Expression of aquaporins and PAX-2 compared to CD10 and cytokeratin 7 in renal neoplasms: a tissue microarray study

Renal cell cancer without a renal primary

Renal cell carcinoma has been increasing in incidence over the past two decades. Men are affected more than women and metastatic disease at presentation occurs in up to one third of patients. Metastasis can occur to virtually any organ, and involvement of multiple organs is not uncommon. To date, no reports have been found of metastatic disease without a renal primary. We present a case of renal cell cancer initially presenting as a subcutaneous mass with subsequent pancreatic and parotid gland metastases in absence of a primary renal source.

Decomposition and model selection for large contingency tables

Large contingency tables summarizing categorical variables arise in many areas. One example is in biology, where large numbers of biomarkers are cross-tabulated according to their discrete expression level. Interactions of the variables are of great interest and are generally studied with log-linear models. The structure of a log-linear model can be visually represented by a graph from which the conditional independence structure can then be easily read off. However, since the number of parameters in a saturated model grows exponentially in the number of variables, this generally comes with a heavy computational burden. Even if we restrict ourselves to models of lower-order interactions or other sparse structures, we are faced with the problem of a large number of cells which play the role of sample size. This is in sharp contrast to high-dimensional regression or classification procedures because, in addition to a high-dimensional parameter, we also have to deal with the analogue of a huge sample size. Furthermore, high-dimensional tables naturally feature a large number of sampling zeros which often leads to the nonexistence of the maximum likelihood estimate. We therefore present a decomposition approach, where we first divide the problem into several lower-dimensional problems and then combine these to form a global solution. Our methodology is computationally feasible for log-linear interaction models with many categorical variables each or some of them having many levels. We demonstrate the proposed method on simulated data and apply it to a bio-medical problem in cancer research.

The sonic hedgehog signaling pathway is reactivated in human renal cell carcinoma and plays orchestral role in tumor growth

Background

Human clear cell renal cell carcinoma (CRCC) remains resistant to therapies. Recent advances in Hypoxia Inducible Factors (HIF) molecular network led to targeted therapies, but unfortunately with only limited clinical significance. Elucidating the molecular processes involved in kidney tumorigenesis and resistance is central to the development of improved therapies, not only for kidney cancer but for many, if not all, cancer types. The oncogenic PI3K/Akt, NF-kB and MAPK pathways are critical for tumorigenesis. The sonic hedgehog (SHH) signaling pathway is crucial to normal development.

Results

By quantitative RT-PCR and immunoblot, we report that the SHH signaling pathway is constitutively reactivated in tumors independently of the von Hippel-Lindau (VHL) tumor suppressor gene expression which is inactivated in the majority of CRCC. The inhibition of the SHH signaling pathway by the specific inhibitor cyclopamine abolished CRCC cell growth as assessed by cell counting, BrdU incorporation studies, fluorescence-activated cell sorting and β-galactosidase staining. Importantly, inhibition of the SHH pathway induced tumor regression in nude mice through inhibition of cell proliferation and neo-vascularization, and induction of apoptosis but not senescence assessed by in vivo studies, immunoblot and immunohistochemistry. Gli1, cyclin D1, Pax2, Lim1, VEGF, and TGF-β were exclusively expressed in tumors and were shown to be regulated by SHH, as evidenced by immunoblot after SHH inhibition. Using specific inhibitors and immunoblot, the activation of the oncogenic PI3K/Akt, NF-kB and MAPK pathways was decreased by SHH inhibition.

Conclusions

These findings support targeting SHH for the treatment of CRCC and pave the way for innovative and additional investigations in a broad range of cancers.

Expression of PAX8 in normal and neoplastic renal tissues: an immunohistochemical study

Cell-lineage-specific transcription factors are a group of regulatory proteins expressed in embryonic, differentiated, or neoplastic cells of the same lineage and represent a valuable repertoire of tissue-specific markers for the diagnosis of human tumors. Together with PAX2, PAX8 is a nephric-lineage transcription factor and is required for the establishment of renal-lineage cells and the formation of the kidney. In contrast to PAX2, little is known about the expression of PAX8 in adult kidney and renal tumors. In this study, we used immunohistochemistry to investigate the expression of PAX8 in adult human kidney and renal epithelial tumors. We report here that PAX8 was detected in renal epithelial cells in all segments of renal tubules from the proximal tubules to the renal papillae and in the parietal cells of Bowman's capsule in the adult kidney. PAX8 was also present in 98% of clear cell renal cell carcinomas (RCCs), 90% of papillary RCCs, and 95% of oncocytomas, similar to PAX2. In addition, PAX8 was found in 82% of chromophobe RCCs, 71% of sarcomatoid components of RCCs, and 100% (2/2) of renal medullary carcinomas. Overall, PAX8 was detected in 85% of metastatic renal tumors. Interestingly, expression of PAX8 was noted in some urothelial cells in the renal pelvis and ureters and approximately 23% of urothelial carcinomas of the renal pelvis, but not in the urothelium or urothelial carcinomas of the urinary bladder; this probably underlines the different embryonic origins of urothelial cells in the upper and lower urinary tracts. As shown in this study, PAX8 is widely expressed in normal and neoplastic renal tissues. PAX8 may be a useful additional marker for renal epithelial tumors; however, its specificity and sensitivity await further investigation.

