~(131)I-Herceptin对HER2过表达乳腺癌细胞Bcl-xL表达的影响

目的:探讨131I-Herceptin对HER2过表达乳腺癌细胞Bcl-x L表达的影响。方法:采用Iodogen法制备131I-Herceptin,超滤法纯化后测定其标记率、放射化学纯度和免疫结合率。通过免疫荧光法检测乳腺癌细胞表面HER2表达水平。131I(4.625 MBq/m L)、Herceptin(125μg/m L)及131I-Herceptin(4.625 MBq/m L)干预乳腺癌BT474细胞后,Western blot检测细胞中Bcl-x L的表达。结果:131I-Herceptin的标记率、放射化学纯度和免疫结合率分别为(89.71±2.93)%、(91.80±1.43)%和(58.84±3.35)%。BT474细胞膜表面HER2表达水平明显高于MDA-MB-231细胞。Herceptin、131I-Herceptin组BT474细胞内Bcl-x L表达水平明显低于对照组及131I组(均P0.01),而Herceptin与131I-Herceptin组之间细胞内Bcl-x L含量差异无统计学意义(P0.05)。结论:131I-Herceptin保留Herceptin对HER2过表达乳腺癌细胞Bcl-x L表达的抑制作用并促进细胞凋亡,进而与131I产生协同作用,较Herceptin更有效地杀伤HER2过表达乳腺癌细胞。     

Anti HER2 ScFv-GFP融合抗体靶向检测HER2的表达

为验证真核表达的携带绿色荧光的抗HER2单链抗体应用于临床诊断HER2阳性肿瘤细胞和病理组织的可靠性,构建融合基因Anti HER2 ScFv-GFP,重组入pFAST Bac HT A载体,在昆虫细胞Sf9中表达,以Ni2+-NTA亲和层析法纯化Anti HER2 ScFv-GFP融合蛋白,测定其浓度与纯度,将同浓度的纯化蛋白分别与3种乳腺癌细胞BT474、SKBR3和MCF7各混合12 h、24 h和48 h,分析其在不同时间段结合HER2阳性肿瘤细胞的稳定性。用纯化蛋白直接检测经抗原修复的乳腺癌病理组织,与免疫组织化学法检测结果对比。结果在昆虫细胞Sf9中可观察到明显绿色荧光,纯化的融合蛋白相对分子量约60 kDa,浓度为115.5μg/mL,纯度约97%,SKBR3和BT474鉴定为HER2阳性。结合12 h、24 h、48 h后其细胞表面均有明显绿色荧光,而HER2阴性MCF7被洗脱后无荧光,该抗体滴度为1:64,48 h内该荧光抗体仍具有稳定性。携带绿色荧光的融合抗体检测病理组织与IHC法的结果完全一致。表明成功表达的携带绿色荧光的抗HER2单链抗体可特异性检测HER2阳性乳腺癌细胞BT474和SKBR3,在HER2阳性肿瘤细胞和临床病理组织检测上具有应用前景。     

人FOXO3a基因真核表达载体的构建及其功能验证

目的:构建带myc标签的人FOXO3a基因真核表达载体,并对其功能进行初步检测。方法:采用PCR技术,从乳腺文库中扩增人FOXO3a基因,并将其正确插入pXJ-40-myc载体;将重组质粒与空载体分别转染人乳腺癌细胞系ZR75-1、MCF-7后,通过Western印迹检测其表达情况,并用CCK8法测定细胞生长曲线。结果:双酶切和测序鉴定表明myc-FOXO3a真核表达质粒构建成功,转染乳腺癌ZR75-1、MCF-7细胞后目的基因成功表达;细胞生长曲线结果显示,转染myc-FOXO3a的乳腺癌细胞较空载体细胞生长较慢。结论:构建了带myc标签的人FOXO3a基因真核表达载体,为进一步研究FOXO3a在乳腺癌中的功能奠定了基础。     

