An intron 9 containing splice variant of PAX2.

BACKGROUND: PAX2 is a transcription factor with an important role in embryogenic development. However, PAX2 expression was frequently identified in neoplasia responsible for the growth and survival of cancer cells. Due to alternative splicing of exon 6, exon 10 and exon 12 four isoforms of PAX2 are described so far. METHODS: The expression of an intron 9 containing PAX2 splice variant was analyzed in neoplastic B cell and solid tumor cell lines as well as in primary tumor samples by quantitative RT-PCR. PAX2 proteins were detected by Western Blot in a subset of cell lines. RESULTS: All 14 lymphoma cell lines expressed an undescribed PAX2 splice variant containing the entire intron 9 sequence and the exon 10 sequence. This splice variant could also be detected in 35 solid tumor cell lines, in leukemia and lymphoma as well as in colon carcinoma and melanoma patient samples and in blood samples of healthy donors. Expression of this new splice variant on protein level was verified by Western Blot analysis. CONCLUSION: We discovered a previously undescribed intron 9 and exon 10 containing splice variant of PAX2 in B-cell neoplasia and in solid tumors on mRNA and protein level.

Wilms' tumor gene 1 (WT1) expression in subtypes of acute lymphoblastic leukemia (ALL) of adults and impact on clinical outcome.

Wilms' tumor gene 1 (WT1) is gaining increasing attention as a therapeutic target molecule due to its common expression in acute leukemias and its involvement in cell proliferation. Here, we reported on WT1 messenger RNA expression levels at diagnosis in a series of 238 adult acute lymphoblastic leukemia (ALL) samples of various subtypes and clinical outcome. WT1 expression was found in 219 out of 238 ALL samples (92%). Compared to a cohort of acute myeloid leukemia patients, the median WT1 expression level in ALL was significantly lower with large variations among different ALL subgroups. Specifically, WT1 expression levels were low in mature B-ALL and highest in ALL cases with co-expression of myeloid markers, making it a useful therapeutic target molecule in adult ALL with the exception of mature B-ALL. Cox regression analysis, considering ALL phenotype as well as molecular-cytogenetic subsets, revealed no independent prognostic role of WT1 expression level for disease-free and overall survival.

Follistatin antagonizes transforming growth factor-beta3-induced epithelial-mesenchymal transition in vitro: implications for murine palatal development supported by microarray analysis.

Epithelial-mesenchymal transition (EMT) is involved in normal embryonic development as well as in tumor progression and invasiveness. This process is also known to be a crucial step in palatogenesis during fusion of the bi-lateral palatal processes. Disruption of this step results in a cleft palate, which is among the most frequent birth defects in humans. A number of genes and encoded proteins have been shown to play a role in this developmental stage. The central role is attributed to the cytokine transforming growth factor-beta3 (TGF-beta3), which is expressed in the medial edge epithelium (MEE) already before the fusion process. The MEE covers the tips of the growing palatal shelves and eventually undergoes EMT or programmed cell death (apoptosis). TGF-beta3 is described to induce EMT in embryonic palates. With regard to the early expression of this molecule before the fusion process, it is not well understood which mechanisms prevent the TGF-beta3 producing epithelial cells from undergoing differentiation precociously. We used the murine palatal fusion to study the regulation of EMT. Specifically, we analyzed the MEE for the expression of known antagonists of TGF-beta molecules using in situ hybridization and detected the gene coding for Follistatin to be co-expressed with TGF-beta3. Further, we could show that Follistatin directly binds to TGF-beta3 and that it completely blocks TGF-beta3-induced EMT of the normal murine mammary gland (NMuMG) epithelial cell line in vitro. In addition, we analyzed the gene expression profile of NMuMG cells during TGF-beta3-induced EMT by microarray hybridization, detecting strong changes in the expression of apoptosis-regulating genes.

Expression of the stem cell markers nestin and CD133 on circulating melanoma cells.

