BioVector® SBC-3/ETP Etoposide-Resistant Human Small Cell Lung Cancer Cell Line / SBC-3/ETP 人小细胞肺癌依托泊苷抗性耐药特异性细胞株

一 产品基本信息与细胞生物学背景

• 细胞名称：SBC-3/ETP（亦写为 SBC3/ETP）。

• 物种与组织来源：人类（Homo sapiens），源自一名 24 岁日本男性的转移性小细胞肺癌（Small Cell Lung Cancer, SCLC）骨髓标本（其亲本细胞为 SBC-3），经体外长期接触依托泊苷（Etoposide/VP-16）压力诱导筛选建立的特异性获得性耐药亚系。

• 细胞系建立背景（耐药株的衍生）：亲本 SBC-3 细胞系最初由日本科研团队从一名年轻 SCLC 患者的骨髓转移灶中分离建立。依托泊苷（Etoposide）作为一种经典的拓扑异构酶 II（Topoisomerase II）抑制剂，是临床治疗小细胞肺癌的核心一线化疗药物，但患者极易产生继发性耐药。为了在体外还原这种耐药进化过程，研究人员将亲本 SBC-3 细胞长期暴露于含有阶梯递增浓度依托泊苷的培养基中（Stepwise escalating drug selection method）。历经数月的生存压力筛选，最终促使抗性克隆存活并稳定传代，成功建立了高耐药指数的衍生亚系 SBC-3/ETP。

• 核心表型与耐药分子机制：

  • 形态学特征：贴壁生长。在倒置显微镜下，SBC-3/ETP 细胞维持了基本的上皮样（Epithelial-like）或多角形（Polygonal）形态。细胞体通常较小，核质比高，常表现为密集的细胞集团或连续的成片贴壁生长。

  • 耐药谱系特征：对依托泊苷（Etoposide）及同类拓扑异构酶抑制剂（如替尼泊苷等）表现出强烈的抵抗性，其半抑制浓度（IC50）较亲本 SBC-3 细胞显著飙升。此外，由于细胞内部药物泵的改变，该细胞常伴随有对多柔比星（Adriamycin/Doxorubicin）等部分广谱化疗药的交叉耐药（Cross-resistance）。

  • 核心耐药机理：该细胞的耐药性主要源于拓扑异构酶 II（Topoisomerase II, Topo II）的基因突变、表达量选择性下调或细胞核内定位异常，导致依托泊苷无法有效稳定“Topo II-DNA 裂解复合物”，从而逃逸了化疗引发的 DNA 双链断裂（DSBs）与细胞凋亡。此外，药物外排泵（如多药耐药相关蛋白 MRP 系列）的高表达也协同介导了其抗性表型。

• 生物安全级别：1级（BSL-1）。

二 核心科研价值与转化医学应用

SBC-3/ETP 细胞系作为高度特异性的肺癌一线化疗耐药底盘，在肿瘤药理学和转化医学研究中具有极高的应用价值：

1. 小细胞肺癌（SCLC）化疗耐药逆转剂与增敏剂筛选：SBC-3/ETP 是寻找能攻克小细胞肺癌顽固性耐药的小分子靶向药、中药天然提取物、非编码 RNA 药物的标准筛选平台。常用于评估联合用药是否能重新让耐药细胞恢复对依托泊苷的敏感性。

2. 新型拓扑异构酶抑制剂与 DNA 损伤修复（DDR）药物评价：该细胞被广泛用作靶底，用来测试新一代不依赖于经典 Topo II 路径的抗癌新药（如新型拓扑异构酶 I 抑制剂、PARP 抑制剂、ATR/ATM 抑制剂、CHK1/2 阻断剂），评估它们在克服依托泊苷耐药状态下的独立杀伤效能。

3. SCLC 肿瘤靶向新型疗法（如 DLL3 靶向与免疫疗法）评估：研究表明，SBC-3/ETP 细胞与其亲本一致，表面仍高度且特异性地表达小细胞肺癌标志物 Delta 样蛋白 3（DLL3）。因此，它常被用作耐药肺癌模型，来评估 DLL3 靶向抗体偶联药物（ADCs）、双特异性 T 细胞衔接器（BiTEs）或近红外光免疫疗法（NIR-PIT）等前沿靶向手段的治疗响应。

