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M Platica

Publications and source records attributed to M Platica.

13 recordsLinked to original sources
PubMed2001

Stable lower PAR expression decreased DU145 prostate cancer cell growth in SCID mice.

BACKGROUND: PAR is a novel gene ubiquitously expressed in normal and malignant tissues with a trend towards higher expression in tumor cells. PAR biological function is unknown. Here we report the effect of lowering PAR expression on in vitro and in vivo proliferation of DU145 cells. METHODS: Decreased PAR expression was achieved by stable transfection of DU145 cells with antisense PAR cDNA cloned in pCMV-Script expression vector. The proliferative potential of DU145 transfectants was studied by cell counts, colony formation in soft agar, flow cytometry, and growth in severe combined immunodeficient (SCID) mice. RESULTS: DU145 transfectants exhibited a decreased cell proliferation in tissue culture and a low efficiency of colony formation in soft agar. Flow cytometry revealed an arrest of these cells in G2-M phase of mitotic cycle. A dramatic decrease of tumor growth was observed when DU145 transfectant cells were inoculated in SCID mice, compared with controls. Histological examination of these tumors showed a marked decrease in cell density and in number of mitoses while control tumors showed a high cell density and numerous mitoses. CONCLUSIONS: The data presented here provide the first evidence for PAR gene cellular function and its possible implication in malignant transformation.

Animals↗
PubMed2000

PAR, a novel androgen regulated gene, ubiquitously expressed in normal and malignant cells.

During our work on the mechanism of hormone resistance of prostatic carcinomas, a novel gene that we called PAR (prostate androgen regulated) was isolated from an androgen resistant subline (LNCaP-OM) using a modified representational difference analysis. The complete sequence of the gene cDNA has 1029 nucleotides with a continuous reading frame of 438 bases encoding for 146 amino acids. Its deduced amino acid sequence has motifs for myristoylation and phosphorylation by protein kinase C. The PAR gene was overexpressed in all prostatic carcinoma cell lines studied (LNCaP, DU145, PC3 and LNCaP-OM) compared to the normal prostatic tissue. Furthermore, its expression was higher in androgen resistant prostate cancer lines DU145, PC3 and LNCaP-OM, in comparison to androgen sensitive LNCaP cells. The expression of this gene was down regulated by androgens in androgen sensitive prostate cells, but not in the hormone resistant cell lines. The PAR mRNA was detected in all 29 normal human tissues studied and overexpressed in most (67%) of their malignant counterparts. The PAR expression was higher in MCF7 and T47D breast cancer cell lines, as well as in all primary breast tumors studied compared to their normal tissue counterparts. The biological function of this gene is still unknown, but its ubiquitous expression in normal tissues and its overexpression in some malignancies suggest the PAR involvement in certain basic cellular processes and possibly, in malignant transformation.

Amino Acid Sequence↗
PubMed1992

Pituitary extract causes aggregation and differentiation of rat mammary tumor MTW9/Pl cells.

Alkaline pituitary extracts (PE) of the mammosomatotropic tumor MtTW10 differentiated cultured PRL-independent rat mammary tumor cells MTW9/Pl. Within 24 h, MTW9 cells growing in suspension began to aggregate and adhere to the plastic dish. Cultured dispersed MTW9 cells were undifferentiated, but PE treatment resulted in organoid aggregates that exhibited glandular luminal structures and periodic acid-Schiff-positive material consistent with basement membrane formation. Morphometric examination of organoids demonstrated a reduction in nuclear and cell perimeters compared to those of untreated cells. Electron microscopy showed that the treatment resulted in polarization, nuclear changes, junctional complexes, secretory spaces, microvilli, and basement membrane formation. A disaggregated undifferentiated tumor now appeared as a differentiated adenocarcinoma. PE induced expression of laminin and milk protein, but failed to increase fibronectin expression. Extracts of MTOM (a variant of MtTW10 which secretes little PRL) and bovine pituitary also produced aggregation and adhesion of MTW9. A number of tissue extracts, growth factors, and hormones failed to produce such aggregation. Laminin, but not fibronectin, produced aggregation and adhesion similar to those produced by PE. Cycloheximide inhibited the aggregation effect of PE, but not that of laminin. PE was mitogenic for MTW9, but inhibition of proliferation by vinblastine did not inhibit the aggregation induced by PE. These observations suggest that the pituitary contains a novel factor that stimulates matrix synthesis, resulting in differentiation, possibly laminin induced.

