The study was aimed to investigate the mechanism of cytotoxic effect of trichosanthin (TCS) on leukemia or lymphoma cell lines. Trypan blue exclusion was used to measure the effect of TCS on cell growth and flow cytometry was used to detect the effects of TCS on cell apoptosis and cell cycle. The results indicated that the TCS could inhibit proliferation of various leukemia/lymphoma cell lines at 12.5 microg/ml concentration, but the effect of TCS on T-lymphocyte and macrophage cell lines showed inducing cell apoptosis and the effect of TCS on B lymphocyte cell line showed inhibiting cell growth. Detection of the cell cycle revealed that TCS could arrest B lymphocytes at S phase, but not had this effect on T lymphocytes at the same condition. It is concluded that TCS can kill leukemia/lymphoma cells through different mechanisms such as inducing cell apoptosis or arresting cell cycle according to cell types.
Antineoplastic Agents, Phytogenic ; pharmacology ; Apoptosis ; drug effects ; Cell Cycle ; drug effects ; Humans ; Leukemia ; pathology ; Lymphoma ; pathology ; Trichosanthin ; pharmacology ; Tumor Cells, Cultured

OBJECTIVETo investigate if CYP3A5 is involved in drug resistances mechanisms of acute leukemia.

METHODSBy using RT-PCR, immunohistochemistry and MTT assay, CYP3A5 mRNA and protein were detected in leukemia cell lines and acute leukemia patients, meanwhile transcriptional regulation of CYP3A5 induced by daunorubicin was observed. A pcDNA3-CYP3A5 reconstituted plasmid and its stably transfected cell line HL-60/CYP3A5 were both established.

RESULTSCYP3A5 mRNA was detected in K562 and U937 cells, whose IC(50) values of daunorubicin were 2.1-fold higher than those of NB4 and HL-60 cells. Bone marrow CYP3A5 positive blast cell percentage at the time of diagnosis in primary drug resistance group (17.2%) was significantly higher than that of continuous complete remission (CCR) group (0.4%) and secondary drug resistance group (5.4%). In their first complete remission of the early relapsed group, the positive rate had been 23.9% as compared with that of CCR group (1.3%). Daunorubicin increased CYP3A5 mRNA level in K562/A02 and activated its transcription in HL-60/ADR. HL-60/CYP3A5 cell was significantly resistant to daunorubicin and vincristine than HL-60 cells did (3.0 and 4.0 times, respectively).

CONCLUSIONCYP3A5 expressed in leukemia cells may cause in situ metabolization of many kinds of anticancer drugs, thus led to drug resistance.

Cytochrome P-450 CYP3A ; Cytochrome P-450 Enzyme System ; genetics ; physiology ; Daunorubicin ; pharmacology ; Drug Resistance, Neoplasm ; Humans ; Leukemia ; drug therapy ; enzymology ; RNA, Messenger ; analysis ; Tumor Cells, Cultured