Identification of compounds that preferentially suppress the growth of T-cell acute lymphoblastic leukemia-derived cells

Abstract

T-cell acute lymphoblastic leukemia (T-ALL) is one of the most frequently occurring cancers in children and is associated with a poor prognosis. Here, we performed large-scale screening of natural compound libraries to identify potential drugs against T-ALL. We identified three low-molecular-weight compounds (auxarconjugatin-B, rumbrin, and lavendamycin) that inhibited the proliferation of the T-ALL cell line CCRF-CEM, but not that of the B lymphoma cell line Raji in a low concentration range. Among them, auxarconjugatin-B and rumbrin commonly contained a polyenyl 3-chloropyrrol in their chemical structure, therefore we chose auxarconjugatin-B for further analyses. Auxarconjugatin-B suppressed the in vitro growth of five human T-ALL cell lines and two T-ALL patient-derived cells, but not that of adult T-cell leukemia patient-derived cells. Cultured normal T cells were several-fold resistant to auxarconjugatin-B. Auxarconjugatin-B and its synthetic analogue Ra#37 depolarized the mitochondrial membrane potential of CCRF-CEM cells within 3 h of treatment. These compounds are promising seeds for developing novel anti-T-ALL drugs.

Keywords: T-ALL; anticancer compounds; depolarization; leukemia; mitochondria.

FIGURE 1

Identification of three natural compounds that selectively suppress the growth of CCRF‐CEM cells. The chemical structure (upper panels) and growth inhibitory activity (lower panels) of auxarconjugatin‐B (A), rumbrin (B), and lavendamycin (C) are shown. In the lower panels, CCRF‐CEM or Raji cells (3000) were cultured in the presence or absence of various concentrations of the indicated compounds. At 72 h after culture, the relative cell number (% to medium control) was determined. Each point represents an average of four well measurements ± SEM.

FIGURE 2

Growth inhibitory activities of the three natural compounds in various human leukemia and solid tumor‐derived cell lines. Cells (3000) were cultured in the presence or absence of 5 μM auxarconjugatin‐B, 2 μM lavendamycin, or 5 μM rumbrin. At 72 h after culture, the relative cell number (% to medium control) was determined. Each bar graph represents an average of four well measurements ± SEM.

FIGURE 3

Growth inhibitory activity of auxarconjugatin‐B and its chemical analogue in T‐ALL patient‐derived leukemic cells. Cells (3000) were cultured in the presence or absence of various concentrations of auxarconjugatin‐B (A) or Ra#37 (B). At 72 h after culture, the relative cell number (% to medium control) was determined. Each point represents an average of four well measurements ± SEM.

FIGURE 4

Growth inhibitory activity of Ra#37 in myeloid leukemia‐derived cell lines. The chemical structure (A) and growth inhibitory activity (B–D) of Ra#37 in TF‐1 (B), THP‐1 (C), and K562 (D) cells are shown. In (B)–(D), cells (3000) were cultured in the presence or absence of various concentrations of Ra#37. At 72 h after culture, the relative cell number (% to medium control) was determined. Each point represents an average of four well measurements ± SEM.

FIGURE 5

Growth inhibitory activities of Ra#37 in various human leukemia and solid tumor‐derived cell lines. Cells (3000) were cultured in the presence or absence of 2 μM Ra#37. At 72 h after culture, the relative cell number (% to medium control) was determined. Each bar graph represents an average of four well measurements ± SEM.

FIGURE 6

Intracellular localization of Ra#37. CCRF‐CEM (A) and Raji (B) cells were incubated with 10 μM Ra#37 or solvent control (DMSO) for 1 h followed by MitoTracker staining. Confocal microscopic images of Ra#37‐treated cells are shown. Scale bars = 10 μm.

FIGURE 7

Effect of Ra#37 on mitochondrial membrane potential. CCRF‐CEM and Raji cells were incubated with 10 μM Ra#37 or solvent control (DMSO) for 1 h, washed with medium, stained with JC‐10, and harvested immediately (indicated as 1 h) or after 2 h of incubation (indicated as 3 h). FACS profiles of orange fluorescence (generated by aggregated JC‐10 in polarized mitochondria) and green fluorescence (monomeric JC‐10) are shown.