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M Landström

Publications and source records attributed to M Landström.

At least 19 recordsLinked to original sources
PubMed2001

Phosphorylation of Smad7 at Ser-249 does not interfere with its inhibitory role in transforming growth factor-beta-dependent signaling but affects Smad7-dependent transcriptional activation.

Smad proteins are major components in the intracellular signaling pathway of transforming growth factor-beta (TGF-beta), and phosphorylation is an important mechanism in regulation of their functions. Smad7 was identified as a potent inhibitor of TGF-beta-dependent signaling. We have identified serine 249 in Smad7 as a major phosphorylation site, the phosphorylation of which was not affected by TGF-beta1. Abrogation of the phosphorylation by substitution of Ser-249 with alanine or aspartic acid residues did not affect the ability of Smad7 to inhibit TGF-beta1 and BMP7 signaling. No differences were found in the stability or in the intracellular distribution of Smad7 mutants compared with the wild-type molecule. However, Smad7 fused to the DNA-binding domain of GAL4 induced transcription from a reporter with mutated TATA minimal promoter in a Ser-249-dependent manner. Moreover, a reporter with the SV40 minimal promoter was inhibited by GAL4-Smad7, and this effect was also dependent on Ser-249 phosphorylation. The amplitude of effects on transcriptional regulation was dependent on cell type. Our results suggest that phosphorylation of Smad7, unlike phosphorylation of the receptor-regulated Smads, does not regulate TGF-beta signaling but rather affects TGF-beta-independent effects of Smad7 on transcriptional regulation.

3T3 Cells↗
PubMed2000

Smad7 mediates apoptosis induced by transforming growth factor beta in prostatic carcinoma cells.

Transforming growth factor beta (TGF-beta) is an important regulator of apoptosis in some cell types, but the underlying molecular mechanisms are largely unknown. TGF-beta signals through type I and type II receptors and downstream effector proteins, termed Smads. TGF-beta induces the phosphorylation of Smad2 and Smad3 (receptor-activated Smads) which associate with Smad4 and translocate to the nucleus, where they regulate gene transcription [1]. Smad7 protein is induced by TGF-beta1 and has been classified as an inhibitory Smad. Smad7 prevents phosphorylation of receptor-activated Smads, thereby inhibiting TGF-beta-induced signaling responses [1]. Smad7 expression is increased in rat prostatic epithelial cells undergoing apoptosis as a result of castration [2]. Here we have shown that TGF-beta1 treatment or ectopic expression of Smad7 in human prostatic carcinoma cells (PC-3U) induces apoptosis. Furthermore, TGF-beta1-induced apoptosis was prevented by inhibition of Smad7 expression, by antisense mRNA in stably transfected cell lines or upon transient transfection with antisense oligonucleotides in several investigated cell lines. These findings provide evidence for a new effector function for Smad7 in TGF-beta1 signaling.

Amino Acid Chloromethyl Ketones↗
PubMed2000

Effects of tobacco smoke on tumor growth and radiation response of dunning R3327 prostate adenocarcinoma in rats.

BACKGROUND: The influence of tobacco smoke has been investigated on the growth rate and histology of prostate cancer, both in untreated tumors and in those subjected to fractionated irradiation. METHODS: Twenty-five rats were implanted bilaterally with Dunning R3327 tumor fragments at 10 weeks of age. Approximately 3 months later, they were randomly allocated to two groups, one of which was exposed to tobacco smoke for an hour each day, 5 days a week. Three weeks later the groups were further subdivided into two groups which acted as controls or were subjected to 5 daily doses of 6 Gy. The tumors were measured weekly to construct growth curves. At a fixed time, 9 weeks or 20 weeks later, the animals were sacrificed and the tumors were removed for histological evaluation of the tissue composition. Sections from each tumor were scored in a morphometric analysis of the fraction of the area of tumor that was occupied by (epithelial) tumor cells, by stroma, or by luminal spaces. In addition, the density of mast cells was assessed in adjacent sections stained with toluidine blue. RESULTS: Smoking caused only minor changes in the growth rates of both the control and the irradiated tumors. At the cellular level, smoking caused a small but significant increase in the fraction of tumor cells relative to controls. Irradiation also caused a small but significant decrease in tumor cell fraction compared to controls, even after 20 weeks of regrowth. This difference was reduced in the smoking and irradiation group. The main difference observed was in the mast cell numbers. Smoking caused a 4-fold increase in mast-cell density. Irradiation caused an even greater increase (25-fold). The combination of smoking and irradiation resulted in an intermediate increase (10-fold). CONCLUSIONS: Long-term smoke exposure can slightly alter the growth rate and morphology of Dunning R3327 rat prostatic adenocarcinoma, but our study does not show a negative effect on the outcome of radiation treatment of this tumor model. We have also demonstrated a highly elevated number of mast cells in the irradiated group, and have shown that smoke exposure significantly depressed the radiation-induced enhancement of the number of mast cells.

