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mTOR kinase inhibitors synergize with histone deacetylase inhibitors to kill B-cell acute lymphoblastic leukemia cells.

Beagle BR, Nguyen DM, Mallya S, Tang SS, Lu M, Zeng Z, Konopleva M, Vo TT, Fruman DA - Oncotarget (2015)

Bottom Line: However, emerging data indicate that mTOR inhibitors are most effective when combined with other target agents.We found that mTOR kinase inhibitors (TOR-KIs) synergize with HDAC inhibitors to cause apoptosis in B-ALL cells and the effect is greater when compared to rapamycin plus HDAC inhibitors.The combination of TOR-KIs with the clinically approved HDAC inhibitor vorinostat increased apoptosis in primary pediatric B-ALL cells in vitro.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology & Biochemistry, University of California, Irvine, CA.

ABSTRACT
High activity of the mechanistic target of rapamycin (mTOR) is associated with poor prognosis in pre-B-cell acute lymphoblastic leukemia (B-ALL), suggesting that inhibiting mTOR might be clinically useful. However, emerging data indicate that mTOR inhibitors are most effective when combined with other target agents. One strategy is to combine with histone deacetylase (HDAC) inhibitors, since B-ALL is often characterized by epigenetic changes that silence the expression of pro-apoptotic factors. Here we tested combinations of mTOR and pan-HDAC inhibitors on B-ALL cells, including both Philadelphia chromosome-positive (Ph+) and non-Ph cell lines. We found that mTOR kinase inhibitors (TOR-KIs) synergize with HDAC inhibitors to cause apoptosis in B-ALL cells and the effect is greater when compared to rapamycin plus HDAC inhibitors. The combination of TOR-KIs with the clinically approved HDAC inhibitor vorinostat increased apoptosis in primary pediatric B-ALL cells in vitro. Mechanistically, TOR-KI and HDAC inhibitor combinations increased expression of pro-death genes, including targets of the Forkhead Box O (FOXO) transcription factors, and increased sensitivity to apoptotic triggers at the mitochondria. These findings suggest that targeting epigenetic factors can unmask the cytotoxic potential of TOR-KIs towards B-ALL cells.

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MLN0128 is mainly cytostatic in human B-ALL cells(A) Cell lines (p190, SUP-B15) or (B) primary B-ALL cells (n = 3 independent specimens) were cultured for 48hr with vehicle or with RAP or MLN0128. The percent viable cells was measured by 7-AAD staining and flow cytometry. For the primary patient samples, cells were grown on stromal cells and viability was determined for human CD19+ cells. (C) DNA content analysis was used to assess cell cycle distribution in p190 and SUP-B15 cells after 48 of culture. * p < 0.05; ** p < 0.01, *** p<0.001, one-way ANOVA.
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Figure 1: MLN0128 is mainly cytostatic in human B-ALL cells(A) Cell lines (p190, SUP-B15) or (B) primary B-ALL cells (n = 3 independent specimens) were cultured for 48hr with vehicle or with RAP or MLN0128. The percent viable cells was measured by 7-AAD staining and flow cytometry. For the primary patient samples, cells were grown on stromal cells and viability was determined for human CD19+ cells. (C) DNA content analysis was used to assess cell cycle distribution in p190 and SUP-B15 cells after 48 of culture. * p < 0.05; ** p < 0.01, *** p<0.001, one-way ANOVA.

Mentions: TOR-KIs provide significant anti-leukemic effects in vitro and in vivo using both murine and human models of B-ALL [27, 28, 36]. Consistent with our previous study using PP242 [27], the clinical candidate compound MLN0128 [28] caused both cell death (Fig. 1A) and G0/G1 arrest (Fig. 1C) in BCR-ABL-transformed murine pre-B cells (p190 cells). In contrast, human Ph+ cell lines (SUP-B15 and BV-173), Ph-negative cell lines (Nalm-6, Blin-1, RS11;4, 697, REH, SEM, Kasumi-2) and primary cells from bone marrow of pediatric B-ALL patients (Ph-negative) were less sensitive to MLN0128 induced cytotoxicity (Fig. 1A, 1B, 2A, 2B and Supplementary Figure S1). In agreement with our previous findings [27], TOR-KIs caused greater cell cycle arrest and death in p190 cells than rapamycin (Fig. 1A, C). Similarly, MLN0128 caused greater cell cycle arrest than rapamycin in SUP-B15 cells (Fig. 1C).


mTOR kinase inhibitors synergize with histone deacetylase inhibitors to kill B-cell acute lymphoblastic leukemia cells.

