[In situ analyses of molecular mechanisms of colorectal carcinogenesis]

The main signaling pathways of colorectal carcinogenesis encompass the classical adenoma-carcinoma sequence and the serrated route. In the classical adenoma-carcinoma sequence there are initially frequent mutations of the APC gene which lead to an activation of the WNT signaling pathway. When the WNT signaling pathway is activated β-catenin mediates the transcription of diverse factors which cause migration, invasion and proliferation of cells. Although APC mutations occur in all tumor cells, a heterogeneous distribution pattern of β-catenin is found in tumors and β-catenin also represents an important prognostic marker. A similar picture is found for γ-catenin which is expressed independently from β-catenin. Clearly more homogeneous is the expression of TCF4 and LEF1 which are the main binding partners of β-catenin and γ-catenin and are likewise important prognostic markers. The TRAIL signaling pathway is therapeutically interesting and within this pathway loss of the main receptors TRAIL-R1 and TRAIL-R2 is frequently found. Furthermore, the membranous localization of both factors correlates with a better overall survival. These results might be therapeutically relevant with respect to therapy with recombinant TRAIL molecules binding to TRAIL-R1 and TRAIL-R2. In the serrated route oncogen-induced senescence caused by mutations of the KRAS and BRAF oncogenes initially plays an important role. This senescence blockade is overcome by hypermethylation of the p16(INK4a) promoter and leads to the development of invasive tumors. The SIRT1 and c-Myc genes also contribute to progression of lesions in the serrated route and are activated through the RAS/RAF/MAPK-kinase signaling pathway as well as the WNT/β-catenin signaling pathway.

A genetic progression model of Braf(V600E)-induced intestinal tumorigenesis reveals targets for therapeutic intervention

We show that BRAF(V600E) initiates an alternative pathway to colorectal cancer (CRC), which progresses through a hyperplasia/adenoma/carcinoma sequence. This pathway underlies significant subsets of CRCs with distinctive pathomorphologic/genetic/epidemiologic/clinical characteristics. Genetic and functional analyses in mice revealed a series of stage-specific molecular alterations driving different phases of tumor evolution and uncovered mechanisms underlying this stage specificity. We further demonstrate dose-dependent effects of oncogenic signaling, with physiologic Braf(V600E) expression being sufficient for hyperplasia induction, but later stage intensified Mapk-signaling driving both tumor progression and activation of intrinsic tumor suppression. Such phenomena explain, for example, the inability of p53 to restrain tumor initiation as well as its importance in invasiveness control, and the late stage specificity of its somatic mutation. Finally, systematic drug screening revealed sensitivity of this CRC subtype to targeted therapeutics, including Mek or combinatorial PI3K/Braf inhibition.

Up-regulation of c-MYC and SIRT1 expression correlates with malignant transformation in the serrated route to colorectal cancer

Approximately 7.5% of all colorectal cancers are considered to originate from the alternative, serrated route. Here, we investigate the expression of the c-MYC oncogene and the SIRT1 protein deacetylase by immunohistochemical staining in subgroups of colorectal serrated lesions that were characterized by different molecular alterations. The expression of c-MYC and SIRT1 correlated with the presence of KRAS and BRAF mutations and high expression of c-MYC and SIRT1 was strongly associated with higher grades of malignancy. In contrast, in the majority of serrated lesions without KRAS or BRAF mutations, c-MYC and SIRT1 expression was not found increased. In this group only a subset of mostly high grade intraepithelial neoplasia and carcinoma was characterized by elevated c-MYC and SIRT1 expression. This was associated with nuclear localization of beta-catenin, indicating that Wnt pathway activation may confer transcriptional induction of c-MYC. In summary, we established a link between oncogenic K-Ras and B-Raf, suggesting post-transcriptional regulation of c-MYC through MAPK/ERK1/2 pathway activation, as well as for Wnt signalling to the activation of the c-MYC oncogene, and consequently of SIRT1 in the serrated route. The increasing expressions with higher grades of malignancy suggest crucial functions for c-MYC and SIRT1 in the progression of serrated lesions to colorectal cancer. These functions may include antagonizing of apoptosis and senescence, which are characteristic features of serrated lesions.

