Biomedical subjects

M Guo

Publications and source records attributed to M Guo.

At least 55 records · Page 3Linked to original sources

PubMed2001

[Studies on characteristics of kinetics and metabolic shift of genetically engineered yeast Pichia pastoris in high-density chemostat cultivation].

Kinetics and metabolic shift of DNA recombinant yeast Pichia pastoris was studied in high-density chemostat cultivation in which the glycerol was used as a limited substrate. The experimental results showed that (1) cell optical density (OD600) of Pichia pastoris was linear with its dry cell weight (DCW) and wet cell weight (WCW), and reached 100 OD600 = 128.3 g WCW/L or 100 OD600 = 22.9 g DCW/L; (2) The relationship of specific growth rate (mu) and residual concentration of glycerol is accorded with Monod Equation, to obtain mu = mumax S/(Ks + S), where mumax = 0.366 h-1, Ks = 0.1823 g/L. The maximum cell yield of glycerol substrate YG = 0.54 g/g, growth maintaining coefficient m = 0.0069 g/(g.h), The cell yield of oxygen YX/O2 = 30.96 g/moL, and the optimum theoretical dilution rate Dm = 0.341 h-1 by parameter inference; (3) With specific growth rate (mu) increasing, glycerol metablic flux shifts linearly from glycogenesis and hexosephosphate pathways to glycolysis and tricarboxylic acid cycle pathways on basis of variations of consumption rate of NH3.H2O and respiratory quotient value.

Biotechnology↗

PubMed2001

[Effects of isocarbophos on the integrity of epidermic cell membrane of human skin].

OBJECTIVE: To investigate the effects of isocarbophos, a new and highly effective organophosphorus pesticide on the membranes of keratinocytes. METHODS: The epidermic cells of human skin cultured in the medium were adopted as a biological material. The activity of lactate dehydrogenase (LDH) was used as an indicator. We tested the activities of LDH and alkaline phosphatase (ALP) in the medium in different isocarbophos dosage conditions. RESULTS: It was found that the activity of LDH in the medium decreased with the increase of isocarbophos dosage. The LDH activities of the dosage groups were statistically different from those of the positive and negative groups. The ALP activities were of no significant difference between the groups. CONCLUSION: The above findings reveal that isocarbophos does not damage the membranes of keratinocytes directly, however it inhibits the LDH of human skin keratinocytes; thus it is suggested that isocarbophos like most organophosphorus pesticides used widely can pass through the intact human skin and poison the body before the skin is damaged. Therefore, protection during work hours is of paramount importance.

Alkaline Phosphatase↗

PubMed2001

[Postlaryngectomy peristomal recurrence].

OBJECTIVE: To study the etiopathology, diagnosis and management of peristomal recurrence after laryngectomy, and the prevention of peristomal recurrence. METHODS: Retrospective analysis of clinical management and outcomes of 16 cases of peristomal recurrence. RESULTS: The subglottic extension of laryngeal cancer and peritracheal metastasis may result in peristomal recurrence. The stomal resection with mediastinal dissections and the use of the pectoralis major myocutaneous flap were done. The survival period of 11 cases surgically treated was longer than that of 5 cases irradiated or untreated. CONCLUSION: Surgical management would improve the survival, but overall prognosis is dismal and attention should be focused on prevention. It is evident that early diagnosis of stomal recurrences will yield good results.

Aged↗

PubMed2001

[Effects of direct current on vibration of cochlear basilar membrane].

OBJECTIVE: To explore the effects of direct current on vibration of cochlear basilar membrane. METHODS: A small hole with a diameter about 0.4 mm, which had the distance of 2.4 mm from round window niche, was made on cochlear basic turn of guinea pig for measuring the velocity of basilar membrane in vivo. On the superior and inferior edge of the measuring window, holes were made on the scala tympani and scala vestibuli for insert stimulating electrode that was made of platinum-iridium. The basilar membrane vibration was elicited by tone and the effect of direct current stimuli were observed by Laser Doppler interference velocimeter. RESULTS: The velocity of basilar membrane vibration elicited with tone was increased significantly when positive current was delivered to scala vestibuli and the velocity was decreased on the contrary. CONCLUSION: The positive endolymphatic potential is essential for cochlea to transit sound to nerve impulse in physiological condition. It is benefit to enhance the gain of cochlear amplifier when the positive potential is increased on the top of outer hair cells, but the extrinsic negative potential should significantly decrease the gain of cochlear amplifier.

