肿瘤细胞治疗研究
英文原题：Cancer-oocyte SAS1B protein is expressed at the cell surface of multiple solid tumors and targeted with antibody-drug conjugates.
SAS1B是一种新型的癌-卵母细胞抗原，其细胞表面表达仅限于癌细胞。在体外，它是抗体介导的癌细胞裂解的有效靶点。这些发现支持进一步探索SAS1B作为多种人类癌症中潜在的治疗性癌症靶点，无论是作为ADC还是作为CAR-T（CAR-T）细胞靶点。
精子顶体SLLP1结合蛋白（SAS1B）存在于卵母细胞中，是精子-卵母细胞相互作用所必需的，也存在于子宫癌和胰腺癌中。抗SAS1B抗体-药物偶联物（ADC）可抑制这些癌症的生长。然而，SAS1B在癌症和正常组织中的表达尚未被表征。我们假设SAS1B表达于其他常见实体癌细胞表面，但不表达于正常组织细胞，并可能成为选择性治疗靶点。
采用免疫组织化学法检测人正常组织和癌组织中 SAS1B 的表达，并利用互补 DNA（cDNA）文库通过 PCR 扩增人 SAS1B 及其转录本。使用小鼠杂交瘤生成抗人 SAS1B 单克隆抗体（mAb）。构建 SAS1B 缺失突变体以定位 SAS1B 的表位，从而制备阻断肽。对人转染的正常细胞和癌细胞进行间接免疫荧光（IIF）以评估 SAS1B 表达。用抗 SAS1B mAb 染色后，通过流式细胞术评估正常组织和肿瘤组织中 SAS1B 的细胞内表达与表面表达，并用阻断肽确认特异性。用递增浓度的 mAb 和 ADC 处理人癌细胞系。定量 ATP 作为细胞活力的指标。
SAS1B表达在部分人类癌症和胰岛细胞胞质中被鉴定。推导出两种新的SAS1B剪接变体。针对SAS1B剪接变体A产生了单克隆抗体。mAbs SB2和SB5的表位位于SAS1B氨基酸32-39之间。IIF显示转染肾细胞中有细胞内SAS1B表达，以及鳞状细胞肺癌细胞表面有表达。流式细胞术显示所有肿瘤和部分正常细胞中有细胞内SAS1B表达。然而，SAS1B的表面表达仅在癌细胞上被鉴定到。SB2 ADC介导了对多种人类癌细胞系的剂量依赖性细胞毒性杀伤。
BACKGROUND: S perm a crosomal S LLP 1 b inding (SAS1B) protein is found in oocytes, which is necessary for sperm-oocyte interaction, and also in uterine and pancreatic cancers. Anti-SAS1B antibody-drug conjugates (ADCs) arrested growth in these cancers. However, SAS1B expression in cancers and normal tissues has not been characterized. We hypothesized that SAS1B is expressed on the surface of other common solid cancer cells, but not on normal tissue cells, and might be selectively targeted therapeutically. METHODS: SAS1B expression in human normal and cancer tissues was determined by immunohistochemistry, and complementary DNA (cDNA) libraries were employed to PCR amplify human SAS1B and its transcripts. Monoclonal antibodies (mAbs) to human SAS1B were generated using mouse hybridomas. SAS1B deletion constructs were developed to map SAS1B's epitope, enabling the creation of a blocking peptide. Indirect immunofluorescence (IIF) of human transfected normal and cancer cells was performed to assess SAS1B expression. SAS1B intracellular versus surface expression in normal and tumor tissues was evaluated by flow cytometry after staining with anti-SAS1B mAb, with specificity confirmed with the blocking peptide. Human cancer lines were treated with increasing mAb and ADC concentrations. ATP was quantitated as a measure of cell viability. RESULTS: SAS1B expression was identified in a subset of human cancers and the cytoplasm of pancreatic islet cells. Two new SAS1B splice variants were deduced. Monoclonal antibodies were generated to SAS1B splice variant A. The epitope for mAbs SB2 and SB5 is between SAS1B amino acids 32-39. IIF demonstrated intracellular SAS1B expression in transfected kidney cells and on the cell surface of squamous cell lung carcinoma. Flow cytometry demonstrated intracellular SAS1B expression in all tumors and some normal cells. However, surface expression of SAS1B was identified only on cancer cells. SB2 ADC mediated dose-dependent cytotoxic killing of multiple human cancer lines. CONCLUSION: SAS1B is a novel cancer-oocyte antigen with cell surface expression restricted to cancer cells. In vitro, it is an effective target for antibody-mediated cancer cell lysis. These findings support further exploration of SAS1B as a potential therapeutic cancer target in multiple human cancers, either with ADC or as a chimeric antigen receptor-T (CAR-T) cell target.
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