC11A was assessed in 18 pairs of cancerous and adjacent tissues by qRT-PCR and western blotting. Immunohistochemistry was performed in clinical specimen sections to evaluate the expression of SEC11A and its association with outcomes. Furthermore, the functional role of SEC11A in HNSCC tumor proliferation and progression was investigated using the in vitro cell model with lentivirus-mediated SEC11A knockdown. Colony formation and CCK8 assays were conducted to assess cell proliferation potential, while in vitro migration and invasion were examined using wound healing and transwell assays. To determine the tumor formation potential in vivo, a tumor xenograft assay was used. Results: In contrast to adjacent normal tissues, SEC11A expression was significantly elevated in HNSCC tissues. SEC11A was mainly localized in the cytoplasm, and its expression was significantly associated with patient prognosis. SEC11A was silenced using shRNA lentivirus in TU212 and TU686 cell lines, and the gene knockdown was confirmed. A series of functional assays demonstrated that SEC11A knockdown reduced cell proliferation, migration and invasion ability in vitro. In addition, the xenograft assay demonstrated that SEC11A knockdown significantly inhibited tumor growth in vivo. Tumor tissue sections of mice showed decreased proliferation potential in the shSEC11A xenografts cells by immunohistochemistry. Conclusion: SEC11A knockdown decreased cell proliferation, migration and invasion in vitro and subcutaneous tumorigenesis in vivo. SEC11A is crucial to HNSCC proliferation and progression, and may serve as a new therapeutic target.

Clinical Significance of SEC11A Expression in Patients With Locally Advanced Gastric Cancer.

BACKGROUND/AIM: SEC11A gene encodes the SPC18 protein, which has been implicated in tumour progression by inducing the secretion of various growth factors. We investigated the clinical significance of SEC11A expression in gastric cancer (GC) tissues in patients with locally advanced gastric cancer (LAGC) after curative resection. PATIENTS AND METHODS: We estimated SEC11A expression in cancer tissues from 253 pStage II/III GC patients who underwent curative resection using quantitative polymerase chain reaction (PCR) and investigated the relationship of SEC11A expression with clinicopathological factors and survival. RESULTS: SEC11A expression was significantly related to serosal invasion, lymph node metastasis, lymphatic invasion, and pathological stage. The high-SEC11A expression group had a significantly lower survival rate than the low group (5-year survival 52.3% vs. 75.9%; p<0.005). Furthermore, in multivariate analysis, high-SEC11A expression was an independent factor of poor survival (hazard ratio, 2.010; 95% confidence interval=1.303-3.100; p=0.002). CONCLUSION: SEC11A expression in cancer tissue may be a useful prognostic marker in patients with LAGC after curative resection.

SPC18 Expression Is an Independent Prognostic Indicator of Patients with Esophageal Squamous Cell Carcinoma.

OBJECTIVES: Esophageal cancer is the sixth most common malignancy worldwide. Signal peptidase complex 18 (SPC18) protein, which is encoded by the SEC11A gene, is one of the subunits of the signal peptidase complex and plays an important role in the secretion of proteins including transforming growth factor α (TGF-α). In this study, we investigated the significance of SPC18 expression in human esophageal squamous cell carcinoma (ESCC). METHODS: SPC18 expression was examined by immunohistochemistry. RNA interference was used to inhibit SPC18 expression in ESCC cell lines. To examine cell viability, we performed 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. The effects of SPC18 inhibition on epidermal growth factor receptor (EGFR) signaling were analyzed by Western blot. RESULTS: In total, 46 (50%) of 92 ESCC cases were positive for SPC18. SPC18 staining was observed more frequently in stage II/III/IV cases than in stage I cases (p = 0.028). We found that SPC18 expression was significantly associated with increased cancer-specific mortality (p = 0.006, log-rank test). SPC18 expression was frequently found in EGFR-positive cases compared with EGFR-negative cases. Cell proliferation and EGFR signaling were inhibited by SPC18 knockdown. CONCLUSION: Specific inhibitors of SPC18 may be promising anticancer drugs for patients with ESCC.

