BioVector® 4T1-Taxol Paclitaxel-Resistant Mouse Mammary Carcinoma Cell Line / 4T1-Taxol 小鼠乳腺癌紫杉醇耐药特异性细胞株

一 产品基本信息与细胞生物学背景

• 细胞名称：4T1-Taxol（亦称 4T1/PTX，4T1-PR）。

• 物种与组织来源：小鼠（Mus musculus），源自 BALB/c 小鼠自发性乳腺癌（4T1 亲本细胞），经体外高浓度紫杉醇（Taxol/Paclitaxel）阶梯递增压力诱导筛选建立的耐药亚系。

• 细胞系建立背景（耐药株的衍生）：4T1 亲本细胞是国际公认的、恶性程度极高且极具侵袭性的小鼠三阴性乳腺癌（TNBC）同系移植模型。紫杉醇（Taxol）作为临床针对乳腺癌的一线微管稳定类化疗药物，极易在治疗中后期诱发获得性耐药。科研人员通过在 4T1 亲本细胞的日常培养基中，连续数月、从极低剂量（如几纳摩尔）阶梯式递增添加紫杉醇进行持续的体外生存压力筛选（Stepwise escalating drug selection method），最终促使特定抗性克隆存活。在对其进行单克隆富集扩增及耐药指数（RI）鉴定后，锁定了这株具备高稳定紫杉醇耐药表型的衍生亚系 4T1-Taxol。

• 核心表型与耐药机理特征：

  • 耐药谱系表征：相较于亲本 4T1 细胞，4T1-Taxol 的半抑制浓度（IC50）飙升了数十倍甚至上百倍。对紫杉醇引发的微管束聚合稳定、有丝分裂阻滞及后续的凋亡级联反应（Apoptosis cascade）表现出强烈的抵抗性。

  • 形态学改变：贴壁生长。在倒置显微镜下，该耐药亚系维持了基本的上皮样（Epithelial-like）形态，但相较于亲本，其胞体通常略微增大、铺展、拉长，细胞骨架发生重塑，甚至细胞核在 DAPI 染色下表现出特征性的异质性肥大。

  • 耐药分子机制：细胞内部高度激活了药物外排泵（如 P-糖蛋白 P-gp/MDR1/ABCB1）、发生了微管蛋白异型体（如 β-tubulin 突变或高表达）改变，或者选择性激活了 HER2/β-catenin/c-Myc 等抗凋亡增殖通路，使其能够在高浓度药物环境中完美绕过细胞周期监控。

• 生物安全级别：1级（BSL-1）。

二 核心科研价值与转化医学应用

4T1-Taxol 克服了人源耐药模型无法在免疫健全小鼠体内成瘤的瓶颈，在肿瘤药理学和转化医学研究中扮演着不可替代的角色：

1. 化疗耐药逆转剂（Chemoresistance Reversers）的体外高通量筛选：4T1-Taxol 是寻找“紫杉醇增敏剂”的标准底盘。科研人员通常将其作为靶板，筛选新型小分子激酶抑制剂、MDR1 外排泵阻断剂、中药天然提取物（如 EGCG 等）是否能与紫杉醇联合，重新恢复该耐药株对微管靶向化疗的敏感性。

2. 同系免疫健全耐药小鼠模型构建（Syngeneic Taxol-Resistant CDX Model）：这是该细胞系最核心的战略价值。将 4T1-Taxol 接种到免疫健全的 BALB/c 雌鼠的原位乳腺脂肪垫（Mammary fat pad）或皮下后，其成瘤率高达 100%。它可以完美模拟临床上“晚期三阴性乳腺癌患者对紫杉醇化疗耐药、肿瘤持续生长及全身广泛性转移”的极其复杂的病理微环境。

3. 耐药状态下的肿瘤转移（Metastasis）与肿瘤免疫微环境（TME）探讨：4T1 亲本本身即具有极强的自发转移（肺、肝、脑、骨等）能力。通过 4T1-Taxol 模型，研究者能深度探究：乳腺癌细胞在对紫杉醇耐药后，其长途迁移能力、上皮-间充质转化（EMT）活性是否发生进一步进化；以及耐药肿瘤在体内如何通过耗竭 T 细胞、富集 MDSCs（髓系来源抑制细胞），来构建更为顽固的免疫逃逸微环境。

三 实验室细胞复苏、贴壁常规培养、传代与保存标准步骤

4T1-Taxol 细胞生长极为凶猛，其细胞倍增时间短，对营养消耗速度惊人。在培养过程中，最大的控制核心是维持其耐药表型的稳定性。

1. 培养基配置与耐药压力维持

• 基础培养基：RPMI-1640 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紫杉醇（具体药物浓度需严格遵照随货细胞说明书，通常在 50 nM - 100 nM 范围，因具体克隆株耐药指数而异），以防细胞在无药环境下由于逆向进化而导致耐药性发生部分退化。

