Viral killing of tumor stem cells

Helsinki, Finland

It is to be expected that tumor cells possess altered biological characteristics in comparison to their non-malignant counterparts. One very interesting method of targeting tumors is through the use of viruses that have a specific tissue trophism towards neoplastically transformed tissue. For example, it is known that human reovirus can only grow in cells that have an activated ras pathway, a common feature of many tumors. Various oncolytic viruses have entered the clinic and are reviewed in Crompton et al. From ONYX-015 to armed vaccinia viruses: the education and evolution of oncolytic virus development. Curr Cancer Drug Targets. 2007 Mar;7(2):133-9.

While viruses may target tumor tissue, the question is whether they can target tumor stem cells. A recent paper (Eriksson M,Oncolytic Adenoviruses Kill Breast Cancer Initiating CD44CD24 Cells. Mol Ther. 2007 Sep 11) demonstrated that indeed this may be the case.

The investigators isolated stem cells from primary samples of breast cancer patients. More specifically, the stem cells were isolated from pleural effusions based on the CD44+ CD24- phenotype. It was shown that the oncolytic viruses Ad5/3-Delta24 and Ad5.pk7-Delta24 were effective against advanced orthotopic CD44CD24-derived tumors by targeting undifferentiated tumor stem cells.