Roger Pearse

Multiple myeloma disrupts the TRANCE/ osteoprotegerin cytokine axis to trigger bone destruction and promote tumor progression

Bone destruction, caused by aberrant production and activation of osteoclasts, is a prominent feature of multiple myeloma. We demonstrate that myeloma stimulates osteoclastogenesis by triggering a coordinated increase in the tumor necrosis factor-related activation-induced cytokine (TRANCE) and decrease in its decoy receptor, osteoprotegerin (OPG). Immunohistochemistry and in situ hybridization studies of bone marrow specimens indicate that in vivo, deregulation of the TRANCE–OPG cytokine axis occurs in myeloma, but not in the limited plasma cell disorder monoclonal gammopathy of unknown significance or in nonmyeloma hematologic malignancies. In coculture, myeloma cell lines stimulate expression of TRANCE and inhibit expression of OPG by stromal cells. Osteoclastogenesis, the functional consequence of increased TRANCE expression, is counteracted by addition of a recombinant TRANCE inhibitor, RANK-Fc, to marrow/myeloma cocultures. Myeloma–stroma interaction also has been postulated to support progression of the malignant clone. In the SCID-hu murine model of human myeloma, administration of RANK-Fc both prevents myeloma-induced bone destruction and interferes with myeloma progression. Our data identify TRANCE and OPG as key cytokines whose deregulation promotes bone destruction and supports myeloma growth.

SHIP Modulates Immune Receptor Responses by Regulating Membrane Association of Btk

Membrane recruitment of SHIP is responsible for the inhibitory signal generated by FcgammaRIIB coligation to the BCR. By reducing the level of PIP3, SHIP regulates the association of the tyrosine kinase Btk with the membrane through PH domain-phosphoinositol lipid interactions. Inhibition of BCR signaling by either FcgammaRIIB coligation, membrane expression of SHIP, or inhibition of P13K, conditions which result in decreased levels of PIP3, is suppressed by the expression of Btk as a membrane-associated chimera. Conversely, increasing PIP3 levels by deletion of SHIP results in increased Btk association with the membrane and hyperresponsive BCR signaling. These results suggest a central role for PIP3 in regulating the B cell stimulatory state by modulating Btk localization and thereby calcium fluxes.

Myeloma interacts with the bone marrow microenvironment to induce osteoclastogenesis and is dependent on osteoclast activity.

Summary. Myeloma tumour growth, except in the most advanced stages of the disease, is restricted to the bone marrow. We used the severe combined immunodeficient‐human (SCID‐hu) host system, in which primary human myeloma cells grow in, disseminate to and interact with a human microenvironment, to study the interactions between myeloma cells and cells in the bone marrow microenvironment. We used inhibitors of osteoclast activity to determine the role of osteoclasts and their products in supporting myeloma cell growth. Treatment of myelomatous SCID‐hu hosts with an inhibitor of osteoclast activity (pamidronate or zoledronate) or with a specific inhibitor of the receptor activator of NF‐κB ligand (RANKL) halted myeloma‐induced bone resorption, when present, and resulted in inhibition of myeloma cell growth and survival. In contrast, myeloma cells from patients with extramedullary disease had a different growth pattern in the SCID‐hu hosts and were not inhibited by these interventions, indicating that, while still dependent on a human microenvironment, these cells no longer required the bone marrow microenvironment for survival. This study demonstrates the dependence of myeloma cells on osteoclast activity and their products, and highlights the importance of the myeloma–osteoclast–myeloma loop for sustaining the disease process. Breaking this loop may help control myeloma.

SHIP Recruitment Attenuates FcγRIIB-Induced B Cell Apoptosis

Abstract FcγRIIB is an inhibitory receptor that terminates activation signals initiated by antigen cross-linking of the BCR through the recruitment of SHIP. FcγRIIB can also signal independently of BCR coligation to directly mediate an apoptotic response, requiring only an intact transmembrane domain. Failure to recruit SHIP, either by deletion of SHIP or mutation of FcγRIIB, results in enhanced FcγRIIB-triggered apoptosis. Thus, in the germinal center, where ICs are retained by FDCs, FcγRIIB may be an active determinant in the negative selection of B cells whose BCRs have reduced affinity for antigen as a result of somatic hypermutation. Selection of B cells may represent the sum of opposing signals generated by the interaction of ICs with the BCR and FcγRIIB through pathways modulated by SHIP.

