Identification of Genes with Prognostic and Therapeutic Relevance in Multiple Myeloma Using Serial Analysis of Gene Expression Technique.

Serial analysis of gene expression (SAGE) allows a comprehensive profiling of gene expression within a given tissue and also an assessment of transcript abundance.

Objectives: We generated SAGE libraries from normal and neoplastic plasma cells with the aim of identifying genes differentially expressed in MM that could be useful as new potential diagnostic, prognostic markers or therapeutic targets.

Material and methods: Normal plasma cells were obtained from palatine tonsils of 20 children who underwent tonsillectomy. MM SAGE library was obtained from bone marrow plasma cells of two IgGk newly diagnosed MM patients. Purified normal and neoplastic plasma cells were isolated after magnetic sorting of CD-138-positive cells.

Results: We obtained 29,918 SAGE tags from normal and 10,340 tags from tumor libraries. Computer-generated genomic analysis identified 50 overexpressed genes in MM library. After comparison of unique tags expression levels, we selected 12 overexpressed (at least 10 times) genes in the MM library (ZFHX1B, XBP1, PIM2, LGALS1, RANBP2, P53CSV, DDX5, LSM5, JUND, MAPKAPK2, SP140 and NTN1) for further investigation. Expression of 10 out of 12 genes was validated by quantitative real-time PCR in purified plasma cells of 31 MM patients and three controls. XBP1, RANBP2, P53CSV, DDX5, MAPKAPK2 were overexpressed in at least 50% of MM cases. Comparative analyses of relative expression (2^{-D D CT}) of the 10 genes in 31 MM cases and 3 controls showed statistically significant difference between cases and controls for all genes but PIM2 and ZHFX1B, confirming the SAGE data. Also, we could identify that RANBP2 and ZHFX1B have prognostic impact in MM OS (p = 0.040 and p = 0.0502, respectively). Multivariate analysis confirmed RANBP2 expression as a good independent prognostic marker.

Conclusions: SAGE technique allowed the identification of genes differentially expressed in normal and neoplastic plasma cells. These genes may have important role in tumorigenesis or may be possible therapeutic targets for MM control, particularly P53CSV and MAPKAPK2, or prognostic impact, as RANBP2.