Erastin Induces Ferrotposis in Multiple Myeloma Cells through SLC7A11-IRF1-Txn Axis

Introduction:Multiple myeloma (MM) is the second most common hematological malignancy characterized by genetic heterogeneity. Ferroptosis is a newly defined form of regulated cell death with promising antitumor results in some cancers, while the relationship between MM and ferroptosis remains largely unclear. One of the most important ferrotposis defence pathway is the SLC7A11-GSH-GPX4 axis, here we observed erastin inhibits thioredoxin(TXN) and finally lead to ferrotposis in MM cells. TXN as a essential oxidative stress molecular play a part in cellar pathways, but how it effects ferroptosis is still unknown. Our research show that TXN is the key molecular in the pathway which protect MM cells from ferroptosis, erastin inhibits TXN via promoting inhibiting transcription factor of TXN-IRF1, leading to cell death. Targeting TXN is a novel and promising therapeutic approach to improve the outcome of MM.

Aim: To determine whether TXN acts as a protector in ferroptosis, if so, address the mechanism.

Metods: We explored the expression of TXN in MM patients by GEO database and our clinical samples to study its expression level and indirect effects in survival. Detecting the cells proliferation and lipid peroxidation level in MM cells after knockdown TXN by siRNA and TXN inhibitor Ferroptocide treatment to determine whether ferroptosis is truly happened. Salvage agent Ferrostatin-1(Fer-1) was also used to verify the occurrence of ferroptosis. We treated the MM cell lines (RPMI8226 and MM.1S) with erastin to inhibited SLC7A11 and observed the expression of TXN to explore the relationship between SLC7A11 and TXN. Jasper database was used to find out the key transcription factor of TXN, and we performed ChIP to verify the direction effect of TFs and TXN. After confirm the TF of TXN is interferon regulatory factor 1(IRF1), we employed to siRNA of IRF1 to test its impact on TXN and expression of IRF1 after erastin.

Results: Using GEO database and our clinical samples we show TXN, as an adverse prognostic factor, is high expression in MM which leads to poor survival. After siRNA transfection and Ferroptocide treatment in RPMI8226 and MM.1S cell lines, cells proliferation was significantly inhibited (P<0.05), and lipid peroxidation levels were increased(P<0.05), which could be restrained by Fer-1, indicating the occurrence of ferroptosis. Treatment of MM cell lines with the ferroptosis inhibitor erastin resulted lower expression of TXN in both mRNA level and protein level. Using Jasper database, we locked several TFs of TXN, and ChIP analyse showed that IRF1 could direct affect with TXN. We confirmed expression of TXN increased after inhibit the IRF1 by siRNA, indicating inhibition role of IRF1 to TXN. After confirming the TF, we treating MM cells with erastin and tested the IRF1 expression change, the results showed the IRF1 expressed higher, which indicate erastin inhibiting SLC7A11 to promote IRF1 leading to decreased expression of TXN.

Conclusion: TXN is involved in redox reactions and acts as a ferroptosis inhibitor, protecting MM cells from ferroptosis and enhancing their resistance. Inhibiting the expression or function of TXN can increase MM cell death through ferroptosis, SCL7A11-IRF1-TXN axis is a new ferroptosis defensive pathway could protect cell from death. TXN is a potential key molecule in regulating ferroptosis and targeting TXN is a novel and promising therapeutic approach to improve the outcome of MM.

No relevant conflicts of interest to declare.