Liposomal squalenoyl-gemcitabine: formulation, characterization and anticancer activity evaluation

A new prodrug of gemcitabine, based on the covalent coupling of squalene to gemcitabine (GemSQ), has been designed to enhance the anticancer activity of gemcitabine, a nucleoside analogue active against a wide variety of tumors. In the present study, the feasibility of encapsulating GemSQ into liposomes either PEGylated or non-PEGylated has been investigated. The in vivo anticancer activity of these formulations has been tested on subcutaneous grafted L1210wt leukemia model and compared to that of free gemcitabine. The liposomal GemSQ appears to be a potential delivery system for the effective treatment of tumors.

Squalenoyl nucleoside monophosphate nanoassemblies: new prodrug strategy for the delivery of nucleotide analogues

4-(N)-1,1',2-trisnor-squalenoyldideoxycytidine monophosphate (SQddC-MP) and 4-(N)-1,1',2-trisnor-squalenoylgemcitabine monophosphate (SQdFdC-MP) were synthesized using phosphoramidite chemistry. These amphiphilic molecules self-assembled to about hundred nanometers size nanoassemblies in aqueous medium. Nanoassemblies of SQddC-MP displayed significant anti-HIV activity whereas SQdFdC-MP nanoassemblies displayed promising anticancer activity on leukemia cells. These results suggested that squalene conjugate of negatively charged nucleotide analogues efficiently penetrated within cells. Thus, we propose a new prodrug strategy for improved delivery of nucleoside analogues to ameliorate their biological efficacy.

Aspirin inhibits proliferation of gemcitabine-resistant human pancreatic cancer cells and augments gemcitabine-induced cytotoxicity

AIM

To investigate whether aspirin is able to augment gemcitabine-induced cytotoxicity in human pancreatic cancer cells.

METHODS

Two gemcitabine-insensitive human pancreatic cancer cell lines, PANC-1 and Capan-1, were used. Cells were treated with either aspirin or gemcitabine alone or both of them. Cell growth and apoptosis were determined by MTT assay, Annexin V or Hoechest 33258 staining. Cell cycle distribution was examined by flow cytometry. Western blot with specific phosphorylated protein antibodies was used to detect the activation of protein kinase. RT-PCR and Western blot were applied to assess the transcription and protein level for cyclin D1 and Bcl-2.

RESULTS

Aspirin alone significantly inhibits the proliferation of PANC-1 cells by causing cell cycle arrest at G(1) phase. Aspirin potentiates the anti-survival effect of gemcitabine as well as its pro-apoptotic effect in PANC-1 cells, although aspirin per se does not trigger apoptosis. Aspirin inhibits GSK-3beta activation and suppresses the expression of its downstream gene products (cyclin D1 and Bcl-2), which are implicated in proliferation, survival and chemoresistance of pancreatic cancer. The effects of aspirin on Capan-1, were similar to that on PANC-1.

CONCLUSION

Our results suggest that aspirin inhibits the proliferation of gemcitabine-resistant pancreatic cancer cells and augments the antisurvival effect of gemcitabine, probably by suppressing the activity of GSK-3beta and its downstream gene products.

Squalene: A natural triterpene for use in disease management and therapy

Squalene is a natural lipid belonging to the terpenoid family and a precursor of cholesterol biosynthesis. It is synthesized in humans and also in a wide array of organisms and substances, from sharks to olives and even bran, among others. Because of its significant dietary benefits, biocompatibility, inertness, and other advantageous properties, squalene is extensively used as an excipient in pharmaceutical formulations for disease management and therapy. In addition, squalene acts as a protective agent and has been shown to decrease chemotherapy-induced side-effects. Moreover, squalene alone exhibits chemopreventive activity. Although it is a weak inhibitor of tumor cell proliferation, it contributes either directly or indirectly to the treatment of cancer due to its potentiation effect. In addition, squalene enhances the immune response to various associated antigens, and it is therefore being investigated for vaccine delivery applications. Since this triterpene is well absorbed orally, it has been used to improve the oral delivery of therapeutic molecules. All of these qualities have rendered squalene a potentially interesting excipient for pharmaceutical applications, especially for the delivery of vaccines, drugs, genes, and other biological substances. This paper is the first review of its kind and offers greater insight into squalene's direct or indirect contribution to disease management and therapy.

