Comparison of sensitivity to methioninase of methionine-addicted cancer cells and their isogenic methionine-independent revertants in vitro
(A) Diagram of the establishment of low-methionine-requirement (methionine-independent) revertants.
(B) Recombinant methioninase (rMETase) was used to deplete methionine in the cell culture medium. rMETase was added to the medium (1 U/mL) and the methionine level in the medium was measured at 0 h, 15 min, 30 min, 1 h, 3 h, 6 h, and 24 h (n = 3).
(C) Cell proliferation assay of methionine-addicted parental cancer cells and their isogenic methionine-independent revertants under methionine restriction by rMETase. Cells were cultured in methionine-containing medium or methionine-containing medium with rMETase (1 U/mL) for 24, 48, 72, and 96 h (mean ± SEM, n = 3. ∗∗∗, p < 0.001, Student’s t test).
(D) Cell proliferation assay of methionine-addicted parental cancer cells and their isogenic methionine-independent revertants in methionine-free medium containing 200 μM DL-homocysteine or 250 nM methylthioadenosine (MTA) with 10% dialyzed fetal bovine serum (mean ± SEM, n = 3. ∗, p < 0.05, Student’s t test).