RANK‐Fc: A therapeutic antagonist for RANK‐L in myeloma

Severe bone destruction due to inappropriate osteoclastogenesis is a prominent feature of multiple myeloma (MM). MM increases bone loss by disrupting the checks that normally control signaling by receptor activator of nuclear factor κB ligand (RANK‐L, also called TRANCE [tumor necrosis factor‐related, activation‐induced cytokine], osteoprotegerin ligand [OPG‐L], osteoclast differentiation factor [ODF], and tumor necrosis factor superfamily member 11 [TNFSF11]), a TNF‐family cytokine required for osteoclast differentiation and activation. RANK‐L binds to its functional receptor RANK (TNF receptor superfamily member 11a [TNF RSF11a]) to stimulate osteoclastogenesis. Osteotropic cytokines regulate this process by controlling bone marrow stromal expression of RANK‐L. Further control over osteoclastogenesis is maintained by regulated expression of osteoprotegerin (OPG, also called osteoclastogenesis inhibitory factor and TNFRSF11b), a soluble decoy receptor for RANK‐L. In normal bone marrow, abundant stores of OPG in stroma, megakaryocytes, and myeloid cells provide a natural buffer against increased RANK‐L. MM disrupts these controls by increasing expression of RANK‐L and decreasing expression of OPG. Concurrent deregulation of RANK‐L and OPG expression is found in bone marrow biopsies from patients with MM but not in specimens from patients with non‐MM hematologic malignancies.

Stem Cell Mobilization with Cyclophosphamide Overcomes the Suppressive Effect of Lenalidomide Therapy on Stem Cell Collection in Multiple Myeloma

A total of 28 treatment-naïve patients with stage II or III multiple myeloma (MM) were treated with the combination of clarithromycin, lenalidomide, and dexamethasone (BiRD). Stem cells were collected following granulocyte-colony stimulating factor (G-CSF) or cyclophosphamide (Cy) plus G-CSF mobilization at maximum response. Sufficient stem cells for 2 autologous stem cell transplants were collected from all patients mobilized with Cy plus G-CSF, versus 33% mobilized with G-CSF alone (P < .0001). The duration of prior lenalidomide therapy did not correlate with success of stem cell harvests (P = .91). In conclusion, Cy can be added to G-CSF for stem cell mobilization to successfully overcome the suppressive effect of prior treatment with lenalidomide.

Lenalidomide-induced myelosuppression is associated with renal dysfunction: adverse events evaluation of treatment-naïve patients undergoing front-line lenalidomide and dexamethasone therapy.

Data on 72 patients receiving lenalidomide/dexamethasone for multiple myeloma (MM) was used to determine the factors that are associated with lenalidomide‐induced myelosuppression. Eight of 14 patients with grade ≥3 myelosuppression had baseline creatinine clearance (CrCl) ≤0·67 ml/s. Kaplan–Meier analysis by log‐rank test demonstrated a significant association (P < 0·0001) between renal insufficiency and time to myelosuppression (hazard ratio = 8·4; 95% confidence interval 2·9–24·7, P = 0·0001). Therefore, CrCl is inversely associated with significant myelosuppression. Caution should be exercised when lenalidomide therapy is commenced and CrCl should be incorporated as a determinant of the initial dosing of lenalidomide in MM patients.

Kyphoplasty enhances function and structural alignment in multiple myeloma.

