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  • br Conclusions This study showed that in EOC

    2020-09-18


    Conclusions This study showed that in EOC cells, tyrosine kinase receptor DDR1 was expressed mainly in EOC KN-92 phosphate with an Epithelial phenotype. The repressed expression of DDR1 in EOC cells with Mesenchymal phenotype could be due to the higher CpG methylation levels observed at the promoter of this gene. The negative correlation between DDR1 expression with EMT suggested that EOC tumours with an Epithelial phenotype, but not those with a Mesenchymal phenotype, might give better response to DDR1-targeting drugs. More extensive works are needed to validate the importance of DDR1 in EOC progression.
    Introduction Gastric cancer (GC) is the fourth most common type of cancer and the second leading cause of cancer-associated mortality worldwide [1]. Although numerous novel chemotherapy regimens have been developed and surgical skills and instruments for the treatment of GC have also improved, the survival rate remains low [2]. One of the reasons for the poor prognosis of GC is the inability of anticancer agents to target tumor cells and tissues selectively [3]. Thus, the search for a promising therapeutic target and a novel prognostic biomarker for GC is of great interest. GC tissues often show histological heterogeneity, containing intestinal and diffuse subtypes. In particular, the diffuse type of GC has rich stromal components, consisting of rich collagen [4]. Recently, the interaction between cancer cells and the stroma has been thought to be primarily responsible for tumor progression and metastasis. Discoidin domain receptors (DDRs) are unique receptor tyrosine kinases (RTKs) that bind to and are activated by collagens [5], [6]. Among the collagen receptor families, DDRs are the only RTKs phosphorylated by various collagens [7], [8], [9]. Various types of collagen act as ligands for DDRs. DDR1 is activated by collagens of type I-VI and VIII, whereas DDR2 is activated by the fibrillar collagens, in particular the collagens of type I and type III [7]. DDR1 is reported to be preferentially expressed in highly invasive cancer cells, whereas DDR2 is mainly expressed in surrounding stromal cells [10]. DDR1 has been reported to be highly expressed in a variety of neoplasms, including those in the lung, liver, ovary, and breast, and other types of tumors [11], [12], [13], [14]. In highly invasive non–small cell lung cancer, DDR1 is reported to be significantly correlated with lymph node metastasis and poor prognosis [11], [15]. In pancreatic ductal adenocarcinoma, high expression of DDR1 was found to be significantly associated with poor prognosis [16]. Recently, Hoon et al. reported that DDR1 expression in GC patients receiving adjuvant chemotherapy was an independent prognostic factor [17]. DDR1 is reported to regulate diverse functions of tumor cells, including cellular adhesion and morphogenesis, differentiation, migration and invasion, extracellular matrix (ECM) remodeling, proliferation, and apoptosis [14], [18], [19], [20]. However, the role of DDR1 in GC progression and metastasis is not yet well understood.
    Materials and Methods
    Results
    Discussion Tumor cells must undergo a series of sequential, interrelated, selective steps for metastasis to occur. These steps include growth, vascularization, invasion of the host stroma, entrance into and survival in the circulatory system, adhesion to capillary endothelial cells, extravasation into the organ parenchyma, response to local growth factors, proliferation, and induction of vascularization. Tumor growth and metastasis are determined not by cancer cells alone but also by interactions between cancer cells and various kinds of stromal components. The tumor stroma consists of carcinoma-associated fibroblasts, smooth muscle cells, inflammatory cells, microvessels, and abundant ECM [25]. Collagen fibers are the most abundant fibrous protein within the ECM. DDR1 is an RTK that is activated by most matrix collagens, such as types I to V, VIII, and XI, and it has been shown to be involved in numerous cellular functions, including differentiation, proliferation, adhesion, migration, and invasion [26], [27], [28], [29], [30].