A subset of prostate basal cells lacks the expression of corresponding phenotypic markers

A transgenic mouse model for early prostate metastasis to lymph nodes

The emergence of recurrent, metastatic prostate cancer following the failure of androgen-deprivation therapy represents the lethal phenotype of this disease. However, little is known regarding the genes and pathways that regulate this metastatic process, and moreover, it is unclear whether metastasis is an early or late event. The individual genetic loss of the metastasis suppressor, SSeCKS/Gravin/AKAP12 or Rb, genes that are downregulated or deleted in human prostate cancer, results in prostatic hyperplasia. Here, we show that the combined loss of Akap12 and Rb results in prostatic intraepithelial neoplasia (PIN) that fails to progress to malignancy after 18 months. Strikingly, 83% of mice with PIN lesions exhibited metastases to draining lymph nodes, marked by relatively differentiated tumor cells expressing markers of basal (p63, cytokeratin 14) and luminal (cytokeratin 8 and androgen receptor) epithelial cells, although none expressed the basal marker, cytokeratin 5. The finding that PIN lesions contain increased numbers of p63/AR-positive, cytokeratin 5-negative basal cells compared with WT or Akap12-/- prostate lobes suggests that these transitional cells may be the source of the lymph node metastases. Taken together, these data suggest that in the context of Rb loss, Akap12 suppresses the oncogenic proliferation and early metastatic spread of basal-luminal prostate tumor cells.

The myoepithelial cell layer may serve as a potential trigger factor for different outcomes of stage-matched invasive lobular and ductal breast cancers

Invasive lobular cancer (ILC) tends to be significantly larger in size with significantly more positive lymph nodes, whereas ILC has a significantly more favorable outcome, compared to stage-matched invasive ductal carcinoma (IDC). The mechanism accounting for such differences remains elusive. Based on morphological, immunohistochemical, and molecular studies of over 1,000 cases of human breast cancers, we hypothesize that the differences may result from the structural and/or functional differences of their surrounding myoepithelial cell layers, which dictate lobular and ductal tumor cells to follow different pathways of invasion or metastasis. The background, rationale, supportive data, and implications of our hypothesis are presented and discussed.

Metastasis suppressors in human benign prostate, intraepithelial neoplasia, and invasive cancer: their prospects as therapeutic agents

Despite advances in diagnosis and treatment of prostate cancer, development of metastases remains a major clinical challenge. Research efforts are dedicated to overcome this problem by understanding the molecular basis of the transition from benign cells to prostatic intraepithelial neoplasia (PIN), localized carcinoma, and metastatic cancer. Identification of proteins that inhibit dissemination of cancer cells will provide new perspectives to define novel therapeutics. Development of antimetastatic drugs that trigger or mimic the effect of metastasis suppressors represents new therapeutic approaches to improve patient survival. This review focuses on different biochemical and cellular functions of metastasis suppressors known to play a role in prostate carcinogenesis and progression. Ten putative metastasis suppressors implicated in prostate cancer are discussed. CD44s is decreased in both PIN and cancer; Drg-1, E-cadherin, KAI-1, RKIP, and SSeCKS show similar expression between benign epithelia and PIN, but are downregulated in invasive cancer; whereas, maspin, MKK4, Nm23 and PTEN are upregulated in PIN and downregulated in cancer. Moreover, the potential role of microRNA in prostate cancer progression, the understanding of the cellular distribution and localization of metastasis suppressors, their mechanism of action, their effect on prostate invasion and metastasis, and their potential use as therapeutics are addressed.

Study of immunohistochemistry in prostatic lesions with special reference to proliferation and invasiveness

Prostatic lesions on routine staining sometimes cause diagnostic dilemma especially in premalignant lesions like atypical adenomatous hyperplasia and prostatic intraepithelial neoplasia. Benign small acinar lesions also may be difficult to differentiate from small acinar adenocarcinoma. An important differentiating point is the loss of basal cell layer in adenocarcinoma and its presence in benign lesions. Basal cell markers (e.g. 34βE12 cytokeratin) & proliferative markers (e.g. AgNOR and PCNA) can help in this regard. Total 60 cases of different prostatic lesions studied. After history taking, clinical examination, radiological & other investigations were done. Routine H&E staining, immunohistochemical staining against 34βE12 cytokeratin & proliferative markers (AgNOR & PCNA) was performed. Statistically significant differences found in expression of 34βE12 cytokeratin and proliferative markers between benign, premalignant and malignant prostatic lesions. Basal cell markers and proliferative markers are important parameters to distinguish between different benign, premalignant and malignant prostatic lesions.

Reliability of the 34βE12, keratin 5/6, p63, bcl-2, and AMACR in the diagnosis of prostate carcinoma

OBJECTIVE

In this study, we aimed to investigate which basal cell marker should be used with α-methylacyl coenzyme A racemase (AMACR) to increase diagnostic accuracy in the diagnosis of prostate carcinoma.

