Over-expression of Eph and ephrin genes in advanced ovarian cancer: ephrin gene expression correlates with shortened survival

BACKGROUND: Increased expression of Eph receptor tyrosine kinases and their ephrin ligands has been implicated in tumor progression in a number of malignancies. This report describes aberrant expression of these genes in ovarian cancer, the commonest cause of death amongst gynaecological malignancies. METHODS: Eph and ephrin expression was determined using quantitative real time RT-PCR. Correlation of gene expression was measured using Spearman's rho statistic. Survival was analysed using log-rank analysis and (was visualised by) Kaplan-Meier survival curves. RESULTS: Greater than 10 fold over-expression of EphA1 and a more modest over-expression of EphA2 were observed in partially overlapping subsets of tumors. Over-expression of EphA1 strongly correlated (r = 0.801; p < 0.01) with the high affinity ligand ephrin A1. A similar trend was observed between EphA2 and ephrin A1 (r = 0.387; p = 0.06). A striking correlation of both ephrin A1 and ephrin A5 expression with poor survival (r = -0.470; p = 0.02 and r = -0.562; p < 0.01) was observed. Intriguingly, there was no correlation between survival and other clinical parameters or Eph expression. CONCLUSION: These data imply that increased levels of ephrins A1 and A5 in the presence of high expression of Ephs A1 and A2 lead to a more aggressive tumor phenotype. The known functions of Eph/ephrin signalling in cell de-adhesion and movement may explain the observed correlation of ephrin expression with poor prognosis

The role of Eph receptors and ephrin ligands in colorectal cancer

Eph receptors and their ephrin ligands constitute the largest subfamily of receptor tyrosine kinases and are components of the cell signaling pathways involved during development. Eph and ephrin overexpression have been documented in a variety of human cancers including gastrointestinal malignancies and in particular colorectal malignancies. EphB and ephrin B proteins have been implicated in the homeostasis of the gastrointestinal tract where EphB2-and EphB3-ephrin B signaling regulates cell sorting in the mature epithelium. These proteins are also reported to be upregulated in colon carcinomas. The EphA/ephrin A system has also been implicated in epithelial tissue structure and function. More recently, EphA receptors and their corresponding ligands have been implicated in numerous malignancies. Of these, EphA2 in particular has been intensively investigated and has been proposed as a therapeutic target. An interesting observation emerging from these studies is the role for Ephs and ephrins in critical aspects of cell adhesion, migration and positioning, and a crucial role in tumor progression and metastasis. However, the underlying role of Ephs and ephrins in these processes has generally been studied on individual Eph or ephrin genes. Given the multiplicity of Eph expression on gut epithelial cells, a more global approach is needed to define the precise role of Eph-ephrin interaction in malignant transformation. Here, we will review the recent advances on the role of Eph-ephrin signaling in colorectal malignancies. © 2009 UICC

Complex expression patterns of Eph receptor tyrosine kinases and their ephrin ligands in colorectal carcinogenesis

Aberrant expression of Eph and ephrin proteins in human cancers is extensively documented. However, data are frequently limited to one gene and therefore incomplete and in some instances conflicting. We analysed expression of all Eph and ephrin genes in colorectal cancer (CRC) cell lines and 153 clinical specimens, providing for the first time a comprehensive analysis of this system in CRC. Eph/ephrin mRNA expression was assessed by quantitative real-time PCR and correlated with protein expression (flow cytometry, Western blotting and immunocytochemistry). These data show that EphA1, EphA2, EphB2 and EphB4 were significantly over expressed in CRC. In all cases, at least one Eph gene was found in normal colon (EphA1, EphA2, EphB2, EphB4), where expression was observed at high levels in most CRCs. However, other Eph gene expression was lost in individual CRCs compared to the corresponding normal, EphA7 being a striking example. Loss of expression was more common in advanced disease and thus correlated with poor survival. This is consistent with the redundant functionality of Eph receptors, such that expression of a single Eph gene is sufficient for effector function. Overall, the data suggest a progressive loss of expression of individual Eph genes suggesting that individual CRCs need to be phenotyped to determine which Eph genes are highly expressed. Targeted therapies could then be selected from a group of specific antibodies, such as those developed for EphA1

Varying etiologies lead to different molecular changes in Australian and South African hepatocellular carcinomas

There is significant regional variation in the etiologic agents responsible for hepatocellular carcinoma (HCC), which influences the genetic and epigenetic mechanisms of malignant transformation. The aim of the present study was to investigate the prevalence of allelic imbalance (AI) and CpG island methylation in HCCs from Australia and South Africa. Genomic DNA was extracted from malignant and non-malignant liver from 37 Australian and 24 South African HCCs and histologically normal liver from 20 transplant donors. AI was examined at 1p, 4p, 4q, 8p, 9p, 13q, 16q and 17p, using 23 microsatellite markers. Methylation status of p14, p16, p15, RIZ1, E-cadherin and O -MGMT was examined using methylation specific PCR, while MINTs 1, 2, 12, 25 and 31 were assessed using combined bisulfite restriction analysis. The highest prevalence of AI was observed at 9p (69%) and 17p (52%). AI was significantly higher in South African HCCs (

Silencing of O-6-methylguanine DNA methyltransferase in the absence of promoter hypermethylation in hepatocellular carcinomas from Australia and South Africa

The DNA repair protein O-6-methylguanine-DNA methyltransferase (MGMT) is involved in cellular defences against alkylating agents. Alterations in the MGMT gene may result in an increase in the mutation rate and risk of malignant transformation. We have previously shown that MGMT is implicated in colorectal carcinogenesis particularly in cancers which display microsatellite instability, a marker of impaired DNA repair. The aims of the current study were to assess the roles of MGMT and microsatellite instability in hepatocellular carcinomas (HCCs) from Australia and South Africa. DNA was extracted from malignant and non-malignant liver tissue from 37 Australian and 24 South African patients, and histologically normal liver from 20 transplant donors. MGMT promoter hypermethylation and MGMT protein expression were assessed using methylation specific PCR and immunohistochemistry. Microsatellite instability was examined using a panel of 23 microsatellite markers previously used to detect allelic imbalance and two specific markers for the detection of low levels of microsatellite instability. Methylation specific PCR did not detect any methylation of the MGMT promoter in Australian and South African HCCs. Similarly, no hypermethylation of MGMT was observed in the adjacent nonmalignant liver or histologically normal liver. MGMT staining was predominantly nuclear with some cytoplasmic staining. Overexpression of MGMT protein was detected in 14 (39%) HCCs, while a reduction in protein expression was evident in 14 (39%) HCCs. In the remaining 8 cases the expression of MGMT was comparable in HCCs and adjacent nonmalignant tissue. Interestingly, MGMT expression decreased relative to adjacent non-malignant liver tissue in patients who had aetiologies other than viral hepatitis for their underlying liver diseases (p < 0.02). No microsatellite instability was detected in this series of 61 HCCs. This suggests that epigenetic silencing of MGMT and microsatellite instability does not play an important role in this series of HCCs derived from different populations