Differential cellular expression of the human MSH2 protein in normal and myelodysplastic haematopoiesis

Loss of human MSH2 (hMSH2) protein might be involved in the multistep pathogenesis of haematological malignancies associated with genetic instability. Here, we examine cellular hMSH2 expression in bone marrow samples from 10 haematopoietically normal individuals in comparison with nine patients with myelodysplastic syndrome (MDS) [one refractory anaemia (RA), two RA with ringed sideroblasts (RARS), four RA with excess blasts (RAEB) and two RAEB in transformation (RAEB-T)]. HMSH2 protein was predominantly expressed in myeloblasts and promyelocytes. Blast cells from three patients with RAEB and one with RAEB-T displayed absent or very low hMSH2 expression. As no correlation between hMSH2 expression and chromosomal aberrations was observed, further genetic events seem to be required to induce karyotype instability.