Today, there is a theory that proliferative potential of hematopoietic stem cells is depleted, and the balance of committed precursor cells shifts towards suppressors during the development of cancer. However, differentiation of hematopoietic stem cells can vary depending on the tumor type, localization, and microenvironment specifics. The study aimed to assess the impact of tumors of various origins on the CD34+ hematopoietic stem cells (n = 10). Assessment of the cell cycle and cell differentiation via both direct contact with the tumor and exchanging humoral factors only in transwells was conducted by flow cytometry. In the co-culture with К562, the number of hematopoietic stem cells being in their synthesis phase was 2.1%, while in the control it was 11.2% (p = 0.01); in the co-culture with SK-mel37, the number of hematopoietic stem cells being in the G2‒M cell cycle phase was reduced to 0.3% (p < 0.05). 1301 and К562 directed the hematopoietic stem cell differentiation towards granulocyte-macrophage precursor cells (p < 0.05), while 1301 and SK-mel37 directed it towards common multipotent progenitor cells. It is interesting that the number of pluripotent hematopoietic stem cells significantly increased (2-fold) compared to control after incubation with К562 in transwells (24.17% and 10.19%, respectively). Thus, properties of hematopoietic stem cells can vary depending on both tumor type and the way of interacting with these cells.