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Biomedical subjects

M A Krasil'nikov

Publications and source records attributed to M A Krasil'nikov.

At least 19 recordsLinked to original sources
PubMed2006

Sensitization of MCF-7 breast cancer cells to the apoptotic effect of estradiol.

A new substrain of hormone-resistant MCF-7/T breast cancer cells was selected after long-term culturing of estrogen-dependent MCF-7 cells in the presence of tamoxifen. These cells were resistant to the growth-stimulating and cytostatic effects of estradiol and tamoxifen, respectively. MCF-7/T cells gained paradoxical sensitivity to the apoptotic effect of estradiol. Estradiol stimulated p53 expression and decreased DNA-binding activity of NF-kappaB. Our findings provide indirect evidence that these proteins are involved in the regulation of estrogen-induced apoptosis. These results indicate that tamoxifen-resistant breast cancer cells can be sensitized to the apoptotic effect of estradiol. The data form a basis for the development of new methods of endocrine therapy for breast cancer patients.

Antineoplastic Agents↗
PubMed2004

Role of phosphatidylinositol-3 kinase in regulation of differential sensitivity of melanoma cells to antitumor agents. A model for hormone resistance development in tumor cells.

Phosphatidylinositol-3 kinase (PI3K) belongs to one of the most important cellular proteins involved in the transmission of anti-apoptotic signal and regulation of survival pathways in tumor cells. Earlier we have found that prolonged treatment of melanoma cells with dexamethasone results in formation of a cell subline which was resistant to growth inhibitory dexamethasone action. We showed that constitutive activation of PI3K can be considered as one of the factors that regulate cell resistance to dexamethasone. Here we demonstrate that increased level of PI3K protein in dexamethasone-resistant cells correlates with partial decrease in expression of down-stream target of PI3K--protein kinase B (PKB). Study of the cell's sensitivity to various damaging agents showed that the cells after prolonged dexamethasone treatment are characterized by increased level of the resistance to both hormonal drugs and hypoxia, and at the same time with high sensitivity to ultraviolet (UV) radiation or anti-tumor agents such as adriamycin. As revealed, hypoxic conditions or short-term dexamethasone treatment of the resistant cells lead to a substantial increase in the PKB level, whereas neither UV radiation nor adriamycin affects the PKB level in these cells. We demonstrate that long-term dexamethasone treatment of melanoma cells results in the accumulation of the active form of mitogen-transducing signaling protein STAT3 (Signal Transducer and Activator of Transcription-3), which also contributes to inducing the melanoma cell's resistance to antiproliferative action of dexamethasone. We suggest that decreased level of PKB in combination with an activation of PI3K/STAT3 signaling in the melanoma cells after prolonged dexamethasone treatment may be one of the mechanisms of different sensitivity of these cells to hormonal drugs and damaging agents. The model of the progression of hormonal resistance of in vitro cultured tumor cells is presented.

3-Phosphoinositide-Dependent Protein Kinases↗
PubMed2004

[The molecular mechanism responsible for the adaptation of malignant tumors to hormonal drugs: a role of phophatidylinositol-3-kinase and phosphoinositide-dependent proteins].

Phophatidylinositol-3-kinase (PI3K) is a major intracellular protein that is responsible for the transmission of an antiapoptotic signal and controls the survival of tumor cells upon exposure to damaging agents. Experiments using different tumor cell cultures have shown that the resistance of cells to the antiproliferative action of dexamethasone, caused by their long cultivation with the hormone, is associated with the activation of PI3K and the transcription factor STATS. The activation of PI3K and STAT3 in the dexamethasone-resistant cells correlates with the increase in the total thyrosine kinase activity and with the decrease in the sensitivity of cells to exogenous proliferative agents, such as 17beta-estradiol. The long exposure of hormone-sensitive cells to nonhormonal factors that activate the PI3K/STAT3 signaling pathway, hypoxia in particular, has been shown to suffice to reduce the degree of hormonal tumor cell dependence. VEGF-A, an angiogenic peptide whose action was partially realizes through the PI3K-signalling pathway, has been demonstrated to be involved in the maintenance of cell growth, including the growth of hormone-independent cells. The findings suggest that complex changes in the antiapoptotic and mitogenic signaling pathways associated with PI3K, which ensures the autonomic, hormone-independent growth of tumor cells, may underlie the decreased hormonal dependence of tumor cells. Whether PI3K may be used to suppress the growth of hormone-independent tumors is discussed.