Recent developments in the pathology of renal tumors: morphology and molecular characteristics of select entities

CONTEXT

Renal cell carcinoma is a heterogeneous group of tumors with distinct histopathologic features, molecular characteristics, and clinical outcome. These tumors can be sporadic as well as familial or associated with syndromes. The genetic abnormalities underlying these syndromes have been identified and were subsequently found in corresponding sporadic renal tumors.

OBJECTIVE

To review the recent molecular and genetic advancements relating to sporadic and familial renal carcinomas as well as those related to Xp11.2 translocation-associated renal cell carcinoma and renal medullary carcinoma.

DATA SOURCES

Literature review, personal experience, and material from the University of Chicago.

CONCLUSIONS

Molecular genetic diagnostic techniques will continue to introduce new biomarkers that will aid in the differential diagnosis of difficult cases. The identification of specific signaling pathways that are defective in certain renal tumors also makes possible the development of new therapies that selectively target the aberrant activity of the defective proteins.

Identification of an immunogenic HLA-A*0201-binding T-cell epitope of the transcription factor PAX2

PAX2 is a transcription factor and member of the highly conserved family of paired box genes. PAX2 is aberrantly expressed in a variety of solid and hematologic malignancies. PAX2 regulates the transcription factor Wilms tumor gene 1, which is a promising target of cancer immunotherapy. The aim of this study was to apply a modified reverse immunology strategy to identify immunogenic epitopes of PAX2 which could be useful for cancer immunotherapy. Thirteen potential HLA-A*0201 epitopes were predicted by a major histocompatibility complex binding algorithm (SYFPEITHI) and a proteasome cleavage algorithm (PAProC) and screened for recognition by T cells from HLA-A*02-positive cancer patients using intracellular cytokine cytometry. Epitope-specific T cells were generated from CD4CD25 regulatory T-cell-depleted peripheral blood mononuclear cell. Nine of 20 colorectal cancer patients, 1 of 13 renal cell carcinoma patients, and 2 of 17 lymphoma patients had a spontaneous CD8 T-cell response toward at least 1 of 6 PAX2 peptide pools. None of the 20 healthy subjects showed reactivity toward PAX2. PAX2.337-345 (TLPGYPPHV)-specific T cells could repeatedly be generated, which specifically lysed the PAX2 expressing colorectal tumor cell line SW480. In this study, a modified reverse immunology strategy was employed to identify a first immunogenic HLA-A*0201 restricted T-cell epitope and natural ligand of the tumor antigen PAX2. Thus, PAX2 is another embryonic transcription factor, which is of potential interest as immunotherapy target antigen.

Multiclass cancer classification by support vector machines with class-wise optimized genes and probability estimates

We investigate the multiclass classification of cancer microarray samples. In contrast to classification of two cancer types from gene expression data, multiclass classification of more than two cancer types are relatively hard and less studied problem. We used class-wise optimized genes with corresponding one-versus-all support vector machine (OVA-SVM) classifier to maximize the utilization of selected genes. Final prediction was made by using probability scores from all classifiers. We used three different methods of estimating probability from decision value. Among the three probability methods, Platt's approach was more consistent, whereas, isotonic approach performed better for datasets with unequal proportion of samples in different classes. Probability based decision does not only gives true and fair comparison between different one-versus-all (OVA) classifiers but also gives the possibility of using them for any post analysis. Several ensemble experiments, an example of post analysis, of the three probability methods were implemented to study their effect in improving the classification accuracy. We observe that ensemble did help in improving the predictive accuracy of cancer data sets especially involving unbalanced samples. Four-fold external stratified cross-validation experiment was performed on the six multiclass cancer datasets to obtain unbiased estimates of prediction accuracies. Analysis of class-wise frequently selected genes on two cancer datasets demonstrated that the approach was able to select important and relevant genes consistent to literature. This study demonstrates successful implementation of the framework of class-wise feature selection and multiclass classification for prediction of cancer subtypes on six datasets.

CD98hc (SLC3A2), a novel marker in renal cell cancer

BACKGROUND

In a variety of malignant diseases, molecular targeting represents a therapeutic option, whereby, when compared with chemotherapy, fewer side effects are thought to be expected. Especially in renal cell cancer (RCC), tyrosine kinase-inhibitors have been established as useful and highly effective therapy. However, tyrosine kinase-inhibitors currently approved for RCC treatment lack single molecule specificity and bear a variety of side effects of the gastro-intestinal tract, skin, heart and haematopoietic system. Therefore, the identification of novel cell surface markers is sought, which might lead to novel diagnostic and therapeutic strategies in cancer.

MATERIAL AND METHODS

Paraffin-embedded RCCs from a well characterized tissue bank were immunohistochemically quantified for embryonic transmembrane antigen CD98hc (SLC3A2) expression and semi-quantitative analyses were correlated with subtype or grade of differentiation.

RESULTS

We found increased CD98hc expression in different types of malign RCCs, among them clear cell (cc)RCC, papillary (p)RCC and chromophobe (ch)RCC, but lack of expression in the benign renal oncocytoma. Thereby, the extent of CD98hc expression directly complies with grade of malignancy. Furthermore, the more malignant type II pRCC significantly higher expressed CD98hc than the less malignant and more differentiated type I pRCC (type II 83.34%, type I 4.76% CD98hc positive, P < 0.00001; n = 51). The established marker for type I pRCC, Cytokreatin 7, showed 95.24% expression in type I and 26.67% expression in type II pRCC (P < 0.00001, n = 51).