4. 小鼠耐药异种移植模型构建（Resistant CDX Models）：将 SBC-3/ETP 细胞接种于免疫缺陷小鼠（如 BALB/c Nude 裸鼠、NOD-SCID 小鼠）皮下，能构建稳定的、高度模拟临床晚期化疗耐药患者病理状态的异种移植（CDX）体内模型，用以定量评价候选抗癌新药在体内的抑瘤率。

三 实验室细胞复苏、贴壁常规培养、传代与保存标准步骤

SBC-3/ETP 细胞在日常维护中最大的控制核心是维持其耐药表型的稳定性，并且在消化传代时需要精准把控细胞密度。

1. 培养基配置与耐药压力维持

• 基础培养基：RPMI-1640 基础培养基。

• 维持期完全培养基配方（日常传代）：RPMI-1640 基础培养基 加 10% 优质胎牛血清（FBS） 加 1% 青霉素-链霉素双抗。

• 耐药压力维持（关键质量控制点）：

  • 在常规扩增与日常传代期间，通常需要在完全培养基中额外添加维持浓度的依托泊苷（Etoposide）药物（具体维持浓度需严格遵照随货细胞说明书或特定克隆株的耐药指数），以防止细胞在完全无药的环境下由于逆向进化而导致耐药特征发生部分回归或丢失。

  • 重要提示：在正式用于下游实验（如 MTT/CCK-8 药效检测、Western Blot 蛋白检测或小鼠体内接种）前的 24 至 48 小时，必须将细胞更换为不含依托泊苷的常规完全培养基进行洗脱（Washout），以彻底清除细胞内外残留游离药物对实验数据的背景干扰。

• 细胞解离液：0.25% Trypsin-0.02% EDTA 消化液。

• 环境参数：37 摄氏度，5% 二氧化碳，饱合湿度孵箱。

2. 冷冻细胞复苏步骤

1. 提前在无菌生物安全柜中配制好干净的 T25 培养瓶，注入 5 - 6 mL 预热至 37 摄氏度的常规完全培养基（注意：复苏第一代时，为了保证受损细胞的恢复与贴壁，切勿添加依托泊苷药物）。

2. 从液氮罐中取出 SBC-3/ETP 冻存管，立刻全量投入 37 摄氏度恒温水浴箱中快速摇晃解冻，确保在 1 分钟内令管内冰块完全融化。

3. 用 75% 酒精喷洒冻存管外壁消毒，随后移入生物安全柜内。

4. 用无菌移液枪吸取融化的细胞悬液，缓慢滴加至盛有 4 mL 预热常规完全培养基的 15 mL 离心管中，前后轻柔颠倒一次以稀释冷冻保护剂（DMSO）。

5. 以 1000 rpm（约 200 g）离心 4 - 5 分钟，小心吸除上清液。

6. 加入 1 mL 新鲜常规完全培养基轻轻重悬细胞沉淀，将其接种至准备好的 T25 瓶中。前后轻柔十字晃动混匀，置于孵箱中。

7. 复苏 24 小时后，在显微镜下常规观察细胞贴壁状态。全量更换一次新鲜培养基以清除死细胞碎屑。待细胞完全恢复对数生长状态（通常复苏 2-3 天后），在下一次传代时再重新加入含维持剂量依托泊苷的完全培养基。

3. 日常贴壁常规传代操作

• 传代时机：当细胞融合度达到 80% - 90% 时必须进行传代。由于小细胞肺癌细胞体较小且倾向于密集靠拢，绝对不能允许其长满至 100% 叠层生长。一旦过度挤压，底层细胞易因缺氧缺营养发生成片自发脱落，并会导致耐药表型发生漂移。

• 操作流程：

  1. 吸除旧培养基，使用无菌的、不含钙镁离子的 PBS 缓冲液轻轻漂洗细胞表面 1 - 2 次，彻底洗去血清。

  2. 加入适量 0.25% 胰酶消化液（T25 瓶常规加入 1 mL），摇晃使其全面覆盖细胞层。置于 37 摄氏度孵箱中消化 1 - 3 分钟。

  3. 在倒置显微镜下实时动态观察。当发现多角形细胞体边缘回缩变圆、胞间裂隙增大、轻敲瓶壁细胞可见移动脱落时，立刻加入 2 到 3 倍体积的含血清完全培养基以终止胰酶的消化反应。