Loss of TRAIL-receptors is a recurrent feature in pancreatic cancer and determines the prognosis of patients with no nodal metastasis after surgery

INTRODUCTION

Agonistic antibodies targeting TRAIL-receptors 1 and 2 (TRAIL-R1 and TRAIL-R2) are being developed as a novel therapeutic approach in cancer therapy including pancreatic cancer. However, the cellular distribution of these receptors in primary pancreatic cancer samples has not been sufficiently investigated and no study has yet addressed the issue of their prognostic significance in this tumor entity.

AIMS AND METHODS

Applying tissue microarray (TMA) analysis, we performed an immunohistochemical assessment of TRAIL-receptors in surgical samples from 84 consecutive patients affected by pancreatic adenocarcinoma and in 26 additional selected specimens from patients with no lymph nodes metastasis at the time of surgery. The prognostic significance of membrane staining and staining intensity for TRAIL-receptors was evaluated.

RESULTS

The fraction of pancreatic cancer samples with positive membrane staining for TRAIL-R1 and TRAIL-R2 was lower than that of cells from surrounding non-tumor tissues (TRAIL-R1: p<0.001, TRAIL-R2: p = 0.006). In addition, subgroup analyses showed that loss of membrane staining for TRAIL-R2 was associated with poorer prognosis in patients without nodal metastases (multivariate Cox regression analysis, Hazard Ratio: 0.44 [95% confidence interval: 0.22-0.87]; p = 0.019). In contrast, analysis of decoy receptors TRAIL-R3 and -R4 in tumor samples showed an exclusively cytoplasmatic staining pattern and no prognostic relevance.

CONCLUSION

This is a first report on the prognostic significance of TRAIL-receptors expression in pancreatic cancer showing that TRAIL-R2 might represent a prognostic marker for patients with early stage disease. In addition, our data suggest that loss of membrane-bound TRAIL-receptors could represent a molecular mechanism for therapeutic failure upon administration of TRAIL-receptors-targeting antibodies in pancreatic cancer. This hypothesis should be evaluated in future clinical trials.

Microsatellite instability, KRAS mutations and cellular distribution of TRAIL-receptors in early stage colorectal cancer

Background

The fact that the receptors for the TNF-related apoptosis inducing ligand (TRAIL) are almost invariably expressed in colorectal cancer (CRC) represents the rationale for the employment of TRAIL-receptors targeting compounds for the therapy of patients affected by this tumor. Yet, first reports on the use of these bioactive agents provided disappointing results. We therefore hypothesized that loss of membrane-bound TRAIL-R might be a feature of some CRC and that the evaluation of membrane staining rather than that of the overall expression of TRAIL-R might predict the response to TRAIL-R targeting compounds in this tumor.

Aim and Methods

Thus, we evaluated the immunofluorescence pattern of TRAIL-receptors and E-cadherin to assess the fraction of membrane-bound TRAIL-receptors in 231 selected patients with early-stage CRC undergoing surgical treatment only. Moreover, we investigated whether membrane staining for TRAIL-receptors as well as the presence of KRAS mutations or of microsatellite instability (MSI) had an effect on survival and thus a prognostic effect.

Results

As expected, almost all CRC samples stained positive for TRAIL-R1 and 2. Instead, membrane staining for these receptors was positive in only 71% and 16% of samples respectively. No correlation between KRAS mutation status or MSI-phenotype and prognosis could be detected. TRAIL-R1 staining intensity correlated with survival in univariate analysis, but only membranous staining of TRAIL-R1 and TRAIL-R2 on cell membranes was an independent predictor of survival (cox multivariate analysis: TRAIL-R1: p = 0.019, RR 2.06[1.12–3.77]; TRAIL-R2: p = 0.033, RR 3.63[1.11–11.84]).

Conclusions

In contrast to the current assumptions, loss of membrane staining for TRAIL-receptors is a common feature of early stage CRC which supersedes the prognostic significance of their staining intensity. Failure to achieve therapeutic effects in recent clinical trials using TRAIL-receptors targeting compounds might be due to insufficient selection of patients bearing tumors with membrane-bound TRAIL-receptors.

A simple immunohistochemical algorithm predicts the risk of distant metastases in right-sided colon cancer

AIMS

A test predicting distant metastases would be valuable for prognostication in colon cancer (CC). In previous studies, CC with microsatellite instability (MSI) showed a reduced risk of distant metastases. High expression of CD133 and β-catenin, both related to cancer stem cell phenotypes, might be predictive markers for metastasis. The aim of this study was to develop a simple and robust test for risk assessment of distant metastases in CC.

