Anti-myeloma Activity Research Articles

Inhibition of Glycogen Synthase Kinase-3 Increases NKG2D Ligand MICA Expression and Sensitivity to NK Cell–Mediated Cytotoxicity in Multiple Myeloma Cells: Role of STAT3

Engagement of NKG2D and DNAX accessory molecule-1 (DNAM-1) receptors on lymphocytes plays an important role for anticancer response and represents an interesting therapeutic target for pharmacological modulation. In this study, we investigated the effect of inhibitors targeting the glycogen synthase kinase-3 (GSK3) on the expression of NKG2D and DNAM-1 ligands in multiple myeloma (MM) cells. GSK3 is a pleiotropic serine-threonine kinase point of convergence of numerous cell-signaling pathways, able to regulate the proliferation and survival of cancer cells, including MM. We found that inhibition of GSK3 upregulates both MICA protein surface and mRNA expression in MM cells, with little or no effects on the basal expression of the MICB and DNAM-1 ligand poliovirus receptor/CD155. Moreover, exposure to GSK3 inhibitors renders myeloma cells more efficient to activate NK cell degranulation and to enhance the ability of myeloma cells to trigger NK cell-mediated cytotoxicity. We could exclude that increased expression of β-catenin or activation of the heat shock factor-1 (transcription factors inhibited by active GSK3) is involved in the upregulation of MICA expression, by using RNA interference or viral transduction of constitutive active forms. On the contrary, inhibition of GSK3 correlated with a downregulation of STAT3 activation, a negative regulator of MICA transcription. Both Tyr(705) phosphorylation and binding of STAT3 on MICA promoter are reduced by GSK3 inhibitors; in addition, overexpression of a constitutively active form of STAT3 significantly inhibits MICA upregulation. Thus, we provide evidence that regulation of the NKG2D-ligand MICA expression may represent an additional immune-mediated mechanism supporting the antimyeloma activity of GSK3 inhibitors.

Antiestrogen-binding site ligands induce autophagy in myeloma cells that proceeds through alteration of cholesterol metabolism

Multiple myeloma (MM) is a malignancy characterized by the accumulation of clonal plasma cells in the bone marrow. Despite extensive efforts to design drugs targeting tumoral cells and their microenvironment, MM remains an incurable disease for which new therapeutic strategies are needed. We demonstrated here that antiestrogens (AEs) belonging to selective estrogen receptor modulators family induce a caspase-dependent apoptosis and trigger a protective autophagy. Autophagy was recognized by monodansylcadaverin staining, detection of autophagosomes by electronic microscopy, and detection of the cleaved form of the microtubule-associated protein light chain 3. Moreover, autophagy was inhibited by drugs such as bafilomycin A1 and 3-methyladenosine. Autophagy was mediated by the binding of AEs to a class of receptors called the antiestrogen binding site (AEBS) different from the classical estrogen nuclear receptors. The binding of specific ligands to the AEBS was accompanied by alteration of cholesterol metabolism and in particular accumulation of sterols: zymostenol or desmosterol depending on the ligand. This was due to the inhibition of the cholesterol-5,6-epoxide hydrolase activity borne by the AEBS. We further showed that the phosphoinositide 3-kinase/AKT/mammalian target of rapamycin pathway mediated autophagy signaling. Moreover, AEBS ligands restored sensitivity to dexamethasone in resistant MM cells. Since we showed previously that AEs arrest MM tumor growth in xenografted mice, we propose that AEBS ligands may have a potent antimyeloma activity alone or in combination with drugs used in clinic.

Arsenic Trioxide-Enhanced, Matrine-Induced Apoptosis in Multiple Myeloma Cell Lines

