[Growth-inhibiting effect of psoralen plus ultraviolet-A light therapy on K562 cells].

Objective: To observe the effects of psoralen plus ultraviolet-A light (PUVA) on K562 cells and the relative mechanism.

Methods: The effects of psoralen, ultraviolet-A light and PUVA on K562 cells were assayed by monotetrazolium test (MTT). DNA content was analyzed by flow cytometry (FCM). The apoptotic rates of K562 cells treated with 40 and 80 microg/ml psoralen for 24 and 48 hours were assayed by Annexin-V-FITC/PI reagent kit on FCM respectively. The ultrastructures of apoptotic cells were observed by a transmission electron microscope (TEM).

Results: Either single psoralen therapy or single ultraviolet-A irradiation had inhibiting effect on K562 cells. The inhibiting effect of PUVA on K562 cells was stronger than that of the single psoralen therapy or single ultraviolet-A light irradiation (P<0.05). Apoptotic peak (AP) was detected by FCM. TEM test showed that K562 cells treated with PUVA were smaller, having condensed cell nucleus, assembled chromatin, disintegrated nucleus body and the majority of the cells appeared to be apoptotic conformation.

Conclusion: Psoralen has inhibiting effect on K562 cells, and the effect of PUVA is more significant. It is suggested that 10 min irradiation and 40 microg/ml terminal concentration of psoralen be probably the best choice for PUVA. The inhibiting effect of PUVA is due to apoptosis.