Decreased response to paclitaxel versus docetaxel in HER-2/neu transfected human breast cancer cells

Taxanes are effective in the treatment of metastatic breast cancer. Docetaxel has been shown to be more potent than paclitaxel in inducing bcl-2 phosphorylation and apoptosis and is clinically active in some paclitaxel-resistant breast tumors. HER-2/neu overexpression has been shown to correlate with resistance to hormonal therapy as well as chemotherapy. Using a HER-2/neu transfected MCF-7 human breast cancer cell line, we investigated the role of HER-2/neu overexpression on resistance to paclitaxel and docetaxel treatment. A control vector transfected MCF-7 human breast cancer cell line (MCF/neo) and a HER-2/neu transfected MCF-7 line (MCF/18) were treated with various concentrations of docetaxel or paclitaxel. Cell number was assessed using the MTT tetrazolium dye assay. In the control vector transfected MCF/neo cell line, paclitaxel and docetaxel gave similar dose-dependent growth inhibition ( p = 0.175). In HER-2/neu transfected MCF/18 cells, docetaxel treatment resulted in a dose-dependent inhibition similar to that seen in MCF/neo cells. Paclitaxel, however, gave significantly less growth inhibition than docetaxel in the HER-2/neu overexpressing MCF/18 cells (p = 0.0003). These data suggest that HER-2/neu overexpression may contribute to paclitaxel resistance. In contrast, the cytotoxic effects of docetaxel in these breast carcinoma cells are not affected by HER-2/neu expression. Therefore, docetaxel may be the preferred taxane therapy in HER-2/neu overexpressing breast tumors.     

Combining flavopiridol with various signal transduction inhibitors

Treatment of human tumors with a combination of chemotherapeutic agents results in improved response as well as the ability to use less toxic concentrations of the drugs. Recent phase I clinical trials with the cyclin-dependent kinase inhibitor, flavopiridol, have shown some promise in the treatment of a variety of human tumors. Because of the severe toxicity, however, the use of less toxic doses in combination with other antiproliferative agents would be desirable. The purpose of this study was to examine the effects of combining flavopiridol with several signal transduction inhibitors: the SC236 COX-2 inhibitor, a PKC kinase inhibitor and LY294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor in a control vector transfected MCF-7 human breast cancer cell line (MCF/neo) and a HER-2/neu transfected MCF-7 cell line (MCF/18). Enhanced (better than that seen with either agent alone but not additive) growth inhibition was observed in both cell lines with the combination of flavopiridol and the PKC kinase inhibitor. The combination of flavopiridol and the SC236 COX-2 inhibitor resulted in an enhanced effect in the MCF/18 cell line and a synergistic effect in the MCF/neo cells. The combination of flavopiridol and LY294002 resulted in a synergistic effect in the MCF/18 cell line and an additive effect in the MCF/neo cells. These data suggest that combinations of flavopiridol and signal transduction inhibitors warrant further studies as treatments for breast tumors, and that HER-2/neu expression may influence the choice of inhibitor to combine with flavopiridol.     

Automated electrorotation to reveal dielectric variations related to HER-2/neu overexpression in MCF-7 sublines.

PURPOSE: Electrorotation (ROT) is a technique that allows for determination of the dielectric properties of living cells when exposed to a rotating electric field. We evaluated the ROT behavior of MCF/neo and p185(neu) transfectancts MCF/HER2-11 and MCF/HER2-18 to investigate whether differences in HER-2/neu expression were associated with differences in dielectric properties in these cells. Experimental Design: P185(neu) was measured by Western blotting in MCF/neo cells and HER-2/neu transfectants MCF/HER2-11 and MCF/HER2-18. ROT spectra and cell membrane-specific capacitance were obtained for each cell line. RESULTS: The mean cell membrane-specific capacitance values for MCF/neo, MCF/HER2-11, and MCF/HER2-18 were 2.09, 1.70, and 2.56 microF/cm(2), respectively. The mean specific capacitance for MCF/neo was significantly different from that for MCF/HER2-11 (P = 0.006) and that for MCF/HER2-18 (P = 0.007). CONCLUSIONS: ROT is sufficiently sensitive to detect variations in dielectric properties in breast cancer cell lines overexpressing p185(neu). These differences may be related to the morphological alterations determined by HER-2/neu overexpression.     

