Local ablation disrupts immune evasion in pancreatic cancer [RNA-seq 2]

Pancreatic cancer (PC) is a devastating disease characterised by late diagnosis, genetic neoplastic heterogeneity, poor T-cell infiltration, a highly immunosuppressive tumour microenvironment, and metastatic spreading which results in poor clinical outcomes. Surgery remains the most effective treatment, although it is limited to a few patients. Local ablative techniques, such as radiofrequency ablation (RFA), have been proposed to control PC progression in patients with nonresectable tumours. However, the impact of these therapies on promoting the activation of the immune system and eliciting an effective anti-tumour immune response remains elusive. Whether local ablative techniques could overcome resistance to immunotherapy in PC is unknown. We enrolled a cohort of patients with non-resectable locally advanced pancreatic cancer and longitudinally evaluated the impact of local thermal ablation on circulating immunological parameters. Additionally, we used cancer cell lines derived from PC transgenic mouse models to establish a preclinical platform that recapitulates systemic and localised inflammation induced by RFA in vivo. Finally, we employed this preclinical experimental platform to evaluate the efficacy of the therapeutic treatments. Thermal ablation induced a short-term inflammatory process resulting in a systemic increase in myeloid cells as well as increased plasma levels of high mobility group box 1 molecule, which correlates with a better patient outcome. We performed thermal ablative procedures in mice bearing orthotopic PC and evaluated the therapeutic efficacy of thermal treatment alone or in combination with immune checkpoint-based immunotherapy through activation of a T lymphocyte-dependent anti-tumour immune response. We demonstrated that RFA synergises with immunotherapy to restrict tumour progression, significantly improving the overall survival of PC-bearing mice. Tumour immune landscape characterisation confirmed that RFA in combination with immunotherapy supported the sculpting of an immune hostile milieu towards an effective anti-tumour milieu characterised by an increased infiltration of cytotoxic T lymphocytes in spite of CD206-expressing tumour-associated macrophages. Our study confirmed that RFA enhances immunotherapy effectiveness by breaking tumour immune tolerance and unleashing the full cytotoxic abilities of tumour-specific T-cells. Thus, RFA can circumvent the current limitations of immunotherapy in patients with pancreatic cancer. Overall design: Comparison of gene expression profile of KPC-derived PDAC treated with RFA compared to untreated control. Tumor samples were collected 48h after treatment.

胰腺癌（Pancreatic cancer, PC）是一种致死性极强的恶性疾病，其特征为确诊时机较晚、肿瘤遗传异质性显著、T细胞浸润匮乏、存在高度免疫抑制的肿瘤微环境，且易发生转移扩散，最终导致患者临床预后极差。手术仍是目前最有效的治疗手段，但仅适用于少数患者。针对不可切除肿瘤患者，已有研究提出采用射频消融（radiofrequency ablation, RFA）等局部消融技术以控制胰腺癌进展。然而，此类疗法对免疫系统激活的促进作用，以及能否诱导有效的抗肿瘤免疫应答，目前仍不明确；局部消融技术是否能够克服胰腺癌对免疫治疗的耐药性，尚且未知。

本研究纳入了一组不可切除的局部晚期胰腺癌患者，纵向评估了局部热消融对循环免疫学参数的影响。此外，我们利用源自胰腺癌转基因小鼠模型的癌细胞系，构建了可复现射频消融在体内诱导的全身及局部炎症反应的临床前研究平台。最后，我们借助该临床前实验平台评估了相关治疗方案的疗效。

热消融可诱导短期炎症反应，使循环髓系细胞数量升高，同时血浆中高迁移率族蛋白B1的水平上升，该指标变化与患者更好的预后相关。我们在携带原位胰腺癌的小鼠中实施热消融操作，并通过激活T淋巴细胞依赖性抗肿瘤免疫应答，评估了单一热疗或联合基于免疫检查点的免疫治疗的疗效。研究结果显示，射频消融可与免疫治疗协同抑制肿瘤进展，显著延长荷瘤小鼠的总生存期。对肿瘤免疫景观的分析证实，射频消融联合免疫治疗可将免疫抑制性微环境重塑为有效的抗肿瘤微环境，其特征为细胞毒性T淋巴细胞浸润显著增加，即便同时存在表达CD206的肿瘤相关巨噬细胞。

本研究证实，射频消融可通过打破肿瘤免疫耐受，充分激活肿瘤特异性T细胞的细胞毒活性，从而增强免疫治疗的疗效。因此，射频消融能够克服当前胰腺癌患者免疫治疗所面临的局限性。

总体研究设计：对比经射频消融处理与未处理的对照组KPC源性胰腺导管腺癌的基因表达谱。肿瘤样本于治疗后48小时采集。