  4. 用移液枪在瓶壁轻轻吹打，使细胞彻底剥离并分散成单细胞悬液。收集入管，1000 rpm 离心 5 分钟。

  5. 弃去上清，加入含维持剂量依托泊苷的完全培养基重悬。按照 1 比 3 至 1 比 5 的常规稀释比例，接种至新的培养瓶中。

  6. 通常每 2 - 3 天传代一次。为了防止其耐药基因发生长期的体外非特异性变异，建议体外连续传代代数控制在 15 代以内，严禁无限制无限期连续往下传代。

4. 细胞长期保存标准

• 冻存液配方：90% 优质完全培养基（无依托泊苷） 加 10% 分析级二甲基亚砜（DMSO）。

• 冷冻规范：

  1. 收集处于对数生长最旺盛期、健康指数高、密度在 80% 左右、形态结构处于标杆耐药维持状态的 SBC-3/ETP 细胞。

  2. 经温和消化、离心沉淀后，用配置好的无药冻存液悬浮，调整细胞密度至 每毫升 1,500,000 到 2,500,000 个细胞。

  3. 分装入无菌冻存管中，立刻移入标准程序降温盒（如 Mr. Frosty），并置于 零下 80 摄氏度冰箱中过夜梯度降温（遵循约每分钟降温 1 摄氏度的稳态速率）。

  4. 次日，必须迅速将冻存管转移入液氮罐（零下 196 摄氏度）长期锁死保存。绝对禁止在 零下 80 摄氏度普通冰箱内长期存放，以防长期的微小热幅射导致细胞内部冰晶重塑，严重破坏后续复苏时的复苏存活率与特殊的药物抵抗表型。

Part 2 English Section

I General Information and Cell Biological Background

• Cell Line Name: SBC-3/ETP (Standardly cataloged as SBC3/ETP, or SBC3-ETP).

• Organism and Tissue Extraction Origin: Homo sapiens (human); derived from a metastatic bone marrow specimen of a 24-year-old Japanese male patient diagnosed with Small Cell Lung Cancer (SCLC). The parental baseline lineage is SBC-3, and this subline was established through long-term in vitro evolutionary selection against Etoposide (VP-16).

• Cell Line Establishment Background (Derivation of the Drug-Resistant Line):The parental SBC-3 reference line was originally isolated from a bone marrow metastatic niche in a young SCLC donor. Etoposide—a classic topoisomerase II inhibitor—functions as a cornerstone first-line chemotherapeutic for small cell lung cancer; however, clinical outcomes are heavily compromised by rapid secondary drug resistance. To recapitulate this evasion mechanism in vitro, investigators exposed parental SBC-3 cultures to an escalating chemical selection pressure regimen (Stepwise escalating drug selection method) across multiple months. Surviving drug-tolerant colonies were expanded and cloned to yield SBC-3/ETP, fixing an acquired, high-index etoposide-resistant phenotype.

• Core Morphological Phenotype and Resistance Machinery:

  • Morphological Form: Adherent growth; under inverted phase-contrast microscopy, SBC-3/ETP preserves a characteristic epithelial-like or polygonal morphology. The cells are small with a high nuclear-to-cytoplasmic (N/C) ratio, expanding in tight interlocking colonies or contiguous monolayers.

  • Resistance Profile Designation: Demonstrates significant tolerance to Etoposide and related topoisomerase II targeted agents, manifesting a profound surge in its half-maximal inhibitory concentration (IC50) index compared to parental cells. Due to altered intracellular transport dynamics, the line often possesses cross-resistance phenotypes against other broad-spectrum cytostatics, such as Doxorubicin (Adriamycin).

  • Molecular Escape Cascades: The cell's resistance is primarily driven by structural point mutations, selective transcriptional downregulation, or anomalous nuclear localization of Topoisomerase II (Topo II). Consequently, etoposide fails to stabilize the "Topo II-DNA cleavage complex," allowing cells to bypass drug-induced DNA Double-Strand Breaks (DSBs) and programmed apoptosis. This is further augmented by upregulated drug efflux pumps, including elements of the Multidrug Resistance-Associated Protein (MRP) family.