Adenocarcinoma↗
PubMed2001

[Role of phosphatidylinositol signalling path in developing hormonal resistance in tumor cells].

Phosphatidylinositol 3-kinase (PI3K) is a key regulatory protein which is responsible for anti-apoptotic signal transduction regulating cell survival during exposure to damaging factors. The report deals with the role of the PI3K signaling pathway in regulating cellular response to hormones and, particularly, in development of resistance as a result of long-term exposure of cells to steroid cytostatic hormones. In our study, even a short-term exposure of transformed fibroblasts of hamster (line 2PK) resulted in an activation of main PI3K effectors (MAP-kinase and protein kinase B (PKB)) which appeared against the background of hormone-induced inhibition of cellular growth. A long-term (3 months) cell culturing with dexamethasone was followed by formation of subpopulations of cells which were refractory to the growth inhibition by hormone and were characterized by high levels of activity of PI3K, MAP-kinases and PKB. Activation of PI3K and PI3K-dependent enzymes correlated with enhancement of synthesis of c-jun, a component of the AP-1 transcriptional factor, was observed both in short- and long-term application of dexamethasone. We believe that, during long-term exposure of cells to cytostatic hormones, continuous activation of PI3K and PI3K-dependent transcriptional factors may result in a significant restructuring of intracellular signal pathway, and, finally, constitutive PI3K-signal pathway and partial overcoming the proliferative block by cells.

Cell Division↗
PubMed2000

Expression of phosphatidylinositol-3 kinase in lung cancer.

The expression of phosphatidylinositol-3 kinase in tumors and homologous tissues from 29 patients with lung cancer, 5 patients with lung metastases of various tumors, and some non-tumorous pulmonary diseases was studied by Western blot analysis. The expression of phosphatidylinositol-3 kinase was increased in these tumors in comparison with histologically intact lung tissue in 5 patients with non-small-cell cancer. In 20 patients expression of phosphatidylinositol-3 kinase was the same as in homologous tissue and in 4 patients it was decreased. No relationship between phosphatidylinositol-3 kinase expression and clinical and morphological characteristics of lung cancer was revealed.

Adenocarcinoma↗
PubMed1999

The role of phosphatidylinositol 3-kinase in the regulation of cell response to steroid hormones.

Phosphatidylinositol 3-kinase (PI-3 kinase) has been implicated in the regulation of many cellular processes, including growth and transformation. We describe the effect of glucocorticoids on cell growth, phosphoinositide formation and PI-3 kinase activity in Rous sarcoma virus-transformed hamster fibroblasts (HET-SR). Using a prolonged dexamethasone treatment of HET-SR cells we have selected a new glucocorticoid receptor-positive cell subline, HET-SR(h), that was resistant to growth inhibitory action of dexamethasone and/or non-hormonal drugs (vinblastine, adriamycin) and was characterized by higher levels of phosphoinositide formation and increased PI-3 kinase activity. Study of the short-term hormone action has shown that both dexamethasone-sensitive and -resistant sublines responded to hormone by a decrease in phospholipid turnover rate. At the same time, in both cell lines activation of PI-3 kinase after dexamethasone addition was revealed. Dexamethasone-dependent activation of PI-3 kinase was more significant and maintained for a longer period in HET-SR(h) cells than in parent HET-SR cells. Finally, by transfecting p110*, a constitutively active catalytic subunit of PI-3 kinase, into hormone-sensitive HET-SR cells, we have found a marked increase in cell resistance to growth inhibitory dexamethasone action. These results suggest that PI-3 kinase may serve as one of the factors providing cell resistance to cytostatic drugs.

Animals↗
PubMed1999

Phospatidylinositol 3-kinase expression in human breast cancer.

Phospatidylinositol 3-kinase (PI 3-kinase) expression was analysed by Western blotting with monoclonal antibodies to the p85 subunit in a series of tumour and adjacent mammary gland samples collected at surgery from 33 breast cancer patients. Seventy-nine percent of the investigated pairs of the samples were characterised by an increased level of PI 3-kinase in the tumour in comparison with the adjacent mammary gland. PI 3-kinase activation was not associated with tumour steroid receptor status, histologic grade and other clinico-morphological characteristics. Furthermore, immunoblotting of epidermal growth factor receptor (EGFR) in the tumours with increased PI 3-kinase and corresponding adjacent tissues revealed no association between EGFR and PI 3-kinase activation. Thus, increased PI 3-kinase expression appears to be a widespread feature of breast cancer not associated with the main biological markers of its prognosis and hormone sensitivity.

