Alex R Musler

Academisch Medisch Centrum Universiteit van Amsterdam, Amsterdam, North Holland, Netherlands

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Publications (24)148.83 Total impact

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    ABSTRACT: Ocular adnexal marginal zone B-cell lymphomas (OAMZLs) arise in the connective tissues of the orbit or in the mucosa-associated lymphoid tissue of the conjunctiva. Here, we present the immunological and genetic analyses of 20 primary Chlamydia psittaci (Cp)-negative OAMZLs. Analysis of the immunoglobulin variable heavy chain (IgV(H)) gene usage demonstrated a significant preference for V(H)4-34. A combined analysis across all previously published OAMZLs confirmed that this is a general feature of OAMZL, in particular of the Cp-negative group. Our series of OAMZLs did not express the characteristic rheumatoid factor V(H)DJ(H) rearrangements that were previously found in salivary gland- and gastric-marginal zone B-cell lymphomas (MZBCLs). We did not detect the MZBCL-specific chromosomal translocations, t(11;18) API2-MALT1 (mucosa-associated lymphoid tissue1) and t(14;18) IgH/MALT1. Two cases contained a premature stop codon in the A20 gene (TNFAIP3) and one case harbored the activating MYD88 hotspot mutation L265P. Variable nuclear expression of BCL10, NFκB1 (p50) and NFκB2 (p52) suggests that other additional genetic abnormalities affecting the NFκB pathway exist within this group of lymphomas. OAMZL showed variable expression of the chemokine receptor CXCR3 and integrin α4β7 by the tumor B cells, and low interferon-γ and interlukin-4 mRNA levels in the tissue, indicative of an inflammatory environment with features in between those previously found in cutaneous and other extranodal MZBCL. The strongly biased usage of V(H)4-34 in Cp-negative OAMZLs suggests involvement of a particular stimulatory (auto-) antigen in their development.
    Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 02/2012; 26(7):1647-53. · 10.16 Impact Factor
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    ABSTRACT: Hyperplastic polyposis syndrome (HPS) is characterized by the presence of multiple colorectal serrated polyps and is associated with an increased colorectal cancer (CRC) risk. The mixture of distinct precursor lesion types and malignancies in HPS provides a unique model to study the canonical pathway and a proposed serrated CRC pathway in humans. To establish which CRC pathways play a role in HPS and to obtain new support for the serrated CRC pathway, we assessed the molecular characteristics of polyps (n = 84) and CRCs (n = 19) in 17 patients with HPS versus control groups of various sporadic polyps (n = 59) and sporadic microsatellite-stable CRCs (n = 16). In HPS and sporadic polyps, APC mutations were exclusively identified in adenomas, whereas BRAF mutations were confined to serrated polyps. Six of 19 HPS CRCs (32%) were identified in a serrated polyp. Mutation analysis performed in the CRC and the serrated component of these lesions showed identical BRAF mutations. One HPS CRC was located in an adenoma, both components harboring an identical APC mutation. Overall, 10 of 19 HPS CRCs (53%) carried a BRAF mutation versus none in control group CRCs (P = 0.001). Six BRAF-mutated HPS CRCs (60%) were microsatellite unstable owing to MLH1 methylation. These findings provide novel supporting evidence for the existence of a predominant serrated CRC pathway in HPS, generating microsatellite-stable and microsatellite-instable CRCs.
