Biomedical subjects

Jorma Isola

Publications and source records attributed to Jorma Isola.

At least 19 recordsLinked to original sources

PubMed2007

Cytogenetic characterization and gene expression profiling of the trastuzumab-resistant breast cancer cell line JIMT-1.

Resistance to the HER-2 targeting drug trastuzumab can be observed clinically, but the lack of suitable experimental models hampers studies of resistance mechanisms. We characterized a HER-2-positive carcinoma cell line (JIMT-1) derived from a 62-year-old breast cancer patient which was clinically resistant to trastuzumab. Multicolor fluorescence in situ hybridization revealed a complex hyperdiploid karyotype with numerous marker chromosomes and unbalanced translocations. Comparative genomic hybridization (CGH) revealed numerous regions of copy number aberration (CNA). Further analysis by array CGH identified 27 regions of CNA (16 amplified, 11 deleted). Thirty-eight percent of the genes in the amplified regions were overexpressed, compared to only 9% in regions of normal copy number ratios (CNR). Accordingly, 26% of the genes in the deleted regions were underexpressed, compared to 10% in regions of normal CNR. Most amplified and overexpressed genes were located on chromosome 1 as well as on 8q, 12q14.1, 17q11 approximately q21, and 20q13. In 17q11 approximately q21, we identified two separate amplicons, the HER-2 amplicon and a previously unreported amplicon at 17q21.31. Several aberrant genes are implicated in cancer development (e.g., JUN, CDK4, and SLUG protooncogenes, as well as the drug/hormone-metabolizing genes GSTM1 and CYP24). We conclude that cytogenetic and expression profiling of JIMT-1 revealed several new features that need further characterization and may shed light on trastuzumab resistance.

Animals↗

PubMed2006

Generalisability of survival estimates for patients with breast cancer--a comparison across two population-based series.

The purpose of the study was to analyse the generalisability and geographic transportability of survival estimates produced by commonly used prognostic factors. We compared the influence of tumour size, histologic grade, axillary nodal status, oestrogen and progesterone receptor contents, age at diagnosis and two prognostication schemes (the Nottingham Prognostic Index and St. Gallen criteria) in two nationwide cohorts of patients diagnosed with breast cancer in 1991-2, the FinProg (n=2923, Finland) and the SEER series (n=43,249, the United States (US)). Eight-year estimates of breast cancer-specific (84% versus 80%), relative (86% versus 83%), and overall (70% versus 69%) survival were slightly more favourable in the SEER than in the FinProg series, respectively. Despite differences in demographic variables and the frequency of use of adjuvant therapies and mammography screening between the series, the prognostic factors examined produced close to overlapping survival curves with similar shapes. The results suggest that quantitative survival estimates based on frequently used prognostic factors and prognostication schemes are generalisable and transportable between large, unselected cohorts of breast cancer patients.

Adult↗

PubMed2006

Basoluminal carcinoma: a new biologically and prognostically distinct entity between basal and luminal breast cancer.

PURPOSE: Breast carcinomas expressing basal epithelium cytokeratins constitute a tumor subgroup that is typically hormone receptor negative and shows a distinct gene expression profile. Based on variable basal cytokeratin immunostaining patterns, we hypothesized that the "basal phenotype" tumor group may comprise more than one biological entity. EXPERIMENTAL DESIGN: Basal cytokeratins 5 and 14 (CK5/14) were stained by immunohistochemistry and the percentage of positive cells was defined by image analysis. The results thus obtained were compared with clinicopathologic characteristics and relapse-free survival. RESULTS: Of the 506 breast tumors, 53 (10.5%) showed immunoreactivity for CK5/14. Basal cytokeratin expression showed up as two microscopically distinguishable subtypes, i.e., a uniformly positive type ("basal") and a partially positive type ("basoluminal") often displaying a checkerboard-type intratumoral heterogeneity. These subgroups could also be separated with a third basal cytokeratin (CK17, P < 0.0001). Both basal and basoluminal subtypes were hormone receptor negative and of high grade, but differed with respect to the Ki-67 labeling index (P = 0.0014), vimentin (P = 0.005), and c-kit (P = 0.02), which were more frequently expressed in basal than in basoluminal tumors. In contrast, the amplification of HER-2 was found almost exclusively in the basoluminal subgroup (P = 0.009). Compared with the basal tumors, basoluminal tumors associated with significantly shorter relapse-free survival (P = 0.01), which was not explained by their more frequent HER-2 amplification. CONCLUSIONS: We conclude that the intratumoral heterogeneity in basal cytokeratin expression can be used to define two distinct breast cancer subtypes, basal and basoluminal, with distinctive features related to proliferation activity, oncogene and biomarker status, and patient survival.

