Tomasz Motyl

IGF-I, EGF, and sex steroids regulate autophagy in bovine mammary epithelial cells via the mTOR pathway

Mammary gland growth and involution are based on a dynamic equilibrium between proliferation and apoptosis of mammary epithelial cells (MEC). The main type of cell death responsible for bovine mammary gland involution is apoptosis, but MEC also exhibit morphological features of autophagy. The present study has been undertaken in order to examine factors, which are responsible for the regulation of autophagy in bovine MEC. We used a model of in vitro mammary gland involution known to be dependent on fetal bovine serum (FBS) deficiency in the culture of bovine BME-UV1 cells. We investigated the effects of insulin-like growth factor-1 (IGF-I) and epidermal growth factor (EGF) signaling, as well as sex steroids and rapamycin (a specific inhibitor of mammalian target of rapamycin, mTOR, kinase) on autophagy in the MEC line BME-UV1. Our main focus was on the role of mTOR in the regulation of autophagy by growth factors and hormones. Laser scanning cytometry, electron microscopy, Western-blot analysis, GFP-LC3 reporter-based expression analysis, and LysoTracker Green-related fluorescence were used to determine the activity of autophagy in BME-UV1 cells. We found that FBS deficiency induced both autophagy and apoptosis with the highest intensity of both processes after 48h of MEC exposure to the deficient medium (0.5% FBS). Addition of IGF-I or/and EGF to the FBS-deficient medium clearly diminished autophagy. We also show that IGF-I and EGF are involved in the activation of mTOR in bovine MEC, whereas inhibition of mTOR by rapamycin abrogated the suppressive effects of IGF-I and EGF on autophagy. This suggests that mTOR links IGF-I and EGF signaling in inhibiting the autophagy pathways. Contrary to IGF-I and EGF, 17beta-estradiol and progesterone exerted stimulatory effects on autophagy in bovine MEC. At the same time we observed a suppressive effect of both steroids on mTOR activation/phosphorylation. In conclusion, autophagy in bovine MEC undergoes complex regulation, where its activity is controlled by survival pathways dependent on IGF-I and EGF, which are involved in suppression of autophagy, and by pregnancy steroids, which act as inducers of the process.

Expression of bcl-2 and bax in TGF-β1-induced apoptosis of L1210 leukemic cells

TGF-β1 is a multifunctional regulatory peptide (25 kDa) inducing growth arrest and apoptosis in many normal and neoPlastic cells. In the present study, the involvement of proapoptotic (bax) and antiapototic (bcl-2) genes in the molecular mechanism of TGF-β1-induced apoptosis of L1210 leukemic cells was investigated. Bax transcript was measured using the RT-PCR method with GAPDH as a “housekeeping gene” control, whereas bcl-2 protein was determined using flow cytometry (FITC-conjugated monoclonal anti-bcl-2 antibody and FITC-conjugated mouse anti-IgG1 antibody as a negative control). Apoptosis was evaluated using fluorescence microscopy and flow cytometry after cell staining with DAPI and sulforhodamine or propidium iodide and Hoechst 33342. ROS generation was assessed by flow cytometry using the oxidation-sensitive fluorescent marker C-DCDHF-DA. The response of L1210 leukemic cells to TGF-β1 was two-directional: 1) Partial arrest of the cell cycle at G1-S transition, and 2) induction of apoptotic cell death. TGF-β1 increased the number of leukemic cells with typical morphological features of apoptosis: cell shrinkage, condensation of chromatin, pyknosis and fragmentation of nuclei, followed by secondary necrosis. DNA cleavage led to a decrease of the nuclear DNA content and the appearance of a hypodiploid peak sub-G1 in the DNA histogram. The extraction of lowmolecular weight DNA fragments from apoptotic cells showed that TGF-βl-induced apoptosis concerned first of all the cells from Gt phase. Twophases of intracellular ROS generation in TGF-βl-treated cultures were observed: the first (rapid, 60 min after TGF-β1 administration), and the second (slow, occurring between 24 and 48h of experiment, respectively). The increase of apoptotic cell number in TGF-β1 treated cultures (2 % FCS/RPMI 1640) was associated with the decrease of cell number expressing bcl-2, and with a significant drop of BcI-2 level in the remaining cells after 24h. The dose-dependent relationship between TGF-βl concentration and bcl-2level was nonlinear and described by power series regression. The lowest BcI-2 level was noted at lng/ml of TGF-βl concentration. The increase of Bax mRNA:GAPDH mRNA ratio was observed 3h after TGF-βl (1 ng/ ml) administration to both the maintenance (2 % FCS/RPMI) and growth promoting (10% FCS/RPMI) medium. Regardless of TGF-β1 treatment, the quantity of Bax transcript was dependent on FCS concentration, being higher in the growth promoting medium. The results of this study indicate that bax may function as a primary response gene and together with lowered bcl-2 level may determine the induction of apoptotic process in LU10 leukemic cells exposed to TGF-βl.