Synergistic inhibition of breast cancer cell lines with a dual inhibitor of EGFR-HER-2/neu and a Bcl-2 inhibitor

The epidermal growth factor receptor (EGFR) (ErbB1) and HER-2/neu (ErbB2) are members of the ErbB family of receptor tyrosine kinases. These receptors are overexpressed in a variety of human tumors and overexpression generally correlates with poor prognosis and decreased survival. Lapatinib, a reversible inhibitor of both EGFR and HER-2/neu, has shown some success in achieving clinical responses in heavily pretreated advanced cancer patients. GW2974 is a reversible dual inhibitor similar to lapatinib, but GW2974 was not progressed to clinical trials due to pharmacokinetic issues. Bcl-2, an anti-apoptotic protein, is also overexpressed in a number of human tumors. Bcl-2 inhibitors induce apoptosis and sensitize cancer cells to other therapies. The purpose of this study was to assess the effects of combining ErbB and Bcl-2 inhibitors on the growth of human breast cancer cell lines. EGFR/HER-2/neu tyrosine kinase inhibitors (lapatinib and GW2974) were combined with Bcl-2 inhibitors (HA14-1 or GX15-070) and the anti-proliferative effects were determined by the MTT tetrazolium dye assay. Combinations were tested in MCF-7 human breast cancer cells, a HER-2/neu transfected MCF-7 cell line (MCF/18), and a tamoxifen-resistant MCF-7 cell line (MTR-3). A synergistic inhibitory effect was observed with the combination of inhibitors of EGFR-HER-2/neu (lapatinib or GW2974) and Bcl-2 (GX15-070 or HA14-1) on the growth of the MCF-7, MCF/18, and MTR-3 human breast cancer cell lines. This study suggests that simultaneously blocking the ErbB family of receptor tyrosine kinases and Bcl-2 family of proteins may be a benefit to breast cancer patients.     

Mechanisms of tumor regression and resistance to estrogen deprivation and fulvestrant in a model of estrogen receptor-positive, HER-2/neu-positive breast cancer

HER-2/neu in breast cancer is associated with tamoxifen resistance, but little data exist on its interaction with estrogen deprivation or fulvestrant. Here, we used an in vivo xenograft model of estrogen receptor (ER)-positive breast cancer with HER-2/neu overexpression (MCF7/HER-2/neu-18) to investigate mechanisms of growth inhibition and treatment resistance. MCF7/HER-2/neu-18 tumors were growth inhibited by estrogen deprivation and with fulvestrant, but resistance developed in 2 to 3 months. Inhibited tumors had reductions in ER, insulin-like growth factor-I receptor (IGF-IR), phosphorylated HER-2/neu (p-HER-2/neu), and phosphorylated p42/44 mitogen-activated protein kinase (p-MAPK). p27 was increased especially in tumors sensitive to estrogen deprivation. Tumors with acquired resistance to these therapies had complete loss of ER, increased p-HER-2/neu, increased p-MAPK, and reduced p27. In contrast, IGF-IR and phosphorylated AKT (p-AKT) levels were markedly reduced in these resistant tumors. The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor gefitinib, which can block EGFR/HER-2/neu signaling, significantly delayed the emergence of resistance to both estrogen deprivation and fulvestrant. Levels of p-MAPK and p-AKT decreased with gefitinib, whereas high ER levels were restored. Eventually, however, tumors progressed in mice treated with gefitinib combined with estrogen deprivation or fulvestrant accompanied again by loss of ER and IGF-IR, increased p-HER-2/neu, high p-MAPK, and now increased p-AKT. Thus, estrogen deprivation and fulvestrant can effectively inhibit HER-2/neu-overexpressing tumors but resistance develops quickly. EGFR/HER-2/neu inhibitors can delay resistance, but reactivation of HER-2/neu and signaling through AKT leads to tumor regrowth. Combining endocrine therapy with EGFR/HER-2/neu inhibitors should be tested in clinical breast cancer, but a more complete blockade of EGFR/HER-2/neu may be optimal.     