Adenocarcinoma↗
PubMed1999

Expression of Smad proteins in human colorectal cancer.

Escape from transforming growth factor-beta (TGF-beta)-induced inhibition of proliferation has been observed in many tumor cells and may contribute to loss of growth control. Smad proteins have been identified as major components in the intracellular signaling of TGF-beta family members. In this study, we examined the expression of receptor-activated, common-mediator and inhibitory Smads by immunohistochemistry in human colorectal cancers. We found increased expression of receptor-activated Smads in a fraction of the tumor cells, while no immunostaining for Smad2, Smad3 or Smad5 and only occasional staining for Smad1/8 was found in epithelial mucosa of normal colon. No or only weak staining for receptor-activated Smads, common-mediator Smad4 and inhibitory Smads was observed in the tumor stroma. Common-mediator Smad4 and inhibitory Smads were detected in cells of both tumor and normal tissues. We observed a distinct pattern of Smad4 immunostaining of epithelial cells along colon crypts, with high expression in zones of terminal differentiation. Our data show selective up-regulation of receptor-activated Smad proteins in human colorectal cancers and suggest involvement of Smad4 in differentiation and apoptosis of surface epithelial cells of normal crypts.

Amino Acid Sequence↗
PubMed1999

Increased smad expression and activation are associated with apoptosis in normal and malignant prostate after castration.

Transforming growth factor (TGF)-beta1 is induced in the prostate after castration and has been implicated in apoptosis of epithelial cells during involution. TGF-beta1-mediated receptor activation induces phosphorylation of Smad2 and Smad3, which form complexes with Smad4, that translocate to the nucleus to regulate transcription of target genes. Smad6 and Smad7 antagonize the action of signal-transducing Smads. We have examined the immunohistochemical expression of different Smad molecules in the epithelium of rat ventral prostate before and after castration, in androgen-sensitive Dunning R3327 PAP prostatic tumor cells from untreated and castrated rats, and after treatment with estrogen. In the ventral prostate, a significant increase of phosphorylated Smad2 (P-Smad2) was observed after castration. In prostatic tumor cells we observed an increased expression of Smad2 and P-Smad2 after treatment. The levels of Smad3 and, in particular, Smad4 were enhanced in the normal ventral prostate, as well as in the tumors after castration. Interestingly, Smad6 and Smad7 expression was also up-regulated in cells with increased Smad2 activation. The staining for Smad2, P-Smad2, Smad3, Smad4, and Smad7 was nuclear in some cells and was present in areas with a large number of apoptotic cells identified by various morphological criteria, formation of apoptotic bodies and, in adjacent sections, by terminal deoxynucleotidyl transferase-mediated nick end labeling assay. Our results suggest that the signal transduction pathway for TGF-beta, leading to apoptosis, is activated in the normal prostate after castration and in the tumor model after castration, without or with estrogen treatment.

Animals↗
PubMed1998

Transforming growth factor beta1 induces nuclear export of inhibitory Smad7.