Aged↗

PubMed2006

Female predominance in meningiomas can not be explained by differences in progesterone, estrogen, or androgen receptor expression.

The female predominance in meningioma incidence and association between meningioma and breast cancer suggest that growth of meningiomas is hormone-dependent. There are several discrepancies in literature about the proliferative effect of sex hormones on meningiomas. This study aims to evaluate the hormone receptor status of meningiomas and assess its relation to age, sex, histological grade, recurrence, and proliferation activity. The material was based on consecutive patients operated for meningioma at Tampere University Hospital in 1989-1999. The occurrence of progesterone, estrogen and androgen receptor in patients with primary and recurrent meningiomas was studied immunohistochemically by using specific monoclonal antibodies. Hormonal status was determined in 510 tumor samples. 443 samples were from primary meningiomas and 67 from recurrent tumors. Of the samples, 455 were benign (WHO grade I), 49 atypical (grade II), and 6 malignant (grade III). Of the primary tumor samples, 88% were progesterone receptor positive, 40% were positive for estrogen and 39% for androgen receptors. Grade I meningiomas had significantly higher incidence for estrogen and androgen receptors than higher grade meningiomas. Estrogen positive tumor samples had significantly higher proliferation index than estrogen negative samples. No difference in expression of sex hormone receptors was observed by sexes or age group. Estrogen and androgen receptors may have more influence on the pathogenesis of meningiomas than earlier thought. The higher incidence of meningiomas in women can not be explained by differences of sex hormone receptor expression.

Age Factors↗

PubMed2006

Topoisomerase IIalpha gene amplification predicts favorable treatment response to tailored and dose-escalated anthracycline-based adjuvant chemotherapy in HER-2/neu-amplified breast cancer: Scandinavian Breast Group Trial 9401.

PURPOSE: Amplification of the HER-2/neu and topoisomerase IIalpha (TOP2A) genes has been linked to the effects of anthracyclines. Their role in predicting the outcome of anthracycline-based adjuvant chemotherapy for breast cancer patients has remained controversial. PATIENTS AND METHODS: The present substudy of the Scandinavian Breast Group trial 9401, in which an epirubicin-based regimen (nine courses of tailored and dose-escalated fluorouracil, epirubicin, and cyclophosphamide [FEC]) was compared with three or four courses of standard FEC followed by bone marrow-supported high-dose chemotherapy (cyclophosphamide, thiotepa, and carboplatin), included high-risk breast cancer patients (with eight or more positive axillary lymph nodes or at least five nodes with additional poor prognostic indicators). Amplification of HER-2/neu was determined retrospectively in paraffin-embedded tumor tissue sections by chromogenic in situ hybridization. TOP2A was tested only in HER-2/neu-amplified tumors. RESULTS: HER-2/neu amplification alone, which was present in 32.7% of the tumors, was a strong prognostic factor for short relapse-free (P = .0034) and overall survival (P = .0008) but showed no direct association with treatment assignment. TOP2A coamplification, which was present in 37% of HER-2/neu-amplified tumors, was associated with better relapse-free survival in patients treated with tailored and dose-escalated FEC (hazard ratio [HR] = 0.45; P = .049). A statistical multivariate Cox's regression analysis confirmed the predictive significance of TOP2A coamplification (HR = 0.30; P = .020) in HER-2/neu-amplified tumors. There was no such association in patients with HER-2/neu-amplified tumors without TOP2A gene amplification. CONCLUSION: Coamplification of HER-2/neu and TOP2A may define a subgroup of high-risk breast cancer patients who benefit from individually tailored and dose-escalated adjuvant anthracyclines.

Anthracyclines↗

PubMed2006

Gene amplification, mutation, and protein expression of EGFR and mutations of ERBB2 in serous ovarian carcinoma.

