Re-evaluation of histological diagnoses of malignant mesothelioma by immunohistochemistry

<p>Abstract</p> <p>Background</p> <p>In order to provide reliable tissue material for malignant mesothelioma (MM) studies, we re-evaluated biopsies and autopsy material from 61 patients with a diagnosis of MM from the period of 1980-2002.</p> <p>Methods</p> <p>Basic positive (Calretinin, EMA, Podoplanin, Mesothelin) and negative (CEA, Ber-Ep4) immunohistochemical (IHC) marker reactions were determined. If needed, more markers were used. Histological diagnoses were made by three pathologists. Survival data were calculated.</p> <p>Results</p> <p>49 cases (80%) were considered being MM by a high degree of likelihood, five more cases possible MM. Of the remaining seven cases, three were diagnosed as adenocarcinoma, three as pleomorphic lung carcinoma, in one peritoneal case a clear entity diagnosis could not be given. One of the possible MM cases and two of the lung carcinoma cases had this already as primary diagnoses, but were registered as MM.</p> <p>With a sensitivity of 100%, Calretinin and CEA were the most reliable single markers. The amount of MM cells with positive immunoreactivity (IR) for Podoplanin and Mesothelin showed most reliable inverse relation to the degree of atypia.</p> <p>In the confirmed MM cases, there had been applied either no IHC or between one and 18 markers.</p> <p>The cases not confirmed by us had either lacked IHC (n = 1), non-specific markers were used (n = 4), IR was different (n = 1), or specific markers had not shown positive IR in the right part of the tumour cells (n = 3).</p> <p>46 of the 49 confirmed and three of the not confirmed cases had been diagnosed by us as most likely MM before IHC was carried out.</p> <p>Conclusions</p> <p>In order to use archival tissue material with an earlier MM diagnosis for studies, histopathological re-evaluation is important. In possible sarcomatous MM cases without any positive IR for positive MM markers, radiology and clinical picture are essential parts of diagnostics. IHC based on a panel of two positive and two negative MM markers has to be adapted to the differential diagnostic needs in each single case. New diagnostic tools and techniques are desirable for cases where IHC and other established methods cannot provide a clear entity diagnosis, and in order to improve MM treatment.</p

Genome-Wide Profile of Pleural Mesothelioma versus Parietal and Visceral Pleura: The Emerging Gene Portrait of the Mesothelioma Phenotype

Malignant pleural mesothelioma is considered an almost incurable tumour with increasing incidence worldwide. It usually develops in the parietal pleura, from mesothelial lining or submesothelial cells, subsequently invading the visceral pleura. Chromosomal and genomic aberrations of mesothelioma are diverse and heterogenous. Genome-wide profiling of mesothelioma versus parietal and visceral normal pleural tissue could thus reveal novel genes and pathways explaining its aggressive phenotype.Well-characterised tissue from five mesothelioma patients and normal parietal and visceral pleural samples from six non-cancer patients were profiled by Affymetrix oligoarray of 38 500 genes. The lists of differentially expressed genes tested for overrepresentation in KEGG PATHWAYS (Kyoto Encyclopedia of Genes and Genomes) and GO (gene ontology) terms revealed large differences of expression between visceral and parietal pleura, and both tissues differed from mesothelioma. Cell growth and intrinsic resistance in tumour versus parietal pleura was reflected in highly overexpressed cell cycle, mitosis, replication, DNA repair and anti-apoptosis genes. Several genes of the “salvage pathway” that recycle nucleobases were overexpressed, among them TYMS, encoding thymidylate synthase, the main target of the antifolate drug pemetrexed that is active in mesothelioma. Circadian rhythm genes were expressed in favour of tumour growth. The local invasive, non-metastatic phenotype of mesothelioma, could partly be due to overexpression of the known metastasis suppressors NME1 and NME2. Down-regulation of several tumour suppressor genes could contribute to mesothelioma progression. Genes involved in cell communication were down-regulated, indicating that mesothelioma may shield itself from the immune system. Similarly, in non-cancer parietal versus visceral pleura signal transduction, soluble transporter and adhesion genes were down-regulated. This could represent a genetical platform of the parietal pleura propensity to develop mesothelioma.Genome-wide microarray approach using complex human tissue samples revealed novel expression patterns, reflecting some important features of mesothelioma biology that should be further explored

