In a recent article published in Cancer, Krishnamurthy et al used a pancytokeratin antibody cocktail (AE1/AE3, CAM5.2, MNF116, cytokeratin 8 [CK8], and CK18) to immunostain bone marrow cytospin specimens that were believed to contain disseminated tumor cells from patients with early stage breast cancer.1 They possibly overlooked the manufacturer's information, and used redundant anti-CAM5.2 and anti-CK8 monoclonal antibodies (MoAbs), which may misguide the readers when building a cost-effective comparable antibody cocktail for detecting such wide-spectrum CKs.
The anti-CK CAM5.2 MoAb, clone CAM 5.2 (BD Biosciences, Sparks, Md), reacts primarily with CK8 (52 kilodaltons [kD]). Anti-CK AE1/AE3, clone AE1/AE3 (Dako, Carpinteria, Calif), is comprised of 2 MoAbs. The AE1 MoAb identifies an antigenic determinant present on the majority of the A subfamily of CKs, including CKs with Moll designations 10, 13, 14, 15, 16, and 19 (molecular weights [MWs] of 56.5, 54′, 50, 50′, 48, and 40 kD, respectively). The AE3 MoAb identifies an antigenic determinant shared by the B subfamily of CKs including CKs 1, 2, 3, 4, 5, 6, 7, and 8 (MWs of 65, 67, 64, 59, 58, 56, 54, and 52 kD, respectively). Accordingly, the anti-CK CAM5.2 MoAb does not expand the detecting spectrum of anti-CK AE1/AE3.
Despite anti-CK8, clone C51 (Invitrogen, Carlsbad, Calif), and anti-CK18, clone DC10 (Invitrogen), the anti-CK8/CK18 MoAb, clone Zym5.2 (Invitrogen), recognizes human CKs with MWs of 52 kD and 45 kD, respectively, corresponding to CK8 and CK18. The anti-CK MNF116 MoAb, clone MNF116 (Dako), labels the numbers of discrete bands ranging from 40 kD to 58 kD on immunoblot analysis, corresponding to CK5, CK6, CK8, CK17, and most likely CK19. Accordingly, the anti-CK8/CK18 and MNF116 MoAbs offer the additional ability to detect CK17 and CK18, which are complementary to the antibody spectrum covered by the anti-CK AE1/AE3.
We clarified that the 3-antibody cocktail (panel), either AE1/AE3-MNF116-CK18 or AE1/AE3-MNF116-CK8/CK18, is sufficient in detecting similar broad-spectrum CKs including CKs 1 to 8, CK10, and CKs 13 to 19. The superfluous anti-CK CAM5.2 and anti-CK8 MoAbs seem to provide no remarkable advantages to the pancytokeratin cocktail (AE1/AE3-CAM5.2-MNF116-CK8-CK18) that used in this study.