NK cells from the blood of CML patients are progressively decreased in number as the disease progresses. We hypothesize that BCR/ABL may be directly responsible by interfering with NK differentiation. Under NK differentiation conditions, the NK cloning frequency was significantly decreased from CML CD34VHLA-DR cells ( 1:481 -1:16857 ) compared to normal donors (1:24-1:38) (p<0.001). In some experiments, CD56VCD3 NK cells generated from CML progenitors were sorted by FACS and examined by FISH. In 3 of 4 advanced phase CML patients, CD34+/HLA-DR+ cells gave rise to BCR/ABL+ NK cells (14-83%). This finding prompted us to further investigate NK cells from the blood of CML patients. In contrast to chronic phase CML, significantly increased numbers of CD56VCD3 NK cells from advanced phase CML patients were BCR/ABL+ ( 16±4.4% vs 40±11.9%, p=0.049), whereas T cells were always BCR/ABL (5.0±1% vs 4.4±1%, p=0.37). To test the effects of BCR/ABL as the sole genetic abnormality, BCR/ABL was transduced into cord blood (CB) CD34+ cells using a MSCV retrovirus containing eGFP-p210. After 3 weeks of culture, 28.6+3.7% of total cells were CDSoVeGFP+ NK cells from eGFP transduced CD34+ cells, as compared to 1.9+0.5% when transduced with eGFP-p210 (n=l 1, p=0.001). eGFP-p210 transduced CD34+ cells gave rise to significantly decreased numbers of NK cells from 600 progenitors (18,361±5,421) compared to eGFP transduction alone (229,825±56,183) (n= 11, p=0.003). eGFP-p210 transduced cells readily gave rise to myeloid differentiation, suggesting that decreased NK differentiation was not due to a general survival disadvantage but rather a selective effect on lymphoid differentiation. In order to investigate the extrinsic effect of p210 transduced progenitor cells on normal NK cell differentiation, normal CB CD34VCD38 cells (300 cells/well) were co-cultured with 50 eGFP-p210 or eGFP transduced autologous CB CD34+ cells. Compared to the extrinsic addition of eGFP transduced cells (68,894± 15,775), the extrinsic addition of eGFP-p210 transduced CD34+ cells suppressed the NK differentiation of normal CB CD34VCD38+ cells (3,326±869) (p=0.002). This study provides the first evidence that 1) BCR/ABL is directly responsible for the altered NK differentiation from BCR/ABL+ progenitors, 2) BCR/ABL+ progenitors extrinsically suppress normal NK differentiation, and 3) NK cells can be involved with the malignant clone in advanced stage CML.
|Original language||English (US)|
|Issue number||11 PART I|
|State||Published - Dec 1 2000|