YES1 activation induces acquired resistance to neratinib in HER2‐amplified breast and lung cancers

Molecular‐targeted therapies directed against human epidermal growth factor receptor 2 (HER2) are evolving for various cancers. Neratinib is an irreversible pan‐HER tyrosine kinase inhibitor and has been approved by the FDA as an effective drug for HER2‐positive breast cancer. However, acquired resistance of various cancers to molecular‐targeted drugs is an issue of clinical concern, and emergence of resistance to neratinib is also considered inevitable. In this study, we established various types of neratinib‐resistant cell lines from HER2‐amplified breast and lung cancer cell lines using several drug exposure conditions. We analyzed the mechanisms of emergence of the resistance in these cell lines and explored effective strategies to overcome the resistance. Our results revealed that amplification of YES1, which is a member of the SRC family, was amplified in two neratinib‐resistant breast cancer cell lines and one lung cancer cell line. Knockdown of YES1 by siRNA and pharmacological inhibition of YES1 by dasatinib restored the sensitivity of the YES1‐amplified cell lines to neratinib in vitro. Combined treatment with dasatinib and neratinib inhibited tumor growth in vivo. This combination also induced downregulation of signaling molecules such as HER2, AKT and MAPK. Our current results indicate that YES1 plays an important role in the emergence of resistance to HER2‐targeted drugs, and that dasatinib enables such acquired resistance to neratinib to be overcome.     

Lapatinib耐药性HER2阳性乳腺癌细胞株的建立及鉴定

目的:为研究HER2阳性乳腺癌细胞获得拉帕替尼耐药性的机制,建立稳定具有拉帕替尼耐药性的细胞株。方法:采用2μmol/L的拉帕替尼处理HER2阳性乳腺癌细胞BT-474,维持12个月,使细胞获得稳定耐药性。然后分别利用MTT、平板克隆和软琼脂克隆形成能力分析等方法,评价所建立耐药细胞的耐药能力。结果:所建立的耐药细胞在细胞增殖能力、平板克隆形成能力和软琼脂克隆形成能力等方面均具有耐药性。结论:建立的拉帕替尼耐药性细胞BT-474具有稳定的耐药性,为后续机制研究奠定基础。     

The inflammatory chemokines CCL2 and CCL5 in breast cancer

A causal role was recently attributed to inflammation in many malignant diseases, including breast cancer. The different inflammatory mediators that are involved in this disease include cells, cytokines and chemokines. Of these, many studies have addressed the involvement and roles of the inflammatory chemokines CCL2 (MCP-1) and CCL5 (RANTES) in breast malignancy. While minimally expressed by normal breast epithelial duct cells, both chemokines are highly expressed by breast tumor cells at primary tumor sites, indicating that CCL2 and CCL5 expression is acquired in the course of malignant transformation, and suggesting that the two chemokines play a role in breast cancer development and/or progression. Supporting this possibility are findings showing significant associations between CCL2 and CCL5 and more advanced disease course and progression. Furthermore, studies in animal model systems have shown active and causative roles for the two chemokines in this disease. In line with the tumor-promoting roles of CCL2 and CCL5 in breast cancer, the two chemokines were shown to mediate many types of tumor-promoting cross-talks between the tumor cells and cells of the tumor microenvironment: (1) they shift the balance at the tumor site between different leukocyte cell types by increasing the presence of deleterious tumor-associated macrophages (TAM) and inhibiting potential anti-tumor T cell activities; (2) of the two chemokines, mainly CCL2 promotes angiogenesis; (3) CCL2 and CCL5 which are expressed by cells of the tumor microenvironment osteoblasts and mesenchymal stem cells play a role in breast metastatic processes. In addition, both chemokines act directly on the tumor cells to promote their pro-malignancy phenotype, by increasing their migratory and invasion-related properties. Together, the overall current information suggests that CCL2 and CCL5 are inflammatory mediators with pro-malignancy activities in breast cancer, and that they should be considered as potential therapeutic targets for the limitation of this disease.     

Y-box factor YB-1 predicts drug resistance and patient outcome in breast cancer independent of clinically relevant tumor biologic factors HER2, uPA and PAI-1.

