A recent publication from our group demonstrated that the induction of genes encoding effectors of the SUMOylation pathway correlated with decreased MM patient survival. Preliminary data suggest that genes from this pathway not only correlate with response to bortezomib in patients with relapsed MM, but also define a subset of patients at initial diagnosis. Therefore, we seek to further investigate the role of protein regulation by the SUMOylation pathway in myelomagenesis. SPECIFIC AIM 1: to investigate whether gene expression of selective E3s are induced in MM patient samples and correlated with resistance to bortezomib-based therapy. We will examine the gene expression profiles generated from patients on the CREST and APEX clinical trials. Preliminary data suggests that RNF4, an E3 that recognizes poly-SUMOylated proteins for proteasomal degradation, is significantly more highly expressed in MM malignant plasma cells compared to normal plasma cells. Moreover, RNF4 and other components of the SUMOylation, Ubiquitination and Proteasome pathways may be induced in MM patients that did not respond to bortezomib. We will further interrogate the role of RNF4 in protein regulation and resistance to bortezomib in MM cell lines. Specifically, we will both over-express and knock down RNF4 in MM cell lines and examine the cellular effects of treatment with bortezomib. SPECIFIC AIM 2: to expand the biomarker profiles to genes in the SUMO, Ubiqutin and proteasome subunit families in order to better identify subpopulations of patients more likely to respond to proteasome-directed therapy and identify new targets for therapeutic intervention. We will include at least 10 genes from each family of functionally related genes and compare their predictive values to that of clinical parameters such as age, B2-microglobulin, C-reactive protein and albumin. We will also investigate the individual correlations with overall survival after bortezomib treatment. We will also generate bortezomib-resistant MM cell lines in the laboratory and quantify the expression of these genes in the resistant cell lines compared to the parental bortezomib-sensitive cell lines.