    American Journal Of Pathology 06/2011; 178(6):2700-7. · 4.60 Impact Factor
  • Gastroenterology 01/2010; 138(5). · 12.82 Impact Factor
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    ABSTRACT: The finding of bone morphogenetic protein (BMP) receptor 1a mutations in juvenile polyposis suggests that BMPs are important in colorectal cancer (CRC). We investigated the BMP pathway in sporadic CRC. We investigated BMP receptor (BMPR) expression using immunoblotting and sequenced BMPR2 in CRC cell lines. We assessed the expression of BMPRs, SMAD4, and pSMAD1/5/8 in 72 sporadic CRCs using a tissue microarray and immunohistochemistry. We assessed the effect of reintroduction of wild-type BMPR2 on BMP pathway activity and the effect of wild-type or mutated BMPR2 3' untranslated region (UTR) sequences on protein expression by attachment to pCMV-Luc. BMPR2 and SMAD4 protein expression is abrogated in microsatellite unstable (MSI) and microsatellite stable (MSS) cell lines, respectively. BMPR2 3'UTR is mutated in all MSI and in none of the MSS cell lines. Mutant BMPR2 3'UTR sequences reduced luciferase expression 10-fold compared with wild-type BMPR2 3'UTR. BMPR2 expression is impaired more frequently in MSI CRCs than MSS (85% vs 29%; P < .0001) and shows a mutually exclusive pattern of impaired expression compared with SMAD4. Nine of 11 MSI cancers with impaired expression of BMPR2 have microsatellite mutations. The BMP pathway is inactivated, as judged by nuclear pSMAD1/5/8 expression, in 70% of CRCs, and this correlates with BMPR and SMAD4 loss. Our data suggest that the BMP pathway is inactivated in the majority of sporadic CRCs. In MSI CRC this is associated predominantly with impaired BMPR2 expression and in MSS CRC with impaired SMAD4 expression.
    Gastroenterology 06/2008; 134(5):1332-41. · 12.82 Impact Factor
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    ABSTRACT: Post-translational cleavage of full-length cyclin E from the N-terminus can produce low molecular weight (LMW) isoforms of cyclin E containing the C-terminus only. To assess their presence in early-onset gastric cancer (EOGC), stump cancers and conventional gastric cancers and ascertain how they influence survival in EOGC. The expression of full-length and LMW isoforms of cyclin E in 330 gastric cancers, including early-onset gastric cancer (EOGC), stump cancer and conventional gastric cancer (>45 years old) was compared using antibodies targeted to the N- and C-terminals. LMW isoforms were found in 35% of EOGCs, compared to 8% of conventional gastric cancers and 4% of stump cancers; their presence was visualised in cell lines using western blot analysis. In addition, C-terminal staining was a positive predictor of survival in EOGC. In contrast, no correlation with survival was found with the N-terminal antibody which detects only full-length cyclin E. EOGCs have a unique molecular phenotype and LMW isoforms of cyclin E may independently influence survival in EOGC.
    Journal of clinical pathology 04/2008; 61(3):311-6. · 2.43 Impact Factor
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    ABSTRACT: Contemporary pathology involves an emerging role for molecular diagnostics. Current tissue handling procedures [ie, formalin fixation and paraffin embedment (FFPE)] have their origin in the aim to obtain good tissue morphology and optimal results within immunohistochemistry. Unfortunately, FFPE is notorious for its poor RNA conservation capacities. In this study, we have examined the impact of the individual steps in tissue handling processes on the RNA extractability, quality, and usability for reverse-transcription polymerase chain reaction. It was found that a prolonged prefixation time (ie, the time between tissue dissection and fixation) has a measurable impact on RNA integrity when analyzed with the Agilent Bioanalyzer. Surprisingly, however, the deteriorated RNA quality hardly had any consequences for reverse-transcription polymerase chain reaction yields. Furthermore, we assessed the optimal fixation time for RNA preservation, and we found that an RNA heating step, preceding copy DNA synthesis, significantly increases the RNA template length. Finally, we provide a protocol for RNA isolation from immunohistochemically stained FFPE tissue sections. Thus, by applying alterations to tissue handling procedures, archival FFPE tissues become well suitable for RNA-based molecular diagnostics.