Subcellular redistribution of BAX during apoptosis induced by anticancer drugs.

BAX is the 192-amino acid, 21-kDa protein which is ubiquitously distributed in normal tissues and is regarded as a tumor suppressor sensitizing malignant cells to anticancer drugs. In spite of many studies, the molecular mechanism of BAX action is still obscure. In the present study subcellular BAX translocations in human colon adenocarcinoma COLO 205 cells exposed to various anticancer drugs [camptothecin (CPT), etoposide (ETO), staurosporine (STP), 2-chloro-2′-deoxyadenosine (2CdA) and nimesulide (NIM)] was examined. Cells were grown on coverslips under optimal conditions (10% FCS/DMEM) or were stimulated to apoptosis with the drugs examined. Laser scanning cytometry was applied for the quantitative analysis of BAX expression, and distribution in the cytoplasmic (BAX Cf) and nuclear (BAX Nf) area. BAX maximal pixel (BAX MP), the parameter corresponding to aggregation of BAX in the cell, was also measured. All examined drugs increased the number of cells with high BAX MP, reaching the peak at 60 min after drug administration. The most pronounced effect was in the case of 2CdA, CPT and STP. The increase in BAX MP was observed only when antibody recognizing the 43-61 amino acid sequence was used. When antibody binding the N-terminal epitope (11-30 amino acid sequence) was applied, the number of cells expressing high BAX MP significantly decreased. These results indicate that apoptotic stimuli delivered by anticancer drugs led to aggregation of BAX in cancer cells, which is dependent on BAX activation by its cleavage at the N-terminal epitope and exposure of the BH3 domain. It was shown that BAX Nf increased in cells treated with CPT, STP, ETO, 2CdA and NIM, whereas BAX Cf rose after STP and NIM. The increase in BAX Nf and, occurring in most treatments, the increase in the BAX Nf:Cf ratio indicates a BAX shift from the cytoplasm to the nucleus. Furthermore, staining with different antibodies showed that only the activated form of BAX was translocated to the nucleus. Immunoelectron microscopy revealed that CPT-induced apoptosis was associated with translocation of BAX from the cytosol to organellar membranes (mitochondrial, Golgi apparatus and endoplasmic reticulum) and via nuclear envelope pores to the nucleus, occurring within 60-180 min of cell exposure to the drug. The subcellular translocations of BAX preceded in time the appearance of morphological symptoms of apoptosis. In conclusion, (i) in spite of different molecular mechanisms of apoptosis induction by the anticancer drugs examined, BAX remains a common link in the chain of reactions leading to cell death, and (ii) BAX activation and subcellular translocations from the cytosol to organellar membranes and nucleus are key cellular responses to drugs bearing proapoptotic properties.

Comparison of metabolic effects of EGF, TGF-α, and TGF-β1 in primary culture of fetal bovine myoblasts and rat L6 myoblasts

Abstract 1. 1. Comparative studies of EGF, TGF-α, and TGF-βl action on the synthesis of DNA and cellular proteins in rat L6 myogenic cells and fetal bovine myoblasts demonstrated considerable differences between particular growth factors, dependent on dose and target cells. 2. 2. Among examined growth factors only EGF exerted mitostimulatory action, more pronounced at lower concentrations. EGF, progressively with dose, stimulated protein synthesis much more effectively in fetal bovine myoblasts than in L6 cells. 3. 3. The dynamics of stimulation of protein synthesis by TGF-α was greater than by EGF in both examined types of cell cultures. 4. 4. The maximal response of fetal bovine myoblasts to TGF-α in a concentration of 100 ng/ml reached 370%, whereas EGF in a 10 times higher concentration stimulated protein synthesis only to 123% of control. 5. 5. In contrast to EGF, TGF-α significantly inhibits DNA synthesis. Inhibition of the mitogenic response with simultaneous stimulation of protein synthesis by TGF-α may indicate changes toward cell differentiation. 6. 6. TGF-β 1 in smallest concentration inhibits both DNA and protein synthesis. The suppressive action of TGF-β 1 was more distinct in fetal bovine myoblasts than in the L6 cell line. 7. 7. Increasing concentrations of TGF-β l diminished its inhibitory effect, even leading to stimulation of protein synthesis at higher doses in L6 myoblasts.

