Biomedical subjects

O Larsson

Publications and source records attributed to O Larsson.

At least 37 records · Page 2Linked to original sources

PubMed2001

Association of HLA class I and class II antigen expression and mortality in uveal melanoma.

PURPOSE: Malignant transformation of cells is frequently associated with abnormalities in human leukocyte antigen (HLA) expression. These abnormalities may play a role in the clinical course of the disease, because HLA antigens mediate interactions of tumor cells with T cells and NK cells. Uveal melanoma is a highly malignant tumor of the eye and is characterized by a hematogenic spread to the liver. Little is known about the role of HLA expression in progression of this malignant disease. METHODS: In the present study HLA class I antigen, beta(2)-microglobulin (beta(2)-m), and HLA class II antigen expression was analyzed in primary uveal melanoma lesions by immunoperoxidase staining with monoclonal antibodies of 65 archival clinical samples. The results were correlated with the clinical course of the disease. RESULTS: HLA class I antigen expression and beta(2)-m expression were downregulated in 40 and 35 lesions, respectively. HLA class II antigens were expressed in 30 lesions. Patients with high HLA class I, including beta(2)-m, and HLA class II antigen expression in their primary melanoma lesions had a significantly decreased survival (P = 0.009, P < 0.001, and P = 0.006, respectively). CONCLUSIONS: The findings argue against a major role of cytotoxic T-lymphocyte (CTL)-mediated control of tumor growth in the clinical course of uveal melanoma and are compatible with a potential role of NK-cell-mediated control of hematogenic metastatic spread.

Adult↗

PubMed2000

Increased expression of insulin-like growth factor I receptor in malignant cells expressing aberrant p53: functional impact.

We investigated the functional impact of p53 on insulin-like growth factor I receptor (IGF-IR) expression in malignant cells. Using the BL-41tsp53-2 cell line, a transfectant carrying temperature-sensitive (ts) p53 and endogenous mutant p53 (codon 248), we demonstrated a drastic down-regulation of plasma membrane-bound IGF-IRs on induction of wild-type p53. However, a similar response was obtained by treatment of BL-41tsp53-2 cells expressing mutant ts p53 with a p53 antisense oligonucleotide. Thus, even if the negative effect of wild-type p53 predominates under a competitive condition, these data indicate that mutant p53 may be important for up-regulation of IGF-IR. To further elucidate this issue, three melanoma cell lines (BE, SK-MEL-5, and SK-MEL-28) that overexpressed p53 were investigated. The BE cell line has a "hot spot" mutation (codon 248) and expresses only codon 248-mutant p53. SK-MEL-28 has a point mutation at codon 145. SK-MEL-5 cells did not exhibit any p53 mutations, but the absence of p21Waf1 expression suggested functionally aberrant p53. Our data suggest that interaction with Mdm-2 may underlie p53 inactivation in these cells. Using p53 antisense oligonucleotides, we demonstrated a substantial down-regulation of cell surface expression of IGF-IR proteins in all melanoma cell lines after 24 h. This was paralleled by decreased tyrosine phosphorylation of IGF-IR and growth arrest, and, subsequently, massive cell death was observed (this was also seen in BL-41tsp53-2 cells with mutant conformation of ts p53). Taken together, our results suggest that up-regulation of IGF-IR as a result of expression of aberrant p53 may be important for the growth and survival of malignant cells.

Acetylcysteine↗

PubMed2000

A link between basic fibroblast growth factor (bFGF) and EWS/FLI-1 in Ewing's sarcoma cells.

The EWS/FLI-1 fusion gene is characteristic of most cases of Ewing's sarcoma and has been shown to be crucial for tumor transformation and cell growth. In this study we demonstrate a drastic down-regulation of the EWS/FLI-1 protein, and a growth arrest, following serum depletion of Ewing's sarcoma cells. This indicates that growth factor circuits may be involved in regulation of the fusion gene product. Of four different growth factors tested, basic fibroblast growth factor (bFGF) was found to be of particular significance. In fact, upon treatment of serum-depleted cells with bFGF, expression of the EWS/FLI-1 protein and growth of the Ewing's sarcoma cells were restored. In addition, a bFGF-neutralizing antibody, which was confirmed to inhibit FGF receptor (FGFR) phosphorylation, caused down-regulation of EWS/FLI-1. Experiments using specific cell cycle blockers (thymidine and colcemide) suggest that EWS/FLI-1 is directly linked to bFGF stimulation, and not indirectly to cell proliferation. We also demonstrated expression of FGFRs in several tumor samples of Ewing's sarcoma. Taken together, our data suggest that expression of FGFR is a common feature of Ewing's sarcoma and, in particular, that the bFGF pathway may be important for the maintenance of a malignant phenotype of Ewing's sarcoma cells through up-regulating the EWS/FLI-1 protein. Oncogene (2000) 19, 4298 - 4301