EGFR and erbB-2 are targets for specific cancer therapy. The purpose of this study was to examine the frequency and clinicopathological correlations of gene amplification, protein expression, and mutations of EGFR and ERBB2 in serous carcinoma, the most common and aggressive type of ovarian cancer. Tissue microarray constructed of 398 carcinomas was examined by chromogenic in situ hybridization (CISH) and by immunohistochemistry. Cases with amplification of EGFR by CISH were further analyzed by fluorescence in situ hybridization. One hundred ninety-eight samples were analyzed for mutations in exons 18, 19, or 21 of EGFR and in exon 20 of ERBB2 using denaturating high-performance liquid chromatography and direct sequencing. Amplification of EGFR was present in 12% (41/333), low-level gain in 43% (144/333), and protein overexpression in 17% (66/379) of the tumors. Both increased copy number and overexpression of EGFR were associated with high tumor grade, greater patient age, large residual tumor size, high proliferation index, aberrant p53, and poor patient outcome. Furthermore, increased copy number of EGFR was associated with increased copy number of ERBB2. No mutations were identified in EGFR, whereas one tumor had an insertion mutation in exon 20 of ERBB2. Both amplification and protein overexpression of EGFR occur in serous ovarian carcinoma, but EGFR copy number has a stronger prognostic value. This makes EGFR amplification a potentially useful criterion for selecting patients in clinical trials testing the effect of EGFR inhibitors in serous ovarian carcinoma.

Cystadenocarcinoma, Serous↗

PubMed2006

Adjuvant docetaxel or vinorelbine with or without trastuzumab for breast cancer.

BACKGROUND: We compared docetaxel with vinorelbine for the adjuvant treatment of early breast cancer. Women with tumors that overexpressed HER2/neu were also assigned to receive concomitant treatment with trastuzumab or no such treatment. METHODS: We randomly assigned 1010 women with axillary-node-positive or high-risk node-negative cancer to receive three cycles of docetaxel or vinorelbine, followed by (in both groups) three cycles of fluorouracil, epirubicin, and cyclophosphamide. The 232 women whose tumors had an amplified HER2/neu gene were further assigned to receive or not to receive nine weekly trastuzumab infusions. The primary end point was recurrence-free survival. RESULTS: Recurrence-free survival at three years was better with docetaxel than with vinorelbine (91 percent vs. 86 percent; hazard ratio for recurrence or death, 0.58; 95 percent confidence interval, 0.40 to 0.85; P=0.005), but overall survival did not differ between the groups (P=0.15). Within the subgroup of patients who had HER2/neu-positive cancer, those who received trastuzumab had better three-year recurrence-free survival than those who did not receive the antibody (89 percent vs. 78 percent; hazard ratio for recurrence or death, 0.42; 95 percent confidence interval, 0.21 to 0.83; P=0.01). Docetaxel was associated with more adverse effects than was vinorelbine. Trastuzumab was not associated with decreased left ventricular ejection fraction or cardiac failure. CONCLUSIONS: Adjuvant treatment with docetaxel, as compared with vinorelbine, improves recurrence-free survival in women with early breast cancer. A short course of trastuzumab administered concomitantly with docetaxel or vinorelbine is effective in women with breast cancer who have an amplified HER2/neu gene. (International Standard Randomised Controlled Trial number, ISRCTN76560285.).

Analysis of Variance↗

PubMed2006

Allelic imbalance of HER2 variant in sporadic breast and ovarian cancer.

Both breast and ovarian cancers are associated with HER2 receptor activation, which usually results from receptor overexpression and/or gene amplification. The HER-2 gene harbors a polymorphism at codon 655 (GTC/valine to ATC/isoleucine) in the transmembrane domain region, which has been associated with an elevated risk of breast cancer. The objective of this study was to determine whether the polymorphism is under a selection pressure during breast and ovarian carcinogenesis. The Ile/Val genotype was present in 41% (9/22) of the normal DNA of breast cancer patients. An allelic imbalance in the tumor tissue was found in three breast tumors, with overrepresentation of the Val allele. HER-2 was amplified and overexpressed in these tumors. Half of the eight ovarian tumor patients carried heterozygous Ile/Val genotypes. In contrast to breast tumors, all these ovarian cancer specimens showed the presence of the Ile allele. In our selected set of tumors, the Val allele was overrepresented in the subset of HER2-positive breast cancers and the Ile allele in serous ovarian cancer. Further analyses of tumors with known gene amplifications and overexpression may reveal novel associations between germline polymorphisms and development of sporadic tumors.

