The lack of epithelial interleukin-7 and BAFF/BLyS gene expression in prostate cancer as a possible mechanism of tumor escape from immunosurveillance

Clin Cancer Res. 2009 May 1;15(9):2979-87. doi: 10.1158/1078-0432.CCR-08-1951. Epub 2009 Apr 14.

Abstract

Purpose: The human prostate is endowed with intraepithelial and stromal lymphocytes, which may develop lymphoid follicles (LF) and allow a local immune response. We sought to investigate whether interleukin (IL)-7 and BAFF/BLyS, two fundamental survival factors for T and B cells, are expressed in the normal and neoplastic prostate and affect intraprostatic lymphocyte homeostasis.

Experimental design: We have used real-time reverse transcription-PCR of microdissected prostatic glands and confocal microscopy to detect cytokine production, combined with immunohistochemistry to characterize intraprostatic lymphocytes.

Results: Prostatic epithelia constitutively produce IL-7 and, to a lesser extent, BAFF/BLyS. Indeed, we show that IL-7 receptor alpha is expressed by intraepithelial T lymphocytes and parafollicular T cells, whereas BAFF-R is found on periglandular B lymphocytes and mantle zone B cells of LFs. Prostate-homing B and T lymphocytes are scarcely proliferating, whereas most of them express the antiapoptotic protein bcl-2 and reveal a low apoptotic index in the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. The transition from normal to neoplastic glands in prostate cancer (PCa) is marked by a dramatic decline of IL-7 and BAFF/BLyS production. Accordingly, PCa is characterized by a significant reduction of intraepithelial lymphocytes and loss of LFs. B-cell and T-cell expression of bcl-2 decrease, whereas the apoptotic events increase. The remaining PCa-infiltrating lymphocytes are mostly CD8(+) T cells that lack terminal differentiation and barely penetrate neoplastic glands.

Conclusions: These results suggest that epithelial IL-7 and BAFF/BLyS production support intraprostatic lymphocyte survival. Its loss in PCa is associated with a severe depletion of prostate-associated lymphocytes and points to a novel tumor escape mechanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects
  • Apoptosis / immunology
  • B-Cell Activating Factor / genetics*
  • B-Lymphocytes / immunology
  • B-Lymphocytes / metabolism
  • B-Lymphocytes / pathology
  • Blotting, Western
  • Epithelial Cells / metabolism
  • Epithelial Cells / pathology
  • Gene Expression Regulation, Neoplastic / physiology*
  • Humans
  • Immunoenzyme Techniques
  • Interleukin-7 / genetics*
  • Interleukin-7 Receptor alpha Subunit / genetics
  • Lymphocytes, Tumor-Infiltrating / immunology
  • Male
  • Middle Aged
  • Monitoring, Immunologic*
  • Prostate / immunology
  • Prostate / metabolism
  • Prostate / pathology*
  • Prostatic Neoplasms / genetics*
  • Prostatic Neoplasms / immunology*
  • Prostatic Neoplasms / pathology
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • T-Lymphocytes / immunology
  • T-Lymphocytes / metabolism
  • T-Lymphocytes / pathology
  • Tumor Escape*

Substances

  • B-Cell Activating Factor
  • Interleukin-7
  • Interleukin-7 Receptor alpha Subunit
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Messenger
  • TNFSF13B protein, human