Splicing of the platelet‐derived‐growth‐factor A‐chain mRNA in human malignant mesothelioma cell lines and regulation of its expression

Platelet‐derived‐growth‐factor (PDGF) A‐chain transcripts differing in the presence or absence of an alternative exon‐derived sequence have been described. In some publications, the presence of PDGF A‐chain transcripts with this exon‐6‐derived sequence was suggested to be tumour specific. However, in this paper it was shown by reverse‐transcription polymerase‐chain‐reaction (PCR) analysis that both normal mesothelial cells and malignant mesothelioma cell lines predominantly express the PDGF A‐chain transcript without the exon‐6‐derived sequence. This sequence encodes a cell‐retention signal, which means that the PDGF A‐chain protein is most likely to be secreted by both cell types. In cultured normal mesothelial cells, the secreted PDGF A‐chain protein might be involved in autocrine growth stimulation via PDGF α receptors. However, human malignant mesothelioma cell lines only possess PDGF β receptors. If this also holds true in vivo, the PDGF A‐chain protein produced and secreted by malignant mesothelial cells might have a paracrine function. In a previous paper, we described elevated expression of the PDGF A‐chain transcript in human malignant mesothelioma cell lines, compared to normal mesothelial cells. In this paper, the possible reason for this elevation was studied. First, alterations at the genomic level were considered, but cytogenetic and Southern‐blot analysis revealed neither consistent chromosomal aberrations, amplification nor structural rearrangement of the PDGF A‐chain gene in the malignant cells. Possible differences in transcription rate of the PDGF A‐chain gene, and stability of the transcript between normal and malignant cells, were therefore studied. The presence of a protein‐synthesis inhibitor, cycloheximide, in the culture medium did not significantly influence the PDGF A‐chain mRNA level in normal mesothelial and malignant mesothelioma cell lines. Furthermore, nuclear run‐off analysis showed that nuclear PDGF A‐chain mRNA levels varied in both cell types to the same extent as the levels observed in Northern blots. Taken together, this suggests that increased transcription is the most probable mechanism for the elevated mRNA level of the PDGF A‐chain gene in human malignant mesothelioma cell lines.</p

Splicing of the platelet‐derived‐growth‐factor A‐chain mRNA in human malignant mesothelioma cell lines and regulation of its expression

Platelet‐derived‐growth‐factor (PDGF) A‐chain transcripts differing in the presence or absence of an alternative exon‐derived sequence have been described. In some publications, the presence of PDGF A‐chain transcripts with this exon‐6‐derived sequence was suggested to be tumour specific. However, in this paper it was shown by reverse‐transcription polymerase‐chain‐reaction (PCR) analysis that both normal mesothelial cells and malignant mesothelioma cell lines predominantly express the PDGF A‐chain transcript without the exon‐6‐derived sequence. This sequence encodes a cell‐retention signal, which means that the PDGF A‐chain protein is most likely to be secreted by both cell types. In cultured normal mesothelial cells, the secreted PDGF A‐chain protein might be involved in autocrine growth stimulation via PDGF α receptors. However, human malignant mesothelioma cell lines only possess PDGF β receptors. If this also holds true in vivo, the PDGF A‐chain protein produced and secreted by malignant mesothelial cells might have a paracrine function. In a previous paper, we described elevated expression of the PDGF A‐chain transcript in human malignant mesothelioma cell lines, compared to normal mesothelial cells. In this paper, the possible reason for this elevation was studied. First, alterations at the genomic level were considered, but cytogenetic and Southern‐blot analysis revealed neither consistent chromosomal aberrations, amplification nor structural rearrangement of the PDGF A‐chain gene in the malignant cells. Possible differences in transcription rate of the PDGF A‐chain gene, and stability of the transcript between normal and malignant cells, were therefore studied. The presence of a protein‐synthesis inhibitor, cycloheximide, in the culture medium did not significantly influence the PDGF A‐chain mRNA level in normal mesothelial and malignant mesothelioma cell lines. Furthermore, nuclear run‐off analysis showed that nuclear PDGF A‐chain mRNA levels varied in both cell types to the same extent as the levels observed in Northern blots. Taken together, this suggests that increased transcription is the most probable mechanism for the elevated mRNA level of the PDGF A‐chain gene in human malignant mesothelioma cell lines.</p