Transforming growth factor beta (TGF-beta) signals from membrane to nucleus through serine/threonine kinase receptors and their downstream effector molecules, termed Smad proteins. Recently, Smad6 and Smad7 were identified, which antagonize TGF-beta family signaling by preventing the activation of signal-transducing Smad complexes. Here we report that Smad7, but not Smad6, inhibits TGF-beta1-induced growth inhibition and the expression of immediate early response genes, including Smad7. Interestingly, in the absence of ligand, Smad7 was found to be predominantly localized in the nucleus, whereas Smad7 accumulated in the cytoplasm upon TGF-beta receptor activation. The latter is in accordance with the physical association of Smad7 with the ligand-activated TGF-beta receptor complex in the cell membrane. Whereas the ectopically expressed C-terminal domain of Smad7 was also exported from the nucleus to the cytoplasm upon TGF-beta challenge, a Smad7 mutant with a small deletion at the C terminus or only the N-terminal domain of Smad7 was localized mainly in the cytoplasm in the absence or presence of ligand. This suggests that an intact Mad homology 2 domain is important for nuclear localization of Smad7. The nuclear localization of Smad7 suggests a functional role distinct from its antagonistic effect in receptor-mediated Smad activation.

Animals↗
PubMed1998

Inhibitory effects of soy and rye diets on the development of Dunning R3327 prostate adenocarcinoma in rats.

METHODS: Dunning R3327 PAP prostate tumors were transplanted in 125 rats, the rats were divided into five groups, and tumor development was examined for 24 weeks during treatment with diets containing 33% of soy flour (SD), rye bran (RB), heat-treated rye bran (HRB), or rye endosperm (RE). RESULTS: In the SD, RB, and HRB groups, significantly fewer palpable tumors and lower tumor volume were detected 14 and 16 weeks after transplantation when compared with the control, fiber-free dietary (FF) group. The body weight was lower 16 weeks after tumor transplantation in the RB and HRB groups when compared with the control group (P < 0.05). Rats in the RB and the HRB groups had a significant lower energy intake than the FF group during the first metabolic observation period, 3-6 weeks after tumor transplantation (P < 0.05), whereas the energy intake was the same in all groups during the second metabolic observation period, 13-16 weeks after tumor transplantation. However, when the tumor volume was adjusted for the body weight of the animals, there were still significant lower tumor volumes in the SD, RB, and HRB groups compared with the FF group (P < 0.05). A significant increase in daily urinary excretion of the isoflavonoids, daidzein, O-desmethylangolensin, equol, and Genistein, was observed in the rats fed SD, and of the ligands enterolactone and enterodiol in the rats fed RB and HRB during both metabolic periods. There were no differences in testosterone levels between the groups. CONCLUSIONS: The present study shows that SD inhibits implanted prostate cancer growth. Although RB and HRB had a protective effect, further studies are needed to exclude the possibility that a low energy intake played a role in this respect. The results suggest that phytoestrogens (isoflavonoids and ligands), may be responsible for the delayed prostate tumor growth.

Adenocarcinoma↗
PubMed1998

The response of Dunning R3327 prostatic adenocarcinoma to IL-2, histamine and radiation.

A syngeneic, androgen-sensitive Dunning R3327 rat prostatic adenocarcinoma was transplanted bilaterally in the flanks of male Copenhagen Fisher rats. Approximately 3 months after implantation, when the tumours had a median volume of 150 mm3, one group of rats was treated with histamine alone (4 mg kg(-1) subcutaneously on week days), another group with human recombinant interleukin 2 (IL-2) alone (425 IU kg(-1) continuous infusion) and a third group with both histamine and IL-2 during 6 weeks. Tumours on one flank were irradiated (6 Gy once daily for 3 days to a total dose of 18 Gy) beginning 1 week after the onset of treatment with histamine and/or IL-2. The contralateral tumour served as the intra-animal control. The tumour volumes were determined weekly. The growth curves showed that all three drug treatments were effective in delaying growth, but when used individually did not cause tumour shrinkage. Radiation was the most effective single agent, but when used alone the shrinkage did not occur until 2 weeks after irradiation. When combined with the drugs, more rapid and extensive growth delay and/or shrinkage was seen. The growth curves showed clear differences between the different treatments. The combination of the three agents was the most effective of all. The most striking difference between radiation alone and radiation plus biotherapy was the time at which a tumour response was detectable. Thus, active biotherapy alone and especially in a combination with histamine and radiotherapy warrants further investigation as a potential therapeutic approach to prostate cancer.

