OPN neutralization synergizes with Ara-C to reduce MRD. (A) Ara-C and OPN neutralization treatment protocol. (B-C) MRD in leukemic mice treated with OPN neutralization and Ara-C or Ara-C chemotherapy alone, as detected by intravital microscopic study. Imaging was performed on the entirety of the calvarial BM, and individual fluorescent cells were counted by hand. Representative images are shown in (B), and quantification of data is shown in (C). MRD burden is significantly decreased in anti-OPN–treated mice, demonstrating that OPN neutralization synergizes with Ara-C to sensitize cells to chemotherapy; n = 5, *P = .01. Scale bars equal 50 µm.