The Function And Mechanism Of Lysine Specific Demethylase 1 In Prostate Cancer

Background and purpose: As of 2021,prostate cancer（PCa）has become the second most common cancer in men,only after lung cancer.And it is the fifth leading cause of cancer death worldwide.Radical surgery is the standard treatment for most patients of PCa.However,androgen-deprivation therapy（ADT）is the first-line treatment currently for advanced PCa patients who cannot be cured by surgery.The common drugs for ADT are abiraterone,enzalutamide and so on.Unfortunately,cancer cells will develop drug resistance after ADT treatment for a period of time.And PCa will further progress into castration resistant prostate cancer（CRPCa）.The prognosis of patients with CRPCa is poor and the treatment is limited.Therefore,it is of great importance to find a new target for treatment.LSD1 is up-regulated in CRPCa and correlated with prognosis.The high-expression LSD1 has been shown to be a potential target for treatment and is widely studied for its demethylase-activity.However,its demethylation-independent function remains to be elusive in PCa.Recent study shows that LSD1 can destabilize cancer suppressor protein FBXW7 without demethylation-function.Hence,we hope to investigate the impact of non-canonical function of LSD1 on PCa cell survival.Methods: In this study,the expression levels of LSD1 and FBXW7 in prostate cancer and adjacent tissues were detected by immunohistochemistry.Spearman correlation coefficient method was used to analyze the expression relationship between LSD1 and FBXW7 in prostate cancer samples.Prostate cancer cell lines LNCa P and PC3 were transfected with small interfering RNA or plasmid,and LSD1 and FBXW7 genes were silenced or over-expressed for function experiments in vitro.Prostate cancer cell lines were treated with gsk-2879552 or sp-2509,which were LSD1 inhibitors with different mechanisms.The protein expression levels of LSD1,FBXW7,c-myc,NOTCH-1 and K661 A were detected by Western blot.The m RNA levels of LSD1 and FBXW7 were detected by q-PCR.Actinomycin D experiment was used to detect the protein degradation rate of LSD1 and FBXW7.Results: Firstly,the immunohistochemical results of clinical specimens of patients with prostate cancer and the Western blot results of corresponding cell lines showed that the expression of LSD1 was up-regulated and the expression of FBXW7 was down regulated in prostate cancer,and this trend was more obvious in prostate cancer specimens with metastasis.Spearman analysis showed that there was a negative correlation between the expression of LSD1 and FBXW7 in prostate cancer specimens.Furthermore,functional experiments in vitro showed that overexpression of FBXW7 could down-regulate the expression levels of oncoproteins c-MYC and NOTCH-1,and inhibit the viability of prostate cancer cells.LSD1 knockdown inhibited the proliferation of cancer cells,decreased the protein level of FBXW7 in cells,and increased the expression levels of c-MYC and NOTCH-1.The rescue experiment showed that the knockdown of FBXW7 could restore the viability of PCa cells with LSD1 knockdown.Next,q-PCR and actinomycin D experiments showed that LSD1 knockdown did not change the m RNA level of FBXW7,but could prolong the half-life of FBXW7 protein.In addition,both wild-type LSD1 and enzyme activity deletion mutant K661 A can inhibit the protein expression of FBXW7 and promote the proliferation of prostate cancer cells.Finally,drug-treatment experiment showed that allosteric inhibitor SP-2509 could decrease the expression of LSD1 to block the interaction between LSD1 and FBXW7,and inhibit cell proliferation.While the inhibitory effect of enzyme activity inhibitor GSK-2879552 was not ideal.Conclusions: In conclusion,this study revealed that the biological functions of LSD1 are diverse.In PCa cells,LSD1 can destabilize FBXW7 and accelerate its degradation through demethylation-independent function,thus promoting the viability of PCa cells.The functional diversity of LSD1 also explains why simple enzyme activity inhibitors are not effective in the treatment of PCa.It also suggests that more attention should be paid to the demethylation-independent function for LSD1 inhibitors study.