Although new therapies have doubled the survival of multiple myeloma (MM) patients, this remains an incurable disease. It has been postulated that the so-called MM Cancer Stem Cells (MM-CSC) would be responsible for tumor initiation and relapse but their unequivocal identification remains unclear. Here, we investigated in a panel of MM cell lines the presence of CD20+ cells harboring a MM-CSC phenotype. Among the multiple cell lines investigated, only a small population of CD20dim+ cells (0.3%) in the RPMI-8226 cell line was found. CD20dim+ RPMI-8226 cells expressed the plasma cell markers CD38 and CD138 and were CD19-CD27-. Additionally, CD20dim+ RPMI-8226 cells did not exhibit stem-cell markers as shown by gene expression profiling and the aldehyde dehydrogenase (ALDH) assay. Moreover, we demonstrated that CD20dim+ RPMI-8226 cells are not essential for CB17-SCID mice engraftment and show lower self-renewal potential than the CD20- RPMI-8226 cells. These results do not support CD20+ expression for the identification of MM-CSC.
CD20 positive cells are undetectable in the majority of multiple myeloma cell lines and are not associated with a cancer stem cell phenotype.
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View SamplesDespite recent advances in the treatment of multiple myeloma (MM), it remains an incurable disease potentially due to the presence of resistant myeloma cancer stem cells (MM-CSC). Although the presence of clonogenic cells in MM was described more than 30 years ago, the phenotype of MM-CSC is still a matter of debate, especially with respect to the expression of syndecan- 1 (CD138). Here, we demonstrate the presence of two subpopulations - CD138++ (95-99%) and CD138low (1-5%) - in eight MM cell lines. To find out possible stem-cell-like features, we have phenotypically, genomic and functionally characterized the two subpopulations. Our results show that the minor CD138low subpopulation is morphologically identical to the CD138++ fraction and does not represent a more immature B-cell compartment (with lack of CD19, CD20 and CD27 surface expression). Moreover, both subpopulations have similar gene expression and genomic profiles. Importantly, both CD138++ and CD138low subpopulations have similar sensitivity to bortezomib, melphalan and doxorubicin. Finally, serial engraftment in SCID mice shows that CD138++ as well as CD138low cells have self-renewal potential and they are also phenotypically interconvertible. Overall, our results differ from previously published data which attribute a B-cell phenotype to MM-CSC and urge the need to explore more reliable markers to discriminate true clonogenic myeloma cells.
Phenotypic, genomic and functional characterization reveals no differences between CD138++ and CD138low subpopulations in multiple myeloma cell lines.
Disease, Cell line
View SamplesMicroRNAs have been demonstrated to be deregulated in multiple myeloma (MM). We have previously reported the downregulation of miR-214 in MM compared to normal plasma cells. In the present study, we have explored the functional role of miR-214 in myeloma pathogenesis. Ectopic expression of miR-214 reduced cell growth and induced apoptosis of myeloma cells. In order to identify the potential direct target genes of miR-214 which could be involved in the biological pathways regulated by this miRNA, gene expression profiling of H929 myeloma cell line transfected with precursor miR-214 was carried out. Functional analysis revealed significant enrichment for DNA replication, cell cycle phase and DNA binding. We show that miR-214 directly down-regulates the expression of PSMD10, which encodes the oncoprotein gankyrin, and ASF1B, a histone chaperone required for DNA replication, by binding to their 3'-UTR. In addition, gankyrin inhibition induced an increase of P53 mRNA levels and subsequent up-regulation in CDKN1A (p21Waf1/Cip1) and BAX transcripts, which are direct transcriptional targets of p53. In conclusion, we demonstrate that miR-214 function as a tumor suppressor in myeloma by a positive regulation of p53 and inhibition of DNA replication.
Restoration of microRNA-214 expression reduces growth of myeloma cells through positive regulation of P53 and inhibition of DNA replication.
Cell line
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The kinesin spindle protein inhibitor filanesib enhances the activity of pomalidomide and dexamethasone in multiple myeloma.
Specimen part, Cell line, Treatment
View SamplesKinesin spindle protein (KSP) inhibition is known to be an effective therapeutic approach in several malignancies. Filanesib (Arry-520), a KSP inhibitor, has demonstrated activity in heavily pretreated multiple myeloma (MM) patients. The aim of this work was to investigate the activity of filanesib in combination with an IMiDs plus dexamethasone backbone, and the mechanisms underlying the potential synergistic effect. Results: Filanesib showed in vitro and in vivo synergy with all IMiDs plus dexamethasone treatment, particularly with the pomalidomide combination (PDF). Importantly, the in vivo synergy observed in this combination was more evident in large, highly proliferative tumors, and it was shown to be mediated by impairment of mitosis transcriptional control, an increase in monopolar spindles, cell cycle arrest and the induction of apoptosis in cells in proliferative phases. In addition, PDF increased the activation of the proapoptotic protein Bax, which has been previously associated with sensitivity to filanesib, and could potentially be used as a predictive biomarker of response to this combination. Conclusions: Our results provide preclinical evidence for the potential benefit of the combination of filanesib with pomalidomide and dexamethasone and es-tablished the basis for a recently activated trial being conducted by the Spanish MM group investigating this combination in relapsed MM patients.
The kinesin spindle protein inhibitor filanesib enhances the activity of pomalidomide and dexamethasone in multiple myeloma.
Specimen part, Treatment
View SamplesKinesin spindle protein (KSP) inhibition is known to be an effective therapeutic approach in several malignancies. Filanesib (Arry-520), a KSP inhibitor, has demonstrated activity in heavily pretreated multiple myeloma (MM) patients. The aim of this work was to investigate the activity of filanesib in combination with an IMiDs plus dexamethasone backbone, and the mechanisms underlying the potential synergistic effect. Results: Filanesib showed in vitro and in vivo synergy with all IMiDs plus dexamethasone treatment, particularly with the pomalidomide combination (PDF). Importantly, the in vivo synergy observed in this combination was more evident in large, highly proliferative tumors, and it was shown to be mediated by impairment of mitosis transcriptional control, an increase in monopolar spindles, cell cycle arrest and the induction of apoptosis in cells in proliferative phases. In addition, PDF increased the activation of the proapoptotic protein Bax, which has been previously associated with sensitivity to filanesib, and could potentially be used as a predictive biomarker of response to this combination. Conclusions: Our results provide preclinical evidence for the potential benefit of the combination of filanesib with pomalidomide and dexamethasone and es-tablished the basis for a recently activated trial being conducted by the Spanish MM group investigating this combination in relapsed MM patients.
The kinesin spindle protein inhibitor filanesib enhances the activity of pomalidomide and dexamethasone in multiple myeloma.
Cell line, Treatment
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