Abstract 2423: Signaling pathway profiling in multiple myeloma
Authors: Xu Jing , Hielscher Thomas , Lehners Nicola , Ellert Elena , Ho Anthony D. , Schirmacher Peter , Goldschmidt Hartmut , Andrulis Mindaugas , Raab Marc-Steffen 
Published: August 2015

Abstract
Multiple myeloma (MM) is an incurable malignancy of terminally differentiated B cells. The disease develops from preclinical stages, i.e. MGUS/SMM, to symptomatic MM and eventually becomes refractory to therapy. Recent data indicate relevant clusters of mutational hotspots within signaling pathways, yet only very limited data is available on actual signaling profiles. Therefore, we aimed to characterize the activation of five oncogenic signaling pathways (RAS/RAF/MEK/ERK, JAK-STAT, NF-κB, PI3K/AKT and cMYC) in primary MM biopsies and to correlate the data with disease stage and clinical outcome.
We used immunohistochemistry to assess key activation markers of respective signaling pathways in a discovery cohort (DC) of patients with SMM/MGUS (n = 32), symptomatic MM (n = 195) and refractory MM (n = 50). Furthermore, an independent validation cohort (VC, n = 84) of newly diagnosed MM, enrolled in two clinical trials, was employed. Activation scores included signal intensity as well as the percentage of positive versus total tumor cells per sample to account for potential clonal heterogeneity. A non-linear principal component analysis was applied to integrate signaling scores per pathway and sample.
Overall, NF-κB was activated in 90% of cases; ERK or AKT in 45%, MYC and STAT3 activation in 44% and 27%, respectively. At diagnosis, strong activation of single pathways was found in a mutually exclusive pattern. In refractory MM, the signaling pathways were more frequently activated, except for NF-κB (NF-κB, MYC, AKT p&lt; 0.001; ERK p = 0.002; STAT3 p = 0.008). Moreover, simultaneous activation of multiple pathways was detectable in 72% of refractory MM compared to 38.5% of MM and only 9.4% of SMM/MGUS. In the VC, MYC and STAT3 activation was associated with a higher ISS score (p = 0.05 and p = 0.0011, respectively). In addition, activated STAT3 correlated with shorter overall survival (HR 2.97, p = 0.020) and progression-free survival (HR 2.31, p = 0.026), MYC activation with shorter overall survival (HR 2.41, p = 0.028). Furthermore, pathway activation clustering revealed a prognostic hierarchy with isolated NF- κB activation being favorable; ERK or AKT activation being neutral and MYC or STAT3 activation being indicative for poor outcome.
To conclude, this is the first systematic analysis of oncogenic signaling patterns on primary MM samples. Our data reveal a mutually exclusive landscape of most strongly activated pathways in newly diagnosed MM and proof to be of prognostic significance, while simultaneous pathway activation appears to be associated with disease progression.
Citation Format: Jing Xu, Thomas Hielscher, Nicola Lehners, Elena Ellert, Anthony D. Ho, Peter Schirmacher, Hartmut Goldschmidt, Mindaugas Andrulis, Marc-Steffen Raab. Signaling pathway profiling in multiple myeloma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2423. doi:10.1158/1538-7445.AM2015-2423