Bovine
lactoferricin (LfcinB) is a
cationic antimicrobial peptide that selectively induces apoptosis in several different types of human
cancer cells. However, the potential use of LfcinB as an
anticancer agent is presently limited by the need for relatively high concentrations of the
peptide to trigger apoptosis.
Ceramide is a membrane
sphingolipid that is believed to function as a second messenger during apoptosis. In this study, we investigated the role of
ceramide in LfcinB-induced apoptosis in CCRF-CEM and Jurkat T-
leukemia cell lines. Exposure to LfcinB caused nuclear condensation and fragmentation,
poly(ADP-ribose) polymerase (PARP) cleavage, and DNA fragmentation in CCRF-CEM and Jurkat T-cell
acute lymphoblastic leukemia cell lines. Treatment with C6
ceramide, a cell-permeable, short-chain
ceramide analog, also induced apoptotic nuclear morphology, PARP cleavage, and DNA fragmentation in T-
leukemia cells. Although LfcinB treatment did not cause
ceramide to accumulate in CCRF-CEM or Jurkat cells, the addition of C6
ceramide to LfcinB-treated T-
leukemia cells resulted in increased DNA fragmentation. Furthermore, modulation of cellular
ceramide metabolism either by inhibiting
ceramidases with D-erythro-2-(N-myristoylamino)-1-phenyl-1-propanol or
N-oleoylethanolamine, or by blocking
glucosylceramide synthase activity with
1-phenyl-2-palmitoylamino-3-morpholino-1-propanol, enhanced the ability of LfcinB to trigger apoptosis in both Jurkat and CCRF-CEM cells. In addition, LfcinB-induced apoptosis of T-
leukemia cells was enhanced in the presence of the
antiestrogen tamoxifen, which has multiple effects on
cancer cells, including inhibition of
glucosylceramide synthase activity. We conclude that manipulation of cellular
ceramide levels in combination with LfcinB
therapy warrants further investigation as a novel strategy for the treatment of T cell-derived
leukemias.