Inhibition of the mTOR/S6K signal is necessary to enhance fluorouracil-induced apoptosis in gastric cancer cells with HER2 amplification

The purpose of this study was to explore the effect of trastuzumab in enhancing the activity of chemotherapeutic agents and the molecular basis of this effect. Two gastric cancer cell types with HER2 amplification, one sensitive (NCI?N87) and one insensitive (MKN-7) to trastuzumab, were tested for the effects of trastuzumab on cell growth and cell signaling using MTS assay and western blotting, respectively. Interaction between trastuzumab and chemotherapeutic agents (fluorouracil, doxorubicin, cisplatin and paclitaxel) was evaluated by the combination index (CI). Fluorouracil-induced apoptosis was evaluated using western blot for poly (ADP-ribose) polymerase (PARP). Trastuzumab decreased phosphorylation of S6K, showed synergistic effect with fluorouracil or doxorubicin, and increased fluorouracil-induced apoptosis in NCI-N87 cells, but not in MKN-7 cells. While the mTOR inhibitor everolimus enhanced fluorouracil-induced apoptosis in both HER2-amplified cell lines, this was not the case in the gastric cancer cell lines without HER2 amplification. Consistently, while the EGFR/HER2 inhibitor Cl-387,785 inhibited cell growth of MKN-7, this growth inhibition did not accompany decrease in phosphorylation of S6K, and the compound did not enhance fluorouracil-induced apoptosis. In summary, inhibition of the mTOR/S6K signal may be a key molecular event in enhancing fluorouracil-induced apoptosis specifically in gastric cancer cells with HER2 amplification. mTOR inhibitors may therefore be attractive alternative drugs in gastric cancers with HER2 amplification regardless of their sensitivity to trastuzumab.     

曲妥珠单抗联合氟尿嘧啶或顺铂治疗胃癌的实验研究

目的：探讨曲妥珠单抗（Herceptin,HCP）联合氟尿嘧啶（5-FU）或顺铂（PDD）治疗胃癌的效果及机制。方法：采用流式细胞检查确定胃癌细胞株的HER-2/neu（HER2）表达情况,并测定药物对细胞周期的影响;以MTT法评价药物的细胞毒性作用;以Westernblot法分析药物对HER2-PI3K-AKT信号转导的影响;以RT-PCR分析药物对靶蛋白酶mRNA的影响。结果：HCP单抗可增强化疗药对HER2阳性细胞的毒性作用。先予5-FU后予HCP单抗、先HCP单抗和PDD联合再序贯使用HCP单抗的方案效果最佳,但先予HCP单抗再和5-FU联合可拮抗5-FU的化疗效果。HCP单抗单用或与化疗药联用均可抑制AKT的磷酸化,HCP单抗与PDD同时使用可抑制NF-κB的核移位;HCP单抗不能增强5-FU对胸苷酸合成酶（TS）mRNA表达的抑制,但可使PDD上调的核苷酸切除修复交叉互补基因（ERCC1）mRNA恢复至正常水平;联合方案对细胞周期的改变影响明显。结论：HCP单抗更适于与PDD联合用于HER2阳性胃癌的治疗,HCP单抗与PDD同时使用再序贯使用HCP单抗的给药方法可能是最佳联合模式;而HCP单抗与5-FU联合则要注意正确的用药次序,以免减弱5-FU的化疗效果。     

HER-2/neu overexpression is rare in hepatocellular carcinoma and not predictive of anti-HER-2/neu regulation of cell growth and chemosensitivity

