Role of tumor/endothelial cell interactions in tumor growth and metastasis.

BACKGROUND: It is known that interactions between tumor and endothelial cells have a significant influence on the growth and metastasis of malignant tumors. AIM: To study the reciprocal effect of Lewis lung carcinoma (LLC) and endothelial cells on the growth rate of each other upon their co-cultivation in vitro and to assess the contribution of such tumor/endothelial cell crosstalk to in vivo LLC growth and metastasis. MATERIALS AND METHODS: Two variants of Lewis lung carcinoma cells, high-metastatic (LLC) and low-metastatic (LLC/R9), and murine aorta endothelial cell line (MAEC) were used. Kinetics of tumor cell growth in vitro and in vivo, electrokinetic properties of tumor cells and their adhesion to endothelial monolayer, and the number of tumor and endothelial viable cells after 1-day contact or non-contact co-cultivation were estimated. RESULTS: LLC/R9 had significantly higher growth rate in vivo (as opposed to in vitro) than LLC. However, the number and volume of lung metastatic lesions in LLC/R9-bearing mice were 4.5-fold (p < 0.05) and 3.6-fold lower (p < 0.05), respectively, compared to those in LLC-bearing mice. Non-contact co-cultivation of LLC/R9 + MAEC caused more than a 34% (p < 0.05) LLC/R9-induced increase in the number of MAEC and a 60% (p < 0.05) MAEC-induced increase in the number of LLC/R9 cells as compared to those of corresponding controls (cells cultured alone). In contrast, in the case of LLC + MAEC, both the number of LLC and MAEC cells after their non-contact co-cultivation and cultivation alone did not differ significantly. Contact co-cultivation LLC+MAEC (in contrast to LLC/R9+MAEC) caused more than a 50% (p < 0.01) LLC-induced decrease in the number of MAEC and a 50% decrease (p < 0.05) MAEC-induced in the number of LLC cells as compared to the corresponding controls. Both tumor cell variants showed a bimodal distribution of cells by ζ-potential, but in the case of LLC there was observed a shift towards high values due to 52% of cells with a surface charge density > 10 C/m2, while in the case of LLC/R9 such a subpopulation was absent and 19% of cells had a surface charge < 5 C/m2. The number of LLC cells that adhered to the monolayer of endothelial cells was by 65% (p < 0.05) higher than that of LLC/R9 cells. CONCLUSION: Obtained data demonstrated that the tumor/endothelial cell relationships might reflect the features of tumor growth and metastasis of a malignant tumor.

Changes in VEGF level and tumor growth characteristics during lewis lung carcinoma progression towards cis-DDP resistance.

AIM: To study the relationship between tumor angiogenic potential and its growth and metastasis using Lewis lung carcinoma (LLC) models with different degree of resistance to cis-diamminedichloroplatinum (cis-DDP). METHODS: LLC and its two cis-DDP-resistant variants (LLC-9 LLC-19), were used. For determination of angiogenic potential of LLC, LLC-9 and LLC-19, the level of VEGF production by these tumor cells in vitro and the level of circulating VEGF during tumor growth in vivo was measured by enzyme-linked immunosorbent assay. RESULTS: Progressive decrease of LLC-9 and LLC-19 sensitivity to action of cis-DDP evidenced in vitro (IC50=0.0077+/-0.0005 mg/ml and 0.0156+/-0.0008 mg/ml respectively vs. 0.004+/-0.0003 mg/ml for LLC, p<0.05) and in vivo (index of primary tumor growth inhibition by cis-DDP was 26% and 3% respectively vs. 46%; index of metastasis inhibition--46% and 11% vs. 65%, p<0.05) was accompanied by the significant changes of tumor angiogenic potential. The level of VEGF production by primary culture of LLC-9 in vitro was 1.5 fold higher (p<0.05) than that by primary culture of LLC, whereas there were no differences in the level of VEGF production between LLC-19 and LLC. The level of circulating VEGF drastically increased in the initial phase of LLC-9 and LLC-19 growth in vivo, whereas in LLC bearing mice the dynamic changes of VEGF level are characterized by the presence of long-term latent period (t(lag)=17.0+/-0.3 days). In LLC bearing mice the character of changes of circulating VEGF level significantly correlated with the number of metastases (p<0.001) but not with tumor volume; while in LLC-9 bearing mice - with tumor volume (p<0.01) and the number of metastases (p<0.05). Although maximum level of circulating VEGF was significantly (p<0.05) higher in LLC-9 bearing mice than that in LLC bearing mice, maximum number of lung metastases was significantly (p<0.05) lower in LLC-9 bearing mice vs LLC. In contrast to LLC-9, in LLC-19 bearing mice the level of metastatic injury was significantly elevated (p<0.05) and the level of circulating VEGF considerably correlated with both tumor volume (p<0.01) and metastatic index (p<0.01). CONCLUSION: There is revealed a direct correlation between the level of circulating VEGF and all parameters of tumor progression observed only in the cases of highly resistant tumors, whilst elevation of circulating VEGF level during tumor growth in vivo could be considered as a marker of metastasis not dependent on a drug resistance of tumor.

Influence of aconitine-containing herbal extract BC1 on proliferative and electrokinetic characteristics of endothelial cells.

AIM: To evaluate the influence of new antitumor preparation BC1 produced on the base of Aconitum species on viability and electrokinetic properties of endothelial cells for estimation of mechanisms of its antitumor and antimetastatic activity. MATERIALS AND METHODS: Cytotoxic/cytostatic action of BC1 toward murine aorta endothelial cells (MAEC) and tumor LLC/R9 cells was studied using MTT-test. Apoptotic rate of MAEC was performed by flow cytometry. Electrokinetic properties of MAEC were determined by linear rate of their migration in electric field with the voltage of 20 V/cm. RESULTS: After 24 h of incubation with BC1, IC50 for actively proliferating was 0.95 -/+ 0.06 microg/ml and was 9-fold and 14-fold lower (p < 0.05) than that index for confluent endotheliocytes and LLC/R9 cells respectively. The ability of BC1 to alter electrokinetic characteristics of MAEC and to induce apoptosis has been demonstrated. At the concentration of IC50/10, 1 caused 2-fold decrease of zeta-potential and surface density of charge of compared to the control (p < 0.05) whilst at the concentration of IC50/20 - inversion of surface charge of the majority (80%) of the cells in association with BC1-induced apoptosis. CONCLUSION: High sensitivity of actively proliferating MAEC to the action of BC1 was revealed as well as the ability of that preparation to cause apoptosis and inversion of surface charge of endothelial cells.

A protein kinase inhibitor from A431 subline overexpressing TGF alpha possesses antimicrobial activity.

During the last decade the key role of antimicrobial peptides in innate immunity has been argued. They were found in plants and in different phylogenic groups of animals (insects, amphibia, and even in mammals). We report the production of a human peptide antibiotic that was previously characterized as an EGF receptor tyrosine kinase inhibitor in epidermoid carcinoma A431/1522 cell subline overexpressing TGF alpha. It is a 3 kDa hydrophobic cationic peptide cytotoxic for different species of Gr+ and Gr- bacteria in micromolar concentration range, and demonstrating slight fungicidal activity.