Biomedical subjects

O Larsson

Publications and source records attributed to O Larsson.

At least 19 recordsLinked to original sources

PubMed2003

Gain of 17q in malignant fibrous histiocytoma is associated with a longer disease-free survival and a low risk of developing distant metastasis.

In this study, a panel of 39 primary malignant fibrous histiocytomas (MFH) of high malignancy grade were characterised for chromosomal alterations. The results were then evaluated in relation to the survival and the occurrence of recurrent disease during follow-up for an average period of 63 months. Chromosomal alterations detected by comparative genomic hybridisation (CGH) were recorded in 37 of the 39 cases analysed. The most frequent CGH abnormalities were gains of 17p, 20q, 16p, 17q, 1p31, 7q21, and 9cen-q22, and losses of 9p21-pter and 13q21-22. However, the patterns of CGH imbalances did not allow the identification of a single common event, suggesting that the key initiating event(s) is not a numerical imbalance. Patients with tumours harbouring a gain of 17q showed significantly longer overall and disease-free survival (P=0.001 and 0.008) as well as lower frequency of metastasis (P=0.018) during follow-up. Taken together, the findings suggest that the clinical outcome of MFH is associated with the genetic profiles of the primary tumours. Importantly, a subgroup of MFHs characterised by a low risk of developing metastasis and local recurrence is recognised based on their frequent gains of 17q by CGH.

Adult↗

PubMed2003

Polariton parametric amplifier pump dynamics in the coherent regime.

We studied the pump coherent dynamics in a II-VI microcavity parametric amplifier, using angle-resolved four-wave mixing. The polariton parametric amplification is found to result in a strong quenching and saturation of the pump coherence lifetime above the threshold. For the polariton scattering processes that remain below the amplification threshold, we find an angle-dependent collision broadening associated with the efficiency of the polariton scattering towards the excitonic reservoir.

Journal Article↗

PubMed2003

Characterization of lacZ complementation deletions using membrane receptor dimerization.

We describe the screening of lacZ deletions in mammalian cells and the discovery of a novel pair of lacZ deletions that can undergo alpha-complementation only when they are fused to peptides that interact with each other. The two lacZ deletions, delta N 11-75 and delta C 82-1023, were first characterized by fusing to two small interacting peptides and were then further analyzed by fusing to three membrane receptors (G protein-coupled receptors alpha 2cAR and D2DRL and receptor tyrosine kinase insulin receptor) that were known to form homodimers in the membrane. Histochemical and quantitative FACS assays demonstrated that the novel deletions have much lower level of association with each other, thus offering a much lower background in monitoring membrane protein interactions compared to previously published lacZ deletions. Furthermore, our method has the exciting potential to monitor simultaneously membrane receptor dimerization and localization to the cell surface of living cells.

Animals↗

PubMed2002

Tissue distribution and differential expression of melanocortin 1 receptor, a malignant melanoma marker.

The melanocortin 1 receptor is a G-protein-coupled receptor, described to be expressed on melanomas and melanocytes. Subsequent RT-PCR studies demonstrated the presence of melanocortin 1 receptor mRNA in other tissues such as pituitary gland and testis. Previously, we have demonstrated that three HLA-A2 binding nonamer peptides derived from melanocortin 1 receptor can elicit peptide-specific CTL which can recognize target cells transfected with the melanocortin 1 receptor gene and MHC class I matched melanoma lines. The potential of targeting melanocortin 1 receptor in therapy and diagnosis will depend on a preferential expression of this receptor in the majority of primary and metastatic melanomas vs normal tissues. We tested a panel of melanomas, carcinomas and other cell lines for the presence of melanocortin 1 receptor, using two monoclonal antibodies. The receptor was detected in 83% of the tested melanoma cell lines but not in other carcinoma lines. Immunohistochemistry revealed a strong expression of melanocortin 1 receptor in all tested primary and metastatic melanomas, but also demonstrated low levels of expression in adrenal medulla, cerebellum, liver and keratinocytes. Flow cytometry studies showed that melanocortin 1 receptor was expressed in in vitro activated monocytes/macrophages and in the THP-1 monocytic leukaemia line at levels of about 1 in 3 to 1 in 5 of that found in melanomas. Peripheral blood-derived dendritic cells, also express melanocortin 1 receptor in vitro. This extensive analysis of melanocortin 1 receptor tissue distribution may be of relevance not only for melanoma immunology, but also for research on the pathogenicity of inflammatory conditions in the skin and neurologic tissues. It remains to be seen if the over-expression of melanocortin 1 receptor in melanomas is sufficiently high to allow a 'therapeutic window' to be exploited in cancer immunotherapy.