Adult↗

PubMed2006

Virtual microscopy in prostate histopathology: simultaneous viewing of biopsies stained sequentially with hematoxylin and eosin, and alpha-methylacyl-coenzyme A racemase/p63 immunohistochemistry.

PURPOSE: Histopathological diagnosis of small focus carcinomas in prostatic needle biopsies is often assisted by IHC. To make a definitive diagnosis the pathologist must compare IHC findings with hematoxylin and eosin stained tissue morphology. We introduce what is to our knowledge a new application of virtual microscopy, in which hematoxylin and eosin, and IHC stains done sequentially on the same microscope slide can be simultaneously displayed and compared on a computer screen. MATERIALS AND METHODS: A total of 30 hematoxylin and eosin stained prostatic needle biopsies were scanned with a computer controlled microscope. The slides were destained and then immunostained with a cocktail of AMACR and p63 antibodies, which labels the nuclei of nonmalignant basal cells (p63) and the cytoplasm of neoplastic glandular cells suspicious for malignancy (AMACR). The slides were then scanned again and the pairs of virtual slides were aligned for synchronized viewing. RESULTS: The presented technique was found helpful when suspicious lesions were small and when examining the immunoprofile of specimens was warranted, in addition to examining hematoxylin and eosin stained tissue morphology. The usefulness of our approach based on virtual microscopy can be evaluated on the website , which also serves as an educational tool for self-learning the correlation between hematoxylin and eosin stained tissue morphology, and AMACR/p63 IHC in prostate biopsies. CONCLUSIONS: The technology for simultaneously viewing sequentially hematoxylin and eosin and IHC stained prostate biopsies can be readily used for educational purposes, as exemplified by our website, and along with the availability of rapid virtual slide scanners it can also be used for clinical diagnostics.

Biopsy, Needle↗

PubMed2006

Platelet-derived growth factor receptor family mutations in gastrointestinal stromal tumours.

OBJECTIVE: Activating mutations of either KIT or platelet-derived growth factor receptor alpha (PDGFRA) genes are present in the majority of gastrointestinal stromal tumours (GISTs). The type of gene mutation is associated with the aggressiveness of the disease, response to imatinib therapy, and the tumour site in the gastrointestinal tract. However, a subgroup of GISTs does not harbour these mutations. MATERIAL AND METHODS: Thirty-three GISTs were studied for mutations in exons encoding the juxtamembrane and the activation loop domains of KIT, PDGFRA, PDGFRB, CSF1R, and FLT3 genes using denaturing high-performance liquid chromatography and gene sequencing. RESULTS: Twenty-two (67%) GISTs had mutation in KIT and 3 (9%) in PDGFRA. The three PDGFRA mutations were all detected in exon 18 of the gene. Three of the 5 GISTs that had weak to moderate KIT expression had a PDGFRA mutation as compared to none of the 26 cases with strong KIT immunopositivity (p=0.022). No mutations were found in PDGFRB, CSF1R or FLT3 in the 8 cases that did not harbour KIT or PDGFRA mutations. CONCLUSIONS: KIT and PDGFRA are the most commonly mutated type III receptor tyrosine kinase genes in GIST. GISTs with PDGFRA mutations often have reduced expression of the KIT protein in immunohistochemistry, suggesting that immunohistochemistry may be potentially useful in identification of such GISTs.

Adult↗

PubMed2006

Amplification of KIT, PDGFRA, VEGFR2, and EGFR in gliomas.

Receptor tyrosine kinase aberrations are implicated in the genesis of gliomas. We investigated expression and amplification of KIT, PDGFRA, VEGFR2, and EGFR in 87 gliomas consisting of astrocytomas, anaplastic astrocytomas, oligodendrogliomas, or oligoastrocytomas in tumor samples collected at the time of the diagnosis and in samples of the same tumors at tumor recurrence. Gene amplifications were investigated using either chromogenic in situ hybridization or fluorescence in situ hybridization, and protein expression using immunohistochemistry. In samples collected at glioma diagnosis, KIT and PDGFRA amplifications were more frequent in anaplastic astrocytomas than in astrocytomas, oligodendrogliomas, and oligoastrocytomas [28% versus 5% (P = 0.012) and 33% versus 2% (P = 0.0008), respectively]. VEGFR2 amplifications occurred in 6% to 17% of the gliomas at diagnosis, and EGFR amplifications in 0% to 12%. Amplified KIT was more frequently present in recurrent gliomas than in newly diagnosed gliomas (P = 0.0066). KIT amplification was associated with KIT protein expression and with presence of PDGFRA and EGFR amplifications both at the time of the first glioma diagnosis and at tumor recurrence, and with VEGFR2 amplification at tumor recurrence. Three (4%) primary gliomas and 10 (14%) recurrent gliomas that were evaluable for coamplification of KIT, PDGFRA, and VEGFR2 showed amplification of at least two of these genes; the amplicon contained amplified KIT in all 13 cases. In conclusion, besides glioblastoma, amplified KIT, PDGFRA, and VEGFR may also occur in lower-grade gliomas and in their recurrent tumors. It is currently not known whether specific tyrosine kinase inhibitors are effective in the treatment of such gliomas.

