Bortezomib-Resistant Nuclear Factor B Activity in Multiple Myeloma Cells

Department of Pharmacology, University of Wisconsin, Madison, WI 53706, USA.
Molecular Cancer Research (Impact Factor: 4.38). 08/2008; 6(8):1356-1364. DOI: 10.1158/1541-7786.MCR-08-0108


Bortezomib (Velcade/PS341), a proteasome inhibitor used in the treatment of multiple myeloma (MM), can inhibit activation of nuclear factor-kappaB (NF-kappaB), a family of transcription factors often deregulated and constitutively activated in primary MM cells. NF-kappaB can be activated via several distinct mechanisms, including the proteasome inhibitor-resistant (PIR) pathway. It remains unknown what fraction of primary MM cells harbor constitutive NF-kappaB activity maintained by proteasome-dependent mechanisms. Here, we report an unexpected finding that constitutive NF-kappaB activity in 10 of 14 primary MM samples analyzed is refractory to inhibition by bortezomib. Moreover, when MM cells were cocultured with MM patient-derived bone marrow stromal cells (BMSC), microenvironment components critical for MM growth and survival, further increases in NF-kappaB activity were observed that were also refractory to bortezomib. Similarly, MM-BMSCs caused PIR NF-kappaB activation in the RPMI8226 MM cell line, leading to increased NF-kappaB-dependent transcription and resistance to bortezomib-induced apoptosis. Our findings show that primary MM cells frequently harbor PIR NF-kappaB activity that is further enhanced by the presence of patient-derived BMSCs. They also suggest that this activity is likely relevant to the drug resistance development in some patients. Further elucidation of the mechanism of PIR NF-kappaB regulation could lead to the identification of novel diagnostic biomarkers and/or therapeutic targets for MM treatment.

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Available from: Shigeki Miyamoto, Jun 25, 2015
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    • "The biological mechanisms underlying primary or acquired bortezomib resistance are not known although the development of structural variants in the β5-subunit of the 20S proteasome core has been cited [27]. Previously our group has demonstrated that a subset of primary MM cells isolated from patient bone marrow samples display enhanced constitutive NF-κB activity when exposed to bortezomib and such activation in MM cell lines correlated with bortezomib-resistance in vitro [28]. We therefore sought to evaluate in a subset of patients receiving treatment on this trial whether we could correlate clinical response with this phenomenon. "
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    ABSTRACT: Purpose Retreatment with bortezomib (B) is often considered for patients with relapsed multiple myeloma (MM), but this strategy is hindered by uncertainty of response and emergence of B-induced peripheral neuropathy (PN). We incorporated acetyl-l-carnitine (ALCAR) to prevent PN and allow for adequate dosing. We also investigated the correlation between B-inducible NF-κB activation and response to therapy. Methods Nineteen patients with relapsed/refractory MM received up to 8 cycles of intravenous bortezomib, doxorubicin and oral low-dose dexamethasone (BDD) to evaluate response and toxicity. Thirteen additional patients received prophylactic ALCAR (BDD-A). Patients receiving BDD-A were evaluated by FACT-GOG-TX, FACIT-Fatigue, Neuropathic Pain index (NPI) and Grooved Pegboard (GP) testing. Primary MM cells from 11 patients were tested for B-inducible NF-κB activation. Results Seventy-six percent of subjects were refractory to previous treatment, 39 % refractory to bortezomib. Median cycles received were 5. CR + PR for the entire group were 53 % and did not differ between groups. Incidence of ≥3 PN was 32 % in the BDD group versus 15 % in the BDD-A group (p = ns). Patient-reported fatigue and PN measured by FACT-GOG-TX increased throughout the treatment period in the BDD-A group, although time to complete GP testing declined. In a sub-study examining constitutive bortezomib-inducible NF-κB activity in primary subject-specific MM cells, the presence of NF-κB activation correlated with lower likelihood of response. Conclusions Addition of ALCAR to BDD did not alter the incidence or severity of PN in relapsed MM patients receiving a B-based regimen. Bortezomib-inducible NF-κB activation in patient-derived primary MM cells may be associated with poorer response.
    Cancer Chemotherapy and Pharmacology 08/2014; 74(4). DOI:10.1007/s00280-014-2550-5 · 2.77 Impact Factor
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    • "NF-κB is an important mediator in the activation of IL-6. Moreover, it has been reported that NF-κB activation has a crucial role in the regulation of bortezomib response to MM cells (10, 14, 15). Interestingly, U266 cells that were treated with a low dose of bortezomib (2 nM) on an intermittent schedule showed gradually increased expressions of p-ERK and p-p65, which are involved in NF-κB pathway. "
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    ABSTRACT: Bortezomib has been known as the most promising anti-cancer drug for multiple myeloma (MM). However, recent studies reported that not all MM patients respond to bortezomib. To overcome such a stumbling-block, studies are needed to clarify the mechanisms of bortezomib resistance. In this study, we established a bortezomib-resistant cell line (U266/velR) and explored its biological characteristics. The U266/velR showed reduced sensitivity to bortezomib, and also showed cross-resistance to the chemically unrelated drug thalidomide. U266/velR cells had a higher proportion of CD138 negative subpopulation, known as stem-like feature, compared to parental U266 cells. U266/velR showed relatively less inhibitory effect of prosurvival NF-κB signaling by bortezomib. Further analysis of RNA microarray identified genes related to ubiquitination that were differentially regulated in U266/velR. Moreover, expression level of CD52 in U266 cells was associated with bortezomib response. Our findings provide basis for developing therapeutic strategies in bortezomib-resistant relapsed and refractory MM patients.
    BMB reports 12/2013; 47(5). DOI:10.5483/BMBRep.2014.47.5.134 · 2.60 Impact Factor
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    • "These are well known for cell proliferation related to cell cycle progression and antiapoptosis. NF-í µí¼…B is known to be correlated with drug-resistant activity [24] and to be a major signaling pathway associated with multiple myeloma pathogenesis. Previous reports showed that not only multiple myeloma cells but also BMSCs adherent to multiple myeloma cells also release IL-6 via NFí µí¼…B pathway to support MM cell growth [25]. "
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    ABSTRACT: IL-6 and TNF α were significantly increased in the bone marrow aspirate samples of patients with active multiple myeloma (MM) compared to those of normal controls. Furthermore, MM patients with advanced aggressive disease had significantly higher levels of IL-6 and TNF α than those with MM in plateau phase. TNF α increased interleukin-6 (IL-6) production from MM cells. However, the detailed mechanisms involved in signaling pathways by which TNF α promotes IL-6 secretion from MM cells are largely unknown. In our study, we found that TNF α treatments induce MEK and AKT phosphorylation. TNF α -stimulated IL-6 production was abolished by inhibition of JAK2 and IKK β or by small interfering RNA (siRNA) targeting TNF receptors (TNFR) but not by MEK, p38, and PI3K inhibitors. Also, TNF α increased phosphorylation of STAT3 (ser727) including c-Myc and cyclin D1. Three different types of JAK inhibitors decreased the activation of the previously mentioned pathways. In conclusion, blockage of JAK/STAT-mediated NF- κ B activation was highly effective in controlling the growth of MM cells and, consequently, an inhibitor of TNF α -mediated IL-6 secretion would be a potential new therapeutic agent for patients with multiple myeloma.
    BioMed Research International 09/2013; 2013:580135. DOI:10.1155/2013/580135 · 1.58 Impact Factor
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