Angiogenic Signature of Multiple Myeloma Determined by Gene Expression Profiling.

BACKGROUND. Angiogenesis is a hallmark of active multiple myeloma and a therapeutic target, e.g. by thalidomide. Others and we have shown this to be due to a differential and novo expression of pro/antiangiogenic genes in MM as well as an effect of increased plasma cell number. AIM of this study was to investigate based on the expression of (anti)angiogenic genes alone (consensus list determined by medline search),

• whether for respective samples being PPC, BMPC or MMC can be predicted,

• what expression differences between these entities exist,

• if differences between the expression pattern of MMC from early stage vs. therapy requiring MM can be used for prediction, and

• whether the survival of MM–patients undergoing HDT is different in two groups distinguished by their angiogenic signature.

PATIENTS AND METHODS. 187 newly diagnosed MM/MGUS–patients (65 training (TG) / 122 independent validation group (VG)), 14 normal donors (ND) and 12 in vitro generates PPC samples were included. Bone marrow aspirates were CD138-purified by activated magnetic cell sorting. RNA was in-vitro transcribed and hybridised to Affymetrix HG U133 A+B GeneChip (TG) and HG U133 2.0 plus arrays (VG). Expression data were gcrma-normalised and the empirical Bayes algorithm used. P-Values were adjusted using the Benjamini-Hochberg method (Bioconductor). The PANP-algorithm was used to identify expressed genes. iFISH was performed on purified MM-cells using probesets for chromosomes 1q21, 9q34, 11q23, 11q13, 13q14, 15q22, 17p13, 19q13, 22q11 and the translocations t(4;14) and t(11;14). Selected expression data were verified by real time RT-PCR and western blotting.

RESULTS.

• On TG and VG, being BMPC or PPC is predicted by a 17 gene predictor (31 probe sets) without error. Being MMC is predicted with an error rate of 6.9/4.7% with an overall-error rate of 5.8/4.3% in TG/VG, respectively.

• 5 proangiogenic genes/7 probe sets (HGF [hepatocyte growth factor], ADM [adrenomedullin], CXCL2 [chemokine (C-X-C-motif)-ligand 2], IGF1 [insulin-like growth factor 2], Met [HGF-receptor]) and 1 antiangiogenic/1 probe set (SerpinF1, [Serpin peptidase inhibitor F1]) are differentially expressed between these entities concordantly in TG and VG.

• Attribution of MMC to early or therapy requiring can not be predicted. Most patients with MGUS and MM display 1 or several over expressed angiogenic gene. Survival analysis (EFS/OAS) will now be performed based on these findings.

CONCLUSION. Our analysis reveals novel targets for antiangiogenic therapy of multiple myeloma as anti-HGF. There is evidence that angiogenesis related genes are activated early during disease progression as rationale for early intervention using antiangiogenic compounds.