Animals↗

PubMed2000

The dendritic cell receptor for endocytosis, DEC-205, can recycle and enhance antigen presentation via major histocompatibility complex class II-positive lysosomal compartments.

Many receptors for endocytosis recycle into and out of cells through early endosomes. We now find in dendritic cells that the DEC-205 multilectin receptor targets late endosomes or lysosomes rich in major histocompatibility complex class II (MHC II) products, whereas the homologous macrophage mannose receptor (MMR), as expected, is found in more peripheral endosomes. To analyze this finding, the cytosolic tails of DEC-205 and MMR were fused to the external domain of the CD16 Fcgamma receptor and studied in stable L cell transfectants. The two cytosolic domains each mediated rapid uptake of human immunoglobulin (Ig)G followed by recycling of intact CD16 to the cell surface. However, the DEC-205 tail recycled the CD16 through MHC II-positive late endosomal/lysosomal vacuoles and also mediated a 100-fold increase in antigen presentation. The mechanism of late endosomal targeting, which occurred in the absence of human IgG, involved two functional regions: a membrane-proximal region with a coated pit sequence for uptake, and a distal region with an EDE triad for the unusual deeper targeting. Therefore, the DEC-205 cytosolic domain mediates a new pathway of receptor-mediated endocytosis that entails efficient recycling through late endosomes and a greatly enhanced efficiency of antigen presentation to CD4(+) T cells.

Adsorption↗

PubMed2000

Suppression of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-mediated aryl hydrocarbon receptor transformation and CYP1A1 induction by the phosphatidylinositol 3-kinase inhibitor 2-(4-morpholinyl)-8-phenyl-4H-1- benzopyran-4-one (LY294002).

Numerous flavonoids are ligands of the aryl hydrocarbon receptor (AHR) and function as AHR antagonists and/or agonists. LY294002 [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one] is a widely used inhibitor of phosphatidylinositol 3-kinase (PI 3-kinase), and is structurally related to members of the flavonoid family. Concentrations of LY294002 >/= 10 microM were cytostatic, but not cytotoxic, to cultures of the immortalized human breast epithelial cell line MCF10A-Neo. Treatment of MCF10A-Neo cultures with the AHR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) stimulated the transcriptional activation of CYP1A1, as monitored by measurements of steady-state CYP1A1 mRNA. Pretreatment of cultures with >/= 10 microM LY294002 suppressed the TCDD activation of CYP1A1 (IC(50) approximately 10 microM). Electrophoretic mobility shift assays employing rat liver cytosol demonstrated that concentrations of LY294002 </= 400 microM did not transform the AHR into a DNA-binding species. However, the addition of LY294002 to cytosol just prior to TCDD addition completely suppressed AHR transformation by TCDD (IC(50) approximately 35 microM). The PI 3-kinase inhibitor Wortmannin was weakly cytostatic, but not cytotoxic to MCF10A-Neo cultures at concentrations </= 500 nM. Exposure of cultures to Wortmannin (10-500 nM) did not suppress TCDD activation of CYP1A1. Analyses of the phosphorylation status of Akt-1, an in vivo substrate of PI 3-kinase, demonstrated that concentrations of LY294002 >/= 50 microM and Wortmannin >/= 10 nM completely suppressed PI 3-kinase activity. Hence, the ability of LY294002 to suppress TCDD-dependent activation of CYP1A1 is unrelated to PI 3-kinase inhibition. Instead, this activity reflects LY294002 functioning as an AHR antagonist. Furthermore, most of the cytostatic activity of LY294002 towards MCF10A-Neo cells is unrelated to the inhibition of PI 3-kinase.

Androstadienes↗

PubMed2000

Ti(IV) uptake and release by human serum transferrin and recognition of Ti(IV)-transferrin by cancer cells: understanding the mechanism of action of the anticancer drug titanocene dichloride.

