ALDH1A1 and plasma cell myeloma: More recently, we demonstrate that member A1 of the ALDH1 family of proteins, ALDH1A1, was up-regulated in the course of myeloma therapy and progression, and that enforced expression of ALDH1A1 led to both increased tumorigenicity and resistance to two widely used myeloma drugs (doxorubicin, bortezomib) in vitro and in vivo [56].