Regulation of differential expression of platelet-derived growth factor α-and β-receptor mRNA in normal and malignant human mesothelial cell lines

In earlier studies we showed that the expression patterns of platelet-derived growth factor (PDGF) α- and β-receptors differ between normal and malignant mesothelial cell lines. Normal mesothelial cells predominantly express PDGF α-receptor mRNA and protein, whereas most malignant mesothelioma cell lines produce PDGF P-receptor mRNA and protein. In this paper we studied regulation of this differential PDGF receptor mRNA expression. Such an analysis is of importance in view of the suggested PDGF autocrine activity involving the PDGF β-receptor in mesothelioma cells. The results obtained in this study demonstrate that malignant mesothelioma cell lines are not only capable of PDGF β-receptor transcription but of α-receptor transcription as well, as evidenced from run off analysis and RT-PCR using α-receptor specific primers. However, the fact that PDGF α-receptor mRNA could not be detected by Northern blot analysis, even after cycloheximide treatment, suggests a difference in steady-state PDGF α-receptor mRNA expression levels between normal and malignant mesothelial cell lines, which is likely to be caused by a post-transcriptional mechanism. In normal mesothelial cells a half-life of more than 6 h was observed for PDGF α-receptor mRNA. In the majority of malignant mesothelioma cell lines clear PDGF β-receptor mRNA expression was seen. The half-life of the PDGF β-receptor transcript was at least 6 h in these cells. In contrast, hardly any PDGF β-receptor transcription was observed in run off assays in normal mesothelial cells, suggesting that differences in β-receptor transcriptional initiation most probably account for the inability to clearly detect PDGF β-receptor transcripts in these cells. Transforming growth factor β-1 (TGF-β1), which is being produced in active form by mesothelial cells was evaluated for its potential role in regulation of the differential PDGF receptor expression in these cells. Stimulation with TGF-β1 revealed decreased PDGF α-receptor mRNA expression in normal mesothelial cells. The effect on PDGF β-receptor mRNA in the malignant mesothelioma cell lines was variable. Although the TGF-β1 effect cannot entirely explain the differential PDGF receptor expression pattern, TGF-β1 may nevertheless play a role in downregulation of an (already) low PDGF α-receptor mRNA level in malignant mesothelioma cell lines.</p

Regulation of differential expression of platelet-derived growth factor α-and β-receptor mRNA in normal and malignant human mesothelial cell lines

In earlier studies we showed that the expression patterns of platelet-derived growth factor (PDGF) α- and β-receptors differ between normal and malignant mesothelial cell lines. Normal mesothelial cells predominantly express PDGF α-receptor mRNA and protein, whereas most malignant mesothelioma cell lines produce PDGF P-receptor mRNA and protein. In this paper we studied regulation of this differential PDGF receptor mRNA expression. Such an analysis is of importance in view of the suggested PDGF autocrine activity involving the PDGF β-receptor in mesothelioma cells. The results obtained in this study demonstrate that malignant mesothelioma cell lines are not only capable of PDGF β-receptor transcription but of α-receptor transcription as well, as evidenced from run off analysis and RT-PCR using α-receptor specific primers. However, the fact that PDGF α-receptor mRNA could not be detected by Northern blot analysis, even after cycloheximide treatment, suggests a difference in steady-state PDGF α-receptor mRNA expression levels between normal and malignant mesothelial cell lines, which is likely to be caused by a post-transcriptional mechanism. In normal mesothelial cells a half-life of more than 6 h was observed for PDGF α-receptor mRNA. In the majority of malignant mesothelioma cell lines clear PDGF β-receptor mRNA expression was seen. The half-life of the PDGF β-receptor transcript was at least 6 h in these cells. In contrast, hardly any PDGF β-receptor transcription was observed in run off assays in normal mesothelial cells, suggesting that differences in β-receptor transcriptional initiation most probably account for the inability to clearly detect PDGF β-receptor transcripts in these cells. Transforming growth factor β-1 (TGF-β1), which is being produced in active form by mesothelial cells was evaluated for its potential role in regulation of the differential PDGF receptor expression in these cells. Stimulation with TGF-β1 revealed decreased PDGF α-receptor mRNA expression in normal mesothelial cells. The effect on PDGF β-receptor mRNA in the malignant mesothelioma cell lines was variable. Although the TGF-β1 effect cannot entirely explain the differential PDGF receptor expression pattern, TGF-β1 may nevertheless play a role in downregulation of an (already) low PDGF α-receptor mRNA level in malignant mesothelioma cell lines.</p