We prospectively evaluated 19 patients with multiple myeloma who had kyphoplasty for vertebral compression fractures. Functional status was assessed preoperatively and 3 months postoperatively using the Oswestry Disability Index. Restoration of anterior and midvertebral height was assessed using lateral radiographs. Meaningful improvement occurred in 16 of 19 patients, with a reduction of the average Oswestry Disability Index from 49 ± 16.6 to 32.6 ± 13.6. Partial restoration of anterior vertebral body height was achieved in 76% of levels with an average of 37.8% restoration of the defect. Partial restoration of midvertebral body height was achieved in 91% of levels with an average restoration of 53.4% of the defect. There were no significant complications. These results were compared with results of a cohort of 26 patients with osteoporotic compression fractures treated with kyphoplasty at 37 levels. There was no difference between the groups in terms of Oswestry Disability Index improvement and midvertebral height restoration after 3 months. Greater anterior vertebral height restoration was achieved in the osteoporotic group (51.2% versus 37.8%). Kyphoplasty is a safe treatment modality for myeloma-related vertebral compression fractures. Efficacy in terms of pain relief and functional outcome is comparable with the results in patients with osteoporosis.

BLT-D (clarithromycin [Biaxin], low-dose thalidomide, and dexamethasone) for the treatment of myeloma and Waldenström's macroglobulinemia.

Multiple myeloma remains incurable. Despite the pursuit of various chemotherapeutic approaches, little improvement in outcome has been made in the last 30 years. Thalidomide, dexamethasone, and clarithromycin are oral, nonmyelosuppressive agents, each with reported single agent activity against myeloma. We evaluated a regimen of clarithromycin (Biaxin), low-dose thalidomide and dexamethasone (BLT-D) in patients with previously untreated or treated multiple myeloma or Waldenströms macroglobulinemia. Patients were initially given clarithromycin 500 mg twice daily, thalidomide 50-200 mg daily, and dexamethasone 40 mg weekly until disease progression. Minimum response was defined as >50% reduction in monoclonal immunoglobulin or light chain levels in serum or urine. Response, toxicity, and survival were determined on an evaluable and/or intent-to-treat basis. Of the 50 patients available for analysis, 92% remain alive and 64% remain on treatment with a median and mean duration of treatment of 7 and 8 months, respectively. Overall, 93% of evaluable patients responded to BLT-D, including 13% complete remissions, 40% near complete responses, 13% major responses, and 27% partial responses. Minimal drug resistance was initially encountered. Neurotoxicity, although usually mild to moderate, was the primary reason for treatment discontinuation. Only four patients died, including three sudden deaths in patients with severe cardiopulmonary disease. It appears that BLT-D is a highly effective, nonmyelosuppressive regimen for myeloma. Caution should be exercised when using thalidomide, alone or in combination, in patients with a preexisting tendency to thromboses, severe cardiopulmonary disease, or neurologic dysfunction.

MAGE-A inhibits apoptosis in proliferating myeloma cells through repression of Bax and maintenance of survivin

Purpose: The type I Melanoma Antigen GEnes (MAGEs) are commonly expressed in cancers, fueling speculation that they may be therapeutic targets with oncogenic potential. They form complexes with RING domain proteins that have E3 ubiquitin ligase activity and promote p53 degradation. MAGE-A3 was detected in tumor specimens from patients with multiple myeloma and its expression correlated with higher frequencies of Ki-67+ malignant cells. In this report, we examine the mechanistic role of MAGE-A in promoting survival of proliferating multiple myeloma cells. Experimental Design: The impact of MAGE-A3 expression on survival and proliferation in vivo was examined by immunohistochemical analysis in an independent set of tumor specimens segregated into two groups: newly diagnosed, untreated patients and patients who had relapsed after chemotherapy. The mechanisms of MAGE-A3 activity were investigated in vitro by silencing its expression by short hairpin RNA interference in myeloma cell lines and primary cells and assessing the resultant effects on proliferation and apoptosis. Results: MAGE-A3 was detected in a significantly higher percentage of relapsed patients compared with newly diagnosed, establishing a novel correlation with progression of disease. Silencing of MAGE-A showed that it was dispensable for cell cycling, but was required for survival of proliferating myeloma cells. Loss of MAGE-A led to apoptosis mediated by p53-dependent activation of proapoptotic Bax expression and by reduction of survivin expression through both p53-dependent and -independent mechanisms. Conclusions: These data support a role for MAGE-A in the pathogenesis and progression of multiple myeloma by inhibiting apoptosis in proliferating myeloma cells through two novel mechanisms. Clin Cancer Res; 17(13); 4309–19. ©2011 AACR.