Targeted delivery of nucleic acids into xenograft tumors mediated by novel folate-equipped liposomes

Folate receptors (FR) are cellular markers highly expressed in various cancer cells. Here, we report on the synthesis of a novel folate-containing lipoconjugate (FC) built of 1,2-di-O-ditetradecyl-rac-glycerol and folic acid connected via a PEG spacer, and the evaluation of the FC as a targeting component of liposomal formulations for nucleic acid (NA) delivery into FR expressing tumor cells. FR-targeting liposomes, based on polycationic lipid 1,26-bis(cholest-5-en-3β-yloxycarbonylamino)-7,11,16,20-tetraazahexacosan tetrahydrochloride (2X3), lipid helper dioleoylphosphatidylethanolamine (DOPE) and novel FC, formed small compact particles in solution with diameters of 60 ± 22 nm, and were not toxic to cells. Complexes of NAs with the liposomes were prepared at various nitrogen to phosphate ratios (N/P) to optimize liposome/cell interactions. We showed that FR-mediated delivery of different nucleic acids mediated by 2X3-DOPE/FC liposomes occurs in vitro at low N/P (1/1 and 2/1); under these conditions FC-containing liposomes display 3-4-fold higher transfection efficiency in comparison with conventional formulation. Lipoplexes formed at N/P 1/1 by targeted liposomes and cargo (Cy7-labeled siRNA targeting MDR1 mRNA) in vivo efficiently accumulate in tumor (∼15-18% of total amount), and kidneys (71%), and were retained there for more than 24 h, causing efficient downregulation of p-glycoprotein expression (to 40% of control) in tumors. Thus, FC containing liposomes provide effective targeted delivery of nucleic acids into tumor cells in vitro and in xenograft tumors in vivo.

Structure-transfection activity relationships in a series of novel cationic lipids with heterocyclic head-groups

Cationic liposomes are promising candidates for the delivery of various therapeutic nucleic acids. Here, we report a convenient synthesis of carbamate-type cationic lipids with various hydrophobic domains (tetradecanol, dialkylglycerol, cholesterol) and positively charged head-groups (pyridinium, N-methylimidazolium, N-methylmorpholinium) and data on the structure-transfection activity relationships. It was found that single-chain lipids possess high surface activity, which correlates with high cytotoxicity due to their ability to disrupt the cellular membrane by combined hydrophobic and electrostatic interactions. Liposomes containing these lipids also display high cytotoxicity with respect to all cell lines. Irrespective of chemical structures, all cationic lipids form liposomes with similar sizes and surface potentials. The characteristics of complexes composed of cationic liposomes and nucleic acids depend mostly on the type of nucleic acid and P/N ratios. In the case of oligodeoxyribonucleotide delivery, the transfection activity depends on the type of cationic head-group regardless of the type of hydrophobic domain: all types of cationic liposomes mediate efficient oligonucleotide transfer into 80-90% of the eukaryotic cells, and liposomes based on lipids with N-methylmorpholinium cationic head-group display the highest transfection activity. In the case of plasmid DNA and siRNA, the type of hydrophobic domain determines the transfection activity: liposomes composed of cholesterol-based lipids were the most efficient in DNA transfer, while liposomes containing glycerol-based lipids exhibited reasonable activity in siRNA delivery under serum-free conditions.

[Synthesis of positively charged galactosurfactants]

An approach to synthesis of cationic carbohydrate surfactants with potential antimicrobial or transfected activities is described.

Novel cholesterol-based cationic lipids for gene delivery

Gene therapy based on gene delivery is a promising strategy for the treatment of human disease. Here we present data on structure/biological activity of new biodegradable cholesterol-based cationic lipids with various heterocyclic cationic head groups and linker types. Enhanced accumulation of nucleic acids in the cells mediated by the lipids was demonstrated by fluorescent microscopy and flow cytometry. Light scattering and atomic force microscopy were used to find structure/transfection activity correlations for the lipids. We found that the ability of the lipids to stimulate intracellular accumulation of the oligodeoxyribonucleotides and plasmid DNA correlates well with their ability to form in solution lipid/NA complexes of sizes that do not exceed 100 nm. Screening of the lipids revealed the most promising transfection agents both in terms of low toxicity and efficient delivery: cholesterol-based lipids with positively charged pyridine and methyl imidazole head groups and either the ester or carbamate linker.

[Positively charged acyl derivatives of carbohydrates as promising transfection agents]

A convenient approach to the synthesis of mono- and polycationic glycolipid amphiphiles is suggested. The compounds obtained can be used for study of the structure-activity relationship and determination of the effect of hydrophobic and cationic domains on transfection efficiency.

[The synthesis of a glucosyldiglyceride for constructing pH-sensitive liposomes]

A glucosyldiglyceride containing residues of 11-aminoundecanoic acid was synthesized for constructing pH-sensitive liposomes.