Transcriptomic signature of cell lines isolated from canine mammary adenocarcinoma metastases to lungs

Metastasis is a final step in the progression of mammary gland cancer, usually leading to death. Potentially, a molecular signature of metastasis can be defined via comparison of primary tumors with their metastases. Currently, there is no data in the literature regarding the molecular portrait of metastases in dogs and only few reports regarding human cancer. This is the first report describing the transcriptomic signature of canine cancer metastatic cells. Two adenocarcinoma cell lines isolated from the canine mammary gland (CMT-W1 and CMT-W2) were compared with cell lines isolated from their lung metastases (CMT-W1M and CMT-W2M) with regards to the following cytometric parameters: cell cycle, ploidy, Bcl-2 expression, susceptibility to induced apoptosis, and transcriptomic profile. Cytometric analyses revealed significant differences in cell cycle and antiapoptotic potential between the examined cells. Using oligonucleotide microarrays, we found 104 up-regulated genes in the metastatic cell line CMT-W1M and 21 up-regulated genes in the primary CMT-W1 cell line. We also found 83 up-regulated genes in the CMT-W2M cell line and only 21 up-regulated genes in the CMT-W2 cell line. Among the up-regulated genes in both metastatic cell lines, we found 15 common genes. These differently expressed genes are involved mainly in signal transduction, cell structure and motility, nucleic acid metabolism, developmental processing, and apoptosis (GHSR, RASSF1, ARF1GAP, WDR74, SMOC2,SFRP4, DIAPH1, FSCN1, ALX4, SNX15, PLD2, WNT7B, POU6F2, NKG7, andPOLR2F). Seven ofthem are involved in a cellular pathway dependent on ghrelin via growth hormone secretagogue receptor (GHSR). Our results suggest that this pathway may be essential for mammary cancer cells to have a metastatic potential.

EXPRESSION OF BAX IN CELL NUCLEUS AFTER EXPERIMENTALLY INDUCED APOPTOSIS REVEALED BY IMMUNOGOLD AND EMBEDMENT‐FREE ELECTRON MICROSCOPY

The unique combination of immunocytochemistry with embedment‐free electron microscopy was applied for precise and specific localisation of BAX in the human colon adenocarcinoma COLO 205 cell line stimulated to undergo apoptosis by camptothecin (DNA topoisomerase I inhibitor). Camptothecin‐induced apoptosis was associated with redistribution of BAX from cytosol to organelle membranes: mitochondria, Golgi apparatus, endoplasmic reticulum and via nuclear envelope pores to the nucleus, occurring within 60–180min of cell exposure to the drug. An increase in BAX immunoreactivity on fine filaments and the lamina‐pore complex of the nuclear matrix was also observed. The increase in BAX expression in the nuclear area of camptothecin‐treated COLO 205 cells was confirmed by quantitative analysis using laser scanning cytometry. The subcellular translocations of BAX preceded the appearance of any morphological symptoms of apoptosis.

Regulation of Autophagy in Bovine Mammary Epithelial Cells

The bovine mammary gland undergoes intensive remodeling during the lactation cycle, and the escalation of this process is observed during dry periods. The main type of cell death responsible for bovine mammary gland involution is apoptosis; however, there are also a lot of cells exhibiting morphological features of autophagy during drying off. Our in vitro and in vivo studies of bovine mammary gland physiology suggest that the enhanced process of autophagy, observed at the end of lactation and during dry periods, is the result of: (1) decreased level of lactogenic hormones (GH, IGF-I), (2) decreased GH-R and IGF-IRα expression, (3) increased expression of auto/paracrine apoptogenic peptides (IGFBPs, TGF-β1), (4) increased influence of sex steroids (17β-estradiol and progesterone) and (5) enhanced competition between the intensively developing fetus and the mother organism for nutritional and bioactive compounds. The above conditions may create a state of temporary malnutrition of mammary epithelial cells, which forces the cells to the induction of autophagy, as a mechanism for stabilizing intracellular supplies of energy and amino acids, especially during the enhanced activity of apoptogenic factors. Addendum to: Apoptosis and Autophagy in Mammary Gland Remodeling and Breast Cancer Chemotherapy T. Motyl, B. Gajkowska, J. Zarzyńska, M. Gajewska and M. Lamparska-Przybysz J Physiol Pharmacol 2006; 57:17-32

Expression and role of PGP, BCRP, MRP1 and MRP3 in multidrug resistance of canine mammary cancer cells

