ALDH1A1 and plasma cell myeloma: To evaluate whether the expression of ALDH1 exhibits changes in the course of myeloma therapy and disease progression, we queried the mRNA levels of the three most well-studied members of the ALDH1 gene family, ALDH1A1, ALDH1B1, and ALDH1A3, in 9 patients with myeloma for which the following four serial, microarray-based gene expression profiles (GEPs) were available: at diagnosis, prior to the first and second autologous stem cell transplant, and after the second transplant.