  • 重要提示：在正式用于下游实验（如 MTT 药效检测、Western Blot 检测、小鼠体内接种）前的 24 至 48 小时，必须更换为不含紫杉醇的常规完全培养基进行洗脱，以清除残存药物对后续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，饱和湿度。

2. 冷冻细胞复苏步骤

1. 提前在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贴壁，千万不要添加紫杉醇药物）。

2. 从液氮罐中取出 4T1-Taxol 冻存管，立刻投入 37 摄氏度恒温水浴箱中快速摇晃解冻，确保在 1 分钟内完全融化。

3. 用 75% 酒精喷洒消毒外壁，移入安全柜内。

4. 用无菌移液枪吸取细胞悬液，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（动作轻柔，避免物理剪切损伤）。

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

6. 加入 1 mL 新鲜常规完全培养基重悬细胞沉淀，将其接种至 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，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。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紫杉醇的完全培养基。

3. 日常贴壁常规传代操作

• 传代时机：当细胞融合度达到 80% 左右时必须进行传代。4T1 系列细胞生长周期极短（倍增时间通常十几小时），绝对不能允许其长满至 100% 连成密不透风的片状。一旦过密，细胞会自发老龄化、大面积抱团悬浮脱落，且极易导致耐药表型退化。

• 操作流程：

  1. 吸除细胞瓶内的旧培养基，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，洗去血清。

  2. 加入适量 0.25% 胰酶消化液（T25 瓶加入 1 mL），摇晃使其覆盖细胞层。置于 37 摄氏度孵箱（或室温）中消化 1 - 2 分钟。

  3. 在倒置显微镜下观察。当发现原本铺展的上皮样细胞快速回缩变圆、胞间出现明显裂隙、轻敲瓶壁细胞开始整体移动时，立刻加入 2 到 3 倍体积的含血清完全培养基以终止胰酶消化。

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

  5. 弃去上清，加入含维持剂量紫杉醇的完全培养基。按照 1 比 6 至 1 比 8 的常规稀释比例，接种至新的培养瓶中。

  6. 通常每 2 天就需传代一次。为了防止其耐药基因发生长期体外变异漂移，建议体外连续传代代数严格控制在 15-20 代以内使用，严禁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（无紫杉醇） 加 10% 分析级二甲基亚砜（DMSO），或使用 95% 完全培养基 加 5% DMSO。

• 冷冻规范：

  1. 收集处于对数生长最旺盛期、细胞密度在 80% 左右、形态高度健康的 4T1-Taxol 细胞（处于加药维持状态的细胞即可）。

  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 2,000,000 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（约每分钟降温 1 摄氏度）。

  4. 次日，迅速将冻存管转移入液氮罐（零下 196 摄氏度）中长期锁死保存。严禁在 零下 80 度普通冰箱内长期存放，以防长期的微小温度波动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及耐药特性的维持。

Part 2 English Section

I General Information and Cell Biological Background

• Cell Line Name: 4T1-Taxol (Standardly abbreviated as 4T1/PTX, or 4T1-PR).

• Organism and Tissue Extraction Origin: Mus musculus (mouse); derived from the parental 4T1 mouse triple-negative breast cancer line in a BALB/c background, engineered via chronic stepwise escalation exposure to Paclitaxel (Taxol).

• Cell Line Establishment Background (Derivation of the Drug-Resistant Subline):The parental 4T1 lineage is a globally standardized, hyper-aggressive, and invasive human Triple-Negative Breast Cancer (TNBC) syngeneic analog.In clinical oncology, Paclitaxel (Taxol) represents a primary microtubule-stabilizing chemotherapeutic; however, long-term administration frequently induces acquired multidrug resistance. Investigators exposed parental 4T1 cultures to an escalating chemical selection pressure regimen (Stepwise escalating drug selection method) spanning multiple months, starting from nanomolar scales. Surviving drug-tolerant colonies were enriched and cloned to validate 4T1-Taxol, locking in a highly stable paclitaxel-resistant phenotype.

• Core Morphological Phenotype and Resistance Mechanisms:

  • Resistance Profile Designation: Exhibits an extreme shift in its half-maximal inhibitory concentration (IC50) index, demonstrating a multifold surge in tolerance compared to parental cells. The line shows complete evasion of paclitaxel-induced microtubule bundling, mitotic arrest, and downstream apoptotic signaling cascades.

