[Gene expression of vascular endothelial growth factors and their receptors in different variants of the course of multiple myeloma].

Aim: To determine the significance of the angiogenic activity estimated from the gene expression of the vascular endothelial growth factors (VEGFs) VEGF-A, VEGF-C, and VEGF-D and their receptors VEGFR1, VEGFRls, VEGFR2, and VEGFR3 in the mononuclear cell fraction of bone marrow (BM) aspirates with tumor plasma cells predominating in different variants of the course of multiple myeloma (MM).

Materials And Methods: The gene expression of VEGF-A, VEGF-C, and VEGF-D and their receptors VEGFRI, VEGFRls, VEGFR2, and VEGFR3 was determined by reverse-transcription polymerase chain reaction (RT-PCR).

Results: VEGF-A, VEGF-C, VEGF-D, as well as VEGFR1, VEGFRls, VEGFR2, and VEGFR3 were expressed showing different intensities in the mononuclear cell fraction of BM aspirates with a predominance of tumor plasma cells in the patients with MM, which allowed patient groups to be identified.

Coexpression of two mRNA isoforms of insulin-like growth factor-1 gene and mRNA of YB-1 gene in patients with multiple myeloma.

Coexpression of two mRNA isoforms for insulin-like growth factor-1 (IGF-1A and IGF-1B) and expression of YB-1 mRNA were analyzed in the bone marrow aspirates from 19 patients with multiple myeloma. It was shown that mRNA isoforms for IGF-1A and IGF-1B were mainly expressed in samples with hyperexpression of YB-1 mRNA, and, on the contrary, practically were not expressed (except sporadic cases) in samples with low level of YB-1 mRNA expression. Coexpression of mRNA isoforms for IGF-1A and IGF-1B were observed in 80% patients with multiple myeloma.

Expression of vascular endothelial growth factor receptors VEGFR1 in cultured multiple myeloma cells: correlation with immunophenotype and drug resistance.

We studied the expression of genes encoding vascular endothelial growth factors VEGF-A, VEGF-C, VEGF-D and their receptors in cell cultures of human multiple myeloma IM9, RPMI 1640, RPMI 8226. The studied cells did not differ by the expression of growth factors. Expression of VEGFR1 receptor was detected only in IM9 cells and VEGFR2 and VEGFR3 receptors were not expressed in multiple myeloma cells.

Influence of proteasome inhibitor bortezomib on the expression of multidrug resistance genes and Akt kinase activity.

The goal of this work was to study the mechanisms of ABC family transport proteins' regulation by a new-generation antitumor drug - the proteasome inhibitor bortezomib (Velcade). ABC transporters determine the multidrug resistance of tumor cells (MDR). We confirmed our previously discovered observation that bortezomib affects the expression of genes involved in the formation of MDR (ABCB1 gene, also known as MDR1, and ABCC1-MRP1), reducing the amount of their mRNA.

Isolation and characterization of highly radioresistant malignant hamster fibroblasts that survive acute gamma irradiation with 20 Gy.

To study the acquired radioresistance of tumor cells, a model system of two cell lines, Djungarian hamster fibroblasts (DH-TK-) and their radioresistant progeny, was established. The progeny of irradiated cells were isolated by treating the parental cell monolayer with a single dose of 20 Gy (PIC-20). The genetic and morphological features, clonogenic ability, radiosensitivity, cell growth kinetics, ability to grow in methylcellulose, and tumorigenicity of these cell lines were compared.

[Retention of tumorigenicity in radioresistant progeny of cells surviving exposure to high doses of gamma irradiation].

The cell tumorigenic ability and the cell clonogenicity in semi-solid medium of highly radioresistant variant cell line, PIC-20 (the progeny of djungarian hamster fibroblast cell line DX-TK- surviving acute exposure to 20 Gy of gamma-irradiation), were examined. In the absence of additional radiation, no differences between tested features of non-irradiated PIC-20 cells and parental DX-TK- cells were observed. On the contrary, after gamma-irradiation with high doses the essential differences in the properties of the examined cell lines were revealed.

Effects of isoprenoid analogues of SDB-ethylenediamine on multidrug resistant tumor cells alone and in combination with chemotherapeutic drugs.

