I. V. Alekseenko

Therapeutic properties of a vector carrying the HSV thymidine kinase and GM-CSF genes and delivered as a complex with a cationic copolymer.

BackgroundGene-directed enzyme prodrug therapy (GDEPT) represents a technology to improve drug selectivity for cancer cells. It consists of delivery into tumor cells of a suicide gene responsible for in situ conversion of a prodrug into cytotoxic metabolites. Major limitations of GDEPT that hinder its clinical application include inefficient delivery into cancer cells and poor prodrug activation by suicide enzymes. We tried to overcome these constraints through a combination of suicide gene therapy with immunomodulating therapy. Viral vectors dominate in present-day GDEPT clinical trials due to efficient transfection and production of therapeutic genes. However, safety concerns associated with severe immune and inflammatory responses as well as high cost of the production of therapeutic viruses can limit therapeutic use of virus-based therapeutics. We tried to overcome this problem by using a simple nonviral delivery system.MethodsWe studied the antitumor efficacy of a PEI (polyethylenimine)-PEG (polyethylene glycol) copolymer carrying the HSVtk gene combined in one vector with granulocyte–macrophage colony-stimulating factor (GM-CSF) cDNA. The system HSVtk-GM-CSF/PEI-PEG was tested in vitro in various mouse and human cell lines, ex vivo and in vivo using mouse models.ResultsWe showed that the HSVtk-GM-CSF/PEI-PEG system effectively inhibited the growth of transplanted human and mouse tumors, suppressed metastasis and increased animal lifespan.ConclusionsWe demonstrated that appreciable tumor shrinkage and metastasis inhibition could be achieved with a simple and low toxic chemical carrier – a PEI-PEG copolymer. Our data indicate that combined suicide and cytokine gene therapy may provide a powerful approach for the treatment of solid tumors and their metastases.

Activity of the upstream component of tandem TERT/survivin promoters depends on features of the downstream component.

We spliced the promoters of the human telomerase and human survivin genes (PhTERT and PhSurv, respectively) widely used for gene therapy and known to have the broadest cancer type spectrum of activity. Two head-to-tail constructs were obtained: the PhTERT-PhSurv and PhSurv-PhTERT tandems. The splicing caused quantitative and qualitative changes in the promoter features. In both constructs, only the promoter proximal to the transcribed gene retained its ability to initiate transcription, whereas the distal promoter was silent, the phenomenon never reported before. However, the distal promoter modulated the activity of the proximal one by increasing its strength and causing an appearance of additional transcription start sites. We suggested that this suppression might be due to the presence of Sp1 transcription factor binding sites in both promoters and Sp1-bridges between these sites. Such Sp1-bridges might convert the tandem promoter linear DNA into a stem-loop structure. If localized inside the formed loop, the distal promoter could lose its ability to initiate transcription. To test this hypothesis, we constructed two modified double promoters, where the proximal PhSurv promoter was replaced either by a shortened variant of the survivin promoter (PhSurv269) or by the mouse survivin promoter. Both PhSurv substitutes were considerably shorter than PhSurv and had different numbers and/or positions of Sp1 sites. In modified tandems, transcription was initiated from both promoters. We also prepared two mutant forms of the PhSurv-PhTERT tandem with two or four Sp1 sites removed from the distal “long” PhSurv promoter. In the first case, the distal PhSurv promoter remained silent, whereas the removal of four Sp1 binding sites restored its activity. In the majority of studied cancer cell lines the efficiency of transcription from the hTERT-(shortened hSurv269) promoter tandem was markedly higher than from each constituent promoter. In normal lung fibroblast cells, the tandem promoter activity was considerably lower.

Bicistronic vector for combined expression of the HSVtk killer gene and cytokine GM-CSF gene in cancer cells.

174 Gene therapy is one of the most actively developed approaches for cancer treatment. There are several strategies to kill cancer cells, in particular: (a) suppres sion of oncogene function in a cancer cell, (b) destruc tion of cancer cells by a killer gene, and (c) stimulation of antitumor immunity. The last two strategies are most versatile because they can destroy cancer cells regardless of their type. The approach with the use of killer genes is based on the introduction into the can cer cell of genes encoding enzymes that are not typical of normal cells and can convert a compound that is nontoxic to normal cells in a toxin that causes selective destruction of cancer cells. One of the killer genes that are commonly used for this purpose is the gene encod ing the herpes simplex virus thymidine kinase (HSVtk). The HSVtk protein can phosphorylate the nucleoside analogue ganciclovir (GCV) to ganciclovir monophosphate. The latter is then phosphorylated by cellular kinases to form ganciclovir triphosphate, which is incorporated into a growing DNA strand dur ing cell division and terminates its synthesis, thereby ensuring the destruction of tumor cells [1]. Thus, can cer cells are destroyed selectively because normal rest ing cells do not synthesize DNA and do not incorpo rate the phosphorylated ganciclovir.