  • Morphological Form: Adherent growth; under inverted phase-contrast microscopy, it maintains a general epithelial-like framework. However, compared to parent cells, the resistant variants typically appear enlarged, flattened, and elongated, exhibiting profound cytoskeleton remodeling and hypertrophic nuclear configurations.

  • Molecular Machinery of Evasion: Driven by high expression of cellular drug efflux pumps (such as P-glycoprotein, encoded by MDR1/ABCB1), specific structural mutations or shifts in β-tubulin isotype profiles, or hyper-activation of cell survival networks (such as the HER2/β-catenin/c-Myc signaling loops), allowing cells to bypass cell cycle surveillance hubs.

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

II Strategic Research Value and Translational Fields

4T1-Taxol circumvents a critical limitation of human-derived resistant lineages—their inability to establish tumors in immunocompetent animals—making it essential for translational oncology studies:

1. High-Throughput Screening of Chemoresistance Reversers:4T1-Taxol serves as a standard screening substrate to discover "Paclitaxel sensitizers". It is used to test whether novel small-molecule kinase inhibitors, P-gp efflux pump antagonists, or bioactive natural molecules (such as green tea catechins/EGCG) can act synergistically with taxanes to restore chemotherapeutic sensitivity.

2. Syngeneic Immunocompetent Resistant CDX Modeling:This represents the primary strategic value of the line. Inoculating 4T1-Taxol into immunocompetent female BALB/c recipients (either subcutaneously or directly into the mammary fat pads) yields a 100% tumor-take profile. This system reproduces the intricate pathology of advanced, chemoresistant TNBC in humans, mimicking primary tumor progression alongside spontaneous distal spread under an intact host immune system.

3. Deciphering Metastasis Mechanics & Tumor Microenvironment (TME) Modeling:The parental 4T1 background naturally tracks multi-organ spontaneous metastasis (homing to lungs, liver, bones, and brain). Utilizing the 4T1-Taxol configuration allows investigators to determine if chemoresistance pathways accelerate Epithelial-Mesenchymal Transition (EMT) and distal migration, and to examine how chemoresistant nodes remodel the TME by exhausting effector T-cells and enriching Myeloid-Derived Suppressor Cells (MDSCs).

III Laboratory Thawing, Cultivation, Passaging, and Cryopreservation Protocols

4T1-Taxol cells proliferate rapidly with a brief doubling time and a high rate of nutrient consumption. The primary parameter of daily cultivation is maintaining the stability of the drug-resistant phenotype.

1. Growth Medium & Chemo-Pressure Maintenance Protocols

• Basal Medium: RPMI-1640 medium.

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

• Drug Maintenance Control Window (Critical Protocol):

  • To secure resistance stability during routine maintenance, the complete growth medium must be spiked with a maintenance dose of Paclitaxel (ranging typically between 50 nM and 100 nM depending on specific lot specifications and target verification boundaries). Cultivating cells in a drug-free matrix for extended periods can cause gradual regression of the resistant phenotype.

  • 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 MTT cytotoxicity profiling, Western blotting, or live animal inoculation) to wash out residual intracellular paclitaxel and eliminate background drug 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 packed with 5 - 6 mL of standard drug-free complete growth medium inside the Class II Biosafety Cabinet. (Note: Do not add paclitaxel during initial recovery to prevent acute cytotoxicity while the cells are structurally fragile post-thaw).

2. Retrieve the 4T1-Taxol 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. Handle gently to avoid structural cell shear stress.

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 sediment in 1 mL of fresh drug-free complete growth medium and transfer the entire volume into the prepared T25 flask. Distribute evenly by executing 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 paclitaxel at the next passage.

3. Routine Adherent Passaging Mechanics and Maintenance

• Confluency Control Window: Subculturing routines must be initiated when monolayers achieve a target 80% confluency scale.Due to its rapid doubling cycle, never allow 4T1-Taxol sheets to achieve 100% full saturation or compact layering. Overcrowding triggers rapid cell aging, large-scale sheet detachment into floating spheres, and a structural drop in drug-resistance stability.

• 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 - 2 minutes.

  3. Monitor cell detachment kinetics under an inverted microscope. As the epithelial-like 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, pre-warmed complete growth medium supplemented with the maintenance dose of paclitaxel, and inoculate into new flasks utilizing standard split ratios of 1:6 to 1:8.

  6. Execute subculturing every 2 days. To prevent genetic drift and maintain long-term phenotypic integrity, it is highly recommended to restrict in vitro expansion to under 15–20 total passages.

4. Long-Term Cryopreservation Standards

• Cryoprotectant Preservation Matrix: 90% premium complete growth medium (without paclitaxel) supplemented with 10% analytical-grade Dimethyl Sulfoxide (DMSO) (or 95% complete medium with 5% 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 1,000,000 to 2,000,000 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.

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