Cancer drugs have unexpectedly led to an entirely new way to beat viral infections - and particularly smallpox - a new study suggests.Viruses are hard to stop and, with few exceptions, drugs aimed at killing viral infections have not worked nearly as well as the antibiotics that kill bacteria.Now, US scientists have found that an experimental drug aimed at stopping the uncontrolled growth of cancer cells actually prevents the smallpox virus from replicating inside human cells, and can save mice from dying of a closely related virus, Vaccinia.Viruses succeed by invading a cell and hijacking the “machinery” used by actively dividing cells to replicate their own DNA. But most cells frequently exposed to viruses - such as skin cells or those lining the lungs - are not actively dividing and so have their replication machinery turned off. Viruses such as smallpox have learned to turn it back on by making their own copies of the hormones and growth factors that normally induce cells to divide.Since the overexpression of the receptors for these growth factors in cancer cells is one of the reasons cancers grow uncontrollably, cancer research has focused on finding molecules that block the receptors.
