Abstract

Background

Current hepatocellular carcinoma (HCC) immunotherapy trials only yield modest outcome, suggesting that possibly strong intrinsic immunosuppressive network needed to be tackled. Conventional chemotherapies are found to exert immunomodulatory effect on the tumor microenvironment (TME). Our study investigated anti-tumor activity of 5-FU in combination with anti-PD-L1, using pre-clinical HCC mouse model, and evaluated the immunomodulation in TME after drug treatments.

Methods

For the orthotopic HCC in vivo experiment, 6-8-week-old male C57BL/6 mice were injected intrahepatically with 5x10^⁵ RIL-175 luc+ cells. In order to assess its immunomodulatory effect on HCC TME rather than on direct tumor-killing effect, 5-FU was administrated (i.p.) 3 times per week at a relative low dose—20mg/kg. Whilst, anti-PD-L1(10mg/kg) was delivered (i.p.) every 5 days. Tumor growth was monitored via in vivo imaging. Tumor, liver, spleen and blood was collected afterwards, followed by immune profiling analysis via flow cytometry.

Results

In terms of in vivo imaging results, mice with single anti-PD-L1 treatment showed significant response in tumor growth amongst other groups. Meanwhile 5-FU monotherapy and combined treatment group showed no difference with vehicle group. We found an increased amounts of T lymphocytes and NK cells in the tumor site after anti-PD-L1 single treatment, suggesting that these immune active cells contributed to the anti-tumor effect. Tumor-infiltrating myeloid cells, particularly P-MDSC, elevated upon 5-FU treatment in both single and combined group, suggesting that they may play a role in mediating immunosuppression.

Conclusion

This study illustrated that anti-PD-L1 monotherapy enriched tumor-infiltrating T lymphocytes and NK cells, possibly accounting for the deferred tumor growth. However, the accumulation of myeloid cells in 5-FU treated mice hinders the anti-tumor activity of anti-PD-L1 from this orthotopic HCC mouse model. Therefore, low dose of 5-FU may initiate immunosuppressive mechanism to alter the effectiveness of anti-PD-L1 in HCC.

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.

中文翻译：

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化疗药物150P的肿瘤内MDSC募集，5-FU抵消了HCC免疫检查点抑制剂的抗肿瘤活性

抽象的

背景

当前的肝细胞癌（HCC）免疫疗法试验仅产生适度的结果，表明可能需要解决强大的内在免疫抑制网络。发现常规化学疗法对肿瘤微环境（TME）发挥免疫调节作用。我们的研究使用临床前HCC小鼠模型研究了5-FU与抗PD-L1组合的抗肿瘤活性，并评估了药物治疗后TME中的免疫调节作用。

方法

对于原位HCC体内实验，向6-8周龄的雄性C57BL / 6小鼠肝内注射5×10 ⁵ RIL-175 luc +细胞。为了评估其对HCC TME的免疫调节作用，而不是对直接的肿瘤杀伤作用，以相对较低的剂量（20mg / kg）每周3次（ip）施用5-FU。同时，每5天递送（ip）抗PD-L1（10mg / kg）。通过体内成像监测肿瘤的生长。随后收集肿瘤，肝脏，脾脏和血液，然后通过流式细胞仪进行免疫谱分析。

结果

就体内成像结果而言，采用单抗PD-L1处理的小鼠在其他组中显示出对肿瘤生长的显着反应。同时5-FU单药联合治疗组与媒介物组无差异。我们发现抗PD-L1单一治疗后肿瘤部位的T淋巴细胞和NK细胞数量增加，表明这些免疫活性细胞有助于抗肿瘤作用。在单个或联合组中，经5-FU处理后，肿瘤浸润性髓样细胞，特别是P-MDSC升高，表明它们可能在介导免疫抑制中发挥作用。

结论

这项研究表明，抗PD-L1单一疗法可丰富肿瘤浸润性T淋巴细胞和NK细胞，这可能是造成肿瘤延缓生长的原因。但是，5-FU处理的小鼠中髓样细胞的积累阻碍了该原位HCC小鼠模型中抗PD-L1的抗肿瘤活性。因此，低剂量的5-FU可能会启动免疫抑制机制，从而改变抗PD-L1在肝癌中的有效性。

负责研究的法人实体

作者。

资金

尚未收到任何资金。

揭露

所有作者均声明没有利益冲突。