Adenocarcinoma↗

PubMed2000

Tamoxifen-induced cell death in malignant melanoma cells: possible involvement of the insulin-like growth factor-1 (IGF-1) pathway.

Recent data indicate that the estrogen receptor (ER) blocker tamoxifen (TAM) can induce cell death in malignant melanoma cells. However, as shown in the present study and several other studies melanoma cells usually do not express classical ERs. In the present study we investigated whether the cytotoxic effect of TAM on melanoma cells could depend on interference with the expression or function of the insulin-like growth factor-1 receptor (IGF-1R), a plasma membrane receptor important for cell survival in this tumor cell type. Several melanoma cell lines were included in the analysis. Administration of TAM at a concentration of 15 microm or more resulted in cell death of the melanoma cells within 48 h. TAM treatment was correlated to a slight to moderate inhibition of IGF-1 binding to IGF-1R. Since it has been reported that TAM can increase the release of IGF binding proteins (IGFBPs) we then investigated whether this mechanism could underly the decreased IGF-1 binding. However, we could demonstrate that the amount of released IGFBPs were unchanged or decreased in TAM-treated cells. Whereas TAM did not have any strong effect on IGF-1 binding and the expression of IGF-1R at the cell surface, it was was found to efficently block tyrosine phosphorylation of IGF-1R beta-subunit. Taken together, our data suggest that TAM-induced cytotoxicity of malignant melanoma cells can be due to inactivation of IGF-1R.

Antineoplastic Agents, Hormonal↗

PubMed2000

Trends in mortality from malignant melanoma in Sweden, 1970-1996.

BACKGROUND: The rise in melanoma-related mortality in Sweden has been less pronounced than the increase in incidence. Interventional activities aimed at early detection may have contributed to this discrepancy. METHODS: Individuals with malignant melanoma as the underlying cause of death between 1970 and 1996 (n = 7177) formed the basis of this study. Annual age-standardized mortality rates were calculated using the direct method of standardization with the Swedish population of 1970 as reference. Temporal trends in the standardized rates were evaluated using a log-linear model. The effects of age, period, and cohort on the mortality trends were estimated using a Poisson regression model. RESULTS: Since the mid-1980s, melanoma-related mortality in Sweden has leveled off, with no further increase during the last 10-15 years. The contribution to the mortality from noncutaneous melanoma was proportionally stable (20-25%) during the studied period. In females, a significant decrease in mortality from cutaneous melanoma was shown for the period of 1987-1996 with an estimated annual decrease of -2.3% (95% confidence interval: -4.3 to -0.3). This trend appeared to be more pronounced in the Stockholm-Gotland region. The observed trends were best explained with the age-period model in both genders. CONCLUSIONS: Melanoma-related mortality in Sweden has leveled off since the mid-1980s. During the period 1987-1996, a statistically significant downward trend was observed for females. This trend coincides with increased preventional activities.

Adult↗

PubMed2000

Silanized nucleic acids: a general platform for DNA immobilization.

We have developed a method for simultaneous deposition and covalent cross-linking of oligonucleotide or PCR products on unmodified glass surfaces. By covalently conjugating an active silyl moiety onto oligonucleotides or cDNA in solutions we have generated a new class of modified nucleic acids, namely silanized nucleic acids. Such silanized molecules can be immobilized instantly onto glass surfaces after manual or automated deposition. This method provides a simple and rapid, yet very efficient, solution to the immobilization of prefabricated oligonucleotides and DNA for chip production.

Cross-Linking Reagents↗

PubMed2000

Rapid Ca2+ influx and diacylglycerol synthesis in growth hormone-mediated islet beta -cell mitogenesis.