Genetic Regulatory Mechanisms of Evolution and Embryogenesis in a Distorting Mirror of Carcinogenesis

The article is an attempt to provide an overview of the relationships between the regulatory genetic mechanisms of three fundamental processes of biology, i.e., development, evolution, and cancer. The problems of the evolutionary inevitability of the onset of cancer, the evolutionarily developed systems for protecting the body against tumors, and the general systems of regulation used in evolution, development, and cancer are considered.

The cause of cancer mutations: Improvable bad life or inevitable stochastic replication errors?

Despite substantial progress in understanding the mechanisms of carcinogenesis and fighting oncology diseases, cancer mortality remains rather high. Therefore, there is a striving to reduce this mortality to the level determined by endogenous biological factors. The review analyzes the mutations that lead to cell malignant transformation and describes the contribution that self-renewal of adult tissues makes to tumorigenesis. Cancer progression is considered as a development of a complicated system where cells mutate, evolve, and are subject to selection. Cancer paradoxes are described in conclusion.

Are super-enhancers regulators of regulatory genes of development and cancer?

Enhancers make up a huge class of genome regulatory elements that play an important role in the formation and maintenance of specific patterns of gene transcriptional activity in all types of cells. In recent years, high-throughput methods for the genome-wide epigenetic analysis of chromatin have made it possible to identify structural and functional features of enhancers and their role in the spatial and functional organization of the genome and in the formation and maintenance of cell identity, as well as in the pathogenesis of certain diseases. Special attention has been focused on genome regions called super-enhancers, or stretch enhancers, which consist of clusters of elements with properties of classic enhancers. This review considers current data on specific properties of super-enhancers and their role in the formation of interconnected autoregulatory circuits with positive feedback that regulates the most important genes, the activity of which underlies the formation and maintenance of specialized cellular functions.

Fundamentally low reproducibility in molecular genetic cancer research

The review discusses the causes of multiple failures in cancer treatment, which might primarily result from the excessive variability of cancer genomes. They are capable of changing their spatial and temporal architecture during tumor development. The key reasons of irreproducibility of biomedical data and the presumable means for improvement of therapeutic results aiming at targeting the most stable tumor traits are suggested.

Fibroblast activation protein (FAP) as a possible target of an antitumor strategy

This review was devoted to the use of the universal component of tumoral stroma (fibroblast activation protein, FAP) as a target of the universal tumor therapy. A tumor is a coevolution system, which includes a microenvironment or reactive stroma differing from the normal tissue in its phenotypic and genotypic features. Cancer-associated fibroblasts (CAFs), which contain the typical marker FAP (serine proteinase with the enzymatic activity of dipeptidyl peptidase and endopeptidase), are important elements of the tumor microenvironment. According to the literature, more than 90% of tumors contain FAP-positive activated fibroblasts. FAP is virtually absent in normal tissues, but it is present in the embryonic and tumor tissues, which makes it a selective and universal target. In this work, basic approaches to affecting CAFs using FAP as a target are discussed. The use of FAP as a target provides an important advantage: its proteolytic activity can be used along with the protein-targeted agents. The main areas of development in the therapeutic use of FAP are discussed in this work.

Cytotoxicities of cytosine deaminase and herpes simplex virus thymidine kinase genes in melanoma cells are not affected by the promoter strength

The right choice of regulatory elements (promoters and enhancers) is essential for the preparation within cancer cells of the therapeutic genetic constructs aimed at the gene-programmed enzymatic transformation of non-toxic prodrugs into toxins. It is generally accepted that the efficiency of gene therapy constructions is dependent, in particular, on the strength of promoters regulating the expression of therapeutic genes. Using melanoma-specific promoters and gene enhancers of human melanoma inhibitory activity and mouse tyrosinase and therapeutic genes, namely, HSVtk encoding herpes simplex virus thymidine kinase and FCU1 encoding cytosine deaminase/uracil phosphoribosyltransferase hybrid protein gene, we demonstrated that the promoter strength was not critical for the development of cytotoxic effects. The cytotoxic activity of these genes was shown to be influenced by the concentration of the prodrug added.

A Universal Tumor-Specific Promoter for Cancer Gene Therapy

An artificial double tandem tumor-specific promoter based on survivin and human telomerase reverse transcriptase gene promoters was constructed. Studies in in vitro and ex vivo therapeutic systems showed that the designed promoter exhibits a high activity in tumor cells, which is comparable to the activity of the CMV constitutive promoter.