Absence of c-kit expression in HD and ALK-positive ALCL cell lines and tumors. (A) Top: Expression of c-kit mRNA in HD and ALCL cell lines as detected by RT-PCR as described elsewhere5 using the following primers: 5′-ACACCCTGTTCACTCCTTTGCTGA-3′ (forward), and 5′-GACTCCTTTGAATGCAGAAGA-3′ (reverse). The ST-882 and MO7e cell lines served as positive controls. Bottom: Immunoblots showing expression of c-kit protein in HD and ALCL cell lines. All HD and ALCL cell lines tested were negative for c-kit. A 145-kDa band corresponding to c-kit receptor was detected only in the ST-882 and MO7e control cell lines. β-actin served as a control for the amount of protein loaded in each well. (B,C) Representative cases of classical HD (B) and ALK-positive ALCL (C) showing no c-kit immunoreactivity in tumor cells. Note that occasional plasma cells are positive for c-kit. Original magnifications: B, × 200; C, × 400. Stained with immunoperoxidase with hematoxylin counterstain.