Growth hormone (GH) is an important mitogenic stimulus for the insulin-producing beta-cell. We investigated the effects of GH on Ca(2+) handling and diacylglycerol (DAG) and cAMP formation in the beta-cell. GH elicited a rapid increase in the cytoplasmic free [Ca(2+)], which required extracellular Ca(2+) and was also blocked by pertussis toxin or protein kinase C (PKC) inhibition. GH also elevated islet DAG content, which should lead to PKC activation. Pertussis toxin and PKC inhibitors obliterated the mitogenicity of GH, suggesting involvement of GTP-binding proteins. PKC activation stimulated beta-cell proliferation, and it also activated phospholipase D. Islet cAMP content was not elevated by GH. Addition of a specific protein kinase A antagonist failed to influence the mitogenicity of GH, whereas a stimulatory cAMP agonist stimulated beta-cell replication. We conclude that GH rapidly increases the beta-cell cytoplasmic free [Ca(2+)] and also evokes a similar increase in DAG content via a phosphatidylcholine-specific phospholipase C, but does not affect mitogen-activated protein kinases, phospholipase D, or the cAMP signaling pathway. This rise in DAG may be of importance in translation of the stimulatory signal of GH into a proliferative response by the beta-cell, which seems to occur through GTP-binding proteins and PKC-dependent mechanisms.

Animals↗

PubMed2000

A prospective population-based study of cutaneous malignant melanoma of the head and neck.

UNLABELLED: OBJECTIVES/HYPOTHESIS For cutaneous malignant melanoma (CMM) of the head and neck, neither prognostic factors in population-based groups, nor outcome with respect to surgical resection margins is clear. Therefore, we analyzed data in a regional registry to align treatment results for CMM of the head and neck with prognosis and survival times. STUDY DESIGN: Patient material collected prospectively for an 18-year period in a Swedish cancer registry underwent statistical analyses to establish the most reliable prognostic factors and the influence of surgical treatment on the survival of patients with CMM of the head and neck. METHODS: Data originated from the CMM database of the Stockholm-Gotland area of Sweden. Tumor thickness or invasiveness (Breslow or Clark's levels), extent of surgical margin, sex, histogenetic type, anatomic site, and ulceration were compared statistically for 469 patients. RESULTS: Male patients with head and neck CMM had a 68% 10-year survival rate; the 10-year survival rate for female patients was 87%. The corresponding figures for CMM at other sites were 83% and 90%, respectively. Tumor thickness (or Clark level of invasion) was the only statistically significant prognostic factor in a multivariate analysis (P < .001). The surgical resection margin seemed to be of no importance to outcome. CONCLUSIONS: Long-term survival after treatment for CMM of the head and neck is better than reported in most earlier publications, presumably because our evaluation used population-based materials, an important factor in accurate reporting of this kind. Tumor thickness is the main prognostic factor in estimating outcome.

Female↗

PubMed2000

Synaptotagmin III isoform is compartmentalized in pancreatic beta-cells and has a functional role in exocytosis.

Synaptotagmin is involved in Ca2+-regulated secretion and has been suggested to serve as a general Ca2+ sensor on the membrane of secretory vesicles in neuronal cells. Insulin exocytosis from the pancreatic beta-cell is an example of a Ca2+-dependent secretory process. Previous studies of pancreatic beta-cells were unable to show presence of synaptotagmin I. We now present biochemical and immunohistochemical data showing that synaptotagmin III is present in pancreatic beta-cells as well as in the insulin-secreting cell line HIT-T15 and in rat insulinoma. By subcellular fractionation, we found synaptotagmin III in high-density fractions together with insulin and secretogranin I, indicating colocalization of synaptotagmin III and insulin in secretory granules. We could also show that blockade of synaptotagmin III by a specific antibody inhibited Ca2+-induced changes in beta-cell membrane capacitance, suggesting that synaptotagmin III is part of the functional protein complex regulating beta-cell exocytosis. The synaptotagmin III antibody did not affect the activity of the voltage-gated L-type Ca2+-channel. These findings are compatible with the view that synaptotagmin III, because of its distinct localization in the pancreatic beta-cell, functionally modulates insulin exocytosis. This indicates that synaptotagmin may have a general role in the regulation of exocytosis not only in neuronal cells but also in endocrine cells.

