Figure 2
From: Spontaneous loss of B lineage transcription factors leads to pre-B leukemia in Ebf1+/–Bcl-xLTg mice
EB mice develop aggressive disease with neoplastic infiltrates in multiple organs. Compared to Bcl-xLTg control mice, affected EB mice have dense neoplastic round cell infiltrates within hematopoietic and lymphoid tissues including skull bone marrow (a, b) and spleen (c, d), as well as in the lungs (f, g) and kidneys (h, i). Insets show higher magnification. Within the skull (b) and some long bones (not shown), neoplastic cells fill and expand the medullary cavity. They also extend into the meninges and middle ear (b; black arrows). Neoplastic cells completely replace the hematopoietic tissue of the skull bones and are arranged in dense sheets among a scant fibrovascular stroma. Neoplastic cells are large, round to oval with scant to small amounts of eosinophilic homogenous cytoplasm and indistinct cell margins, while normal bone marrow displays a heterogenous population of cells (compare b and a insets). Nuclei are large, round to oval with vesicular chromatin and one to rarely two prominent central nucleoli. Anisokaryosis and anisocytosis are mild. Mitoses (b; open arrows) are frequent (8–10 per × 400 field). (d) Affected EB splenic white pulp (asterisks) is expanded by similar neoplastic cells yet maintains typical architecture. The red pulp contains hematopoietic cells (extramedullary hematopoiesis). Lungs (g) and kidneys (i) from EB mice have perivascular neoplastic infiltrates (black arrows), while Bcl-xLTg lungs (f) and kidneys (h) display limited infiltrates of small lymphocytes with a normal morphology. (e,j) Immunohistochemistry (IHC) shows neoplastic cells in the spleen (e) and mesenteric adipose tissue (j) which display intense nuclear staining with Ki-67 antibody. Images a–j are representative of three EB, three Ebf1+/– and two Bcl-xLTg mice analyzed. (k, l) IHC reveals numerous cells in control bone marrow (k, Ebf1+/−) display nuclear staining with EBF1 antibody, while neoplastic cells in EB bone marrow do not retain stain (l). (m) Immunoblot showing EBF1 expression in whole cell extracts from wild-type MACS-sorted splenic B cells (EBF1 staining control) compared to whole cell extracts from pre-B tumor cell isolates in four different EB mice and three different Eμ-Myc mice. GAPDH is included as a loading control.
