However, the disease becomes chemo-refractory within approximately two-years, and second-line treatment options do not provide significant survival advantage [2]. Thus, novel treatment approaches are needed to be investigated for this era. Retinoids include both natural and synthetic derivatives of vitamin A. In the cell, they act by binding nuclear receptors that function as retinoid-dependent transcriptional factors, including the RAR and RXR

receptors [3, 4]. All- find more trans retinoic acid (ATRA), a natural derivative of vitamin A, induces growth arrest, differentiation and cell death of different types of cancer cell lines in vitro [5, 6]. In the literature, there is a body of selleck evidence that ATRA enhances the cytotoxic effects of chemotherapeutic agents [7–10]. There are some encouraging data from preclinical trials that have demonstrated the efficacy of using retinoids and cytotoxics in combination check details [11–13]. Zoledronic acid, a third-generation bisphosphonate, inhibits osteoclastic resorptive activity partly through inhibition of farnesyl-diphosphate synthase and protein prenylation [14]. Though it is mainly

used for the treatment of cancer-induced bone disease, the promising findings coming from substantial amount of preclinical and early clinical evidence on the cytotoxic effect of zoledronic acid have led to several ongoing studies that will ascertain the benefit of zoledronic acid, itself, may act as a new antitumor agent in some human cancers [14, 15]. Latest trials have demonstrated that zoledronic acid also has diverse anti-tumor effects via multiple mechanisms [16, 17]. In preclinical models, bisphosphonates directly inhibit tumour growth and angiogenesis. Two recent clinical trials, ABCSG13 and Z/Zo-FAST have shown a disease-free survival

benefit with zoledronic ID-8 acid in women receiving adjuvant endocrine therapy [18, 19]. Thus, it has been discussed to be used in the extended adjuvant treatment of early breast cancer as a new, promising anti cancer drug. The wide spectrum toxic side effects of cytotoxic treatment as well as drug resistance occur to be important limitations of management of ovarian cancer, thus new treatment approaches are needed. Based on the knowledge of ATRA may work as enhancer of cytotoxic effect when added to other drugs, we investigated the possible additive/synergistic combination of ATRA with zoledronic acid in human ovarian cancer cell lines, OVCAR-3 and MDAH-2774. Since both of the agents have much more tolerable side effects as compared to conventional cytotoxic drugs, we searched for if this new combination might be a hope for elderly ovarian cancer patients. Ovarian cancer cell lines can potentially overcome the experimental limitations inherent in both the animal models of ovarian cancer and the primary cloning of human ovarian cancer specimens.