[Transfection of eucaryotic cells using cytochrome CYP450 2B6 gene: sensitivity to cyclophosphamide]

Sensitivity of 293 human epithelial kidney cells transfected by human cytochrome CYP450 gene to cyclophosphamide was investigated. Transfection was carried out by plasmid DNA containing CYP2B6 gene complexed with cationic liposomes. Liposomes were prepared from mixture of cationic lipids and cholesterol at different molar ratios. Experimental protocol included the following steps: transfection of epithelial kidney cells by complexes of plasmid DNA-cationic liposomes, clone selection in the medium with antibiotic Geneticin G418, selected clone harvesting and their treatment by cyclophosphamide as following cytotoxicity evaluation. It was shown that addition of 0.25 mM of cyclophosphamide resulted in death of 40-45% transfected cell population.

[Synthesis of cationic glucosyldiglycerides]

A series of glucosyl dialkylglycerols with the pyridinium, N-morpholinium, and N-methylimidazolium polar heads were synthesized by quaternization of the corresponding bases with the acetylated glucosyl diglyceride 6-O-methane- and 6-O-toluenesulfonates. The resulting compounds were designed for the use in gene delivery systems.

[Assay of adenine nucleotide level in platelet storage pool for evaluation of the course of hemoblastosis]

The content of adenine nucleotides (ATP, ADP) was studied in dense granules of platelets in hemoblastosis to estimate the character of the pathological process course. Varying biochemical defects were observed at the levels of ATP and ADP depending on the severity of the pathological process in chronic myeloid leukemia, acute lymphoblastic leukemia, acute myeloblastic and acute myelo-monoblastic leukemias. Adenine nucleotide values can be used for the diagnosis of varying stages of the above diseases, for the evaluation of anomalous platelets and characterization of the adequacy of the bone marrow hemopoiesis.

[Importance of studying the level of platelet adenine nucleotide levels in various phases of chronic myeloleukoses]

Content of adenine nucleotides was studied in various compartments of blood platelets obtained from donors and patients with chronic myeloleukosis at various steps of the disease. Dissimilar biochemical defect was found in content of ATP and ADP, which varied in thrombocyte storage granules depending on severity of the disease. The data on adenine nucleotides content may be used for diagnosis of various steps of chronic myeloleukosis, for detection of thrombocytes anomaly and for evaluation of the state of medullary hemopoiesis.

[The use of a panel of monoclonal antibodies for immunologic prognosis of recurrence of acute lymphoblastic leukemia]

A method for early immunological prognosis of acute lymphoblastic leukemia (ALL) relapses has been presented. It is based on the dynamic phenotyping of lymphoid blood cells from the patients during remission by the indirect immunofluorescence test using a specially composed panel with monoclonal antibodies (MCA) to differentiation antigens of early lymphopoiesis stages. The panel composed for monitoring the population of leukemic cells during remission, contained 6 MCA selected from 40 MCA samples with the known specificity, basing on the principle of the highest reactivity with lymphoblasts from patients, and minimal positive reactions with lymphocytes from normal subjects. Blood mononuclear cells from 10 patients with ALL were subjected to immunophenotyping in the panel with MCA during remission, before each course of polychemotherapy. A retrospective analysis of the immunophenotyping data has shown that populations of lymphoid cells carrying antigens of early differentiation stages in amounts significantly exceeding the limits of the standard values (M +/- 3 delta) appear among blood lymphocytes, practically, in all the patients, 1-4 months before the relapse of ALL has been proved.

[The prognostic significance of parameters of bone marrow blast cell proliferation in patients with acute leukemia]

Percentage of bone marrow blasts in S-phase (S%) in acute leukemia patients was evaluated by 3H-thymidine autoradiography or Feulgen cytophotometry at the initial acute period before chemotherapy. In acute lymphoid leukemia (ALL) patients who showed complete remission (CR) S% was 8.6 +/- 1.8% versus 2.1 +/- 0.4% in cases without CR (p less than 0.001). In acute non-lymphoid leukemia (ANLL) the corresponding values were 11.4 +/- 1.4% and 8.3 +/- 1.8%, p greater than 0.05. A negative correlation was observed between S% and the duration of CR in ALL: S% was 13.0 +/- 0.7% in CR, more than 12 months, and 6.9 +/- 1.1% in CR less than 12 months (p less than 0.01). The duration of life also correlated negatively with S%. In ALL S% was 9.5 +/- 1.5% for patients with survival less than 12 months versus 6.2 +/- 0.6% for patients with survival more than 12 months (p less than 0.05). In ANLL the difference (10.3 +/- 1.6% and 6.8 +/- 1.2, respectively) was not significant (p greater than 0.05). Thus in ALL the correlations between S% and the probability to achieve CR is positive, while the correlations between S% and survival and remission duration are negative. In ANLL these correlations are statistically insignificant.