The most effective but largely ignored target for prostate cancer early detection and intervention

Abstract

Over the past two decades, the global efforts for the early detection and intervention of prostate cancer seem to have made significant progresses in the basic researches, but the clinic outcomes have been disappointing: (1) prostate cancer is still the most common non-cutaneous cancer in Europe in men, (2) the age-standardized prostate cancer rate has increased in nearly all Asian and African countries, (3) the proportion of advanced cancers at the diagnosis has increased to 8.2% from 3.9% in the USA, (4) the worldwide use of PSA testing and digital rectal examination have failed to reduce the prostate cancer mortality, and (5) there is still no effective preventive method to significantly reduce the development, invasion, and metastasis of prostate cancer… Together, these facts strongly suggest that the global efforts during the past appear to be not in a correlated target with markedly inconsistent basic research and clinic outcomes. The most likely cause for the inconsistence appears due to the fact that basic scientific studies are traditionally conducted on the cell lines and animal models, where it is impossible to completely reflect or replicate the in vivo status. Thus, we would like to propose the human prostate basal cell layer (PBCL) as "the most effective target for the early detection and intervention of prostate cancer". Our proposal is based on the morphologic, immunohistochemical and molecular evidence from our recent studies of normal and cancerous human prostate tissues with detailed clinic follow-up data. We believe that the human tissue-derived basic research data may provide a more realistic roadmap to guide the clinic practice and to avoid the potential misleading from in vitro and animal studies.

Keywords: Cancer early detection and intervention.; Prostate basal cell layer; Tumor capsule.

Figure 1

Structural relationships of prostate gland tissue components. Formalin-fixed and paraffin-embedded human prostate gland tissue sections were double immune-stained, 1A and 1B with antibodies to smooth muscle actin (SMA) that is reactive to the basement membrane (BM), smooth muscle, and endothelial cells, and CK34βE12, which is reactive to PBCL; 1C and 1D with SMA plus p63, which is reactive to PBCL. EP = Epithelium.

Figure 2

Expression of tumor suppressors p63 and Maspin in PBCL. Formalin-fixed and paraffin-embedded human prostate gland sections were double immune-stained, 2A with CK34βE12 (red) and p63 (black); 2B with Maspin (red) and p63 (black). Please note that the normal PBCL is continuous and the basal cells express a high level of Maspin and p63. PBCL = Prostate basal cell layer. EP = Epithelium.

Figure 3

Focal PBCL senescence or degenerative changes. Formalin-fixed and paraffin-embedded human prostate gland tissue sections were double immune-stained (see the detailed labeling within individual figures). Circles identify focal PBCL disruptions; Squares identify large clusters of basal cell debris; Thick arrows in A and B identify basal cells with the loss of nuclear p63 expression; Thin arrows identify the residual PBCL; Red stars identify invasive lesions. Please note that the size of the focal disruptions in PBCL varies substantially, and that the epithelial cells overlying focally disrupted PBCL are morphologically more similar to the adjacent invasive cancer cells with a higher proliferation rate than their adjacent counterparts still enclosed by the residual PBCL.

Figure 4

Focal PBCL disruptions and cancer invasion. Formalin-fixed and paraffin-embedded human prostate gland tissue sections were double immune-stained with several antibodies (see labeling within each individual picture). Circles identify focal disruptions in PBCL and the overlying epithelial cells. Thick arrows identify the normal or residual PBCL Thin arrows identify proliferating cells. Red starts identify invasive lesions. Please note that the budding cells overlying focally disrupted PBCL have a significantly higher proliferation rate than their counterparts enclosed by the residual PBCL, and that budding cells are immediately adjacent to or in a direct continuity with invasive lesions.

Figure 5

Gene expression profiling of cells overlying focally disrupted and enclosed by residual PBCL. Formalin-fixed and paraffin-embedded human prostate gland tissue sections were double immune-stained with antibodies for SMA and Ki-67. Thick arrows identify residual PBCL. Thin arrows identify proliferating epithelial cells. The square identifies epithelial cells overlying focally disrupted FBCL, and the circle identifies epithelial cells enclosed by the residual FBCL micro-dissected for gene expression profiling. Please note that morphologically comparable epithelial cells overlying focally disrupted PBCL and enclosed by the residual PBCL have different profiles of the gene expression.

Figure 6

Significantly reduced basal cell numbers of p63 expression in normal appearing PBCL. Formalin-fixed and paraffin-embedded human prostate gland tissue sections from two different biopsies with morphologically normal appearing basal cell layers associated with a morphologically normal appearing epithelial cell population were double immune-stained with p63 and Maspin. In the cases one, a vast majority of the normal appearing basal cells display the distinct expression of p63 within the cell nuclei. However, in a sharp contrast in the case two, only around 1-3% of the normal appearing basal cells show the normal localization of p63 expression within the cell nuclei. Circles identify normal appearing basal cells in the case 2, which display a high level of Maspin expression within the cell cytoplasm, whereas they are completely devoid of p63 expression within the cell nuclei despite the fact that the nuclei of these basal cells are clearly visible. 6B and 6D are the higher magnification of 6A and 6C, respectively.

Figure 7

The lack of all basal cell markers in the PBCL of pre-invasive prostate cancer clusters. Formalin-fixed and paraffin-embedded consecutive human prostate gland tissue sections from one case were subjected to H&E staining (7A-7B) and IHC staining (7C-7F) for different biomarkers (see detailed labeling within each individual picture). Red starts identify invasive lesions. Thin arrows identify atypical basal cells. Thick arrows identify normal basal cells. Please note that the PBCL overlying a walnut-like tumor nest is morphologically distinct in both H&E and IHC stained sections, but all basal cells are completely devoid of the expression of CK34βE12, p63, and Maspin. In addition, these morphologically distinct basal cells are also completely devoid of the expression of proliferating cell nuclear antigen (PCNA), in a sharp contrast to the enclosed epithelial cells, which are all strongly immunoreactive to PCNA.

Figure 8

Apoptosis-related alterations in degenerated basal cells. Formalin-fixed and paraffin-embedded human prostate gland tissue sections were subjected to the apoptotic assays with a commercially available detection kit, and then, were immune-stained for CK34βE12 to elucidate PBCL. Arrows identify PBCL. Squares identify apoptotic basal cells. Circles identify epithelial cells overlying or near the focally disrupted PBCL.

Figure 9

Physical association of infiltrating immune cells with degenerated basal cells. Formalin-fixed and paraffin-embedded human prostate tissue sections from four different cases were subjected to double IHC staining with the basal specific marker CK34βE12 and infiltrating immune cell marker (leukocyte common antigen, LCA). Thick arrows identify residual basal cells. Thin arrows identify infiltrating immune cells. Please note that a vast majority of infiltrating immune cells are physically associated with or immediately adjacent to degenerative basal cells. The epithelial component or the acinar and ductal lumen in focally disrupted PBCL often harbor infiltrating immune cells. It is interesting to note that nearly all the normal, benign, and malignant epithelial cells show no distinct sign of degeneration-related alterations.

Figure 10

Tenascin expression at the site of focally disrupted PBCL. Formalin-fixed and paraffin-embedded human prostate gland tissue sections from two different cases were double immune-stained for CK34βE12 (red) and Tenascin C (brown). Arrows identify residual basal cells. Squares enclose Tenascin C overlying focally disrupted PBCL. Please note that strong Tenascin C positivity is seen only at or adjacent to the site of focally disrupted PBCL. Non-disrupted PBCLs are largely devoid of Tenascin C expression.