BACKGROUND: The overexpression of HER-2/neu oncogene has been implicated in the development and modulation of many types of cancer. However, whether HER-2/neu overexpression plays a similar role in hepatocellular carcinoma (HCC) has not been determined. METHODS: Tissue specimens from 36 HCC patients who had been enrolled in 3 separate prospective clinical trials of systemic chemotherapy were studied by immunohistochemical staining. A polyclonal antibody (A0485; DAKO, Copenhagen, Denmark) against HER-2/neu and a horseradish peroxidase-based visualization system (Envision+, DAKO) was used. Scoring criteria was in accordance with the manufacturer's guidelines. Twelve HCC cell lines were examined for HER-2/neu overexpression by Western blotting. Single-agent growth regulatory activity of the anti-HER-2/neu antibody, trastuzumab (Herceptin; Genentech, South San Francisco, CA), and its combinative cytotoxicity with chemotherapeutic agents (doxorubicin, gemcitabine, cisplatin, irinotecan) were determined by a tetrazolium-based colorimetric assay (MTT test). RESULTS: All but one of the HCC tumor tissues were negative for HER-2/neu expression. The only patient with positive HER-2/neu expression was a 57-year-old male patient who achieved stabilization of disease for 2 months after chemotherapy. Eight of the 35 patients with negative HER-2/neu expression had had partial remission after chemotherapy (P = 0.78). Only one (Tong cells) of the 12 HCC cell lines had a significant level of HER-2/neu expression. However, trastuzumab up to 10 microg/mL had no discernible growth inhibitory or chemosensitizing effect on Tong cells or any other cell lines. CONCLUSIONS: HER-2/neu overexpression is rare in human HCC tissues, and anti-HER-2/neu regulation appears to play little role in the treatment of this tumor.     

Antitumor activity of trastuzumab in combination with chemotherapy in human gastric cancer xenograft models

Purpose

To clarify the antitumor activity of trastuzumab and its potential as an effective treatment for gastric cancer patients.

Methods

Levels of HER2 expression in tumor tissues of gastric cancer cell lines were examined using immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and mRNA quantification. Efficacy of trastuzumab was examined as a single agent or in combination with chemotherapeutic agents widely used clinically for gastric cancers in HER2-overexpressing human gastric cancer xenograft models.

Results

Two of nine human gastric cancer xenograft models, NCI-N87 and 4-1ST, showed overexpression of HER2 mRNA and protein by IHC (HercepTest^®) and HER2 gene amplification by FISH (Pathvysion^®). HER2 protein showed potent staining in peripheral membranes, similar to the staining pattern of breast cancer. FISH scores were also comparable to those of breast cancer models. Trastuzumab as a single agent inhibited the tumor growth in both of the HER2-overexpressing models but not in the HER2-negative models, GXF97 and MKN-45. In any combination with capecitabine, cisplatin, irinotecan, docetaxel, or paclitaxel, trastuzumab showed more potent antitumor activity than the anticancer agents alone. A three-drug combination of capecitabine, cisplatin, and trastuzumab showed remarkable tumor growth inhibition. In NCI-N87 in vitro, trastuzumab showed direct antiproliferative activity according to cell count or crystal violet dying, and showed indirect antitumor activity such as antibody-dependent cellular cytotoxicity.

Conclusion

The antitumor activity of trastuzumab observed in human gastric cancer models warrants consideration of its use in clinical treatment regimens for human gastric cancer as a single agent or a combination drug with various chemotherapeutic agents.     

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.     

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.     

阿帕替尼联合曲妥珠单抗对胃癌细胞的协同增敏作用

目的观察阿帕替尼联合曲妥珠单抗杀伤胃癌NCI-N87细胞的协同增敏作用并探讨可能作用机制。方法CCK-8法检测空白对照组、曲妥珠单抗组(0.1、1、10μg/ml)、阿帕替尼组(1μmol/L)及曲妥珠单抗(0.1、1、10μg/ml)+阿帕替尼(1μmol/L)组对NCI-N87细胞的增殖抑制作用,流式细胞术检测NCI-N87细胞凋亡,Western blotting检测HER-2、VEGFR2、Bax、Bcl-2蛋白表达。结果CCK-8检测提示曲妥珠单抗、阿帕替尼能够抑制NCI-N87细胞增殖,在一定浓度范围内作用呈浓度依赖性和时间依赖性(P<0.01);q值计算提示曲妥珠单抗与阿帕替尼具有协同抑制NCI-N87细胞增殖的作用。流式细胞术检测显示联合组NCI-N87胃癌细胞凋亡较单药组明显升高(P<0.05),其中空白对照组、阿帕替尼组(1μmol/L)、曲妥珠单抗(0.1μg/ml)组及曲妥珠单抗(0.1μg/ml)+阿帕替尼(1μmol/L)组的凋亡率分别为(3.0±1.28)%、(5.8±1.63)%、(8.0±3.92)%和(21.6±6.85)%。曲妥珠单抗+阿帕替尼组与空白对照组、曲妥珠单抗及阿帕替尼单药组比较,HER-2蛋白表达显著下调(P<0.05);曲妥珠单抗+阿帕替尼组与空白对照组比较,Bcl-2蛋白表达、Bcl-2/Bax比值明显降低(P<0.01)。结论阿帕替尼联合曲妥珠单抗可能通过下调HER-2蛋白及调控凋亡相关蛋白Bcl-2、Bax的表达,协同抑制NCI-N87细胞增殖和促进细胞凋亡。     