Anti-HER2-ScFv-GFP融合蛋白靶向结合体外乳腺癌细胞表面受体的研究

为了研究不同表达系统获得的携带绿色荧光抗HER2单链抗体(Anti-HER2-ScFv-GFP)是否既可靶向结合HER2阳性乳腺癌细胞表面,也可通过观察绿色荧光变化直接判断抗体结合乳腺癌细胞表面后细胞的动态变化,在前期成功构建两种表达系统的基础上,利用Ni~(2+)-NTA亲和层析法纯化来源于真核表达系统pFAST Bac to Bac HT A/Tn-5B1-4和原核表达系统pBAD His B/TOP10的融合蛋白Anti-HER2-ScFv-GFP,设置HER2阳性细胞SKBR3为实验组、HER2阴性细胞MCF7为对照组,分别与之混合24 h后,1×PBS洗脱细胞3次,激光共聚焦显微镜观察到两种不同表达系统获得的融合蛋白在HER2阳性细胞SKBR3表面分布均有绿色荧光,真核表达的蛋白结合效率明显高于原核表达的蛋白,SKBR3结合高浓度的融合蛋白后细胞表现出皱缩,绿色荧光明显增强,而两种不同来源的融合蛋白与HER2阴性MCF7混合后均易被洗脱。GFP标准品与SKBR3混合后也容易被洗脱。实验表明构建的携带绿色荧光抗HER2单链抗体同时具有靶向结合和报告作用两方面的功能。     

薯蓣皂苷激活p38MAPK/FOXO3a信号抑制三阴性乳腺癌细胞上皮–间质转化及侵袭

该研究探讨了薯蓣皂苷(Dioscin)对三阴性乳腺癌MDA-MB-231、BT549细胞体外侵袭及上皮–间质转化(epithelial to mensenchymal transition,EMT)的影响及其作用机制。以正常人乳腺上皮MCF-10A细胞为对照,通过MTS法、克隆形成实验检测细胞增殖能力;Transwell实验检测细胞侵袭、迁移能力;Western blot法检测p38MAPK、p-p38MAPK、FOXO3a及上皮–间质转化(epithelial to mensenchymal transition,EMT)相关标志物的表达。结果显示,Dioscin能明显抑制MDA-MB-231、BT549细胞的增殖,且具有浓度依赖性,对MCF-10A细胞抑制作用较弱;Dioscin处理后肿瘤细胞的侵袭、迁移能力明显降低,Dioscin可显著下调细胞间质样标志物波形蛋白(vimentin)、N-钙黏蛋白(N-cadherin)并促进上皮样标志物E-钙黏蛋白(E-cadherin)的表达,EMT关键转录因子Snail的表达也受到抑制。进一步研究发现,Dioscin能够上调p38MAPK磷酸化水平并促进转录因子FOXO3a的表达,而干扰FOXO3a能够逆转Dioscin对细胞EMT及侵袭的抑制作用。以上研究表明,Dioscin能够抑制三阴性乳腺癌细胞EMT及体外侵袭、迁移能力,其机制可能与Dioscin调控p38MAPK/FOXO3a信号有关。     

反义硫代寡核苷酸与赫赛汀联合抗乳腺癌活性的体外研究

目的:研究以人表皮生长因子受体2(HER2)mRNA为靶点的反义硫代脱氧寡核苷酸(S-ODNs)HA6722单用及与赫赛汀合用时对HER2过表达乳腺癌细胞株MDA-MB-453体外增殖的抑制作用,探索乳腺癌治疗的新方法。方法:选择HER2过表达的MDA-MB-453乳腺癌细胞,用噻唑蓝(MTT)法观察HA6722单用及与赫赛汀合用时对该肿瘤细胞增殖的影响;以末端转移酶介导的dUTP切口末端标记法(TUNEL)检测细胞凋亡。结果:HA6722及赫赛汀单用均可以剂量依赖方式抑制MDA-MB-453细胞的体外增殖,IC50值分别为(79.41±11.51)及(60.66±17.63)nmol/L(n=3,x±s)。联合应用的顺序直接影响二者的交互作用,如先用HA6722再用赫赛汀,则在50及200nmol/L的浓度下联合应用对MDA-MB-453细胞的增殖抑制作用增强,但在800nmol/L的浓度下抗增殖作用并无进一步增强。结论:在适宜的浓度下,反义寡核苷酸HA6722与单克隆抗体赫赛汀序贯应用,对HER2过表达乳腺癌细胞的体外增殖抑制具有协同作用。     

