Roles And Mechanistic Studies Of The SRC-3 In Multiple Myeloma Drug Resistance

Objective 1.To elucidate the role of steroid receptor coactivator-3(SRC-3)in bortezomib(BTZ)induced drug resistance in multiple myeloma(MM).2.To explore the regulatory mechanism of SRC-3 in posttranslational modification and liquid-liquid phase separation during drug resistance of multiple myeloma.3.To verify the mechanism of SI-2 about the anti-drug resistance effect.Methods and results 1.The level of SRC-3 was negatively correlated with the relapsed/refractory myeloma patients after bortezomib(BTZ)-based regimen treatment and positively correlated with the t(4;14)chromosomal abnormality.SRC-3 increased in relapsed/refractory myeloma patients with micro CT,quantitative real-time PCR and follow-up analysis,predicted a poorer progression and worse bone lesion restoration.2.The level of SRC-3 was negatively correlated with the sensitization to BTZ treatment of myeloma cell lines.Higher SRC-3 expression predicted a poorer sensitization to BTZ treatment.SRC-3 was one elevated protein of resistant myeloma cells by SILAC analysis,with 128 elevated proteins.3.NSD2 interacted with SRC-3 as a partner by mass spectrum,immunoprecipitation,PLA assay.NSD2 interacted with AD2 region through the PWWP domain.4.NSD2 promoted the protein agglutination of SRC-3.SRC-3 was characterized by liquid-liquid phase separation with the intrinsically disordered regions(IDR,369?1072 aa and 1085?1424 aa)which is interacted with NSD2.5.The protein agglutination of SRC-3 increased in drug resistant myeloma cells.6.SI-2 impaired the interaction between SRC-3 and NSD2,resulted in the decrease of the protein stability and agglutination of SRC-3 as a consequence.7.SI-2 can weaken the transcriptional elongation and H3K36me2,inhibit the expression of those genes,which related to drug resistance and anti-apoptosis were increased to enhance the drug resistance,including ABC gene family,BCL2,CCL4,CBS,TNC,EGR1 and IGF1 R at al.8.SI-2 altered the sensitization to BTZ treatment of MM,the combination of SI-2 and BTZ can effectively inhibit tumor growth,promote cell death and bone reconstruction,overcame the drug resistance in vitro and in vivo.Conclusion 1.SRC-3 expression predicted a poorer progression and worse bone lesion restoration in the relapsed/refractory myeloma patients,and were positively correlated with the t(4;14)chromosomal abnormality.2.SRC-3 levels were negatively correlated with sensitization to BTZ of myeloma.3.Mechanistically,elevated histone methyltransferase NSD2 interacted with SRC-3 at the intrinsically disordered regions to enhance the phase separation,and modified the H3K36me2 level on promoters of antiapoptotic genes.4.The SRC-3 specific inhibitor,SI-2,could synergeticly sensitize BTZ treatment in MM cells in vitro and overcome drug resistance in vivo.