CONCLUSIONS

From these data, we conclude that CD98hc is expressed in RCCs, whereby the extent of expression is likely to correlate directly with grade of malignancy. In pRCCs, CD98hc might represent a novel and reliable marker for type II pRCC.

Pathologic evaluation of unknown primary cancer

The pathologic approach to metastases of unknown primary cancer (UPC) is stepwise and uses the clinical context, morphology, and, where necessary, immunohistochemistry (IHC). This review covers the initial approach to a UPC biopsy; the diagnosis of malignancy and broad tumor typing into carcinoma, melanoma, lymphoma, or sarcoma; and further subtyping of carcinoma into germ cell (broadly included), squamous, neuroendocrine, and solid organ including liver and renal, and adenocarcinomas. Finally, for adenocarcinoma, the prediction of primary tumor site, including lung, pancreas, stomach, colon, ovary, prostate, and breast, is discussed. For each tumor type, the morphologic features are presented alongside established useful IHC markers, with a description of their staining patterns and common diagnostic dilemmas. Optimal tissue handling and IHC interpretation, quality assurance, and limitations also are discussed. The target readership is oncologists, but other clinicians and trainee pathologists also may find the content of use.

PAX-2 in the diagnosis of primary renal tumors: immunohistochemical comparison with renal cell carcinoma marker antigen and kidney-specific cadherin

The diagnosis of renal cell carcinoma (RCC) remains problematic, especially in the context of metastasis or small needle biopsy specimens. The renal cell carcinoma marker (RCCM) and kidney-specific cadherin (KSC) are considered specific markers for RCC but are expressed preferentially in specific subtypes of RCC of lower grades. This study was aimed at evaluating the usefulness of PAX-2 in the diagnosis of renal tumors and comparing it with that of RCCM and KSC. Immunostaining for PAX-2, RCCM, and KSC was performed on consecutive tissue sections of 130 renal tumors. PAX-2 was successfully detected in routine tissue specimens. Although PAX-2 seems to be more sensitive than RCCM and KSC, there is significant staining overlap in relation to histologic subtypes, justifying the use of all 3 markers, which helps detect the vast majority of renal neoplasms. PAX-2 seems to have a significant role in renal neogenesis and may represent a novel therapeutic target.

Benign Mimickers of Prostate Adenocarcinoma on Needle Biopsy and Transurethral Resection

Prostate needle biopsy currently is the gold standard method for the diagnosis, management, and prognosis of prostate cancer. Obtaining an accurate diagnosis is crucial for pursuing proper patient management. This article discusses histologic mimickers of prostate carcinoma highlighting microscopic features that are helpful to reach a correct diagnosis and emphasizing potential diagnostic pitfalls.

Losses of chromosome arms 4q, 8p, 13q and gain of 8q are correlated with increasing chromosomal instability in hepatocellular carcinoma

OBJECTIVE

Chromosomal instability is a key feature in hepatocellular carcinoma (HCC). Array comparative genomic hybridization (aCGH) revealed recurring structural aberrations, whereas fluorescence in situ hybridization (FISH) indicated an increasing number of numerical aberrations in dedifferentiating HCC. Therefore, we examined whether there was a correlation between structural and numerical aberrations of chromosomal instability in HCC.

METHODS AND RESULTS

27 HCC (5 well, 10 moderately, 12 lower differentiated) already cytogenetically characterized by aCGH were analyzed. FISH analysis using probes for chromosomes 1, 3, 7, 8 and 17 revealed 1.46-4.24 signals/nucleus, which correlated with the histological grade (well vs. moderately,p < 0.0003; moderately vs. lower, p < 0.004). The number of chromosomes to each other was stable with exceptions only seen for chromosome 8. Loss of 4q and 13q, respectively, were correlated with the number of aberrations detected by aCGH (p < 0.001, p < 0.005; Mann-Whitney test). Loss of 4q and gain of 8q were correlated with an increasing number of numerical aberrations detected by FISH (p < 0.020, p < 0.031). Loss of 8p was correlated with the number of structural imbalances seen in aCGH (p < 0.048), but not with the number of numerical changes seen in FISH.

CONCLUSION

We found that losses of 4q, 8p and 13q were closely correlated with an increasing number of aberrations detected by aCGH, whereas a loss of 4q and a gain of 8q were also observed in the context of polyploidization, the cytogenetic correlate of morphological dedifferentiation.

Expression of PAX8 in nephrogenic adenoma and clear cell adenocarcinoma of the lower urinary tract: evidence of related histogenesis?