Molecular Resistance Fingerprint of Pemetrexed and Platinum in a Long-Term Survivor of Mesothelioma

Pemetrexed, a multi-folate inhibitor combined with a platinum compound is the first-line treatment of malignant mesothelioma, but median survival is still one year. Intrinsic and acquired resistance to pemetrexed is common, but its biological basis is obscure. Here we report for the first time a genome-wide profile of acquired resistance in the tumour from an exceptional case with advanced pleural mesothelioma and almost six years survival after 39 cycles of second-line pemetrexed/carboplatin treatment. Genome-wide analysis with Illumina BeadChip Kit of 25,000 genes was performed on mRNA from pre-treatment and post-resistance biopsies from this individual as well on case and control samples from our previously published study (in total 17 samples). Cell specific expression of proteins encoded by selected genes were analysed by immunohistochemistry. Serial serum levels of CA125, CYFRA21-1 and SMRP levels were examined. TS protein, the main target of pemetrexed was overexpressed. Proteins and genes related to DNA damage response, elongation and telomere extension and repair related directly and indirectly to platinum resistance were overexpressed, as the CHK1 protein and the genes CHEK2, LIG3, POLD1, POLA2, FANCD2, PRPF19, RECQ5 respectively, the last two not previously described in mesothelioma. We observed a down-regulation of leukocyte transendothelial migration and cell adhesion molecules pathways. Silencing of NT5C in two mesothelioma cell lines did not sensitize the cells to Pemetrexed. Proposed resistance markers are TS, KRT7/ CK7, TYMP/ thymidine phosphorylase and down-regulated SPARCL1 and CDKN1B. Moreover, comparison of the primary expression of the sensitive versus a primary resistant case showed multi-fold overexpressed DNA repair, cell cycle, cytokinesis, and spindle formation in the latter. Serum CA125 and SMRP reflected the clinical and radiological course and tumour burden. Genome-wide microarray of mesothelioma pre- and post-resistance biopsies indicated a novel resistance signature to pemetrexed/carboplatin that deserve validation in a larger cohort

Cell types fraction of nucleated cells in parietal pleura (PP) and tumour (T).

<p>One of the two samples of case no. 10 is removed as non-representative histologically (see text). ND = not done.</p

Pyrimidine metabolism in tumour versus normal and at acquired resistance.

<p>Genes involved in pathways of DNA metabolism and production in tumour versus normal (red corresponds to overexpressed and dark green correspond to down-regulated) and in acquired resistant tumour (in ovals, all were overexpressed). Abbreviations: 2.1.3.2 =  aspartate transcarbamylase 3.5.2.3 =  dihydroorotase 6.3.5.5 =  CAD; carbamoyl-phosphate synthetase 2 3.1.3.5 =  NT5C; 5′-nucleotidase 2.7.7.7 =  POLA2; DNA polymerase alpha subunit B 2.7.7.7 =  POLD1; DNA polymerase delta subunit 1 1.17.4.1 =  RRM2B; ribonucleoside-diphosphate reductase subunit M2 2.4.2.4 =  TYMP; thymidine phosphorylase.</p

Genes changed more than 2-fold after resistance.

<p>Expression of genes that changed more then 2-fold in the post-resistance tumour, compared to initial tumour. Down-regulated genes are shown to the left (30 in total, two not shown) and the overexpressed to the right (15, three not shown). Green bars represent the relative gene expression before and red bars after acquired resistance.</p

Venn diagram of significantly up- and down-regulated genes (n) in mesothelioma (T) versus normal parietal pleura (pp) and normal visceral pleura (pv) (<i>P</i><0.05).

<p>828 genes are overexpressed (red) and 1004 genes are down-regulated (green) in T versus pp. 341 genes are overexpressed (blue) and 52 genes downregulated (brown) in pv versus pp.</p

A selection of down-regulated gene ontology (GO) entities and genes (Down Genes) in normal parietal pleura versus visceral pleural tissue.

<p>Genes on Chip = the number of genes from each entity represented on the gene chip.</p

RNA isolation and histopathology.

<p>RNA was isolated from parietal pleura (PP) visceral pleura (PV) and mesothelioma (T).</p>*<p>Controls were operated for spontaneous pneumothorax. Histology of the bullae that induced the pneumothorax showed that none had clinical or radiological emphysema.</p