Domestic scientists have cloned four pigs that can each produce a protein used in cancer treatment.

A research team at Chungnam National University and the biotech firm MGenbio on Wednesday said their scientists injected a human GM-CSF gene into a pig's somatic cells to create cloned embryos by implanting the cells into unfertilized eggs with their nuclei removed.

GM-CSF is a protein that promotes the growth of white blood cells. Used in treating anemia and leukemia and in bone marrow transplants, the protein can cost 600,000 dollars per gram.