Biomarkers, Tumor↗

PubMed2002

Assessment and management of risks arising from exposure to cadmium in fertilisers--II.

A preliminary, illustrative human health risk assessment of exposure to cadmium in phosphate fertilisers was performed using typical UK data and a protocol previously developed for application by individual Member States in the European Union. The risk assessment indicated that the for the most pessimistic population exposures characterised by both extreme (97th percentile) cereal and potato consumption and high susceptibility to cadmium uptake, the estimated dose was under the WHO Provisional Tolerable Weekly Intake (PTWI) for fertiliser cadmium concentrations ranging from 15 to 100 mg Cd/kg P2O5 applied over 100 years. However, the low margin of safety for high risk groups and the uncertainties inherent in the overall risk assessment suggested that a prudent risk management strategy would involve maintenance of low levels of cadmium in fertilisers and/or conditions that permitted low accumulation of cadmium in soils. On this basis, two main risk reduction measures were developed and assessed: (a) imposition of limits on cadmium concentration in fertilisers; and (b) imposition of charges on levels of cadmium in phosphate fertilisers. An assessment of the economic impact of these risk reduction measures indicated that, at all price elasticities, the most significant impact in terms of changes in demand and changes in consumer expenditure on phosphate fertilisers will be seen with cadmium charges where no thresholds are defined. The impact on the consumer (i.e. farmer) will be an increase in spending of approximately US $4000 per year, which is considered significant, accompanied by a decrease in demand above 20%. If a threshold is set at 60 mg Cd/kg P2O5, the impact is significantly reduced, but stays relatively high compared to the other options. The analysis also indicates that the use of low-cadmium rock is the low cost option. At a likely rock price increase of approximately 5% and assuming a likely price elasticity of -0.2, the yearly costs to farmers will be approximately US $82 which is considered a minimal impact. In the worst case scenario (elasticity of -0.6 and a 10% increase in rock prices), the increase in spending by farmers will be of 3.9% or US $221 which is also considered to represent a minimal impact. At similar price elasticities, the use of decadmation technologies is predicted to be more costly than the use of low-cadmium rock but this option can still be considered as having a minimal impact on the consumer (increase in expenditure of 1.9-13.3% or US $106-748).

Agriculture↗

PubMed2001

Characterization of hydrophobic prenyl groups of isoprenylated proteins in human cancer cells.

Extensive protease digestion of delipidated [3H]mevalonate (MVA)-labeled proteins, followed by HPLC separation of the products, is one approach to identify and study prenyl cysteines. Using this methodology three major [3H]MVA-labeled peaks appeared. Two of them represent farnesyl cysteine (FC) and geranylgeranyl cysteine (GGC). The third peak represents unknown products that are considerably more hydrophobic than FC and GGC, here designated HPC. Previously, we provided evidence that cysteine residues may also be modified by dolichyl groups. Dolichyl cysteines (DolC) belong to HPC. However, as shown in the present study, DolC only represents a minor portion of HPC. Data obtained from different sets of experiments, including [3H]GGOH-labeling and use of prenyl transferase inhibitors, suggest that HPC mainly involves CXC or CC residues with double-linked GG groups. In turn this points to the possibility that proteins modified by double GG groups are quite common, and may probably involve other proteins than the rab family of GTPases.