Matrine and arsenic trioxide are monomers used in traditional Chinese medicine possessing anti-myeloma activities. In this study, we evaluated the effects and mechanisms of matrine, arsenic trioxide, and their combination therapy on the proliferation and apoptosis of the myeloma cell lines RPMI8226 and U266. The effects of growth inhibition were measured by MTT, and apoptotic cells were analyzed by Hoechst 33258 staining and flow cytometry. The levels of caspase-3, poly (ADP-ribose) polymerase (a DNA repair enzyme), Bcl-2 and survivin (antiapoptotic signaling proteins), Bim (a proapoptotic signaling protein), total AKT, and phosphorylated AKT were evaluated by Western blot. Matrine significantly inhibited proliferation of RPMI8226 and U266 cell lines in a dose- and time-dependent manner with an IC₅₀ at 24 h of 2.25 g/L and 2.18 g/L, and at 48 h of 1.64 g/L and 1.58 g/L, respectively. Arsenic trioxide also displayed a dose- and time-dependent inhibition of growth of multiple myeloma cell lines, and synergistic effects occurred when the two were combined. Matrine (0.5, 1.0 g/L) and arsenic trioxide (2, 4 ug/mL) induced the apoptosis of myeloma cells; more early-stage apoptotic cells were seen with the combination therapy (matrine 0.5 g/L plus arsenic trioxide 2 ug/mL and matrine 1.0 g/L plus arsenic trioxide 4 ug/mL). Activation of caspase-3 and poly (ADP-ribose) polymerase, upregulation of Bim expression, downregulation of Bcl-2, survivin expression, as well as inhibition of phosphorylated AKT related to matrine (0, 0.25, 0.5, 1.0, and 2.0 g/L)-mediated apoptosis, and the effects were enhanced when arsenic trioxide (8 ug/mL) was combined with matrine (1.0 g/L). In conclusion, matrine displayed anti-myeloma effects through apoptotic induction, and arsenic trioxide had synergistic effects with matrine enhancing matrine-induced apoptosis.

HM1.24/CD317-directed immunotoxin to eliminate malignant plasma cells in vitro and in vivo.

8604 Background: Targeted immunotherapy, based on antibodies against tumor-associated antigens, is a promising approach for the treatment of multiple myeloma (MM). Recently, antibody-based strategies delivering a toxic payload have documented impressive clinical activity in hematological malignancies. In particular, surface molecules overexpressed on malignant plasma cells and efficiently internalized represent promising targets for developing myeloma-directed immunoconstructs. Here, the identification of CD317 (HM1.24) as a potent target structure and the characterization of a novel CD317-directed single-chain immunotoxin, HM1.24-ETA', is described. Methods: Using a novel screening tool, a panel of antibodies against MM-associated antigens was evaluated for their ability to mediate antigen-dependent delivery of a truncated version of Pseudomonas exotoxin A (ETA’) to MM cells. HM1.24-ETA' was generated by genetic fusion of a CD317-specific single-chain Fv antibody and ETA'. The anti-myeloma activity of the E. coli-expressed immunotoxin was evaluated in vitro and in a xenograft mouse model. Results: By screening a panel of antibodies including CD38, CS1, IL-6R, CD138 and CD317, CD317 was identified as a suitable receptor to deliver ETA’ to MM cells. The subsequently designed recombinant HM1.24-ETA' immunotoxin efficiently inhibited growth of MM cell lines with halfmaximal growth inhibition at concentrations of less than 1 nM. Antigen-specific MM cell killing occurred via induction of apoptosis. The proliferation of IL-6 dependent INA-6 cells was completely inhibited by HM1.24-ETA' even in the presence of bone marrow stromal cells that otherwise strongly support tumor cell growth. Importantly, HM1.24-ETA' strongly triggered apoptosis (up to 80%) in freshly isolated tumor cells from 7 out of 7 MM patients. In a xenograft SCID mouse model, establishment of INA-6 plasma cell tumors was efficiently abrogated by treatment with HM1.24-ETA' immunotoxin (p < 0.04). Conclusions: The HM1.24-ETA' immunotoxin in vitro and in the preclinical xenograft model in vivo demonstrates that the CD317 antigen may represent a promising target structure for immunotherapy of MM using immunoconjugates with toxic payloads.

