Snake venom slows tumour growth, according to Francis Markland of the University of Southern California School of Medicine. Mice implanted with human breast cancer cells showed a 60-70 per cent reduction in the growth rate of breast tumours and a 90 per cent reduction of tumour spread to the lungs of the animals when treated with the protein contortrostatin (CN), which is purified from the venom of the southern copperhead snake. The protein is effective in slowing the spread of tumour cells because it inhibits their adhesion to and invasion of normal cells in the nearby tissue. Clinical trials using CN to treat breast cancer in women could start soon. Professor Markland reported his findings to this week's American Chemical Society conference.