Beagle BR, Nguyen DM, Mallya S, Tang SS, Lu M, Zeng Z, Konopleva M, Vo TT, Fruman DA - Oncotarget (2015)

MLN0128 is mainly cytostatic in human B-ALL cells(A) Cell lines (p190, SUP-B15) or (B) primary B-ALL cells (n = 3 independent specimens) were cultured for 48hr with vehicle or with RAP or MLN0128. The percent viable cells was measured by 7-AAD staining and flow cytometry. For the primary patient samples, cells were grown on stromal cells and viability was determined for human CD19+ cells. (C) DNA content analysis was used to assess cell cycle distribution in p190 and SUP-B15 cells after 48 of culture. * p < 0.05; ** p < 0.01, *** p<0.001, one-way ANOVA.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385838&req=5

Figure 1: MLN0128 is mainly cytostatic in human B-ALL cells(A) Cell lines (p190, SUP-B15) or (B) primary B-ALL cells (n = 3 independent specimens) were cultured for 48hr with vehicle or with RAP or MLN0128. The percent viable cells was measured by 7-AAD staining and flow cytometry. For the primary patient samples, cells were grown on stromal cells and viability was determined for human CD19+ cells. (C) DNA content analysis was used to assess cell cycle distribution in p190 and SUP-B15 cells after 48 of culture. * p < 0.05; ** p < 0.01, *** p<0.001, one-way ANOVA.
Mentions: TOR-KIs provide significant anti-leukemic effects in vitro and in vivo using both murine and human models of B-ALL [27, 28, 36]. Consistent with our previous study using PP242 [27], the clinical candidate compound MLN0128 [28] caused both cell death (Fig. 1A) and G0/G1 arrest (Fig. 1C) in BCR-ABL-transformed murine pre-B cells (p190 cells). In contrast, human Ph+ cell lines (SUP-B15 and BV-173), Ph-negative cell lines (Nalm-6, Blin-1, RS11;4, 697, REH, SEM, Kasumi-2) and primary cells from bone marrow of pediatric B-ALL patients (Ph-negative) were less sensitive to MLN0128 induced cytotoxicity (Fig. 1A, 1B, 2A, 2B and Supplementary Figure S1). In agreement with our previous findings [27], TOR-KIs caused greater cell cycle arrest and death in p190 cells than rapamycin (Fig. 1A, C). Similarly, MLN0128 caused greater cell cycle arrest than rapamycin in SUP-B15 cells (Fig. 1C).

Bottom Line: However, emerging data indicate that mTOR inhibitors are most effective when combined with other target agents.We found that mTOR kinase inhibitors (TOR-KIs) synergize with HDAC inhibitors to cause apoptosis in B-ALL cells and the effect is greater when compared to rapamycin plus HDAC inhibitors.The combination of TOR-KIs with the clinically approved HDAC inhibitor vorinostat increased apoptosis in primary pediatric B-ALL cells in vitro.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology & Biochemistry, University of California, Irvine, CA.

ABSTRACT
High activity of the mechanistic target of rapamycin (mTOR) is associated with poor prognosis in pre-B-cell acute lymphoblastic leukemia (B-ALL), suggesting that inhibiting mTOR might be clinically useful. However, emerging data indicate that mTOR inhibitors are most effective when combined with other target agents. One strategy is to combine with histone deacetylase (HDAC) inhibitors, since B-ALL is often characterized by epigenetic changes that silence the expression of pro-apoptotic factors. Here we tested combinations of mTOR and pan-HDAC inhibitors on B-ALL cells, including both Philadelphia chromosome-positive (Ph+) and non-Ph cell lines. We found that mTOR kinase inhibitors (TOR-KIs) synergize with HDAC inhibitors to cause apoptosis in B-ALL cells and the effect is greater when compared to rapamycin plus HDAC inhibitors. The combination of TOR-KIs with the clinically approved HDAC inhibitor vorinostat increased apoptosis in primary pediatric B-ALL cells in vitro. Mechanistically, TOR-KI and HDAC inhibitor combinations increased expression of pro-death genes, including targets of the Forkhead Box O (FOXO) transcription factors, and increased sensitivity to apoptotic triggers at the mitochondria. These findings suggest that targeting epigenetic factors can unmask the cytotoxic potential of TOR-KIs towards B-ALL cells.

Show MeSH
Related in: MedlinePlus