ALBERT

Description: It is well established that osteoblast formation and function are profoundly impaired in multiple myeloma (MM) patients. Osteoblastic cells also regulate myeloma cell growth and increasing bone formation result in a reduction of tumoral burden in mice. Recent data suggest that ubiquitin-proteasome pathway, the major cellular degradative system and therapeutic target in myeloma cells, also regulates osteoblast differentiation. Further it has been demonstrated that different proteasome inhibitors may stimulate bone formation in mice. Finally, preliminary observations obtained in MM patients treated with the proteasome inhibitor Bortezomib show an increase of bone specific alkaline phosphatase in responder patients as compared to non-responder ones. Currently it is not know whether the proteasome inhibitor Bortezomib may have a direct effect on osteoblast and bone formation in vitro human cultures and in vivo in MM patients. To clarify this issue first we checked the effect of Bortezomib either on osteoblast differentiation and formation or on osteoblast proliferation, survival and function. In long-term human BM cultures we found that Bortezomib did not reduce the number of both early bone marrow (BM) osteoblast progenitors Colony Forming Unit-Fibroblast (CFU-F) and late ones Colony Forming Bone nodules (CFU-OB). On the other hand we found that Bortezomib (2–3 nM) significantly induced osteoblast phenotype in human mesenchymal cells incubated in presence of osteogenic factors. A stimulatory effect on osteoblast markers was observed after 24 hours of Bortezomib treatment. Consistently we found that Bortezomib significantly increased the activity of the transcription factor Runx2/Cbfa1 in human osteoblast progenitors without affecting the canonical WNT signaling pathway checked by the evaluation of nuclear and cytoplasmatic active beta-catenin levels. Using the human osteoblast like cells MG-63 and immortalized normal osteoblasts (HOBIT) we found that Bortezomib at concentration ranging between 2nM and 5nM did not inhibit osteoblast proliferation or induce osteoblast apoptosis. Similarly, Bortezomib did not affect the expression of osteoblast markers, Runx2/Cbfa1 activity and WNT signaling in both MG-63 and HOBIT cells. To extent our in vitro observation we have evaluated the potential effect of Bortezomib in vivo in MM patients. Bone histomorphometry as well as immunostainig for Runx2/Cbfa1 and beta-catenin was performed on BM biopsies obtained from 15 MM patients before and after 6–8 cycles of Bortezomib administrated in mono-therapy. A significant increase in the number of osteoblastic cells X mm2 of bone tissue and in the number of Runx2/Cbfa1 positive osteoblastic cells was observed only in responder patients showing an early increase of the serum alkaline phosphatase. In conclusion our data indicate that Bortezomib may increase osteoblast differentiation in human mesenchymal cells without affecting the proliferation, survival and function of mature osteoblasts. In vivo and in vitro observations support the hypothesis that both direct and indirect effects on bone formation process could occur during Bortezomib treatment.

Description: Introduction: A phase II multi-center study was performed to investigate the efficacy of Bortezomib with high-dose dexamethasone (Vel-Dex) as induction therapy in multiple myeloma (MM) patients (pts) candidates to high-dose therapy. Methods: Patients were planned to receive 4 courses of Vel-Dex (Bortezomib 1.3 mg/m2 i.v. on days 1, 4, 8, 11; oral Dexamethasone 40 mg on days 1–4 and 8–11 every 3 weeks), followed by 2 courses of DCEP 4 weeks apart with stem cell collection, and a single autologous transplant with melphalan 200 mg/m2. Patients were untreated, aged ≤65 years, with Durie-Salmon stage III, II, or I in progression. Criteria of response were: CR: negative serum/urine immunofixation with

Description: Abstract 5134 BACKGROUND: Bisphosphonates (BP) are standard supportive care in patients affected by symptomatic multiple myeloma (MM) with skeletal lesions. Despite the long term use of BP in the clinic, many of the effects of this category of drugs and their optimal schedule of administration are still matter of debate. In the recent past the identification of osteonecrosis of the jaw induced clinicians and researchers to reevaluate the schedule of administration of BP in myeloma, questioning about their effects on other cells than osteoclasts. Therefore a better definition of risks and benefits of anti-catabolic agents may help addressing future studies in this field. Recently a growing number of publications alerted orthopedics and endocrinologists about a rare but serious event called “atypical low energy fractures” (LEF) in patients affected by osteoporosis treated with long term BP (1–3). LEF refer to stress fractures, mainly localized in the subtrochanteric region, spontaneous or secondary to minor trauma, often preceded by local pain, with specific radiologic patterns and sometimes delayed healing. Localizations in bones different than femur have been reported. Still debated is the association with BP and the pathophysiology of this condition. So far three cases of fractures with the characteristics of LEF have been described in MM patients. METHODS: in order to evaluate the possible existence of other cases of LEF in patients with MM we started a retrospective survey in hematological centers, collecting the cases of MM followed by each center between January 2005 and December 2010, and any case of atypical fracture not related to MM or major trauma. Inclusion criteria for LEF were so defined: diagnosis of MM; treatment with BP; fractures induced by minor trauma or spontaneous, not associated with MM localization; radiological aspect of stress fracture; +/− prodromic pain. Central revision of patients history and radiology will be conducted with the support of an orthopedic in the patients with atypical fractures, followed by bone histomorphometry on bone marrow biopsy. RESULTS: The study is ongoing. At present seven centers reported a total of 1065 patients affected by MM followed between 2005 and 2010 and five cases of suspect LEF. The first patient is a woman diagnosed with anaplastic myeloma in 2002, apparently in complete remission after 4 lines of treatment. In June 2008 the patient was diagnosed with an atraumatic left fracture of the fifth metatarsal bone, followed by a right metatarsal fracture one month later and second right metatarsal stress fracture in 2011. The fractures were not related to myeloma localization. Other four cases of fractures are under investigation in other two center. CONCLUSIONS: MM patients are exposed to high rate of bone fractures related to the hematological disease and at the best of our knowledge the frequency of stress fractures in this population is unknown. With the present study, over a population of more than one thousand patients, we observed five cases of possible LEF that will undergo detailed analysis through central revision of patients history, radiology and bone histomorphometry with the aim to identify individual risk factors. Despite LEF is a rare and still controversial condition, the identification of individual risks to develop fractures not secondary to MM, may help clinicians tailoring the treatment for bone disease, much needed in an era of new drug discoveries for bone treatment. Disclosures: Palumbo: Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Honoraria; Amgen: Honoraria.