Animals↗
PubMed1991

Role of prolactin in growth of the rat mammary tumor MTW9.

The growth of MTW9 mammary tumors exhibits different degrees of responsiveness to ovariectomy, ranging from sensitivity to resistance. This range of response is a function of time elapsing from tumor inoculation until performance of ovariectomy provided that prolactin (PRL) level is kept continuously high. In vivo studies showed that the MTW9 tumors developed by chronic administration of spiramide were sensitive to ovariectomy by 60 days, but they became resistant to ovariectomy by 100 days. However, when spiramide treatment was discontinued after tumor appearance, the tumors were still sensitive to ovariectomy by 100 days. Chromatofocusing (CF) profile of cytosolic estrogen receptors (ER) correlated with the responsiveness to ovariectomy. A 2-peak profile for tumors sensitive to ovariectomy, and only a one-peak profile for tumors resistant to ovariectomy, were seen. Although the prolactin level in rats bearing the tumors was higher than in the normal rats, no correlation between the PRL level and the change in CF profile of ER over time was seen. Also, these changes could not be correlated with the tumor size. In vitro studies showed that incubation of cytosolic ER from a sensitive tumor (2 peaks) with PRL led to a CF profile with only one peak, characteristic of a resistant tumor. Leupeptin, molybdate and phenylmethylsulfonylfluoride (PMSF) could not prevent this transition. The effect was not reproduced by incubation with growth hormone or progesterone. Our data suggest that PRL, either directly or through intermediates, may play a role in changing the response to hormonal therapy of the mammary tumor MTW9.

Animals↗
PubMed1989

Characterization by chromatofocusing of estrogen receptors from rat mammary tumor MTW9.

The estrogen receptor (ER) from rat mammary tumor MTW9-D, which is sensitive to ovariectomy, could be separated by chromatofocusing (CF) into two peaks specifically binding 3H-estradiol, focusing at pH 6.8 (peak A) and pH 6.0 (peak B). The ER from MTW9-MtT tumor, which is resistant to ovariectomy, presented only one peak, focusing at pH 6.0 (peak B). The peaks presented similar sedimentation coefficients (3.5s) with peak B being slightly larger than peak A. Regardless of the tumor sensitivity to hormonal manipulation, the two peaks presented similar molecular weights as shown by immunostaining of Western blots: a major duplex component of 70 kilodaltons (kd), and single bands at 48, 36, and 35 kd. The bands under 70 kd could be proteolytic products; however, the pattern could not be changed by addition of molybdate, leupeptin, or phenylmethylsulfonylfluoride. The pattern was reproducible in experiments done at different intervals of time or when rechromatofocusing. The peaks presented different isoelectric points: peak A, pH 6.8; peak B, pH 6.0. Also, they had different DNA binding abilities: peak A bound quantitatively to DNA, while peak B bound only 20%. Peak A was always present in tumors responsive to ovariectomy, a fact that suggests this ER component could be a marker for the responsiveness to hormonal therapy.

Animals↗
PubMed1985

Lipopolysaccharide stimulation of plasmacytoma cells.

Various preparations of lipopolysaccharides (LPS) were tested for their effect on 6 plasma tumor cell lines. LPS from Escherichia coli B5:055, Salmonella minnesota 1114, and R7 mutant, as well as the glycolipid from S. minnesota 595 were highly stimulatory on cell suspensions from solid transplantable plasma tumor cells MOPC 315 and MPC11, as measured by thymidine incorporation and cell proliferation. Even nanogram doses were effective. LPS preparations from S. minnesota R5 and endotoxin-free cell wall residues of R5 and R7 mutants of S. minnesota had no stimulatory effect on these cells. In contrast, 4 lines of tissue culture-adapted plasma tumor cells (Adj PC5, HOPC-1, MOPC-21, and MPC11 TC) were not affected by any LPS preparation tested. Lymphosarcoma P1798 cells were also unaffected by these LPS.