Efficacy and Mechanism-of-Action of a Novel Superagonist Interleukin-15: Interleukin-15 Receptor αSu/Fc Fusion Complex in Syngeneic Murine Models of Multiple Myeloma

ALT-803, a complex of an interleukin (IL)-15 superagonist mutant and a dimeric IL-15 receptor αSu/Fc fusion protein, was found to exhibit significantly stronger in vivo biologic activity on NK and T cells than IL-15. In this study, we show that a single dose of ALT-803, but not IL-15 alone, eliminated well-established 5T33P and MOPC-315P myeloma cells in the bone marrow of tumor-bearing mice. ALT-803 treatment also significantly prolonged survival of myeloma-bearing mice and provided resistance to rechallenge with the same tumor cells through a CD8(+) T-cell-dependent mechanism. ALT-803 treatment stimulated CD8(+) T cells to secrete large amounts of IFN-γ and promoted rapid expansion of CD8(+)CD44(high) memory T cells in vivo. These memory CD8(+) T cells exhibited ALT-803-mediated upregulation of NKG2D (KLRK1) but not PD-1 (PDCD1) or CD25 (IL2RA) on their cell surfaces. ALT-803-activated CD8(+) memory T cells also exhibited nonspecific cytotoxicity against myeloma and other tumor cells in vitro, whereas IFN-γ had no direct effect on myeloma cell growth. ALT-803 lost its antimyeloma activity in tumor-bearing IFN-γ knockout mice but retained the ability to promote CD8(+)CD44(high) memory T-cell proliferation, indicating that ALT-803-mediated stimulation of CD8(+)CD44(high) memory T cells is IFN-γ-independent. Thus, besides well-known IL-15 biologic functions in host immunity, this study shows that IL-15-based ALT-803 could activate CD8(+)CD44(high) memory T cells to acquire a unique innate-like phenotype and secrete IFN-γ for nonspecific tumor cell killing. This unique immunomodulatory property of ALT-803 strongly supports its clinical development as a novel immunotherapeutic agent against cancer and viral infections.

Pomalidomide: a novel drug to treat relapsed and refractory multiple myeloma

Multiple myeloma remains an incurable disease despite the introduction of the immunomodulatory drugs (IMiDs) thalidomide and lenalidomide and the proteasome inhibitor bortezomib that have improved the outcome of patients with both newly diagnosed and relapsed/refractory disease. However, patients who relapse after treatment with these agents or are refractory to them represent an unmet need and highlight the necessity for the development of novel anti-myeloma agents. Pomalidomide is an IMiD, structurally related to thalidomide, with enhanced antiangiogenic, antineoplastic, and anti-inflammatory properties and exhibiting potent anti-myeloma activity in vitro and in vivo. Pomalidomide has shown remarkable activity in patients who were refractory to both bortezomib and lenalidomide in Phase II and III studies. This paper reviews the chemistry and mechanisms of action of pomalidomide as well as all the available data from clinical trials on pomalidomide use in patients with refractory/relapsed multiple myeloma.

Abstract 5469: SAR650984, an anti-CD38 antibody, shows anti-tumor activity in a preclinical model of multiple myeloma.

Abstract Multiple myeloma (MM) is the second most common cancer of the blood and one that is difficult to treat. Although survival has greatly improved over the past decade, MM remains fatal, necessitating development of novel therapies. CD38 is a promising target for antibody therapeutics for the treatment MM and various other hematological malignancies. CD38 is a type II transmembrane glycoprotein with ectozyme activity that has been implicated in Ca2+ mobilization and is found highly expressed on malignant plasma cells of MM. CD38 expression correlates with poor disease prognosis in a subset of hematological malignancies, including MM, where CD38 expression in circulating cells is associated with decreased progression free survival. Previous studies have identified several potential mechanisms of action in the context of anti-myeloma activity, including antibody-dependent cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and pro-apoptotic activity in cancer cell lines. To determine the potential therapeutic value of targeting CD38 in the context of MM, a humanized anti-CD38 antibody, SAR650984, was generated and evaluated for anti-tumor activity. We evaluated anti-tumor activity of SAR650984 in xenograft-based models of multiple myeloma . SAR650984 demonstrated potent anti-tumor activity in NCI-H929 and RPMI-8226 MM xenograft models. These results strongly support continued clinical examination of the therapeutic potential for SAR650984 in the treatment of MM and further demonstrates that targeting CD38 with SAR650984 has potential to impact MM disease. Citation Format: Byron Hann, Ti Cai, Donghui Wang, Yun-Kit Hom, Blake T. Aftab, Tom Martin, Jeffrey Wolf. SAR650984, an anti-CD38 antibody, shows anti-tumor activity in a preclinical model of multiple myeloma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5469. doi:10.1158/1538-7445.AM2013-5469

Synthesis and SAR of Lehualide B: a marine-derived natural product with potent anti-multiple myeloma activity.

