The Combination Efficacy Of Rk1 And Docetaxel For Treatment Of Castration-resistant Prostate Cancer

Androgen deprivation therapy(ADT)is the mainstay treatment for metastatic and advanced prostate cancer.ADT is effective initially treatment,however,after a period of 2-3 years of remission,almost all patients would progress to lethal castration-resistant prostate cancer(CRPC)within 16-18 months.Currently,next-generation androgen receptor(AR)signaling pathway inhibitors have been approved for the treatment of CRPC,such as the CYP17A1 inhibitor Abiraterone,which targets a critical enzyme in the androgen synthesis pathway,and Enzalutamide,an AR antagonist.Although these drugs can prolong the overall survival of patients,they are often associated with limited therapeutic efficacy and the development of drug resistance.In 2004,the US Food and Drug Administration(FDA)approved Docetaxel(DTX)as a first-line chemotherapy drug for CRPC.DTX stabilizes microtubules,resulting in inhibition of cellular transport,mitotic arrest,and apoptosis.In addition,DTX interacts with the androgen signaling pathway in prostate cancer cells as well,inhibiting AR nuclear translocation and thereby reducing the expression of AR target genes.While DTX has been shown to increase patient survival rates,however,only approximately 50% CRPC patients respond to DTX during initial treatment.Additionally,the efficacy of DTX is limited by drug resistance,with nearly all patients developing resistance within 6-8 months.In CRPC patients,the emergence of AR-Vs represents a key driver of DTX resistance.Therefore,developing a drug that specifically targets AR-Vs and using it in combination with Docetaxel represent a promising approach for the treatment of CRPC.Ginsenoside Rk1,a rare ginsenoside derived from ginseng,has shown promising antitumor activity in various cancers.However,its potential therapeutic role in prostate cancer is not yet clear.Therefore,the main objectives of this experiment were as follows:(1)to assess whether ginsenoside Rk1 has anticancer activity against CRPC cell lines and to investigate its anticancer mechanism;(2)to assess whether the combination of ginsenoside Rk1 and docetaxel can enhance the efficacy of docetaxel.In this study,the anti-tumor effect of Rk1 was tested using a prostate cancer cell line.Rk1 was detected to inhibit the proliferation of CRPC cell lines using the SRB method and was androgen independent.Overexpression of AR-FL or AR-V7 in22Rv1 cells was found to partially rescue the inhibitory effect of Rk1 on cell proliferation.Then Rk1 was detected to inhibit AR transcriptional activity using a luciferase reporter gene approach,and also specifically inhibited the transcriptional activity of AR-Vs and AR-V7.Rk1 was detected to down-regulate AR m RNA and a series of AR-Vs m RNA levels,as well as PSA,KLK2,UBE2 C and CCNA2 m RNA levels,in both cell lines using real-time fluorescence quantitative PCR.Using the luciferase reporter gene method again,Rk1 was detected to inhibit not only AR promoter activity but also AR N-C terminus binding.Then using the Western Blot method,it was detected that Rk1 could down-regulate the level of AR protein and also accelerate the degradation of AR protein through the proteasome pathway.The anti-tumor effect of the combination of Rk1 and docetaxel on CRPC cell lines was then assayed.Rk1 was detected to enhance the proliferation inhibition of CRPC cells by docetaxel using the SRB method.The effect of the combination of the two drugs on AR transcriptional activity was examined using a luciferase reporter gene assay,and Rk1 was found to enhance the inhibitory effect of docetaxel on AR transcriptional activity in the presence or absence of androgens.In addition,using real-time fluorescence quantitative PCR,Rk1 enhanced the inhibitory effect of docetaxel on PSA and KLK2 m RNA levels in the presence or absence of androgens.Finally,the tumor suppressive effects of Rk1 and docetaxel were further examined in nude mice.We found that Rk1 and docetaxel alone could inhibit tumor growth,and when Rk1 was combined with DTX,Rk1 significantly increased the antitumor effect of docetaxel.Using Western Blot,we detected that Rk1 could down-regulate the protein levels of AR-FL and AR-Vs in tumors,and DTX could down-regulate the protein levels of AR-FL in tumors,and when Rk1 was co-administered with DTX,Rk1 could significantly increase the down-regulation of AR-FL by docetaxel.In summary,our experimental results demonstrate that Rk1 can suppress tumor growth by targeting the AR signaling pathway,while enhancing the antitumor effect of docetaxel.Our findings provide a strong theoretical basis for clinical evaluation of the combination of Rk1 and docetaxel in the treatment of CRPC.