Analysis of melphalan-induced DNA ICL formation and repair in plasma cells using the Comet assay.

Examples of comet images obtained from a melphalan-naive (Myeloma 1) and relapsed patient following melphalan-conditioned autograft (Myeloma 2). Both patients showed similar comet tail length following 10 Gy irradiation (no melphalan). Treatment with 50 μM melphalan for 1 hour and subsequent incubation for 16 hours to allow maximum ICL formation (t = 16 hours) produced an equivalently reduced comet tail in both samples. At t = 40 hours the same level of ICLs was still present in Myeloma 1. In contrast, in Myeloma 2 the comet tail length returned to a level similar to the irradiated control, revealing extensive repair of the ICLs. All images stained with propidium iodide. Original magnification, × 20.