Possibility for Transcriptional Targeting of Cancer-Associated Fibroblasts-Limitations and Opportunities

Cancer-associated fibroblasts (CAF) are attractive therapeutic targets in the tumor microenvironment. The possibility of using CAFs as a source of therapeutic molecules is a challenging approach in gene therapy. This requires transcriptional targeting of transgene expression by cis-regulatory elements (CRE). Little is known about which CREs can provide selective transgene expression in CAFs. We hypothesized that the promoters of FAP, CXCL12, IGFBP2, CTGF, JAG1, SNAI1, and SPARC genes, the expression of whose is increased in CAFs, could be used for transcriptional targeting. Analysis of the transcription of the corresponding genes revealed that unique transcription in model CAFs was characteristic for the CXCL12 and FAP genes. However, none of the promoters in luciferase reporter constructs show selective activity in these fibroblasts. The CTGF, IGFBP2, JAG1, and SPARC promoters can provide higher transgene expression in fibroblasts than in cancer cells, but the nonspecific viral promoters CMV, SV40, and the recently studied universal PCNA promoter have the same features. The patterns of changes in activity of various promoters relative to each other observed for human cell lines were similar to the patterns of activity for the same promoters both in vivo and in vitro in mouse models. Our results reveal restrictions and features for CAF transcriptional targeting.

Enhanced Vector Design for Cancer Gene Therapy with Hierarchical Enhancement of Therapeutic Transgene Expression

A set of vectors for Cre recombinase-dependent expression of the hybrid suicidal FCU1 transgene was constructed, including a two-plasmid system wherein the FCU1 and Cre transgenes reside in separate vectors, and single-plasmid variants in which a single plasmid bears both transgenes. To improve the safety profile and specificity in cancer gene therapy applications, as well as to ensure stable propagation of plasmids in bacterial cells, the Cre/LoxP system components were optimized. A bicistronic vector with the Cre expression cassette placed between the LoxP sites unidirectionally with FCU1 cDNA resulted in higher therapeutic efficiency compared with the double-plasmid system in an enzyme-prodrug suicide cancer gene therapy scheme. Therefore, the feasibility of a single-plasmid approach in the development of cancer gene therapy with hierarchical enhancement of therapeutic transgene expression has been demonstrated.

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

BACKGROUND

Gene-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.

METHODS

We 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.

RESULTS

We 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.

CONCLUSIONS

We 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.

[Expression of sphingomyelin synthase 1 (SGMS1) gene varies in human lung and oesophagus cancer]

The investigation of molecular mechanisms contributing to cancer progression is the burning problem ofcurrent research. Considerable attention has been given to the study of gene expression in cancer cells. Sphingomyelin synthase 1 gene (SGMS1) is one of the genes whose expression can be altered in cancer. SMS1 enzyme, encoded by this gene, catalyzes the synthesis of sphingomyelin and diacylglycerol from phosphatidylcholine and ceramide. SMS1 may maintain the balance between cell death and survival by regulating the formation of the pro-apoptotic mediator ceramide and anti-apoptotic mediator diacylglycerol. In addition, the changes in sphingomyelin level and sphingomyelin synthase activity have been observed in cancers of many tissues. However the peculiarities of SGMS1 gene transcription have been insufficiently explored. In this work the expression of transcripts of SGMS1 has been investigated by the method of Real Time PCR in matched pairs of samples of human lung and oesophagus cancer and adjacent tissues without pathology. A significant decrease in SMS1 transcripts expression has been found in samples of human lung cancer. At the same time, in the samples of human oesophagus cancer and adjacent tissue, expression of SMS1 transcripts varies insignificantly: it is increased in 7 and decreased in 5 of 15 samples. The obtained results indicate that SGMS1 gene is differently expressed in cancers of different genesis.

Alterations in gene expression of proprotein convertases in human lung cancer have a limited number of scenarios