Adult↗
PubMed1996

[Effect of specific activation of phosphatidylcholine metabolism in hamster fibroblasts transformed by Rous sarcoma virus].

Transformation of embryonic hamster fibroblasts by the Rous sarcoma virus results in sharp increase of the turnover rate of one of cellular phospholipids-phosphatidylcholine. The decrease in the rate of virus-transformed cells (HETSR strain) during the monolayer formation is attended by additional activation of phosphatidylcholine turnover. A similar effect is observed after prolonged culturing of cells with dexamethasone. Addition of the tyrosine kinase inhibitor, genistein, to cells leads to selective inhibition of phosphatidylcholine synthesis without any effect of phosphoinositide synthesis. Immunoblotting analysis of p60-src, the product of the viral oncogen v-src related to the tyrosine kinase family failed to produce any significant changes in protein synthesis and activity during dexamethasone-induced inhibition of HETSR cell growth. The data obtained testify to selective activation of phosphatidylcholine metabolism in src-transformed cells which enhances with a decrease in the rate of cell growth. The presence in HETSR cells of p60-src whose synthesis is not controlled by dexamethasone may be responsible for increased phosphatidylcholine metabolism and sustaining cell growth under conditions of limited activity of growth-promoting compounds.

Animals↗
PubMed1995

Comparative analysis of the sensitivity of endometrial cancer cells to epidermal growth factor and steroid hormones.

BACKGROUND: Epidermal growth factor (EGF) and EGF-regulated processes play an important role in steroid signal transduction. Comparative analysis of EGF and steroid receptor expression and the sensitivity of early stages of proliferation induction, such as activation of phospholipid turnover to EGF and steroids, may provide a useful new approach to characterizing the sensitivity of endometrial cancer to hormone therapy. METHODS: Progesterone (PR), estradiol (ER), and EGF receptor (EGFR) content was measured by radioligand competitive methods in surgically excised tumors from 26 patients with primary endometrial cancer. In short term cell cultures isolated from 11 of these tumors, the influence of a 10-minute treatment with 10(-8)M EGF either alone or combined with 10(-8)M progesterone on 32P-incorporation into phospholipids was studied. Phospholipids were fractionated by thin-layer chromatography and were located by autoradiography, and quantification of the labeled compounds was made by densitometric scanning of the autoradiograms. RESULTS: Epidermal growth factor receptor was found in 15 of 26 (58%) endometrial cancer samples. Eighty-two percent of the tumors studied contained PR, and 81% contained ER. No significant correlations were revealed between EGFR and ER/PR status or concentration. Epidermal growth factor stimulated 32P-incorporation by more than 120% of the control level in five of seven EGFR-positive and in one of four EGFR-negative endometrial cancer samples. An inverse relationship was revealed between EGFR content and the percentage of EGF-induced stimulation of phospholipid turnover in endometrial cancer cells (r = -0.6; P = 0.15) and between EGFR content in EGFR-positive samples and the extent of progesterone suppression of EGF-induced turnover (r = -0.77; P = 0.04). CONCLUSIONS: Determination of EGF sensitivity on a receptor and a functional level may provide important additional information about the hormonal sensitivity of endometrial cancer.

Adult↗
PubMed1995

[Evaluation of the effectiveness of tamoxifen in malignant breast tumors: new approaches].

It has been shown that 17 beta-estradiol stimulates the cycle of phospholipid conversion in the breast tumor cells. The action of tamoxifen on antiestrogen cells is not limited by weakening the stimulating effect of 17 beta-estradiol on the exchange of intracellular phospholipids, but gives rise to a more complicated pattern of changes: inhibited incorporation of 32-P-phosphatidylcholine (PC) and activated exchange of phosphoinositides (PI). The experimental findings of 53 breast tumors have indicated that in 47.2% of cases Tamoxifen alters the PC/PI ratio and causes its 2-fold increase. Such alterations have been found to be induced by the ability of Tamoxifen to suppress the activity of protein kinase C that regulates the synthesis of PC and PI. It is suggested that the revealed capacity of Tamoxifen to change the rate of intracellular phospholipid conversion might be used for evaluating the efficiency of this agent on malignant tumors.

Autoradiography↗
PubMed1994

[Regulation of the cycle of phospholipid turnover in hamster fibroblasts transformed by v-src and N-ras oncogenes].