Multidrug resistance (MDR) mediated by P-glycoprotein (Pgp) remains the major obstacle for successful treatment of cancer. Inhibition of Pgp transport is important for higher efficacy of anticancer drugs. Lipophilic cationogenic amines with at least one tertiary N atom, such as verapamil, are classical PgP-blocking agents.

[Relationship between the induction of MDR1, a multidrug resistance gene in tumor cells, and apoptosis].

Gene MDR1 coding for P-glycoprotein belongs to a group of genes responsible for cell defense. Overexpression of this gene determines the resistance of tumor cells to a series of chemotherapeutic drugs known as multidrug resistance. Many chemotherapeuticals induce both apoptosis and transcriptional activity of the MDR1 gene in tumor cells.

Differential effects of the MDR1 (multidrug resistance) gene-activating agents on protein kinase C: evidence for redundancy of mechanisms of acquired MDR in leukemia cells.

Human leukemia cells may acquire MDR1/P-glycoprotein-mediated multidrug resistance (MDR) in the course of short-term (within hours) exposure to many stress stimuli. This effect is thought to be associated with the activity of protein kinase C (PKC) (Chaudhary, Roninson, 1992. 1993).

[Adaptation of reverse transcriptase polymerase chain reaction for clinical diagnosis of expression of MDR1 gene].

Chemotherapy of malignant tumors is ineffective usually because of tumor cell resistance to it. Two types of resistance are known: cell resistance to a certain drug and multiple drug resistance (MDR). MDR covers a wide spectrum of drugs with different chemical structure and mechanisms of action.

Induction of P-glycoprotein functional activity and multidrug resistance by a soluble factor(s) produced by some mammalian cells.

In the previous study we have found that Djungarian hamster fibroblasts with high levels of multidrug resistance (MDR) (colchicine-resistance index RI of 1000 to 42000) produce soluble factor(s) communicating MDR to the drug-sensitive cells of the same species by elevating the functional activity of P-glycoprotein (Pgp). Here we have shown that these cells can influence human tumor cells in the same fashion. Rat hepatoma McA RH7777 cells and their colchicine-resistant derivatives are shown to produce a factor with similar effects (induction of MDR and Pgp functional activity in the drug-sensitive cells).

Expression of the FLT4/VEGFR3 receptor tyrosine kinase encoding gene in hepatic tumors.

The FLT4/VEGFR3 tyrosine kinase receptor belongs to a class of receptors for growth factors of the vascular endothelial growth factor family and is important for the biology of lymphatic endothelium. It may play an important role in tumor growth. We have looked for the expression of the FLT4 gene in tumors of various origins.

Colchicine-resistance and enhancement of P-glycoprotein activity after co-cultivation of drug-sensitive cells with multidrug resistant variants.

The role of cellular interactions in the resistance of Djungurian hamster cells to colchicine (CH) and in the efficiency of P-glycoprotein function was studied. Mixtures of CH-resistant and CH-sensitive cells as well as control unmixed cells were propagated for 3 days and the sensitivity of the cells to CH was measured by colony forming assay. Identification of individual subpopulations was possible due to genetic marker (6TG-resistance).

Evidence for formation of somatic cell hybrids in a population of irradiated cells.

Experiments using two genetically marked lines of Djungarian hamster cells (DM-15 HPRT- and DH-TK-) and the technique of hybrid selection in selective HAT medium revealed viable colonies in a mixed culture irradiated with a dose of 5 Gy. The sublines grown from these colonies were examined. Chromosome analysis showed that about 45% of those cells were hybrids inheriting chromosome markers of both parent strains.

[The formation and viability of hybrid cells in a population after irradiation at lethal doses].

With the use of two genetically labeled lines of Djungarian hamster cells and the method of hybrid selection on a HAT-selective medium it was found that in the irradiated mixed culture of the above cell lines, cells were formed that survived in the conditions of total destruction of irradiated parent cells. The chromosome analysis showed that about 45% of the survived cells were hybrids resulting from the radiation-induced fusion of two initial cell lines. These hybrid cells were capable of reproduction.

[The reproductive characteristics of the tick-borne encephalitis virus in interspecific somatic hybrids].