Intrinsic or acquired resistance to chemotherapy is responsible for failure of current treatment regimens in breast cancer patients. The Y-box protein YB-1 regulates expression of the P-glycoprotein gene mdr1, which plays a major role in the development of a multidrug-resistant tumor phenotype. In human breast cancer, overexpression and nuclear localization of YB-1 is associated with upregulation of P-glycoprotein. In our pilot study, we analyzed the clinical relevance of YB-1 expression in breast cancer (n = 83) after a median follow-up of 61 months and compared it with tumor-biologic factors already used for clinical risk-group discrimination, i.e., HER2, urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor type 1 (PAI-1). High YB-1 expression in tumor tissue and surrounding benign breast epithelial cells was significantly associated with poor patient outcome. In patients who received postoperative chemotherapy, the 5-year relapse rate was 66% in patients with high YB-1 expression. In contrast, in patients with low YB-1 expressions, no relapse has been observed so far. YB-1 expression thus indicates clinical drug resistance in breast cancer. Moreover, YB-1 correlates with breast cancer aggressiveness: in patients not treated with postoperative chemotherapy, those with low YB-1 expression are still free of disease, whereas the 5-year relapse rate in those with high YB-1 was 30%. There was no significant correlation between YB-1 expression and either HER2 expression or uPA and PAI-1 levels. Risk-group assessment achieved by YB-1 differed significantly from that by HER2 or uPA/PAI-1. In conclusion, YB-1 demonstrated prognostic and predictive significance in breast cancer by identifying high-risk patients in both the presence and absence of postoperative chemotherapy, independent of tumor-biologic factors currently available for clinical decision making.     

Anti‐tumor activity of the ATR inhibitor AZD6738 in HER2 positive breast cancer cells

Ataxia telangiectasia and Rad3‐related (ATR) proteins are sensors of DNA damage, which induces homologous recombination (HR)‐dependent repair. ATR is a master regulator of DNA damage repair (DDR), signaling to control DNA replication, DNA repair and apoptosis. Therefore, the ATR pathway might be an attractive target for developing new drugs. This study was designed to investigate the antitumor effects of the ATR inhibitor, AZD6738 and its underlying mechanism in human breast cancer cells. Growth inhibitory effects of AZD6738 against human breast cancer cell lines were studied using a 3‐(4,5‐dimethylthiazol‐2‐yl)?2,5‐diphenyltetrazolium bromide (methyl thiazolyl tetrazolium, MTT) assay. Cell cycle analysis, Western blotting, immunofluorescence and comet assays were also performed to elucidate underlying mechanisms of AZD6738 action. Anti‐proliferative and DDR inhibitory effects of AZD6738 were demonstrated in human breast cancer cell lines. Among 13 cell lines, the IC₅₀ values of nine cell lines were less than 1 μmol/L using MTT assay. Two cell lines, SK‐BR‐3 and BT‐474, were chosen for further evaluation focused on human epidermal growth factor receptor 2 (HER2)‐positive breast cancer cells. Sensitive SK‐BR‐3 but not the less sensitive BT‐474 breast cancer cells showed increased level of apoptosis and S phase arrest and reduced expression levels of phosphorylated check‐point kinase 1 (CHK1) and other repair markers. Decreased functional CHK1 expression induced DNA damage accumulation due to HR inactivation. AZD6738 showed synergistic activity with cisplatin. Understanding the antitumor activity and mechanisms of AZD6738 in HER2‐positive breast cancer cells creates the possibility for future clinical trials targeting DDR in HER2‐positive breast cancer treatment.     

Src激酶抑制剂ZD6474在乳腺癌MCF-7细胞转移中的作用和机制

目的:探讨Src激酶抑制剂ZD6474在乳腺癌MCF-7细胞转移中的作用和机制。方法:乳腺癌MCF-7细胞经ZD6474处理后,检测肿瘤细胞体外黏附、侵袭能力的改变,应用Western blot及Real-time PCR观察细胞Src激酶磷酸化水平及E-钙黏素和β-连环蛋白表达的变化,报告基因技术检测Snail在转录水平表达的变化。结果:ZD6474可抑制MCF-7细胞中Src激酶活性,在ZD6474浓度为1×10-5mol/L和1×10-4mol/L时,细胞的抑制率分别为12.2%和27.5%。Src酪氨酸激酶抑制剂可上调E-cadherin在mRNA和蛋白表达水平,下调β-catenin在mRNA和蛋白表达水平及Snail启动子活性。结论:Src激酶与乳腺癌MCF-7细胞肿瘤转移能力密切相关,阻断Src激酶活性可抑制肿瘤细胞转移能力。     

c‐Src inhibitor selectively inhibits triple‐negative breast cancer overexpressed Vimentin in vitro and in vivo