MATERIALS AND METHODS

A total of 98 cases of prostate biopsy, comprising 65 cases with prostate adenocarcinoma and 33 cases without adenocarcinoma, were included in this study. Prostate-specific antigen (PSA) serum levels before biopsies were obtained. The number of cores with malignant glands and Gleason scores for each case were determined. Paraffin sections were stained immunohistochemically with 34βE12, keratin 5/6, p63, bcl-2, and AMACR.

RESULTS

According to staining pattern, extensiveness, and intensity of basal cell markers in benign glands, 34βE12 gave the best results. As negative markers for prostate adenocarcinoma, the best markers were p63 and 34βE12. According to the AUC values in ROC curves for both extensiveness and intensity, the arrangement from the best to the worst was 34βE12, p63, bcl-2, and keratin 5/6. The 34βE12 had the best sensitivity and specificity values (95% and 98%, respectively). Staining extensiveness and intensity of keratin 5/6 in malignant glands, and those of bcl-2 in benign glands had statistically significant positive correlation with serum PSA levels. Even though AMACR is a negative marker for benignity, some of the benign glands also had positive immune reaction with AMACR. However, AMACR positivity was usually focal and weak. Nevertheless, intensively stained subjects were also present. No correlation was present between AMACR and basal cell markers.

CONCLUSIONS

As a result, we suggest that keratin 5/6 and bcl-2 should not be used to identify benign glands in prostate biopsy since they show high positivity in malignant glands and high negativity in benign glands. 34βE12 should be the first choice as a basal cell marker. p63 can be used together with 34βE12, but it may not give additional diagnostic information. When we evaluated the correlation of basal cell markers, we did not find any complementary staining results among basal cell markers. Our study showed that 34βE12 is the most appropriate negative marker to combine with AMACR as a positive marker for the diagnosis of prostate adenocarcinoma.

Correlated alterations in prostate basal cell layer and basement membrane

Our recent studies revealed that focal basal cell layer disruption (FBCLD) induced auto-immunoreactions represented a contributing factor for human prostate tumor progression and invasion. As the basement membrane surrounds and attaches to the basal cell layer, our current study assessed whether FBCLD would impact the physical integrity of the associated basement membrane. Paraffin sections from 25-human prostate tumors were subjected to double immunohistochemistry to simultaneously elucidate the basal cell layer and the basement membrane with corresponding biomarkers. The physical integrity of the basement membrane overlying FBCLD was examined to determine the extent of correlated alterations. Of a total of 89 FBCLD encountered, 76 (85 %) showed correlated alterations in the overlying basement membrane, which included distinct focal disruptions or fragmentations. In the remaining 13 (15%) FBCLD, the overlying basement membrane showed significant attenuation or reduction of the immunostaining intensity. The basement membrane in all or nearly all ducts or acini with p63 positive basal cells was substantially thicker and more uniform than that in ducts or acini without p63 positive basal cells, and also, a vast majority of the focal disruptions occurred near basal cells that lack p63 expression. These findings suggest that focal disruptions in the basal cell layer and alterations in the basement membrane are correlated events and that the physical and functional status of the basal cells could significantly impact the physical integrity of the overlying basement membrane. As the degradation of both the basal cell layer and the basement membrane is a pre-requisite for prostate tumor invasion or progression, ducts or acini with focally disrupted basal cell layer and basement membrane are likely at greater risk to develop invasive lesions. Thus, further elucidation of the specific molecules and mechanism associated with these events may lead to the development of a more effective alternative for repeat biopsy to monitor tumor progression and invasion.

Bad seeds produce bad crops: a single stage-process of prostate tumor invasion

It is a commonly held belief that prostate carcinogenesis is a multi-stage process and that tumor invasion is triggered by the overproduction of proteolytic enzymes. This belief is consistent with data from cell cultures and animal models, whereas is hard to interpret several critical facts, including the presence of cancer in "healthy" young men and cancer DNA phenotype in morphologically normal prostate tissues. These facts argue that alternative pathways may exist for prostate tumor invasion in some cases. Since degradation of the basal cell layer is the most distinct sign of invasion, our recent studies have attempted to identify pre-invasive lesions with focal basal cell layer alterations. Our studies revealed that about 30% of prostate cancer patients harbored normal appearing duct or acinar clusters with a high frequency of focal basal cell layer disruptions. These focally disrupted basal cell layers had significantly reduced cell proliferation and tumor suppressor expression, whereas significantly elevated degeneration, apoptosis, and infiltration of immunoreactive cells. In sharp contrast, associated epithelial cell had significantly elevated proliferation, expression of malignancy-signature markers, and physical continuity with invasive lesions. Based on these and other findings, we have proposed that these normal appearing duct or acinar clusters are derived from monoclonal proliferation of genetically damaged stem cells and could progress directly to invasion through two pathways: 1) clonal in situ transformation (CIST) and 2) multi-potential progenitor mediated "budding" (MPMB). These pathways may contribute to early onset of prostate cancer at young ages, and to clinically more aggressive prostate tumors.

