The Rational Therapeutics blog has a post on Vitamin D and triple-negative breast cancer that I find especially intriguing. For example, vitamin D actually operates like a hormone and interacts with other hormone receptors, such as estrogen and progesterone. Too little of it brings a susceptibility to TNBC:
What is vitamin D? Well, although we refer to it as a vitamin, it is, in fact, a hormone. It is obtained from the diet or from exposure to sun. The most potent form of vitamin D is that associated with sunlight exposure. Once in the body, vitamin D interacts with cells at very specific receptors. The term receptor reflects the role of these “landing sites” contained within the cell’s nucleus. As the vitamin D molecule traverses the cell membrane and enters the cell nucleus, it binds with the vitamin D receptor, which connects to the chromosome at a hormone response element and drives the cell machinery forward.
The vitamin D receptor is part of a large collection of genes called the steroid super gene family. These include receptors for estrogen, progesterone, testosterone, and, yes, vitamin D. Read more.