Oncogene c‐Src has been found to be a potential target for the treatment of triple‐negative breast cancer (TNBC). However, the therapeutic effects of the c‐Src inhibitor on TNBC patients are controversial compared to those on cell lines. The molecular mechanisms of the inhibitory effects of the c‐Src inhibitor on TNBC remain unclear. Herein, we showed that a specific c‐Src inhibitor, PP2, was effective in inhibiting phosphorylation of c‐Src in 4 cell lines: T‐47D, SK‐BR‐3, SUM1315MO2, and MDA‐MB‐231, regardless of hormone receptors and human epidermal growth factor receptor 2 (HER2) expression levels. Giving PP2 preferentially reduced the S phase of cell cycles and inhibited colony formation in SUM1315MO2 and MDA‐MB‐231, but not in SK‐BR‐3 and T‐47D cells. Furthermore, PP2 effectively blocked cell migration/invasion and epithelial‐mesenchymal transition (EMT) in TNBC cell lines, SUM1315MO2 and MDA‐MB‐231. An EMT biomarker, vimentin, was highly expressed in 2 TNBC cell lines when they were compared with SK‐BR‐3 and T‐47D cells. Further depletion of vimentin by shRNA remarkably attenuated the inhibitory effects of the c‐Src inhibitor on TNBC cells in vitro and in vivo, indicating a crucial action of vimentin to affect the function of c‐Src in TNBC. This study provides an important rationale for the clinic to precisely select TNBC patients who would benefit from c‐Src inhibitor treatment. This finding suggests that traditional markers for TNBC are not sufficient to precisely define this aggressive type of cancer. Vimentin is identified as an important biomarker to enable categorization of TNBC.     

Trastuzumab‐based neoadjuvant therapy in patients with HER2‐positive breast cancer

Overexpression, or gene amplification, of the human epidermal growth factor receptor 2 (HER2) is evident in 20% to 25% of breast cancers. The biologic agent trastuzumab is an HER2‐targeted monoclonal antibody that inhibits the proliferation of tumor cells and induces tumor cell death through multiple mechanisms of action. Currently, trastuzumab is approved for use in the adjuvant and metastatic settings. Trials combining trastuzumab with neoadjuvant chemotherapy suggest that patients with HER2‐positive breast cancer also may benefit from preoperative trastuzumab. For this article, the author reviewed efficacy and safety data from key studies of patients who received neoadjuvant trastuzumab‐based therapy. Studies were identified from literature searches of publication and congress databases. The results of 3 large phase 3 trials (the M. D. Anderson Cancer Center neoadjuvant trastuzumab trial, the Neoadjuvant Herceptin [NOAH] trial, and the German Breast Group/Gynecologic Oncology Study Group “GeparQuattro” trial) demonstrated that, compared with chemotherapy alone, neoadjuvant trastuzumab plus chemotherapy significantly increased pathologic complete response rates to as high as 65%. Improvements in disease‐free, overall, and event‐free survival also were reported in the NOAH trial. In addition to demonstrated efficacy, a low incidence of cardiac dysfunction suggests that neoadjuvant trastuzumab is both effective and well tolerated. Similar results have been reported in a range of phase 2 studies using different trastuzumab‐based regimens. These encouraging data led the National Comprehensive Cancer Network to recommend treating patients who have operable, locally advanced, HER2‐positive breast cancer with neoadjuvant paclitaxel plus trastuzumab followed by 5‐fluorouracil, epirubicin, and cyclophosphamide plus trastuzumab. Cancer 2010. © 2010 American Cancer Society.     

c-Met蛋白在CCL5诱导的乳腺癌MDA-MB-231细胞迁移中的作用

目的:探讨c-Met蛋白在CC型趋化因子5(CCL5)诱导的乳腺癌MDA-MB-231细胞迁移中的作用.方法:Western-Blot检测乳腺癌MDA-MB-231细胞表面CCL5受体(CCR5)的表达情况;Transwell法检测CCL5诱导的MDA-MB-231细胞迁移能力的变化;Western-Blot检测CCL5刺激后MDA-MB-231细胞c-Met及磷酸化c-Met(p-Met)的表达.结果:乳腺癌MDA-MB-231细胞表面高表达CCR5蛋白;CCL5增强MDA-MB-231细胞的迁移能力,沉默CCR5基因后抑制了CCR5蛋白表达,MDA-MB-231细胞迁移能力降低;MDA-MB-231细胞表达的p-Met水平在CCL5刺激10 min后明显升高.结论:CCL5/CCR5信号通路可以促进乳腺癌MDA-MB-231细胞的迁移能力,c-Met蛋白参与CCL5诱导的乳腺癌MDA-MB-231细胞迁移.     

