Women's Malignancies Branch, National Cancer Institute, Bethesda, Maryland, USA
Department of Pathology, Johns Hopkins, Baltimore, Maryland, USA.
J Immunother Cancer. 2020 Jul;8(2). doi: 10.1136/jitc-2019-000516.
Preclinical data suggest cell cycle checkpoint blockade may induce an immunostimulatory tumor microenvironment. However, it remains elusive whether immunomodulation occurs in the clinical setting. To test this, we used blood and fresh tissue samples collected at baseline and post therapy from a phase II trial of the cell cycle checkpoint 1 inhibitor (CHK1i) prexasertib in recurrent ovarian cancer.
Paired blood samples and fresh core biopsies, taken before treatment was started at baseline (cycle 1 day 1 (C1D1)) and post second dose on day 15 of cycle 1 (C1D15), were collected. To evaluate changes in the immune responses after treatment, multiparametric flow cytometry for DNA damage markers and immune cell subsets was performed on paired blood samples. RNA sequencing (RNAseq) of paired core biopsies was also analyzed. Archival tissue immune microenvironment was evaluated with immunohistochemistry. All correlative study statistical analyses used two-sided significance with a cut-off of p=0.05.
Flow cytometric analysis showed significantly increased γ-H2AX staining after CHK1i treatment, accompanied by increased monocyte populations, suggestive of an activated innate immune response (median 31.6% vs 45.6%, p=0.005). Increased expressions of immunocompetence marker HLA-DR (Human Leukocyte Antigen DR antigen) on monocytes and of a marker of STING (stimulator of interferon genes) pathway activation, in biopsies were associated with improved progression-free survival (PFS) (9.25 vs 3.5 months, p=0.019; 9 vs 3 months, p=0.003, respectively). Computational analysis of RNAseq data indicated increased infiltration of tumor niches by naïve B-cells and resting memory T-cells, suggestive of a possibly activated adaptive immune response, and greater T-reg infiltration after treatment correlated with worse PFS (9.25 vs 3.5 months, p=0.007). An immunosuppressive adaptive immune response, perhaps compensatory, was also observed on flow cytometry, including lymphodepletion of total peripheral CD4+ and CD8+T cells after CHK1i and an increase in the proportion of T-regs among these T-cells. Additionally, there was a trend of improved PFS with greater tumor-infiltrating lymphocytes (TILs) in archival tissues (13.7 months >30% TILs vs 5.5 months ≤30% TILs, p=0.05).
Our study demonstrates that a favorable clinical response in high-grade serous ovarian carcinoma patients treated with CHK1i is possibly associated with enhanced innate and adaptive immunity, requiring further mechanistic studies. It is supportive of current efforts for a clinical development strategy for therapeutic combinations with immunotherapy in ovarian cancer.
临床前数据表明，细胞周期检查点阻断可能会诱导免疫刺激性肿瘤微环境。然而，在临床环境中是否发生免疫调节仍然难以捉摸。为了验证这一点，我们使用了在复发性卵巢癌中进行的细胞周期检查点 1 抑制剂（CHK1i）prexasertib 的 II 期试验中在基线时和治疗后收集的血液和新鲜组织样本进行检测。
采集基线时（第 1 周期第 1 天（C1D1））和第 1 周期第 15 天（C1D15）第二次给药后开始治疗前的配对血液样本和新鲜核心活检。为了评估治疗后免疫反应的变化，对配对的血液样本进行了用于 DNA 损伤标志物和免疫细胞亚群的多参数流式细胞术分析。还对配对的核心活检进行了 RNA 测序（RNAseq）分析。使用免疫组织化学评估存档组织免疫微环境。所有相关性研究的统计分析均采用双侧显著性检验，截值为 p=0.05。
流式细胞术分析显示，CHK1i 治疗后 γ-H2AX 染色明显增加，同时单核细胞群增加，提示固有免疫反应激活（中位数 31.6% vs 45.6%，p=0.005）。活检中单核细胞上免疫能力标志物 HLA-DR（人类白细胞抗原 DR 抗原）和 STING（干扰素基因刺激物）途径激活标志物的表达增加与无进展生存期（PFS）的改善相关（9.25 与 3.5 个月，p=0.019；9 与 3 个月，p=0.003）。RNAseq 数据的计算分析表明，肿瘤基质中幼稚 B 细胞和静止记忆 T 细胞的浸润增加，提示可能存在激活的适应性免疫反应，并且治疗后 T-reg 浸润增加与较差的 PFS 相关（9.25 与 3.5 个月，p=0.007）。流式细胞术也观察到适应性免疫的抑制作用，包括 CHK1i 后外周血总 CD4+和 CD8+T 细胞的淋巴细胞耗竭以及这些 T 细胞中 T-reg 比例的增加。此外，在存档组织中，肿瘤浸润淋巴细胞（TIL）较多的患者 PFS 有改善趋势（13.7 个月>30%TILs 与 5.5 个月≤30%TILs，p=0.05）。
我们的研究表明，接受 CHK1i 治疗的高级别浆液性卵巢癌患者的良好临床反应可能与固有和适应性免疫增强有关，需要进一步的机制研究。这支持了目前在卵巢癌中进行免疫治疗联合治疗的临床开发策略的努力。