The organometallic anticancer agent titanocene dichloride, Cp(2)TiCl(2), is now in phase II clinical trials as an anticancer drug, but its mechanism of action is poorly understood. We show here that the interactions of Cp(2)TiCl(2) with human serum transferrin (hTF) and that of Ti(2)-hTF with adenosine triphosphate (ATP) have characteristics that could allow transferrin to act as a mediator for titanium delivery to tumor cells. Such reactions may therefore be important to the anticancer activity of this new class of drugs. Cp(2)TiCl(2) reacts rapidly with human apo-transferrin under physiological conditions (100 mM NaCl, 25 mM bicarbonate, and 4 mM phosphate, pH 7.4) with carbonate as a synergistic anion. The Cp ligands are released from the drug. Two-dimensional [(1)H, (13)C] NMR studies of epsilon-[(13)C]Met-hTF show that Ti(IV) loads the C-lobe first followed by the N-lobe and binds in the specific Fe(III) sites. The protein conformational changes induced by Ti(IV) appear to be similar to those induced by Fe(III). Carbonate can act as a synergistic anion in Ti(2)-hTF but does not appear to be essential. A specific Ti(IV)-hTF adduct is formed even in the absence of bicarbonate. When the pH of Ti(2)-hTF solutions is lowered, no Ti(IV) is released at the endosomal pH of ca. 5.0-5.5, but one Ti(IV) dissociates between pH 4.5-2.0. In contrast, in the presence of 1 mM ATP, all Ti(IV) is readily released from both lobes when the pH is lowered from 7.0 to 4.5. Moreover, Fe(III) displaces Ti(IV) rapidly from the C-lobe of Ti(2)-hTF (<5 min) but only slowly (days) from the N-lobe. Thus, the species Fe(C)Ti(N)-hTF might also provide a route for Ti(IV) entry into tumor cells via the transferrin receptor. Ti(2)-hTF effectively blocked cell uptake of radiolabeled (59)Fe-hTF into BeWo cells, a human placental choriocarcinoma cell line in culture. These results imply that titanium transferrin might be recognized by the transferrin receptor and be taken up into cancer cells.

Adenosine Triphosphate↗

PubMed2000

Activation of caspase-3 in molt4 cells by apoptosis-inducing nucleosides from CD57(+)HLA-DR(bright) natural suppressor cell line.

Apoptosis-inducing nucleosides (AINs), which were released and isolated from CD57(+)HLA-DR(bright) natural suppressor (57.DR-NS) cell line derived from human decidual tissue, induced apoptosis in Molt4 cells. The addition of caspase-3 inhibitor into the reaction blocked the cleavage of caspase-3 and apoptosis in Molt4 cells treated with AINs, detected by flow cytometrical or spectrofluorometrical analysis and DNA fragmentation assay. Furthermore, by means of immunoblotting, the processing of caspase-3 was shown with the appearance of their catalytically active subunits of 20 and 11 kDa during the generation of apoptosis in Molt4 cells treated with AINs. This processing of caspase-3 into active subunits was also blocked by the addition of caspase-3 inhibitor. Thus, it was definitely revealed that the activation of caspase-3 was a key feature in the caspase cascade of AINs-induced apoptosis in Molt4 cells.

Apoptosis↗

PubMed2000

The catalytic subunit of DNA-dependent protein kinase selectively regulates p53-dependent apoptosis but not cell-cycle arrest.

DNA damage induced by ionizing radiation (IR) activates p53, leading to the regulation of downstream pathways that control cell-cycle progression and apoptosis. However, the mechanisms for the IR-induced p53 activation and the differential activation of pathways downstream of p53 are unclear. Here we provide evidence that the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) serves as an upstream effector for p53 activation in response to IR, linking DNA damage to apoptosis. DNA-PKcs knockout (DNA-PKcs-/-) mice were exposed to whole-body IR, and the cell-cycle and apoptotic responses were examined in their thymuses. Our data show that IR induction of apoptosis and Bax expression, both mediated via p53, was significantly suppressed in the thymocytes of DNA-PKcs-/- mice. In contrast, IR-induced cell-cycle arrest and p21 expression were normal. Thus, DNA-PKcs deficiency selectively disrupts p53-dependent apoptosis but not cell-cycle arrest. We also confirmed previous findings that p21 induction was attenuated and cell-cycle arrest was defective in the thymoctyes of whole body-irradiated Atm-/- mice, but the apoptotic response was unperturbed. Taken together, our results support a model in which the upstream effectors DNA-PKcs and Atm selectively activate p53 to differentially regulate cell-cycle and apoptotic responses. Whereas Atm selects for cell-cycle arrest but not apoptosis, DNA-PKcs selects for apoptosis but not cell-cycle arrest.