Adenocarcinoma↗
PubMed1997

Combined castration and fractionated radiotherapy in an experimental prostatic adenocarcinoma.

PURPOSE: The present study using the Dunning R3327-PAP rat prostatic adenocarcinoma model was designed to study the effect on tumor growth of castration prior to or after irradiation with 20-25 Gy as compared with either irradiation or castration alone. METHODS AND MATERIALS: Rats were bilaterally orchidectomized. During the irradiation procedure the nonanesthetized animals were held in a metallic frame with a strong cotton net and they were observed by means of a video camera. The suboptimal irradiation dose was given once daily with a 4-MeV linear accelerator, 4-5 Gy/fraction, during 5 consecutive days. Tumor volumes and rat weights were followed. At the end point of the study the animals were sacrificed and the tumors were morphometrically analyzed. RESULTS: The combination of irradiation and castration delayed tumor regrowth better than irradiation alone with the same suboptimal dose. Castration before irradiation delayed tumor regrowth more efficiently than castration after irradiation. However, castration alone delayed tumor regrowth even more effectively than suboptimal irradiation doses combined with castration. CONCLUSIONS: In combination with suboptimal irradiation neoadjuvant androgen deprivation was more inhibitory to rat prostatic adenocarcinoma regrowth than adjuvant androgen deprivation. Irradiation with suboptimal doses combined with castration may cause an earlier relapse to androgen-independent tumor growth than castration alone.

Adenocarcinoma↗
PubMed1997

Apoptosis in rat prostatic adenocarcinoma is associated with rapid infiltration of cytotoxic T-cells and activated macrophages.

Rats transplanted with the androgen-sensitive, syngeneic Dunning R3327 PAP prostatic tumor were castrated and treated with estrogen or vehicle for 4, 12 and 24 hr and for 6 weeks. Tumor growth was retarded by castration and further inhibited by estrogen. Immediately after castration, an increased number of activated macrophages and T-cells were found in parallel with increasing apoptotic tumor cells. Administration of an immunosuppressive drug, FK 506, abolished the growth-inhibitory effects of castration and estrogen. The tumor growth rate correlated negatively with the number of R73- and OX8-positive T-cells and NK cells and with the percentage of ED3-positive macrophages. There was a positive correlation between the percentage of TdT-mediated-dUTP nick end labeling (TUNEL)-positive apoptotic cells and that of ED3-positive cells. Our results suggest that apoptosis of prostatic carcinoma cells induced by endocrine treatment in vivo is partly due to a rapid infiltration by immunocompetent cells.

Adenocarcinoma↗
PubMed1996

Estrogen induces apoptosis in a rat prostatic adenocarcinoma: association with an increased expression of TGF-beta 1 and its type-I and type-II receptors.

Rats transplanted with the androgen-sensitive Dunning R3327 PAP prostatic adenocarcinoma were castrated and treated with either estrogen or vehicle alone for short periods (4 hr, 12 hr, 24 hr) and for 6 weeks. In these tumors the expression of TGF-beta 1, TGF-beta type-I and type-II receptors (TGF-beta RI, TGF-beta RII) was examined by immunohistochemistry. Apoptotic cells were identified by in situ nick and labelling (TUNEL). Tumor growth was retarded by castration and even more by additive estrogen treatment. The epithelium of the untreated tumors stained weakly for TGF-beta 1 and TGF-beta RI, but TGF-beta RII was not detected. Castration induced moderate TGF-beta 1 immunoreactivity in a major part of the glandular epithelium after 24 hr. After 12 hr already, castration plus estrogen resulted in an intense staining for TGF-beta 1 in the basal epithelial cells, some of which also showed an apoptotic appearance. The percentage of cells having stained positive for TGF-beta 1 was significantly higher in the estrogen-treated groups than in the castrated group after 12 hr, and its elevated TGF-beta 1 level remained at 6 weeks. Notably, the increased immunoexpression of TGF-beta 1 occurred before the onset of induction of apoptosis. In parallel with the upregulation of TGF-beta 1 after castration, the expression of its receptors. TGF-beta RI and RII, was induced and was further enhanced by the additive estrogen treatment. The number of intensely stained TGF-beta 1 tumor cells showed a strong correlation with the number of apoptotic tumor cells identified by TUNEL in the whole material. Furthermore, TGF-beta 1 immunoreactivity co-localized with the presence of apoptotic cells in the estrogen-treated tumors at 6 weeks after castration.