Animals↗
PubMed1983

Use of chromatofocusing to distinguish estradiol receptor from ovarian-dependent and -independent rat mammary tumors.

Cytosol estradiol receptor from MTW9-D (ovarian dependent) and MTW9-MtT (ovarian independent) rat mammary tumors were fractionated by chromatofocusing, a procedure which separates proteins on an ion-exchange column as a function of isoelectric point. Receptor from MTW9-D usually fractionated as three peaks with mean pH at peak height of 7.5, 6.8, and 6.0. The intermediate peak at pH 6.8 was present in 90% of MTW9-D tumors examined but in only 20% of MTW9-MtT tumors. Treatment of cytosols with 20 mM sodium molybdate or 50 mM leupeptin did not change the chromatofocusing profiles. The pI 6.8 fraction of receptor bound quantitatively to DNA-cellulose after ammonium sulfate precipitation, while receptor in the other two peaks bound much less. The quantitative binding of a fraction of estradiol receptor characteristic of MTW9-D to DNA is consistent with the greater binding of unfractionated cytosol receptor from MTW9-D to DNA than the binding of receptor from MTW9-MtT. Sucrose gradient analysis of the pI 6.8 receptor showed a sedimentation coefficient slightly less than ovalbumin with a Stokes radius of 26 A as determined by agarose chromatography. The correlation of receptor binding to DNA with response to ovariectomy might make this form of receptor a potential marker of hormonal responsivity in mammary tumors.

Animals↗
PubMed1982

Lipopolysaccharide and pristane-induced peritoneal exudate requirements for plasma tumor cell colony formation.

The role for lipopolysaccharide (LPS) and a pristane-induced peritoneal exudate (PIPE) on the in vitro development of murine plasmacytoma was studied. MOPC-315 cell suspensions showed little tendency for colony formation in a soft agar culture medium. Additions of LPS and PIPE were required for maximal colony formation. The LPS effect was dose-dependent down to nanogram quantities. PIPE prepared from inbred strains of mice not susceptible to pristane-induced plasmacytoma (DBA/2) or from normal peritoneal washings was ineffective. PIPE activity was radioresistant and not transferable by cell-free conditioned medium. Three strains of transplantable plasmacytomas showed colony formation stimulation by LPS plus PIPE, but LPS and PIPE were ineffective with lymphosarcoma P1798.

Animals↗
PubMed1980

Effect of subcutaneously administered 2,6,10,14-tetramethylpentadecane on plasmacytoma growth.

2,6,10,14-Tetramethylpentadecane (pristane), s.c. injected simultaneously with plasmacytoma inocula, enhances the transplantability of tumor cells. The effect is dose and time dependent. The enhancement is shown only by plasmacytoma (MOPC-315 and MPC-11) and not by the murine lymphosarcoma and chondrosarcoma tested. Various mechanisms, such as stress and depression of humoral and cellular immunity, have been considered.

Adrenocorticotropic Hormone↗
PubMed1978

Dithiols simulate endotoxin in the Limulus reaction.

Dithiothreitol, dithioerythritol and bacterial lipopolysaccharides increase optical absorbance and clot Limulus lysate. Purification of dithiothreitol from possible endotoxin contamination by vacuum sublimation or chromatography does not abolish the reaction with lysate. The dithiols reported active here represent the smallest molecules capable of simulating endotoxin in the Limulus test.

Bacterial Toxins↗
PubMed1978

Role of lipopolysaccharide in the production of plasma cell tumors in mice given mineral oil injections.

The lipopolysaccharide (LPS) content of peritoneal fluids of BALB/c mice given mineral oil injections and of normal mice was measured. Peritoneal fluids were passed through DEAE-Bio-Gel columns to remove an inhibitor to the Limulus amebocyte lysate reaction and then were assayed for LPS by a spectrophotometric Limulus amebocyte lysate test. A highly significant difference between control animals and animals given mineral oil injections was found. A clear correlation between LPS concentration and time after first oil injection was shown. P-200 gel chromatography and heat stability of the active material were consistent with the behavior of LPS. The possible role of LPS in the pathogenesis of plasma cell tumor is discussed.

Animals↗