Spleens of myelofibrosis patients contain malignant hematopoietic stem cells
Xiaoli Wang, Sonam Prakash, Min Lu, Joseph Tripodi, Fei Ye, Vesna Najfeld, Yan Li, Myron Schwartz, Rona Weinberg, Paul Roda, Attilio Orazi, Ronald Hoffman
Xiaoli Wang, Sonam Prakash, Min Lu, Joseph Tripodi, Fei Ye, Vesna Najfeld, Yan Li, Myron Schwartz, Rona Weinberg, Paul Roda, Attilio Orazi, Ronald Hoffman
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Research Article Hematology

Spleens of myelofibrosis patients contain malignant hematopoietic stem cells

Abstract

Cancer stem cell behavior is thought to be largely determined by intrinsic properties and by regulatory signals provided by the microenvironment. Myelofibrosis (MF) is characterized by hematopoiesis occurring not only in the marrow but also in extramedullary sites such as the spleen. In order to study the effects of these different microenvironments on primitive malignant hematopoietic cells, we phenotypically and functionally characterized splenic and peripheral blood (PB) MF CD34+ cells from patients with MF. MF spleens contained greater numbers of malignant primitive HPCs than PB. Transplantation of PB MF CD34+ cells into immunodeficient (NOD/SCID/IL2RĪ³null) mice resulted in a limited degree of donor cell chimerism and a differentiation program skewed toward myeloid lineages. By contrast, transplanted splenic MF CD34+ cells achieved a higher level of chimerism and generated both myeloid and lymphoid cells that contained molecular or cytogenetic abnormalities indicating their malignant nature. Only splenic MF CD34+ cells were able to sustain hematopoiesis for prolonged periods (9 months) and were able to engraft secondary recipients. These data document the existence of MF stem cells (MF-SCs) that reside in the spleens of MF patients and demonstrate that these MF-SCs retain a differentiation program identical to that of normal hematopoietic stem cells.

Authors

Xiaoli Wang, Sonam Prakash, Min Lu, Joseph Tripodi, Fei Ye, Vesna Najfeld, Yan Li, Myron Schwartz, Rona Weinberg, Paul Roda, Attilio Orazi, Ronald Hoffman

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Figure 3

Immunohistochemical analyses of spleens of NSG mice transplanted with MF CD34+ cells.

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Immunohistochemical analyses of spleens of NSG mice transplanted with MF...
(A and B) Spleen sections 5 months after transplantation with PB1 CD34+ cells stained with H&E (A) and hCD45 (B). The image demonstrates normal splenic architecture (A); rare hCD45+ cells as indicated by arrows were detected (B). (C–I) Spleen sections 5 months after transplantation with SP1 CD34+ cells. (C) H&E staining demonstrated normal splenic architecture with a preserved white pulp and EMH in the red pulp (D). Immunohistochemical staining demonstrated the presence of human granulocytes as well as lymphocytes in the red pulp (E). The white pulp was composed primarily of hCD45+ lymphoid cells (F), which included both hCD5+ T cells (G) and hCD20+ B cells (H). Many normoblasts in the red pulp were mTER119–, indicating their human origin (I). The horizontal arrow indicates mTer119+ normoblasts, while the vertical arrow indicates mTer119– normoblast. (J–O) Spleen sections 9 months after transplantation with SP1 CD34+ cells. (J) The normal splenic architecture was preserved with a prominent white pulp. (K) H&E image demonstrated trilineage hematopoiesis in the red pulp. Immunohistochemical stains demonstrated human myeloid cells as indicated by the arrow in the red pulp (L). The white pulp was almost entirely composed of hCD45+ lymphoid cells (M), which were predominantly hCD5+ T cells (N), with fewer hCD20+ B cells (O). Original magnification, A: ×200; B, D, and I: ×400; C and F–H: ×100; J and M–O: ×40; E, K, and L: ×600. WP, white pulp; RP, red pulp; Pos, positive; Neg, negative; g, granulocytic precursors; e, erythroid precursors; m, megakaryocyte; l, lymphocyte.