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.     

Change in HER-2/neu Status from Negative to Positive following Treatment in Breast Cancer: A Case Report

INTRODUCTION: Approximately 25-30% of breast cancers are assumed to be HER-2/neu positive. It is well known that HER-2/neu-positive cancers after treatment with trastuzumab can become HER-2/neu negative. Change in HER-2/neu status from negative to positive following treatment has not been well studied. We describe a patient with inflammatory breast cancer who was initially HER-2/neu negative but became positive after treatment. A 59-year-old postmenopausal white female saw her surgeon for violaceous discoloration of the left breast for 4 months. The surgeon palpated a mass measuring 6 cm in the patient's left breast. Additionally, there was violaceous discoloration involving two thirds of the breast. Biopsy of the breast mass and skin revealed inflammatory breast cancer. The tumor was estrogen receptor positive, progesterone receptor positive and HER-2/neu negative. The patient was given four cycles of chemotherapy with cyclophosphamide, doxorubicin and docetaxol. She subsequently underwent a mastectomy, excision of the skin over the chest wall and axillary node dissection. Of the axillary lymph nodes, 14/14 were involved. The tumor was still estrogen receptor positive and progesterone receptor positive, but HER-2/neu was 2+ by immunohistochemistry and amplified at 3.3 as detected by fluorescent in situ hybridization. The patient received trastuzumab along with chemotherapy followed by radiation therapy and letrozole. She is currently receiving trastuzumab and letrozole in the adjuvant setting and appears to be doing well. CONCLUSION: A breast cancer which was initially HER-2/neu negative can become positive following treatment. Therefore, re-biopsy may be necessary during the course of treatment of breast cancer to re-assess the HER-2/neu status. This gives the clinician the opportunity to include drugs like trastuzumab and lapatinib in the treatment of patients with a transformation to HER-2/neu-positive cancer.     

Immunotherapy: new options in breast cancer treatment

Immunotherapy is a promising new approach in breast cancer treatment, complementing surgery, chemotherapy, radiation and antihormonal therapy. Primarily, two treatment options are available which are supported by a rapidly growing body of clinical evidence. These are active specific immunotherapy with Theratope and passive immunotherapy targeting the HER-2 receptor with trastuzumab (Herceptin). Trastuzumab has a proven efficacy as monotherapy as well as in combination with chemotherapeutic agents in HER-2-overexpressing metastatic breast cancer. Trastuzumab is generally well tolerated although cardiotoxicity has been observed, especially when in combination with doxorubicin (Adriamycin), where this can be a serious concern. Therefore, less cardiotoxic combinations with docetaxel (Taxotere), vinorelbine (Navelbine) and epirubicin (Pharmorubicin) or cyclophosphamide (Endoxana) have been tested. The combination of trastuzumab with paclitaxel (Taxol) is well approved. The use of trastuzumab in adjuvant and preoperative therapy is currently being examined in controlled trials. After a brief outline of immunotherapy with Theratope and trastuzumab, this article reviews recent and ongoing clinical studies conducted with trastuzumab.     

Anti-Her-2/neu antibody induces apoptosis in Her-2/neu overexpressing breast cancer cells independently from p53 status.

