Use of Ubiquitin-Proteasome System Profiling for Differentiating Between Various Leukemic Processes.

Abstract Abstract 4712 The ubiquitin-proteasome system (UPS) plays a major role in cell homeostasis in normal and neoplastic states. Expression and function of the UPS system vary with the specific characteristics of individual cell types, suggesting that determination of UPS “signatures” could be useful in identifying various cell populations. Since direct analysis of cancer cells is often problematic, even in hematologic diseases, we explored the potential of using UPS signatures in plasma to differentiate between various leukemias. We first analyzed plasma UPS profiles of patients with acute myeloid leukemia (AML; n=111), acute lymphoblastic leukemia (ALL; n=29), advanced myelodysplastic syndrome (MDS; n=20), chronic lymphocytic leukemia (CLL; n=118), or chronic myeloid leukemia (CML; n=128; 46 in accelerated/blast crisis [ACC/BL], 82 in chronic phase), and 85 healthy control subjects. Plasma levels of proteasome, ubiquitin (poly-ubiquitin), and the 3 proteasome enzymatic activities (chymotrypsin-like [Ch-L], caspase-like [Cas-L], trypsin-like [Tr-L]) were measured. Specific activities were calculated by normalizing each of the 3 enzyme activities to the levels of proteasome protein in plasma (Ch-L/p, Cas-L/p, and Tr-L/p). These 8 variables were used in multivariate logistic regression models to differentiate between leukemic processes. UPS signatures provided clear differentiation between patients with a leukemic process and normal controls (AUC=0.991), using 6 different variables (Tr-L/P, Ch-L, Ch-L/p, Cas-L, Cas-L/P, ubiquitin). Distinguishing between acute (AML, ALL, MDS) and chronic (CML, CLL) processes was less efficient (AUC=0.853 using Tr-L, Tr-L/P, Cas-L/P, Ch-L/P, proteasome, Ch-L), likely due to the high proportion (36%) of CML patients in ACC/BL phase. However, UPS signatures generally yielded powerful differentiation between individual leukemias (Table). MDS was not well differentiated from AML (AUC=0.791), reflecting the significant biological overlap of these diseases. These data support the potential usefulness of the UPS profile to aid in the differential diagnosis of various leukemias. Comparison Analytes N (Case/Control) AUC MDS vs Normal PS, UBT, C-L, Tr-L, C-LP Ch-P 105 (20/85) 0.98 ALL PS, UBT, Tr-L, C-LP 49 (20/29) 0.9845 AML PS, UBT, Ch-L, Tr-L, C-LP, Ch-LP, Tr-L/P 131 (20/111) 0.791 CLL C-L/P, Ch-LP 163 (27/136) 0.9909 CML UBT, C-LP, Tr-L 147 (20/127) 0.9496 CML (Chronic) UBT, C-LP, Tr-L, Tr-L/P 101 (20/81) 0.9608 CML (ACC/BL) UBT, C-LP, Tr-L, Tr-LP, Ch-L 66 (20/46) 0.9516 AML vs Normal UBT, C-L, Tr-L, Tr-LP, Ch-LP 196 (111/85) 0.9884 ALL C-LP, Ch-LP, UBT, Ch-LP, PS 140 (111/29) 0.9503 CLL C-LP, Ch-LP 283 (147/136) 0.9835 CML Tr-LP, Tr-L, UBT, C-LP, C-L, Ch-LP 238 (111/127) 0.8301 CML (Chronic) Tr-LP, Tr-L, UBT, C-LP, Ch-LP, PS 192 (111/81) 0.8396 CML (ACC/BL) Tr-LP, Tr-L, UBT, C-LP, Ch-LP, C-L 157 (111/46) 0.8239 ALL vs Normal UBT, Tr-L 114 (29/85) 0.9984 CLL UBT, Tr-L, Tr-LP, Ch-L, Ch-LP, C-LP 147 (29/118) 0.9031 CML no Tr-LP 156 (29/127) 0.9005 CML (Chronic) no Tr-L 110 (29/81) 0.9264 CML (ACC/BL) no Tr-L 75 (29/46) 0.8909 CLL vs Normal C-L/P, Ch-L, UBT 203 (118/85) 0.9978 CML C-LP, C-L, Ch-LP, Tr-L, UBT 245 (118/127) 0.9746 CML (Chronic) Cas-LP, C-L, Ch-LP, Tr-L UBT 199 (118/81) 0.9749 CML (ACC/BL) C-LP, C-L, Ch-LP, Tr-L, UBT 164 (118/46) 0.9746 CML vs Normal UBT, Tr-L 212 (127/85) 0.9986 Abbreviation: PS=proteasome protein Disclosures: No relevant conflicts of interest to declare.