Animals↗

PubMed2000

Fast and quantitative high-performance liquid chromatography method for the determination of 9-fluorenylmethoxycarbonyl release from solid-phase synthesis resins.

Base catalyzed cleavage of 9-fluorenylmethoxycarbonyl (FMOC) group and subsequent analysis by UV spectrophotometry is a commonly used technique for measuring the loading of functional groups on solid supports. Recent works suggest that using 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) instead of piperidine makes it possible to use gas chromatography for quantitation, but due to the long deprotection time used, the method is not high-throughput. We observed that the dibenzofulvene released after DBU deprotection could be measured by reversed-phase (RP) HPLC. We have optimized the concentration of DBU as well as the time of the deprotection and coupled with a fast RP-HPLC separation results in a highly reproducible, high-throughput method. The measured loading correspond well with the manufacturer's data on several commercial resins. Using this method we have quantitated the amine loading on several polystyrene resins and we have found that the total amount of functional group can be more than twice the amount of the available ones. We concluded that the differences were the function of the resin loading as well as the level of crosslinking.

Chromatography, High Pressure Liquid↗

PubMed2000

Stereoselective formation of seven-coordinate titanium(IV) monomer and dimer complexes of ethylenebis(o-hydroxyphenyl)glycine.

Reactions between the antitumor agent titanocene dichloride (Cp2TiCl2) and the hexadentate ligand N,N'-ethylenebis-(o-hydroxyphenylglycine) (H4ehpg) have been investigated in aqueous solution and the solid state. The racemic ligands give crystals of the monomer [Ti(ehpg)(H2O)] x (11/3)H2O (1), while the meso ligand gives the oxo-bridged dimer [[Ti(Hehpg)(H2O)]2O] x 13H2O (2). Complex 1 crystallizes in the monoclinic space group C2/c with a = 24.149(4) A, b = 14.143(3) A, c = 19.487(3) A, beta = 105.371(13) degrees, V = 6417.7(19) A3, Z = 12, and R(F) = 0.0499 for 4,428 independent reflections having I > 2sigma(I), and contains seven-coordinate pentagonal-bipyramidal TiIV with two axial phenolate ligands (Ti-O, 1.869(2) A). The pentagonal plane contains the two N-atoms at 2.210(2) A, two carboxylate O-atoms at 2.061(2) A, and a water molecule (Ti-OH2, 2.091(3) A). Complex 2 crystallizes as an oxygen-bridged dimer in the triclinic space group P-1 with a = 12.521(6) A, b = 14.085(7) A, c = 16.635(8) A, alpha = 80.93(2) degrees beta = 69.23(2) degrees, gamma = 64.33(2) degrees , V = 2472(2) A3, Z = 4, and R(F) = 0.0580 for 5956 independent reflections having I > 2sigma(I). Each seven-coordinate, pentagonal-bipyramidal TiIV has a bridging oxide and a phenolate as axial ligands. The pentagonal plane donors are H2O, two carboxylate O-atoms, and two NH groups, which form H-bonds to O-atoms both in the same half-molecule (O...N, 2.93-3.13 A) and in the other half-molecule (O...N, 2.73-2.75 A); the second phenoxyl group of each Hehpg ligand is protonated and not coordinated to TiIV, but H-bonds to a nearby amine proton (O...N, 2.73-2.75 A) from the same ligand and to a nearby H2O (O...O, 2.68 A). In contrast to all previously reported crystalline metal-EHPG complexes containing racemic ligands, in which the N(S,S)C(R,R) or N(R,R)C(S,S) form is present, complex 1 unexpectedly contains the N(S,S)C(S,S) and N(R,R)C(R,R) forms. This is attributed to the presence of ring strain in seven-coordinate TiIV complexes. Moreover, the rac ligands selectively form crystals of monomeric 1, while the meso ligand selectively forms crystals of the dimer 2 (N(R,R)C(R,S) or N(S,S)C(S,R)). Complexes 1 and 2 exhibit phenolate-to-TiIV charge-transfer bands near 387 nm, and 2D NMR studies indicate that the structures of 1 and 2 in solution are similar to those in the solid state. Complex 1 is stable over the pH range 1.0-7.0, while 2 is stable only between pH 2.5 and pH 5.5. Cp2TiCl2 reacts with EHPG at pH* 7.0 to give complex 1 with a t 1/2 of ca. 50 min (298 K), but complex 2 was not formed at this pH* value. At pH* 3.7, the reaction is very slow: 1 forms with a half-life of ca. 2.5 d, and 2 after ca. 1 week at ambient temperature. The relevance of these data to the possible role of serum transferrin as a mediator for the delivery of TiIV to tumor cells is discussed.

