p63 is a prostate basal cell marker and is required for prostate development

Abstract

The p53 homologue p63 encodes for different isotypes able to either transactivate p53 reporter genes (TAp63) or act as p53-dominant-negatives (DeltaNp63). p63 is expressed in the basal cells of many epithelial organs and its germline inactivation in the mouse results in agenesis of organs such as skin appendages and the breast. Here, we show that prostate basal cells, but not secretory or neuroendocrine cells, express p63. In addition, prostate basal cells in culture predominantly express the DeltaNp63alpha isotype. In contrast, p63 protein is not detected in human prostate adenocarcinomas. Finally, and most importantly, p63(-/-) mice do not develop the prostate. These results indicate that p63 is required for prostate development and support the hypothesis that basal cells represent and/or include prostate stem cells. Furthermore, our results show that p63 immunohistochemistry may be a valuable tool in the differential diagnosis of benign versus malignant prostatic lesions.

Figure 1.

Sequences, amplicon sizes, and exon localizations of primers and probes used for Taqman® PCR experiment.

Figure 2.

a: Normal prostate gland showing selective p63 nuclear expression in basal cells. b: Double-immunostaining for p63 (black nuclear staining) and chromogranin A (red cytoplasmic staining): neuroendocrine cells do not express p63. c: Double-immunostaining for p63 (black nuclear staining) and HMWCK (red cytoplasmic staining): the majority of basal cells co-express p63 and HMWCK. A subset of basal cells expresses p63 only. d: Prostate gland with basal cell hyperplasia double-immunostained for p63 (brown nuclear staining) and HMWCK (red cytoplasmic staining): a subset of p63-positive and HMWCK-negative basal cells is identified. e: Dysplastic cells from high-grade prostatic intraepithelial neoplasia glands are negative for p63 expression whereas a rim of residual p63-positive basal cells can be identified. f: Prostate cancer cells do not express p63 (left) whereas an adjacent normal prostate gland (right) shows p63 expression in basal cells.

Figure 3.

a: p63 protein is expressed in the nuclei of ∼80% of normal basal prostate PrEC cells by immunohistochemistry. LNCaP (b), PC3 (c), and DU145 (d) cells do not express p63 protein. e: Immunoblotting of PrEC cell lysate (lane 1) with anti-p63 antibody shows a major band at ∼80 kd and a fainter band at ∼60 kd. LNCaP (lane 2), PC3 (lane 3) and DU145 (lane 4) cells are negative for p63 protein expression by immunoblotting.

Figure 4.

a: A coronal section of the periurethral region of a wild-type mouse shows the presence of prostatic buds (arrowheads) in both the ventral (V) and dorsolateral periurethral region. Arrows indicate ejaculatory ducts. By immunohistochemistry, basal urothelial and prostatic cells express p63 (inset). b: A coronal section of the periurethral region of a p63(−/−) mouse shows complete absence of prostatic ducts or budding structures in both the ventral (V) and dorsolateral region of the periurethral mesenchyma. p63 expression could not be detected in either epithelial or stromal cells by immunohistochemistry (inset). Ejaculatory ducts (arrows) are present in the posterior periurethral region. Detached urothelial cells are present within the urethral lumen.