β-CT appears to be a quantity control factor — overexpression of β-CT (Madoka et al., 2002), but not BCCP2 (Thelen and Ohlrogge, 2002) or BC (Shintani et al., 1997), could lead to a significant rise in protein levels of all other three subunits, though their mRNA levels were not affected. Here, PCYT1B is linked to breast cancer.