Antineoplastic Agents↗

PubMed2000

A monoclonal antibody to the DEC-205 endocytosis receptor on human dendritic cells.

DEC-205 is a multilectin receptor for adsorptive endocytosis, expressed in mouse dendritic cells (DC) and some epithelia. DEC-205 is homologous to the macrophage mannose receptor (MMR). A cDNA for murine DEC-205 was used to identify 3 overlapping human DEC-205 clones from a lymphocyte library. The human homologue is a transmembrane protein of 1722 aminoacids with 10 externally disposed C-type lectin domains having 77% identity to the mouse counterpart. The NH(2) terminal cysteine-rich and fibronectin type II domains were expressed and used to immunize mice. A hybridoma, MG38, which specifically recognized the immunogen was obtained from a DEC-205 knockout mouse. The antibody precipitated a 205 kD protein from metabolically labeled, monocyte-derived DCs. MG38 labeled mature monocyte-derived DCs but showed weak or no labeling of other peripheral blood mononuclear cells. In tissue sections, MG38 identified DEC-205 on thymic cortical epithelium and DCs in the thymic medulla and tonsillar T cell areas. In contrast, an anti-MMR antibody stained DEC-205 negative, macrophages in the thymus cortex, the trabeculae of the thymus and tonsil, as well as efferent lymphatics in the tonsil. Therefore, the MG38 anti-DEC-205 antibody is useful for identifying DCs and reveals clear differences in sites where MMR and DEC-205 are expressed in lymphoid tissues.

Animals↗

PubMed2000

Identification and characterization of human immunoglobulin G Fc receptors of Fusobacterium nucleatum.

Several human pathogens express components which can bind to the Fc portion of immunoglobulins. This study was undertaken to characterize the human immunoglobulin G (IgG) Fc-binding activity of Fusobacterium nucleatum, a suspected pathogen involved in periodontal diseases. Fc-binding activity was detected using whole-cell, cell envelope and outer membrane fractions, and it was found to be associated with polypeptides of 40 kDa and 42 kDa, respectively. Amino terminal sequencing of these components revealed them to be homologous to the bacterial porin encoded by fomA gene. Further sequencing of internal peptide fragments obtained by CNBr cleavage suggested that these two proteins are probably isoforms. In summary, we show that a porin-like protein on the surface of F. nucleatum can bind the Fc fragment of the human immunoglobulin G, and this protein may act as a virulence factor to facilitate this bacterium in evading host immune surveillance system.

Bacterial Outer Membrane Proteins↗

PubMed2000

Blastomycosis: organ involvement and etiologic diagnosis. A review of 123 patients from Mississippi.

Blastomycosis can only be diagnosed through the identification of the yeasts of Blastomyces dermatitidis in body fluids, tissues, or cultured material. The charts from 123 patients treated for blastomycosis at the University of Mississippi Medical Center from January 1980 through May 2000 were reviewed to determine the role of wet preparation, cytology, histology, and culture in diagnosing this fungal disease. Cytology uncovered the etiologic agent in 56.1% of all cases and in 71.8% of pulmonary cases. Cytology also was the first method to disclose the fungus in 57.7% of pulmonary cases. Sputum was the cytology specimen examined in 51% of the patients. In 69 patients with lung involvement, pulmonary cytology was positive in 97% of cases. Wet preparation was the second method to most commonly uncover the fungus in 37.4% of all cases. Histology was the third method with 32.5% of positive cases. Cultures were positive in 64.2% of all cases but they were the first to detect the fungus in only 3.2% of all patients. There was pulmonary involvement in 87% of patients, cutaneous involvement in 20%, osseous involvement in 15%, and central nervous involvement in 3%. In the medical literature the relative proportion of pulmonary versus disseminated disease clearly increased in series reported after 1959. Proportionally to the pattern of patients admitted to the University of Mississippi Medical Center, there is a clear predominance of black males among patients with blastomycosis followed by black females. White females constitute the sex/ethnic group least affected by this fungal disease.

Adolescent↗

PubMed2000

Human T cell leukemia cell death by apoptosis-inducing nucleosides from CD57(+) HLA-DR(bright) natural suppressor cell line.