HER2胞外段的克隆与原核表达

应用RT-PCR技术从人乳腺癌细胞系SK-BR-3中克隆出人表皮生长因子受体2(human epidermal growth factorreceptor 2,HER2)基因的胞外段,并插入到表达载体pET-30a中,得到重组表达载体pET30-HER2(Ex)。将该载体转化至大肠杆菌BL21(DE3)细胞中,加入IPTG进行诱导表达,成功获得HER2胞外段蛋白。分别提取培养液上清、大肠杆菌周质腔、细胞质可溶性及不可溶性组分蛋白进行SDS-PAGE电泳分析,确定目的蛋白定位于大肠杆菌细胞质包涵体中。通过改变诱导温度、诱导物浓度、诱导起始菌体密度和诱导时间,寻找最佳表达条件,使目的蛋白的表达量达到最高。结果表明,在37℃下,OD600达到1.0时,经终浓度为0.1 mmol/L的IPTG诱导4 h,目的蛋白的表达量最高。将重组表达菌进行超声破碎,分离出包涵体组分,经Ni2+亲和层析纯化后获得了纯度>90%的HER2胞外段蛋白,从而为抗HER2抗体的制备及肿瘤疫苗的研究奠定了基础。     

Caveolin-1 siRNA对与乳腺癌细胞共培养的成纤维细胞自噬体表达影响的研究

为了探索乳腺癌相关的人成纤维细胞中窖蛋白-1(Caveolin-1,Cav-1)与自噬体的相关性及其对乳腺癌细胞的作用,该研究采用si RNA技术干扰成纤维细胞株ESF表达Cav-1,q RTPCR和Western blot确定si RNA干扰Cav-1表达的效果;Transwell insert方法共培养乳腺癌细胞株BT474和ESF细胞,单丹磺酰戊二胺(monodansylcadaverin,MDC)染色、激光共聚焦显微镜观察Cav-1 si RNA对自噬体表达的影响;q RT-PCR和Western blot检测Cav-1 si RNA对微管相关蛋白1轻链3II(microtubule-associated protein 1 light chain 3 II,LC3II)表达的影响;CCK-8方法检测BT474细胞的增殖和活力。结果显示,靶向Cav-1的si RNA下调了ESF细胞中Cav-1的表达;Cav-1 si RNA促进ESF细胞自噬体和LC3II的表达,转染了Cav-1 si RNA的ESF细胞与BT474细胞共培养对自噬体和LC3II的作用更为显著;BT474细胞在ESFsi Cav-1(ESF cells transfected with Cav-1 si RNA)细胞共培养条件下增殖显著加快。研究表明,Cav-1 si RNA促进了与乳腺癌细胞共培养的成纤维细胞自噬体和LC3II的表达,同时加快了与成纤维细胞共培养的乳腺癌细胞的增殖。     

EGFR、HER2、CXCR4在非小细胞肺癌中的表达及临床意义

目的:研究EGFR(epidermal growth factor receptor)、HER2(human epidermalgrowth factor receptor-2)及CXCR4(chemokine(C-X-C motif)receptor 4)在NSCLC中的表达,分析它们与NSCLC临床病理特征的的关系。方法:选择我科2009年7月-2012年12月收治的75例非小细胞肺癌(NSCLC)患者为研究对象,支气管镜活检得到NSCLC肿瘤组织标本,免疫组织化学技术分别检测EGFR、HER2、CXCR4在NSCLC组织中的表达,并分析EGFR、HER2、CXCR4的表达与NSCLC患者临床病理指标和生存期的相关性。结果:EGFR、HER2及CXCR4在NSCLC中的表达与患者淋巴转移及远处转移有关(P0.05)。EGFR、HER2及CXCR4在NSCLC中的表达均呈正相关,EGFR与HER2,EGFR与CXCR4,HER2与CXCR4的相关系数分别为r=0.296(P0.01),r=0.578(P0.01),r=0.426(P0.01)。3种基因表达越多,患者中位生存时间越短(P0.05)。结论:EGFR、HER2及CXCR4与NSCLC的发生发展关系密切,针对性的多个靶向抑制,可更好发挥抑癌作用。根据三者不同的表达情况初步筛选出针对靶向治疗的单一或联合靶点,有助于为NSCLC患者提供个体化的治疗方案。为进一步治疗提供依据。     