We report a concise and convergent laboratory synthesis of the rare marine natural product lehualide B that has led to the discovery that (1) this compound has low nanomolar activity against human multiple myeloma cells and (2) the anticancer effects of lehualide B and its analogues are selective (i.e., they are approximately 2-3 orders of magnitude less toxic to human breast cancer cells). Synthetic lehualide B is shown to be an effective inhibitor of complex I of the mitochondrial electron transport chain, with potency similar to that observed for the terrestrial natural products piericidin A1 and rotenone, an observation that led to the discovery that piericidin A1 is also selectively cytotoxic toward human multiple myeloma cells. Interestingly, synthetic derivatives of lehualide B that resemble verticipyrone (an established complex I inhibitor composed of a γ-pyrone and a simple monounsaturated hydrophobic chain) lack the potent antimyeloma activity of the natural product. Finally, the synthesis and evaluation of a collection of lehualide-inspired analogues led to the elucidation of structure-activity relationships for this rare natural product that established important roles for the substituted γ-pyrone headgroup and the skipped polyene side chain.

A Human ICAM-1 Antibody Isolated by a Function-First Approach Has Potent Macrophage-Dependent Antimyeloma Activity In Vivo

We isolated a tumor B-cell-targeting antibody, BI-505, from a highly diversified human phage-antibody library, using a pioneering "function-first" approach involving screening for (1) specificity for a tumor B cell surface receptor, (2) induction of tumor programmed cell death, and (3) enhanced in vivo antitumor activity compared to currently used treatments. BI-505 bound to intercellular adhesion molecule-1, identifying a previously unrecognized role for this receptor as a therapeutic target in cancer. The BI-505 epitope was strongly expressed on the surface of multiple myeloma cells from both newly diagnosed and relapsed patients. BI-505 had potent macrophage-dependent antimyeloma activity and conferred enhanced survival compared to currently used treatments in advanced experimental models of multiple myeloma.

Arsenic trioxide inhibits the proliferation of myeloma cell line through notch signaling pathway

Arsenic Trioxide (ATO) has shown remarkable efficacy for the treatment of multiple myeloma (MM). However, the mechanism by which ATO exerts its inhibitory effect on the proliferation of myeloma cells remains to be clarified. We study the inhibitory effect of ATO at various concentrations on the proliferation of the myeloma cell line RPMI 8226 and discussed the molecular mechanism of ATO on myeloma cell line. Our results proved that ATO had a significant dose-dependent and time-dependent inhibitory effect on the expressions of the Notch receptor (Notch1) and Notch ligand (Jag2). Data from the real-time PCR assay showed that the mRNA expression levels of the Jag2 gene and its downstream gene Hes1 were both significantly down-regulated after the myeloma cells were treated with ATO while the expression of the tumor suppressor gene PTEN was up-regulated. These results elucidated the molecular mechanism underlying the ATO mediated inhibition of myeloma cell proliferation. This is the first report on the anti-myeloma activity in myeloma cells through inhibition of the Notch signaling pathway.

Nelfinavir augments proteasome inhibition by bortezomib in myeloma cells and overcomes bortezomib and carfilzomib resistance

HIV protease inhibitors (HIV-PI) are oral drugs for HIV treatment. HIV-PI have antitumor activity via induction of ER-stress, inhibition of phospho-AKT (p-AKT) and the proteasome, suggesting antimyeloma activity. We characterize the effects of all approved HIV-PI on myeloma cells. HIV-PI were compared regarding cytotoxicity, proteasome activity, ER-stress induction and AKT phosphorylation using myeloma cells in vitro. Nelfinavir is the HIV-PI with highest cytotoxic activity against primary myeloma cells and with an IC50 near therapeutic drug blood levels (8–14 μM), irrespective of bortezomib sensitivity. Only nelfinavir inhibited intracellular proteasome activity in situ at drug concentrations <40 μℳ. Ritonavir, saquinavir and lopinavir inhibited p-AKT comparable to nelfinavir, and showed similar synergistic cytotoxicity with bortezomib against bortezomib-sensitive cells. Nelfinavir had superior synergistic activity with bortezomib/carfilzomib in particular against bortezomib/carfilzomib-resistant myeloma cells. It inhibited not only the proteasomal β1/β5 active sites, similar to bortezomib/carfilzomib, but in addition the β2 proteasome activity not targeted by bortezomib/carfilzomib. Additional inhibition of β2 proteasome activity is known to sensitize cells for bortezomib and carfilzomib. Nelfinavir has unique proteasome inhibiting activity in particular on the bortezomib/carfilzomib-insensitive tryptic (β2) proteasome activity in intact myeloma cells, and is active against bortezomib/carfilzomib-resistant myeloma cells in vitro.

