背景:新数据表明,程式化死亡配体1(PD-L1)表达增加的恩杂鲁胺治疗的前列腺癌患者可能受益于抗PD-L1治疗。不幸的是,IMbassor250III期临床试验显示,阿特珠单抗(一种PD-L1抑制剂)和恩杂鲁胺联合应用未能延长去势抵抗性前列腺癌(CRPC)患者的总生存期.然而,治疗失败的潜在机制仍然未知.
方法:将人CRPCC4-2B细胞和鼠Myc-CaP细胞长期暴露于浓度增加的恩杂鲁胺中,对恩杂鲁胺有抗性的细胞称为C4-2BMDVR和Myc-CaPMDVR,分别。使用RNA测序分析确定了耐药前列腺癌细胞的作用机制,RNA干扰,实时PCR,西方印迹,和共同培养技术。Myc-CaP和Myc-CaPMDVR肿瘤在同基因FVB小鼠中建立,和肿瘤浸润的白细胞在恩杂鲁胺治疗后分离。通过流式细胞术测定染色的免疫细胞。并使用FlowJo对数据进行分析。
结果:免疫相关信号通路(干扰素α/γ反应,炎症反应,和细胞趋化性)在人抗恩杂鲁胺前列腺癌细胞中受到抑制。在耐药细胞和CRPC患者队列中,PD-L1过表达并受到雄激素受体信号传导的负调控。恩扎鲁胺治疗减少了CD8+T细胞数量,但增加了小鼠Myc-CaP肿瘤中的单核细胞髓源性抑制细胞(M-MDSC)群体和PD-L1表达。同样,趋化性和免疫反应调节信号通路被抑制,使用耐恩杂鲁胺的Myc-CaPMDVR细胞,PD-L1表达也增加。值得注意的是,与Myc-CaP亲本肿瘤相比,Myc-CaPMDVR原位肿瘤中的MDSC群体显着增加。骨髓细胞与Myc-CaPMDVR细胞共培养可显着促进MDSC分化并向M2巨噬细胞偏斜转变。
结论:我们的研究表明,恩杂鲁胺耐药前列腺癌细胞可以直接促进免疫抑制信号传导,并且可能是免疫检查点抑制剂在恩杂鲁胺耐药前列腺癌中的疗效降低的潜在手段。
Emerging data suggest that patients with enzalutamide-treated prostate cancer with increased programmed death-ligand 1 (PD-L1) expression may benefit from anti-PD-L1 treatment. Unfortunately, the Phase III IMbassador250 clinical trial revealed that the combination of atezolizumab (a PD-L1 inhibitor) and enzalutamide failed to extend overall survival in patients with castration-resistant prostate cancer (CRPC). However, the mechanisms underlying treatment failure remain unknown.
Human CRPC C4-2B cells and murine Myc-CaP cells were chronically exposed to increasing concentrations of enzalutamide and the cells resistant to enzalutamide were referred to as C4-2B MDVR and Myc-CaP MDVR, respectively. The mechanisms of action in drug-resistant prostate cancer cells were determined using RNA sequencing analyses, RNA interference, real-time PCR, western blotting, and co-culturing technologies. Myc-CaP and Myc-CaP MDVR tumors were established in syngeneic FVB mice, and tumor-infiltrating leukocytes were isolated after enzalutamide treatment. The stained immune cells were determined by flow cytometry, and the data were analyzed using FlowJo.
Immune-related signaling pathways (interferon alpha/gamma response, inflammatory response, and cell chemotaxis) were suppressed in human enzalutamide-resistant prostate cancer cells. PD-L1 was overexpressed and negatively regulated by androgen receptor signaling in resistant cells and patient with CRPC cohorts. Enzalutamide treatment decreased CD8+ T-cell numbers but increased monocytic myeloid-derived suppressor cell (M-MDSC) populations and PD-L1 expression within murine Myc-CaP tumors. Similarly, chemotaxis and immune response-regulating signaling pathways were suppressed, and PD-L1 expression was also increased using enzalutamide-resistant Myc-CaP MDVR cells. Notably, MDSC populations were significantly increased in Myc-CaP MDVR orthotopic tumors compared with those in Myc-CaP parental tumors. Co-culturing bone marrow cells with Myc-CaP MDVR cells significantly promoted MDSC differentiation and shifted towards M2 macrophage skewing.
Our study suggests that immunosuppressive signaling can be promoted directly by enzalutamide-resistant prostate cancer cells and may be a potential means by which the efficacy of immune checkpoint inhibitors in enzalutamide-resistant prostate cancer is diminished.