Highlights
- Researchers discovered that loss of the patrolling monocyte population following inactivation of a molecular switch turns on gene Nr4a1.
- Mice lacking gene Nr4a1, therefore lacking patrolling monocytes, underwent unchecked metastasis, supporting the idea that patrolling monocytes play anti-cancer roles.
- Monocytes disappear following global Nr4a1 loss proving that the gene is necessary for development of that cell type.
- Directly targeting genes within a specific cell type is important for targeted therapies.
The study, published in the November 15, 2016, edition of Immunity, reports the loss of the same patrolling monocyte population following inactivation of a molecular switch that turns on Nr4a1.
"This new work is exciting, because it shows that we can directly target genes within a specific cell type, which is important for targeted therapies," says Hedrick, a Professor in the Division of Inflammation Biology.
The Hedrick laboratory's previous demonstration that patrolling monocytes disappear following global Nr4a1 loss proved that the gene is necessary for development of that cell type.
Later, her group reported that cancer cells injected into mice lacking Nr4a1, therefore lacking patrolling monocytes, underwent unchecked metastasis, supporting the idea that patrolling monocytes play anti-cancer roles.
Scientists call tissue-specific gene regulatory elements as "enhancers." They then showed that when activated, that DNA region, which they called "enhancer #2" (E2), was capable of switching on Nr4a1 expression only in patrolling monocytes, and not in macrophages.
To confirm that macrophages throw an entirely different molecular switch to turn on Nr4a1, the group exposed mice missing the monocyte E2 switch to a noxious toxin found in bacterial membranes, as a way of seeing whether macrophages can still mount normal inflammatory responses.
Indeed, the macrophage response was entirely normal in E2 mutants, unlike the global Nr4a1 "knockout", showing that macrophages do not use the genetic E2 switch.
The lungs of mutant mice contained many more melanoma cells than did lungs of normal mice. This confirmed that the gene regulatory switch is highly specific to one cell type, monocytes and that tumor cell invasion in the absence of this population had nothing to do with deregulated macrophage activity.
Hedrick also thinks the new findings provide new understanding of just how important DNA enhancer regions can be. "Being able to selectively target specific cell types opens up a new world for understanding how to design therapies to treat disease," she says.
Source-Medindia