ALA光动力联合PD-1/PD-L1抑制剂治疗皮肤鳞状细胞癌的效应与机制研究

PD-1/PD-L1 pathway inhibition has made great achievements in cancer therapies; however, the response rate is limited. It is known that ALA-photodynamic therapy (ALA-PDT) can induce effective antitumor immune. In clinical practice, satisfied outcomes of ALA-PDT was achieved in treating superficial and non-invasive squamous cell carcinoma (SCC), but not invasive SCC. In our previous study, treatment of SCC mouse model with ALA-PDT in combination with systemic PD-1/PD-L1 pathway inhibition, instead monotherapy, resulted in significant regression of tumors. We hypothesized that ALA-PDT potentiates systemic efficacy of checkpoint blockade immunotherapies by activating immune systems in tumor microenvironment; specifically by inhibiting PI3K/Akt-STAT3 pathway and decreasing expression of PD-1/PD-L1. Moreover, PD-1/PD-L1 pathway inhibition enhances anti-tumor activity of ALA-PDT by "liberating effector T cells", thus resulting in a "1 + 1> 2" synergistic effect. In order to confirm the hypothesis, we will further explore the efficacy and the mechanism of combined therapy of ALA-PDT and PD-1/PD-L1 inhibition for SCC. Patient samples, mouse SCC models and coculture system of primary tumor cells and cytotoxic T lymphocytes will be used to elucidate the mechanisms. Our study will throw lights on treatment of advanced SCC and provide fundamental evidence on clinical application of ALA-PDT and PD-1/PD-L1 inhibition.

PD-1/PD-L1抗体治疗肿瘤取得突破，但响应率不高是临床难点。我们研究证实ALA-PDT可激发抗肿瘤免疫，临床上对早期非侵袭性皮肤鳞癌（SCC）有效，而对侵袭性SCC疗效欠佳。本课题组前期在小鼠SCC晚期模型研究中发现，使用PD-1/PD-L1抗体联合ALA-PDT比单用任何一种治疗更有效，提示ALA-PDT可协同PD-1/PD-L1抗体治疗SCC。课题组假设ALA-PDT通过改变免疫原性微环境，抑制PI3K/Akt-STAT3通路，增强肿瘤对PD-1/PD-L1抑制剂治疗敏感性；PD-1/PD-L1抑制剂进一步“解放效应T细胞”增强ALA-PDT激发的抗肿瘤免疫效应，最终产生“1+1>2”协同作用。为验证此假设，本课题拟应用临床样本、小鼠鳞癌模型，细胞毒性T淋巴细胞与鳞癌细胞共培养等体系从体内、细胞和分子水平探讨ALA-PDT与PD-1/PD-L1抑制剂联合治疗SCC协同作用的机制。

免疫检查点阻断（Immune Checkpoint Blockade, ICB）是一种强大的肿瘤治疗方式，适用于多种人类恶性肿瘤，但患者对这种治疗的反应率仍然很低，特别是皮肤鳞状细胞癌（cutaneous Squamous Cell Carcinoma, cSCC）患者。5-氨基酮戊酸-光动力疗法（Aminolevulinic Acid Photodynamic Therapy, ALA-PDT）被广泛用于治疗癌前皮肤病，但ALA-PDT在治疗浸润性cSCC方面的疗效尚有争议。我们以前研究表明，ALA-PDT可以通过促进肿瘤细胞的免疫原性死亡诱发抗肿瘤免疫反应。然而目前还不清楚ALA-PDT是否能与ICB在cSCC中发挥协同作用。在此，我们研究了阻断PD-L1能增强ALA-PDT对原发肿瘤和远处肿瘤的抗肿瘤作用，并优化了cSCC的肿瘤免疫微环境。在本课题中我们首先检测了不同分化程度cSCC患者的PD-L1表达。然后我们发现抗PD-L1单克隆抗体和ALA-PDT的联合治疗通过凋亡和铁死亡介导的免疫原性细胞死亡（Immunogenic Cell Death, ICD）杀死肿瘤细胞，刺激全身免疫反应，并建立免疫记忆反应防止肿瘤复发。此外，我们发现联合治疗可招募类似三级淋巴结构（Tertiary Lymphoid Structure, TLS）的瘤内淋巴细胞聚集结构，这可能促进肿瘤浸润淋巴细胞（Tumor-Infiltrating Lymphocyte, TIL）介导的抗肿瘤免疫力。总之，本课题应用临床样本、小鼠模型等体系从体内、细胞、分子水平表明抗PD-L1单克隆抗体和ALA-PDT对cSCC具有协同的抗肿瘤作用。