Animals↗

PubMed2000

Phosphatidylinositol 4,5-bisphosphate and ATP-sensitive potassium channel regulation: a word of caution.

Phosphatidylinositol 4,5-bisphosphate (PIP2) has been suggested to play an important role as an endogenous regulator of ATP-sensitive potassium (KATP) channels consisting of Kir6.2 as a pore-forming subunit. These studies show the ability of PIP2 to activate KATP channel activity and to counteract the inhibitory effect of ATP, implying that PIP2 could serve the function of modulating the sensitivity of KATP channels to the cytoplasmic free ATP concentration. Careful examination of the literature reveals that the definitive physiologically relevant experiments to establish efficacy of PIP2 on this channel may still have to be performed. Our reservations are based on the handling of PIP2 in cell-free experiments and in various strategies designed to modulate PIP2 concentrations in intact cells. Furthermore, a potent stimulatory effect of phosphatidylinositol 3,4,5trisphosphate, a downstream metabolite of PIP2, on KATP channel activity raises the possibility that the effects on the KATP channel may not be directly related to PIP2.

Adenosine Triphosphate↗

PubMed2000

Expression of insulin-like growth factor-1 receptor (IGF-1R) and p27Kip1 in melanocytic tumors: a potential regulatory role of IGF-1 pathway in distribution of p27Kip1 between different cyclins.

Insulin-like growth factor-1 receptor (IGF-1R) has been shown to be important for melanoma cell growth and survival. In this study we first show, using immunohistochemistry, that progression from benign nevi to malignant melanoma is paralleled by an increased expression of IGF-1R and a down-regulation of the cyclin-dependent kinase inhibitor p27Kip1. Even though the expression of p27Kip1 was drastically reduced compared to benign tumors, detectable amounts of it could be assayed by Western blotting in cultured melanoma cells. To analyze whether there is a causative relationship between the IGF-1 pathway and p27Kip1 expression, melanoma cells were treated with alpha IR-3, an antibody blocking the IGF-1 binding to IGF-1R, or Tunicamycin, which inhibits the translocation of IGF-1R to the cell surface. From these studies we could conclude that the overall expression of p27Kip1 is independent of the IGF-1 pathway. In contrast, the association of p27Kip1 with the different cyclins was drastically affected. Both TM and alpha IR-3 decreased the binding of p27Kip1 to cyclin D1, whose expression was drastically reduced. On the other hand there was an increased binding of p27Kip1 to cyclin E and cyclin A. This redistribution of p27Kip1 may be a mechanism for growth arrest and induction of apoptosis following interruption of the IGF-1 pathway in melanoma cells.

Blotting, Western↗

PubMed2000

Inhibition of N-linked glycosylation down-regulates insulin-like growth factor-1 receptor at the cell surface and kills Ewing's sarcoma cells: therapeutic implications.

The insulin-like growth factor-1 receptor (IGF-1R) has been shown to be of critical importance for tumor development and tumor cell survival of various types of malignancies. We have previously demonstrated that an adequate N-linked glycosylation of IGF-1R is required for its translocation to the cell surface in melanoma cells. This raises the possibility of using glycosylation inhibitors as therapeutic agents against IGF-1R-dependent malignancies. In this study we show that inhibition of N-linked glycosylation using tunicamycin or the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor lovastatin resulted in down-regulation of IGF-1R at the cell surface in Ewing's sarcoma cell lines (RD-ES and ES-1 cells). The down-regulation of plasma membrane-bound IGF-1R was correlated with a drastic decrease in IGF-1R autophosphorylation, suggesting biochemical inactivation of the receptor. Whereas RD-ES and ES-1 cells responded differently with regard to DNA synthesis, the decrease in IGF-1R expression was accompanied by a rapid and substantial decrease in survival of both cell lines. Our data suggest that relatively untoxic HMG-CoA reductase inhibitors (e.g. lovastatin) could have therapeutic significance in IGF-1R-dependent neoplasms like Ewing's sarcoma.

Antineoplastic Agents↗

PubMed1999

Spontaneous and stimulated transients in cytoplasmic free Ca(2+) in normal human osteoblast-like cells: aspects of their regulation.