Combining doxorubicin and liposomal anti-HER-2/NEU antisense oligodeoxynucleotides to treat HER-2/NEU-expressing MDA-MB-435 breast tumor model

This study assessed the in vivo therapeutic activity of an antisense molecule targeted against HER-2/neu expressing mRNA. Antisense activity was evaluated in female SCID/Rag2m mice bearing subcutaneous tumors derived from HER-2/neu-transfected MDA-MB-435 (MDA-MB-435(HER2)) cells, a transfected line derived from the human breast cancer MDA-MB-435 cell line. Animals were treated with free or liposome-encapsulated antisense. The area under the curve (AUC(0-24h)) of the liposomal formulated antisense was demonstrated to be more than 30-fold greater than that of free antisense following intravenous administration. Efficacy was determined by assessing changes in tumor growth rate as well as by an immunohistological end-point evaluating HER-2/neu expression. HER-2/neu protein expression was reduced in mice bearing HER-2/neu-transfected MDA-MB-435 tumors when treated with liposomal antisense. However, tumors in these mice grew at a faster rate than the control, a result that was interpreted to be a consequence of selection of a more rapidly proliferating HER-2/neu-negative subpopulation of cells. Effective control of the MDA-MB-435(HER2) tumors was achieved when antisense treatment was combined with doxorubicin. Tumors derived from animals treated with the combination of doxorubicin and the liposomal antisense against HER-2/neu exhibited no detectable levels of HER-2/neu expression. Antisense targeted against HER-2/neu mRNA was effective in reducing or eliminating HER-2/neu protein expression, and when combined wtih doxorubicin treatment was efficacious in the treatment of mice bearing HER-2/neu-overexpressing human xenograft tumors.     

Restoration of estrogen responsiveness by blocking the HER-2/neu pathway

HER-2/neu gene amplification or protein overexpression is evident in 20-30% of primary breast cancers. Its amplification correlates with poor prognosis. There appears to be an association between HER-2/neu overexpression and estrogen independence. The MCF-7 human breast carcinoma cell line is estrogen-dependent and sensitive to the anti-estrogen, tamoxifen (TAM). This line, when transfected with the HER-2/neu gene, becomes estrogen-independent and resistant to TAM. Blockade of the HER-2/neu receptor with 1-5 nM of the humanized HER-2/neu antibody, Herceptin, restored estrogen, as well as TAM, sensitivity. These results suggest that Herceptin or similar drugs may restore estrogen sensitivity and the administration of a HER-2/neu inhibitor with an anti-estrogen to premenopausal patients should be considered.     

Synergistic interactions between tamoxifen and trastuzumab (Herceptin).

PURPOSE: HER-2/neu and estrogen receptor (ER) are critical in the biology of breast carcinoma, and both are validated therapeutic targets. Extensive interactions between the signaling pathways of these receptors have been demonstrated. This suggests that targeting both receptors simultaneously may have a dramatic effect on the biology of breast cancer. This hypothesis was tested in cell culture experiments. EXPERIMENTAL DESIGN: ER-positive, HER-2/neu-overexpressing BT-474 human breast carcinoma cells were cultured in the presence of the anti-HER-2/neu therapeutic antibody trastuzumab (Herceptin), the antiestrogen tamoxifen, or both. The effects on cell growth, cell cycle distribution, clonogenicity, survival, and the level and activity of HER-2/neu were examined. RESULTS: The combination of tamoxifen and Herceptin resulted in synergistic growth inhibition and enhancement of cell accumulation in the G(0)-G(1) phase of the cell cycle, with a decrease in cells in S phase. Clonogenicity was inhibited in the presence of each drug and more so by the combination, although prior exposure to drugs did not affect subsequent clonogenicity in drug-free media, and neither drug nor the combination induced apoptosis. Herceptin, but not tamoxifen, inhibited signaling by HER-2/neu. CONCLUSIONS: The combination of tamoxifen and Herceptin is formally demonstrated to result in synergistic growth inhibition and enhancement of G(0)-G(1) cell cycle accumulation. In vitro, the individual drugs or combination produces a cytostatic effect. These results suggest that combined inhibition of ER and HER-2/neu signaling may represent a powerful approach to the treatment of breast cancer.     

