Accumulating evidence suggest that NOX is the key enzyme that the earliest known system for producing ROS༎Of note, a small amount of ROS can enhance immune defense and participate in the regulation of cell differentiation, proliferation, apoptosis, and intercellular signaling pathways. Excessive ROS can cause oxidative stress, accelerating the pathogenesis of inflammation, fibrosis, and tumor formation༎Thus, NOX serve significant roles in cancer initiation and progression and diagnosis. Previous studies indicate that NOX1 are associated with patient survival or drug-resistance in human tumors and may be utilized as promising therapeutic targets[24]. It has been widely reported that NOX1 is a member of NOX family༎NOX1-mediated ROS production that regulate exocytosis seems to be vital for cancer development in human cancers, associating with unfavorable metastasis and OS in a number of human cancers. Furthermore, NOX1 has been verified as a biomarker of prognosis in partial human cancers and correlated with the degree of cancer progression as well.
More importantly, recent studies have shown that as one of the main sources of ROS, NOX1 plays key roles in cancer transformation and invasion progression [25, 26], and it is overexpressed in various types of cancer such as breast cancer, colon cancer, gastric cancer, stomach cancer and prostate cancer [25, 27, 28]. Then, NOX1 has been proposed to function as an oncogene and a therapeutic target [29, 30]. In addtion, it is suggested that expression of NOX1 might also be relatively high in human colon epithelial cells compared with that in other normal cell types [31].
All the above indicate the oncogenic characteristics of NOX1. Hence, we attempted to focuse on the association between NOX1 expression and certain clinicopathological features of GIST. We also showed that NOX1 is mainly localized at cytoplasm. Here, signicance positive staining of low NOX1 was presented in the cytoplasm of GIST cells (78 of 146). We further carry out the univariate and multivariate cox's survival analysis to associate the low NOX1 expression, the clinicopathological parameters and OS of GIST. As shown in Table 2, low NOX1 status, mitotic index were associated with reduced survival in patients with GIST. NOX1 may promote tumor development. Therefore, low expression of NOX family- derived NOX1 and advanced mitotic index may be found as an independent prognostic factor for GIST patients. Kaplan–Meier survival curves showed that longer OS was strongly associated with a low NOX1 expression and a favorable prognosis for GIST patients. Meanwhile, with the increase in the level of mitotic index (per 50 HPFs), the positive expression rate of NOX1 increased significantly. This paper explored immunoexpression of NOX1 protein and its roles and prognostic in tumors, in order to explore the effective targets for diagnosis and predicte poor prognosis of patients with GIST. Furthermore, we also analysed the relationship between NOX1 expression of GIST patients in the Oncomine databases online resources. It was presented that NOX1 protein and mRNA expression levels were both significantly higher in GIST compared with normal GIST tissues(Figure. 4). Intriguingly, these results were consistent with our data of NOX1 protein expression in the previous research.
Collectively, novelty of the present findings is that low NOX1 expression is confirmed as a useful prognostic marker in the occurrence and progress of GIST and moreover, a useful predictive marker in patients never receiving preoperative radiotherapy or chemotherapy in all stages of the disease. Conversely, GIST patients with high expression of NOX1, there was no significant survival difference in disease progression. Nevertheless, how effects of NOX is involved in cancer cell proliferation, migration and invasion were not referred to in vitro, whether NOX1 is involved in ROS production remains poorly understood and also requires further investigation. Additionally, the development of inhibitors against NOX and ROS-related redox signaling components as well as understanding the underlying mechanism might provide effective therapeutic strategies for treatment of malignant tumor and define the role of each NOX individual and its regulatory pathways [32]. Significant analysis NOX-1 gene and other NOX isoforms and molecular mechanisms in cancer development remains to be performed in future studies.