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


METHODS
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.
Di Carlo
Emma
E
Department of Oncology and Neurosciences, G. d'Annunzio University, Italy. ediccarlo@unich.it
D'Antuono
Tommaso
T
Pompa
Paolo
P
Giuliani
Rossella
R
Rosini
Sandra
S
Stuppia
Liborio
L
Musiani
Piero
P
Sorrentino
Carlo
C
D017209:Apoptosis / Q000187:drug effects / Q000276:immunology; D053264:B-Cell Activating Factor / Q000235:genetics*; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D015153:Blotting, Western; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006801:Humans; D007124:Immunoenzyme Techniques; D015851:Interleukin-7 / Q000235:genetics*; D053699:Interleukin-7 Receptor alpha Subunit / Q000235:genetics; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology; D008297:Male; D008875:Middle Aged; D015166:Monitoring, Immunologic; D011467:Prostate / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000276:immunology* / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D019139:Tumor Escape
D053264:B-Cell Activating Factor; D015851:Interleukin-7; D053699:Interleukin-7 Receptor alpha Subunit; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; C505719:TNFSF13B protein, human