Tyrphostin AG825 triggers p38 mitogen-activated protein kinase-dependent apoptosis in androgen-independent prostate cancer cells C4 and C4-2

Prostate cancer (PCa) progression is aided by abnormal autocrine growth factor loops. We screened for small cell-permeable inhibitors of receptor tyrosine kinases that could block their signaling and trigger cell death in PCa cell lines. We found that the human epidermal growth factor receptor (HER)-2/neu inhibitor tyrphostin AG825 is preferentially toxic to PCa cells that are phenotypically androgen independent. These effects were dose and time dependent in the human LNCaP, C4, and C4-2 cell line models of progression and correlated with the inhibition of HER-2/neu phosphoactivation and its down-regulation. In addition, we show that the inhibition of HER-2/neu signaling with AG825 triggers an imbalance between extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase activation, which leads to p38-dependent apoptosis. Inhibition of HER-1 with Compound 56 had no effect. These findings suggest that the androgen-independent C4 and C4-2 cells can be killed by selectively inhibiting their HER-2/neu signaling pathway and provide insights into the mechanism of action of AG825 in PCa cells.     

Amplification of HER-2 in gastric carcinoma: association with Topoisomerase IIalpha gene amplification, intestinal type, poor prognosis and sensitivity to trastuzumab.

BACKGROUND: HER-2/neu gene amplification has predictive value in breast cancer patients responding to trastuzumab. We wanted to investigate the frequency and clinical significance of HER-2/neu amplification in gastric carcinoma. PATIENTS AND METHODS: The frequency of HER-2/neu and Topoisomerase IIalpha gene amplification was studied in adenocarcinomas of the stomach (n=131) and the gastroesophageal junction (n=100) by chromogenic in situ hybridization (CISH). Sensitivity of a gastric cancer cell line N87 with HER-2/neu amplification to trastuzumab was studied by a cell viability assay and compared with that of a HER-2 amplified breast cancer cell line SKBR-3. Growth inhibition of N87 cells was also verified in vivo in N87 xenograft tumors. RESULTS: HER-2/neu amplification was present in 16 (12.2%) of the 131 gastric and in 24 (24.0%) of the 100 gastroesophageal adenocarcinomas. Co-amplification of Topoisomerase IIalpha was present in the majority of gastric (63%) and esophagogastric junction cancers (68%) with HER-2/neu amplification. HER-2/neu amplification was more common in the intestinal histologic type of gastric cancer (21.5%) than in the diffuse (2%) or the mixed/anaplastic type (5%, P=0.0051), but it was not associated with gender, age at diagnosis or clinical stage. Presence of HER-2/neu amplification was associated with poor carcinoma-specific survival (P=0.0089). HER-2/neu targeting antibody trastuzumab inhibited the growth of a p185(HER-2/neu) overexpressing gastric and breast carcinoma cell lines (N87 and SKBR-3) with equal efficacy. CONCLUSIONS: HER-2/neu amplification is common in the intestinal type of gastric carcinoma, and it is associated with a poor outcome. HER-2 might be a useful target in this disease, and this hypothesis deserves to be investigated in clinical trials.     

人COX-2基因反义真核表达载体对胃癌转移的影响

目的：在成功构建人COX-2基因反义真核表达载体的基础上,研究COX-2基因对人胃癌细胞株SGC-7901转移能力的影响。方法：实验分为COX-2基因反义真核表达载体转染的人胃癌细胞株SGC-7901转染组、COX-2抑制剂SC236处理组（SGC-7901细胞培养基内含100μmol/L SC236）和对照组（SGC-7901细胞）,并分别采用细胞体外侵袭实验,内皮细胞体外迁移实验,观察各组细胞体外转移的情况。采用裸鼠皮下移植瘤抑制实验,用转染和未转染的SGC-7901细胞按每毫升5×10~7个的细胞悬液分别注射于BALB/C-nu/nu无胸腺裸鼠背部皮下,SC236处理组按3mg/（kg·d）剂量于接种SCC-7901细胞10min后,由尾静脉注射,隔日1次。各组6周后处死动物,观察皮下移植瘤的生长情况。并用Western blot法检测各组细胞VEGF及MMP-2蛋白的表达。结果：体外侵袭实验、促内皮细胞体外迁移实验结果显示,与对照组相比,转染组和SC236处理组迁移的肿瘤细胞和内皮细胞均减少（P〈0.01）;裸鼠皮下移植抑制实验结果显示,转染组和SC236处理组荷瘤鼠移植瘤的生长受到抑制;Western blot结果显示,转染组和SC236处理组细胞VEGF及MMP-2蛋白的表达下降。结论：反义COX-2基因能抑制SCG-7901细胞的转移能力,其机制可能与其抑制肿瘤的血管生成、减少MMP-2的表达有关。     

