Abstract
Higher Expressions of PTH Receptor Type 1 and/or 2 in Bone Marrow is Associated to Longer Survival in Newly Diagnosed Myeloma Patients Enrolled in Total Therapy 3
INTRODUCTION: The Total Therapy 3 enrolled 303 newly diagnosed multiple myeloma patients at Myeloma Institute for Research and Therapy. Protocol included 2 cycles of VTD-PACE (bortezomib, thalidomide, and dexamethasone and 4-day continuous infusions of cisplatin, doxorubicin, cyclophosphamide, and etoposide) as induction and consolidation therapy after melphalan-based tandem transplantation, which is followed by 3 years of intended maintenance with VTD in year 1 and thalidomide/dexamethasone in years 2 and 3. As part of the protocol, gene expression profiling was performed from baseline bone marrow biopsy samples in 178 individuals.
We have previously reported the clinical correlation between response to bortezomib and serum parathyroid hormone variations in myeloma patients as well as the interaction between receptor 1 and proteasome inhibitors function in cell line and myeloma mouse model.
In this study we examine the PTH receptor 1 and 2 expression levels and their correlation to survival in total therapy 3 enrolled patients.
METHOD: Gene expression profiling was performed using Affymetrix U133 plus 2.0 Microarrays (Santa Clara, CA) in baseline bone marrow biopsy samples from 178 patients enrolled on total therapy 3. Of these 178 patients, 108 were male. The overall median age of these patients was 59 years old at enrollment; 10 % of patients were considered to have high risk disease by 70 GEP model. Cox proportional hazards analysis was performed on the MAS5 normalized log 2 expression values of PTH1R and PTH2R using overall survival as the end point. Optimal dichotomous break points were found for PTH1R and PTH2R that corresponded to the maximum log rank test statistic from all cox proportional hazard models examined. To confirm PTH receptor expression in bone marrow, we performed real-time PCR using Taqman probes (PTH1R: Assay ID Hs00174895_m1 and PTH2R: Assay ID Hs00175044_m1) on subset of samples.
RESULTS: Based on cox proportional hazards regression of PTH1R and PTH2R expression values, patients with higher PTH1R and PTH2R expression demonstrated better survival compared to lower expressing patients. PTH1R expression above optimal break point of 8.92 had a hazard ratio of 0.583 with a 95% confidence interval of (0.351, 0.969) and logrank test p-value of 0.035. PTH2R expression above optimal break point of 6.85 had a hazard ratio of 0.541 with a 95% confidence interval of (0.323, 0.905) and logrank test p-value of 0.018. Furthermore, the patients that were lower expressed in both PTH1R and PTH2R performed significantly poorer in outcome (n= 24 and median survival of 4.52 years logrank p-value+5.71e-05).
Real-time PCR using Taqman probes was able to demonstrate relatively high levels of PTH1R and PTHR2 transcripts at bone marrow level.
CONCLUSIONS: This is the first report indicating that PTH receptors type 1 and 2 gene expression levels are positively associated to overall survival in symptomatic multiple myeloma patients. Also we describe the presence of PTH2R at bone marrow level which function appear associated to myeloma control. These data confirm the correlation and close interaction between the survival of multiple myeloma patients and the parathyroid hormone axis.
Zangari:Norvartis: Membership on an entity's Board of Directors or advisory committees; Onyx: Research Funding; Millennium: Research Funding. Heuck:Celgene: Honoraria; Foundation Medicine: Honoraria; Millennium: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. van Rhee:Janssen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Millenium: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees. Morgan:Celgene Corp: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Myeloma UK: Membership on an entity's Board of Directors or advisory committees; International Myeloma Foundation: Membership on an entity's Board of Directors or advisory committees; The Binding Site: Membership on an entity's Board of Directors or advisory committees; MMRF: Membership on an entity's Board of Directors or advisory committees.
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