Studies Of A New Lectin FRIL On The Capability To Maintain Hematopoietic Stem/progenitor Cells In Vitro And Its Mechanism

Ex vivo preservation of HSCs' self-renewal and multipotence by plant lectin is a new strategy for the clinical application of HSC. The studies in this field would be helpful to understand stem cells' self-renewal and the reason of leukemia.We extracted , purified and identified this lectin ,FRIL. In our detection, FRIL may specially target to HSPCs. When CD34+ cells were cultured in the presence of this lectin, within 28 days, most of cells were kept in GO/G1 phase, and their multipotence were maintained properly.To find out the mechanism under FRIL's function, we studied the expression and activation of some molecules which may involve in FRIL receptor's activation , signal transduction and cell cycle control. The result is, FRIL could suppress the phosphorylation and activation of Ras/Raf/MEK/ERK pathway in some degreed, the effort laid in Ras or upstream. As a result , it suppressed the phosphorylation of STAT5, disturb the formation of AP-1 complexity ,thus suppressed the expression or activiation of some cell cycle control proteins. Within these proteins, p53 was positive regulated by FRIL, which may be important to FRIL's effect on cell cycle halting. Abolishing ERK or PI3K pathways could sentence HSPCs to death even with the existent of FRIL, so they must be slightly provoked in FRIL's function. Besides, HOXB4 and HTm4 also involved in FRIL's function to preserving HSPCs in GO/G1 phase. Another work with cells transfected with Flt3 show that FRIL can activate ERK pathway in a low degreed, maybe in this way, FRIL kept HSPCs survival by not proliferation. We have also found another receptor of FRIL by affinity purify and western blot with antibody to FRIL. It may be a new mediate to FRIL's function.In conclusion, FRIL slightly activiated MAPK pathway , in this way , it kept HSPCs self-renewing and maintain their multipotence.