CD34+ hematopoietic progenitor cells (HPC) isolated from healthy donors, from patients with different tumors, and from chronic myelocytic leukemia (CML) patients were used for the analysis of the cGMP/PKG pathway’s effects on proliferation and differentiation of these cells to megakaryocytes [156]. The gene discussed is CD34; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.