Chromatography, High Pressure Liquid↗

PubMed2001

Glucose-induced oscillations in cytoplasmic free Ca2+ concentration precede oscillations in mitochondrial membrane potential in the pancreatic beta-cell.

Using dual excitation and fixed emission fluorescence microscopy, we were able to measure changes in cytoplasmic free Ca(2+) concentration ([Ca(2+)](i)) and mitochondrial membrane potential simultaneously in the pancreatic beta-cell. The beta-cells were exposed to a combination of the Ca(2+) indicator fura-2/AM and the indicator of mitochondrial membrane potential, rhodamine 123 (Rh123). Using simultaneous measurements of mitochondrial membrane potential and [Ca(2+)](i) during glucose stimulation, it was possible to measure the time lag between the onset of mitochondrial hyperpolarization and changes in [Ca(2+)](i). Glucose-induced oscillations in [Ca(2+)](i) were followed by transient depolarizations of mitochondrial membrane potential. These results are compatible with a model in which nadirs in [Ca(2+)](i) oscillations are generated by a transient, Ca(2+)-induced inhibition of mitochondrial metabolism resulting in a temporary fall in the cytoplasmic ATP/ADP ratio, opening of plasma membrane K(ATP) channels, repolarization of the plasma membrane, and thus transient closure of voltage-gated L-type Ca(2+) channels.

Adenosine Triphosphate↗

PubMed2001

Application of an immunodiagnostic method for improving preoperative diagnosis of nodular thyroid lesions.

BACKGROUND: Thyroid cancer is the most common endocrine malignant disease, but preoperative diagnosis remains a challenge. Fine-needle aspiration cytology has greatly improved the clinical management of thyroid nodules, but the preoperative characterisation of follicular lesions is very difficult. Many patients are thus referred to surgery more for diagnosis than for therapeutic necessity. We undertook an international multicentre study to assess the usefulness of immunohistocytochemical staining for two potential markers of malignant thyrocytes. METHODS: Expression of galectin-3 and CD44v6 was tested on 1009 thyroid lesions (tissue specimens and cytological cell-blocks) and 226 fresh cytological samples obtained preoperatively by ultrasound-guided fine-needle aspiration of thyroid nodules (prospective analysis). The test used monoclonal antibodies specific for CD44v6 and galectin-3, the indirect avidin-biotin complex immunoperoxidase method, and 3-amino-9-ethyl-carbazole as substrate. FINDINGS: The sensitivity, specificity, positive predictive value, and diagnostic accuracy of this test method (for coexpression of the two markers) in the prospective analysis were 88%, 98%, 91%, and 97%, respectively. The sensitivity and specificity of galectin-3 immunodetection alone in discriminating benign from malignant thyroid lesions were more than 99% and 98% respectively, and the positive predictive value and diagnostic accuracy were 92% and 99%. INTERPRETATION: The integration of galectin-3 immunostaining with conventional cytomorphological and clinical diagnostic procedures represents a sensitive and reliable diagnostic approach for preoperative identification of thyroid carcinomas. This test method improves the diagnostic accuracy of conventional cytology and provides the molecular basis for a new nosological assignation of the not yet classified thyroid neoplasms of indeterminate malignant behaviour.

Antigens, Differentiation↗

PubMed2001

Cloning and characterization of spliced fusion transcript variants of synovial sarcoma: SYT/SSX4, SYT/SSX4v, and SYT/SSX2v. Possible regulatory role of the fusion gene product in wild type SYT expression.