Recent evidence has showed that nephrogenic adenoma is a true "nephrogenic" lesion derived from the proliferation of exfoliated and implanted renal tubular cells in the urinary tract, a process that closely resembles the formation of endometriosis. This new concept has led to the identification of renal transcription factor PAX2 as a diagnostic marker for nephrogenic adenoma. PAX8 is another transcription factor structurally and functionally related to PAX2. Both are cell lineage restricted transcription factors expressed in normal and neoplastic tissues of related origin, including renal tubular cells in both fetal and adult kidneys. In this study, we investigated the expression of PAX8 in nephrogenic adenoma and its mimics. We report here that PAX8 was detected in all nephrogenic adenomas (N=35) and clear cell adenocarcinoma of the lower urinary tract (N=7), but not in prostate adenocarcinoma (N=100), adenocarcinoma (N=9), squamous cell carcinoma (N=5), or urothelial carcinoma (N=48) of the urinary bladder and its variants. PAX8 was neither detected in normal urothelium of the urinary bladder nor in prostate glands and stroma. PAX2 was also detected in 2 of the 7 clear cell adenocarcinomas of the lower urinary tract. We suggest that PAX8 is an additional marker for identifying nephrogenic adenoma. Expression of PAX8 or PAX2 in both nephrogenic adenoma and clear cell adenocarcinoma of the lower urinary tract may indicate a possible related tissue origin for these 2 lesions; both may be derived from proliferating renal tubular cells in the urinary tract. In addition, detection of PAX8 or PAX2 in clear cell adenocarcinoma of the lower urinary tract is helpful in differentiating it from urothelial carcinoma and its variants and adenocarcinomas of the urinary bladder or of the prostate.

Clear cell renal cell carcinoma with smooth muscle stroma

A recent publication described 5 unusual clear cell renal tumors with prominent smooth muscle stroma that were characterized only by immunostaining. We report 3 additional tumors composed of clear cell renal cell carcinoma intimately admixed with abundant smooth muscle stroma. Epithelial differentiation of the malignant clear cell components and smooth muscle differentiation of the benign spindle cell stroma was confirmed by the immunostaining profiles and by electron microscopy. Fluorescence in situ hybridization analysis of chromosome 3 showed loss of the entire chromosome in 2 cases and loss of 3p in the third case. We therefore interpret these tumors as unique low-grade variants of clear cell renal cell carcinoma that have induced a prolific metaplastic stromal reaction. Extensive tissue sampling and immunostaining are recommended to distinguish cases with an extensive smooth muscle component from morphologically similar but benign lesions including angiomyolipoma, leiomyoma, or mixed epithelial and stromal tumor of the kidney.

The utility of Pax-2 as an immunohistochemical marker for renal cell carcinoma in cytopathology

Pax-2 is a homeogene expressed during kidney development. Its expression in renal cell carcinoma (RCC) has been previously evaluated in histologic samples with a high sensitivity and specificity. Here, we investigated the utility of Pax-2 immunohistochemistry (IHC) for RCC in cytologic material, in comparison with a variety of other neoplasms. Pax-2 IHC was performed on cell block sections of 33 RCCs (14 primary, 19 metastatic) and 35 non-RCC malignancies, including 26 carcinomas, five mesenchymal tumors, one neuroblastoma, two melanomas, and one lymphoma, from fine-needle aspirations and body fluids. The presence or absence of nuclear staining and its intensity and distribution in positive cases were evaluated. Of 33 RCCs, Pax-2 was positive in 20 (61%) and negative in 13 (39%). All staining was nuclear, with an admixture of weakly or strongly staining nuclei. Only an endometrial adenocarcinoma was positive in the non-RCC group. The sensitivity and specificity of Pax-2 IHC for RCC were 61 and 97%, respectively. Pax-2 is a moderately sensitive and highly specific marker for RCC in cytologic material, with a lower sensitivity compared with tissue sections, likely due to a patchy expression pattern, and should be included in the immunohistochemical work-up of malignancies.

Immunohistochemical markers to distinguish between hemangioblastoma and metastatic clear-cell renal cell carcinoma in the brain: utility of aquaporin1 combined with cytokeratin AE1/AE3 immunostaining

Distinguishing hemangioblastomas from metastatic clear-cell renal cell carcinomas (CCRCCs) in the brain is a diagnostic challenge owing to similar clinical and morphologic presentations. Inhibin-alpha and aquaporin1 were shown as positive markers of hemangioblastoma, but are not totally reliable distinguishing hemangioblastoma from metastatic CCRCC. This study shows that the diagnosis can be achieved using a combination of markers. To identify the panel of markers useful for this differential, 67 hemangioblastomas and 34 metastatic CCRCCs were analyzed using a panel of antibodies including aquaporin1, inhibin-alpha, D2-40, cytokeratin AE1/AE3, epithelial membrane antigen, and CD10. The study confirms the usefulness of aquaporin1 (97% sensitivity, 83% specificity) and inhibin-alpha (88% sensitivity, 79% specificity) as positive markers of hemangioblastoma and shows that aquaporin1 is a superior positive marker versus inhibin-alpha for the differential. Positivity of tumor cells with cytokeratin AE1/AE3 is the signature of a metastatic CCRCC (100% specificity, 88% sensitivity) and CD10 expression as well (100% specificity, 79% sensitivity). The combined use of aquaporin1 and AE1/AE3 yields a high degree of sensitivity and specificity to differentiate between hemangioblastoma and metastatic CCRCC. All tumors but one aquaporin1 positive and cytokeratin AE1/AE3 negative (65/66) correspond to hemangioblastomas (97% sensitivity, 97% specificity, 98.5% diagnostic positive predictive value). Tumors with the opposite profile, aquaporin1 negative, and cytokeratin AE1/AE3 positive, (25/25), correspond to metastatic CCRCC (74% sensitivity, 100% specificity, 100% diagnostic positive predictive value). In summary, aquaporin1 is the most sensitive positive marker of hemangioblastoma. Despite its moderate specificity, when used in combination with epithelial marker AE1/AE3, it allowed to reliably distinguish hemangioblastoma from metastatic CCRCC.