Activin Receptors, Type I↗
PubMed1995

Differentiation-stage specific expression of oncoprotein 18 in human and rat prostatic adenocarcinoma.

Oncoprotein 18 (Op18) is an intracellular phosphoprotein that has been shown to be overexpression in a number of human malignancies. In the present report we have studied the pattern of Op18 expression on normal, hyperplastic, and malignant prostatic tissue as well as in rat prostatic tumor lines. One of the objectives of the present work was to establish whether the level of Op18 expression can be used as a prognostic marker in human prostatic adenocarcinoma. To that end, sections from normal, hyperplastic, and malignant human prostatic tissue were examined by immunohistochemistry for expression of Op18. In the normal and hyperplastic prostate, Op18 expression was observed in basal glandular epithelial cells, whereas the columnar luminal epithelial cells were not stained by the anti Op18 antibodies. In highly differentiated prostatic cancers occasional epithelial cells were stained, while in poorly differentiated tumors most of the epithelial cells contained Op18 immunoreactivity. The staining pattern was similar in the primary prostatic tumor and in the regional lymph node metastases. Most importantly, a limited survey of prostatic cancer patient samples (n = 40) showed a significant correlation between the fraction of Op18 immunoreactive cells and survival. Studies of a rat prostatic tumor model, showed that only a few cells were stained in the highly differentiated Dunning R3327PAP tumor, while most cells were stained in the anaplastic AT1 rat prostatic tumor. Interestingly, castration of rats resulted in an increased Op18 immunoreactivity, within 14 days, in the highly differentiated rat R3327PAP prostatic tumor. In conclusion, the level of Op18 expression seems to be related to cellular differentiation, histological grade, and survival in prostatic cancers. These findings show that Op18 immunoreactivity may be useful as a prognostic marker in prostatic cancer. In addition it may help in the differentiation between highly differentiated prostatic tumors and non-malignant conditions.

Adenocarcinoma↗
PubMed1994

Prostatic tumor regrowth after initially successful castration therapy may be related to a decreased apoptotic cell death rate.

Castration of rats transplanted with the androgen-sensitive Dunning R3327-PAP prostatic tumor results initially in a reduction of tumor growth, but after some time, some of the tumors start to grow again. The relapsed, androgen-insensitive PAP tumor shows a dedifferentiated morphology. In the present study, we examined whether this androgen-independent tumor regrowth was due to an increased cell proliferation rate or to a reduction of the number of tumor cells dying by apoptosis. Nine rats (with 18 tumors) were castrated and followed for 16 to 20 weeks. Six of the tumors increased their volume markedly (relapsed), while 12 remained relatively stable (nonrelapsed). The mitotic index and apoptotic index for epithelial cells were examined by light microscopy. Tumor growth rate correlated negatively both to the apoptotic index identified by morphological criteria (RS = -0.82; P < 0.0001) and to the apoptotic index identified by in situ end labeling (RS = -0.83; P < 0.0001). The tumor growth rate percentage did not correlate to the mitotic index, and it was negatively correlated (RS = -0.62; P < 0.01) to the number of cells immunostained for proliferating cell nuclear antigen. It is suggested that one initial event during the androgen-independent prostatic tumor regrowth in the PAP relapse model might be a reduction of the number of tumor cells being depleted by apoptosis, rather than an increase of cell proliferation rate.

