Targeting of endothelin system genes is a promising strategy in cancer therapy. The modulation of these genes was explored in a model of colorectal cancer (CRC) liver metastasis and in a panel of CRC tumor cell lines that were exposed to the demethylating agent decitabine. The CC531 rat model mimicking CRC liver metastasis was used for tumor cell re-isolation and analysis of the endothelin system genes and DNA methyltransferases (DNMTs) by microarray. To mimic the effects caused by methylation changes, a panel of seven CRC cell lines was treated with the demethylating agent decitabine. Three genes of the endothelin system were potently modulated at messenger RNA (mRNA) level in rat CC531 cells during liver colonization. The concomitant decrease of two DNMTs suggested an influence from altered methylation. Changes in gene expression were also accomplished by exposure of CRC cells to the demethylating agent decitabine, when using daily low concentrations for 3 days, with minimal cytotoxic effects. Sensitive human SW480 cells showed an almost 100fold upregulation of endothelin-1 mRNA compared to untreated cells. This, however, was different in LS174T cells, which showed no significant increase in gene expression although the methylation levels were significantly decreased at a variety of corresponding loci. We suggest that the mechanism induced by methylation on gene expression in metastatic CRC cells can be compromised. The results question the overall success of treating metastatic CRC by methylation inhibitors.

Cimetidine is an H2 receptor antagonist that has an antiandrogenic effect. It intervenes with the conversion of testosterone into estrogen in the Sertoli cells with accompanying testicular structural changes. In the present study, the microscopic and the ultrastructural changes induced by cimetidine and the effect of vitamin B12 as a protective agent on rat testes were studied. Immunoexpression of estrogen receptor β (ERβ) in testes was evaluated. Twenty-four adult male rats were divided into four groups: control, cimetidine-treated, vitamin B12 treated, and combined cimetidine and vitamin B12 treated. The experimental rats were administered with cimetidine and/or vitamin B12 for 52 days. Group II rats showed marked atrophy of the seminiferous tubules with a significant increase in tubular diameter and decrease in the tubular luminal and epithelial areas. Ultrastructure of this group showed irregular Sertoli cells with basal cytoplasmic vacuolation and significantly thickened basement membrane. ERβ immunoexpression was similar to controls. Group III rats showed near normal seminiferous tubular structures with minimal cellular alterations and the immunoreactivity of the testicular sections was very close to normal. However, group IV rats showed markedly immunopositive detached cells, spermatids, and primary spermatocytes. Cimetidine interferes with the control of spermatogenesis as evidenced by microscopic and ultrastructural studies and affection of ERβ receptors and vitamin B12 has a protective action against this harmful effect.

Endothelin system members including endothelin-1, endothelin-2, endothelin-3, endothelin receptors, and