Expression of the wilms' tumor gene WT1 in human malignant mesothelioma cell lines and relationship to platelet‐derived growth factor A and insulin‐like growth factor 2 expression

Mutations in the WT1 tumor suppressor gene are known to contribute to the development of Wilms' tumor (WT) and associated gonadal abnormalities. WT1 is expressed principally in the fetal kidney, developing gonads, and spleen and also in the mesothelium, which lines the coelomic cavities. These tissues develop from mesenchymal components that have subsequently become epithelialized, and it has therefore been proposed that WT1 may play a role in this transition of cell types. To test the possible involvement of this gene in malignant mesothelioma, we have first studied its expression in a panel of human normal and malignant mesothelial cell lines. WT1 mRNA expression levels varied greatly between the cell lines and no specific chromosomal aberration on 11p, which could be related to the variation in WT1 expression in these cell lines, was observed. Furthermore, no gross deletions, rearrangements, or functionally inactivating point mutations in the WT1 coding region were identified. All four WT1 splice variants were observed at similar levels in these cell lines. The WT1 gene encodes a zinc‐finger transcription factor and the four protein isoforms are each believed to act as transcriptional repressors of certain growth factor genes. Lack of WT1 expression is thus predicted to result in growth stimulation of tumor cells. Binding of one particular WT1 isoform construct to the insulin‐like growth factor 2 (IGF2) and platelet‐derived growth factor A (PDGFA) gene promoters has been demonstrated to result in repression of these genes in transient transfection studies. Analysis of IGF2 and PDGFA mRNA expression levels compared with WT1 mRNA expression levels failed to demonstrate an inverse correlation in the mesothelial cell lines, which endogenously express these genes. Finally, the putative role of WT1 in the transition of cell types was investigated. No obvious correlation between WT1 expression levels and cell morphology of the malignant mesothelial cell lines was evident from this study. Moreover, no change in WT1 expression was observed in normal mesothelial cells which were, by alteration of culture conditions, manipulated to switch from the mesenchymal to epithelial morphology.</p

Expression of the wilms' tumor gene WT1 in human malignant mesothelioma cell lines and relationship to platelet‐derived growth factor A and insulin‐like growth factor 2 expression

Mutations in the WT1 tumor suppressor gene are known to contribute to the development of Wilms' tumor (WT) and associated gonadal abnormalities. WT1 is expressed principally in the fetal kidney, developing gonads, and spleen and also in the mesothelium, which lines the coelomic cavities. These tissues develop from mesenchymal components that have subsequently become epithelialized, and it has therefore been proposed that WT1 may play a role in this transition of cell types. To test the possible involvement of this gene in malignant mesothelioma, we have first studied its expression in a panel of human normal and malignant mesothelial cell lines. WT1 mRNA expression levels varied greatly between the cell lines and no specific chromosomal aberration on 11p, which could be related to the variation in WT1 expression in these cell lines, was observed. Furthermore, no gross deletions, rearrangements, or functionally inactivating point mutations in the WT1 coding region were identified. All four WT1 splice variants were observed at similar levels in these cell lines. The WT1 gene encodes a zinc‐finger transcription factor and the four protein isoforms are each believed to act as transcriptional repressors of certain growth factor genes. Lack of WT1 expression is thus predicted to result in growth stimulation of tumor cells. Binding of one particular WT1 isoform construct to the insulin‐like growth factor 2 (IGF2) and platelet‐derived growth factor A (PDGFA) gene promoters has been demonstrated to result in repression of these genes in transient transfection studies. Analysis of IGF2 and PDGFA mRNA expression levels compared with WT1 mRNA expression levels failed to demonstrate an inverse correlation in the mesothelial cell lines, which endogenously express these genes. Finally, the putative role of WT1 in the transition of cell types was investigated. No obvious correlation between WT1 expression levels and cell morphology of the malignant mesothelial cell lines was evident from this study. Moreover, no change in WT1 expression was observed in normal mesothelial cells which were, by alteration of culture conditions, manipulated to switch from the mesenchymal to epithelial morphology.</p