METHODS AND RESULTS

In a case-control study, 57 cases of right-sided CC specimens with synchronous distant metastases were matched with 57 CC without distant metastases. Immunohistochemistry for MLH1, CD133 and nuclear β-catenin was carried out. To define the diagnostic algorithm the tumours were first stratified according to their MLH1 expression. Loss of MLH1 expression was correlated significantly with a very low risk of distant metastases (5.3%; P = 0.00003). In MLH1-positive cases, combined high scores of CD133 and β-catenin were associated with a very high rate of distant metastases (94.4%), whereas the risk was intermediate for carcinomas with either low CD133 and/or low β-catenin expression (P = 0.0007). A validation study using an independent set of 68 right-sided CC specimens showed a clear trend towards risk stratification according to the algorithm; however, sample sizes were small, and associations were not statistically significant.

CONCLUSIONS

By the use of three markers, this algorithm allowed identification of subgroups of right-sided CC patients with extremely high and extremely low risk of distant metastases.

SOX2 expression correlates with lymph-node metastases and distant spread in right-sided colon cancer

Background

The transcription factor SOX2, which is involved in the induction of pluripotent stem cells and contributes to colorectal carcinogenesis, is associated with a poor prognosis in colon cancer (CC). Furthermore, SOX2 is a repressor of the transcriptional activity of β-catenin in vitro. Since the majority of CC develop via an activation of the Wnt/β-catenin signalling pathway, indicated by nuclear expression of β-catenin, we wanted to investigate the expression patterns of SOX2 and β-catenin and correlate them with the occurrence of lymph node and distant metastases as indicators of malignant progression.

Methods

The expression of SOX2 and β-catenin was investigated in a case control study utilizing a matched pair collection (N = 114) of right-sided CCs with either corresponding distant metastases (N = 57) or without distant spread (N = 57) by applying immunohistochemistry.

Results

Elevated protein expression of SOX2 significantly correlated with the presence of lymph node- (p = 0.006) and distant metastases (p = 0.022). Nuclear β-catenin expression correlated significantly only with distant metastases (p = 0.001). Less than 10% of cases showed a coexpression of high levels of β-catenin and SOX2. The positivity for both markers was also associated with a very high risk for lymph-node metastases (p = 0.007) and distant spread (p = 0.028).

Conclusion

We demonstrated that increased expression of either SOX2 or nuclear β-catenin are associated with distant metastases in right-sided CC. Additionally, SOX2 is also associated with lymph-node metastases. These data underline the importance of stemness-associated markers for the identification of CC with high risk for distant spread.

Partial avulsion of prosthetic aortic valve caused by S. epidermidis infection resulting in a giant false aneurysm of the complete thoracic aorta

A 69-year-old man was presented with a holosystolic and early diastolic murmur in cardiac auscultation, pretibial edema and elevated inflammation markers. Aortic valve and ascending aorta had been replaced 9 months earlier. Transesophageal echocardiography revealed massive eccentric regurgitation and dehiscence of the aortic valve, resulting in a giant circular false aneurysm with connection to the lumen of the aortic arch. CT and MR confirmed extensive leakage in a covered perforation. The false lumen was confined by a newly formed vessel wall, since the native Aorta ascendens had been excised. Smooth muscle cells expressing the progenitor marker CD34 were detected selectively in this region, indicating a contribution of circulating progenitor cells to the false vessel wall. After detection of Staphylococcus epidermidis in blood, another urgent Bentall operation was performed. However, the patient succumbed to right ventricular failure and multiple organ failure on postoperative day 1.

Differential LEF1 and TCF4 expression is involved in melanoma cell phenotype switching

Recent observations suggest that melanoma cells drive disease progression by switching back and forth between phenotypic states of proliferation and invasion. Phenotype switching has been linked to changes in Wnt signalling, and we therefore looked for cell phenotype-specific differences in the levels and activity of β-catenin and its LEF/TCF co-factors. We found that while cytosolic β-catenin distribution is phenotype-specific (membrane-associated in proliferative cells and cytosolic in invasive cells), its nuclear distribution and activity is not. Instead, the expression patterns of two β-catenin co-factors, LEF1 and TCF4, are both phenotype-specific and inversely correlated. LEF1 is preferentially expressed by differentiated/proliferative phenotype cells and TCF4 by dedifferentiated/invasive phenotype cells. Knock-down experiments confirmed that these co-factors are important for the phenotype-specific expression of M-MITF, WNT5A and other genes and that LEF1 suppresses TCF4 expression independently of β-catenin. Our data show that melanoma cell phenotype switching behaviour is regulated by differential LEF1/TCF4 activity.