In vivo validation of PAX2 as a target for renal cancer therapy

PAX genes are frequently overexpressed in human cancer tissue and appear to contribute to the tumor phenotype, suggesting that they may be potential targets for cancer therapy. In particular, aberrant PAX2 expression has been reported in a high proportion of primary tumors, including the majority of renal cell carcinomas (RCC). We recently demonstrated that PAX2 suppresses cisplatin-induced apoptosis in cultured RCC cells. We hypothesized that silencing of PAX2 expression might partially overcome the notorious resistance of renal cell carcinomas to chemotherapy in vivo. In this report, we show that a PAX2 shRNA successfully knocks down PAX2 mRNA and protein levels in an RCC cell line (ACHN). ACHN cells stably transfected with shRNAs targeted against the PAX2 homeodomain are 3-6-fold more susceptible to cisplatin-induced caspase-3 activation than control ACHN cells line. Furthermore, growth of subcutaneous ACHN/shPAX2 xenografts in nude mice is significantly more responsive to cisplatin therapy than control ACHN cell tumors. Our observations validate PAX2 as a potential therapeutic gene target in renal cancer and suggest that adjunctive PAX2 knockdown may enhance the efficacy of other chemotherapeutic agents.

AQP1 expression analysis in human diseases: implications for proteomic characterization

Aquaporin (AQP)1 belongs to a ubiquitous family of water channel proteins characterized by sequence similarity and the presence of two NPA (Asp-Pro-Ala) motifs existing in almost all organs and tissues. Currently, 13 human AQPs are known and they are divided into two subgroups according to their ability to transport only water molecules, such as AQP1, or also glycerol and other small solutes. The genomic, structural and functional aspects of AQP1 are briefly described. An in-depth discussion is devoted to proteomic approaches that are useful for identifying and characterizing AQP1, mainly through electrophoretic techniques combined with different extraction procedures followed by mass spectrometry analysis. Moreover, the relevance of AQP1 in human diseases is also explained. Its role in human tumors and, in particular, those of the kidney (e.g., clear cell renal carcinoma) is discussed.

Comparison and identification of estrogen-receptor related gene expression profiles in breast cancer of different ethnic origins

The interactions between genetic variants in estrogen receptor (ER) have been identified to be associated with an increased risk of breast cancer. Available evidence indicates that genetic variance within a population plays a crucial role in the occurrence of breast cancer. Thus, the comparison and identification of ER-related gene expression profiles in breast cancer of different ethnic origins could be useful for the development of genetic variant cancer therapy. In this study, we performed microarray experiment to measure the gene expression profiles of 59 Taiwanese breast cancer patients; and through comparative bioinformatics analysis against published U.K. datasets, we revealed estrogen-receptor (ER) related gene expression between Taiwanese and British patients. In addition, SNP databases and statistical analysis were used to elucidate the SNPs associated with ER status. Our microarray results indicate that the expression pattern of the 65 genes in ER+ patients was dissimilar from that of the ER- patients. Seventeen mutually exclusive genes in ER-related breast cancer of the two populations with more than one statistically significant SNP in genotype and allele frequency were identified. These 17 genes and their related SNPs may be important in population-specific ER regulation of breast cancer. This study provides a global and feasible approach to study population-unique SNPs in breast cancer of different ethnic origins.

Nephrogenic adenoma identified on urine cytology using PAX-2 immunostaining

Urine cytology is a sensitive and specific method in detecting urothelial carcinoma of the urinary bladder, particularly the high-grade ones. However, the cytologic features of nonneoplastic lesions of the lower urinary tract, including nephrogenic adenoma, are nonspecific and may cause false positive diagnosis. Recent evidence has demonstrated that nephrogenic adenoma is a true "nephrogenic" lesion derived from the exfoliated and implanted renal tubular cells in the urinary tract. This has promoted the use of immunostaining of renal transcription factor PAX2 in tissue biopsies to differentiate nephrogenic adenoma from the common malignant tumors of the lower urinary tract. We report here that PAX2 immunostaining can also be used in urine cytology specimen to identify nephrogenic adenoma. Combination of PAX2 immunostaining and cytologic analysis may increase the accuracy in identifying this benign lesion in urine cytology specimen and therefore reduce unnecessary repeat cystoscopy and biopsy procedures. This may be a cost effective follow- up method for patients with an established diagnosis of nephrogenic adenoma.

Application of Immunohistochemistry to the Genitourinary System (Prostate, Urinary Bladder, Testis, and Kidney)

Context.—The variety of morphologic patterns of different entities of the genitourinary tract can present a diagnostic dilemma for the pathologist. This is especially true in cases of mimics of cancer, a cancer of unknown primary, or poorly differentiated tumors, in which it is hard to assign histogenesis needed to plan the correct therapy for the patient. Immunohistochemistry offers a better capacity than hematoxylin-eosin staining alone to differentiate human tissue types. Also, in the past decades, several techniques had been developed to differentiate between benign and malignant processes with morphologic overlap. By using immunohistochemistry in selected cases, the rate of false-negative and false-positive diagnoses can be reduced, and some patients are afforded the opportunity to get more specific or effective therapy as a result.

