| Summary: | 碩士 === 國立中山大學 === 生物科學系研究所 === 104 === Backgrounds: Oral cancer is one of the most common cancers worldwide and the fourth leading cause of cancer death among males in Taiwan. Interferons (IFNs) including Type I IFNs (IFN-α/β) and type II IFNs (IFN-γ) are well-known potent cytokine in host defenses against infection with viral and microbial pathogens. However, they have been proven in malignant transformation of tumor cells. Guanylate binding protein (GBP) 5 and GBP6 belong to the guanosine triphosphatase (GTPase) superfamily, which plays an important role in cell proliferation, differentiation, signal transduction, and intracellular protein transportation. In addition, GBP expression is mostly induced by IFN-γ. On the other hand, DDX60, a subtype of DEXD/H Box Helicase, is required for RIG-I- or MDA5-dependent type I interferon production. DDX60 belongs to a DEAD box RNA helicase involving in most cellular processes, such as essential for cancer development. However, roles of GBP5, GBP6 and DDX60 in cancer especially for oral squamous cell carcinoma (OSCC) were not identified so far. The purpose of this study was to investigate the association of the expression levels of GBP5, GBP6 and DDX60 with tumorigenesis, clinicopathologic outcomes, and survival of patients with OSCC and three primary subsites.
Methods: Our preliminary data from next generation sequencing (NGS) indicated that in two pairs of OSCC and corresponding tumor adjacent normal (CTAN) tissues, the gene expressions of GBP5 and DDX60 in OSCC tissue were significant higher than that in CTAN tissue but the GBP6 gene expression in OSCC tissue was significant decreased than that in CTAN tissue. Gene expressions of GBP5, GBP6 and DDX60 were further confirmed by real-time polymerase chain reaction (RT-PCR) using 23 pairs of mucosa squamous cell carcinoma (BMSCC) and CTAN tissues as well as 14 pairs of tongue squamous cell carcinoma (TSCC) and CTAN tissues. In the study, expression levels of GBP5, GBP6 and DDX60 were examined by immunohistochemistry with tissue microarray slides of 494 OSCC patients including 180 buccal mucosal SCC (BMSCC), 241 tongues SCC (TSCC), and 73 lip SCC (LSCC) patients.
Results: The expression results of GBP5, GBP6 and DDX60 assayed by NGS, RT-PCR and immunohistochemical staining were quite consistent. GBP5 and DDX60 expressions (all p <0.05) significantly increased, whereas GBP6 (p <0.001) expression decreased in tumor tissues compared to that in CTAN tissues, indicating that GBP5 and DDX60 might be oncoproteins, but GBP6 was a tumor suppressor. Among OSCC tissues of 494 patients, the higher GBP5 expression was associated with older age over 50 yrs. (>50 yrs.; p=0.019) and well differentiation (p=0.036), whereas decreased GBP6 expression was associated with poor differentiation (p<0.001). Among BMSCC tissues of 180 patients, the GBP5 expression was positively associated with older age (>50 yrs.; p=0.021), although GBP6 expression was negatively associated with poor differentiation (p=0.039). Among TSCC tissues of 241 patients, the loss of GBP6 expression was associated with poor differentiation (p<0.001) and lymph node metastasis (N1- N2, p=0.047). Moreover, the decreased GBP6 expression was correlated with the poor disease-specific survival (DSS) for only TSCC patients. Increased DDX60 expression was associated with males (p=0.002), well differentiation (p=0.004), advanced pathological stage (III-IV, p=0.023), and large tumor size (T3-T4, p=0.001) in OSCC. Higher DDX60 expression was associated with advanced pathological stage (III-IV, p=0.042) and larger tumor size (T3-T4, p=0.032) in BMSCC. Higher DDX60 expression was positively associated with males (p=0.023), well differentiation (p<0.001), and large tumor size (T3-T4, p=0.017) in TSCC. Moreover, the elevated DDX60 expression was correlated with the poor DSS in LSCC patients, and the poor disease-free survival (DFS) in OSCC, especially in TSCC patients.
Conclusion: GBP5 may be the biomarkers for tumor development but not for prognosis in OSCC. GBP6 may be a predictor of better prognosis in TSCC. DDX60 may be the biomarkers for tumor development and prognosis of OSCC, particularly for survival of LSCC and recurrence of TSCC.
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