Therefore, we set out to correlate expression of DDX3 and HIF-1 in a large set of human invasive breast cancers. downstream genes CAIX and GLUT1. Moreover, DDX3 expression correlated with hypoxia-related proteins EGFR, HER2, FOXO4, ER and c-Met in a HIF-1 dependent fashion, and with COMMD1, FER kinase, Akt1, E-cadherin, TfR and FOXO3A independent of HIF-1. Conclusions In invasive breast cancer, expression of DDX3 was correlated with overexpression of HIF-1 and many other hypoxia related proteins, pointing to a distinct role for DDX3 under hypoxic conditions and supporting the oncogenic role of DDX3 which could have clinical implication for current development of DDX3 inhibitors. Introduction In the Western world, one in eight women will develop breast cancer during their life and breast cancer is causing about 458.000 deaths worldwide per year , . Aggressive forms of breast cancer are frequently refractory to treatment , even to established targeted therapy, and thus have a high risk of relapse and formation of distant metastases . Identification of molecular pathways involved in aggressive forms of breast cancer is therefore important to design novel targeted therapeutic agents to counteract tumor progression and metastasis. DDX3, also known as DDX3X because of its location on the X chromosome, is a member of the DEAD-box RNA helicase family which is involved in transcription, RNA splicing, nuclear export of mRNA and translation initiation , . Initially, DDX3 was studied because of its manipulation by viruses like hepatitis C (HCV) and human immunodeficiency virus (HIV) , . Recently DDX3 has been associated with cancer . Conflicting evidence exists with regard to its tumor enhancing or repressing properties. Nevertheless, DDX3 was proven to have antiapoptotic properties , , promotes proliferation and cellular transformation, C. Recently, novel compounds were developed which could Oxibendazole Oxibendazole potentially inhibit DDX3 activityC. A recent study  showed that DDX3 is a direct downstream target of HIF-1, the predominant factor in the mammalian hypoxia response . Hypoxia is an important event in breast carcinogenesisC, causing a more aggressive phenotype with increased invasiveness and proliferation, formation of metastases, resistance to therapy  and poorer survival , . However, no data are yet available on the relation between DDX3 and Oxibendazole hypoxia in human breast cancer, or any other human tumors specimens. Therefore, we set out to correlate expression of DDX3 and HIF-1 in a large set of human invasive breast cancers. Furthermore, we correlated DDX3 expression to expression of various other proteins upstream of HIF-1 like EGFR , HER2 , Akt1C, p53C, COMMD1 , , FER kinase , PIN1  and FOXO4 . Also we assessed proteins downstream of HIF-1 such as ER ,  Transferrin receptor (TfR) , FOXO3A  and Notch1 , . Rabbit polyclonal to INPP5K Finally, we included proteins that have been associated with HIF-1 without clear functional relationship like E-cadherin , p21 , c-Met ,  and p27 . Materials and Methods Patients Representative paraffin embedded tissue blocks of 422 breast cancer patients collected between 2004 and 2007 were taken from the archive of the Department of Pathology of the University Medical Centre in Utrecht and routinely processed to four tissue microarrays (TMA) as described before , . Clinicopathological data including tumor stage, histological data (type, grade, mitotic index (MAI), estrogen receptor alpha (ER) and human epidermal growth factor receptor 2 (HER2)) status was collected from patient files (Table 1). Protein expression data by immunohistochemistry of HIF-1, FOXO3A, FOXO4, PIN1, Akt1, COMMD1, p53, p21, p27, EGFR, E-cadherin, GLUT1 and CAIX was derived from previous studies, , C. Table 1 Patient characteristics. (422)missing(%)Low (%)High (%)ORp valuea ORp valueb (%)Low (%)High (%)ORp valuea ORp valueb (%)Low (%)High (%)ORp valuea ORp valueb results pointing to regulation of DDX3 by HIF-1. We indeed show a positive correlation between HIF-1 and DDX3 overexpression in a large.