The clinical applicability of sensor technology with body position detection to combat pressure ulcers in bedridden patients

Introduction: Pressure Ulcers (PUs) are a major healthcare issue leading to prolonged hospital stays and decreased quality of life. Monitoring body position changes using sensors could reduce workload, improve turn compliance and decrease PU incidence. Method: This systematic review assessed the clinical applicability of different sensor types capable of in-bed body position detection. Results: We included 39 articles. Inertial sensors were most commonly used (n = 14). This sensor type has high accuracy and is equipped with a 2–4 hour turn-interval warning system increasing turn compliance. The second-largest group were piezoresistive (pressure) sensors (n = 12), followed by load sensors (n = 4), piezoelectric sensors (n = 3), radio wave-based sensors (n = 3) and capacitive sensors (n = 3). All sensor types except inertial sensors showed a large variety in the type and number of detected body positions. However, clinically relevant position changes such as trunk rotation and head of bed elevation were not detected or tested. Conclusion: Inertial sensors are the benchmark sensor type regarding accuracy and clinical applicability but these sensors have direct patient contact and (re)applying the sensors requires the effort of a nurse. Other sensor types without these disadvantages should be further investigated and developed. We propose the Pressure Ulcer Position System (PUPS) guideline to facilitate this.</p

The clinical applicability of sensor technology with body position detection to combat pressure ulcers in bedridden patients

Introduction: Pressure Ulcers (PUs) are a major healthcare issue leading to prolonged hospital stays and decreased quality of life. Monitoring body position changes using sensors could reduce workload, improve turn compliance and decrease PU incidence. Method: This systematic review assessed the clinical applicability of different sensor types capable of in-bed body position detection. Results: We included 39 articles. Inertial sensors were most commonly used (n = 14). This sensor type has high accuracy and is equipped with a 2–4 hour turn-interval warning system increasing turn compliance. The second-largest group were piezoresistive (pressure) sensors (n = 12), followed by load sensors (n = 4), piezoelectric sensors (n = 3), radio wave-based sensors (n = 3) and capacitive sensors (n = 3). All sensor types except inertial sensors showed a large variety in the type and number of detected body positions. However, clinically relevant position changes such as trunk rotation and head of bed elevation were not detected or tested. Conclusion: Inertial sensors are the benchmark sensor type regarding accuracy and clinical applicability but these sensors have direct patient contact and (re)applying the sensors requires the effort of a nurse. Other sensor types without these disadvantages should be further investigated and developed. We propose the Pressure Ulcer Position System (PUPS) guideline to facilitate this.</p

Glucocorticoid receptor expression in human bronchial epithelial cells: effects of smoking and COPD.

Previously, we found that inflammatory mediators modulated the number and binding affinity of glucocorticoid receptors (GR) in human bronchial epithelial cell lines. In this study we investigated whether smoking and chronic obstructive pulmonary disease (COPD), both characterized by airway inflammation with increased levels of inflammatory mediators, affect GR characteristics in cultured human bronchial epithelial cells (HBEC). A statistically significant difference was found between the dissociation constant (Kd) values in HBEC from smoking (Kd = 0.98+/-0.08 nM; n = 6) and nonsmoking controls (Kd = 0.76+/-0.10 nM, P = 0.03; n = 5), but no significant difference was found between the mean number of binding sites. Our results are the first indication that cultured HBEC from smokers possess GR with a lower binding affinity. This may result from the inflammation found in the airways from smokers. Furthermore, these results provide further evidence that the bronchial epithelium may be an actual target for inhaled glucocorticoid therapy