EGFR、HER2、CXCR4在tied,细胞肺癌中的表达及临床意义

目的：研究EGFR（epidermal growth factor receptor）、HER2（ human epidermalgrowth factor receptor-2）及CXCR4（chemokine（C-X-C motif） receptor 4）在NSCLC 中的表达,分析它们与NSCLC 临床病理特征的的关系。方法：选择我科2009 年7 月-2012年12 月收治的75 例非小细胞肺癌（NSCLC）患者为研究对象,支气管镜活检得到NSCLC肿瘤组织标本,免疫组织化学技术分别检测EGFR、HER2、CXCR4在NSCLC 组织中的表达,并分析EGFR、HER2、CXCR4 的表达与NSCLC 患者临床病理指标和生存期的相关性。结果：EGFR、HER2 及CXCR4在NSCLC中的表达与患者淋巴转移及远处转移有关（P〈0.05）。EGFR、HER2 及CXCR4在NSCLC 中的表达均呈正相关,EGFR 与HER2,EGFR 与CXCR4,HER2 与CXCR4 的相关系数分别为r=0.296（P〈0.01）,r=0.578（P〈0.01）,r=0.426（P〈0.01）。3 种基因表达越多,患者中位生存时间越短（P〈0.05）。结论：EGFR、HER2 及CXCR4 与NSCLC的发生发展关系密切,针对性的多个靶向抑制,可更好发挥抑癌作用。根据三者不同的表达情况初步筛选出针对靶向治疗的单一或联合靶点,有助于为NSCLC 患者提供个体化的治疗方案。为进一步治疗提供依据。     

Calmodulin binds HER2 and modulates HER2 signaling

Human epidermal growth factor receptor 2 (HER2), a member of the ErbB family of receptor tyrosine kinases, has defined roles in neoplastic transformation and tumor progression. Overexpression of HER2 is an adverse prognostic factor in several human neoplasms and, particularly in breast cancer, correlates strongly with a decrease in overall patient survival. HER2 stimulates breast tumorigenesis by forming protein-protein interactions with a diverse array of intracellular signaling molecules, and evidence suggests that manipulation of these associations holds therapeutic potential. To modulate specific HER2 interactions, the region(s) of HER2 to which each target binds must be accurately identified. Calmodulin (CaM), a ubiquitously expressed Ca²⁺ binding protein, interacts with multiple intracellular targets. Interestingly, CaM binds the juxtamembrane region of the epidermal growth factor receptor, a HER2 homolog. Here, we show that CaM interacts, in a Ca²⁺-regulated manner, with two distinct sites on the N-terminal portion of the HER2 intracellular domain. Deletion of residues 676-689 and 714-732 from HER2 prevented CaM-HER2 binding. Inhibition of CaM function or deletion of the CaM binding sites from HER2 significantly decreased both HER2 phosphorylation and HER2-stimulated cell growth. Collectively, these data suggest that inhibition of CaM-HER2 interaction may represent a rational therapeutic strategy for the treatment of patients with breast cancer. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.     

曲妥珠单抗辅助或新辅助治疗HER2 阳性转移性乳腺癌的临床结果

目的:比较人表皮生长因子受体2过表达(HER2+)的患者既往接受以曲妥珠单抗为基础辅助或新辅助治疗后再次接受针曲妥珠单抗治疗的临床结果。方法:共247例(I-III期170例,IV期77例)HER2+转移性乳腺癌患者,其中首次接受曲妥珠单抗治疗患者211例(I-III期134例,IV期77例),再次接受曲妥珠单抗治疗患者36例(I-III期)。使用Cox比例风险回归和logistic回归分析首次或提前接受曲妥珠单抗治疗的患者的预后的临床结果,生存评估使用Kaplan-Meier法。结果:I-III期HER2+转移性乳腺癌患者中,未预先接受曲妥珠单抗治疗组的中位总生存期为36个月和预先接受曲妥珠单抗治疗组为28个月(危害比[HR],1.45;95%CI,1.05-2.02[P=0.012]);I-IV期HER2+转移性乳腺癌患者中,未预先使用曲妥珠单抗组的中位总生存期为37个月,客观缓解率58%;临床获益率77%;预先使用曲妥珠单抗组为25个月,客观缓解率28%;临床获益率37%;调整后的比值比为客观缓解率0.37(9%CI,0.18-0.77;P=0.010)和临床获益率0.28(95%CI,0.14-0.59;P=0.014)。单因素分析没有提前接受曲妥珠单抗治疗组中位总生存率较长(P=0.012)。多因素分析发现总生存率没有显著差异(P=0.19)。结论:当曲妥珠单抗用于转移性疾病,没有提前接受曲妥珠单抗治疗的HER2+乳腺癌患者临床结果优于提前接受曲妥珠单抗治疗的患者。     