Induction of apoptosis in multiple myeloma cells by a statin–thalidomide combination can be enhanced by p38 MAPK inhibition

The mechanisms involved in anti-myeloma activity of statins combined with thalidomide were studied in multiple myeloma (MM) cells. In addition, the effect of p38 MAPK inhibition on the induction of apoptosis in MM cells by the combination of thalidomide and simvastatin was investigated. Thalidomide was observed to significantly potentiate the antiproliferative activity of statins and enhance the proapoptotic effect of simvastatin and lovastatin. What is more, the combination of thalidomide with statins inhibited cell migration and decreased the production of VEGF and MMP-9 in MM cells more effectively than each of these drugs used separately. The combination of simvastatin and thalidomide augmented caspase 8 and 3 activation, and the additional application of p38 MAPK inhibitor resulted in enhanced apoptosis of MM cells concomitant with increased caspase 9 and 3 activation, as well as JNK phosphorylation. The results suggest that p38 inhibitors together with the combination of simvastatin and thalidomide have the potential to be used in MM treatment.

Age matters: Young T lymphocytes offer better protection from myeloma proliferation.

BackgroundThe incidence and growth of cancer has been reported to increase with age and/or impaired T lymphocyte function.ResultsConsistent with these observations, we found that a monoclonal serum immunoglobulin (mIgG2b), rarely detectable after the injection of 5T33 murine multiple myeloma (MMM) cells into 3–4 month old wild-type C57BL/6 mice was seen more frequently in 18–20 month old wild-type C57BL/6 mice and in 3–4 month old Rag1-deficient C57BL/6 mice. These observations were confirmed and extended using more sensitive assays such as quantitation of splenic mRNA specific for the canonical 5T33 monoclonal IgG2b produced by 5T33 myeloma cells and the most sensitive assay, photon-imaging of mice injected with 5T33 cells, stably transfected with fire-fly luciferase gene (5T33L cells), which emit photons after the injection of luciferin. Furthermore, the proliferation of 5T33L myeloma cells in Rag1-deficient C57BL/6 mice was greater in mice which also received spleen T cells from 18–20 month old C57BL/6 wild-type mice compared to mice which received splenic T cells from 3–4 month old C57BL/6 wild-type mice. Thus, immune reconstitution of C57BL/6 mice with splenic T cells from young wild-type mice offered greater protection from progressive growth of 5T33L myeloma cells than did reconstitution with splenic T cells from old mice.ConclusionsOur findings support the hypothesis that age-associated changes in splenic T cell function contribute to the increased growth of 5T33 MMM cells in old compared to young C57BL/6 mice. Should similar processes occur in humans, increasing the anti-myeloma activity of T cells in old patients with multiple myeloma or transferring cryopreserved, young, autologous, T cells might benefit elderly patients with multiple myeloma.

Proteasome Inhibitors in Treatment of Multiple Myeloma

Multiple myeloma, a plasma cell malignancy, still remains a hard-to-treat hematological disease that desperately needs new therapy targeting plasmocytes but also the bone marrow microenvironment. Clonal plasmocytes are characterized by increased regulation of ubiquitin-proteasome pathway which augments their sensitivity to proteasome inhibitors. Treatment strategies based on proteasome inhibitors belong to the era of new drugs, and they have become increasingly important for treatment of multiple myeloma in recent years. Bortezomib became the first proteasome inhibitor approved for the treatment of multiple myeloma and showed remarkable anti-myeloma activity. However, despite its high efficiency, a large proportion of patients have became bortezomib resistant. The second generation of proteasome inhibitors - carfilzomib, marizomib and MLN9708 - were developed in an effort to overcome bortezomib-resistance and find proteasome inhibitors with a better toxic profile. These drugs brought a chance that multiple myeloma would become a chronic disease.

