Stem cells give clues to understanding cancer and make breakthrough in childhood...(ake tumour samples and grow them in a va...),Health

Professor Ruiz i Altaba added, Hedgehog signalling appears to be involved in many kinds of stem cells and many kinds of cancers. Specifically, Gli-1 seems to be important for the proliferation of tumour cells and especially for the proliferation and perpetuation of cancer stem cells. We think the Gli code, the sum of all Gli activities, is locked in a hyperactivating state in cancer, and if we can revert it to a repressive state, this could provide a possible therapeutic approach.

Meanwhile Dr Manel Esteller of the Spanish National Cancer Research Centre (CNIO) in Madrid has been investigating the way that genes in cancer cells and stem cells are modified by a process called methylation[2].

In a cell not all of the genes are active. Some are rendered silent by the attachment of chemical entities called methyl groups. This is one of the mechanisms by which a cell can switch genes on and off. It has become clear that the pattern of DNA methylation is one key difference between a cell that has become specialised that is differentiated and one that remains undifferentiated.

We have studied plant DNA and have seen that in undifferentiated tissue one particular region of the DNA is always unmethylated, Dr Esteller told the meeting. In differentiated tissue this same region is methylated. If we take the undifferentiated cell and add the methylated gene we get differentiation.

A similar system appears to operate in human cells. And in some cancer cells there are particular patterns of DNA methylation. We have seen that in some leukaemias there is a gene involved in differentiation that is methylated, Dr Esteller said. In cultured cells we see that if we put the unmethylated gene b
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