Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2018 Jun 26;9(49):29193-29207.
doi: 10.18632/oncotarget.25670.

BET inhibition in advanced cutaneous T cell lymphoma is synergistically potentiated by BCL2 inhibition or HDAC inhibition

Sa Rang Kim  1 , Julia M Lewis  1 , Benoit M Cyrenne  1 , Patrick F Monico  1 , Fatima N Mirza  1 , Kacie R Carlson  1 , Francine M Foss  2 , Michael Girardi  1
Affiliations

BET inhibition in advanced cutaneous T cell lymphoma is synergistically potentiated by BCL2 inhibition or HDAC inhibition

Sa Rang Kim et al. Oncotarget. .

Abstract

While several systemic therapies are approved for cutaneous T cell lymphoma (CTCL), a non-Hodgkin lymphoma of skin-homing T cells that may involve lymph nodes and peripheral blood in advanced stages, relapses are common. Mutational analysis of CTCL cells has revealed frequent amplification of the MYC oncogene, and bromodomain and extraterminal (BET) protein inhibitors have been shown to repress MYC expression in various malignancies. Towards a potential novel therapy, we thus sought to examine the effect of BET inhibition on CTCL cells in vitro. Each of the four tested BET inhibitors (JQ1, ABBV-075, I-BET762, CPI-0610) consistently induced dose-dependent decreases in viability of isolated patient-derived CTCL cells and established CTCL cell lines (MyLa, Sez4, HH, Hut78). This effect was synergistically potentiated by combination of BET inhibition with BCL2 inhibition (e.g. venetoclax) or histone deacetylase (HDAC) inhibition (e.g. vorinostat or romidepsin). There was also a marked increase in caspase 3/7 activation when JQ1 was combined with either vorinostat or romidepsin, confirming that the observed synergies are due in major part to induction of apoptosis. Furthermore, MYC and BCL2 expression were each synergistically repressed when CTCL cells were treated with JQ1 plus HDAC inhibitors, suggesting cooperative activities at the level of epigenetic regulation. Taken together, these data indicate that targeting BET proteins in CTCL represents a promising novel therapeutic strategy that may be substantially potentiated by combination with BCL2 or HDAC inhibition.

Keywords: BET inhibition; CTCL; HDAC inhibition; apoptosis.

PubMed Disclaimer

Conflict of interest statement

CONFLICTS OF INTEREST The authors declare no competing financial interests.

Figures

Figure 1
Figure 1. The BET inhibitor JQ1 substantially decreases the viability of patient-derived CTCL cells and CTCL cell lines
All samples were incubated with JQ1 for 72 hours and dose-response curves were generated, from which IC50 and hill slopes were calculated. (A) IC50 of patient-derived samples in increasing order. The median and mean IC50s were 4.29 µM and 6.05 µM, respectively. Mycosis fungoides (MF) patients are in blue and Sézary syndrome (SS) patients are in red. (B) Comparison of IC50 with CTCL subtype at the time of diagnosis as either MF or SS. (C) Comparison of IC50 with CTCL B stage based on ISCL classification. (D) Representative dose-response curves for patient-derived samples. (E) Dose-response curves for cell lines. (F) Comparison of IC50 with MYC amplification status in patient-derived samples. (G) Comparison of IC50 with MYC amplification status in cell lines. ns, p > 0.05; pt, patient; *p < 0.05.
Figure 2
Figure 2. BET inhibitors in clinical development (ABBV-075, I-BET762, CPI-0610) are variably effective in limiting CTCL cell viability
(A) Representative dose-response curves of CTCL cells derived from patient 11 to different BET inhibitors. (B) Comparison of average IC50s of BET inhibitors from patient-derived samples. ABBV-075 and JQ1 were tested against eight patient-derived samples; I-BET-762 and CPI-0610 were tested against five patient-derived samples. Patient codes and individual IC50s are provided in Supplementary Table 1. *p < 0.05; **p < 0.01.
Figure 3
Figure 3. BCL2 inhibitors or HDAC inhibitors synergistically potentiate BET inhibition against patient-derived CTCL cells
(A) The combination index (CI) at 10% viability was calculated for nine patient-derived samples (listed in Supplementary Table 2) exposed to JQ1 combined with venetoclax, vorinostat, or romidepsin, using the Chou-Talalay method. Strong synergy is defined as CI < 0.3, moderate synergy is CI < 0.7, and weak synergy is CI < 0.9 (adapted from Chou). (B) Calculated CI at 10% viability for six patient-derived samples exposed to ABBV-075 combined with venetoclax, vorinostat, or romidepsin. Synergy was note in all patient-derived samples. (C) Representative viability curves for BET inhibitors (JQ1 or ABBV-075) and their combinations with venetoclax, vorinostat, or romidepsin (patient 10).
Figure 4
Figure 4. Effects of BET inhibition and its potentiation by HDAC inhibition are mediated in part by induction of apoptosis by caspase 3/7
Average caspase 3/7 activity at 24 hours, shown as fold change from the control, for four patient-derived samples (patient 4, 9, 11, and 12) incubated with (A) JQ1 and vorinostat, (B) JQ1 and romidepsin, and (C) JQ1 and venetoclax. Caspase 3/7 activity over 48 hours shown for patient 9 following incubation with (D) JQ1 and vorinostat, (E) JQ1 and romidepsin and (F) JQ1 and venetoclax. *p < 0.05; **p < 0.01; ***p < 0.001. For (D–F), +indicates p-value against JQ1 and *indicates p-value against vorinostat, romidepsin or venetoclax.
Figure 5
Figure 5. Combination of BET inhibition and HDAC inhibition markedly represses MYC and BCL2 expression in CTCL cells
Seven patient-derived samples (listed in Supplementary Table 3) were incubated with the indicated agents or vehicle control for 24 hours and changes in gene expression evaluated by qRT-PCR. Change in gene expression as represented by fold change from untreated for (A) JQ1 and vorinostat, (B) JQ1 and romidepsin, and (C) JQ1 and venetoclax. There was a striking decrease in MYC and BCL2 expression when JQ1 was combined with either vorinostat or romidepsin. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001.
See this image and copyright information in PMC

Comment in

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Kim EJ, Hess S, Richardson SK, Newton S, Showe LC, Benoit BM, Ubriani R, Vittorio CC, Junkins-Hopkins JM, Wysocka M, Rook AH. Immunopathogenesis and therapy of cutaneous T cell lymphoma. J Clin Invest. 2005;115:798–812. - PMC - PubMed
    1. Girardi M, Heald PW, Wilson LD. The pathogenesis of mycosis fungoides. N Engl J Med. 2004;350:1978–1988. - PubMed
    1. Kazakov DV, Burg G, Kempf W. Clinicopathological spectrum of mycosis fungoides. J Eur Acad Dermatol Venereol. 2004;18:397–415. - PubMed
    1. Wilcox RA. Cutaneous T-cell lymphoma: 2014 update on diagnosis, risk-stratification, and management. Am J Hematol. 2014;89:837–851. - PubMed
    1. Willemze R, Jaffe ES, Burg G, Cerroni L, Berti E, Swerdlow SH, Ralfkiaer E, Chimenti S, Diaz-Perez JL, Duncan LM, Grange F, Harris NL, Kempf W, et al. WHO-EORTC classification for cutaneous T cell lymphomas. Blood. 2005;105:3768–3785. - PubMed