Bovine Meat and Milk Factors

Bovine Meat and Milk Factors (BMMFs) are circular, single-stranded DNA molecules (cssDNAs) originally found in beef and cow's milk which have been linked to the development of cancer—particularly colorectal and breast cancer. They are formerly known as Slow Progressive Hidden INfections of variable X (SPHINX). Similar molecules have since been found in a much wider range of food.

BMMF/SPHINX sequences are able to copy themselves in animal cells. They encode functional proteins that are expressed in some animal cells. Every BMMF/SPHINX contains at least a "Rep" open reading frame, which encodes a replication endonuclease that, in HEK 293TT cells, acts to replicate and retain the cssDNA.

BMMF/SPHINX sequences are divided into four clades. Clades 1, 2, and 3 share sequence similarity with the plasmids of Acinetobacter baumannii. (A. baumanii regularly produces outer membrane vesicles containing these plamids, and animal cells are known to take up these vesicles.) Clade 4 shares sequence similarity with Gemycircularvirus.