背景:在过去的十年中,癌症免疫疗法彻底改变了黑色素瘤的治疗方法;然而,不同患者人群的反应各不相同。最近,在接受免疫检查点抑制剂治疗的黑色素瘤患者中,基线肿瘤大小已被确定为总生存期的独立预后因素.MG1是一种具有广泛肿瘤嗜性的新型溶瘤药物,最近已进入早期临床试验。这项研究的目的是表征MG1治疗后人类和小鼠黑色素瘤模型中的T细胞反应,并确定在两种不同肿瘤负荷下肿瘤免疫微环境(TIME)的特征是否会影响溶瘤病毒疗法的功效。
方法:进行人三维体外引发测定以测量MG1感染后的抗肿瘤和抗病毒T细胞应答。T细胞受体(TCR)测序,T2杀伤试验,和肽召回分析用于评估TCR库的演变,并测量特定的T细胞反应,分别。在体内,皮下4434黑色素瘤使用RNA测序进行表征,免疫组织化学,和流式细胞术。肿瘤内MG1的有效性在推进4434肿瘤中进行了评估,并通过脾细胞回忆测定法测量了抗肿瘤和抗病毒T细胞的产生。最后,在4434例晚期肿瘤中研究了MG1和程序性细胞死亡蛋白-1抗体(αPD-1)的联合治疗。
结果:MG1有效地支持功能性细胞毒性T细胞(CTL)针对肿瘤相关抗原以及病毒衍生肽的启动,如使用肽召回和T2杀伤分析评估,分别。TCR测序显示,与对照相比,MG1引发的CTL包含更大的相似CDR3氨基酸序列簇。MG1的体内测试表明,MG1单一疗法在治疗早期疾病方面非常有效,导致90%的治愈;然而,MG1的疗效随着疾病负担(局部肿瘤大小)的增加而降低,在更晚期的疾病中,需要添加αPD-1来克服耐药性。差异基因表达谱显示,肿瘤负荷增加与免疫学上较冷的TIME相关。此外,与较小的肿瘤相比,在进展肿瘤中的TCR信号分析显示了TCR参与的不同动态,特别是CD4+细胞的抗原识别发生了变化,从常规子集到监管子集。
结论:需要向MG1中添加αPD-1以克服免疫学上“较冷”更晚期黑色素瘤的病毒治疗耐药性,强调肿瘤负担对不同类型免疫治疗的重要性。
BACKGROUND: Over the past decade, cancer immunotherapies have revolutionized the treatment of melanoma; however, responses vary across patient populations. Recently, baseline tumor size has been identified as an independent prognostic factor for overall survival in patients with melanoma receiving immune checkpoint inhibitors. MG1 is a novel oncolytic agent with broad tumor tropism that has recently entered early-phase clinical trials. The aim of this study was to characterize T-cell responses in human and mouse melanoma models following MG1 treatment and to establish if features of the tumor immune microenvironment (TIME) at two distinct tumor burdens would impact the efficacy of oncolytic virotherapy.
METHODS: Human three-dimensional in vitro priming assays were performed to measure antitumor and antiviral T-cell responses following MG1 infection. T-cell receptor (TCR) sequencing, T2 killing assay, and peptide recall assays were used to assess the evolution of the TCR repertoire, and measure specific T-cell responses, respectively. In vivo, subcutaneous 4434 melanomas were characterized using RNA sequencing, immunohistochemistry, and flow cytometry. The effectiveness of intratumoral MG1 was assessed in advancing 4434 tumors and the generation of antitumor and antiviral T cells measured by splenocyte recall assays. Finally, combination MG1 and programmed cell death protein-1 antibody (αPD-1) therapy was investigated in advanced 4434 tumors.
RESULTS: MG1 effectively supported priming of functional cytotoxic T cells (CTLs) against tumor-associated antigens as well as virus-derived peptides, as assessed using peptide recall and T2 killing assays, respectively. TCR sequencing revealed that MG1-primed CTL comprised larger clusters of similar CDR3 amino acid sequences compared with controls. In vivo testing of MG1 demonstrated that MG1 monotherapy was highly effective at treating early disease, resulting in 90% cures; however, the efficacy of MG1 reduced as the disease burden (local tumor size) increased, and the addition of αPD-1 was required to overcome resistance in more advanced disease. Differential gene expression profiles revealed that increased tumor burden was associated with an immunologically colder TIME. Furthermore, analysis of TCR signaling in advancing tumors demonstrated a different dynamic of TCR engagement compared with smaller tumors, in particular a shift in antigen recognition by CD4+ cells, from conventional to regulatory subsets.
CONCLUSIONS: Addition of αPD-1 to MG1 is required to overcome viral therapy resistance in immunologically \'colder\' more advanced melanoma, highlighting the importance of tumor burden to different types of immunotherapy.