    Diagnostic Molecular Pathology 04/2008; 17(1):51-8. · 1.86 Impact Factor
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    ABSTRACT: LKB1/STK11 germline inactivations are identified in the majority (66-94%) of Peutz-Jeghers syndrome (PJS) patients. Therefore, defects in other genes or so far unidentified ways of LKB1 inactivation may cause PJS. The genes encoding the MARK proteins, homologues of the Par1 polarity protein that associates with Par4/Lkb1, were analyzed in this study because of their link to LKB1 and cell polarity. The genetic defect underlying PJS was determined through analysis of both LKB1 and all four MARK genes. LKB1 point mutations and small deletions were identified in 18 of 23 PJS families using direct sequencing and multiplex ligation-dependent probe amplification analysis identified exon deletions in 3 of 23 families. In total, 91% of the studied families showed LKB1 inactivation. Furthermore, a MARK1, MARK2, MARK3 and MARK4 mutation analysis and an MARK4 quantitative multiplex polymerase chain reaction analysis to identify exon deletions on another eight PJS families without identified LKB1 germline mutation did not identify mutations in the MARK genes. LKB1 defects are the major cause of PJS and genes of the MARK family do not represent alternative PJS genes. Other mechanisms of inactivation of LKB1 may cause PJS in the remaining families.
    Clinical Genetics 01/2008; 72(6):568-73. · 3.94 Impact Factor
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    ABSTRACT: Transforming growth factor beta (TGFbeta) is important in colorectal cancer (CRC) progression. Bone morphogenetic proteins (BMPs), a subgroup within the TGFbeta superfamily, recently also have been implicated in CRC, but their precise role in CRC has yet to be investigated. The authors used a tissue microarray and immunohistochemistry of BMP receptors and signal transduction elements in adenomas and CRC specimens to elucidate the role of BMP signaling in CRC carcinogenesis. The adenoma specimens expressed all 3 BMP receptors (BMPRs) (BMPR type 1a [BMPR1a], BMPR1b, and BMPR2) and expressed SMAD family member 4 (SMAD4); and 20 of 22 adenomas (90.9%) exhibited active BMP signaling, as determined by nuclear phosphorylated SMAD1,5,8 (pSMAD1,5,8) expression. In contrast, pSMAD1,5,8 nuclear staining was present in 5 CRC specimens (22.7%) but was lost in 17 CRC specimens (77.3%; cancer vs adenoma; P< .0001). The earliest loss of pSMAD1,5,8 nuclear staining was detected in regions of high-grade dysplasia/carcinoma in situ within adenomas. CRCs showed frequent loss of BMPR2 (P< .0001) and SMAD4 (P< .01) compared with adenomas. Negative expression of BMPR2 was observed more frequently in earlier stage cancers (Dukes stage B) than in advanced cancers (Dukes stage C; P< .05). Taken together, the current results indicated that loss of BMP signaling correlates tightly with progression of adenomas to cancer and occurs relatively early during cancer progression.
    Cancer 01/2008; 112(2):300-6. · 5.20 Impact Factor
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    ABSTRACT: Three patients with graft-versus-host-like enterocolonopathy are reported. Their history was remarkable for thymoma and other autoimmune manifestations such as thrombocytopenia, red cell aplasia, interface dermatitis, Sjogren sialadenits, vanishing bile ducts and rheumatoid arthritis. In all patients, microsatellite analysis showed the autologous nature of the lymphocytes in the affected organs ruling out GVHD. In search for mechanisms that could mediate loss of tolerance to self-antigens we found in a panel of thymomas, including those of the three patients, a complete lack of autoimmune regulator (AIRE) and minimal expression of the transcription factor FOXP3 in the intra-tumoral T cells. AIRE is a recently discovered transcription factor which plays a key role in the maintenance of central tolerance and is mutated in the autosomal recessive autoimmune polyendocrinopathy syndrome APS-1. Our observations indicate that thymoma-related autoimmunity can potentially be elicited by an incomplete deletion of 'self'-specific T cells in concert with an insufficient formation of natural Tregs.
