小细胞肺癌（SCLC）对一线放化疗敏感，但很快耐药复发，致后续治疗效差预后不佳。研究SCLC化疗耐药机制及应对策略是克服治疗瓶颈的关键。普遍认为SCLC耐药与肿瘤干细胞（CSCs）及遗传背景有关，但因缺乏可靠的CSCs筛选标记及可用于深度测序（NGS）组织标本，至今无明显进展。申请者前期证实电压依赖性钙通道受体α2δ1+细胞具有CSCs特性，对化疗耐药。通过全外显子测序，发现新辅助化疗后残留肿瘤表现特征性突变谱，27个基因可能参与SCLC继发耐药。本课题将进一步探讨α2δ1介导CSCs特性及化疗耐药分子调控机制；通过构建原发/继发耐药PDXs模型，NGS前瞻性分析新辅助化疗患者及PDXs化疗前后全外显子与转录组差异，确定耐药候选基因并进行分子机制研究；通过探讨PD1/PD-L1抑制剂与α2δ1特异性抗体1B50-1对CSCs的作用，探讨免疫治疗克服SCLC化疗耐药、根除肿瘤的可能性。

Small cell lung cancer (SCLC) is a systemic disease. Although the initial response to first-line chemo- and radio-therapy, the quickly resistance and recurrence cause the worse prognosis. So the research of resistant mechanisms and coping strategies becomes the key to overcome bottleneck SCLC treatment. The mechanisms related to SCLC resistance is complex. At present, cancer stem cells (CSCs) and genetic background are generally believed to play a key role for development of chemo-resistance. However, the lack of reliable CSCs markers and specimens could be used for next-generation sequencing (NGS) limited the study and little has been made so far. We have previously confirmed that voltage-dependent calcium channel receptor α2δ1-positive cells exhibited CSCs characteristics and correlated with chemo-resistance. We explored genetic background of residual tumor using whole exon sequencing (WES) in patients treated with neoadjuvant chemotherapy. The mutation spectrum was different in residual tumor, and 27 genes may be involved in SCLC acquired resistance. Here, we will further focus on the molecular mechanism of α2δ1-mediated CSCs and chemo-resistance. Exome and transcriptome sequencing will be used to identify candidate genes and molecular mechanisms related to resistance in pre- and post- chemotherapy fresh specimens in PDXs and patients. We will explore the role of PD1/PD-L1 inhibitors and α2δ1-specific antibody 1B50-1 in CSCs, and explore the possibility that immunotherapy was used to overcome chemo-resistance and eradicate residual tumor.