Abstract 3189: The alternate activation of hedgehog pathway, either in CD138+ or in CD138-CD19+ multiple myeloma primary cells, impacts on disease outcome
Authors: Martello Marina , Remondini Daniel , Borsi Enrica , Procacci Mauro , Santacroce Barbara , Dico Angela Flores , Pezzi Annalisa , Zamagni Elena , Tacchetti Paola , Pantani Lucia , Marzocchi Giulia , Rocchi Serena , Mancuso Katia , Zannetti Beatrice Anna , Martinelli Giovanni , Cavo Michele , Terragna Carolina 
Published: July 2016

The iperactivation of Hedgehog (Hh) pathway, which controls the refuel of the tumor clone, might be critical to Multiple Myeloma (MM) recurrence. In order to dissect the role played by Hh pathway in different MM cells compartments, and to evaluate its clinical impact on patient outcomes, here we explore the transcriptomic and genomic profiles in both CD138+ plasma cells and CD138-19+ B progenitors cells obtained from newly diagnosed MM patients (pts),

The study included a cohort of 126 pts, homogenously treated with bortezomib-based regimens and ASCT. DNA and RNA were obtained from both CD138+ plasma cell fraction and CD19+ B cells. Gene expression profiling (GEP) (HG U133 Plus 2.0) and genomic analysis (SNP 6.0) were performed on Affymetrix platform. Data were analysed by employing several software: dChip (GEP clustering), Ingenuity Pathway Analysis (GEP Enrichment) and Nexus (Copy number).

By unsupervised hierarchical clustering, an Hh signature of 10 genes - SHH, IHH, DHH, SMO, PTCH1, PTCH2, SUFU, GLI1, GLI2 and GLI3 - was identified, and it was able to significantly cluster pts in two subgroups: cluster 1 (70 pts) and cluster 2 (56 pts. An overall significant activation of Hh pathway was shown in cluster 2, as compared to cluster 1. Of note, the Hh pathway was down regulated in CD19+ B cells obtained from pts included in cluster 2, while it was overexpressed in cluster 1 pts. Western blots on both cell fractions confirmed this opposite Hh genes behavior. A higher genomic instability (e.g. higher frequencies of both t(4;14) and del(17p)) was demonstrated in CD138+ cells from cluster 2 pts and, at least 5 known tumor suppressor genes, such as RB1, BRCA2, PDX1, FOXO1 and TP53 were affected. Conversely, cluster 1 pts were mainly characterized by hyperdiploid karyotypes. The more aggressive phenotype of cluster 2 pts was confirmed by an overall deregulation of cell adhesion processes (CD44, LIMS1, COL4A2, CTGF, COL1A1, FN1), increased proliferation (MYCBP, IL22, SDPR, SOX2, SOX6) and DNA repair mechanisms (SP1, SMARCD3, FOXA3). Hh pathway activation significantly influenced pts’ outcome, since those included in cluster 2 had a shorter PFS and OS compared to cluster 1. In fact, the 5-year PFS estimates were 31% vs 56% (p = 0.0062), whereas the OS probabilities were 66% and 83%, respectively (p = 0.0071). Of note, both hazard ratios for PFS and OS were doubled in pts included in cluster 2, as compared to pts included in cluster 1. Finally, multivariate analyses confirmed that being part of cluster 2 was an independent prognostic factor for both PFS and OS, along with del(17p) and ISS 3.

Two alternate Hh-driven subtypes of MM might be identified at diagnosis, which correlated with pts outcomes. Stratification of pts according to their molecular background might help the fine-tuning of future clinical studies.

Acknowledgements: FP7 NGS-PTL project, Progetto Regione-Università 2010/2012 L. Bolondi.

Citation Format: Marina Martello, Daniel Remondini, Enrica Borsi, Mauro Procacci, Barbara Santacroce, Angela Flores Dico, Annalisa Pezzi, Elena Zamagni, Paola Tacchetti, Lucia Pantani, Giulia Marzocchi, Serena Rocchi, Katia Mancuso, Beatrice Anna Zannetti, Giovanni Martinelli, Michele Cavo, Carolina Terragna. The alternate activation of hedgehog pathway, either in CD138+ or in CD138-CD19+ multiple myeloma primary cells, impacts on disease outcome. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3189.