Session: 651. Multiple Myeloma and Plasma Cell Dyscrasias Basic and Translational: Genomic Markers of Disease Progression and Therapeutic Response
Hematology Disease Topics & Pathways:
Research, Fundamental Science, Biological therapies, Translational Research, Plasma Cell Disorders, Diseases, Gene Therapy, Therapies, Lymphoid Malignancies
We analyzed our RNA-seq dataset of CD138+ cells from >300 MM patients and 70 MM cell lines for these transcripts and observed reads from regions of MIR17HG that are not included in miR-17-92. Using qRT-PCR and single molecule RNA FISH, we identified the expression of a nuclear-enriched, ~5k-nt long, polyA(+) lncRNA. This lncRNA, named lnc-17-92 was quickly downregulated within a few hours of exposure to ASOs targeting the MIR17HG pre-RNA. Using DROSHA-knockout MM cells, in which MIR17HG produces lnc-17-92 but not miR-17-92, we found that targeting the MIR17HG pre-RNA effectively antagonized MM cell growth. Using easy-to-manipulate cellular models (e.g., HCT-116), we observed stronger rescue by ectopic expression of lnc-17-92, as compared to miR-17-92, after targeting MIR17HG pre-RNA.
Using RNA-protein pull down (RPPD) and RNA yeast-3-hybrid (Y3H) assays, we found that the transcription factor c-MYC and the epigenetic modulator WDR82 were binding partners for lnc-17-92. In fact, we found that lnc-17-92 mediated their protein–protein interaction by providing the chromatin scaffold for the assembly of a MYC–WDR82 complex at the promoter region of ACC1. This gene encodes the limiting enzyme for de novo lipogenesis, a metabolic pathway that we show is controlled by lnc-17-92 to promote MM cell growth.
Using three different cellular models (P493-6, HMECMYC, and U226MYC), we found that targeting MIR17HG pre-RNA preferentially killed MYC+ cells. This could be explained both by lnc-17-92 acting as a chromatin scaffold for MYC and also the known role of miR-17-92 in fine-tuning the downstream transcriptional program of MYC. However, we also observed that lnc-17-92 protected MYC from proteasomal degradation and found that the miR-17-92 member miR-92a negatively regulated MYC protein expression via an, as yet, unknown mechanism. The concerted action of lnc-17-92 and miR-17-92 on MYC protein stability is under investigation and updates will also be presented.
Finally, we explored MIR17HG as a therapeutic target, which includes targeting both its lncRNA and miRNAs. To develop clinically applicable inhibitors, we screened >80 fully phosphorothioated (PS), 2’-O-methoxyethyl (2’-MOE)-modified, lipid-conjugated ASOs that could either trigger RNase H–mediated degradation of MIR17HG pre-RNA (gapmeRs) or exert function via an RNase H–independent mechanism (blockmeRs). We identified an 18-mer tocopherol (T)-conjugated gapmeR G2-15b-T (“G”) and an 18-mer tocopherol (T)-conjugated steric blocker SB9-19-T (“B”). We found they had potent anti-tumor effects both in vitro and in vivo in three pre-clinical animal models, including a clinically relevant PDX-NSG mouse model. Tumor growth inhibition ranged from 100% (regression) to 50% in these models. Inhibitors did not cause overt toxicity in the mice, as shown by blood cell count, clinical, and body weight analysis. These inhibitors are currently being developed for translation to clinical trials.
Altogether, our studies characterize a novel oncogenic mechanism for MIR17HG and provide clinically applicable inhibitors.
Disclosures: Chauhan: Oncopeptides: Consultancy; Stemline Therapeutics: Consultancy; C4 Therapeutics: Current equity holder in publicly-traded company. Anderson: Janssen: Membership on an entity's Board of Directors or advisory committees; Precision Biosciences: Membership on an entity's Board of Directors or advisory committees; Window: Membership on an entity's Board of Directors or advisory committees; Dynamic Cell Therapy: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Raqia: Other: Scientific founder ; OncoPep: Other: Scientific founder ; NextRNA: Other: Scientific founder ; C4 Therapeutics: Other: Scientific founder ; Starton: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Mana Therapeutics: Membership on an entity's Board of Directors or advisory committees. Munshi: Bristol-Myers Squibb: Consultancy; Adaptive Biotechnology: Consultancy; Pfizer: Consultancy; Karyopharm: Consultancy; Abbvie: Consultancy; Novartis: Consultancy; Oncopep: Consultancy, Current equity holder in publicly-traded company, Other: scientific founder, Patents & Royalties; Legend: Consultancy; Takeda Oncology: Consultancy; Celgene: Consultancy; GSK: Consultancy; Amgen: Consultancy; Janssen: Consultancy.
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