Tissue microarrays and their relevance to the urologist

The role of tissue microarray in the era of target-based agents

Tissue microarray (TMA) technologies have been developed over the last years, mainly to identify biomarkers useful for the correct identification and characterization of tumors. Moreover, TMA has been implemented in retrospective studies in order to identify predictive biomarkers of response to a given therapy and/or to find potential new targets for biological therapy. We analyzed the fields of application of TMA technology and the design of TMA varying according to the objectives to be studied. In this article, the reader will learn how to design TMAs in order to cover the objectives of clinical trials based upon the use of target-based agents. The main limits and advantages of TMA and the results achieved in cancer diagnosis will be also described. Tissue microarray technology should be systematically applied to define critical markers, in retrospective studies and in the screening of most human tumors in order to find new possible molecular targets and to molecularly define the diagnosis of the neoplastic diseases. TMAs have substantially improved the field of translational studies, even in the design and follow-up of studies based upon the use of target-based agents in cancer therapy.

Expression of multidrug resistance-related protein (MRP-1), lung resistance-related protein (LRP) and topoisomerase-II (TOPO-II) in Wilms' tumor: immunohistochemical study using TMA methodology

AIMS

MRP-1, LRP and TOPO-II are all associated with protection of the cells from the adverse effects of various chemotherapeutics. The aim of this study was to measure the expression of these proteins in Wilms' tumor (WT).

MATERIALS AND METHODS

TMA block was constructed from 14 samples of WT's and from xenografts derived from them. Sections of the TMA were used for immunostaining against MRP-1, LRP and TOPO-IIa.

RESULTS

All normal kidneys expressed MRP-1 but were either weakly or negatively stained for LRP and TOPO-IIa. In WT samples, MRP-1 was universally expressed, exclusively in the tubular component, while there was no expression of LRP and TOPO-IIa showed heterogeneous distribution. The xenografts varied in their MRP-1 and TOPO-IIa expression and exhibited weak/negative staining of LRP.

CONCLUSIONS

This study shows that although all the proteins evaluated, had different expression patterns in the tumor samples, the most prominent changes in expression were found for MRP-1. The exact clinical implications of these changes in expression and their relevance to the resistance of these tumors to chemotherapy requires further investigation. The finding of different expression profiles for the multidrug resistance proteins in the original WT's and their xenografts suggests that the results of animal cancer models may be difficult to interpret.

Tissue microarray based analysis of prognostic markers in invasive bladder cancer: much effort to no avail?

PURPOSE

To evaluate altered protein expression with tissue microarray methodology for 15 different markers with potential prognostic significance in invasive bladder cancer.

MATERIALS AND METHODS

Invasive tumor was sampled with the tissue-arraying instrument in 133 consecutive patients who underwent radical cystectomy, and at least 3, 0.6-mm tissue cores were obtained. With immunohistochemistry, the expressions of TP53, RB1, CDKN1A (p21), MKI67 (Ki67), PTGS2 (Cox-2), CTNNA1 (alpha-catenin), CTNNB1 (beta-catenin), AKT, PTEN, RHOA, RHOC, STAT1, VEGFC, EGFR, and ERBB2 (HER2) were quantified, and correlations were made with tumor grade, pathologic stage, lymph node status, and disease-specific survival.

RESULTS

Decreased immunohistochemical expression of CTNNA1 and of PTEN correlated with higher pathologic tumor stages (P = 0.01 and P = 0.01, respectively), whereas increased AKT1 and ERBB2 correlated with lower pathologic tumor stages (P = 0.01 and P = 0.03, respectively). Increased RHOA expression was more common in grade 3 than in grade 2 tumors (P = 0.016). There were no other correlations among the 15 factors studied and pathologic stage, lymph node status, or tumor grade. No association was found between bladder cancer death and altered marker status for any of the markers studied.

CONCLUSIONS

Currently, there are reasons to have a skeptical attitude toward the value of tissue microarray based immunohistochemistry as a method for evaluating prognostic markers in invasive bladder cancer. In this study, 15 antibodies were tested but were found to be of little clinical value. Whether this negative finding is related to the group of patients or factors studied, or the methodology is unclear.

Differential expression of α-methylacyl-coenzyme A racemase in colorectal carcinoma bears clinical and pathologic significance

alpha-methylacyl-coenzyme A racemase (AMACR) is a recently discovered biomarker that is shown to be overexpressed in some prostatic carcinomas and associated with prostatic cancer progression. Given that AMACR plays an important role in peroxisomal beta-oxidation of branched-chain fatty acids from red meat and dairy products, and that consumption of red meat may increase risk of developing colon cancer as suggested by epidemiological studies, it is plausible to explore the function of AMACR in colorectal carcinoma. A few previous studies have indeed observed overexpression of AMACR in 45% to 69% of the colorectal carcinomas. However, the clinical and pathologic characteristics of such AMACR expressers have not been investigated. In this study, the immunohistochemical expression pattern of AMACR of 163 patients with primary colorectal carcinoma treated primarily with surgical resection was analyzed and correlated with tumor pathologic features (tumor location, histologic type, grade, pathologic stage, lymph node and distant metastasis) and patient outcome (disease-specific survival). The results showed variable positive staining for AMACR in 123 (75%) of 163 tumors, and moderate to strong staining in 63 (39%) of 163. Lack of staining or low-intensity staining appeared to correlate significantly with mucinous histology (P < .001), poor tumor differentiation (P = .021), and presence of lymphovascular invasion (P = .032). Patients whose tumors showed lack of staining or low-intensity staining also had a significantly worse 5-year disease-specific survival (P < .012), as did patients whose tumors had lymphovascular invasion, or were of high American Joint Committee on Cancer (AJCC) stage. On multivariate analysis, AMACR staining and AJCC staging remained independent predictors for patient outcome. Thus, our data suggest that AMACR expression in colorectal carcinoma correlates with certain tumor pathologic characteristics (histologic type, differentiation, and lymphovascular invasion) and patient outcome. Additional confirmatory studies are needed to establish the significance of AMACR as a prognostic marker for colorectal carcinoma. Further investigation on interaction between AMACR and other known colorectal cancer development pathways may provide new insights on colorectal carcinogenesis.

Overexpression of Ets-like protein 1 in human esophageal squamous cell carcinoma

AIM: To study the expression pattern of Ets-like protein 1 (Elk-1) in human esophageal squamous cell carcinoma (ESCC) and to analyze its relationship with clinicopathologic parameters.

METHODS: The expression of Elk-1 in fresh esophageal cancer tissues and their corresponding normal mucosae was detected immunohistochemically (IHC) by means of tissue microarray (TMA). Its correlation with clinical characteristics was evaluated and analyzed by univariate analysis. All statistical analyses were performed by SPSS version 13.0.

RESULTS: Expression level of transcription factor Elk-1 increased in 78.5% (84/107) ESCC tissues compared with their matched normal esophageal epithelium. However, the expression of Elk-1 did not show any obvious correlation with degree of differentiation of esophageal carcinoma (in well-differentiated, moderately-differentiated and poorly-differentiated tumors, the increased expression was 7/8, 60/74, and 19/25, respectively, P > 0.05). Moreover, no obvious correlation was found with lymph node metastasis and depth of invasion.

CONCLUSION: Increased expression of transcription factor Elk-1 may play an important role in esophageal carcinogenesis.