Proprotein convertases (PCs) is a protein family which includes nine highly specific subtilisin-like serine endopeptidases in mammals. The system of PCs is involved in carcinogenesis and levels of PC mRNAs alter in cancer, which suggests expression status of PCs as a possible marker for cancer typing and prognosis. The goal of this work was to assess the information value of expression profiling of PC genes. Quantitative polymerase chain reaction was used for the first time to analyze mRNA levels of all PC genes as well as matrix metalloproteinase genes MMP2 and MMP14, which are substrates of PCs, in 30 matched pairs of samples of human lung cancer tumor and adjacent tissues without pathology. Significant changes in the expression of PCs have been revealed in tumor tissues: increased FURIN mRNA level (p<0.00005) and decreased mRNA levels of PCSK2 (p<0.007), PCSK5 (p<0.0002), PCSK7 (p<0.002), PCSK9 (p<0.00008), and MBTPS1 (p<0.00004) as well as a tendency to increase in the level of PCSK1 mRNA. Four distinct groups of samples have been identified by cluster analysis of the expression patterns of PC genes in tumor vs. normal tissue. Three of these groups covering 80% of samples feature a strong elevation in the expression of a single gene in cancer: FURIN, PCSK1, or PCSK6. Thus, the changes in the expression of PC genes have a limited number of scenarios, which may reflect different pathways of tumor development and cryptic features of tumors. This finding allows to consider the mRNAs of PC genes as potentially important tumor markers.

Cathepsin D messenger RNA is downregulated in human lung cancer

OBJECTIVES

Lysosomal proteases cathepsins B and D (CB and CD) play a significant part in cancer progression. For many oncological diseases protein expression levels of CB and CD have been investigated and correlations with tumour characteristics revealed. Meanwhile, there is very little information concerning mRNA expression level.

METHODS

In the present work, data about mRNA levels of CB and CD in human lung cancer was obtained using reverse transcription followed by real-time polymerase chain reaction.

RESULTS

For the first time CD and CB mRNA in human lung cancer tumours was quantified. It was shown that CB and CD mRNA levels do not correlate with any tumour characteristics. However, in most analysed tumours, expression of CD mRNA was downregulated compared with adjacent normal tissue (p <0.0003).

CONCLUSIONS

The data obtained indicate CD mRNA as a potential lung cancer marker.

[Comparative analysis of herpes simplex virus thymidine kinase gene expression potentiation via HIV-1 Tat-TAR-system and cancer-specific promoters in p53(+) and p53(-) cells]

Tumor-specific promoters are predominantly active and ensure expression of the gene under control exclusively in cancer cells. However, a low activity of the promoters is an essential disadvantage for their therapy usage. To achieve a higher expression level of the therapeutic gene, herpes simplex virus thymidine kinase (HSV-tk), the Tat-TAR-system being utilized by HIV-1 for increasing own gene expression was developed. A potentiating activity of tat gene under control of two different cancer-specific gene (human survivin gene and human telomerase reverse transcriptase) promoters for increasing of the HSV-tk gene expression being regulated by TAR-element was evaluated, and activity of the cancer-specific promoters in the Tat-TAR-system was compared. Co-transfection of the cells with the both constructions led to the tat protein synthesis and its affect the HIV-1 TAR-element. An expression level of HSV-tk gene ensured by the both promoters in the binary system was close to that for strong non-specific cytomegalovirus (CMV) promoter. Enzymatic activity of HSV-tk protein in cells having both elements of Tat-TAR-system was two orders of magnitude higher than that in the cells transfected with HSV-tk gene under control of the cancer-specific promoter. Notably, the effect was independent of p53-status of transfected cells: HSV-tk expression level was almost the same in p53(+) and p53(-) cells. The obtained results show that system may be used for therapy of different cancer types both p53-defective and p53-positive ones inhibiting cancer-specific promoters activity.

Identification of some human genes oppositely regulated during esophageal squamous cell carcinoma formation and human embryonic esophagus development

Here we directly compared gene expression profiles in human esophageal squamous cell carcinomas and in human fetal esophagus development. We used the suppression subtractive hybridization technique to subtract cDNAs prepared from tumor and normal human esophageal samples. cDNA sequencing and reverse transcription polymerase chain reaction (RT-PCR) analysis of RNAs from human tumor and the normal esophagus revealed 10 differentially transcribed genes: CSTA, CRNN, CEACAM1, MAL, EMP1, ECRG2, and SPRR downregulated, and PLAUR, SFRP4, and secreted protein that is acidic and rich in cysteine upregulated in tumor tissue as compared with surrounding normal tissue. In turn, genes up- and downregulated in tumor tissue were down- and upregulated, respectively, during development from the fetal to adult esophagus. Thus, we demonstrated that, as reported for other tumors, gene transcriptional activation and/or suppression events in esophageal tumor progression were opposite to those observed during development from the fetal to adult esophagus. This tumor 'embryonization' supports the idea that stem or progenitor cells are implicated in esophageal cancer emergence.