LEF-1 and TCF4 expression correlate inversely with survival in colorectal cancer

BACKGROUND

Most colorectal carcinomas are driven by an activation of the canonical Wnt signalling pathway, which promotes the expression of multiple target genes mediating proliferation inavasion and invasion. Upon activation of the Wnt signalling pathway its key player β-catenin translocates from the cytoplasm to the nucleus and binds to members of the T-cell factor (TCF)/lymphoid enhancer factor (LEF-1) family namely LEF-1 and TCF4 which are central mediators of transcription. In this study we investigated the expression of β-Catenin, LEF1 and TCF4 in colorectal carcinomas and their prognostic significance.

METHODS

Immunohistochemical analyses of LEF-1, TCF4 and nuclear β-Catenin were done using a tissue microarray with 214 colorectal cancer specimens. The expression patterns were compared with each other and the results were correlated with clinicopathologic variables and overall survival in univariate and multivariate analysis.

RESULTS

LEF-1 expression was found in 56 (26%) and TCF4 expression in 99 (46%) of colorectal carcinomas and both were heterogeneously distributed throughout the tumours. Comparing LEF-1, TCF4 and β-catenin expression patterns we found no correlation. In univariate analysis, TCF4 expression turned out to be a negative prognostic factor being associated with shorter overall survival (p = 0.020), whereas LEF-1 expression as well as a LEF-1/TCF4 ratio were positive prognostic factors and correlated with longer overall survival (p = 0.015 respectively p = 0.001). In multivariate analysis, LEF-1 and TCF4 expression were confirmed to be independent predictors of longer respectively shorter overall survival, when considered together with tumour stage, gender and age (risk ratio for LEF-1: 2.66; p = 0.027 risk ratio for TCF4: 2.18; p = 0.014).

CONCLUSIONS

This study demonstrates different prognostic values of LEF-1 and TCF4 expression in colorectal cancer patients indicating different regulation of these transcription mediators during tumour progression. Moreover both factors may serve as new potential predictive markers in low stage colon cancer cases in advance.

γ-Catenin is an independent prognostic marker in early stage colorectal cancer

PURPOSE

Expression and role of γ-catenin in colorectal carcinogenesis is not well understood. We aimed at characterizing γ-catenin's expression pattern during colorectal carcinogenesis.

METHODS

The expression pattern of γ-catenin was characterized in adenomas, primary colorectal carcinomas, and their corresponding metastases. Since this descriptive immunohistochemical analysis revealed upregulation of γ-catenin in the invasive front of both primary tumors and metastases, a tissue microarray (TMA) was performed, allowing for correlation of subcellular expression patterns with disease recurrence and cancer-specific survival. Comparison of γ-catenin expression with that of β-catenin was performed.

RESULTS

In normal colonic epithelium and adenomas, γ-catenin was weakly expressed at the membrane. In central areas of primary colorectal carcinomas, membranous and cytoplasmatic expression was present, with cytoplasmatic and nuclear upregulation of γ-catenin in the invasive fronts. Expression patterns found in metastases resembled those of their respective primary tumors. Subsequent TMA analysis showed that upregulation of cytoplasmatic γ-catenin in the invasive fronts of curatively resected early T2 and T3 colorectal carcinomas was associated with shortened disease-free survival and an increased risk of death (p=0.003; hazard ratio = 2.98; 95% confidence interval, 1.44-6.18).

CONCLUSIONS

The correlation of upregulated cellular γ-catenin levels with higher recurrences and impaired survival suggests a tumor promoting role of γ-catenin in colorectal cancer. γ-Catenin may therefore serve as a marker for identifying patients who are at increased risk of disease recurrence who may benefit from closer follow-up and adjuvant therapy.