The synovial sarcoma translocation t(X;18)(p11.2; q11.2) results in the fusion of the SYT gene on chromosome 18 to exon 5 of either SSX1 or SSX2 genes on chromosome X. We recently reported that the SSX4 gene is also involved in such a translocation. In the present investigation we cloned and sequenced the full-length cDNA of SYT/SSX1, SYT/SSX2 and SYT/SSX4 from synovial sarcoma tissues. We isolated a novel fusion transcript type variant involving the fusion of SYT with exon 6 of the SSX4 gene (SYT/SSX4v). The SYT/SSX4 and SYT/SSX2 open reading frame also differed from previously reported SYT/SSX sequences by an in-frame addition of 93bp exon located in the junction between exon 7 and 8 of the SYT. This exon is identical to that reported for the murine SYT but has not been previously found in the human transcript. Two SYT transcripts, with and without the 93 bp exon, were co-expressed in mouse NIH3T3 cells, human malignant cells and human testis tissue, but not in human normal fibroblasts. Stable transfection of an SYT/SSX4 expression vector into human and murine cell lines correlated with a down-regulation of SYT transcripts. This was also observed in a synovial sarcoma tumor expressing SYT/SSX4. This suggests that the SYT/SSX fusion gene may regulate SYT expression from the normal allele and as such alter the normal function of SYT.

Amino Acid Sequence↗

PubMed2001

Ca2+-induced Ca2+ release from the endoplasmic reticulum amplifies the Ca2+ signal mediated by activation of voltage-gated L-type Ca2+ channels in pancreatic beta-cells.

Stimulus-secretion coupling in pancreatic beta-cells involves membrane depolarization and Ca(2+) entry through voltage-gated L-type Ca(2+) channels, which is one determinant of increases in the cytoplasmic free Ca(2+) concentration ([Ca(2+)](i)). We investigated how the endoplasmic reticulum (ER)-associated Ca(2+) apparatus further modifies this Ca(2+) signal. When fura-2-loaded mouse beta-cells were depolarized by KCl in the presence of 3 mm glucose, [Ca(2+)](i) increased to a peak in two phases. The second phase of the [Ca(2+)](i) increase was abolished when ER Ca(2+) stores were depleted by thapsigargin. The steady-state [Ca(2+)](i) measured at 300 s of depolarization was higher in control cells compared with cells in which the ER Ca(2+) pools were depleted. The amount of Ca(2+) presented to the cytoplasm during depolarization as estimated from the integral of the increment in [Ca(2+)](i) over time (integralDelta[Ca(2+)](i).dt) was approximately 30% higher compared with that in the Ca(2+) pool-depleted cells. neo-thapsigargin, an inactive analog, did not affect [Ca(2+)](i) response. Using Sr(2+) in the extracellular medium and exploiting the differences in the fluorescence properties of Ca(2+)- and Sr(2+)-bound fluo-3, we found that the incoming Sr(2+) triggered Ca(2+) release from the ER. Depolarization-induced [Ca(2+)](i) response was not altered by, an inhibitor of phosphatidylinositol-specific phospholipase C, suggesting that stimulation of the enzyme by Ca(2+) is not essential for amplification of Ca(2+) signaling. [Ca(2+)](i) response was enhanced when cells were depolarized in the presence of 3 mm glucose, forskolin, and caffeine, suggesting involvement of ryanodine receptors in the amplification process. Pretreatment with ryanodine (100 microm) diminished the second phase of the depolarization-induced increase in [Ca(2+)](i). We conclude that Ca(2+) entry through L-type voltage-gated Ca(2+) channels triggers Ca(2+) release from the ER and that such a process amplifies depolarization-induced Ca(2+) signaling in beta-cells.

Animals↗

PubMed2001

Clinical impact of molecular and cytogenetic findings in synovial sarcoma.