The study dealt with features of tick-borne encephalitis virus reproduction in two series of interspecies somatic hybrids generated by fusion of transformed cells of Chinese hamster (Ag17) with human diploid fibroblasts (KM/3) and with pseudonormal cells of Indian deer (Muntiacus munjak) (KOM). The viral infection in hybrid Ag17 cells ran an acute course with cell damage, but in KM/3 and KOM cells virus multiplication was not accompanied by the development of cytopathic effect. Two other parameters of tick-borne encephalitis virus infection under study: the extent of infectious particles production and electroimmunochemical properties were found to be under control of genomes of different parental cells.

[Effects of monoclonal antibodies to bovine nerve growth factor on NGF-induced cell differentiation in culture].

Five Hybridoma clones producing monoclonal antibodies (MAT) to bovine nerve growth factor (NGF) were developed. The biological effects of antibodies were studied: the influence of MAT on neurit outgrowth induced by NGF in rat pheochromocytoma PC12 or spinal chicken ganglia was investigated. MAT fell into two groups.

[Normalization of the phenotype of transformed Djungarian hamster cells during selection for colchicine resistance].

The range of the Djungarian hamster cell lines selected for colchicine resistance in high doses (from 7 to 200 micrograms/ml) was studied. These cell lines are characterized by the different levels of drug-resistance (1000- to 16000-fold). A positive correlation is found between the reversion rate of malignant phenotype and the cellular drug-resistance level.

[Fusion of cultured Djungarian hamster tumor cells with the host cells in vivo and the characteristics of the hybrids obtained].

Tumor Djungarian hamster cells resistant to 5-bromodeoxyuridine (5-BrdU) were inoculated to newborn hamsters. Tumors occurred in animals and were seeded into HAT medium in vitro. This procedure permitted to select hybrids between tumor and normal cells established in vivo.

[Expression of malignancy traits in the interspecific somatic hybrids of tumor and normal cells].

Tumorigenicity and anchorage independence in two types of the interspecies hybrids of the tumor and normal mammalian cells were studied. One hybrid type was derived from fusion of spontaneously transformed Chinese hamster and normal mouse cells; the second type was obtained by fusion of SV40-transformed Djungarian hamster and the same mouse cells. The tumorigenicity in the athymic nude mice was suppressed in the first type of hybrids.

[Expression of transformation characters in colchicine-resistant tumor cells].

Malignancy and anchorage independence of Djungarian hamster tumor cell lines resistant to different doses (0.1-5.0 micrograms/ml) of colchicine were studied.

[Manifestation of malignancy in somatic hybrids obtained by the cell fusion of 2 tumor lines].

Malignancy of 6 independent hybrid clones derived from fusion of two tumor cell lines of Djungarian hamster, which had been transformed with SV40 virus, was studied. In most of the hybrid clones, suppression of the ability to grow progressively in vivo and the increase in the latent period of tumor occurrence were observed. These data bear witness to suggestion about the existence of different genetic alterations in these tumor cells.

[Relation of mammalian cell resistance to actinomycin D with a change in the karyotype and a decrease in cytoplasmic membrane permeability].

Djungarian hamster cell lines, selected for resistance to 2 microgram/ml of actinomycin D (AD) have been studied. These lines are 1000-4000 times more resistant to AD than the parent cells. AD-resistance is an unstable property.

[Actinomycin D and 6-mercaptopurine-resistant Djungarian hamster cell line: karyotype, morphology, malignancy].

Djungarian hamster cell lines resistant to actinomycin D (AD) were developed from SV40 transformed HGPRT- cell, line DM-15. Increase in resistance to AD up to 4000 fold was obtained. The acquisition of resistance to AD did not influence the expression of the first mutation--HGPRT-.

Somatic cell hybrids of the Djungarian hamster: malignancy and evolution of the karyotype.

Djungarian hamster somatic cell hybrids were obtained by fusing malignant SV40-transformed fibroblasts (line DM15, HGPRT-), and normal male lymphoid cells. Tumorigenicity, growth in soft agar and karyotype changes of 10 independent hybrid clones were studied. All hybrids grew as tumors after injection of new-born hamsters with 1 x 10(6) cells.