Correlation of p63 immunoreactivity with tumor grade in meningiomas

Predicting tumor behavior in meningiomas based on morphologic features alone remains difficult. The present study was undertaken to assess the correlation between p63 expression and histological grade of meningiomas. A total of 37 archival intracranial meningiomas were classified into 20 grade I, 13 grade II, and 4 grade III meningiomas. Using immunohistochemical methods, staining was scored based on nuclear and/or cytoplasmic distribution as follows: 0, no staining; 1, 50% or less of the cells; 2, more than 50% of the cells. Of grade I meningiomas, 95% (19/20) lacked nuclear p63 expression and none exhibited cytoplasmic staining. Overall, 92% of grade II tumors showed nuclear expression and 31% (4/13) showed cytoplasmic expression. Grade III tumors showed an overall nuclear expression of 75% (3/4) with all exhibiting cytoplasmic staining. Our results indicate a good correlation exists between histological grade and p63 protein expression, suggesting that p63 expression might be correlated with the clinical outcome.

Prostatic basal cells in the peripheral and transitional zones: zonal variation in morphology and in immunophenotype

BACKGROUND

Benign prostatic hyperplasia and prostatic adenocarcinoma exhibit prominent zonal predilections. Basal cells from the transitional zone and from the peripheral zone are postulated to have different underlying biological properties. We studied basal cells in both prostatic zones.

METHODS

Tissue microarrays (TMA) were prepared from 65 whole-mounted prostatectomy specimens with prostatic adenocarcinoma. The transitional zone and peripheral zone were sampled from each prostate. TMA sections were stained with a basal cell cocktail (CK 34betaE12 + p63). The immunostaining pattern and the morphology of basal cells were recorded.

RESULTS

Triangular-shaped basal cells were highlighted by CK 34betaE12 cytoplasmic and p63 nuclear staining. These basal cells had their long axis oriented perpendicular to the basement membrane and their apex toward the lumen interdigited between secretory luminal cells. This morphology was seen in the majority of peripheral zone benign prostatic glands (92.0%) but only a minority of transitional zone benign prostatic glands (18.0%). Basal cells of the transitional zone showed weak or absent CK 34betaE12 staining in 65.9% of glands while maintaining p63. All glands with high-grade prostatic intraepithelial neoplasia (HGPIN) contained the triangular basal cells. In addition, basal cell clusters were identified in 8.7% of peripheral zone glands and 5.2% of HGPIN glands.

CONCLUSIONS

Our results indicate that the basal cell morphology and the basal cell immunophenotype have a zonal variation. The finding of a unique morphology of basal cells and the presence of basal cell clusters in the peripheral zone suggests that the peripheral zone might be the stem/progenitor cell-rich area in the human prostates.

Focal degeneration of basal cells and the resultant auto-immunoreactions: a novel mechanism for prostate tumor progression and invasion