Long non-coding RNA DDX11-AS1 facilitates gastric cancer progression by regulating miR-873-5p/SPC18 axis.

Gastric cancer (GC) is a malignant tumour with high lethality. Accruing evidence elucidates the critical adjusting role of long non-coding RNA (lncRNAs) in human cancers. DDX11 antisense RNA 1 (DDX11-AS1) was previously found to be involved in GC pathogenesis. However, the precise molecular mechanisms of DDX11-AS1 need to be further investigated. In this study, we found that DDX11-AS1 expression was up-regulated in GC tumour tissues and cells. Increased DDX11-AS1 expression was associated with advanced TNM stage and lymph node metastasis. Functionally, knockdown of DDX11-AS1 repressed cell proliferation and clone formation, while induced cell cycle arrest and apoptosis. As expected, DDX11-AS1 overexpression displayed the opposite effect. Mechanically, DDX11-AS1 enhanced SPC18 expression through acting as a ceRNA for miR-873-5p. Furthermore, the inhibitory effect of DDX11-AS1 silencing on malignant biological behaviour of GC cells was attenuated by either miR-873-5p inhibitor or SEC11A up-regulation. Moreover, suppression of DDX11-AS1 also decreased GC tumorigenesis in vivo. In conclusion, DDX11-AS1 may serve as an oncogene in GC progression by sponging miR-873-5p and promoting SPC18 expression, providing a new insight into the mechanisms of DDX11-AS1 and elucidating a promising therapy target in GC.

SEC11A Expression Is Associated with Basal-Like Bladder Cancer and Predicts Patient Survival.

OBJECTIVES: Bladder cancer (BC) is a common malignancy worldwide. Signal peptidase complex 18 (SPC18) protein, which is encoded by the SEC11A gene, is one of the subunits of the signal peptidase complex and induces transforming growth factor-α secretion. In the present study, we analyzed the expression and function of SPC18 protein in human BC. METHODS: Expression of SPC18 was analyzed by immunohistochemistry. RNA interference was used to inhibit SEC11A expression in BC cell lines. For constitutive expression of the SEC11A gene, a SEC11A expression vector was transfected into BC cell lines. To examine cell viability, we performed 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Modified Boyden chamber assays were used to examine cell invasiveness. RESULTS: SPC18 was upregulated in 54% of 81 BC cases. SPC18 expression served as an independent prognostic classifier of patients with BC. SPC18-positive BC cases frequently expressed cytokeratin 5/6, a marker of basal-like BC. Cell growth and invasiveness were inhibited by SEC11A knockdown and enhanced by forced expression of SEC11A. CONCLUSION: These results indicate that SPC18 plays an important role in the progression of BC. Specific inhibitors of SPC18 may be promising anticancer drugs for patients with basal-like BC.

The Natural Product Cavinafungin Selectively Interferes with Zika and Dengue Virus Replication by Inhibition of the Host Signal Peptidase.

Flavivirus infections by Zika and dengue virus impose a significant global healthcare threat with no US Food and Drug Administration (FDA)-approved vaccination or specific antiviral treatment available. Here, we present the discovery of an anti-flaviviral natural product named cavinafungin. Cavinafungin is a potent and selectively active compound against Zika and all four dengue virus serotypes. Unbiased, genome-wide genomic profiling in human cells using a novel CRISPR/Cas9 protocol identified the endoplasmic-reticulum-localized signal peptidase as the efficacy target of cavinafungin. Orthogonal profiling in S. cerevisiae followed by the selection of resistant mutants pinpointed the catalytic subunit of the signal peptidase SEC11 as the evolutionary conserved target. Biochemical analysis confirmed a rapid block of signal sequence cleavage of both host and viral proteins by cavinafungin. This study provides an effective compound against the eukaryotic signal peptidase and independent confirmation of the recently identified critical role of the signal peptidase in the replicative cycle of flaviviruses.