Protein critical for breast milk production found

Melbourne: Australian researchers have discovered a protein critical for sustaining milk production in the breast, rendering it essential for survival of mammalian species.

The protein called MCL-1 was found to be an important regulator of breast development and its milk-producing cells, researchers said.

"This study has unlocked one of the key survival factors in the mammary gland," said Professor Jane Visvader from the Walter and Eliza Hall Institute in Australia.

"MCL-1 is important for all stages of breast development, from puberty to pregnancy and lactation. Based on this discovery, it is reasonable to believe that every mammal requires MCL-1 for milk production and, ultimately, the survival of their offspring," said Visvader.

Researchers said MCL-1 levels increased dramatically in the breast within 12 hours of giving birth.

"We were able to use very sensitive technologies to determine that stem cells and luminal cells were the breast cells that most critically rely on MCL-1," Dr Nai Yang Fu from the institute said.

"Luminal cells are the cells that line breast ducts and respond to hormones during puberty, pregnancy and lactation. It now seems clear that MCL-1 is integral to the survival of these cells," said Yang Fu.

Visvader said the discovery further underscored the importance of MCL-1 for cell survival.

"In addition to our discovery, a number of recent research studies at our institute have shown that MCL-1 is important for the survival of certain immune cells, and for the survival and growth of cancers including leukaemia and lymphoma," she said.

"Stem cells and luminal progenitor cells both require MCL-1 for their survival. Our team has previously implicated both these cell types in some types of breast cancer, raising the question of whether MCL-1 is an important target for developing anti-cancer drugs," said Visvader.

Professor Geoff Lindeman from the institute said the research also identified that EGF - a growth factor - works in tandem with MCL-1 during lactation.

"EGF has emerged as a key inducer of MCL-1 at the switch to lactation," he said.

"It will be important to determine whether this mechanism also operates in breast cancer, as this could reveal new ways of targeting the disease," said Lindeman.

The study was published in the journal Nature Cell Biology.