Immunomodulatory drugs target IKZF1-IRF4-MYC axis in primary effusion lymphoma in a cereblon-dependent manner and display synergistic cytotoxicity with BRD4 inhibitors

Abstract

Primary effusion lymphoma (PEL) is an aggressive type of non-Hodgkin lymphoma localized predominantly in body cavities. Kaposi’s sarcoma-associated herpes virus is the causative agent of PEL. PEL is an incurable malignancy and has extremely poor prognosis when treated with conventional chemotherapy. Immunomodulatory drugs (IMiDs) lenalidomide and pomalidomide are FDA approved drugs for the treatment of various ailments. IMiDs display pronounced anti-proliferative effect against majority of PEL cell lines within their clinically achievable concentrations, by arresting cells at G0/G1 phase of cell-cycle, and without any induction of KSHV lytic-cycle reactivation. Although microarray examination of PEL cells treated with lenalidomide revealed activation of interferon (IFN) signaling, blocking the IFN pathway did not block the anti-PEL activity of IMiDs. The anti-PEL effects of IMiDs involved cereblon-dependent suppression of IRF4 and rapid degradation of IKZF1, but not IKZF3. Small hairpin-RNA (shRNA) mediated knockdown of MYC enhanced the cytotoxicity of IMiDs. Bromodomain and extraterminal domain (BET) proteins are epigenetic readers which perform a vital role in chromatin remodeling and transcriptional regulation. BRD4, a widely expressed transcriptional coactivator, belongs to BET family of proteins, which has been shown to co-occupy the super-enhancers associated with MYC. Specific BRD4 inhibitors were developed which suppress MYC transcriptionally. Lenalidomide displayed synergistic cytotoxicity with several structurally distinct BRD4 inhibitors (JQ-1, IBET151, and PFI-1). Furthermore, combined administration of lenalidomide and BRD4 inhibitor JQ-1 significantly increased the survival of PEL bearing NOD.SCID mice in an orthotopic xenograft model as compared to either agent alone. These results provide compelling evidence for clinical testing of IMiDs alone and in combination with BRD4 inhibitors for PEL.

RNA Polymerase I Inhibition with CX‐5461 as a Novel Therapeutic Strategy to Target MYC in Multiple Myeloma

“…Inhibition of the ubiquitin proteasome pathway may lead to MYC protein stabilization, and thus enhance myeloma sensitivity to CX-5461 (Gregory and Hann 2000, Holien , et al 2012), making this a potentially attractive regimen. In contrast, it is plausible that down regulation of the IKZF1/3 - IRF4 - MYC axis by immunomodulatory drugs, such as lenalidomide and pomalidomide, may reduce the efficacy of CX-5461 (Gopalakrishnan , et al 2016, Kronke , et al 2014). Indeed, when the BET bromodomain inhibitor JQ1, which suppresses MYC transcription, was combined with CX-5461 in myeloma cell lines as part of our preliminary studies, an antagonistic effect was observed (data not shown).…”

Phase 1 study of lenalidomide plus dose‐adjusted EPOCH‐R in patients with aggressive B‐cell lymphomas with deregulated MYC and BCL2

“…[13][14][15][16] Lenalidomide also targets drivers of MYC expression such as nuclear factor κB and the transcription factors Aiolos and Ikaros, which support possible activity in MYC-driven malignancies. [17][18][19][20] Moreover, patients with DHL and DEL have high rates of central nervous system (CNS) disease recurrence, 3,4,21 and the documented activity of lenalidomide against CNS lymphoma may help to prevent this typically fatal event. 22,23 Therefore, we initiated a phase 1 study to evaluate the feasibility and toxicity of DA-EPOCH-R plus lenalidomide in patients with DHL and DEL, and to establish a recommended phase 2 dose for further investigation.…”

Inhibition of bromodomain and extra-terminal (BET) proteins increases NKG2D ligand MICA expression and sensitivity to NK cell-mediated cytotoxicity in multiple myeloma cells: role of cMYC-IRF4-miR-125b interplay

“…However, in our experimental system, treatment of SKO-007(J3) cells with JQ1 only slightly decreased the expression of the IKZF1 and IKZF3 (Additional file 6A–C); as a control, lenalidomide completely abrogated the expression of these two transcription factors, further suggesting that the upregulation of MICA mediated by BETi was mainly dependent on the repression of IRF4. Noteworthy, as shown in Additional file 6E, the combination of the two treatments (lenalidomide + BETi) further increased the expression of MICA, suggesting the possibility that low-dose combinations of IMiDs with BETi could display additional or synergistic activities in MM, as already shown in primary effusion lymphoma (PEL) preclinical data, where the simultaneous targeting of IKZF1-IRF4-MYC increased the cytotoxic effect as compared with either agent alone [48]. In this context, in MM, the combined activities of these two classes of drugs could be able to improve direct cytotoxicity and, at the same time, to enhance the expression of NK cell-activating ligands.…”