Increase of Mitochondrial Activity Contributes to the Bortezomib-Relapsed in Multiple Myeloma, a Novel Therapeutic Opportunity

• Published in: Blood 2019-11, Vol.134 (Supplement_1), p.4408-4408
• Main Authors: Ortiz-Ruiz, Alejandra, Ruiz-Heredia, Yanira, Samur, Mehmet, Aguilar-Garrido, Pedro, Morales, Maria Luz, Valeri, Antonio, Garcia-Ortiz, Almudena, Barrio, Santiago, Bárcena, Carmen, Garcia-Martin, Rosa Maria, Garrido, Vanesa, Fulciniti, Mariateresa, Munshi, Nikhil C., Cedena, María Teresa, Martinez-Lopez, Joaquin, Linares, Maria, Gallardo, Miguel
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2019-123950

Introduction Mitochondria controls crucial biological pathways such as proliferation, apoptosis and cell growth. However, the implication of mitochondrial activity in the pathogenesis of Multiple Myeloma (MM) still remains unknown and only a few studies connect the mitochondrial status and MM. We planned to decipher the role of the mitochondria in the MM mechanism of resistance and the potential exploitation of mitochondrial activity as a functional target in the MM therapy. Methods In order to understand the role of mitochondria in MM and its therapeutic exploitation, firstly we explored factors involved in the mitochondrial function (c-Myc, HNRNPK, TFAM, NRF1 and EF-Tu) from 770 MM patients RNAseq CoMMpass℠ data. Furthermore, we performed different studies in our MM 77 patients set: gene expression validation by RT-PCR (n=40), protein expression (COXII) by IHC (n=28); and mitochondrial activity (COX activity) by histoenzymatic-HE assay (n=11). Additionally, we analyzed the impact of bortezomib in the mitochondria regulator CD38 in 50 samples (n=30 RVD, n=20 RD regimens), at diagnosis and 6/9 months follow-up MM patients. We have tested the effect of tigecycline, a mitochondrial inhibitor, in three regimens: monotherapy, pre-treament of tigecycline (48h) with consecutive bortezomib treatment, and in combination with bortezomib in the MM cell lines JJN3, L363 and NCI-H929. To characterize the molecular mechanisms underlying the cytotoxic effect of tigecycline we analysed mitochondria load and activity (MitoTracker green and red) OXPHOS expression by WB and COX2 activity by HE assay. Finally, we followed an in vivo experiment in NSG mice (n=40) engrafted with the JJN3-GFP cell line (1x106) via tail vein and treated by 4 weeks. Analysis of the in vivo imaging and survival curve were obtained. Results The higher expression of factors involved in the mitochondrial function such as: c-Myc, HNRNPK, NRF1 and EF-Tu predict MM poor outcomes (Fig.1A). Furthermore, mitochondrial representative gene and protein expression and activity were found increased in MM relapse stage patients. We showed overexpression of C-Myc, TFAM and EF-Tu on the MM relapsed group (Fig. 1B). Moreover, IHC reveals overexpression of mitochondrial COXII protein in relapse MM patients (p-value ** < 0.001) (Fig. 1C). By functional assays we have demonstrated that gene/protein overexpression drives to an increase of activity (COX HE) in MM at relapse (p-value ***< 0.0001). (Fig. 1D). Moreover, we