Search

AIM: To investigate the expression of syntaxin binding protein 4 (STXBP4) in oral squamous cell carcinoma (OSCC) and its effects on the malignant biological behavior of OSCC cells. METHODS: (1) The TIMER, GEPIA2, UALCAN, ENCORI, GEO and HPA databases were used to comprehensively study the expression of STXBP4 in head and neck squamous cell carcinoma (HNSCC) tissues at mRNA and protein levels. The mRNA and protein expres⁃ sion levels of STXBP4 in OSCC cell lines were detected by qPCR and Western blot, respectively. (2) The expression of STXBP4 in SCC-9 cells was down-regulated by small interfering RNA (siRNA), and knockdown (si-STXBP4-1, si-STXBP4-2 and si-STXBP4-3) groups and negative control (si-NC) group were established. Overexpression of SCAL-27 cells was achieved by lentivirus transfection, and overexpression (LV-STXBP4) group and negative control (LV-NC) group were established. The viability, colony formation and migration of OSCC cells were examined by CCK-8, plate colony formation, and Transwell assays, respectively. Western blot was used to detect the expression of epithelial-mesen⁃ chymal transition (EMT)-related proteins. (3) By establishing a subcutaneous xenograft tumor model in nude mice, we in⁃ vestigated the effect of STXBP4 on the proliferation of OSCC cells in vivo. RESULTS: (1) Analysis of the TIMER, GE⁃ PIA2, UALCAN, ENCORI and GEO databases revealed that HNSCC tissues had higher STXBP4 mRNA levels than nor⁃ mal tissues. Immunohistochemical staining from HPA database showed that STXBP4 protein in HNSCC tissues was higher than that in normal oral mucosa tissues. In contrast to normal oral mucosa cells, STXBP4 was highly expressed in 5 OSCC cell lines (P<0. 05). (2) The relative expression of STXBP4 in SCC-9 cells transfected with si-STXBP4-1, si-STXBP4-2 and si-STXBP4-3 was significantly lower than that in si-NC group (P<0. 01). Compared with si-NC group, knockdown of STXBP4 resulted in decreased proliferation and migration of SCC-9 cells (P<0. 05). The CAL-27 cells transfected with LV-STXBP4 had considerably higher STXBP4 level than the cells in LV-NC group (P<0. 01), and had markedly better proliferation and migration abilities than those in LV-NC group (P<0. 01). The protein expression of N-cadherin decreased and that of E-cadherin increased after STXBP4 expression was knocked down, while STXBP4 overexpression exerted the opposite effects (P<0. 05). (3)In vivo, overexpression of STXBP4 increased the volume and weight of xenograft tumors in nude mice (P<0. 05). CONCLUSION: High expression of STXBP4 promotes the proliferation and migration of OSCC cells, and its effect on the migration behavior of OSCC cells may be related to EMT. [ABSTRACT FROM AUTHOR]

【Objective】The study aimed to explore the molecular characteristics and the expression regulation pattern of STR gene（CsSTR） in tea plant（Camellia sinensis）, so as to lay the foundation for further functional analysis of CsSTR gene and for mining the medicinal value of tea. 【Method】By employing the RACE technology, CsSTR1 gene was cloned. The physicochemical properties, protein structure, subcellular localization and phylogenetic relationship of CsSTR1 protein were studied by the methods of bioinformatics. Expression pattern of CsSTR1 gene was analyzed by qPCR. 【Result】The full length of CsSTR1 cDNA was 1382 bp, containing 92 bp 5′ UTR, 159 bp 3′ UTR, 1131 bp CDS. The CsSTR1 protein had 376 aa, with the molecular weight being 41.5 kD, the theoretical isoelectric point being 6.36, the instability index being 29.74, the aliphatic index being 88.94, and the grand average of hydropathicity being-0.077. Subcelluar analysis revealed that the CsSTR1 protein was localized in vacuole. The proportions of random coil, extended strand, α-helix and β-turn in the secondary structure of CsSTR1 protein were 42.82%, 29.79%, 16.76%, and 10.64%, respectively. The three-dimensional structure of CsSTR1 protein displayed as six-bladed β-propeller. The phylogenetic analysis revealed a close genetic relationship between CsSTR1 and rice OsSTRL2 protein. qPCR results showed that CsSTR1 gene was expressed in various organs of tea plant, with higher expression levels in buds, the first leaf, the second leaf and the third leaf, with lower expression levels in flowers and fruits. Up-regulation of CsSTR1 gene was seen under low temperature, PEG simulated drought stress, MeJA and SA treatments; Expression of CsSTR1 gene was down-regulated by ABA after 24-48 hours of the treatment. 【Conclusion】The results suggest that CsSTR1 has an important role in both the buds and leaves development of tea plant and defense response to adversity stress, MeJA, SA and ABA can regulate the CsSTR1 gene expression. [ABSTRACT FROM AUTHOR]