    Immunology Letters 12/2007; 114(1):31-7. · 2.34 Impact Factor
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    ABSTRACT: Many studies examine the molecular genetics of gastric cancer, but few look at young patients in particular and there is no comparison of molecular expression between early-onset gastric cancer (< or = 45 years old) and conventional gastric cancers. Expression of cycloxygenase-2 (COX-2) is elevated in gastric adenocarcinomas compared to non-neoplastic mucosa, and in light of studies showing reduced risk of gastric cancer in nonsteroidal anti-inflammatory drug users, we have chosen to investigate the expression of COX-2 and related molecules in 113 early-onset gastric cancers and compare it with 91 conventional gastric cancers, using tissue microarrays. These markers include molecules known to be important in conventional gastric carcinogenesis, such as E-Cadherin, p53, COX-2, Trefoil Factor-1 (TFF1), beta-catenin, p16 and c-myc; as well as molecules not yet described as being important in gastric cancer, such as the transcription factor c-jun, the COX-2 mRNA stabilizer HuR, and C/EBP-beta, a transcription factor for COX-2. All markers showed a statistically significant difference between early-onset gastric cancers and conventional gastric cancers, using a chi2 test. In particular, early-onset gastric cancers displayed a COX-2 Low, TFF1-expressing phenotype, whereas COX-2 overexpression and loss of TFF1 was found in conventional cancers, and this difference between early-onset gastric cancers and conventional cancers remained statistically significant when adjusted for location and histology (P<0.0001 and P = 0.002 respectively). We found that COX-2 overexpression correlates significantly with loss of TFF1 (P = 0.001), overexpression of C/EBP-beta (P<0.001) and cytoplasmic HuR (P = 0.016). COX-2 was significantly associated with p53 positivity (P = 0.003). Abnormalities in E-Cadherin correlated significantly with diffuse phenotype, whereas high expression of COX-2, loss of TFF1 and overexpression of C/EBP-beta correlated with the intestinal phenotype. Our results provide further evidence that early-onset gastric cancer exhibits a distinctive expression profile that may have practical implications.
    Modern Pathology 04/2006; 19(4):564-72. · 5.25 Impact Factor
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    ABSTRACT: LKB1 is a tumour suppressor gene that is associated with Peutz-Jeghers syndrome (PJS), a rare autosomal dominant cancer predisposition syndrome. However, germline mutations in the LKB1 gene are found in only about 60% of patients with PJS, suggesting the existence of a second PJS gene. The STRAD gene, encoding an LKB1 interacting protein that activates LKB1, which subsequently leads to polarisation of cells, is an interesting candidate for a second PJS gene and a potential tumour suppressor gene in sporadic carcinomas. The involvement of STRAD in 42 PJS associated tumours (sporadic lung, colon, gastric, and ovarian adenocarcinomas) was studied using loss of heterozygosity (LOH) analysis of eight microsatellite markers on chromosome 17, including TP53, BRCA1, and STRAD markers. Loss of the marker near the STRAD locus was seen in 13 of 29 informative cases, including all gastric adenocarcinomas. Specific LOH of the STRAD marker was found in four of 29 informative cases. For these patients all exons and exon-intron boundaries of the STRAD gene were sequenced, but no somatic mutations were identified. Furthermore, no germline STRAD mutations were found in 10 patients with PJS and family members without LKB1 germline mutation. Despite the frequent occurrence of LOH in the STRAD region, these results indicate that inactivation of the STRAD gene is not essential in the sporadic adenocarcinomas studied, although it is possible that STRAD may be inactivated in different ways. In addition, no evidence was found for the hypothesis that STRAD is a second PJS susceptibility gene.
    Journal of Clinical Pathology 11/2005; · 2.44 Impact Factor
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    ABSTRACT: Sulindac causes the reduction of adenomas in familial adenomatous polyposis (FAP) patients, but complete regression is unusual, and breakthrough of colorectal carcinoma during sulindac treatment has been described. The molecular features related to sulindac resistance are unknown. Therefore, we investigated molecular alterations in adenomas from FAP patients with complete adenoma regression on sulindac (responsive patients) and from FAP patients with sulindac-resistant adenomas (resistant patients). Fourteen baseline adenomas (removed before sulindac treatment) from six responsive patients were studied. Also, 9 baseline adenomas and 34 resistant adenomas (removed during sulindac treatment) from three resistant patients were analyzed. Using immunohistochemistry, we evaluated the expression of beta-catenin, cyclooxygenase-2 (Cox-2), p53, Bcl-2, and Bax. K-ras codon 12 mutations, loss of heterozygosity at 5q (APC locus), and microsatellite instability were studied with PCR-based techniques. There were no significant differences between baseline adenomas from sulindac-responsive and -resistant patients (P > 0.05). There was less loss of membranous beta-catenin staining and less nuclear beta-catenin accumulation in resistant adenomas compared with baseline adenomas from the same (sulindac-resistant) patients (P < 0.01) or baseline adenomas from responsive patients (P < 0.01). Epithelial Cox-2 expression was less, though not significant, in resistant adenomas compared with baseline adenomas from resistant patients, but was significantly less in baseline adenomas from responsive patients (P < 0.01). K-ras mutations were found in 8 of 34 resistant adenomas (24%) and in none of the baseline adenomas (P < 0.05). Stromal Cox-2 expression, staining of p53 and Bcl-2, and loss of heterozygosity at 5q were comparable in both groups. Loss of Bax staining and microsatellite instability were not found in any adenoma. Sulindac-resistant adenomas display less alteration in beta-catenin staining and less epithelial Cox-2 expression when compared with adenomas removed before sulindac treatment. K-ras mutations may contribute to sulindac-resistance. Continued research is needed to investigate molecular alterations related to sulindac resistance.