Brain Neoplasms↗

PubMed2005

Hsp90 inhibitor 17-AAG reduces ErbB2 levels and inhibits proliferation of the trastuzumab resistant breast tumor cell line JIMT-1.

ErbB2, a member of the EGF receptor family of tyrosine kinases is overexpressed on many tumor cells of epithelial origin and is the molecular target of trastuzumab (Herceptin), the first humanized antibody used in the therapy of solid tumors. Trastuzumab, which is thought to act, at least in part, by downregulating ErbB2 expression is only effective in approximately 30-40% of ErbB2 positive breast tumors. Geldanamycin and its derivative 17-AAG are potential antitumor agents capable of downregulating client proteins of Hsp90, including ErbB2. To investigate the ability of 17-AAG to downregulate ErbB2 in trastuzumab resistant breast cancer cells and the possibility of 17-AAG and trastuzumab potentiating each other's effect, the recently established trastuzumab resistant breast cancer cell line, JIMT-1 was compared to the known trastuzumab sensitive SKBR-3 line. Baseline and stimulus-evoked dimerization and activation levels of ErbB2, and the effects of trastuzumab and 17-AAG alone and in combination on cell proliferation and apoptosis, as well as on ErbB2 expression and phosphorylation have been measured. Baseline activation and amenability to activation and downregulation by trastuzumab was much lower in the resistant line. However, 17-AAG enhanced ErbB2 homodimerization after 5-10 min of treatment in both cell lines, and decreased proliferation with an IC50 of 70 nM for SKBR-3 and 10nM for JIMT-1. Thus, 17-AAG may be a useful drug in trastuzumab resistant ErbB2 overexpressing tumors. The antiproliferative effect of 17-AAG was positively correlated with phosphorylation and downregulation of ErbB2 and was dominated by apoptosis, although, especially at higher doses, necrosis was also present. Interestingly, IC50 values for ErbB2 downregulation and phosphorylation, in the 30-40 nM range, were not significantly different for the two cell lines. This observation and the negative correlation between resting ErbB2 levels and the antiproliferative effect of 17-AAG may indicate that activation of ErbB2 to some extent could counteract the overall cytostatic effect, especially at higher levels of ErbB2 expression. The usual therapeutic dose of trastuzumab did not change the IC50 of 17-AAG on the proliferation of either cell line, but nevertheless decreased overall ErbB2 phosphorylation and at low doses of 17-AAG further decreased cell growth in the sensitive SKBR-3, thus trastuzumab may be a good combination partner to counteract undesired activating effects of 17-AAG.

Antibodies, Monoclonal↗

PubMed2005

Proteolytic cleavage and phosphorylation of a tumor-associated ErbB4 isoform promote ligand-independent survival and cancer cell growth.

The ErbB1 and ErbB2 receptors are oncogenes with therapeutic significance in human cancer, whereas the transforming potential of the related ErbB4 receptor has remained controversial. Here, we have addressed whether four alternatively spliced ErbB4 isoforms differ in regulating cellular responses relevant for tumor growth. We show that the two tumor necrosis factor-alpha converting enzyme (TACE)-cleavable ErbB4 isoforms (the juxtamembrane [JM]-a isoforms) were overexpressed in a subset of primary human breast cancers together with TACE. The overexpression of the JM-a cytoplasmic (CYT)-2 ErbB4 isoform promoted ErbB4 phosphorylation, survival of interleukin-3-dependent cells, and proliferation of breast cancer cells even in the absence of ligand stimulation, whereas activation of the other three ErbB4 isoforms required ligand stimulation. Ligand-independent cellular responses to ErbB4 JM-a CYT-2 overexpression were regulated by both tyrosine kinase activity and a two-step proteolytic generation of an intracellular receptor fragment involving first a TACE-like proteinase, followed by gamma-secretase activity. These data suggest a novel transforming mechanism for the ErbB4 receptor in human breast cancer that is 1) specific for a single receptor isoform and 2) depends on proteinase cleavage and kinase activity but not ligand activation of the receptor.

