Dysregulation of apoptosis is a major mechanism in the lymph node involvement in colorectal carcinoma.

The purpose of this study was to define gene expression profile changes in colorectal tumors in order to identify target genes involved in neoplastic progression. cDNA microarray analysis was used to detect differences in gene expression profiles between colon tumor samples obtained from 20 patients in different tumor stages. Genes included in the cDNA microarray were selected according to their role in the cell cycle, apoptosis process, drug resistance and transcription factor regulation. Cluster analysis showed 2 well differentiated gene expression profiles between colorectal tumors with or without lymph node involvement. Some of these genes are important regulators of apoptotic pathways (DAD1, APO3, DRAK1 or BIK), suggesting that this process could be associated with node involvement. Subsequent analysis of certain genes identified in the microarray analysis were confirmed by quantitative real-time PCR. Our data suggest that microarray technology could discriminate between the involvement of regional lymph node in colon cancer where apoptosis-related genes would be implied. This preliminary analysis also suggests that the gene expression profile may be useful in improving risk-group stratification.

Gene expression profile induced by BCNU in human glioma cell lines with differential MGMT expression.

Chemotherapy with the alkylating agent BCNU (1,3-bis (2-chloroethyl)-1-nitrosourea) is the most commonly used chemotherapeutic agent for gliomas. However, the usefulness of this agent is limited because tumor cell resistance to BCNU is frequently found in clinical brain tumor therapy. The O6-methylguanine-DNA methyltransferase protein (MGMT) reverses alkylation at the O6 position of guanine and we have reported the role of MGMT in the response of brain tumors to alkylating agents. However, the different mechanisms underlying the patterns related to MGMT remain unclear. To better understand the molecular mechanism by which BCNU exerts its effect in glioma cell lines according MGMT expression, we used microarray technology to interrogate 3800 known genes and determine the gene expression profiles altered by BCNU treatment. Our results showed that treatment with BCNU alters the expression of a diverse group of genes in a time-dependent manner. A subset of gene changes was found common in both glioma cell lines and other subset is specific of each cell line. After 24 h of BCNU treatment, up-regulation of transcription factors involved in the nucleation of both RNA polymerase II and III transcription initiation complexes was reported. Interestingly, BCNU promoted the expression of actin-dependent regulators of chromatin. Similar effects were found with higher BCNU doses in MGMT+ cell line showing a similar mechanism that in MGMT-deficient cell with standard doses. Our data suggest that human glioma cell lines treated with BCNU, independently of MGMT expression, show changes in the expression of cell cycle and survival-related genes interfering the transcription mechanisms and the chromatin regulation.