Objective.—For each subgroup of genitourinary system tumors, common diagnostic problems are reviewed, and immunohistochemical markers useful in addressing these problems are discussed, along with expected patterns of immunoreactivity.

Data Sources.—The pertinent literature, with focus on immunohistochemical staining of tumors of the genitourinary tract.

Conclusions.—The addition of immunohistochemistry to the diagnostic armamentarium for genitourinary pathologic diagnosis has increased the sensitivity and specificity of diagnoses and aided in the selection of optional therapeutic regimens in selected cases.

Best practices in diagnostic immunohistochemistry: hepatocellular carcinoma versus metastatic neoplasms

CONTEXT

Immunohistochemistry plays a crucial role in the diagnosis of hepatocellular carcinoma and in its distinction from other primary and metastatic neoplasms. Because limited tissue is available with fine-needle and core biopsies, appropriate selection of antibodies is imperative.

OBJECTIVE

To review the antibodies used for the diagnosis of hepatocellular carcinoma and to outline an immunohistochemical approach in commonly encountered clinical situations.

DATA SOURCES

Our experience and review of research articles published in the English literature between 1987 and 2006.

CONCLUSIONS

Hep Par 1 and polyclonal carcinoembryonic antigen are the most reliable markers for hepatocellular differentiation, but they have low sensitivity for poorly differentiated cases. Immunohistochemistry for glypican-3 shows promise for the diagnosis of poorly differentiated hepatocellular carcinoma and for its distinction from benign processes such as hepatic adenoma. Further studies with a large number of cases are required before it can be widely used. The combination of Hep Par 1 and MOC-31 will allow for the diagnosis of hepatocellular carcinoma in most cases and will guide the selection of immunohistochemical markers for further workup.

Key clinical issues in renal cancer: a challenge for proteomics

Renal cancer has many clinical challenges which proteomics is ideally placed to address. The issues cover all aspects of the disease including diagnosis, prognosis, treatment selection and monitoring to detect metastatic disease. In all cases novel biomarkers would considerably help in clinical management and with the relative resistance to conventional chemotherapy and radiotherapy, a better understanding of the underlying pathogenesis may contribute to the much needed development of novel therapeutic targets and the better use of promising new anti-angiogenic treatments. This review briefly highlights some of the clinical issues and describes proteomics-based approaches generally, before focussing on reviewing the proteomic studies to date in this area.

Cholangiocyte biology

PURPOSE OF REVIEW

Cholangiocytes are increasingly recognized as biologically important epithelia because of the diverse array of cellular processes in which they participate. Collectively, these processes define normal function and, when disturbed, account for abnormalities that cause disease. In addition, the cholangiocyte is the target cell of diverse pathologic processes (i.e. the cholangiopathies). Advances in animal models, imaging and gene silencing have further defined the roles that cholangiocytes play in signaling, transport of water, ions and solutes, and alterations that result in cholestasis. The pace of advances in technology justifies a yearly summary to identify trends, and apprise the readership of the most significant developments in cholangiocyte biology.

RECENT FINDINGS

Recent progress includes insights into the molecular mechanisms of bile secretion, the development of new experimental models, technologies, hypotheses and therapies relevant to disease. Major advances have also included the identification of novel roles for receptors and a better understanding of mechanistic pathways and biologic processes.

SUMMARY

This compendium of current activities in cholangiocyte biology may promote collegial sharing and exchange of novel concepts, ideas, reagents and probes, thereby promoting positive advances in the field.

Proteomic knowledge of human aquaporins

Aquaporins (AQPs) are an ubiquitous family of proteins characterized by sequence similarity and the presence of two NPA (Asp-Pro-Ala) motifs. At present, 13 human AQPs are known and they are divided into two subgroups according to their ability to transport only water molecules (AQP0, AQP1, AQP2, AQP4, AQP5, AQP6, and AQP8), or also glycerol and other small solutes (AQP3, AQP7, AQP9, AQP10, AQP12). The genomic, structural, and functional aspects of this family are briefly described. In particular, proteomic approaches to identify and characterize the most studied AQPs, mainly through SDS-PAGE followed by MS analysis, are discussed. Moreover, the clinical importance of the best studied aquaporin (AQP1) in human diseases is also provided.