The development of human prostate cancer is believed to be a multistep process, progressing sequentially from normal, to hyperplasia, to prostatic intraepithelial neoplasia (PIN), and to invasive and metastatic lesions. High grade PIN has been generally considered as the direct precursor of invasive lesions, and the progression of PIN is believed to be triggered primarily, if not solely, by the overproduction of proteolytic enzymes predominately by cancer cells, which result in the degradation of the basement membrane. These theories, however, are hard to reconcile with two main facts: (1) only about 30% untreated PIN progress to invasive stage, while none of the current approaches could accurately identify the specific PIN or individuals at greater risk for progression, and (2) results from recent world-wide clinical trials with a wide variety of proteolytic enzyme inhibitors have been very disappointing, casting doubt on the validity of the proteolytic enzyme theory. Since over 90% of prostate cancer-related deaths result from invasion-related illness and the incidence of PIN could be up to 16.5-25% in routine or ultrasound guided prostate biopsy, there is an urgent need to uncover the intrinsic mechanism of prostate tumor invasion. Promoted by the facts that the basal cell population is the source of several tumor suppressors and the absence of the basal cell layer is the most distinct feature of invasive lesions, our recent studies have intended to identify the early alterations of basal cell layers and their impact on tumor invasion using multidisciplinary approaches. Our studies revealed that a subset of pre-invasive tumors contained focal disruptions (the absence of basal cells resulting in a gap greater than the combined size of at least three epithelial cells) in surrounding basal cell layers. Compared to their non-disrupted counterparts, focally disrupted basal cell layers had several unique features: (1) significantly lower proliferation; (2) significantly lower p63 expression; (3) significantly higher apoptosis; and (4) significantly higher leukocyte infiltration and stromal reactions. Compared to their counterparts distant from focal disruptions or overlying non-disrupted basal cell layers, epithelial cells overlying focal basal cell layer disruptions showed the following unique features: (1) significantly higher proliferation; (2) significantly higher expression of cell cycle control-, cell growth-, and stem cell-related genes; and (3) physical continuity with adjacent invasive lesions. Together, these findings suggest that focal basal cell layer disruptions could substantially impact the molecular profile and biological presentations of the overlying epithelial cells. Based on these and other findings, we have proposed that prostate tumor invasion is triggered by a localized degeneration of aged or injured basal cells and the resultant auto-immunoreactions. Our hypothesized steps for prostate tumor invasion include the following: (1) due to inherited or environmental factors, some patients contained cell cycle control- and renewal-related defects in the basal cell population that cause elevated basal cell degenerations; (2) the degradation products of degenerated basal cells or diffusible molecules of the overlying epithelial cells attract leukocyte infiltration; (3) leukocytes discharge their digestive enzymes upon the direct physical contact, resulting in a focal disruption in the basal cell layer, which leads to several focal alterations: (a) a focal loss of tumor suppressors and paracrine inhibitory function; (b) a focal increase of the permeability for growth-required nutrients and oxygen; (c) a focal increase of growth factors; (d) direct physical contact between epithelial and stromal cells; and (e) the exposure of the overlying epithelial cells directly to the stromal tissue fluid. These alterations individually or collectively stimulate or favor a clonal proliferation and stromal invasion of tumor progenitor or stem cells. Our hypothesis differs from the traditional theories in several aspects, including the triggering factor for the initiation of tumor invasion, the stage of tumor invasion, the cellular origin of invasive lesions, the significance of immunoreactive and stromal cells, and the potential approaches for early detection, treatment, and prevention of invasion. Our hypothesis represents a novel in vivo model as to the cellular mechanism leading to prostate tumor invasion. If confirmed, it could lead to a new direction to search for more effective approaches to combat prostate cancer. It could also have an immediate impact on patient care through improved pathologic evaluation of prostate tumor biopsies. More importantly, our hypothesis might be applicable, and significantly impact the detection, treatment, and prevention of other epithelium-derived tumors.

Focal degeneration of aged or injured myoepithelial cells and the resultant auto-immunoreactions are trigger factors for breast tumor invasion

The development of breast cancer is believed to be a multi-step process, sequentially progressing from normal to hyperplastic, to in situ, and to invasive stages. The progression from the in situ to invasive stage is believed to be triggered primarily, if not solely, by the overproduction of proteolytic enzymes by cancer cells, which cause degradation of the basement membrane. This theory is consistent with data derived from studies with cell cultures or animal models, while results from recent worldwide clinical trials with a variety of proteolytic enzyme inhibitors have been very disappointing, casting doubt on the validity of the enzyme theory. Based on our recent studies, we propose that breast tumor invasion is triggered by the following mechanisms and events: (1) the predisposition of genetic abnormalities in ME cell replenishment-related genes or other insults results in elevated focal degeneration of ME cells in some individuals; (2) the degradation products of ME cells or diffusible molecules of epithelial cells attract infiltration of immunoreactive cells (IRC) into the affected sites; (3) the direct physical contact between IRC and degenerated ME cells results in the discharge of digestive enzymes from IRC, causing focal disruptions in the ME cell layer; (4) focal disruptions in a given ME cell layer result in a localized loss of tumor suppressors and paracrine inhibitory function, a focal increase of permeability for oxygen, nutrients, and growth factors, and a localized increase of leukocyte infiltration, which facilitate the monoclonal proliferation of tumor progenitors, forming a biologically more aggressive cell cluster overlying the disrupted ME cell layer; (5) the direct physical contact between the newly formed cell cluster and stromal cells stimulates the production of tenascin and other invasion-associated molecules that facilitate tissue remodeling, angiogenesis, and epithelial-mesenchymal transition, providing a favorable micro-environment for proliferation and invasion. Our hypothesis differs from the enzyme theory in the stage of tumor invasion, the cellular origin of invasive lesions, the significance of IRC and stromal cells, and the potential approaches for treatment and prevention. If confirmed, our hypothesis could facilitate the early detection of specific individuals at increased risk to develop invasive breast cancer. More importantly, our hypothesis may facilitate development of novel approaches, including stimulating ME cell growth, neutralizing ME cell degradation products, manipulating the types and extent of IRC infiltration, and controlling the extent of stromal reactions, to combat tumor invasion.