Anticancer efficacy of squalenoyl gemcitabine nanomedicine on 60 human tumor cell panel and on experimental tumor

Gemcitabine (2',2'-difluorodeoxyribofuranosylcytosine) is an anticancer nucleoside analogue active against a wide variety of solid tumors. However, following intravenous administration, this drug is rapidly inactivated by enzymatic deamination and displays a short biological half-life necessitating the administration of high doses leading also to unwanted side effects. To overcome these drawbacks and to improve the therapeutic index of gemcitabine, we have recently developed the concept of squalenoylation which consisted in the bioconjugation of gemcitabine with squalene, a natural lipid. In our preliminary studies, we have shown that this bioconjugate (SQgem) self-organized in water as nanoassemblies with considerable resistance to deamination and significantly higher anticancer activity compared with gemcitabine in an intravenously grafted tumor model in mice. To further establish the candidature of this nanomedicine for clinical trials, in this communication we have tested the preclinical efficacy of squalenoyl gemcitabine nanomedicine on several human tumor cell lines and on the subcutaneously grafted experimental L1210 murine tumor in mice. SQgem nanomedicine displayed an efficient cytotoxicity against a variety of human tumor cell lines in the 60 human tumor cell panel. In vivo, following intravenous administration, SQgem nanomedicine displayed a superior anticancer activity against subcutaneous L1210 tumor, comparatively to gemcitabine. The molecular mechanism behind the anticancer efficacy of SQgem has been investigated by flow cytometry analysis and protein expression profiling of L1210 wt cells treated in vitro with the squalenoyl gemcitabine bioconjugate. It was found that this nanomedicine arrested the cell cycle in G2/M, characterized by an increased cyclin A and cyclin E expression, and activation of caspase-3 and the cleavage of poly(ADP-ribose) polymerase with an increase of cytochrome C level. Taken together, these results suggest that the cell kill by this nanomedicine occurred through mitochondrial apoptotic triggered pathway, similarly to that of gemcitabine free.

Nanomedicine for the management of lung and blood diseases

Nanotechnology provides a broad range of opportunities to develop new solutions for clinical problems. For the pulmonary field, nanotechnology promises better delivery of drugs and nucleic acid-based therapeutics to disease sites. Administration of therapeutics via inhalation provides the opportunity for direct delivery to the lung epithelium, the lining of the respiratory tract. By appropriate selection of particle size, deep lung delivery can be obtained with control of phagocytic uptake, the removal of particles by resident macrophages. Nanotechnology can also help in pulmonary therapies administered by intravenous and oral routes through targeting specific cell types and controlling bioavailability and release kinetics. In the hematology field, nanotechnology can counter multiple drug resistance in leukemia by blocking drug efflux from cancer cells, and provide effective delivery of siRNA into lymphocytes to block apoptosis in sepsis. Controlling the surface properties of materials on devices such as valves and stents promises improved biocompatibility by inhibition of thrombosis, the formation of blood clots, and regulating cell adhesion and activation. Nanoparticle-based thrombolytic agents have the potential to improve the effectiveness of clot removal. Treatment of both lung and blood diseases is also likely to benefit from nano-scaffold-based methods for controlling the differentiation and proliferation of stem and progenitor cells.

Squalenoylation favorably modifies the in vivo pharmacokinetics and biodistribution of gemcitabine in mice

Gemcitabine (2',2'-difluorodeoxyribofuranosylcytosine; dFdC) is an anticancer nucleoside analog active against wide variety of solid tumors. However, this compound is rapidly inactivated by enzymatic deamination and can also induce drug resistance. To overcome the above drawbacks, we recently designed a new squalenoyl nanomedicine of dFdC [4-N-trisnorsqualenoyl-gemcitabine (SQdFdC)] by covalently coupling gemcitabine with the 1,1',2-trisnorsqualenic acid; the resultant nanomedicine displayed impressively greater anticancer activity compared with the parent drug in an experimental murine model. In the present study, we report that SQdFdC nanoassemblies triggered controlled and prolonged release of dFdC and displayed considerably greater t(1/2) (approximately 3.9-fold), mean residence time (approximately 7.5-fold) compared with the dFdC administered as a free drug in mice. It was also observed that the linkage of gemcitabine to the 1,1',2-trisnorsqualenic acid noticeably delayed the metabolism of dFdC into its inactive difluorodeoxyuridine (dFdU) metabolite, compared with dFdC. Additionally, the elimination of SQdFdC nanoassemblies was considerably lower compared with free dFdC, as indicated by lower radioactivity found in urine and kidneys, in accordance with the plasmatic concentrations of dFdU. SQdFdC nanoassemblies also underwent considerably higher distribution to the organs of the reticuloendothelial system, such as spleen and liver (p < 0.05), both after single- or multiple-dose administration schedule. Herein, this paper brings comprehensive pharmacokinetic and biodistribution insights that may explain the previously observed greater efficacy of SQdFdC nanoassemblies against experimental leukemia.