Anti-Her-2/neu antibody is known to induce apoptosis in HER-2/neu overexpressing breast cancer cells. However, exact regulatory mechanisms mediating and controlling this phenomenon are still unknown. In the present study, we have investigated the effect of anti-Her-2/neu antibody on apoptosis of HER-2/neu overexpressing human breast cancer cell lines SK-BR-3, HTB-24, HTB-25, HTB-27, HTB-128, HTB-130 and HTB-131 in relation to p53 genotype and bcl-2 status. SK-BR-3, HTB-24, HTB-128 and HTB-130 cells exhibited mutant p53, whereas wild type p53 was found in HTB-25, HTB-27 and HTB-131 cells. All seven cell lines weakly expressed bcl-2 protein (10-20%). Anti-Her-2/neu antibody, irrespective of p53 and bcl-2 status, induced apoptosis in all 7 cell lines dose- and time-dependently and correlated with Her-2/neu overexpression. In addition, incubation of cell lines with anti-Her-2/neu antibody did not alter p53 or bcl-2 expression. Anti-HER-2/neu antibody did not induce apoptosis in HER-2/neu negative HBL-100 and HTB-132 cell lines. Our results indicate that within the panel of tested breast cancer cell lines, anti-Her-2/neu antibody-induced apoptosis was independent from the presence of intact p53.     

An immunotherapeutic approach to treatment of breast cancer: focus on trastuzumab plus paclitaxel

Recent emphasis has focused on the development of an immunotherapeutic approach toward the treatment of breast cancer. In particular, evaluation of antibodies and vaccines are active areas of research. The monoclonal antibody trastuzumab (H), directed against the HER-2/neu protein, has resulted in inhibition of tumor growth in both preclinical and clinical studies. This effect can be increased when used in combination with several chemotherapeutic agents. A randomized trial of chemotherapy alone versus chemotherapy plus H in untreated metastatic breast cancer patients found prolonged survival in the combination therapy arm. Cardiac toxicity was increased with doxorubicin and cyclophosphamide plus H but not for paclitaxel (T) plus H. Several trials of dose-dense weekly T have found minimal toxicity and significant clinical benefit. These findings prompted the initiation of a trial to evaluate weekly 1-h T plus weekly H. Preliminary data from this ongoing study demonstrate few side effects and a response rate of 64% (95%CI 42-76%). The optimal role of H in the treatment of breast cancer has not yet been defined. Additional evaluation in the metastatic and adjuvant settings is planned.     

Tyrosine kinase inhibitor emodin suppresses growth of HER-2/neu-overexpressing breast cancer cells in athymic mice and sensitizes these cells to the inhibitory effect of paclitaxel.

Overexpression of the HER-2/neu proto-oncogene, which encodes the tyrosine kinase receptor p185neu, has been observed in tumors from breast cancer patients. We demonstrated previously that emodin, a tyrosine kinase inhibitor, suppresses tyrosine kinase activity in HER-2/neu-overexpressing breast cancer cells and preferentially represses transformation phenotypes of these cells in vitro. In the present study, we examined whether emodin can inhibit the growth of HER-2/neu-overexpressing tumors in mice and whether emodin can sensitize these tumors to paclitaxel, a commonly used chemotherapeutic agent for breast cancer patients. We found that emodin significantly inhibited tumor growth and prolonged survival in mice bearing HER-2/neu-overexpressing human breast cancer cells. Furthermore, the combination of emodin and paclitaxel synergistically inhibited the anchorage-dependent and -independent growth of HER-2/neu-overexpressing breast cancer cells in vitro and synergistically inhibited tumor growth and prolonged survival in athymic mice bearing s.c. xenografts of human tumor cells expressing high levels of p185neu. Both immunohistochemical staining and Western blot analysis showed that emodin decreases tyrosine phosphorylation of HER-2/neu in tumor tissue. Taken together, our results suggest that the tyrosine kinase activity of HER-2/neu is required for tumor growth and chemoresistance and that tyrosine kinase inhibitors such as emodin can inhibit the growth of HER-2/neu-overexpressing tumors in mice and also sensitize these tumors to paclitaxel. The results may have important implications in chemotherapy for HER-2/neu-overexpressing breast tumors.     

