A Study On Regulation Of Folate Receptor β By All-Trans Retinoic Acid And Its Mechanism

Background Folate receptors(FR)are proteins on membrane of cells with high affinity,which mediate internalization and allows intake of folic acid to cytoplasm of eukaryotic cells.Its highly expression on tumor cells makes it potential in molecular targeted therapies of cancers,thus investigation on regulation of folate receptor expression is highly significant.Purpose To study if all-trans retinoic acid(ATRA)regulate FRβexpression in KG-1cells and its mechanism of action.Study Design:1.to study the effect of ATRA on FR-βprotein expression in KG-1 and other cells.2.to study the effect of ATRA on FR-βmRNA expression.3. To study the gateway of ATRA and other proliferative agents on gene expression of folate receptor.Methods The effect of ATRA with different concentration at different time on FR-βprotein expression by use of folic acid combination experiment,flow cytometry,Western Blot,FR-βmRNA expression was detected with real time RT-PCR.Further,the gateway of ATRA activity on FR-βexpression in nucleus was studied by a panel of retinoid activators and inhibitors.Results 1,ATRA is capable of up-regulating FR-βprotein expression in KG-1cells,with dose dependent in certain range of concentration(10^-9mol/L～10^-6mol/L);however,ATRA cannot regulate FR-βprotein expression in KG-1a, NB4,HL60,293,L1210,JAR,Hela cells based on our results.2,FR-βexpression was higher when ATRA,at 10^-6mol/L,co-cultured with KG-1 cells for 5 days,while it went down to baseline when clear the ATRA in the medium,like reversible.3.Retinoid receptor RARαactivator CD336 and RARγactivator CD2781 were capable of inducing FR-βexpression.Conclusions:1.ATRA can reversibly up-regulate FR-βprotein in KG-1 cells, with dose dependent in a certain range of concentration.2.ATRA can up-regulate FR-βmRNA expression.3.The regulation of FR-βexpression by ATRA in KG-1 cells might be associated with retinoid receptor RARαand RARγ,rather than RARβand RXRs.