Synovial sarcoma is an aggressive soft-tissue tumor that accounts for up to 10% of soft-tissue sarcomas. Cytogenetically, synovial sarcoma is characterized by the t(X;18)(p11;q11), found in more than 95% of the tumors. This translocation results in rearrangements of the SYT gene in 18q11 and one of the SSX1, SSX2, or SSX4 genes in Xp11, creating a SYT/SSX1, SYT/SSX2, or SYT/SSX4 chimeric gene. It has been shown that patients with SYT/SSX1 fusion genes have a shorter metastasis-free survival than do patients with SYT/SSX2. Previous studies have also suggested that clonal evolution may be associated with disease progression. In the present study, RT-PCR analysis showed that all 64 examined synovial sarcomas from 54 patients had SYT-SSX chimeric genes. SYT/SSX1 was found in 40 tumors from 33 patients, SYT/SSX2 in 23 tumors from 20 patients, and SYT/SSX4 in one case. Two patients had variant SYT/SSX2 transcripts, with 57 bp and 141 bp inserts, respectively, between the known SYT and SSX2 sequences. Patients with tumors with SYT/SSX1 fusions had a higher risk of developing metastases compared to those with SYT/SSX2 fusions (P = 0.01). The reciprocal transcripts SSX1/SYT and SSX2/SYT were detected using nested PCR in 11 of the 40 samples with SYT/SSX1 and 5 of the 23 samples with SYT/SSX2, respectively. Among 20 blood samples, SYT/SSX1 and SYT/SSX2 were detected in one sample each. The t(X;18), or variants thereof, was found cytogenetically in all patients but three. Among 32 primary tumors, the t(X;18) or a variant translocation was the sole anomaly in 10. In contrast, of the seven metastatic lesions that were investigated prior to radiotherapy, only one had a t(X;18) as the sole anomaly; all other tumors displayed complex karyotypes. Cytogenetic complexity in primary tumors was, however, not associated with the development of metastases. Tumors with SYT/SSX2 less often (4/12 vs. 7/15) showed complex karyotypes than did tumors with SYT/SSX1, but the difference was not significant. Combining cytogenetic complexity and transcript data, we found that the subgroup of patients with tumors showing simple karyotypes and SYT/SSX2 fusion had the best clinical outcome (2/8 patients developed metastases), and those with tumors showing complex karyotypes together with SYT/SSX1 fusion the worst (6/7 patients developed metastases). This corresponded to 5-year metastasis-free survival rates of 0.58 and 0.0, respectively (P = 0.02).

Adolescent↗

PubMed2001

Bactericidal antisense effects of peptide-PNA conjugates.

Antisense peptide nucleic acids (PNAs) can specifically inhibit Escherichia coli gene expression and growth and hold promise as anti-infective agents and as tools for microbial functional genomics. Here we demonstrate that chemical modification improves the potency of standard PNAs. We show that 9- to 12-mer PNAs, especially when attached to the cell wall/membrane-active peptide KFFKFFKFFK, provide improvements in antisense potency in E. coli amounting to two orders of magnitude while retaining target specificity. Peptide-PNA conjugates targeted to ribosomal RNA (rRNA) and to messenger RNA (mRNA) encoding the essential fatty acid biosynthesis protein Acp prevented cell growth. The anti-acpP PNA at 2 microM concentration cured HeLa cell cultures noninvasively infected with E. coli K12 without any apparent toxicity to the human cells. These results indicate that peptides can be used to carry antisense PNA agents into bacteria. Such peptide-PNA conjugates open exciting possibilities for anti-infective drug development and provide new tools for microbial genetics.

Amino Acid Sequence↗

PubMed2001

Inositol hexakisphosphate increases L-type Ca2+ channel activity by stimulation of adenylyl cyclase.