ADAM Proteins↗

PubMed2005

Associations of ErbB2, beta1-integrin and lipid rafts on Herceptin (Trastuzumab) resistant and sensitive tumor cell lines.

ErbB2-mediated transmembrane signaling is a key target of novel anticancer agents such as Herceptin. Our comparison of Herceptin resistant (JIMT-1, MKN-7) and sensitive (SKBR-3, N-87) cell lines demonstrates the importance of ErbB2 association patterns involving integrins and lipid rafts. Flow cytometric FRET and confocal microscopic measurements revealed colocalization and molecular proximity between beta1-integrins and ErbB2, as well as their association with lipid rafts. A weak functional interaction between ErbB2 and beta1-integrin and the fact that ErbB2 did not co-patch with beta1-integrins upon crosslinking imply that ErbB2 and beta1-integrin define two distinct molecular association clusters from a functional point of view. Although Herceptin-sensitive cell lines expressed more ErbB2 and fewer beta1-integrin molecules on their surface than their resistant counterparts, this finding probably does not explain the Herceptin resistant phenotype due to the weak interaction between beta1-integrins and ErbB2. Our results imply that the true significance of the expression profile of proteins involved in oncogenesis can only be understood after characterizing their molecular interactions.

Antibodies, Monoclonal↗

PubMed2005

Down-regulated xanthine oxidoreductase is a feature of aggressive breast cancer.

PURPOSE: Xanthine oxidoreductase (XOR) is a key enzyme in the degradation of DNA, RNA, and high-energy phosphates and also plays a role in milk lipid globule secretion. Given the strong and regulated expression of XOR in normal breast epithelium, and the previously shown alterations of its expression in experimental tumorigenesis, we hypothesized that XOR may be differentially expressed in breast cancer. EXPERIMENTAL DESIGN: XOR expression was analyzed by immunohistochemistry in tissue microarray specimens of 1,262 breast cancer patients with a median follow-up of 9.5 years. RESULTS: Expression of XOR was moderately decreased in 50% and undetectable in another 7% of the tumors. Decreased XOR expression was associated with poor histologic grade of differentiation, ductal and lobular histologic types, large tumor size, high number of positive axillary lymph nodes, and high cyclooxygenase-2 expression, but not with estrogen or progesterone receptor status, Ki-67, p53, or ERBB2 amplification. Absence of XOR expression was associated with unfavorable outcome, and patients with no XOR expression had more than twice the risk of distant recurrence as compared with those with a moderately decreased or normal expression (hazard ratio, 2.21; P < 0.0001). This was also true in patients with node-negative disease (hazard ratio, 2.75; P < 0.0001) as well as in patients with small (< or = 1 cm) tumors (hazard ratio, 3.09; P = 0.027). In a multivariate survival analysis, negative XOR emerged as an independent prognostic factor both in the entire series (P = 0.01) and among patients with node-negative disease (P = 0.0009). CONCLUSION: Loss of XOR identifies breast cancer patients with unfavorable prognosis.

Breast↗

PubMed2005

Cleavable ErbB4 isoform in estrogen receptor-regulated growth of breast cancer cells.

ErbB1 and ErbB2 receptors are well-characterized targets for anticancer drugs, but the clinical relevance of the related ErbB4 receptor is unknown. Here, we have assessed the clinical significance of the proteolytically cleavable ErbB4 isoforms in breast cancer patients and investigated their functions in vitro. The expression of transcripts encoding the cleavable ErbB4 isoforms associated with estrogen receptor-alpha (ER) expression (P < 0.001) and a high histologic grade of differentiation (P </= 0.002) in real-time reverse transcription-PCR analysis of 62 breast cancer samples. Despite high ErbB4 mRNA expression levels in a subset of samples, ErbB4 gene amplification was not observed. High ErbB4 protein expression levels, as assessed by immunohistochemistry, associated with a favorable outcome in ER-positive cases from a series of 458 breast cancer patients (P = 0.01), whereas no association between ErbB4 expression and survival was found among women with ER-negative cancer (P = 0.86). However, nuclear ErbB4 immunoreactivity was associated with poor survival as compared with women whose cancer had membranous ErbB4 staining (P = 0.04). In vitro, overexpression of a cleavable ErbB4 isoform in ER-positive breast cancer cells resulted in translocation of a proteolytically released intracellular ErbB4 receptor fragment into the nucleus, as well as, enhanced proliferation, anchorage-independent growth, and estrogen response element-mediated transcriptional activity. These results suggest that the association of ErbB4 expression with clinical outcome is dependent on the subcellular localization of ErbB4 and that a proteinase-cleavable ErbB4 isoform promotes growth of ER-positive breast cancer and enhances ER-mediated gene transcription.

