In vitro effect of liposome-incorporated valinomycin on growth and macromolecular synthesis of normal and ras-transformed 3T3 cells

Novel tumor-targeted liposomes comprised of an MDM2 antagonist plus proteasome inhibitor display anti-tumor activity in a xenograft model of bortezomib-resistant Waldenstrom macroglobulinemia

Targeted drug delivery remains an active area of investigation in hematologic cancers. We have previously reported on a novel nanoparticle formulation (D1X) that can encapsulate drugs within a liposome whose lipid bilayer contains dexamethasone, which serves as a targeting ligand for drug delivery to tumor cells that express glucocorticoid receptors. We tested the activity of D1X-encapsulated bortezomib (D1XB) in combination with D1X-encapsulated nutlin (D1XN) in B-lymphoma/Waldenstrom macroglobulinemia (WM) cells. WM cells treated with D1XB + D1XN experienced cell cycle arrest, ER stress and apoptosis. In mice xenografted with bortezomib-resistant WM cells, D1XB + D1XN treatment resulted in significantly lower tumor burden compared to vehicle or nonliposomal parent drugs. In vivo biodistribution studies showed minimal uptake of D1X-based drugs in normal mice tissues. Our studies demonstrate that highly targeted delivery of both bortezomib and nutlin encapsulated in D1X nanoparticles are cytotoxic to and delay in vivo growth of bortezomib-resistant WM cells.

Combination chemotherapy of human ovarian xenografts with intraperitoneal liposome-incorporated valinomycin and cis-diamminedichloroplatinum(II)

Intraperitoneal administration of liposomal valinomycin (MLV-VM) with cis-diamminedichloroplatinum(II) (cDDP) had significant antitumor activity against murine P388 leukemia and inhibited the growth of OVCAR-3 tumors in a nude mouse model of human ovarian cancer. This tumor is a teratoma originating in the ovary with pathogenesis and metastatic properties similar to those of human ovarian cancer. Drug was given to the mice once every 5 days for 4 doses beginning 1 day after i.p. implantation of 10(7) or 5 x 10(7) OVCAR-3 tumor cells. For P388 leukemia, drug was given i.p. once or on days 1 and 5 after tumor inoculation. Despite the use of low doses of MLV-VM, the antitumor activity of the combination [increase in life span (%T/C), 289%-294%] represents a 4-log cell kill over the additive effect of the two drugs, indicating a synergistic interaction between MLV-VM and cDDP. Likewise, low doses of the drug combination produced a synergistic interaction on human ovarian OVCAR-3 tumors, and tumor-free, long-term survivors were obtained. Combined therapy of liposome-incorporated valinomycin and cisplatin was well tolerated and produced no overlapping nephrotoxicity, although a decrease in liver enzyme markers (alkaline phosphatase and/or alkaline aminotransferase) with MLV-VM was observed. These results appear to suggest that MLV-VM with cDDP may have considerable potential for the treatment of ovarian cancer disseminated within the peritoneal cavity, although the frequency and sequence of drug administration may need to be improved.

Synergistic cytotoxic actions of cisplatin and liposomal valinomycin on human ovarian carcinoma cells

We have previously shown that the toxicity of valinomycin (VM), a membrane-active agent with antineoplastic activity, can be dramatically reduced with no loss of the antitumor efficacy of the drug by incorporating it into liposomes. In the present study, we investigated the interaction between cis-diamminedichloroplatinum(II) (CDDP) and VM in terms of in vitro cytotoxicity to human ovarian tumor cells. Using the MTT assay and analyzing the data using the median-effect principle, we showed that synergistic cytotoxic interactions exist between CDDP and VM in their liposomal form. The degree of cytotoxic synergism was influenced by the duration of drug exposure and the dose ratio. The cellular accumulation of platinum by ovarian cells at 37 degrees C was slightly higher after exposure to VM as compared with controls; however, it is not clear that this accounts for the cytotoxic synergism. These results suggest that the combination of liposomal VM and CDDP may have merit as a form of localized drug delivery for the treatment of ovarian cancer disseminated within the peritoneal space.