• Biosafety Matrix: Classified under Biosafety Level 1 (BSL-1) containment parameters.

II Strategic Research Value and Translational Fields

SCLC behaves aggressively and acquires resistance rapidly. SBC-3/ETP serves as an important tool for evaluating clinical evasion nodes and testing advanced preclinical drug modalities:

1. High-Throughput Screening of SCLC Chemoresistance Reversers:The line acts as a standardized screening substrate to identify small-molecule targeted inhibitors, natural products, or non-coding RNA candidates capable of breaking etoposide resistance. It allows investigators to discover synergistic combinations that can restore conventional chemotherapeutic efficacy.

2. Evaluating Novel Topoisomerase and DNA Damage Repair (DDR) Inhibitors:SBC-3/ETP is deployed as a baseline platform to evaluate the cytotoxicity of next-generation anticancer agents that function independently of classical Topo II networks, such as novel topoisomerase I inhibitors, PARP inhibitors, ATR/ATM antagonists, and CHK1/2 blockers.

3. Validating Advanced SCLC-Targeted Strategies (DLL3-Targeted Therapies):Preclinical characterization confirms that, matching its parental counterpart, SBC-3/ETP retains high surface expression of Delta-like ligand 3 (DLL3), a prominent SCLC neuroendocrine biomarker. It is used to evaluate advanced DLL3-targeted configurations, including Antibody-Drug Conjugates (ADCs), Bispecific T-cell Engagers (BiTEs), and near-infrared photoimmunotherapy (NIR-PIT) platforms under chemoresistant settings.

4. Predictable In Vivo Tumor Modeling via CDX Interfacing:Inoculated subcutaneously into athymic nude or advanced immunodeficient (NOD-SCID) murine recipients, SBC-3/ETP consistently establishes solid Cell Line-Derived Xenograft (CDX) models. These models accurately mimic the pathology of advanced, chemoresistant SCLC patients, allowing for the quantitative evaluation of Tumor Growth Inhibition (TGI) rates of novel preclinical candidates.

III Laboratory Thawing, Cultivation, Passaging, and Cryopreservation Protocols

The primary metric of daily cultivation is maintaining the stability of the drug-resistant phenotype through strict adherence to drug-maintenance windows and subconfluent passaging controls.

1. Growth Medium & Chemo-Pressure Maintenance Protocols

• Basal Medium: Standard RPMI-1640 medium.

• Maintenance Complete Medium Formulation (Routine Passaging): Basal RPMI-1640 medium enriched with 10% premium Fetal Bovine Serum (FBS) and fortified with 1% Penicillin-Streptomycin dual antibiotics.

• Drug Maintenance Control Window (Critical Protocol):

  • To preserve resistance stability during routine maintenance and expansion, the complete growth medium must be spiked with a maintenance dose of Etoposide (tailored strictly to specific lot parameters or clonal resistance indexes). Cultivating cells in a drug-free matrix for extended intervals risks gradual regression or loss of the resistant phenotype due to backward evolutionary adaptation.

  • Critical Operational Note: The maintenance medium must be evacuated and replaced with drug-free complete growth medium 24 to 48 hours prior to downstream functional assays (e.g., in vitro CCK-8/MTT cytotoxicity screens, Western blotting, or live animal CDX inoculation) to wash out residual intracellular and free drug fractions, eliminating background chemical interference.

• Cell Dissociation Enzyme: Standard 0.25% Trypsin-0.02% EDTA solution.

• Environmental Cultivation Constants: Incubate at 37 degrees Celsius inside a humidified atmosphere charged with 5% Carbon Dioxide.

2. Cryovial Thawing and Recovery Sequence

1. Pre-warm a pristine T25 tissue culture flask filled with 5 - 6 mL of standard drug-free complete growth medium inside the Class II Biosafety Cabinet. (Note: Do not add etoposide during initial recovery to shield fragile, post-thaw membranes from acute cytotoxic stress).

2. Retrieve the SBC-3/ETP cryovial from liquid nitrogen storage and submerge it instantly into a 37 degrees Celsius constant-temperature water bath. Shake rapidly and continuously to secure absolute thawing within 60 seconds.

