Then the membranes were subsequently incubated with horseradish peroxidase-linked secondary antibody anti-Crm1 rabbit IgG (1/3000, Cat# ab9705; Abcam) and anti–actin mouse IgG (1/2500, Cat #7076P2; Cell Signaling Technology, Danvers, MA, USA) at 37?C for 1?h with shaking, and the bound proteins were visualized by ECL substrate (Cat# 1705060; Bio-Rad, Hercules, CA, USA) using the ChemiDoc MP Imaging System (BioRad). expression levels in HNSCC cells through either treatment with specific Crm1 RNA interference (siRNA) or the selective Crm1 inhibitor leptomycin B (LMB), cell viability, proliferation, migration, and wound-healing abilities decreased, suppressing tumorigenic properties through the induction of apoptosis. Crm1 Atosiban Acetate is a powerful diagnostic biomarker because of its central role in cancerogenesis, and it has a high potential for the development of targeted Crm1 molecules or synthetic agents, such as LMB, as well as for the improvement of the clinical features in head and neck cancer. Keywords: Head and neck cancer, chromosome region maintenance 1, metastasis, RNA interference, leptomycin B 1. Introduction Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer type and represents the third most common cause of cancer-related deaths worldwide (Stell et al., 1989; Jemal et al., 2009) . It constitutes 4% of all cancer cases, resulting in approximately 650,000 new cases and 400,000 deaths annually (Mao et al., 2004; Siegel et al., 2014) . In most cases of HNSCC, only 51% of short-term malignancies and only 10.5% of long-term malignancies could be detected even with advanced investigations. Five year survival rates are 51% in short-term malignancies and 28% in long-term malignancies (Jemal et al., 2009). The underlying mechanism of HNSCC invasion and metastasis is a multistep process characterized by multiple genetic and molecular changes (Wilken et al., 2011) . However, not all of the underlying molecular mechanisms of HNSCC pathology are clear. Additionally, despite the standard therapies, including radiation, surgery, and/or chemotherapy, there has been no significant change in the survival rate within the last 20C30 years, and the mortality rate for HNSCC is still high (Jemal et al., 2009). Therefore, it is XRP44X very important to investigate new candidate molecules for the diagnosis, follow-up, and control of HNSCC. Moreover, the investigation of potential target molecules that may be responsible for the HNSCC pathogenesis is crucial for the development of new clinical therapeutic approaches. Chromosome region maintenance 1 (Crm1), a member of the cytoplasm-nucleus transport receptor family known as the karyopherins, is an important nuclear export protein in mammals that facilitates the transport of various classes of RNAs, proteins, and other macromolecules from the nuclear membrane to the cytoplasm, and it helps maintain their appropriate subcellular localization (Kudo et al., 1997; Nguyen et al., 2012; Turner et al., 2012) . Crm1 has a broad range of substrates and recognizes numerous cargo proteins, which are rich in nuclear export signal (NES) sequences, including tumor suppressor proteins such as p53, p27, and p21. These tumor suppressor proteins carry NES sequences rich in leucine amino acids and hydrophobic residues (Fukuda et al., 1997; Henderson et al., 2000; Mariano et al., 2006; Chan et al., 2010; van der Watt et al., 2011; Brodie et al., 2012; Santiago et al., 2013; Fung et al., 2014) . Furthermore, transcription factors that are the target cargo proteins of Crm1 have critical roles in the regulation of intracellular processes via their expression levels and functions, which are regulated by the cell cycle and signaling proteins (Henderson et al., 2000; Mariano et al., 2006; Chan et al., 2010; van der Watt et al., 2011; Brodie et al., 2012; Santiago et al., 2013) . The deregulation of Crm1 expression, which is dependent on the cell cycle, results in the loss of cellular proliferation control through various intracellular pathways (Ishizawa et al., 2015). Recent studies on various cancer types have reported an increase in the expression level of Crm1 compared with healthy tissue, and this increase has been found to be associated with metastasis, histological grading, increased tumor size, and a decreased general survival rate (Noske et al., 2008; Shen et al., 2009; van der Watt et al., 2009, 2014; Yao et al., 2009; Zhou et al., 2013; Tai et al., 2014; Yang et al., 2014; Liu et al., 2016) . The increased expression level of Crm1 has also been shown to play a key role in carcinogenesis, and it was observed that in retrovirus-mediated small interfering RNA (siRNA)-introduced Crm1 knockdown cancer lines, the XRP44X proliferation and migration abilities of the cells were suppressed and apoptosis was induced (van der Watt et al., 2009, 2014; Yang et al., 2014) . Therefore, XRP44X Crm1, a nuclear export molecule, has become a significantly promising target for the treatment of cancer (Yashiroda et al.,.