Suppression of tumor growth in human gastric cancer with HER2 overexpression by an anti-HER2 antibody in a murine model

New modalities are necessary for the treatment of patients with unresectable gastric cancer. The aim of this study was to investigate whether or not anti-HER2 antibody could suppress the growth of human gastric cancer cells with HER2 overexpression in vitro and in vivo. Four human gastric cancer cell lines, NCI-N87, MKN-45P, Kato-III, and MKN-1, were used in this study. The suppression of cell proliferation in vitro and of subcutaneous tumor growth in a nude mouse model after treatment with trastuzumab was examined. The expression of HER2 protein was investigated by Western blot analysis. The effect of trastuzumab on the survival rate of nude mice with peritoneal dissemination was examined. Trastuzumab significantly reduced proliferative activity in NCI-N87, a HER2-overexpressing human gastric cancer cell line, in vitro. In the nude mouse model with transplanted subcutaneous tumor, trastuzumab significantly suppressed the tumor growth of NCI-N87 cells, and then HER2 expression was reduced. Trastuzumab improved the survival rate of mice with peritoneal dissemination of MKN-45P cells. Trastuzumab therapy is a potential candidate for a novel treatment of HER2-overexpressing gastric cancer.     

Feasibility of tailored, selective and effective anticancer chemotherapy by direct injection of docetaxel-loaded immunoliposomes into Her2/neu positive gastric tumor xenografts

We assessed the effects of direct injection of docetaxel-loaded immuno-(trastuzumab)-liposomes (IDL) on a xenograft mouse tumor model to determine potential clinical applications of intratumoral tailored chemotherapy against Her2/neu-overexpressing gastric cancer. The NCI-N87 Her2/neu overexpressing gastric cancer cell line xenograft mouse model was treated with IDL or docetaxel-loaded liposomes (DL). The ratio of the tumor volume of the treatment:control was determined. In addition, docetaxel pharmacokinetics in tumors were measured using high-performance liquid chromatography, and the cell viability and cell cycle distribution of Her2/neu positive cells were determined by flow cytometric analysis. The IDL group showed a significantly higher distribution of docetaxel in the N87 xenograft tumor tissues and superior antitumor efficacy compared to crude administration of docetaxel and/or trastuzumab and DL. The number of viable Her2/neu positive cells decreased following treatment with either free trastuzumab or IDL. On day 7 after treatment, a decrease in the G0/G1 phase of the cell cycle was observed in the DL and IDL groups compared to the control group. No local adverse effects were observed. These results suggest that intratumoral administration of IDL maintains a high concentration of docetaxel within the tumor leading to a safe and effective regional cancer therapeutic strategy. In addition to the inherent cytotoxic effect of trastuzumab, conjugation of trastuzumab to a liposome further enhanced the retention of docetaxel within the tumors. These data suggest that immuno-liposome mediated delivery of drugs is a promising new therapeutic option for patients with advanced gastric cancer that overexpress Her2/neu.     

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.     

E1A-mediated paclitaxel sensitization in HER-2/neu-overexpressing ovarian cancer SKOV3.ip1 through apoptosis involving the caspase-3 pathway.

HER-2/neu-overexpressing breast cancer cells are more resistant to the chemotherapeutic agent paclitaxel (Taxol) than low-HER-2/neu-expressing breast cancer cells, and the adenoviral type 5 EIA can down-regulate HER-2/neu overexpression. Therefore, in this study, we asked (a) whether EIA might sensitize response to paclitaxel in human HER-2/neu-overexpressing ovarian cancer cells, and, if so, what is the mechanism responsible; and (b) whether this enhanced chemosensitivity would translate into a therapeutic effect in an ovarian cancer xenograft model. Consequently, we demonstrated that: (a) adenovirus type 5 E1A could enhance the sensitivity of paclitaxel in paclitaxel-resistant HER-2/neu-overexpressing human ovarian cancer cells in vitro by inducing apoptosis, (b) this induction was heavily dependent on activation of the caspase-3 pathway, and (c) nude mice bearing i.p. HER-2/neu-overexpressing human ovarian cancer cells and treated with both paclitaxel and E1A gene therapy survived significantly longer than did mice treated only with paclitaxel or E1A gene therapy. Thus, we concluded that the E1A gene enhanced both the in vitro and in vivo sensitivity of paclitaxel in paclitaxel-resistant HER-2/ neu-overexpressing ovarian cancer SKOV3.ipl cells. Because a Phase I clinical trial using E1A gene targeted to HER-2/neu down-regulation has recently been completed, the current study also provided a scientific basis to further develop a novel therapy that combines paclitaxel and E1A gene therapy and its testing in a Phase II trial.     