Different molecular markers have been identified for melanoma-initiating cells including CD133 and nestin. Assuming that metastasis requires a dissemination of tumor-initiating cells, presence of circulating tumor-initiating cells should be associated with worse patient outcome. In this study, 20 ml blood was collected from 32 consecutive patients affected by metastatic melanoma and blood was enriched for circulating melanoma cells (CMCs) by CD45 depletion of the non-melanoma cell fraction. Multiparameter cytometry was carried out to co-stain with combinations of CD133 and nestin (NES). Six tissue samples from metastatic lesions of six different patients were stained with the same antibodies by immunohistochemistry. Percentage of NES-positive CMCs correlated with tumor burden and number of metastatic sites. Cox regression analysis revealed levels of lactate dehydrogenase (LDH; hazard ratio: 12.8 (1.35-121.5); P=0.02), number of metastatic sites (hazard ratio 3.87 (1.66-9.03); P=0.02), tumor burden (hazard ratio 5.72 (1.57-20.9); P=0.01), and percentage of NES-expressing CMCs ≥ 35% (hazard ratio 5.73 (1.66-19.7); P=0.006) to be factors related to shorter overall survival. CD133- and NES-expression profiles on CMCs were similar to matched metastatic tissue. These findings show that CMCs expressed stem cell-associated markers NES and CD133. Higher expression of NES on CMCs might represent an index of poor prognosis.

Circulating melanoma cells and distant metastasis-free survival in stage III melanoma patients with or without adjuvant interferon treatment (EORTC 18991 side study).

AIM: To evaluate the prognostic and predictive importance of detection of melanoma cells in peripheral blood using reverse transcriptase polymerase chain reaction (RT-PCR) in stage III cutaneous melanoma patients after sentinel or regional lymph node dissection. PATIENTS AND METHODS: Serial testing for tyrosinase and Mart-1/Melan-A transcripts in peripheral blood was performed every 6 months over a maximum period of 60 months in a subset of patients enrolled in EORTC 18991 phase 3 trial, comparing pegylated interferon-alpha-2b with observation. Univariate and multivariate analyses were performed to estimate the role of RT-PCR as prognostic and predictive factor for distant metastasis-free survival (DMFS). RESULTS: Among 299 patients who underwent RT-PCR analyses, 109 (36.5%) had at least one positive sample, either at time of randomisation (N=17) or subsequently (N=92). The cumulative rate of positive results was similar in the two treatment groups, as the DMFS from first RT-PCR positivity. RT-PCR result, positive versus negative, at a given time point, had no prognostic impact on subsequent DMFS. Cox time-dependent analysis indicated a significantly higher risk of developing distant metastasis in patients with a positive sample as compared to those with a negative one: hazard ratio (HR) of 2.23 (95% confidence interval (CI), 1.40-3.55; p<.001). These results were comparable in the 2 treatment groups, indicating that RT-PCR assessment was not predictive for treatment outcome. CONCLUSION: Detection of circulating tumour cells by RT-PCR for tyrosinase and Mart-1/Melan-A was a time-dependent moderate prognostic factor for subsequent development of distant metastasis in stage III melanoma patients.

Sensitivity of tumor cells to proteasome inhibitors is associated with expression levels and composition of proteasome subunits.

BACKGROUND: Sensitivity of tumor cells to induction of apoptosis by proteasome inhibitors varies greatly. This study was undertaken to investigate the sensitivity of neoplastic B cells and solid tumor cells to proteasome inhibition with respect to constitutive expression levels of proteasome subunits. METHODS: Twelve neoplastic B-cell lines and 12 solid tumor cell lines were assessed for their expression levels of proteasome subunits by using quantitative reverse transcriptase-polymerase chain reaction analysis and were assessed for their sensitivity to the proteasome inhibitors PS-341 and lactacystin by using a flow cytometry assay that detected activated caspases. RESULTS: The neoplastic B-cell lines were categorized into 3 groups representing refractory cell lines, cell lines with moderate sensitivity, and cell lines with high sensitivity. Correlating expression levels of proteasome subunits with sensitivity to proteasome inhibition indicated that refractory B cells exhibited lower expression levels of the standard subunit beta2 and of the immunoproteasome subunit LMP2 compared with sensitive B cell lines. Compared with neoplastic B cells solid tumor cells were less sensitive. They expressed the immunoproteasome subunits LMP2, LMP7 and MECL-1 and the standard subunit beta2 clearly below the median of the expression level of the sensitive B cell lines. IFN-gamma pretreatment enhanced sensitivity to PS-341 in 50% of the tumor cell lines, potentially related to the induction of immunoproteasomes. CONCLUSIONS: The results of this study indicated that sensitivity to proteasome inhibition is correlated with expression levels of proteasome subunits, which determine the enzymatic activity of the proteasome. Combining PS-341 with IFN-gamma may enhance its clinical efficacy.