Alternative Splicing↗

PubMed2005

Decreased accessibility and lack of activation of ErbB2 in JIMT-1, a herceptin-resistant, MUC4-expressing breast cancer cell line.

Overexpression of erbB2 in breast tumors is associated with poor prognosis and is a target of receptor-oriented cancer therapy. Trastuzumab (Herceptin), a monoclonal antibody against a membrane-proximal epitope in the extracellular region of erbB2, shows a therapeutic effect against a fraction of erbB2-amplified breast tumors. Unfortunately, resistance to Herceptin is common, and its cause is as yet unclear. Here we investigated the properties of erbB2 in a Herceptin-resistant cell line, JIMT-1, established from a breast cancer patient showing erbB2 gene amplification and primary resistance to Herceptin. The expression profile of erbB proteins, Herceptin-induced erbB2 internalization, and down-regulation in JIMT-1 were similar to those in Herceptin-sensitive lines. However, the mean number of Herceptin Mab binding sites in JIMT-1 was 1/5 that of the expressed erbB2 molecules, although 5% to 10% of the cells showed a approximately 10-fold higher Herceptin binding than the main population. Herceptin Fab and Mab 2C4, an antibody binding to an epitope in the ectodomain further removed from the membrane, bound more efficiently to JIMT-1 cells than Herceptin Mab, implying that erbB2 was partly masked. The expression of MUC4, a membrane-associated mucin that according to reports contributes to the masking of membrane proteins, was higher in JIMT-1 than in Herceptin-sensitive lines, and its level was inversely correlated with the Herceptin binding capacity of single cells. Knockdown of MUC4 expression by RNA interference increased the binding of Herceptin. Western blotting showed a low level of proteolytic processing, shedding, and tyrosine phosphorylation of erbB2 in JIMT-1. The latter finding may explain its Herceptin-resistant phenotype characterizing both the low and high Herceptin binding subpopulations. We conclude that masking of erbB2 in JIMT-1 leads to diminished Herceptin binding and isolation of erbB2 from its normal interaction and activation partners.

Antibodies, Monoclonal↗

PubMed2005

Web-based virtual microscopy in teaching and standardizing Gleason grading.

Gleason grading forms the basis of prognostic and therapeutic assessment in prostatic carcinoma despite its subjective nature and substantial interobserver variation. The accuracy of Gleason grading can be improved by the use of educational tools such as reference images. However, conventional microscopy images are of limited educational value because it is neither possible to view the sample at different magnifications nor to navigate into different areas of the specimen. This limitation can be overcome by the use of virtual microscopy, which allows viewing entire digitized microscope slides. We created an interactive Web site ( www.webmicroscope.net/gleason ) featuring a comprehensive set of prostatic needle biopsies as virtual slides, which can be viewed with a standard Web browser (Internet Explorer or Netscape). To evaluate the validity of Web-based virtual microscopy for Gleason grading, an experienced uropathologist (TK) scored a series of 62 biopsies from the original glass slides and 6 weeks later from virtual slides on the Web site using an ordinary desktop computer. The intraobserver agreement was excellent, with identical Gleason scores found in 48 of the 62 cases ( kappa = 0.73). The 14 remaining scores differed only by 1 point on the Gleason scale (2-10). The virtual slides were viewed by 2 other uropathologists (PM and HH), with interobserver kappa coefficients ranging from 0.55 to 0.62, which is within the range of previously reported studies using glass slides. The 3 uropathologists' Gleason scores were included as reference scores on the Web site, which now serves as a publicly open platform for self-testing and learning of Gleason grading. We conclude that Web-based virtual microscopy is a promising new tool for teaching and standardizing Gleason grading.

Biopsy, Needle↗