MEMPHIS, April 16 (UPI) -- U.S. medical researchers say they have linked a combination of genetic mutations to an aggressive form of acute lymphoblastic leukemia.

St. Jude Children's Research Hospital scientists said the series of genetic mutations work together to initiate most cases of the often-fatal ALL. The finding, they said, could lead to new cancer-fighting therapies

The defects -- known as "cooperating oncogenic lesions" -- include the deletion of a gene, IKZF1, whose protein, Ikaros, normally helps guide the development of a blood stem cell into a lymphocyte. The researchers also found that loss of the same gene accompanied the transformation of chronic myelogenous leukemias to a life-threatening acute stage.

"These findings provide new avenues to pursue to gain a better understanding of these disease processes and, ultimately, to develop better therapies," said Dr. James Downing, St. Jude's scientific director.

He said the study adds further support to a key concept in cancer genetics -- that malignancies frequently require mutations in multiple genes in order to develop.

The research is reported in the online edition of the journal Nature.