Analysis of Antitumor Activity of the Liposomal Photosensitizer Lipophthalocyan.

We studied specific antitumor activity of a liposomal drug based on tetra-3-phenylthiophthalocyanine aluminum hydroxide (lipophthalocyan) intended for photodynamic therapy. The optimal dose and protocol for photodynamic therapy with lipophthalocyan were chosen in experiments on mice: single intravenous dose of 6 mg/kg with a 5-h interval between administration and laser exposure and irradiation energy density of 400 J/cm2. A wide spectrum antitumor activity of lipophthalocyan was demonstrated in vivo for various transplantable mouse tumors (Lewis lung epidermoid carcinoma, S37 sarcoma, and colon adenocarcinoma AKATOL). The results show the possibility of using lipophthalocyan for photodynamic therapy of tumors of surface localization (skin and mucosa tumors).

Ah-receptor-independent stimulation of hepatoma 27 culture cell proliferation by polycyclic aromatic hydrocarbons.

The proliferative effect of some compounds that are aryl hydrocarbon (Ah) receptor ligands was studied on hepatoma 27 cells with absent expression of Ah receptor. Compounds of the polycyclic aromatic hydrocarbon (PAH) class benzo/a/pyrene, 3-methylcholanthrene, 7,12-dimethylbenz/a/anthracene, and benzo/e/pyrene as well as ß-naphthoflavone (ß-NF) and chlorinated hydrocarbon Aroclor 1254 were studied. It was found that carcinogenic PAH and ß-NF stimulate cell proliferation both under conditions of standard serum content and in a medium with low serum content. More efficient stimulation of proliferation was observed in the case of low serum content. Aroclor 1254 and benzo/e/pyrene did not stimulate cell proliferation. Stimulation of proliferation was accompanied by activation of the ERK1/2-dependent MAP-kinase cascade. Benzo/a/pyrene caused a decrease in the number of cells in G1 phase of the cell cycle and increase in number of cells in G2/M phases under conditions of cell growth in media with low serum content. Carcinogenic PAH and ß-NF activated transcription factor AP-1, and in this case activation was more pronounced in cells grown in medium with low serum content. A possible mechanism of activation of proliferation by an Ah receptor-independent pathway is discussed.

NF-kappaB suppression provokes the sensitization of hormone-resistant breast cancer cells to estrogen apoptosis.

The progression of breast cancer cells to estrogen-independent growth may be accompanied with the paradoxical cell sensitization to estrogen apoptotic action; however, the mechanism of this phenomenon is still unclear. In the present study, we have shown that the sensitization of hormone-resistant breast cancer cells to estrogen apoptotic action is accompanied with the gradual NF-kappaB suppression. Using the chemical inhibitors of NF-kappaB as well as the dominant-negative NF-kappaB constructs, we have proved the sufficiency of NF-kappaB inhibition for the sensitization of the resistant cells to estrogen apoptosis. Estradiol treatment results in the additional suppression of NF-kappaB, demonstrating the possible NF-kappaB involvement in the regulation of cell response to estrogens. Totally, the results presented suggest that the constitutive NF-kappaB suppression in the estrogen-independent cells may be considered as one of the factors resulting in a imbalance between pro- and anti-apoptotic pathways and enhancement in estrogen apoptotic action in the cells.

Appearance of differentiation characteristics (induction of Ah-receptor-dependent genes) during cultivation of transformed cell clone K8 from embryonic rat fibroblasts.

The differentiation status of fibroblasts can be characterized by their ability to induce Ah-receptor-dependent genes. The ability to induce Ah-receptor-dependent genes encoding cytochrome P450 isoforms, Ah-receptor repressor, and NADPH-quinine oxidoreductase were studied in the transformed cell clone K8 obtained from immortalized embryonic rat fibroblasts by treatment with benzo(a)pyrene and in the parental clone F27. Treatment with benz(a)anthracene did not induce the genes in the transformed clone K8 on passages 4-14, but the induction was recorded in the transformed clone beginning from the 16th passage and later, whereas in F27 cells the induction was observed throughout the experiment. Induction levels of mRNA of the induction-regulating genes encoding the Ah-receptor and Ah receptor nuclear translocator were similar in F27 cells and in the transformed cell clone K8 in both early and late passages. Electrophoretic mobility shift assay showed that in clone K8 transmission of the induction signal was disturbed in the early passages before interaction of the activated Ah-receptor with the recognizing region of DNA. Possible mechanisms responsible for the absence of induction in the early passages in the transformed cells are discussed.