The phospholipid turnover has been studied in two lines of golden hamster cells: in cells transformed by the Rous sarcoma virus (line HET-SR) and in cells additionally transfected with the activated oncogene N-ras (line HET-SR-N-ras, clone 6). It has been found that HET-SR cells are distinguished by a high level of phosphatidylcholine turnover and a relatively low level of phosphoinositide turnover. Transfection of cells with the activated N-ras (line HET-SR-N-ras) leads to the inhibition of phosphatidylcholine synthesis and activation of phosphoinositide metabolism. Both cell lines preserve their sensitivity to serum growth factors stimulating the rate of phospholipid turnover. In both cell lines dexamethasone decreases the rate of DNA synthesis and inhibits the phosphatidylcholine and phosphoinositide turnover. At the same time, dexamethasone does not influence the predominant activation of phosphatidylcholine synthesis in HET-SR cells or the activation of phosphoinositide synthesis characteristic of HET-SR-N-ras cells. The data obtained suggest that the transmission of the mitogenic signal from growth factor in HET-SR and HET-SR-N-ras cells occurs via the activation of the phospholipid turnover and is controlled by steroid hormones. The role of v-src and N-ras oncogens in the transmission of the mitogenic signal seems to be insignificant; their activity is not controlled by dexamethasone.

Animals↗
PubMed1993

Regulation of phospholipid turnover by steroid hormones in endometrial carcinoma and breast cancer cells.

To study the early effects of steroid hormones on cells we investigated the influence of the sex steroids and tamoxifen on phospholipid turnover in endometrial carcinoma and breast cancer cells. Studies were performed on 19 human uterine adenocarcinomas and 29 breast cancer tumors. Progesterone in a final concentration of 10(-7) mol/l caused a twofold decrease of 32P incorporation into phospholipids (phosphatidylcholine and phosphoinositides) in 85% of the uterine adenocarcinomas where the progesterone receptor (PR) content was more than 100 nmol/kg and only in 30% of the tumors where the PR content was less than 100 nmol/kg. Treatment of the cells with 10(-8) mol/l 17 beta-estradiol or 10(-8) mol/l epidermal growth factor led to an increase in 32P incorporation into phospholipids. Analysis of the hormonal responsiveness of 29 human breast cancers showed that 17 beta-estradiol increased 32P incorporation into phospholipids in 47% of the tumors where the estradiol receptor (ER) content was more than 10 nmol/kg and in 21% of the receptor-negative tumors (ER < 10 nmol/kg) The results show that phospholipid turnover in uterine and breast cells can be regulated by sex steroids. Treatment of the breast cancer cells with the antiestrogen tamoxifen (10(-6) mol/l) led to an increase of 32P incorporation into phosphoinositides and a decrease of 32P incorporation into phosphatidylcholine. Addition of an activator of protein kinase C, i.e. 2 x 10(-7) mol/l 12-0-tetradecanoylphorbol-13-acetate, weakened the inhibitory effect of tamoxifen on phosphatidylcholine turnover. These findings suggest that tamoxifen action can be mediated via an alteration of the growth signal transducing system.

Adenocarcinoma↗
PubMed1993

[The effect of steroid hormones and tamoxifen on the rate of phospholipid turnover in the cells of uterine and breast tumors].

The cycle of phospholipid turnover has been found to be under the negative control of hormonal cytostatics (progesterone) and under the positive control of proliferation stimulants (17 beta-estradiol, epidermal growth factor). Specific changes in the synthesis of phospholipids are shown when tamoxiphen, an antiestrogen and an inhibitor of protein kinase C, was used. The findings suggest that changes in the turnover rate of phospholipids are one of the key stages of steroid action on target cells and may be regarded as an additional criterion of tumor genetic sensibility.

Adenocarcinoma↗
PubMed1993

[The effect of progesterone and tamoxifen on EGF-dependent activation of phospholipid turnover in uterine and breast tumor cells].

