Liposomal formulation of a methotrexate lipophilic prodrug: assessment in tumor cells and mouse T-cell leukemic lymphoma.

In a previous study, a formulation of methotrexate (MTX) incorporated in the lipid bilayer of 100-nm liposomes in the form of diglyceride ester (MTX-DG, lipophilic prodrug) was developed. In this study, first, the interactions of MTX-DG liposomes with various human and mouse tumor cell lines were studied using fluorescence techniques. The liposomes composed of egg phosphatidylcholine (PC)/yeast phosphatidylinositol/MTX-DG, 8:1:1 by mol, were labeled with fluorescent analogs of PC and MTX-DG. Carcinoma cells accumulated 5 times more MTX-DG liposomes than the empty liposomes. Studies on inhibitors of liposome uptake and processing by cells demonstrated that the formulation used multiple mechanisms to deliver the prodrug inside the cell. According to the data from the present study, undamaged liposomes fuse with the cell membrane only 1.5-2 hours after binding to the cell surface, and then, the components of liposomal bilayer enter the cell separately. The study on the time course of plasma concentration in mice showed that the area under the curve of MTX generated upon intravenous injection of MTX-DG liposomes exceeded that of intact MTX 2.5-fold. These data suggested the advantage of using liposomal formulation to treat systemic manifestation of hematological malignancies. Indeed, the administration of MTX-DG liposomes to recipient mice bearing T-cell leukemic lymphoma using a dose-sparing regimen resulted in lower toxicity and retarded lymphoma growth rate as compared with MTX.

Inhibitor of vasculogenic mimicry restores sensitivity of resistant melanoma cells to DNA-damaging agents.

The increasing incidence of melanoma makes this cancer an important public health problem. Therapeutic resistance is still a major obstacle to the therapy of patients with metastatic melanomas. The aim of this study was to develop the melanoma cell line resistant to DNA-alkylating agents and to elucidate the mechanisms involved in acquired drug resistance. We established a unique melanoma subline Mel MeR resistant to DNA-alkylating drug aranoza by continuous stepwise selection of the Mel Me/WT cell line with increasing concentrations of this drug. Mel MeR cells were also cross-resistant to streptozotocin or cisplatin. Here, we show that aranoza-resistant melanoma cells modulate the ABC transporter activity, upregulate the expression of PRAME, adopt a vascular-related phenotype and engage in vasculogenic mimicry. LCS1269, a vasculogenic mimicry low-molecular-weight inhibitor, reverses the sensitivity of resistant melanoma cells to DNA-damaging agents. In this study, we provide experimental evidence that LCS1269 might be considered as a new potential anticancer agent capable of overcoming multidrug resistance for DNA-damaging agents in melanoma.