Enhanced anti-proliferative activity of the combination of tamoxifen plus HER-2-neu antibody

HER-2/neu overexpression has been associated with poor prognosis in human breast cancer. Many of these cancers are also ER-positive. A logical therapeutic approach for patients who are ER-positive and overexpress HER-2/neu may be to block both the ER and the HER-2/neu pathways. In our study, we used both the MTT tetrazolium dye assay and ³H-thymidine incorporation to measure the effects of the anti-estrogen Tamoxifen or the 4D5 anti-HER-2/neu antibody alone or in combination on the growth of BT474 human breast cancer cells which express ER and overexpress HER-2/neu. We found an enhanced inhibitory effect on cell proliferation with the combination of Tamoxifen and the antibody compared to that seen by either agent alone. This simultaneous interruption of both the ER and the HER-2/neu pathways may be relevant in the clinical treatment of patients who are both ER-positive and overexpress HER-2/neu.     

Monoclonal antibody to HER-2/neu receptor enhances radiosensitivity of esophageal cancer cell lines expressing HER-2/neu oncoprotein

PURPOSE: The role of HER-2/neu in the response of esophageal cancer to radiation is not well known. The purpose of this study was to evaluate the effect of an anti-HER-2/neu antibody trastuzumab on the proliferation, cell cycle distribution, and radiosensitivity of esophageal cancer cell lines. EXPERIMENTAL DESIGN: Expression of HER-2/neu protein by four esophageal squamous cancer cell lines (KE4, TE8, TE9, and TE10) and an esophageal adenocarcinoma cell line (SKGT4) was assessed using immunohistochemical (IHC) analysis and flow cytometry. We also evaluated HER-2/neu oncogene expression by fluorescence in situ hybridization. As a control for HER-2/neu protein expression and gene amplification, breast cancer cell lines (MCF7, MDA MB175VII, and SKBR3) were also examined. The cytotoxity of trastuzumab (0.1-200 microg/mL) was estimated by the MTT assay, and the cell cycle distribution was determined by flow cytometry. The effect of 10 microg/mL trastuzumab combined with radiation was assessed by a clonogenic assay. RESULTS: Flow cytometry and IHC revealed that two esophageal cancer cell lines (TE9 and SKGT4) showed HER-2/neu expression (IHC 1+ and mean fluorescence intensity of 11-20), while the other esophageal cancer cell lines were negative for HER-2/neu expression. Although trastuzumab alone had no effect on the esophageal cancer cell lines, the combination of 10 microg/mL trastuzumab with radiation showed a synergistic effect on the HER-2/neu expressing cell lines. CONCLUSIONS: This study suggested that trastuzumab plus irradiation may be effective for the treatment of esophageal cancers, including adenocarcinoma and squamous cell cancer with HER-2/neu expression.     

Acquired antiestrogen resistance in MCF-7 human breast cancer sublines is not accomplished by altered expression of receptors in the ErbB-family