Inositol hexakisphosphate (InsP6) is a most abundant inositol polyphosphate that changes simultaneously with inositol 1,4,5-trisphosphate in depolarized neurons. However, the role of InsP6 in neuronal signaling is unknown. Mass assay reveals that the basal levels of InsP6 in several brain regions tested are similar. InsP6 mass is significantly elevated in activated brain neurons and lowered by inhibition of neuronal activity. Furthermore, the hippocampus is most sensitive to electrical challenge with regard to percentage accumulation of InsP6. In hippocampal neurons, InsP6 stimulates adenylyl cyclase (AC) without influencing cAMP phosphodiesterases, resulting in activation of protein kinase A (PKA) and thereby selective enhancement of voltage-gated L-type Ca2+ channel activity. This enhancement was abolished by preincubation with PKA and AC inhibitors. These data suggest that InsP6 increases L-type Ca2+ channel activity by facilitating phosphorylation of PKA phosphorylation sites. Thus, in hippocampal neurons, InsP6 serves as an important signal in modulation of voltage-gated L-type Ca2+ channel activity.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2001

The novel imidazoline compound BL11282 potentiates glucose-induced insulin secretion in pancreatic beta-cells in the absence of modulation of K(ATP) channel activity.

The insulinotropic activity of the novel imidazoline compound BL11282 was investigated. Intravenous administration of BL11282 (0.3 mg x kg(-1) x min(-1)) to anesthetized rats did not change blood glucose and insulin levels under basal conditions, but produced a higher increase in blood insulin levels and a faster glucose removal from the blood after glucose infusion. Similarly, in isolated Wistar rat pancreatic islets, 0.1-100 micromol/l BL11282 potently stimulated glucose-induced insulin secretion but did not modulate basal insulin secretion. Unlike previously described imidazolines, BL11282 did not block ATP-dependent K+ channels. Furthermore, the compound stimulated insulin secretion in islets depolarized with high concentrations of KCl or permeabilized with electric shock. Insulinotropic activity of BL11282 was dependent on activity of protein kinases A and C. In pancreatic islets from spontaneously diabetic GK rats, the imidazoline compound restored the impaired insulin response to glucose. In conclusion, the imidazoline BL11282 constitutes a new class of insulinotropic compounds that exerts an exclusive glucose-dependent insulinotropic activity in pancreatic islets by stimulating insulin exocytosis.

Adenosine Triphosphate↗

PubMed2001

Concomitant loss of chromosome 3 and whole arm losses and gains of chromosome 1, 6, or 8 in metastasizing primary uveal melanoma.

PURPOSE: To elucidate the genetic differences between metastasizing and nonmetastasizing primary tumors, uveal melanoma samples were screened for DNA copy number alterations by comparative genomic hybridization (CGH). METHODS: DNA copy number changes were studied on 14 primary uveal melanomas that had not metastasized, 15 primary uveal melanomas that had metastasized, and on 6 metastases that were available from 6 primary uveal melanomas. CGH is based on quantitation of the fluorescence intensity of differentially labeled DNAs. Tumor DNA labeled with FITC dCTP and dUTP and normal DNA labeled with Texas red dCTP and dUTP were hybridized to normal metaphase chromosomes. The hybridizations were analyzed using an Olympus fluorescence microscope and the ISIS digital image analysis system to identify gain or loss of genetic material. RESULTS: Primary uveal melanomas that had metastasized and metastases had significantly more changes than primary uveal melanomas that had not metastasized. Comparison between primary nonmetastasizing tumors, metastasizing tumors, and metastases showed that the most common DNA copy number changes were -3 (21%, 73%, 67%, respectively), -6q (7%, 40%, 83%), -1p (0, 33%, 33%), -13q (14%, 13%, 50%), -8p (14%, 27%, 0), -18 (7%, 13%, 33%), +8q (14%, 53%, 100%), +6p (29%, 20%, 17%), +1q (0, 7%, 33%), and +16p (0, 7%, 33%). CONCLUSIONS: Loss of chromosome 3, loss of 6q, and gain of 8q were significantly associated with poor overall survival. In addition, losses of 1p were only found in primary uveal melanomas that had metastasized and in metastases, which suggests that this region may harbor a tumor suppressor gene important in the tumor progression. Finally, loss of chromosome 3 may be associated with isochromosome formation of 1q, 6p, 8q, 16p, 20q, and 22q.

Adult↗

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↗