The in vitro effects of the epidermal growth factor (EGF) and progesterone on phospholipid turnover in cells of 19 human adenocarcinomas (postsurgical material) have been studied. In 58% of tumours EGF increased the 32P incorporation into two basic cell phospholipids--phosphatidylcholine and phosphoinositides. In EGF-insensitive cells progesterone induced no noticeable changes in the basal level of phospholipid metabolism. However, in 10 out of 11 positively responding to EGF adenocarcinomas progesterone inhibited the EGF-dependent activation of 32P incorporation into the phospholipids already on the 15th min after its addition to the cells. Analysis of effects of EGF and the anti-estrogen drug tamoxifen on phospholipid turnover in 22 human mammary tumours did not reveal any significant differences in tamoxifen effect on tumour cells differing in their sensitivity to EGF. Independently of cell sensitivity to EGF, tamoxifen caused some decrease in the 32P incorporation into phosphatidylcholine but increased the label incorporation into phosphoinositides. Tamoxifen added to tumour cells prestimulated with EGF or 17 beta-estradiol failed to abrogate the effect of these compounds on phospholipid turnover. At the same time, treatment of cells with the protein kinase C activator 12-O-tetradecanoyl-phorbol-13-acetate fully inhibited the effect of tamoxifen on phospholipid metabolism. The results obtained suggest that the EGF-dependent activation of intracellular phospholipid turnover is under the negative control of progesterone. As for tamoxifen, its effect on cells is independent of EGF and consists, apparently, in the inhibition of protein kinase C activity.

Adenocarcinoma↗
PubMed1993

[Biochemical paths for regulating hormone-sensitive cells].

The main causes of alterations in cell sensitivity to steroid hormones were studied during malignant growth and upon ageing. In many cases studied the decreased sensitivity of cells to steroids was reversible and unrelated to changes in the receptor system of the cell. Based on the data obtained, a hypothesis was proposed concerning the multifunctional regulation of cell sensitivity to hormones. Within the framework of this hypothesis the sensitivity of cells to hormones is regulated by both changes in the receptor system responsible for hormonal signal transmission and by changes in the activity of hormone-dependent intracellular enzymatic systems. The role of target cell microenvironment in the formation of the ultimate cell response to hormonal stimuli is discussed.

Aging↗
PubMed1992

Glucocorticoid regulation of phospholipid turnover and protein kinase C activity in mouse hepatoma 22 cells.

Glucocorticoids induce growth inhibition in certain sensitive hepatoma cells. To investigate how glucocorticoids interact with growth-factor-dependent pathways, we studied the effects of dexamethasone (Dex) on the DNA synthesis, protein kinase C (PKC) activity and phospholipid turnover in mouse hepatoma 22 cells. Dex was found to reduce DNA synthesis in slowly growing hepatoma cells, whereas exponentially growing cells were Dex-insensitive. Direct measurements of PKC activity in the hormone-sensitive hepatoma 22 cells showed a rapid inhibition (within 30 min) when treated with Dex. Dex addition to hormone-sensitive but not to hormone-insensitive hepatoma 22 cells for 30 min caused a significant decrease of 32P-incorporation into the major cellular phospholipids: phosphatidylcholine, phosphatidylglycerol and phosphoinositides. At the same time, the analysis of the correlation between changes in PKC activity and phospholipid turnover showed that synthesis of phosphatidylcholine and phosphatidylglycerol was under positive control of PKC activity. The data suggest that suppression of phospholipid turnover in hormone-sensitive hepatoma 22 cells is one of the early events caused by glucocorticoids, whereas the decrease of PKC activity induced by the hormone is mediated, probably, via changes in phospholipid metabolism.

Animals↗
PubMed1992

[Regulation of the phospholipid turnover rate and protein kinase C activity as a necessary stage in the realization of the growth-inhibiting effect of dexamethasone on hepatoma 22 cells].

The role of protein kinase C and phospholipid turnover in the realization of the cytostatic effect of dexamethasone on hormone-sensitive cells of mouse hepatoma 22 has been studied. It was found that dexamethasone added to hepatoma cells induces a rapid (within 30 min) inhibition of the protein kinase C activity with a simultaneous decrease of the 32P incorporation into the major phospholipids (phosphatidylglycerol, phosphatidylcholine, and phosphoinositides). Analysis of correlation between the protein kinase C activity and phospholipid turnover rate revealed that phosphatidylglycerol and phosphatidylcholine synthesis is under the positive control of protein kinase C, whereas that of phosphoinositides is not controlled by the enzyme. A proportional decrease in the rates of metabolism of all the three major phospholipids after addition of the hormone to hepatoma cells suggests that inhibition of phospholipid turnover is one of the primary manifestations of the dexamethasone effect. The hormone-induced decrease in the protein kinase C activity may be regarded as being due to these changes.

Animals↗