    Clinical Cancer Research 12/2001; 7(12):4000-7. · 7.84 Impact Factor
  • Gastroenterology 01/2001; 120(5). · 12.82 Impact Factor
  • Gastroenterology 01/2001; 120(5). · 12.82 Impact Factor
  • Gastroenterology 01/2000; 118(4). · 12.82 Impact Factor
  • Gastroenterology 01/2000; 118(4). · 12.82 Impact Factor
  • Gastroenterology 01/2000; 118(4). · 12.82 Impact Factor
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    ABSTRACT: Partial gastrectomy is a well-established pre-malignant condition. It is postulated that in the gastric stump an accelerated neoplastic process takes place, similar to that of (intestinal type) adenocarcinoma from the non-operated stomach. K-ras codon 12 mutation is one of the most frequent oncogenic alterations in human solid neoplasms. It is rare in conventional gastric carcinoma and has not been studied in gastric stump carcinoma. The aim of this study was to compare the prevalence of K-ras codon 12 point mutations in gastric stump carcinomas with those in conventional carcinomas from the non-operated stomach. Twenty-four gastric stump carcinomas were compared with 26 conventional gastric carcinomas. Stage, histology, and demographics were comparable in both groups. Mutations in codon 12 of the K-ras gene were examined with a polymerase chain reaction (PCR)-based method and subsequent dot blot hybridization with mutation-specific probes. The results of Helicobacter pylori infection, Epstein-Barr virus infection and p53 immunohistochemistry were partially known from a previous study. In one of the gastric stump carcinomas as well as in one of the conventional gastric carcinomas a K-ras codon 12 point mutation was found. p53 immunohistochemistry results were comparable in both groups. Interestingly, Helicobacter pylori infection rate and Epstein-Barr virus in situ hybridization for EBER1, as previously studied, appeared were significantly different in the two groups. K-ras codon 12 point mutations are rare in both gastric stump carcinomas and conventional gastric carcinomas. This supports the postulated hypothesis that the pathways of carcinogenesis in both gastric stump carcinoma and conventional gastric carcinoma share common features. However, these groups differ in infection rate of Helicobacter pylori and of Epstein-Barr virus, which suggests that some neoplastic stimuli differ as well.
    Hepato-gastroenterology 01/1999; 46(27):2063-8. · 0.77 Impact Factor

Publication Stats

347 Citations
148.83 Total Impact Points

Institutions

  • 2006–2011
    • Academisch Medisch Centrum Universiteit van Amsterdam
      • • Department of Gastroenterology and Hepatology
      • • Department of Pathology
      Amsterdam, North Holland, Netherlands
  • 2008
    • Academic Medical Center (AMC)
      Amsterdamo, North Holland, Netherlands
  • 2007
    • University Medical Center Utrecht
      • Department of Pathology
      Utrecht, Provincie Utrecht, Netherlands
  • 1998–1999
    • University of Amsterdam
      • • Faculty of Medicine AMC
      • • Department of Pathology
      Amsterdam, North Holland, Netherlands
  • 1997
    • Johns Hopkins Medicine
      • Department of Pathology
      Baltimore, MD, United States