Effect of high ectopic HOXB4 expression in human CD34⁺ cells on myeloid differentiation.

High ectopic HOXB4 expression in human CD34⁺ cells impairs myeloid differentiation in vitro. Following transduction with different HOXB4 vector contructs and the GFP control vector, FACS-sorted GFP⁺ cells (A,C) and unsorted transduced cells (B) for each vector were cultured for 7 days in liquid medium containing a myeloid differentiation–inducing cytokine cocktail. Thereafter, the cells were counted, and reporter gene expression was determined after staining cell samples either with PE-labeled antihuman CD33 antibodies alone or with a combination of antihuman CD14–APC/CD15–PE antibodies. (A) Comparison of the absolute number of hematopoietic cells generated from 30 000 GFP⁺-sorted input cells. (B) Percentage of GFP⁺ cells at the day of harvest compared with that at initiation of differentiation (input) in cultures with unsorted transduced cells. (C) Percentage of cells expressing myeloid-specific cell surface markers (CD33, CD14, and CD15) in cultures initiated with FACS-purified GFP⁺ cells. Results are shown as mean ± standard error (bar) values. The Student t test (paired; 2-sided) was applied for statistical analysis. *P < .05.