Synergistic antitumor effect of the anti-ErbB2 antibodies trastuzumab and H2-18 on trastuzumab-resistant gastric cancer cells

Trastuzumab resistance is a severe problem in the treatment of ErbB2-amplified cancer. Although trastuzumab plus pertuzumab is able to partly overcome trastuzumab resistance in ErbB2-overexpressing cancer, its antitumor efficacy remains limited. The present study investigated the antitumor activity of the combination of trastuzumab with H2-18, which is an antibody targetinsg ErbB2 domain I. Cell proliferation and inhibition experiments indicated that H2-18 and trastuzumab synergistically inhibited the proliferation of both the trastuzumab-sensitive gastric cancer cell line, NCI-N87 and the trastuzumab-resistant gastric cancer cell line, NCI-N87-TraRT. Furthermore, H2-18 plus trastuzumab inhibited the growth of NCI-N87-TraRT cells more effectively than trastuzumab plus pertuzumab, both in vitro and in vivo. Compared with trastuzumab plus pertuzumab, H2-18 plus trastuzumab had a potent ability to inhibit NCI-N87-TraRT cells to form colonies. Notably, H2-18 plus trastuzumab was more effective in inducing cell death than trastuzumab plus pertuzumab. The in vivo studies demonstrated that H2-18 plus trastuzumab effectively inhibited the growth of both NCI-N87 and NCI-N87-TraRT xenograft tumors. Further experiments revealed that in NCI-N87-TraRT cells, H2-18 plus trastuzumab was comparable to trastuzumab plus pertuzumab in the inhibition of phosphorylated (p-)HER3, p-AKT and p-ERK. However, compared with trastuzumab plus pertuzumab, H2-18 plus trastuzumab effectively activated ROS production and the phosphorylation of JNK and c-jun in NCI-N87-TraRT cells. Therefore, the superior antitumor efficacy of H2-18 plus trastuzumab over trastuzumab plus pertuzumab may be mainly attributable to the potent cell death-inducing activity. In addition, the in vitro and in vivo antitumor effect of the combination of H2-18, trastuzumab and pertuzumab were further investigated. The results revealed that H2-18 plus trastuzumab plus pertuzumab exhibited a maximal antitumor effect among all the anti-ErbB2 monoclonal antibody combinations tested. In summary, H2-18 plus trastuzumab may have potential as an effective strategy to overcome the resistance to trastuzumab in ErbB2-amplified gastric cancer cell lines.     

Controlled internalization of Her-2/ neu receptors by cross-linking for targeted delivery

Receptor mediated internalization is a crucial step for targeted intracellular delivery of therapeutic and imaging agents. It was recently demonstrated that trastuzumab, an FDA approved humanized monoclonal antibody against Her-2/ neu tyrosine kinase receptor, did not induce endocytosis of the internalization resistant Her-2/ neu receptor. Here we report that accelerated internalization of trastuzumab can be induced by cross-linking the cell membrane bound antibody-receptor complex with an avidin/streptavidin-biotin system. We demonstrated that internalization was achieved both in vitro and in vivo in Her-2/ neu expressing human breast cancer cell lines (BT-474, SK-BR-3 and AU-565) and that repetitive labeling cycles further amplified the loading of cargo molecules within the targeted cells. No trastuzumab binding and internalization was observed in Her-2/ neu negative MDA-MB-231 cells, whereas weak membrane binding and negligible internalization were detected in MCF-7 cells with low expression level of Her-2/ neu receptor. The method was used to noninvasively image Her-2/ neu receptors in isolated cells and in a preclinical breast cancer model with MRI. The controlled internalization of Her-2/ neu receptors can potentially enhance intracellular delivery of drugs and imaging probes, and improve imaging sensitivity and selectivity as well as therapeutic efficacy, through antibody-directed binding and internalization using a pretargeting approach.