BackgroundIn both women and female dogs, the most prevalent type of malignant neoplasm is the spontaneous mammary tumor. In dogs, half of these are malignant. The treatment of choice for the canine patients is surgical mastectomy. Unfortunately, it often fails in high-risk, locally invasive mammary tumors as of during the time of the surgery the micro-metastases are present. Moreover, there are neither large studies conducting to prove of the benefit from the chemotherapy in dogs nor established chemotherapy treatment protocols available. Additionally, the effectiveness of each individual chemotherapeutic agent and drug resistance of canine mammary cancer have not yet been characterized. That has become the aim of our study, to assess the expression of PGP, BCRP, MRP1 and MRP3 in canine mammary cancer cell lines and to investigate their role in cancer resistance to vinblastine, cisplatin and cyclophosphamide with using RNAi approach.ResultsThe results suggested that in canine mammary cancer, the vinblastine efflux was mediated by PGP and MRP1 proteins, cisplatin efflux was mediated by all four examined efflux pumps (PGP, BCRP, MRP1 and MRP3), whereas cyclophosphamide resistance was related to BCRP activity. RNAi silencing of these efflux pumps significantly decreased IC50 doses of the examined drugs in canine mammary carcinoma cells.ConclusionsOur results have indicated the treatment of cells involving use of the siRNA targeting efflux pumps could be a beneficial approach in the future.

Kinetics of Smac/DIABLO release from mitochondria during apoptosis of MCF-7 breast cancer cells

Smac/DIABLO, a pro‐apoptotic protein released from mitochondrial intermembrane space during apoptosis, promotes caspase activation by IAPs neutralization. The kinetics and molecular mechanism of Smac/DIABLO release from mitochondria has remained obscure. Homeostatic confocal microscopy, for the first time, showed the precise kinetics of Smac/DIABLO release from mitochondria during CPT‐induced apoptosis in living MCF‐7 cells. The time pattern of Smac/DIABLO escape from mitochondria comprised two phases: the initial phase of gradual protein release, followed by the second phase of plateau, appearing after 24 min of cell exposure to the drug. A similar pattern was observed during oxidative stress. The dynamics of Smac/DIABLO redistribution was confirmed by different methods: traditional confocal microscopy, immunoelectron microscopy and laser scanning cytometry. The inhibition of m‐calpain prevented Smac/DIABLO release from mitochondria, which confirmed the involvement of Bax in the process. Acquired results indicate that CPT treatment triggers Bax‐dependent release of Smac/DIABLO from mitochondria simultaneously with the efflux of cytochrome c.

Effects of hormones and growth factors on TGF-β1 expression in bovine mammary epithelial cells

The decline of mammary epithelial cell (MEC) number during mammary gland involution in the cow is due to inhibition of proliferation and induction of apoptosis. Transforming growth factor-beta 1 (TGF-beta1) belongs to a group of intramammary auto/paracrine inhibitors of bovine MEC growth and inducers of apoptosis. However, the mechanism responsible for the regulation of TGF-beta1 expression in MEC is not known. The present study examined the effect of the hormones, growth hormone (GH), somatostatin (STS), 17-beta oestradiol (E2), progesterone (P4), as well as the growth factors, insulin-like growth factor I (IGF-I) and epidermal growth factor (EGF), on TGF-beta1 expression in the bovine MEC lines, BME-UV1 and MAC-T. The model of apoptosis in bovine mammary gland in vitro was applied by reduction of fetal bovine serum (FBS) (from 10% to 2% or 0.5% FBS) in the cell environment to show the relationship between TGF-beta1 expression and apoptosis in bovine MEC. RT-PCR, Western blot and laser scanning cytometry (LSC) were used for analysis of TGF-beta1 transcript and protein level as well as apoptosis and cell cycle in examined MEC. In this model of apoptosis, FBS deficiency (mimicking the naturally occurring decline in the access of bioactive compounds and nutrients at the end of lactation and dry period) was associated with increased TGF-beta1 expression at the level of transcript and protein, induction of apoptosis and inhibition of cell cycle. Exogenous TGF-beta1, IGF-I, EGF and GH inhibited FBS-deficiency-stimulated TGF-beta1 expression. The suppressive effect of GH was reversed when cells were maintained longer in FBS-deficient medium. In general, STS, E2 and P4 increased TGF-beta1 expression. However, this effect was dependent on hormone concentration and cell line. BME-UV1 cells were much more responsive to the peptides, GH, STS, IGF-I and EGF, whereas MAC-T cells were more responsive to the steroid sex hormones: E2 and P4.