CDX-2 Homeobox Gene Product Expression in Neuroendocrine Tumors

Identification of differentially expressed microRNAs by microarray: a possible role for microRNA genes in pituitary adenomas

MicroRNAs (miRNAs) are small non-coding RNAs that control gene expression by targeting mRNA. It has been demonstrated that miRNA expression is altered in many human cancers, suggesting that they may play a role in human neoplasia. To determine whether miRNA expression is altered in pituitary adenomas, we analyzed the entire miRNAome in 32 pituitary adenomas and in 6 normal pituitary samples by microarray and by Real-Time PCR. Here, we show that 30 miRNAs are differentially expressed between normal pituitary and pituitary adenomas. Moreover, 24 miRNAs were identified as a predictive signature of pituitary adenoma and 29 miRNAs were able to predict pituitary adenoma histotype. miRNA expression could differentiate micro- from macro-adenomas and treated from non-treated patient samples. Several of the identified miRNAs are involved in cell proliferation and apoptosis, suggesting that their deregulated expression may be involved in pituitary tumorigenesis. Predictive miRNAs could be potentially useful diagnostic markers, improving the classification of pituitary adenomas.

Homeobox genes and their functions on development and neoplasm in gastrointestinal tract

AIM

To describe the role of homeobox genes on development and tumorigenesis in gastrointestinal tract.

METHODS AND RESULTS

We searched the MEDLINE database (until March, 2006) with the keywords of homeobox genes, gastrointestinal tract, development, tumorigenesis, carcinogenesis and therapeutic targets. We reviewed the literature on classification of homeobox genes, development of gastrointestinal tract, carcinogenesis of gastrointestinal tract as well as therapeutic targets.

CONCLUSIONS

The functional effects of homeobox family in development and tumorigenesis of gastrointestinal tract are identified. The importance of homeobox genes and a possibility of therapeutic intervention in clinical medicine are discussed.

Expression of CDX2 in benign tissue and adenocarcinoma of the prostate

Numerous studies have claimed that CDX2 is relatively specific and sensitive in establishing a gastrointestinal origin in metastatic tumors of unknown origin. We have recently seen 2 cases of prostatic adenocarcinoma (PCa) on needle biopsies with diffuse strong nuclear staining for CDX2 sent for consultation. One case was a prostatic duct adenocarcinoma in a man with a prostate-specific antigen (PSA) value of 327 ng/mL, and the other was a PCa with a Gleason score (GS) of 4 + 4 = 8 in a man with a PSA value of 15 ng/mL. An adenocarcinoma with GS 3 + 3 = 6 from the contralateral side did not express CDX2. Because documented examples of this phenomenon are rare, we investigated the immunoexpression of CDX2, using tissue microarrays (TMAs). Three slides of TMAs were used to stain 708 tissue samples (0.6 mm in diameter) containing either benign or malignant prostate tissue, as well as control tissues from various anatomical sites including colon. In total, 195 samples of primary PCa with GS of 6 (n = 41), 7 (n = 21), and 8 (n = 8); 195 samples of benign prostate tissue; and 185 samples of metastatic PCa were studied. Of 70 radical prostatectomy specimens examined for PCa in TMAs, 4 (5.7%) were positive for CDX2, showing Gleason score of 6 (n = 3) and Gleason score of 7 (n = 1). Focal moderate positive staining was seen in benign prostate tissue in 7 (11.7%) of 60 radical prostatectomy specimens. None of the metastatic PCa expressed CDX2. CDX2 may uncommonly be focally expressed in benign prostatic glands. Staining in PCa is less common and appears independent of GS and is usually patchy and focal and of lesser intensity than in colonic tissue. However, rarely strong and diffuse staining may be seen. Positive CDX2 staining in high-grade prostate cancer (ductal, cribriform, and solid) may be confused with secondary carcinoma of colonic origin. Routine histopathology, positive PSA immunostaining, and clinical findings can help confirm the correct diagnosis.

Historical, current and future perspectives on gastrointestinal and pancreatic endocrine tumors

Gastrointestinal and pancreatic endocrine tumors are neoplasms of which the pathogenesis is not completely understood and of which the clinical behavior is difficult to predict. Originally, Masson suggested that the cell of origin was an endocrine cell derived from the gastrointestinal epithelium. However, Pearse showed that the endocrine cells throughout the body shared various features, among others the amine precursor uptake and decarboxylation (APUD) capacity, and postulated the neural crest as the common origin for all APUD cells, a hypothesis that received support from the scientific community for many years. Now, biologists start to elucidate the various transcription factors that drive gastrointestinal development, and it has become evident that Masson was presumably right. Transcription factors relevant for development may also operate during tumorigenesis, and their expression may determine tumor biology. With other genetic factors, they may play a role in the pathogenesis of gastrointestinal and pancreatic endocrine tumors, and perhaps, their expression will turn out to be of prognostic or therapeutic value. In this review, current knowledge on the development of endocrine cells, hypotheses on the origin of endocrine tumors, genetic alterations, and prognostic factors are discussed. It is suggested that the increasing understanding of the normal development of gastrointestinal and pancreatic endocrine cells, the accumulating data on genetic alterations in endocrine tumors and the reappraisal of the hypotheses on their pathogenesis formulated in the past may help in elucidating their pathogenesis and in more accurately predicting prognosis.