Development of acquired resistance against antiestrogen treatment is a serious problem in human breast cancer, and knowledge of alterations resulting in resistance is important for selection of further treatment. To mimic the clinical situation we have established a series of MCF-7 human breast cancer cell lines by long term treatment with the antiestrogens tamoxifen, ICI 164,384, and ICI 182,780. Common for these cell lines is a decreased expression of the estrogen receptor (ER). In human breast cancer, lack of response to endocrine therapy is often associated with decreased expression of the estrogen receptor and increased expression of epidermal growth factor receptor (EGFR) and/or HER-2/neu (ErbB-2). Our antiestrogen resistant cell lines did not express altered levels of EGFR, HER-2/neu, ErbB-3, or ErbB-4. Estrogen and antiestrogen regulation of HER-2/neu expression was essentially similar in parent and resistant MCF-7 cells. Treatment with antibodies to HER-2/neu (Herceptin^TM) did not affect growth of MCF-7 cells or resistant cells, indicating that in this in vitro model system, acquired antiestrogen resistance does not emerge from activation of the HER-2/neu signaling pathway. In MCF-7 cells transfected with HER-2/neu and/or ErbB-3, overexpression alone did not result in resistance. However, addition of heregulinl-1 abolished the inhibitory activity of ICI 182,780 on both vector and HER-2/neu/ErbB-3 transfected MCF-7 cells, demonstrating that activation of the HER-2/neu receptor signaling pathway can override the growth inhibitory effect of ICI 182,780.     

Treatment of HER-2/neu overexpressing breast cancer xenograft models with trastuzumab (Herceptin) and gefitinib (ZD1839): drug combination effects on tumor growth, HER-2/neu and epidermal growth factor receptor expression, and viable hypoxic cell fraction.

PURPOSE: The purpose of this research was to assess the effects of single agent and combination treatment with trastuzumab and gefitinib on tumor growth and tumor microenvironment in two HER-2/neu overexpressing breast xenograft models, MDA-MB-435/LCC6(HER-2) (LCC6(HER-2); estrogen receptor negative) and MCF-7(HER-2) (estrogen receptor positive). EXPERIMENTAL DESIGN: LCC6(HER-2) and MCF-7(HER-2) cells, both in tissue culture and xenografts grown in SCID-Rag 2M mice, were treated with trastuzumab and gefitinib, alone or in combination. The rate of tumor growth was determined. In addition, tumor HER-2/neu and epidermal growth factor receptor expression, cell viability, cell cycle distribution, and proportion of viable hypoxic cells were determined by flow cytometric analyses of single tumor cell suspensions. RESULTS: Both tumor models were very sensitive to trastuzumab and moderately sensitive to gefitinib in vivo. The combination resulted in therapeutic effects, as judged by inhibition of tumor growth, which was greater (albeit not statistically significant) than that observed with trastuzumab administered as a single agent. Trastuzumab was effective in down-regulating HER-2/neu, and gefitinib mediated a reduction in epidermal growth factor receptor expression on tumor cells. In LCC6(HER-2) tumors, trastuzumab significantly reduced tumor cell viability, which was not improved by the addition of gefitinib. Gefitinib dramatically reduced the proportion of viable hypoxic cells in LCC6(HER-2) and MCF-7(HER-2) tumors. This effect was abrogated by the addition of trastuzumab. CONCLUSIONS: Although in vivo efficacy studies in two HER-2/neu overexpressing breast xenograft models showed that the combination of trastuzumab and gefitinib was effective, analyses of various cellular parameters failed to reveal beneficial effects and argue that this drug combination may not be favorable.     

Inhibitory effects of the combination of HER-2 antisense oligonucleotide and chemotherapeutic agents used for the treatment of human breast cancer.

Poor response to chemotherapy in patients with breast cancer is often associated with overexpression of HER-2/neu. Interference with HER-2 mRNA translation by means of antisense oligonucleotides might improve the efficacy of chemotherapy. To test this hypothesis, eight breast cancer cell lines and a normal human fibroblast cell line were examined for their level of HER-2 expression, their sensitivity to phosphorothioate antisense oligonucleotides (AS HER-2 ODN), and to various chemotherapeutic agents, and the combination of the two. No correlation was found between the intrinsic HER-2 level and either the sensitivity to a particular chemotherapeutic agent alone, or the amount of growth inhibition observed with a specific AS HER-2 ODN concentration. Although sequence specificity and extent of AS HER-2 ODN inhibition of HER-2 synthesis were somewhat higher in the HER-2 overexpressing MDA-MB-453 and SK-BR-3 cells, we found that antisense treatment significantly sensitized all of the breast cancer cells, even MDA-MB-231 and MDA-MB-435 cells, with approximately basal levels of HER-2, to various chemotherapeutic agents. In addition, the combination of AS HER-2 ODN and taxol was shown to synergistically induce apoptosis in MDA-MB-435. These results demonstrate that overexpression of HER-2 would not be a prerequisite for the effective use of AS HER-2 ODN as a combination treatment modality for breast cancer and suggest that the use of AS HER-2 ODN, as part of a combination treatment modality, need not be limited to breast tumors that display elevated levels of HER-2.     