An integrin-targeted, pan-isoform, phosphoinositide-3 kinase inhibitor, SF1126, has activity against multiple myeloma in vivo

Multiple reports point to an important role for the phosphoinositide-3 kinase (PI3K) and AKT signaling pathways in tumor survival and chemoresistance in multiple myeloma (MM). The goals of our study were: (1) to generate the preclinical results necessary to justify a Phase I clinical trial of SF1126 in hematopoietic malignancies including MM and (2) to begin combining pan-PI3K inhibitors with other agents to augment antitumor activity of this class of agent in preparation for combination therapy in Phase I/II trials. We determined the in vitro activity of SF1126 with 16 human MM cell lines. In vivo tumor growth suppression was determined with human myeloma (MM.1R) xenografts in athymic mice. In addition, we provide evidence that SF1126 has pharmacodynamic activity in the treatment of patients with MM. SF1126 was cytotoxic to all tested MM lines, and potency was augmented by the addition of bortezomib. SF1126 affected MM.1R cell line signaling in vitro, inhibiting phospho-AKT, phospho-ERK, and the hypoxic stabilization of HIF1α. Tumor growth was 94 % inhibited, with a marked decrease in both cellular proliferation (PCNA immunostaining) and angiogenesis (tumor microvessel density via CD31 immunostaining). Our clinical results demonstrate pharmacodynamic knockdown of p-AKT in primary patient-derived MM tumor cells in vivo. Our results establish three important points: (1) SF1126, a pan-PI3K inhibitor has potent antitumor activity against MM in vitro and in vivo, (2) SF1126 displays augmented antimyeloma activity when combined with proteasome inhibitor, bortezomib/Velcade(®), and (3) SF1126 blocks the IGF-1-induced activation of AKT in primary MM tumor cells isolated from SF1126-treated patients The results support the ongoing early Phase I clinical trial in MM and suggest a future Phase I trial in combination with bortezomib in hematopoietic malignancies.

Lymphocytopenia is associated with an increased risk of severe infections in patients with multiple myeloma treated with bortezomib-based regimens

Bortezomib is a proteasome inhibitor with potent antimyeloma activity in relapsed/refractory multiple myeloma (MM) patients. We evaluated the types and factors affecting the onset of infectious complications and mortality owing to infection in MM patients treated with bortezomib-based regimens. We reviewed 139 patients with MM treated with regimens containing bortezomib in order to assess the types and factors affecting the development of severe infections. Infections occurred in 56 (40.3 %) of 139 patients and 83 (7.8 %) cases of the 1,069 evaluable cycles. Severe infections developed in 43 (30.9 %) patients and ten patients (7.1 %) died during bortezomib-based treatment. Multivariate analysis determined lymphocytopenia grade 3-4 (OR 3.17, 95 % CI 1.38-7.31, P = 0.007) and number of cycles ≤ 8 (OR 3.91, 95 % CI 1.39-11.02, P = 0.010) as risk factors associated with increased severe infection. This study showed that MM patients who received bortezomib-based regimens are at a higher risk of severe infections within eight cycles of treatment during especially severe lymphocytopenic periods. MM patients treated with bortezomib-based regimens should be closely monitored for the development of infectious complications during lymphocytopenia.

In vivo and in vitro effects of a novel anti-Dkk1 neutralizing antibody in multiple myeloma

Over-expression of the protein Dickkopf-1 (Dkk1) has been associated with multiple myeloma bone disease. Previous reports with the use of anti-Dkk1 neutralizing Ab directed strategies have demonstrated a pro-anabolic effect with associated anti-myeloma activity in 2 in vivo mouse models. However new insights on the role of the wnt pathway in osteoclasts (OC) are emerging and the potential effect of a neutralizing Ab to Dkk1 in osteoclastogenesis remains to be elucidated. In order to better define the effect of an anti-Dkk1 neutralizing Ab on osteoclastogenesis and myeloma, we studied a novel anti-Dkk1 monoclonal Ab in our preclinical models. In vivo data confirmed the pro-anabolic and anti-MM effect. In vitro data in part confirmed the in vivo observation, suggesting an indirect anti-MM effect secondary to inhibition of osteoclastogenesis and thus the interaction between MM and bone microenvironment. However, when studies on osteoclastogenesis were extended to samples derived from MM patients, we observed a variable response to anti-Dkk1 treatment without correlation to expression of surface receptors for Dkk1 in OCs suggesting potential heterogeneity in the efficacy of such a strategy. In conclusion, Dkk1 is a promising target for the treatment of both MM and bone disease, and ongoing clinical studies will help elucidate its efficacy.

