OBJECTIVETo study the potential mechanism of the new steroidal drug NSC67657 induced leukemic cells differentiation.

METHODSCell proliferation was assayed by MTT assay. Surface antigen CD14 on THP-1 cells treated by NSC67657 at different time different concentration, was detected by flow cytometry (FCM). The expression of beta-catenin- interacting protein 1 (ICAT) gene and protein were detected by RT-PCR and Western blot. Eukaryotic expressing vector pDsRed-ICAT was constructed and transfected into HL60 cell line. FCM, Wright's staining and electronmicroscope were employed to analyse the differentiation of transfected THP-1 cells after they were treated with NSC67657 for 24 hours.

RESULTSThe proliferation of THP-1 cells was significantly inhibited by NSC67657 treatment. The level of CD14 expression was elevated in line with the increasing drug concentration and treatment time. 10 µmol/L NSC67657 treatment for five days was the optimal condition for the induction of THP-1 cells differentiation, when the CD14(+) THP-1 cells were more than 90%. Morphological study indentified the THP-1 cells of monocytic differentiation. The eukaryotic expressing vector pDSRed-ICAT was successfully constructed, and almost 90% positive clone could be obtained after G418 screening. Electro-transfection was employed for transfecting the vector into THP-1 cells. After the transfection the expression of ICAT gene and protein was increased. On the NSC67657 treatment, there was not significant difference in CD14 expression on transfected THP-1 cells compared to that on the control groups. After 24 h treatment, the transfected THP-1 cells remained in early differentiated stage.

CONCLUSIONNSC67657 can induce THP-1 cell to monocytic differentiation and activate the expression of ICAT gene, but overexpression of ICAT itself is not sufficient to induce such differentiation.