3. Decontaminate the exterior shell with 75% ethanol before transfer into the biosafety cabinet.

4. Using a sterile pipettor, smoothly extract the thawed suspension and deliver it dropwise into a 15 mL conical tube packed with 4 mL of pre-warmed drug-free complete medium, inverting gently once to equalize osmotic pressures.

5. Centrifuge the suspension at 1000 rpm (approximately 200 g) for 4 - 5 minutes at room temperature, then carefully decant the DMSO-laden supernatant.

6. Resuspend the cell pellet in 1 mL of fresh drug-free complete growth medium, transfer the entire volume into the prepared T25 flask, distribute evenly via a gentle cross-shake movement, and place in the incubator.

7. Inspect the adherent status approximately 24 hours post-thaw. Perform a complete medium change to remove non-adherent dead cell fragments. Once the cells regain robust log-phase division metrics (typically 2-3 days post-thaw), reintroduce the complete growth medium spiked with the maintenance dose of etoposide at the next passage.

3. Routine Adherent Passaging Mechanics and Maintenance

• Confluency Control Window: Subculturing routines must be initiated when monolayers achieve an optimal 80% - 90% confluency scale. Because SCLC cells have small diameters and naturally grow in tight clusters, never allow SBC-3/ETP sheets to achieve 100% full saturation or multilayer stratification. Overcrowding triggers sheet detachment due to underlying localized nutrient depletion and leads to phenotypic resistance drift.

• Passaging Execution Steps:

  1. Aspirate the spent growth matrix and gently rinse the cell layer 1 - 2 times with sterile, calcium/magnesium-free PBS to remove all remaining serum proteins that could deactivate the trypsin.

  2. Administer a suitable volume of 0.25% Trypsin-EDTA enzyme (typically 1 mL for a T25 flask format), tilt the flask to ensure total monolayer coverage, and place inside the 37 degrees Celsius incubator for 1 - 3 minutes.

  3. Monitor cell detachment kinetics under an inverted microscope. As the polygonal cells round up, separate from neighbors, and slide upon gentle physical tapping of the flask wall, immediately add 2 to 3 volumes of serum-fortified complete growth medium to arrest enzymatic cleavage.

  4. Gently pipette the solution against the flask walls to rinse down remaining cells and dissociate clusters into a single-cell suspension. Transfer the suspension into a conical tube and centrifuge at 1000 rpm for 5 minutes.

  5. Discard the supernatant, resuspend the cell pellet in fresh complete growth medium supplemented with the maintenance dose of etoposide, and inoculate into new flasks utilizing standard split ratios of 1:3 to 1:5. Subculture every 2 - 3 days.

  6. To prevent unintended long-term genetic drift in vitro, it is highly recommended to restrict continuous cultivation to under 15 total passages from thaw.

4. Long-Term Cryopreservation Standards

• Cryoprotectant Preservation Matrix: 90% premium complete growth medium (without etoposide) supplemented with 10% analytical-grade Dimethyl Sulfoxide (DMSO).

• Freezing Protocol Validation:

  1. Exclusively harvest healthy, log-phase cultures showing an optimal confluency of approximately 80% under standard maintenance drug conditions.

  2. Post-enzymatic treatment and centrifugation, adjust the cell concentration inside the formulated drug-free cryoprotectant matrix to a target range of 1,500,000 to 2,500,000 cells per milliliter.

  3. Dispense the suspension into sterile cryovials, insert them immediately into a controlled-rate freezing device (e.g., Mr. Frosty), and place into a minus 80 degrees Celsius freezer overnight to achieve steady gradient cooling (approximately 1 degree Celsius per minute).

  4. The following day, swiftly transfer the frozen cryovials into liquid nitrogen storage tanks (minus 196 degrees Celsius) for definitive long-term preservation. Do not store vials indefinitely inside a minus 80 degrees Celsius freezer; minor temperature oscillations can compromise post-thaw recovery rates and lead to the degradation of resistant traits.

The diagnostic framework and immunotherapy testing methodologies for such refractory hematological and small cell phenotypes can be explored in The diagnosis of early T-cell precursor (ETP) ALL. This video outlines the molecular biology and characterization protocols used to identify highly refractory, immature, and multi-lineage resistant cellular phenotypes in translational medical laboratories.

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