The Effects Of Ultraviolet Radiation On The Proliferation And The Expression Of Five Multidrug Resistance Relative MicroRNAs Of HL-60Cells

Objective: To observe the effects of ultraviolet (UV) radiation on theproliferation and the expression of five multidrug resistancerelative microRNAs (miRNAs) of acute promyelocyticleukemia (APL) cell line HL-60, and explore its potentialclinical significance.Methods: The DNR-sensitive HL-60cells were routinely cultured. TheDNR-resistant HL-60cells were induced with a small dose ofdaunorubicin (DNR). The UV group1DNR-sensitive andUV group2DNR-resistant cells were irradiated with254nmUV radiation. The inhibition rate of HL-60cells treated withDNR was estimated by using dimethylthiazoldiphenyltetrazolium (MTT) assay. The proliferation of cellswas detected by using trypan blue staining. The expression ofmiRNA-21, miRNA-125b, miRNA-27a, let-7f andmiRNA-181d were analyzed by using reverse transcriptionpolymerase chain reaction (RT-PCR).Results:1. The preparation of HL-60DNR-resistant cells: HL-60DNR-sensitive cells would generate DNR resistance after induction with8ng/ml DNR. The inhibition rate of DNR onDNR-sensitive cells declined day by day. But the inhibitionrate would not decline again and enter a period of plateauafter about the10th day of DNR induction, which indicatedthat DNR-sensitive cells had generated some DNRresistance. HL-60cells induced with DNR for1monthwere used as DNR-resistant cells for the next experiments;2. The effect of UV radiation on the proliferation of HL-60cells: the proliferation of DNR-sensitive HL-60cells couldbe inhibited after they were irradiated once with2-6mJ UV.The cells would completely die when the DNR-sensitivecells were irradiated once with15mJ UV or twice (onceevery5days) with2-10mJ UV, or when the DNR-resistantcells were irradiated once with20mJ UV. But theDNR-resistant cells could recover proliferation on the15thday after they were irradiated once with15mJ UV. Theproliferation of DNR-sensitive and resistant cells waspartially inhibited if they were irradiated only once with10mJ UV. Their mortality rate would reach the highestvalue on the3rd day after UV irradiation. But the mortalityrate of DNR-resistant cells were lower than those ofDNR-sensitive cells (P<0.05). Additionally, DNR-resistantcells could recover proliferation on the7th day after UVirradiation, but the DNR-sensitive cells would need morethan10days to recover proliferation;3. The inhibition rate of DNR on HL-60cells irradiated with UV light: On the1st and3rd day after10mJ UV irradiationonce, the inhibition of DNR on DNR-sensitive cells withUV irradiation was lower than that on DNR-sensitive cellswithout UV irradiation (P<0.05). On the5th day after10mJUV irradiation once, the inhibition of DNR onDNR-sensitive cells with UV irradiation would return tothat of the DNR-sensitive cells without UV irradiation(P>0.05). From the1st day to the10th day, the inhibitionrate of DNR on DNR-resistant cells with10mJ UVirradiation once was lower than that of DNR-sensitive andresistant cells without UV irradiation (P<0.05);4. The expression of miRNA in HL-60cells: Comparing withthe DNR-sensitive cells, the expression of miRNA-21andmiRNA-125b in the DNR-resistant cells were obviouslyup-regulated (P<0.05), whereas the expression ofmiRNA-181d, miRNA-27a and let-7f were obviouslydown-regulated (P<0.05). Comparing with the controls, theexpression of miRNA-21in the cells of UV groups1and2were obviously up-regulated on the1st day after10mJ UVradiation once (P<0.05), and then, the expression ofmiRNA-21reduced to the level of controls on the6th dayand10th day after10mJ UV radiation once. The expressionof let-7f and miRNA-27a in the cells of UV groups1and2,especially UV group2, were obviously up-regulated on the1st day after10mJ UV radiation once (P<0.05). Althoughthe expression of let-7f and miRNA-27a in the cells of both UV groups1and2decreased on the6th and10th day after10mJ UV radiation once, and the expression of let-7f andmiRNA-27a in the cells of UV groups1was close to thelevel of control group, but the expression of let-7f andmiRNA-27a in the cells of UV groups2was stillsignificantly higher than that of control group (P<0.05).The expression of miRNA-125b in the cells of UV groups1and2had little change on the1st day after10mJ UVradiation once (P>0.05), but significantly increased on the6th and10th day after10mJ UV radiation once (P<0.05).The expression of miRNA-181d in the cells of UV group1reduced slightly on the6th and10th day after10mJ UVradiation once (P<0.05), the expression of miRNA-181d inthe cells of UV group2had only little change on the1stand10th day after10mJ UV radiation once (P>0.05), butsignificantly decreased on the6th day after10mJ UVradiation once (P<0.05).Conclusion: UV radiation has a significant killing effect on bothDNR-sensitive and resistant cells, especially on theDNR-sensitive cells, but small-dose UV radiation maymake HL-60cells, especially the DNR-resistant cellsbecome more resistant to DNR. In addition, UV radiationhad significant impacts on the expression of miRNA-181d,miRNA-21, miRNA-125b, let-7f and miRNA-27a in theDNR-sensitive and resistant cells, indicating that these5miRNAs are not only involved in the formation of multidrug resistance of HL-60cells, but might alsoparticipate in the response to UV damage and the repair ofUV damage of HL-60cells. These findings may have somereference values for the therapy of APL with UV radiationand RNAi technique in the future.