We characterize two patterns of transients in cytoplasmic free calcium ([Ca2+]i) in normal human osteoblast-like cells (hOB cells). Firstly, spontaneous oscillations in [Ca2+]i were found to be common. The [Ca2+]i oscillations were completely inhibited by thapsigargin, indicating that Ca2+ fluxes between intracellular Ca2+ pools and the cytosol contributed to the generation of the [Ca2+]i oscillations. Removing extracellular Ca2+ either attenuated or completely inhibited spontaneous [Ca2+]i oscillations. Gadolinium, an inhibitor of stretch activated cation channels (SA-cat channels), reduced the frequency of [Ca2+]i oscillations. Hence, entry of calcium from the extracellular space, possibly through SA-cat channels also seemed to be of importance in the regulation of these [Ca2+]i oscillations. The role of the observed spontaneous [Ca2+]i oscillations in hOB cell function is not clear. Secondly, a decrease in pericellular osmolality, which causes the plasma membrane to stretch, transiently increased [Ca2+]i in hOB cells. This effect was also observed in a Ca2+ free extracellular environment, suggesting that osmotic stimuli release Ca2+ from intracellular pools. This finding indicates a possible signaling pathway by which mechanical strain can promote anabolic effects on the human skeleton.

Calcium↗

PubMed1999

Syntaxin 1 interacts with the L(D) subtype of voltage-gated Ca(2+) channels in pancreatic beta cells.

Interaction of syntaxin 1 with the alpha(1D) subunit of the voltage-gated L type Ca(2+) channel was investigated in the pancreatic beta cell. Coexpression of the enhanced green fluorescent protein-linked alpha(1D) subunit with the enhanced blue fluorescent protein-linked syntaxin 1 and Western blot analysis together with subcellular fractionation demonstrated that the alpha(1D) subunit and syntaxin 1 were colocalized in the plasma membrane. Furthermore, the alpha(1D) subunit was coimmunoprecipitated efficiently by a polyclonal antibody against syntaxin 1. Syntaxin 1 also played a central role in the modulation of L type Ca(2+) channel activity because there was a faster Ca(2+) current run-down in cells incubated with antisyntaxin 1 compared with controls. In parallel, antisyntaxin 1 markedly reduced insulin release in both intact and permeabilized cells, subsequent to depolarization with K(+) or exposure to high Ca(2+). Exchanging Ca(2+) for Ba(2+) abolished the effect of antisyntaxin 1 on both Ca(2+) channel activity and insulin exocytosis. Moreover, antisyntaxin 1 had no significant effects on Ca(2+)-independent insulin release trigged by hypertonic stimulation. This suggests that there is a structure-function relationship between the alpha(1D) subunit of the L type Ca(2+) channel and the exocytotic machinery in the pancreatic beta cell.

Animals↗

PubMed1999

Expression of insulin-like growth factor-1 receptor in synovial sarcoma: association with an aggressive phenotype.

It is well known that insulin-like growth factor-1 receptor (IGF-1R) plays a crucial role in proliferation and survival of transformed cells. Overexpression of IGF-1R in certain tumors has been reported, but there is still little known about its importance in vivo. Here, we evaluated the IGF-1R levels in 35 human synovial sarcoma tumors by Western blot and reverse transcriptase-PCR. In 18 of these, IGF-1R was detectable by Western blot, whereas 17 were nondetectable. There was a significant association between the amount of receptor proteins and mRNA transcripts. Furthermore, we found that the IGF-1R Western blot-positive tumors were associated with a high incidence of lung metastases. Eleven of 18 (61%) developed metastases in the IGF-1R detectable group, compared to 3 of 17 (18%) in the nondetectable group (P = 0.01). Moreover, in the detectable group of IGF-1R, 12 of 18 (67%) exhibited a high tumor cell proliferative rate, compared to 5 of 16 (31%) in the nondetectable group (P = 0.04). On the other hand, no association was found between the IGF-1R and type of fusion gene transcript (SYT-SSX1 or SYT-SSX2). Our results suggest that expression of IGF-1R can underlie an aggressive phenotype in synovial sarcoma.

Adult↗

PubMed1999

Identification of new HER2/neu-derived peptide epitopes that can elicit specific CTL against autologous and allogeneic carcinomas and melanomas.

