01, and ***P<0. effective doses and IC50 values. Percentages of apoptotic cells were evaluated by Annexin/PI staining and mRNA levels of OPN isoforms and AKT/ VEGF-A and VEGF-C/ STAT3/ -catenin/ CXCR4/ IL-6/ KDR gene expression were investigated by Real Time-PCR method. Moreover, to confirm OPN gene expression data, we investigated the effect of simvastatin and OPN siRNA as an OPN inhibitor around the cell proliferation and induction of apoptosis in the indicated cell lines. Our data display that Ara-c (2M and 1M in KG-1 and U937 cell lines respectively), CUR (40M in both cell lines), and also their combination significantly increased the percentage of apoptotic cells. Moreover, the mRNA level of OPN isoforms were down regulated in the KG-1and U937 cell lines treated with Ara-c while, upregulated in KG-1and U937 cell lines treated with CUR and its combination. Our results suggest that despite anti-angiogenesis effects of CUR, AML cells probably evade from anti-angiogenesis effects of CUR via induction of OPN b and c isoform and related molecular pathways. MELK-IN-1 Keywords: Osteopontin, anti-angiogenesis, chemoresistance, acute myeloid leukemia Introduction Acute Myeloid Leukemia (AML), is one of the most common hematologic disorders that, described by the prevented homeostatic mechanisms of normal hematopoietic stem cells (Shahrabi et al., 2016; Zahedpanah et al., 2016). Treatment for AML has comprised a combination of Cytarabine (Ara-c), an anthracycline (often daunorubicin) or anthracycline mitoxantrone (Bishop, 1997). However, 40 to 50% of AML patients achieve complete remission after intensive chemotherapy; there is a widespread variation in the incidence and recurrence of the disease (Kavianpour et al., 2016). Curcumin (CUR) is the major extracted component of Curry family (Huang et al., 1994; Bailly et al., 1997; Rao et al., 2011; Mohammadi et al., 2017c). In vitro studies have exhibited that CUR specifically hinders the development of tumor cells as well as MELK-IN-1 induction of cell apoptosis in a dose-dependent manner (Menon et al., 1995; Jiang et al., 1996; Wu et al., 2000). It is recommended that CUR has an exceptionally developing prospect in antitumor activities. In spite of the fact that CUR instigates apoptosis in the flexibility of AML MELK-IN-1 cell lines, cytotoxic impacts of MELK-IN-1 CUR in AMLs remain indistinct (Mohammadi et al., 2016b; Mohammadi et al., 2017a). Osteopontin (OPN) is usually a glycoprotein and overexpressed in many cancers (Vejda et al., 2005; Rangel et al., 2008). The association of OPN, with different cancers and distinct stages of disease progression, suggests that it is a viable target for therapeutic interposition (Mi et al., 2009; Dai et al., 2010; Mohammadi et al., 2017c). In spite of the knowledge and understanding of OPN in soft tissue tumors, there is little information in connection with OPN in leukemia (Zahedpanah et al., 2016). Recent studies have shown that this oncogenic roles of OPN, including excitation of cell proliferation, invasion and migration might be regulated through different OPN isoforms such as OPN-a, Rabbit Polyclonal to SF1 OPN-b and OPN-c (Liu et al., 2004; Flamant et al., 2005; Nilsson et al., 2005; Mirza et al., 2008; Powell et al., 2009; Zduniak et al., 2015). Although many studies have been conducted on the effect of OPN in solid tumors, MELK-IN-1 but not addressed, the effect of different isoforms of OPN in the hematologic malignancies (Philip et al., 2001; Philip and Kundu, 2003; Rangel et al., 2008; Shevde and Samant, 2014). Our previous study revealed that upregulation of OPN-b and c in AML cells were concurrently associated with the upregulation of AKT/VEGF/CXCR4/STAT3/ IL-6 genes expression as a part of molecular loop involved in angiogenesis (Mirzaei et al., 2017). Based on the critical role of CUR in the suppression of angiogenesis in cancer cells (Ding et al., 2014; Huang et al., 2015), it seems affordable to hypothesize that combination of CUR with conventional AML.