Neuromedin U alters bioenergetics and expands the cancer stem cell phenotype in HER2‐positive breast cancer

Neuromedin U (NmU) is a neuropeptide belonging to the neuromedin family. Recently, we reported a significant association between NmU and breast cancer, particularly correlating with increased aggressiveness, resistance to HER2‐targeted therapies and overall significantly poorer outcome for patients, although the mechanism through which it exerts this effect remained unexplained. Investigating this, here we found that ectopic over‐expression of NmU in HER2‐positive breast cancer cells induced aberrant metabolism, with increased glycolysis, likely due to enhanced pyruvate dehydrogenase kinase activity. Similar results were observed in HER2‐targeted drug‐resistant cell variants, which we had previously shown to display increased levels of NmU. Overexpression of NmU also resulted in upregulation of epithelial‐mesenchymal transition markers and increased IL‐6 secretion which, together with aberrant metabolism, have all been associated with the cancer stem cell (CSC) phenotype. Flow cytometry experiments confirmed that NmU‐overexpressing and HER2‐targeted drug‐resistant cells showed an increased proportion of cells with CSC phenotype (CD44⁺/CD24^–). Taken together, our results report a new mechanism of action for NmU in HER2‐overexpressing breast cancer that enhances resistance to HER2‐targeted drugs through conferring CSC characteristics and expansion of the CSC phenotype.     

Significant association between high serum CCL5 levels and better disease‐free survival of patients with early breast cancer

Analysis of anticancer immunity aids in assessing the prognosis of patients with breast cancer. From 250 operated breast cancers, we focused on serum levels of C‐C motif chemokine ligand 5 (CCL5), which is involved in cancer immune reactions. Serum levels of CCL5 were measured using a cytometric bead‐based immunoassay kit and CCL5 expression in cancer cells was determined using immunohistochemical staining. In addition, mRNA in cancer and stromal cells was analyzed by microdissection and comparison with the public dataset. Disease‐free survival (DFS) of patients with high CCL5 levels (cut‐off, 13.87 ng/mL; n = 192) was significantly better than those with low CCL5 levels (n = 58; hazard ratio, 0.20; 95% confidence interval, 0.10‐0.39; P < .0001). An improved overall survival was observed in patients with high CCL5 levels compared to those with low CCL5 levels (P = .024). On the contrary, high immunohistochemical expression of CCL5 in cancer cells was significantly associated with decreased DFS. As serum CCL5 levels did not correlate with CCL5 expression in cancer cells and the relative expression of mRNA CCL5 was elevated in stromal cells in relation to cancer cells, serum CCL5 might be derived not from cancer cells, but from stromal cells. Expression of CCL5 in serum, but not in cancer cells, might contribute to improved patient prognosis mediating through not only immune reaction, but through other mechanisms. Determination of circulating CCL5 levels could be useful for predicting patient prognosis.     

Expression of CD24 is associated with HER2 expression and supports HER2‐Akt signaling in HER2‐positive breast cancer cells