Ink4a/Arf and oncogene-induced senescence prevent tumor progression during alternative colorectal tumorigenesis

Colonic cancers with a serrated morphology have been proposed to comprise a molecularly distinct tumor entity following an alternative pathway of genetic alterations independently of APC mutations. We demonstrate that intestinal epithelial cell specific expression of oncogenic K-ras(G12D) in mice induces serrated hyperplasia, which is characterized by p16(ink4a) overexpression and induction of senescence. Deletion of Ink4a/Arf in K-ras(G12D) expressing mice prevents senescence and leads to invasive, metastasizing carcinomas with morphological and molecular alterations comparable to human KRAS mutated serrated tumors. Thus, we suggest that oncogenic K-ras represents a key player during an alternative, serrated pathway to colorectal cancer and hence propose RAS-RAF-MEK signaling apart from APC as an additional gatekeeper in colorectal tumor development.

Abstract LB-252: Expression of FGF-2 is essential for the maintenance of cancer stem cell characteristics in human colorectal tumor cell lines

Colorectal cancers (CRCs) consist of tumor cells with different capabilities. A small subpopulation of these tumor cells is characterized by signs of dedifferentiation and is able to induce in small numbers heterogeneous tumors when implanted subcutaneously into immunocompromised mice. This subpopulation of tumor cells is known to resemble cancer stem cells (CSCs). CSCs from colorectal cancers (CoCSCs) are considered to be characterized by nuclear ß-CATENIN, the central effector protein of the WNT signaling pathway that is dysregulated in most colorectal carcinomas. Interestingly, nuclear ß-CATENIN induces epithelial-mesenchymal transition (EMT) which is known to be intimately associated with the induction of stemness in formerly epithelial cells. Therefore, a mechanism mediated by stabilized ß-CATENIN might render CoCSCs independent of adequate WNT regulated niche conditions as they are known to be important for their normal counterparts in the intestine. Importantly, for in vitro maintenance of CoCSCs the addition of FGF-2 (fibroblast growth factor-2) to the culture medium is mandatory for their dedifferentiated phenotype. Since we detected that FGF-2 is a ß-CATENIN target gene and thus endogenously expressed by colorectal tumor cells, we hypothesized that this endogenous FGF-2 might be part of the ß-CATENIN regulated mechanism for the maintenance of CSC characteristics also in cultivated colorectal tumor cell lines.

In a first experimental approach, we prepared side populations (sp) from Caco2 and LoVo cells. Sp are known to contain CSCs. Our sp cells did not only express higher levels of the CoCSC markers CD44, CD166 and CD133 but also significantly increased values of FGF-2. To investigate the importance of FGF-2 we stably knocked down (kd) the FGF-2 expression in LoVo and Caco2 cells using RNA interference (RNAi). Knock down of FGF-2 led to a strong reduction in anchorage independent growth as well as tumor formation after xenografting into nude mice indicative for a less transformed phenotype. Moreover, LoVo FGF-2 kd cells displayed less mesenchymal characteristics like downregulation of vimentin and upregulation of E-cadherin at the same time as shown by real time PCR, Western Blotting and immunofluorescence. Importantly, the sp and thus the CSC fraction from LoVo FGF-2 kd cells was almost 90% reduced compared to the control cell line.

Taken together, we show evidence that the ß-CATENIN target gene FGF-2 is implicated in the transformation of colorectal tumor cells and is also important for the maintenance of mesenchymal- as well as CSC characteristics. Our results are thus another piece of evidence for the outstanding role of ß-CATENIN in colorectal carcinogenesis and might offer potential therapeutic strategies against one of its important downstream effectors that obviously plays an important role in the generation of an autonomous, ß-CATENIN regulated CSC niche.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-252.

Prognostic significance of the cancer stem cell markers CD133, CD44, and CD166 in colorectal cancer

CD133, CD44, and CD166 are cell surface markers that have recently been associated with colorectal cancer stem cells. As which of these markers has the greatest impact on patient prognosis is currently unknown, we compared their expression and prognostic significance in 110 colorectal adenocarcinomas. We demonstrate that expression of CD133 correlates with that of CD166, while both do not correlate with CD44. We show that CD133 is the best sole marker to predict low patient survival, while the combined analysis of all three markers may be superior in identification of low-, intermediate-, and high-risk cases of colorectal cancer.

