Memorial Sloan-Kettering Cancer Center scientists led by cancer biologist Joan Massagué have discovered a new branch in the signaling network of a protein called transforming growth factor-beta (TGF- ). The branch, described in the June 2 issue of Cell, is part of a larger TGF- signaling pathway known to control the production of mature red blood cells. [PubMed Abstract]

In 1987, Dr. Massagué was part of a team that identified the ability of TGF- to direct blood stem cell fate. This process involves two steps: halting cell division and stimulating cell differentiation. The first step is achieved through a part of the TGF- signaling pathway that already has been well characterized.

"The surprise now is that within this pathway there is a separate and novel branch responsible for the differentiation step," said Dr. Massagué, senior author of the study. "Furthermore, this branch involves a previously obscure protein -- transcriptional intermediary factor 1 [TIF1]."

Investigators studying the TGF- signaling pathway uncovered the branch after identifying TIF1 and noting that in this protein's absence blood stem cells did not fully differentiate in cell culture. This finding further elucidates the signaling network of TGF-, a protein that has been well studied in cancer research because it both promotes and inhibits cell growth in many different types of cells.