Vaccination with human HER-2/neu (435-443) CTL peptide induces effective antitumor immunity against HER-2/neu-expressing tumor cells in vivo

HER-2/neu is a self-antigen expressed by tumors and nonmalignant epithelial tissues. The possibility of self-tolerance to HER-2/neu-derived epitopes has raised questions concerning their utility in antitumor immunotherapy. Altered HER-2/neu peptide ligands capable of eliciting enhanced immunity to tumor-associated HER-2/neu epitopes may circumvent this problem. The human CTL peptide HER-2/neu (435-443) [hHER-2(9(435))] represents a xenogeneic altered peptide ligand of its mouse homologue, differing by one amino acid residue at position 4. In contrast to mHER-2(9(435)), vaccination of HLA-A*0201 transgenic (HHD) mice with hHER-2(9(435)) significantly increased the frequency of mHER-2(9(435))-specific CTL and also induced strong protective and therapeutic immunity against the transplantable ALC tumor cell line transfected to coexpress HLA-A*0201 and hHER-2/neu or rHER-2/neu. Similar results were also obtained with wild-type C57BL/6 mice inoculated with HER-2/neu transfectants of ALC. Adoptive transfer of CD8(+) CTL from mice immunized with hHER-2(9(435)) efficiently protected naive syngeneic mice inoculated with ALC tumors. In conclusion, our results show that HER-2(9(435)) serves as a tumor rejection molecule. They also propose a novel approach for generating enhanced immunity against a self-HER-2/neu CTL epitope by vaccinating with xenogeneic altered peptide ligands and provide useful insights for the design of improved peptide-based vaccines for the treatment of patients with HER-2/neu-overexpressing tumors.     

SUCI02选择性抑制HER-2/neu受体酪氨酸激酶磷酸化及其对HER-2/neu过表达乳腺癌细胞生长的影响

背景与目的：HER-2／neu受体过度表达与肿瘤的发生发展、对化疗的敏感性以及患者预后有关;我们通过大量筛选,发现SUCI02[N-(4-乙氧苯基)-2-羟基酸胺]能抑制HER2／neu受体酪氨酸激酶磷酸化。本研究拟探讨SUCI02对HER-2／nell过度表达的肿瘤细胞生长的影响。方法：用免疫沉淀、免疫印迹法检测：HER-2／neu受体酪氨酸激酶磷酸化、酪氨酸激酶蛋白水平的变化;MTT法检测SUCI02对乳腺癌细胞的抑制作用。结果：SUCI02能抑制HER-2／neu受体的自身磷酸化,在乳腺癌MDA—MB．453m1细胞中,SUCI02对HER-2／neu受体自身磷酸化的IC50为4．34μg／ml,对HER-2／neu的表达没有任何影响。在用SUCI02处理MDA-MB-453ml细胞30min后,用培养液洗掉药物,继续培养不同时间,结果可见洗掉药物后30min,SUCI02对HER-2／neu受体磷酸化的抑制就开始恢复。SUCI02处理MDA-MB-453ml细胞后其下游靶分子MAPK和AKT激活明显受抑制,呈现剂量依赖性。SUCI02对EGFR受体酪氨酸磷酸化在最高剂量用到40μg／ml下没有明显的抑制作用。应用MTT法检测了SUCI02对过度表达HER-2／neu的MDA-MB-453ml细胞的生长抑制作用,同时应用过表达EGFR的乳腺癌MDA—MB-468细胞作为对照,结果可见SUCI02对HER-2／neu过表达的肿瘤细胞相对于过表达EGFR的肿瘤细胞有更明显的抑制作用。结论：SUCI02选择性抑制HER-2／neu受体酪氨酸激酶磷酸化,阻断其下游信号途径,对过度表达HER-2／neu的肿瘤细胞具有更强的生长抑制作用。