Twenty-two new HLA-A2.1-binding peptides derived from the protooncogene HER2/neu were identified and analyzed for their capacity to elicit peptide and tumor-specific CTL responses. We used peptide-pulsed autologous DC from the ascites of patients with ovarian carcinomas to induce CTL. Of the 22 tested new HER2/neu-derived epitopes that could bind HLA-A2 with high (IC50 < 50 nM) or intermediate (50 nM < IC50 < 500 nM) affinity, we report the recognition by CTL of at least four novel epitopes, including HER2(9435), HER2(9665), HER2(9689), and HER2(10952), and confirm that of the known HER2 (9369) epitope. These epitopes were able to elicit CTL that specifically killed peptide-sensitized target cells and, most importantly, a HER2/neu-transfected cell line and the autologous tumor cells. We also confirm that HER2/neu is overexpressed in several melanoma lines, and as a new finding, report that some of these lines are sensitive to CTL induced by the HER2 (9369), HER2(9435), and HER2(9689) epitopes. Finally, CTL clones specific for HER2 (9369), HER2(9435), and HER2(9689) epitopes were isolated from tumor-specific CTL lines, further demonstrating the immunodominance of these epitopes. These findings broaden the potential application of HER2/neu-based immunotherapy.

Carcinoma↗

PubMed1999

The SYT-SSX1 variant of synovial sarcoma is associated with a high rate of tumor cell proliferation and poor clinical outcome.

Cytogenetically, synovial sarcoma (SS) is characterized by the translocation t(X;18)(p11.2;q11.2), resulting in a fusion between the SYT gene on chromosome 18 and SSX1 or SSX2 on the X chromosome and the formation of new chimeric genes, SYT-SSX1 or SYT-SSX2. We examined the potential clinical relevance of SYT-SSX1 and SYT-SSX2 fusion transcripts together with tumor proliferation. In a series of 33 patients with primary SS, the type of fusion transcript was assessed by reverse transcription-PCR and sequence analysis. The proliferation rate was analyzed using anti-Ki-67 antibodies. One case carrying an atypical transcript with a 57-bp insert was excluded, leaving 13 SYT-SSX1 and 19 SYT-SSX2 cases for analysis. The hazard ratio (with respect to metastasis-free survival for patients with SYT-SSX1 versus patients with SYT-SSX2 fusion transcripts was 7.4 (95% confidence interval, 1.5-36; log-rank P = 0.004). There was also an association with reduced overall survival for patients with SYT-SSX1 compared to patients with SYT-SSX2 (hazard ratio, 8.5; 95% confidence interval, 1.0-73; log-rank P = 0.02). The 5-year metastasis-free survival for patients with SYT-SSX1 was 42% versus 89% for patients with SYT-SSX2. There was a significant association between SYT-SSX1 and a high tumor proliferation rate (P = 0.02). We conclude that the findings suggest that the type of SYT-SSX fusion transcript determines the proliferation rate and is an important predictor of clinical outcome in patients with SS.

Adolescent↗

PubMed1999

Different modes of action of the imidazoline compound RX871024 in pancreatic beta-cells. Blocking of K+ channels, mobilization of Ca2+ from endoplasmic reticulum, and interaction with exocytotic machinery.

The imidazoline compound RX871024 glucose-dependently potentiates the release of insulin in pancreatic islets and beta-cell lines. This activity of the compound is not related to its action by stimulating alpha 2-adrenoceptors and I1- and I2-imidazoline receptors. There are at least three modes of action of RX871024 in beta-cells: (1) RX871024 blocks the ATP-dependent, Ca(2+)-activated, and delayed rectifier K+ channel activity; (2) RX871024 causes mobilization of Ca2+ from thapsigargin-sensitive intracellular stores, the effect probably controlled by cytochrome P450; and (3) the stimulatory activity of RX871024 on insulin release involves interaction of the compound with the exocytotic machinery, unrelated to the changes in membrane potential and cytoplasmic-free Ca2+ concentration, whereas protein phosphorylation plays an important role in this process. The maximal insulinotropic effect of RX871024 is much higher than that of the sulfonylurea glibenclamide. RX871024 stimulates insulin release and normalizes blood glucose levels in rats in vivo without affecting blood pressure and heart rate.

Animals↗