Apoptosis-inducing nucleosides (AINs) released from CD57( +) HLA-DR(bright) natural suppressor (57.DR-NS) cell line, derived from human decidual tissue, were isolated from 57.DR-NS cell culture supernatant by the combination of thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). Apoptotic cell death was strongly induced in human T cell leukemia Molt4 cells treated with AINs, absolutely depending on DNA strand breaks, with activation of the caspase cascade, especially caspase-3. The administration of AINs to Molt4 tumor-bearing severe combined immunodeficiency (SCID) mice resulted in drastic suppression of tumor growth, with a decrease of tumor size and the appearance of apoptotic signals in tumor tissue. Thus, AINs are candidates for development as anticancer agents.

Animals↗

PubMed2000

Isolation and characterization of a human neutrophil aggregation defective mutant of Fusobacterium nucleatum.

Fusobacterium nucleatum is known to adhere to human polymorphonuclear neutrophils (PMNs) and cause them to aggregate. In this study, we isolated a spontaneously occurring aggregation defective (AGG(-)) mutant and this mutant will be used for future study of the interactions between this bacterium and human PMN. Genomic DNA fingerprinting by random-primed polymerase chain reaction method revealed a difference between the parent strain and the AGG(-) mutant. This mutant also showed an altered phenotype in both microbicidal and phagocytic assays, suggesting that the bacterial factor involved in the aggregation may also be very important for the phagocytosis and, subsequently, the killing by human PMNs. Further study of this mutant may help to clarify the molecular mechanisms of the interaction between this pathogen and human PMNs.

Bacterial Adhesion↗

PubMed2000

Mycobacterium smegmatis has two pyrazinamidase enzymes, PncA and pzaA.

The Mycobacterium smegmatis pncA gene, encoding nicotinamidase/pyrazinamidase, was identified. While it was similar to counterparts from other mycobacteria, the M. smegmatis PncA had little homology to the other M. smegmatis pyrazinamidase/nicotinamidase, encoded by the pzaA gene. Transformation of Mycobacterium bovis strain BCG with M. smegmatis pncA or pzaA conferred susceptibility to pyrazinamide.

Amidohydrolases↗

PubMed2000

Phorbol ester-induced production of cytostatic factors by normal and oncogenic Ha-ras-transformed human breast cell lines.

The effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) on cell cycle progression were examined in the human breast cell line MCF10A-Neo and a derivative line which expresses a Ha-ras oncogene (MCF10A-NeoT cells). Exposure of MCF10A-Neo cultures to TPA induced a G(1) arrest that lasted approximately 16-24 h (IC(50) approximately 0.5 nM). TPA-treated cultures produced a cytostatic conditioned medium. Cytostatic activity was detectable within 1 h of TPA treatment, peaked 3-7 h later and disappeared between 16 and 24 h post-treatment. However, cytostatic conditioned medium could be quickly regenerated by re-feeding previously treated cultures with new medium. Removal of latent transforming growth factor beta (TGF beta) from the culture medium, supplementing the culture medium with anti-TGFbeta or soluble TGF beta(II) receptor, or pre-absorption of conditioned medium with anti-TGF beta all reduced the cytostatic effects of TPA or conditioned medium on MCF10A-Neo proliferation by approximately 50%. Co-treatment with the serine protease inhibitors aprotinin or plasminogen activator inhibitor-1 also suppressed the cytostatic activity of TPA approximately 50%. Conditioned medium isolated from TPA-treated MCF10A-Neo cultures was transiently cytostatic to MCF10A-NeoT cells. The proliferation of MCF10A-NeoT cultures, in contrast to MCF10A-Neo cells, was suppressed at least 72 h following TPA exposure. Conditioned medium isolated from TPA-treated MCF10A-NeoT cultures also suppressed MCF10A-NeoT proliferation for approximately 72 h, but suppressed MCF10A-Neo proliferation for <24 h. These studies suggest that TPA quickly activates proteolytic processes in MCF10A-Neo cells leading to the activation of latent TGF beta supplied by the serum in the culture medium. TPA also stimulates the production of an additional cytostatic factor(s) which signals via a mechanism not involving the TGF beta(II) receptor. Lastly, expression of an activated Ha-ras oncogene alters both the types of cytostatic factors produced following TPA treatment and responsiveness to these factors.

Antineoplastic Agents↗