CDX2 Is a Useful Marker of Intestinal-Type Differentiation: A Tissue Microarray–Based Study of 629 Tumors From Various Sites

Context.—CDX2, a critical nuclear transcription factor for intestinal development, is expressed in intestinal epithelium and adenocarcinomas.

Objectives.—To determine if CDX2 is a useful marker for intestinal-type differentiation and to correlate tumor histology with CDX2 staining in colorectal adenocarcinomas.

Design.—Tissue microarrays from 71 colorectal adenocarcinomas, 31 hepatocellular carcinomas, 47 lung adenocarcinomas, 55 squamous cell carcinomas of the lung, 69 neuroendocrine carcinomas of the lung and 43 of the pancreas, 57 pancreatic adenocarcinomas, and 256 endometrial adenocarcinomas were stained with antibody against CDX2.

Results.—CDX2 staining was positive in 51 (71.8%) of 71 colorectal cancers, including 38 (74.5%) of 51 well- or moderately differentiated tumors and 13 (65.0%) of 20 high-grade tumors. Of the high-grade tumors, 5 (71.4%) of 7 mucinous, 3 (100%) of 3 signet ring cell, and 5 (50.0%) of 10 poorly differentiated tumors were positive. Other tumors showing occasional CDX2 staining included 1 of 30 well- or moderately differentiated neuroendocrine carcinomas of the lung and 2 of 43 from the pancreas, 1 of 47 lung adenocarcinomas, 3 of 57 pancreatic adenocarcinomas, and 15 of 256 endometrial carcinomas. Hepatocellular, poorly differentiated neuroendocrine carcinoma of the lung and squamous cell carcinomas of the lung were not immunoreactive for CDX2.

Conclusions.—CDX2 is a useful marker for intestinal-type differentiation, is rarely seen in tumors from the other sites evaluated, and may be useful in determining the site of origin for some metastatic tumors. However, CDX2 is not a sensitive marker for poorly differentiated colorectal carcinoma.

CDX2 as a marker of intestinal EC-cells and related well-differentiated endocrine tumors

Gastroenteropancreatic (GEP) endocrine tumors (ETs) are neoplasms showing different hormonal profiles and different clinical and prognostic features, which depend consistently on the site of origin. Histological features and general endocrine markers do not differentiate tumors in relation to their location, making it difficult to establish the site of origin of a GEP ET that has metastasized to the liver or lymph nodes. A site-specific marker would be particularly useful in the examination of small specimens where there is not sufficient material for an extensive study of the hormonal expression. CDX2 is a transcription factor that has been recently proposed as a marker of intestinal adenocarcinomas. Our aim was to evaluate the immunohistochemical expression of CDX2 in normal tissues and in 184 formalin-fixed and paraffin-embedded ETs to verify whether it could be used to identify intestinal ETs with a high degree of sensitivity and specificity. Of these cases, 154 were primary tumors (99 GEP and 55 non-GEP tumors), 101 were well-differentiated endocrine tumors, and 53 were poorly differentiated endocrine carcinomas (PDECs). Of the cases, 30 were metastases from differently located ETs. Nuclear CDX2 immunoreactivity was found in all EC-cells (serotonin-producing cells), in about 10% of G-cells (gastrin-producing cells), in about 30% of GIP-cells (gastric inhibitory peptide cells) and in a few motilin-positive cells of the normal intestinal mucosa, while other gastrointestinal endocrine cell types were CDX2 negative. All midgut EC-cell tumors, their metastases, and two of three pancreatic EC-cell ETs were diffusely and intensely CDX2 positive. The other GEP ETs, their metastases, as well as the non-GEP ETs, were all CDX2 negative, with the exception of four PDECs, five gastrinomas and one pheochromocytoma, which were only focally positive. We conclude that CDX2 may be considered a sensitive and specific marker of midgut EC-cells and EC-cell tumors, and its expression may be useful in the diagnosis of metastases from occult ETs.

Cdx2 as a marker for neuroendocrine tumors of unknown primary sites

The transcription factors CDX1 and CDX2 are homeobox genes that regulate development of the epithelium of the small and large intestine. A few studies have shown that Cdx2 protein expression is useful in the diagnosis of adenocarcinomas as well as neuroendocrine tumors of the small and large intestine. To examine the utility of Cdx2 in recognizing neuroendocrine tumors of unknown primary sites, we analyzed 224 primary and metastatic neuroendocrine tumors by immunohistochemistry. The specificity of the antibody reaction was confirmed by Western blotting. Cdx2 antibody stained all primary and most metastatic midgut carcinoid tumors. A few rectal and pulmonary carcinoids were positive, while gastric carcinoids were negative for Cdx2. One of five small cell carcinomas (20%) of the colon was positive for Cdx2, while all pulmonary small cell carcinomas were negative. Neuroendocrine tumors of the pituitary, parathyroid, medullary thyroid carcinomas, paragangliomas, pheochromocytomas and Merkel cell carcinomas were all negative for Cdx2. Western blot analysis of seven cases showed a 40 kDa band in both primary and metastatic midgut carcinoid tumors. These results indicate that Cdx2 can be very useful in recognizing metastatic neuroendocrine carcinomas of unknown primary sites, especially when they are derived from the small intestine.