Animals↗
PubMed1994

Estrogen treatment postpones the castration-induced dedifferentiation of Dunning R3327-PAP prostatic adenocarcinoma.

Male Copenhagen x Fisher F1 rats, transplanted with the androgen-sensitive Dunning R3327 PAP rat prostatic adenocarcinoma, were castrated when tumor volumes were approximately 1300 mm3. The rats were thereafter followed with measurements of tumor volume. Castration stopped tumor growth, but some of the tumors started to regrow after 7-36 weeks. These tumors relapsing from castration treatment were now considered to be androgen-insensitive. In this study, we defined relapse as the time when the tumor volume had increased to 200% of the volume at the time for castration. At this time, the rats were treated either with estradiol-17 beta (E2, 50 micrograms s.c. daily) or vehicle for 8 weeks. After this period, tumor morphology was examined. The tumors in the vehicle-treated group were heterogeneous, and both highly and more dedifferentiated parts were present. The tumor growth rate was correlated to the epithelial cell nuclear size and its variance, and to the mitotic index. In the E2-treated group, tumor growth rate was retarded throughout the treatment period, and dedifferentiated tumor areas were rare. Estrogen treatment resulted in a reduction of nuclear area and mitotic index, a changed nuclear shape, and an increased apoptotic index compared to that in vehicle-treated tumors. By castration, it is possible to induce an alteration of the androgen-sensitive Dunning R3327 PAP tumor phenotype to an androgen-insensitive tumor with an altered morphology. Estradiol-17 beta apparently inhibits not only the growth, but also postpones the castration-induced dedifferentiation of the tumor.

Adenocarcinoma↗
PubMed1992

Effects of 6-methylene progesterone on growth, morphology, and blood flow of the Dunning R3327 prostatic adenocarcinoma.

Copenhagen x Fisher F1 rats were implanted with the androgen-dependent Dunning R3327 prostatic adenocarcinoma. When the tumors had median volumes of ca 470 mm3, the rats were castrated and/or treated with 6-methylene-4-pregnene-3,20-dione (6MP) in different doses. Tumor growth inhibition occurred in all castrated and treated groups, with decrease in volume of the epithelial compartment in the intact group. Tumor volumes at the highest dose level of 6MP equalled those observed in the castrate group. Plasma levels of testosterone were within the normal range. The administration of 6MP surprisingly induced an increment of tumor blood flow in the castrate group. Also in castrated and testosterone-supplemented animals, 6MP induced a reduction of prostatic tumor growth. Through the castration-like effect on tumor growth, the use of 6MP may represent an attractive alternative to castration for treatment of androgen-responsive prostate cancer.

Adenocarcinoma↗
PubMed1992

Estrogen treatment of Dunning tumors in castrated rats: qualitative and quantitative morphology.

Adult male rats bearing the Dunning R3327 prostatic carcinoma were randomized to the following treatments: intact controls, castration, and castration + estrogen. After a study period for 6 weeks the rats were killed and the tumors were analyzed morphometrically to determine the amount of epithelium, stroma, and connective tissue fibers in the tumors, and the nuclear size of large stromal cells. Cryostat sections were analyzed with immunohistochemistry using a panel of antibodies against cytokeratins, desmin, vimentin, fibronectin and collagens. Addition of estrogen to castration resulted in an inhibition of tumor growth. The expression of cytokeratin 14 (a marker for basal myoepithelial cells) was reduced, but the expression of cytokeratin 18 (a marker for the luminal epithelial cells) was unaffected by estrogen. The amounts of collagen I, III and fibronectin (plasma and cellular types) were increased in the stroma, and the nuclear size of large stromal cells was also increased by estrogen. It is concluded that castration + estrogen treatment has effects in the epithelium and stroma of Dunning tumors that are qualitatively and quantitatively different from the effects of castration alone.

Adenocarcinoma↗