Switching addictions between HER2 and FGFR2 in HER2-positive breast tumor cells: FGFR2 as a potential target for salvage after lapatinib failure

Agents that target HER2 have improved the prognosis of patients with HER2-amplified breast cancers. However, patients who initially respond to such targeted therapy eventually develop resistance to the treatment. We have established a line of lapatinib-resistant breast cancer cells (UACC812/LR) by chronic exposure of HER2-amplified and lapatinib-sensitive UACC812 cells to the drug. The mechanism by which UACC812/LR acquired resistance to lapatinib was explored using comprehensive gene hybridization. The FGFR2 gene in UACC812/LR was highly amplified, accompanied by overexpression of FGFR2 and reduced expression of HER2, and a cell proliferation assay showed that the IC₅₀ of PD173074, a small-molecule inhibitor of FGFR tyrosine kinase, was 10,000 times lower in UACC812/LR than in the parent cells. PD173074 decreased the phosphorylation of FGFR2 and substantially induced apoptosis in UACC812/LR, but not in the parent cells. FGFR2 appeared to be a pivotal molecule for the survival of UACC812/LR as they became independent of the HER2 pathway, suggesting that a switch of addiction from the HER2 to the FGFR2 pathway enabled cancer cells to become resistant to HER2-targeted therapy. The present study is the first to implicate FGFR in the development of resistance to lapatinib in cancer, and suggests that FGFR-targeted therapy might become a promising salvage strategy after lapatinib failure in patients with HER2-positive breast cancer.     

Identification of quinones as HER2 inhibitors for the treatment of trastuzumab resistant breast cancer

HER2 overexpression is associated with aggressive breast cancer with high recurrence rate and poor patient prognosis. Treatment of HER2 overexpressing patients with the HER2 targeting therapy trastuzumab results in acquired resistance within a year. The HER2/EGFR dual kinase inhibitor lapatinib was shown to inhibit some trastuzumab resistant breast cancer cell lines and is currently in clinical trials. Our group has found two new quinone compounds that show excellent inhibition of breast tumor cells expressing HER2 or the trastuzumab resistant HER2 oncogenic isoform, HER2Δ16. Compound 4 ((1R,2S,3S)-1,2,3,5,8-pentahydroxy-1,2,3,4-tetrahydroanthracene-9,10-dione) and compound 5 (5,8-dihydroxy-2,3-bis(hydroxymethyl)naphthalene-1,4-dione) showed sub-micromolar inhibition potency against these cell lines. These compounds also inhibit auto-phosphorylation of the Y1248 and Y1068 residues of HER2 and EGFR, respectively.     

HER2 阳性乳腺癌转移患者最佳治疗方案的研究进展

针对人表皮生长因子受体HER2 的靶向制剂曲妥珠单抗,显著改善了HER2 阳性乳腺癌转移患者疾病的发展状况,提高了 患者的总体生存期（OS）,然而耐药现象时有发生。其它靶向制剂如帕妥珠单抗,酪氨酸激酶受体抑制剂拉帕替尼和ado-transtusumab emtansine等克服了其耐药性,为治疗提供了更多选择。这些HER2 靶向制剂单用或联用已显示出良好的临床功效,但最 佳治疗次序依然未知。随着新型靶向制剂的出现,最佳治疗方案的研究成为热点。本篇综述重点阐述了目前HER2 阳性乳腺癌转 移患者最佳治疗方案的研究进展,以及新型靶向制剂的现有状况。     

Human Epidermal Growth Factor Receptor 2 (HER2) Impedes MLK3 Kinase Activity to Support Breast Cancer Cell Survival