Expression of aquaporin 3 (AQP3) in normal and neoplastic lung tissues

Aquaporin 3 (AQP3) acts as the membrane channel of water and other small solutes and plays a major role in fluid homeostasis. To investigate the expression of AQP3 in normal and neoplastic lung tissues, we studied a series of 149 lung carcinoma tissues and 2 cell lines by immunohistochemistry, Western blotting, and reverse transcriptase-polymerase chain reaction. In normal lung tissues, immunohistochemical expression of AQP3 was demonstrated in bronchial basal cells, alveolar type II cells, bronchiolar epithelial cells, and secretory cells of submucosal glands. In lung carcinomas, AQP3 expression was observed in 59 (70.2%) of 84 adenocarcinomas. Squamous cell carcinoma and large cell carcinoma had rather low positive ratios (35.8% and 13.4%, respectively). No AQP3 expression was demonstrated in small cell carcinoma, pleomorphic carcinoma, or metastatic colon adenocarcinoma. In adenocarcinomas, AQP3 was detected in all tumors of bronchioloalveolar subtype. Papillary subtype also showed a higher positive ratio of AQP3 compared with that in acinar and solid with mucin subtypes. In addition, AQP3 expression was related to tumor differentiation and clinical stage in adenocarcinomas. Western blotting and reverse transcriptase-polymerase chain reaction analyses confirmed the expression of AQP3 protein and messenger RNA in cell lines and tissues of lung adenocarcinoma. We conclude that AQP3 is widely expressed in the normal respiratory tract and can play an important role in the maintenance of water homeostasis. In addition, lung carcinomas, especially adenocarcinomas, can produce AQP3, possibly in connection with their functional and/or biological nature, although the detailed mechanism of AQP3 expression in lung carcinomas remains to be clarified.

Cytohistopathologic hybrid renal cell carcinoma with papillary and clear cell features

Clear cell (CRCC) and papillary (PRCC) renal cell carcinomas (RCC) are the two most frequent subtypes of RCC. In this study, we studied RCC which displayed a hybrid morphology with areas of PRCC and CRCC or which contained papillary structures with clear cell changes (CCC). Consecutive cases of RCC collected over a 12-year period were reviewed to identify RCC with papillary structures and a possible admixture between CRCC and non-oncocytic PRCC. Special stains for glycogen and immunostaining for cytokeratin 7 were applied to sections containing both areas of classical PRCC and PRCC with CCC. Of the total of 541 RCC retrieved, there were 68 non-oncocytic RCC having papillary structures that could be grouped into: (a) group 1 (15 cases), CRCC with areas of papillary formation; (b) group 2a (9 cases), PRCC with extensive CCC with areas of foamy epithelial cells or macrophages; (c) group 2b (18 cases), RCC with areas of classical PRCC with focal CCC; and (d) group 3 (26 cases), RCC with features of groups 2a and 2b and containing areas of classical CRCC. There was a high rate (12/68) of sarcomatous transformation in the study cases. Groups 2 and 3 were associated with a higher rate of vascular invasion, distant metastasis, and mortality than classical PRCC and a higher rate of lymph node metastasis than CRCC. Our study identifies two groups of RCC (referred to as groups 2 and 3) that exhibit characteristic cytohistopathologic hybrid features that set them apart from classical RCC. This type of hybrid tumor seems to be associated with a more aggressive biologic behavior, and its recognition may facilitate the classification of RCC with ambiguous morphology.

Renal adenocarcinoma in a ferret

A spontaneous case of renal tumor was observed in a 7-year-old ovariectomized female pet ferret (Mustela putorius furo). Clinical signs included exhaustion, emaciation, anorexia, and stooping position. At necropsy, a solid and cystic mass replaced the left kidney and adrenal gland. The tumor was composed of pleomorphic epithelial cells with a large number of giant cells. Metastases were recognized in the lung, liver, greater omentum, right renal pelvis, and systemic lymph nodes. Immunohistochemical stains revealed that the tumor cells were positive for CD10, cytokeratin (CAM 5.2), and Ki-67 (MIB-1). On the basis of morphologic and immunohistochemical features, the tumor was diagnosed as a pleomorphic renal adenocarcinoma. This type of neoplasm is very rare in all species and has never been reported in a ferret.

Increased migration and metastatic potential of tumor cells expressing aquaporin water channels

Aquaporin (AQP) water channels are expressed in high-grade tumor cells of different tissue origins. Based on the involvement of AQPs in angiogenesis and cell migration, we tested whether AQP expression in tumor cells might enhance their migration and metastatic potential. Transfection of B16F10 and 4T1 tumor cells with AQP1 did not affect their appearance, size, growth, or substrate adherence but increased their plasma membrane osmotic water permeability by 5- to 10-fold. In vitro analysis of cell migration by transwell assay, wound healing and video microscopy showed a 2- to 3-fold accelerated migration of the AQP1-expressing tumor cells compared to control cells. In mice, AQP1 expression increased tumor cell extravasation by >1.5-fold as quantified by counting tumor cells in lung at 6 h after tail vein injection of a mixture of fluorescently tagged AQP1-expressing and control tumor cells. AQP1 expression also increased by 3-fold the number of lung metastases 14 days after tail vein injection of tumor cells, with alveolar wall infiltration seen with AQP1-expressing tumor cells. Our results provide evidence for AQP-facilitated tumor cell migration and spread, suggesting a novel function for AQP expression in high-grade tumors. AQP inhibition may thus reduce the metastatic potential of some tumors.

Tissue microarrays: bridging the gap between research and the clinic

Tissue microarrays are a high-throughput method for the investigation of biomarkers in multiple tissue specimens at once. This technique allows for the analysis of up to 500 tissue samples in a single experiment using immunohistochemistry and in situ hybridization. Recently, cell lines and xenografts have been reduced to a tissue microarray format and are being applied to preclinical drug development. In clinical research, tissue microarrays are applied at multiple levels: comprehensive analysis of samples in the context of a clinical trial or across a population. Tissue microarrays play a central role in translational research, facilitating the discovery of molecules that have potential roles in the diagnosis, prognosis and prediction of response to therapy.

