Modulation of Drug Resistance in Ovarian Adenocarcinoma by Enhancing Intracellular Ceramide Using Tamoxifen-Loaded Biodegradable Polymeric Nanoparticles Harikrishna Devalapally, 1 Zhenfeng Duan, 2 Michael V. Seiden, 2 and Mansoor M. Amiji 1 Abstract Purpose: To modulate intracellular ceramide levels and lower the apoptotic threshold in multidrug-resistant ovarian adenocarcinoma, we have examined the efficacy and preliminary safety of tamoxifen coadministration with paclitaxel in biodegradable poly(ethylene oxide)^ modified poly(epsilon-caprolactone) (PEO-PCL) nanoparticles. Experimental Design: In vitro cytotoxicity and proapoptotic activity of paclitaxel and tamoxifen, either as single agent or in combination, was examined in wild-type (SKOV3) and MDR-1 ^ positive (SKOV3 TR ) human ovarian adenocarcinoma cells. Subcutaneous SKOV3 and SKOV3 TR xenografts were established in female nu/nu mice, and this model was used to evaluate the antitumor efficacy and preliminary safety. Paclitaxel (20 mg/kg) and tamoxifen (70 mg/kg) were administered i.v. either as a single agent or in combination in aqueous solution and in PEO-PCL nanoparticles. Results: In vitro cytotoxicity results showed that administration of paclitaxel and tamoxifen in combination lowered the IC 50 of paclitaxel by 10-fold in SKOV3 cells and by >3-fold in SKOV3 TR cells. The combination paclitaxel/tamoxifen co-therapy showed even more pronounced effect when administered in nanoparticle formulations. Upon i.v. administration of paclitaxel/tamoxifen combination in PEO-PCL nanoparticle formulations, significant enhancement in antitumor efficacy was observed. Furthermore, the combination paclitaxel/tamoxifen therapy did not induce any acute toxicity as measured by body weight changes, blood cell counts, and hepatotoxicity. Conclusions: The results of this study show that combination of paclitaxel and tamoxifen in biodegradable PEO-PCL nanoparticles can serve as an effective clinically translatable strategy to overcome multidrug resistance in ovarian cancer. Ovarian cancer is the most common gynecologic malignancy in women with more than 23,000 cases per year in the United States. Despite aggressive chemotherapy, the mortality rate of ovarian cancer remains relatively high (1). This is due to initial diagnosis of the disease at late stages, when there is significant dissemina- tion in organs of the peritoneal cavity and failure of therapy due to intrinsic and acquired resistance development (2). Taxanes (e.g., paclitaxel) and platinum drugs (e.g., cisplatin and carboplatin) are the first-line choice for chemotherapy in ovarian cancer (3). Unfortunately, paclitaxel resistance is seen in >70% of patients at the time of initial diagnosis and almost all upon relapse (4). Acquisition of drug resistance to a multitude of chemotherapeutic drugs occurs due to poor availability of systemically administered drugs and phenotypic alterations in cancer cells due to microenvironmental selection pressures (5, 6). The expression of MDR-1 gene in tumor multidrug resistance (MDR) leads to the presence of membrane-bound ATP-binding cassette family of transporters, including P-glycoprotein (7). Additional phenotypic alternations in MDR leads to enhanced DNA repair, rapid metabolism of drugs by cytochrome P-450 and glutathione S -transferase enzymes, and alteration in the apoptotic signaling cascade (8, 9). Recent studies have shown that intracellular ceramide, a secondary lipid messenger, levels in MDR cells are significantly altered due to inhibition of transport from the endoplasmic reticulum and overexpression of ceramide-metabolizing enzymes, such as glucosylceramide synthase (GCS; refs. 10, 11). Lower levels of intracellular ceramide and correspondingly higher levels of GCS have been shown in a variety of MDR models. Using different MDR- reversing agents, such as verapamil (a calcium channel blocker; ref. 12), quinidine and other antiarrhythmics (13), cyclospor- ine A (an immunosuppressive agent; ref. 14), and tamoxifen (the selective estrogen response modifier; ref. 12, 15), Cabot et al. have observed that GCS inhibition can be a very effective strategy to overcome tumor MDR (16, 17). Although there are a number of GCS inhibitors, including the threo- 1-phenyl-2-decanoylamino-3-morpholino-1-propanol and Cancer Therapy: Preclinical Authors’ Affiliations: 1 Department of Pharmaceutical Sciences, School of Pharmacy, Northeastern University; 2 Department of Hematology and Oncology, Massachusetts General Hospital, Boston, Massachusetts Received 11/25/07; revised 12/31/07; accepted 1/21/08. Grant support: Nanotechnology Platform Partnership grant R01-CA119617 from National Cancer Institute of NIH. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Requests for reprints: Mansoor M. Amiji, Department of Pharmaceutical Sciences, School of Pharmacy, Northeastern University, 360 Huntington Avenue, Boston MA 02115. Phone: 617-373-3137; Fax: 617-373-8886; E-mail: m.amiji@ neu.edu. F 2008 American Association for Cancer Research. doi:10.1158/1078-0432.CCR-07-4973 www.aacrjournals.org Clin Cancer Res 2008;14(10) May 15, 2008 3193