CERS4 and breast cancer: However, in these studies the elevated levels in cancer specimens compared to normal tissues were consistent throughout all Cer species (C14:0, C16:0, C18:0, C18:1, C20:0, C22:0, C24:0, C24:1, C26:0 and C26:1), due to a significant increase of activity of CerS2, CerS4, Cer5 and CerS6, suggesting that the effects of the different Cer species on BC growth might result from complex and inter-regulated activity of different CerS.