Human epidermal growth factor receptor 2 (HER2) is amplified in ∼15–20% of human breast cancer and is important for tumor etiology and therapeutic options of breast cancer. Up-regulation of HER2 oncogene initiates cascades of events cumulating to the stimulation of transforming PI3K/AKT signaling, which also plays a dominant role in supporting cell survival and efficacy of HER2-directed therapies. Although investigating the underlying mechanisms by which HER2 promotes cell survival, we noticed a profound reduction in the kinase activity of a pro-apoptotic mixed lineage kinase 3 (MLK3) in HER2-positive (HER2+) but not in HER2-negative (HER2−) breast cancer tissues, whereas both HER2+ and HER2− tumors expressed a comparable level of MLK3 protein. Furthermore, the kinase activity of MLK3 was inversely correlated with HER2+ tumor grades. Moreover, HER2-directed drugs such as trastuzumab and lapatinib as well as depletion of HER2 or HER3 stimulated MLK3 kinase activity in HER2+ breast cancer cell lines. In addition, the noted inhibitory effect of HER2 on MLK3 kinase activity was mediated via its phosphorylation on Ser⁶⁷⁴ by AKT and that pharmacological inhibitors of PI3K/AKT prevented trastuzumab- and lapatinib-induced stimulation of MLK3 activity. Consistent with the pro-apoptotic function of MLK3, stable knockdown of MLK3 in the HER2+ cell line blunted the pro-apoptotic effects of trastuzumab and lapatinib. These findings suggest that HER2 activation inhibits the pro-apoptotic function of MLK3, which plays a mechanistic role in mediating anti-tumor activities of HER2-directed therapies. In brief, MLK3 represents a newly recognized integral component of HER2 biology in HER2+ breast tumors.     

慢病毒介导的RNA干涉对乳腺癌SKBR3细胞HER2受体的下调及生长抑制

大约30％的乳腺癌中有表皮生长因子受体家族蛋白HER2的过表达,此类癌症的预后差,恶性程度高。RNA干涉（RNAi）是最近发展起来能特异性抑制哺乳动物细胞中基因表达的新技术。本文在以往获得的能够产生良好基因沉默效应的小干涉RNA（siRNA）的基础上,构建了U6和H1双启动子siRNA表达载体,并转染HER2高表达乳腺癌SKBR3细胞定量测定了其HER2下调效应。随后,siRNA表达盒经LR重组反应被克隆入慢病毒载体中,在成功包装成病毒后,感染SKBR3并经荧光定量PCR、蛋白印迹杂交和流式细胞仪一系列实验证明慢病毒介导的RNAi确实能有效地下调肿瘤抗原HER2的表达。细胞长期增殖实验表明经慢病毒处理后细胞生长得到抑制。我们的研究为进一步阐明HER2与癌症恶化的关系以及发展新的基因治疗药物提供了工具和可能。     

89Zr-mAb3481 PET for HER3 tumor status assessment during lapatinib treatment

Treatment of human epidermal growth factor receptor 2 (HER2)-driven breast cancer with tyrosine kinase inhibitor lapatinib can induce a compensatory HER3 increase, which may attenuate antitumor efficacy. Therefore, we explored in vivo HER3 tumor status assessment after lapatinib treatment with zirconium-89 (⁸⁹Zr)-labeled anti-HER3 antibody mAb3481 positron emission tomography (PET). Lapatinib effects on HER3 cell surface expression and mAb3481 internalization were evaluated in human breast (BT474, SKBR3) and gastric (N87) cancer cell lines using flow cytometry. Next, in vivo effects of daily lapatinib treatment on⁸⁹Zr-mAb3481 BT474 and N87 xenograft tumor uptake were studied. PET-scans (BT474 only) were made after daily lapatinib treatment for 9 days, starting 3 days prior to ⁸⁹Zr-mAb3481 administration. Subsequently, ex vivo ⁸⁹Zr-mAb3481 organ distribution analysis was performed and HER3 tumor levels were measured with Western blot and immunohistochemistry. In vitro, lapatinib increased membranous HER3 in BT474, SKBR3 and N87 cells, and consequently mAb3481 internalization 1.7-fold (BT474), 1.4-fold (SKBR3) and 1.4-fold (N87). ⁸⁹Zr-mAb3481 BT474 tumor uptake was remarkably high at SUV_mean 5.6±0.6 (51.8±7.7%ID/g) using a 10 μg ⁸⁹Zr-mAb3481 protein dose in vehicle-treated mice. However, compared to vehicle, lapatinib did not affect ⁸⁹Zr-mAb3481 ex vivo uptake in BT474 and N87 tumors, while HER3 tumor expression remained unchanged. In conclusion, lapatinib increased in vitro HER3 tumor cell expression, but not when these cells were xenografted. ⁸⁹Zr-mAb3481 PET accurately reflected HER3 tumor status. ⁸⁹Zr-mAb3481 PET showed high, HER3-specific tumor uptake, and such an approach might sensitively assess HER3 tumor heterogeneity and treatment response in patients.