[Increase of BIRC5 gene expression in non-small cell lung cancer and esophageal squamous cell carcinoma does not correlate with expression of genes SMAC/DIABLO and PML encoding its inhibitors]

Survivin (BIRC5) is one of the members of IAP-family apoptosis inhibitors. The BIRCS gene is expressed in most human embryonic tissues and malignant tumors but not in normal differentiated tissues of adult human. It was suggested that BIRC5 proteins inhibit apoptosis and play an essential role in tumorigenesis, makings surviving an attractive target for anticancer therapy. The mechanisms regulating level of survivin are not completely understood. It was supposed that natural inhibitors of survivin, namely SMAC and PML, play an important role in these processes. Using RT-PCR and immunoblotting we analyzed the transcription level of BIRC5, SMAC and PML genes and content of corresponding proteins in normal and tumor human tissues in non-small cell lung cancer and esophageal squamous cell carcinoma. It was demonstrated that BIRC5 is transcribed only in tumor tissues, whereas expression levels of SMAC and PML are the same in normal and tumor tissues. The contents of proteins correspond to levels of mRNA of the respective genes. Thus the increase of level of survivin in tumor tissues is not the result of decrease in content of its inhibitors SMAC and PML, as their content in tumor and normal cells is the same.

[Regulatory potential of S/MAR elements in transient expression]

S/MARs (scaffold/matrix attachment regions) are the DNA regions that are involved in the interaction with the nuclear matrix and are identified by in vitro methods. According to the available information, S/MARs possess an insulating activity, i.e., the ability to block the interaction between the enhancer and promoter in vivo, and are, probably, intact insulators or their fragments. Nevertheless, there is still no direct proof for this correspondence. To obtain additional information on the insulator activity of S/MARs, we selected five DNA fragments of different lengths and affinities for the nuclear matrix from the previously constructed library of S/MARs and tested their ability to serve as insulators. Two of five elements exhibited an insulator (enhancer-blocking) activity upon the transient transfection of CHO cells. None of the S/MARs displayed either promoter or enhancer/silencer activities in these cells.

Separation of monomerizing and lysozyme activities of destabilase from medicinal leech salivary gland secretion

Destabilase, endo-epsilon-(gamma-Glu)-Lys-isopeptidase, was prepared from the salivary gland secretion of the medicinal leech (Hirudo medicinalis). The secretion prepared by the known method of Rigbi et al. (1987) (secretion-K) lacks the destabilase-characteristic highly specific isopeptidase activity (the D-dimer-monomerizing activity) because of its degradation by proteolytic activity (the substrate of Glp-Ala-Ala-Leu-pNA) due to contamination with leech intestinal channel contents. Therefore, we have elaborated a new technique for preparation of a true leech secretion (secretion-I). This secretion is characterized by the complete absence of the leech intestinal channel contents and has no proteolytic activity. For the first time the destabilase-specific D-dimer-monomerizing and lysozyme activities were separated by fractionation of secretion-I by HPLC gel filtration through Superose S-12. For the purified destabilase preparation, these activities were separated by reversed-phase chromatography in an acetonitrile gradient (0-60%) in the presence of 0.1% trifluoroacetic acid. The monomerizing activity of destabilase is responsible for the ability of secretion-I to dissolve stabilized fibrin via isopeptidolysis of alpha-alpha and gamma-gamma fibrin chains bound by epsilon-(gamma-Glu)-Lys-isopeptide bonds.

Destabilase from the medicinal leech is a representative of a novel family of lysozymes

Intrinsic lysozyme-like activity was demonstrated for destabilase from the medicinal leech supported by (1) high specific lysozyme activity of the highly purified destabilase, (2) specific inhibition of the lysozyme-like activity by anti-destabilase antibodies, and (3) appreciable lysozyme-like activity in insect cells infected with recombinant baculoviruses carrying cDNAs encoding different isoforms of destabilase. Several isoforms of destabilase constitute a protein family at least two members of which are characterized by lysozyme activity. The corresponding gene family implies an ancient evolutionary history of the genes although the function(s) of various lysozymes in the leech remains unclear. Differences in primary structures of the destabilase family members and members of known lysozyme families allow one to assign the former to a new family of lysozymes. New proteins homologous to destabilase were recently described for Caenorhabditis elegans and bivalve mollusks suggesting that the new lysozyme family can be widely distributed among invertebrates. It remains to be investigated whether the two enzymatic activities (isopeptidase and lysozyme-like) are attributes of one and the same protein.