Leukemia Stem Cell Targeted Therapy Resistance Reversal

The true reason for multi-drug resistence and relapse in leukemia treatment is the existent of leukemia stem cells(LSC).LSC is at the starting stage by few proportion in all stem cells and they can reproduce and differentiate as normal stem cells,but their differentiation often stop before come to the end with disorder regulation.These dysfunctional LSCs will reproduce in large numbers and lead leukemia at last.Above 95%LSCs were dormancy at Go period which is conflict to the mechanism of chemistry therapy drugs.Most chemistry therapy drugs act on the ceils during active periods just like tumor cells.At the same time,multi-drug resistence relative gene MRP was over-expressed in the LSCs.These explain why the LSCs can escape from the chemotherapy and the survival how to induce leukemia.These also indicate that the way for leukemia radical cure is to eliminate the LSCs and protect the normal stem cells.We develop our research on LSC treatment from two aspects baseing on discovery above:1,Interleukin 3 receptorαchain(IL-3Rα) namely CD123 high expressed on the LSC surface while it almost didn't expressed on normal stem cell surface by investigate the LSC surface special antigen.IL-3Rαis the part of IL-3R to combine the interleukin 3.CD123 can be the target for LSC treatment.Lidamycin(LDM) is an enediyne antitumor antibiotic with potent cytotoxicity ag -ainst varieties of cancer cell lines.It is considered as one of the most effective natural products with antitumor biological activity found in recent years.LDM is composed of LDC and LDP by non-covalent bond.Lidamycin is highly active to muti-drug resistant cancer cells.The chemosensitivity of those resistant cancer cells to lidamycin is approximately at the similar level as that of parent cancer cells.To construct fusion protein IL3-G4S-LDP and study on its high expression in E.Coli and its biological activity.Two gene fragments of IL3 and LDP were amplified by PCR.After enzymatic digestion and T4 ligation,the fusion gene was cloned into expression vector pAYZ.The fusion protein was efficiently expressed by pAYZ-IL3LDP transformed into E.Coli 16C9 with AP5 induced.The product was purified by cation exchange chromatography and anti-Etag affinity chromatography. Then it was analyzed bv SDS-PAGE and Western blot.Its biological activity was detected by FACS.The data of DNA sequence showed that the fusion protein was corrected and its coding region was 849bps.The fusion protein expressed as soluble protein.The expression level of it in 1L flask reached 1.5mg/L and its purity was over 95%.Furthermore,the fusion protein was capable of binding to CD123 on cell surface as shown by FACS.It can be used to carry cytotoxin to target cells.2,PHⅡ-7 is one of derivatives ofoxindole which designed and synthesized by our research group.The data showed that PHⅡ-7 inhibited the proliferation of various human tumor cells.Especially,PHⅡ-7 had the same antitumor effect on various MDR tumor cells in vitro.PHⅡ-7 can also down-regulated the expression of mdr1 and Sorcin which suggest that must be happened on MRP.The anti-tumor mechanism of PHⅡ-7 is to arrest cell cycles of a panel of tumor cell lines.We can conclud that PHⅡ-7 seems to be a promising anti-MDR tumor agent.We study the mechanism of synthetic anti-tumor effect of PHⅡ-7 with doxorubic -in to multidrug resistant leukemia cell line HL60/ADR and its parent cell line HL60. The synthetic anti-tumor effect on HL60/ADR is higer than HL60.The RNA extracted from the cells treated by PHⅡ-7 imply the down-regulate effect of PHⅡ-7 on the exp -ression of MRP gene in a dose and time dependent manner.The cumulation of doxor -ubicin in HL60/ADR cells restored from 22.4%to 55%after be treated 96 hours by PHⅡ-7.Finding LSC make researchers know the essence of happen,develop,drug-resis -tence and relapse for leukemia.To eliminate the LSC is the right way to radical cure the leukemia.Our study about CD123 and PHⅡ-7 is the base for leukemia treatment.