ITF-2 is disrupted via allelic loss of chromosome 18q21, and ITF-2B expression is lost at the adenoma-carcinoma transition

BACKGROUND & AIMS

The ubiquitously expressed basic helix-loop-helix transcription factor ITF-2B has an important role in differentiation processes, and its transcription is regulated by beta-catenin. The ITF-2 gene is located in the chromosomal region 18q21; allelic loss of this locus occurs in 70% of colorectal cancers. We analyzed the expression, regulation, and function of ITF-2B in colorectal carcinogenesis.

METHODS

The loss-of-heterozygosity (LOH) status of 18q21 and expression of ITF-2B were studied in colorectal carcinomas using polymerase chain reaction-based methods and immunohistochemistry. The biologic effects of ITF-2B were studied in colorectal cancer cells. Reporter gene assays and chromatin immunoprecipitation were utilized to analyze effects of ITF-2B on gene transcription.

RESULTS

ITF-2B is strongly expressed in colon adenomas but frequently down-regulated in carcinomas because of LOH at 18q21. ITF-2B induces cell cycle arrest and regulates the expression of p21(Cip1) via newly identified E-boxes in the CDKN1A gene, independently of p53. Loss of ITF-2B expression correlates with loss of p21(Cip1) expression in primary colon carcinomas.

CONCLUSIONS

Accumulation of mutations and allelic losses are driving forces of colorectal carcinogenesis. ITF-2B, which is up-regulated during early colorectal carcinogenesis because of loss of adenomatous polyposis coli, is a target for LOH on chromosome 18q, along with deleted in colorectal carcinoma and Smad4. This finding, along with the fact that ITF-2B is a regulator of the key cell cycle inhibitor p21(Cip1), indicates that ITF-2B is a tumor suppressor that has an important function at the adenoma to carcinoma transition.

The intratumoral distribution of nuclear beta-catenin is a prognostic marker in colon cancer

BACKGROUND

Most colon cancers harbor mutations of APC or beta-catenin, both of which may lead to nuclear beta-catenin accumulation in the tumor cells and constitutively activated expression of its target genes. In many colon cancers, however, nuclear beta-catenin accumulation is heterogeneous throughout the tumor and often confined to the tumor margin. Herein, the authors investigated whether the intratumoral distribution of nuclear beta-catenin can serve as a prognostic marker for survival and tumor progression of stage IIA colon cancer patients.

METHODS

In total, 142 patients with primarily resected, moderately differentiated stage IIA colon cancer were included in this study. The patterning of nuclear beta-catenin expression was evaluated on immunohistochemically stained whole tissue sections of the tumors and was correlated with cancer-specific survival and disease-free survival using univariate and multivariate statistical analyses.

RESULTS

Four distinct patterns of nuclear beta-catenin expression were identified, and 2 main categories comprising tumors with or without intratumoral regulation of nuclear beta-catenin were distinguished. Moreover, the results demonstrated that the patterning, and especially the regulation or absence of regulation of nuclear beta-catenin expression, was a strong predictive marker of patient survival and tumor progression.

CONCLUSIONS

The current results indicated that the distribution of nuclear beta-catenin expression can be used as a good prognostic marker in patients with stage IIA colon cancer. Thus, the evaluation of nuclear beta-catenin may help to identify patients who will have a shorter than average survival and patients with a greater risk of disease progression who may be considered for adjuvant therapeutic modalities and intensified clinical aftercare in the future.

CD133 and nuclear beta-catenin: the marker combination to detect high risk cases of low stage colorectal cancer

Nuclear beta-catenin and CD133 are linked with two hallmarks of colon cancer, wingless-type mouse mammary tumour virus integration site (WNT)-pathway dysregulation and colon cancer stem cells (Co-CSCs), respectively. Both molecules may be related, as Co-CSCs were proposed to require activated WNT-signalling and as CD133 was postulated as a WNT/beta-catenin target gene. Herein, we investigated the expression of these markers on serial sections of 162 stage IIA colonic adenocarcinomas. We found that the expression of these molecules is statistically independent and that they mark distinct but overlapping subpopulations of the tumour cells. Moreover, we show that their combined evaluation can identify colon cancer cases with vastly reduced survival (hazard ratio (HR) 13.4, 95% confidence interval (CI): 4.7-38.2) and a high risk of tumour progression (HR 6.8, 95%CI: 3.1-15.0). In conclusion, the independence of these markers may on the one hand have implications for their presumed value to identify Co-CSCs; on the other hand it allows their combined analysis to become a powerful tool to identify high risk cases of stage IIA colon cancer.