The PI3K inhibitor GDC-0941 combines with existing clinical regimens for superior activity in multiple myeloma

The phosphatidylinositol 3'-kinase (PI3K) pathway is dysregulated in multiple myeloma (MM); we therefore tested a highly selective class I PI3K inhibitor, GDC-0941, for anti-myeloma activity. Functional and mechanistic studies were first performed in MM cell lines, then extended to primary MM patient samples cultured in vitro. GDC-0941 was then assessed as a single agent and in various combinations in myeloma tumor xenograft models. We show p110 α and β are the predominant PI3K catalytic subunits in MM and that a highly selective class I PI3K inhibitor, GDC-0941, has robust activity as a single agent to induce cell cycle arrest and apoptosis of both MM cell lines and patient myeloma cells. Mechanistic studies revealed an induction of cell cycle arrest at G0/G1, with decreased phospho-FoxO1/3a levels, decreased cyclin D1 and c-myc expression, and an increase in the cell cycle inhibitor, p27kip. Induction of apoptosis correlated with increased expression of the pro-apoptotic BH3-only protein BIM, cleaved caspase 3 and cleaved poly (ADP-ribose) polymerase (PARP). In vitro, GDC-0941 synergized with dexamethasone (Dex) and lenalidomide (combination index values of 0.3-0.4 and 0.4-0.8, respectively); in vivo GDC-0941 has anti-myeloma activity and significantly increases the activity of the standard of care agents in several murine xenograft tumor models (additional tumor growth inhibition of 37-53% (Dex) and 22-72% (lenalidomide)). These data provide a clear therapeutic hypothesis for the inhibition of PI3K and provide a rationale for clinical development of GDC-0941 in myeloma.

Retrospective analysis on therapeutic effect of autologous hematopoietic stem cell transplantation in multiple myeloma patients

To evaluate the efficacy and prognostic factors of autologous hematopoietic stem cell transplantation (ASCT) in multiple myeloma (MM) patients. Retrospective analysis was performed in 27 MM patients undergoing ASCT at our hospital from May 2004 to August 2011. After comparing with 28 patients achieving very good partial response (VGPR) or better outcome and not undergoing ASCT, the impact on the extent of response, progression-free survival (PFS) and overall survival (OS) as well as related prognostic factors of MM patients were analyzed. All patients successfully underwent hematopoietic reconstruction without transplantation-related mortality. The complete remission (CR) rate of ASCT group increased from 25.9% (7/27) at pre-ASCT to 70.4% (19/27) at post-ASCT (P < 0.01). The estimated 5-year rate of progression-free survival was 56.2% (median not reached) in the ASCT group and 24.9% (median 29 months) in the non-ASCT group (P < 0.05). The 5-year probability of overall survival was 52.2% (median not reached) in the ASCT group and 33.1% (median 60 months) in the non-ASCT group (P > 0.05). Univariate analysis in ASCT group demonstrated that maintenance/consolidation therapy was associated with PFS (P = 0.010) and OS (P = 0.008).Patients on induction therapy containing bortezomib and early ASCT maintenance therapy all survived without disease progression until final follow-up (P = 0.010). ASCT can further increase the CR rate, prolong PFS and probably OS. The incorporation of novel agents into induction, consolidation and maintenance phases has optimized the anti-myeloma activity of ASCT and may be important for improved long-term outcomes.

Inhibition of Glycogen Synthase Kinase-3 increases NKG2D Ligand MICA expression and sensitivity to NK cell-mediated cytotoxicity in Multiple Myeloma cells: role of STAT3.