PAX2 inactivation enhances cisplatin-induced apoptosis in renal carcinoma cells

Renal cell carcinoma (RCC) is the most common kidney malignancy and has a poor prognosis owing to its resistance to chemotherapy. RCC cells overexpress the transcription factor, PAX2, normally expressed in fetal kidney but downregulated at birth. Since Pax2 suppresses apoptosis during renal development, we reasoned that PAX2 may confer resistance to cisplatin-induced apoptosis in RCC. Here, we show that PAX2 confers resistance to cisplatin-induced apoptosis in normal kidney cells and fetal kidney explants. Human embryonic kidney 293 cells transfected with a PAX2 expression vector and exposed to cisplatin (40 microM) exhibited 45 +/- 15% as much caspase-3 cleavage compared to control cells. Conversely, murine collecting duct cells stably transfected with PAX2 antisense cDNA had twofold increase in cisplatin-induced apoptosis. Murine fetal (embryonic day 15) kidney explants from PAX2(1Neu)+/- mice exposed to cisplatin (25 microM x 24 h) had 50% increased apoptosis (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling staining). We then show that RCC cells (CAKI-1 (human, Caucasian, kidney, carcinoma) and ACHN (human, Caucasian, kidney, adenocarcinoma)) express PAX2 protein. PAX2-small interfering RNA (100 nM) reduces endogenous PAX2 protein (10% of baseline) and induces apoptosis (Annexin-V staining). Pax2 knockdown sensitized RCC cells to cisplatin-induced apoptosis, killing 50-60% of cisplatin-resistant ACHN and CAKI-1 cells. These findings suggest that PAX2 confers resistance to cisplatin-induced apoptosis in non-transformed kidney cells and fetal kidney explants. Similarly, Pax2 overexpression in RCC cells contributes to cisplatin resistance. Conceivably, a therapeutic strategy that inactivates Pax2 in vivo might enhance the efficacy of conventional cytotoxic drugs against RCC.

An immunohistochemical approach to the differential diagnosis of renal tumors

Renal neoplasms comprise several distinct clinicopathologic entities with potential prognostic and the rapeutic differences. Although careful morphologic examination using sections stained with hematoxylin and eosin will allow for the correct diagnosis in the majority of cases, there is sufficient overlap between several entities such that ancillary techniques may be necessary to arrive at the correct diagnosis. In routine diagnostic surgical pathology practice of renal tumors, immunohistochemistry is the foremost ancillary technique. Using an approach based on common histologic patterns (tumors with clear cytoplasm, granular cytoplasm, tubulopapillary architecture, spindle cell morphology, small round-cell morphology, and infiltrating poorly differentiated carcinoma), we will discuss the utility of immunohistochemistry in the differential diagnosis of renal neoplasms. In recent years, needle biopsies from renal masses are being increasingly performed. In these small biopsies, the entire range of cytoarchitectural features that are generally necessary to make a diagnosis may not be fully appreciated. Immunohistochemistry may be helpful in this setting to narrow the differential diagnosis or to arrive at a definitive diagnosis. Finally, the use of immunohistochemistry for the confirmation of metastatic renal cell carcinoma presenting at distant sites will be discussed. Panels of immunohistochemical stains are proposed for different settings, including renal cell carcinoma (RCC) marker, CD10, and vimentin to suggest renal origin of a metastatic tumor, and markers to aid in subclassification of RCC, including parvalbumin and c-kit for chromophobe RCC, and cytokeratin 7 and alpha-methyl-acyl-CoA racemase for papillary RCC.

Diagnostic significance of aquaporin-1 in liver tumors

The diagnostic utility of aquaporin (AQP)-1 in liver tumors was tested and compared with other well-established markers. In 30 cholangiocarcinomas (CCs), 20 hepatocellular carcinomas (HCCs), and 10 metastatic colorectal carcinomas (MCCs) of the liver, expression of AQP-1, CD10, cytokeratin (CK) 7, CK20, and polyclonal carcinoembryonic antigen (pCEA) was tested. In addition, staining patterns of CD10 and pCEA were analyzed. To compare the selectivity of AQP-1 and CK7 as possible markers for differentiated cholangiocytes, liver biopsies of cholestatic disease were also analyzed. Aquaporin-1 expression was found in 93% of all CCs compared with 0% of HCC (P < .000001) and with 30% of MCC (P < .01). CD10 was positive in 16.7% of CC compared with 40% of HCC (P < .04) and to 20% of MCC (not significant). Cytokeratin 7 was positive in 90% of CC compared with 10% of HCC (P < .00001) and with 20% of MCC (P < .0001). Cytokeratin 20 was positive in 90% of MCC compared with 16.7% of CC (P < .0001) and with 20% of HCC (P < .00001). Canalicular staining patterns of CD10 and pCEA were observed in HCC (100% and 89.5%, respectively) but typically not in CC (0% and 6.7%, respectively) and never in MCC. In cholestatic disease, AQP-1 was expressed in differentiated epithelial cells of the bile ducts, whereas CK7-positive hepatocytes of Rappaport zone 1 did not show any AQP-1 reactivity. Therefore, AQP-1 seems to be a highly selective marker for differentiated cholangiocytes and can be very helpful in the differential diagnosis of liver tumors.