p16INK4a is a beta-catenin target gene and indicates low survival in human colorectal tumors

BACKGROUND & AIMS

Human colorectal carcinomas display an infiltrative front of invasion where tumor cells undergo an epithelomesenchymal transition associated with low survival. Epithelomesenchymal transition is regulated by a nuclear beta-catenin accumulation, and subsequently, activation of beta-catenin/TCF4 target genes similar to CYCLIN D(1). Unexpectedly, these tumor cells are characterized by low proliferation, which correlates with the expression of the cell cycle inhibitor p16(INK4A). Therefore, we investigated the molecular mechanism of the transcriptional regulation of p16(INK4A) in colorectal cancer and its correlation with survival.

METHODS

Molecular biological techniques were used for investigating the transcriptional mechanisms of the p16(INK4A) gene regulation. Moreover, p16(INK4A) expression was correlated with the 10-year survival of patients with colorectal carcinomas.

RESULTS

In colorectal carcinomas, expression of the p16(INK4A) gene is regulated by beta-catenin/TCF4 and correlates with low survival rates of patients with tumors displaying an infiltrative front of invasion.

CONCLUSIONS

beta-catenin/TCF4 regulates cell cycle promoting (c-MYC, CYCLIN D(1)) and inhibiting genes (p16(INK4A)) at the same time in the mesenchymally differentiated tumor cells at the front of invasion. The function of p16(INK4A) seems to supersede in this context thus leading to low proliferation. Moreover, these tumor cells seem to govern the outcome of colorectal cancer independently of their proliferation.

Plasma cell granuloma of the thyroid gland mimicking carcinoma: A case report and review of the literature

Plasma cell granulomas (PCG) are rare tumor-like lesions consisting of sheets of polyclonal plasma cells admixed with numerous lymphocytes and other inflammatory cells surrounded by fibrous stroma. They usually appear in the lung, but involvement of diverse extrapulmonal sites has been described. PCGs occurring in the thyroid are very uncommon. Since 1981, only 11 cases have been described in the English literature. Here, we present the case of a 50-year-old Arabic man who noticed an enlargement of his thyroid gland during the previous 2 years, and he developed swallowing disturbances and a feeling of narrowness in the neck. A nearly total resection of the thyroid gland was made because of clinical suspicion of carcinoma. On histologic examination, PCG of the thyroid associated with Hashimoto's thyroiditis (HT) was diagnosed. This is the first case in which molecular pathological analyses for EBV and HHV8 DNA were made. As these were negative, distinct etiological features were suggested.

Pitfalls in the detection of t(11;22) translocation by fluorescence in situ hybridization and RT-PCR: a single-blinded study

The t(11;22) translocation is a diagnostic hallmark of various small round-cell tumors. This study correlates the performance of fluorescence in situ hybridization (FISH) and reverse transcription polymerase chain reaction (RT-PCR) in the detection of this translocation analyzing paraffin-embedded tissue specimens. As negative control samples, 10 cases of normal colon mucosa and 10 cases of colon carcinoma tissue were analyzed by FISH to determine a valid cutoff value for the diagnosis of a t(11;22) translocation. The mean number of false-positive nuclei differed significantly between disomic and polysomic control group cases (P=0.002). Therefore, the cutoff value was determined considering the pitfall polysomy. The analysis group consisted of 20 cases from the University of Düsseldorf and 10 cases from the University of Bonn. These cases were analyzed using PCR (Düsseldorf) and FISH (Bonn) using a single-blinded approach. Twenty-two cases (73.3%) were concordant in both methods. Five cases (16.7%) were discrepant, showing a positive result in FISH whereas PCR was negative. Three cases (10.0%) were analyzed by FISH, and PCR failed for nonoptimized tissue preparation. In conclusion, the detection of t(11;22) translocation is critically dependent on a thoroughly defined cutoff value for FISH and on appropriate tissue preparation for both methods. We recommend FISH as a sensitive screening tool in the detection of t(11;22) followed by subsequent PCR amplification of the specific chimeric transcript.