Event Abstract Back to Event Inhibition of Glycogen Synthase Kinase-3 increases NKG2D Ligand MICA expression and sensitivity to NK cell-mediated cytotoxicity in Multiple Myeloma cells: role of STAT3. Cinzia Fionda1*, Giulia Malgarini1, Alessandra Soriani1, Alessandra Zingoni1, Francesca Cecere1, Marialuisa Iannitto1, Maria Rosaria Ricciardi2, Maria Teresa Petrucci2, Angela Santoni1 and Marco Cippitelli1 1 University of Rome "Sapienza", Department of Molecular Medicine, Italy 2 Sapienza, Department of Ematology, Italy Engagement of NKG2D and DNAM-1 receptors with their ligands on lymphocytes plays an important role for anticancer response and represents an interesting therapeutic target for pharmacological modulation. In this study, we investigated the effect of inhibitors targeting the Glycogen Synthase Kinase-3 (GSK3) on the expression of NKG2D and DNAM-1 ligands in human MM (Multiple Myeloma) cells. GSK3 is a serine-threonine kinase point of convergence of numerous cell-signaling pathways, able to regulate the proliferation and survival of cancer cells, including MM. We found that inhibition of GSK3 is able to up-regulate MICA protein surface, mRNA expression and promoter activity in MM cells without significant effects on the expression of MICB and DNAM-1 ligand PVR/CD155. Moreover, exposure to GSK-3 inhibitors renders myeloma cells more efficient to activate NK cell degranulation and trigger NK cell-mediated cytotoxicity. We could exclude that two transcription factors specifically inhibited by active GSK3, β-catenin or Heat Shock Factor-1 (HSF-1), are involved in the up-regulation of MICA expression by using RNA-interference or viral transduction of constitutive active forms. On the contrary, inhibition of GSK3 correlated with a significant downregulation of STAT3 activation, a negative regulator of MICA transcription. Both Tyr705 phosphorylation and in vivo binding of STAT3 on MICA promoter are reduced by drugs targeting GSK3; in addition, overexpression of a constitutively active form of STAT3 significantly inhibits MICA upregulation. Thus, we provide evidence that regulation of the NKG2D-ligand MICA expression may represent an additional mechanism supporting the anti-myeloma activity of GSK3 inhibitors, and suggest their possible immunotherapeutic value. Keywords: NKG2D ligands, ; GSK3, Multiple Myeloma, NK, STAT3 Transcription Factor Conference: 15th International Congress of Immunology (ICI), Milan, Italy, 22 Aug - 27 Aug, 2013. Presentation Type: Abstract Topic: Innate immunity Citation: Fionda C, Malgarini G, Soriani A, Zingoni A, Cecere F, Iannitto M, Ricciardi M, Petrucci M, Santoni A and Cippitelli M (2013). Inhibition of Glycogen Synthase Kinase-3 increases NKG2D Ligand MICA expression and sensitivity to NK cell-mediated cytotoxicity in Multiple Myeloma cells: role of STAT3.. Front. Immunol. Conference Abstract: 15th International Congress of Immunology (ICI). doi: 10.3389/conf.fimmu.2013.02.00214 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 12 Mar 2013; Published Online: 22 Aug 2013. * Correspondence: Dr. Cinzia Fionda, University of Rome "Sapienza", Department of Molecular Medicine, Rome, 00161, Italy, cinzia.fionda@uniroma1.it Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Cinzia Fionda Giulia Malgarini Alessandra Soriani Alessandra Zingoni Francesca Cecere Marialuisa Iannitto Maria Rosaria Ricciardi Maria Teresa Petrucci Angela Santoni Marco Cippitelli Google Cinzia Fionda Giulia Malgarini Alessandra Soriani Alessandra Zingoni Francesca Cecere Marialuisa Iannitto Maria Rosaria Ricciardi Maria Teresa Petrucci Angela Santoni Marco Cippitelli Google Scholar Cinzia Fionda Giulia Malgarini Alessandra Soriani Alessandra Zingoni Francesca Cecere Marialuisa Iannitto Maria Rosaria Ricciardi Maria Teresa Petrucci Angela Santoni Marco Cippitelli PubMed Cinzia Fionda Giulia Malgarini Alessandra Soriani Alessandra Zingoni Francesca Cecere Marialuisa Iannitto Maria Rosaria Ricciardi Maria Teresa Petrucci Angela Santoni Marco Cippitelli Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. 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