Background Periodontal bacteria is the major pathogens in the oral cavity and the main cause of adult chronic periodontitis, but their association with incidence and prognosis in cancer is controversial. The aim of this study was to evaluate the effect of periodontal bacteria infection on incidence and prognosis of cancer.Methods A systematic literature search of PubMed, Embase, Web of Science and Cochrane Library databases was performed to obtain 39 studies comprising 7184 participants. The incidence of cancer was evaluated as odd ratios (OR) with a 95% confidence interval (95% CI) using Review Manager 5.2 software. Overall survival (OS), cancer-specific survival (CSS) and disease-free survival (DFS), which were measured as hazard ratios (HR) with a 95% confidence interval (95% CI) using Review Manager 5.2 software.Results Our results indicated that periodontal bacteria infection increased the incidence of cancer (OR=1.25; 95%CI: 1.03–1.52) and was associated with poor OS (HR = 1.75; 95% CI: 1.40–2.20), DFS (HR=2.18; 95%CI: 1.24–3.84) and CSS (HR=1.85, 95%CI: 1.44–2.39). Subgroup analysis indicted that the risk of cancer was associated with Porphyromonas gingivalis (Pg) infection (OR=2.16; 95%CI: 1.34–3.47) and Prevotella intermedia (Pi) infection (OR=1.28; 95%CI: 1.01–1.63) but not Tannerella forsythia (Tf) (OR=1.06; 95%CI: 0.8–1.41), Treponema denticola (Td) (OR=1.30; 95%CI: 0.99–1.72), Aggregatibacter actinomycetemcomitans (Aa) (OR=1.00; 95%CI: 0.48–2.08) and Fusobacterium nucleatum (Fn) (OR=0.61; 95%CI: 0.32–1.16).Conclusion This meta-analysis revealed periodontal bacteria infection increased the incidence of cancer and predicted poor prognosis of cancer.

Background Secernin-1 (SCRN1) is a regulator of exocytosis in mast cells. Recently, SCRN1 has been reported to be correlated with the prognosis of colorectal cancer and gastric cancer but its functional effects on oral squamous cell carcinoma (OSCC) remains unclear. Our aim was to explore the expression pattern and the migration and invasion effects of the newly identified SCRN1 in OSCC. Methods Western blotting (WB) was used to measure SCRN1 expression in human OSCC tissue samples and OSCC cell lines. Then, the effects of SCRN1 on OSCC cell proliferation, invasion and metastasis were analyzed by cell counting kit-8 (CCK-8) and transwell assays. The secretion of matrix metalloproteinase (MMP)-2 and MMP-9 in SCRN1 knockdown OSCC cells and vector cells was investigated by enzyme-linked immunosorbent assay (ELISA). The expression levels of TGF-β, Smad3 and phosphorylated Smad3 (p-Smad3) in SCRN1 knockdown OSCC cells and vector cells were measured by WB. Results The expression of SCRN1 was significantly elevated in the OSCC tissues and cell lines. Furthermore, SCRN1 knockdown attenuated the proliferation, migration and invasion of SCC15 and HSC3 cells. SCRN1 knockdown reduced the secretion of MMP-9 from HSC3 and SCC15 cells, but the secretion of MMP-2 did not obviously change. Additionally, SCRN1 knockdown reduced the expression of TGF-β and p-Smad3 in HSC3 and SCC15 cells. Conclusions Our study demonstrated that SCRN1 is upregulated in OSCC. Further studies demonstrated that SCRN1 promotes proliferation, invasion and metastasis of OSCC cells via TGF-β/Smad3 signaling.