Human epidermal growth factor receptor 2 (HER2)‐positive breast cancer is treated with HER2‐targeted agents, such as trastuzumab and lapatinib, that suppress signaling by phosphatidylinositol 3‐kinase (PI3K)‐Akt and MAPK pathways. However, resistance to HER2‐targeted therapy remains a major clinical problem. Overexpression of CD24 has been detected in many cancers and is associated with a poor prognosis in women with breast cancer. HER2‐positive breast tumors are predominantly positive for CD24, suggesting that the expression of the two molecules is related. To investigate the relation between HER2 and CD24, we overexpressed HER2 in breast cancer cells that were triple‐negative for the estrogen receptor, progesterone receptor and HER2. We found that expression of CD24 was increased by stable overexpression of HER2. Flow cytometry thus revealed that the percentage of CD24‐positive cells was markedly higher in the HER2‐positive fraction than in the HER2‐negative fraction. Knockdown of CD24 in breast cancer cells positive for endogenous HER2 downregulated HER2 expression, whereas knockdown of HER2 did not affect the expression of CD24. Knockdown of CD24 also suppressed the phosphorylation of Akt, which functions downstream of HER2 and PI3K to promote cell survival. Moreover, knockdown of CD24 increased the sensitivity of HER2‐positive breast cancer cells to lapatinib treatment. Our results thus indicate that CD24 supports both the expression of HER2 and the consequent activation of PI3K‐Akt signaling. Furthermore, CD24 may contribute to resistance to HER2‐targeted therapy and, therefore, is itself a potential therapeutic target in HER2‐positive breast cancer.     

Disruption of the blood brain barrier by brain metastases of triple‐negative and basal‐type breast cancer but not HER2/neu‐positive breast cancer

BACKGROUND:

Generally, the blood‐brain barrier (BBB) of brain metastasis was thought to be disrupted.

METHODS:

We retrospectively performed immunohistochemical staining for glucose transporter 1 (GLUT1) and breast cancer resistance protein (BCRP) to evaluate the status of the BBB in resected brain metastases. Associations between expression of GLUT1 and/or BCRP and the immunohistochemical profiles of breast cancers, such as the statuses of hormone receptors, human epidermal growth factor receptor 2 (HER2/neu), and a basal‐type marker (cytokeratin 5/6, HER1), were also analyzed.

RESULTS:

The study included 29 breast cancer patients with brain metastasis who had undergone brain tumor resections. Among the 29 patients, there was no expression of GLUT1 and BCRP in the intratumor microvessels of 9 (32%) and 11 (38%) patients, respectively. There was no expression of both GLUT1 and BCRP in 8 patients (28%). The expression of GLUT1 was significantly associated with that of BCRP (P < .001). A positive correlation was observed between the expression of GLUT1 and/or BCRP and brain metastases of HER2/neu‐positive breast cancer (P = .012), while a negative correlation was observed between the expression of GLUT1 and/or BCRP and brain metastases of triple negative or basal‐type breast cancer (P = .014 and P = .003 for triple negative and basal‐type, respectively).

CONCLUSIONS:

Brain metastases of triple negative or basal‐type breast cancers may often disrupt the BBB, whereas brain metastases of HER2/neu‐positive breast cancer tend to preserve the BBB. Cancer 2010. © 2010 American Cancer Society.     

乳腺癌芳香化酶抑制剂耐药分子机制研究进展

芳香化酶抑制剂（ aromatase inhibitors,AIs）在绝经后雌激素依赖性乳腺癌的治疗中取得了令人鼓舞的疗效。大型的临床试验ATAC和BIG 1-98均证明第三代芳香化酶抑制剂作为绝经后乳腺癌的辅助治疗可明显提高患者的无病生存期,疗效优于他莫昔芬。随着AIs在临床广泛应用及用药时间的延长,AIs耐药也成了临床医生不可回避的问题,至今国内尚没有对AIs耐药分子机制的详细报道,本文通过对国内外一些实验室和临床研究结果的综述,拟概述乳腺癌AIs耐药分子机制的研究进展。     

Role of inhibitor of yes‐associated protein 1 in triple‐negative breast cancer with taxol‐based chemoresistance

Triple‐negative breast cancer (TNBC) is highly clinically aggressive and taxol‐based chemoresistance remains a big TNBC therapeutic problem to be solved. Verteporfin, a small molecular yes‐associated protein 1 (YAP1) inhibitor, is little known as an antitumor drug for TNBC. Our data showed that YAP1 expression was associated with early relapse in tissue samples of patients with TNBC taxol chemoresistance (P < .001). Verteporfin reduced migration and enhanced apoptosis or autophagy of a taxol‐resistant MDA‐MB‐231 cell line in vitro. Knockdown of YAP1 increased epithelial‐mesenchymal transition response in a taxol‐resistant TNBC cell line. In an in vivo experiment, we found that verteporfin was able to shrink tumor weight and volume and decreased Ki67 expression in a taxol‐resistant mouse model. Our results provide evidence that verteporfin could be a chemosensitizer for TNBC patients with taxol‐based treatment.