Deregulation of PAX2 expression in renal cell tumours: mechanisms and potential use in differential diagnosis

Authors

  • Patrícia Patrício,

    1. Cancer Epigenetics Group, Research Center of the Portuguese Oncology Institute - Porto, Porto, Portugal
    2. Department of Genetics, Portuguese Oncology Institute – Porto, Porto, Portugal
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  • João Ramalho-Carvalho,

    1. Cancer Epigenetics Group, Research Center of the Portuguese Oncology Institute - Porto, Porto, Portugal
    2. Department of Genetics, Portuguese Oncology Institute – Porto, Porto, Portugal
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  • Pedro Costa-Pinheiro,

    1. Cancer Epigenetics Group, Research Center of the Portuguese Oncology Institute - Porto, Porto, Portugal
    2. Department of Genetics, Portuguese Oncology Institute – Porto, Porto, Portugal
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  • Mafalda Almeida,

    1. Cancer Epigenetics Group, Research Center of the Portuguese Oncology Institute - Porto, Porto, Portugal
    2. Department of Genetics, Portuguese Oncology Institute – Porto, Porto, Portugal
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  • João Diogo Barros-Silva,

    1. Department of Genetics, Portuguese Oncology Institute – Porto, Porto, Portugal
    2. Cancer Genetics Group, Research Center of the Portuguese Oncology Institute - Porto, Porto, Portugal
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  • Joana Vieira,

    1. Department of Genetics, Portuguese Oncology Institute – Porto, Porto, Portugal
    2. Cancer Genetics Group, Research Center of the Portuguese Oncology Institute - Porto, Porto, Portugal
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  • Paula Cristina Dias,

    1. Department of Pathology, Portuguese Oncology Institute – Porto, Porto, Portugal
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  • Francisco Lobo,

    1. Department of Urology, Portuguese Oncology Institute – Porto, Porto, Portugal
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  • Jorge Oliveira,

    1. Department of Urology, Portuguese Oncology Institute – Porto, Porto, Portugal
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  • Manuel R. Teixeira,

    1. Department of Genetics, Portuguese Oncology Institute – Porto, Porto, Portugal
    2. Cancer Genetics Group, Research Center of the Portuguese Oncology Institute - Porto, Porto, Portugal
    3. Department of Pathology and Molecular Immunology, Institute of Biomedical Sciences Abel Salazar, University of Porto, Porto, Portugal
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  • Rui Henrique,

    1. Cancer Epigenetics Group, Research Center of the Portuguese Oncology Institute - Porto, Porto, Portugal
    2. Department of Pathology, Portuguese Oncology Institute – Porto, Porto, Portugal
    3. Department of Pathology and Molecular Immunology, Institute of Biomedical Sciences Abel Salazar, University of Porto, Porto, Portugal
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    • Joint senior authors.
  • Carmen Jeronimo

    Corresponding author
    1. Department of Genetics, Portuguese Oncology Institute – Porto, Porto, Portugal
    2. Department of Pathology and Molecular Immunology, Institute of Biomedical Sciences Abel Salazar, University of Porto, Porto, Portugal
    • Cancer Epigenetics Group, Research Center of the Portuguese Oncology Institute - Porto, Porto, Portugal
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    • Joint senior authors.

Correspondence to: Carmen JERÓNIMO, Ph.D., Research Center/ Department of Genetics, Portuguese Oncology Institute-Porto, Rua Dr. António Bernardino Almeida, Porto 4200-072, Portugal.

Tel.: +351 225084000 (ext. 7264)

Fax: + 351 225084016

E-mails: carmenjeronimo@ipoporto.min-saude.pt/cljeronimo@icbas.up.pt

Abstract

Expression of PAX2 (Paired-box 2) is suppressed through promoter methylation at the later stages of embryonic development, but eventually reactivated during carcinogenesis. Pax-2 is commonly expressed in the most prevalent renal cell tumour (RCT) subtypes—clear cell RCC (ccRCC), papillary RCC (pRCC) and oncocytoma—but not in chromophobe RCC (chrRCC), which frequently displays chromosome 10 loss (to which PAX2 is mapped). Herein, we assessed the epigenetic and/or genetic alterations affecting PAX2 expression in RCTs and evaluated its potential as biomarker. We tested 120 RCTs (30 of each main subtype) and four normal kidney tissues. Pax-2 expression was assessed by immunohistochemistry and PAX2 mRNA expression levels were determined by quantitative RT-PCR. PAX2 promoter methylation status was assessed by methylation-specific PCR and bisulfite sequencing. Chromosome 10 and PAX2 copy number alterations were determined by FISH. Pax-2 immunoexpression was significantly lower in chrRCC compared to other RCT subtypes. Using a 10% immunoexpression cut-off, Pax-2 immunoreactivity discriminated chrRCC from oncocytoma with 67% sensitivity and 90% specificity. PAX2 mRNA expression was significantly lower in chrRCC, compared to ccRCC, pRCC and oncocytoma, and transcript levels correlated with immunoexpression. Whereas no promoter methylation was found in RCTs or normal kidney, 69% of chrRCC displayed chromosome 10 monosomy, correlating with Pax-2 immunoexpression. We concluded that Pax-2 expression might be used as an ancillary tool to discriminate chrRCC from oncocytomas with overlapping morphological features. The biological rationale lies on the causal relation between Pax-2 expression and chromosome 10 monosomy, but not PAX2 promoter methylation, in chrRCC.

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