[A comparative study of induction regulation in cytochromes family 1 P450 in cell cultures at different stages of tumor transformation].

Lipophilic xenobiotics, including some carcinogenic agents and cytostatics, are metabolized by cytochrome P450 isoforms (CYP). In tumours expression of CYP genes and their inducibility are lower than in a homologous normal tissue. This phenomenon determines the known higher cytostatic stability of tumour cells. To clarify, at which particular stage of tumour transformation the level of family 1 CYP may change, we compared mRNA expression of CYP1A1, CYP1B1 and also of proteins regulated CYP expression: Ah receptor, ARNT and AHRR. For this aim we studied embryonic and fibroblast-like cells, in addition to cells of the same types but immortalized by the Rausher virus, or spontaneously after crisis. Besides, we investigated transformed clones obtained by means of benzo/a/pyrene action on Rausher virus-immortalized cells. Constitutive expression of genes studied in all cell cultures was shown. Benzo/a/anthracene induction increases the mRNA expression of all inducible genes (CYP1A1, CYP1B1, AHRR) in the original embryonic cells, in Rausher virus-immortalized cells, and in transformed clone K2. In both spontaneously immortalized cells and transformed clone K1 only CYP1B1 was induced. In transformed clone K8 no inducible gene was induced. In summary, we have shown that: (1) the ability of immortalized cells to CYP induction is determined not only by their capacity for a non-limited persistence, but also by the nature of immortalization; (2) despite their common genesis, the transformed clones differ in their ability to induce CYP. In addition to Ah receptor and ARNT, some other, yet unknown factors may also take part in CYP induction.

Comparative analysis of family 1 cytochrome p-450 mRNA expression in human intestinal adenocarcinoma and intact portion of the intestine.

The expression of mRNA of proteins involved in the transformations of cytostatics (cytochrome P-450 1A1 and 1B1 isoforms) and genes encoding proteins participating in their regulation (Ah receptor, AHRR and ARNT) in intestinal tumors and intact portions of the intestine were studied. The expression of cytochrome P-450 1A1 increased in poorly differentiated tumors in comparison with its expression in intact portions of the intestine (tumor/intact tissue=1.65). The expression of cytochrome P-450 1B1 was higher in well-differentiated tumors (tumor/intact tissue=1.62). The possibility of practical use of high expression of cytochrome P-450 isoforms in tumors in comparison with intact intestinal tissue is discussed.

Benzo[a]pyrene-dependent activation of transcription factors NF-kappaB and AP-1 related to tumor promotion in hepatoma cell cultures.

The activation by the carcinogenic polycyclic aromatic hydrocarbon (PAH) benzo[a]pyrene (BP) of transcription factors NF-kappaB and AP-1 in hepatoma 27 and HepG2 cell cultures was studied. In contrast to the hepatoma HepG2 cells, cytochrome P450 isoforms and Ah-receptor are not expressed in the hepatoma 27 cells. The transcription factor NF-kappaB was activated only in the hepatoma 27 cells by BP treatment but not by its noncarcinogenic isomer benzo[e]pyrene (BeP). Conversely to NF-kappaB activation the transcription factor AP-1 was activated in the hepatoma HepG2 cells by cell treatment with BP but not in the hepatoma 27 cells. It is concluded that the NF-kappaB activation is caused by nonmetabolized BP molecule and not related to activation of the Ah-receptor. The transcription factor AP-1 seems to be activated as a result of the interaction of BP with the Ah-receptor. The realization of tumor promotion stage by carcinogenic PAHs treatment in dependence on the cytochrome P450 and Ah-receptor levels in the initiated cells is discussed.