Nuclear HER4 mediates acquired resistance to trastuzumab and is associated with poor outcome in HER2 positive breast cancer

The role of HER4 in breast cancer is controversial and its role in relation to trastuzumab resistance remains unclear. We showed that trastuzumab treatment and its acquired resistance induced HER4 upregulation, cleavage and nuclear translocation. However, knockdown of HER4 by specific siRNAs increased trastuzumab sensitivity and reversed its resistance in HER2 positive breast cancer cells. Preventing HER4 cleavage by a γ-secretase inhibitor and inhibiting HER4 tyrosine kinase activity by neratinib decreased trastuzumab-induced HER4 nuclear translocation and enhanced trastuzumab response. There was also increased nuclear HER4 staining in the tumours from BT474 xenograft mice and human patients treated with trastuzumab. Furthermore, nuclear HER4 predicted poor clinical response to trastuzumab monotherapy in patients undergoing a window study and was shown to be an independent poor prognostic factor in HER2 positive breast cancer. Our data suggest that HER4 plays a key role in relation to trastuzumab resistance in HER2 positive breast cancer. Therefore, our study provides novel findings that HER4 activation, cleavage and nuclear translocation influence trastuzumab sensitivity and resistance in HER2 positive breast cancer. Nuclear HER4 could be a potential prognostic and predictive biomarker and understanding the role of HER4 may provide strategies to overcome trastuzumab resistance in HER2 positive breast cancer.     

Calpain-1 expression is associated with relapse-free survival in breast cancer patients treated with trastuzumab following adjuvant chemotherapy

The calpain family, and their endogenous inhibitor calpastatin, has been implicated in cancer progression, and recent in vitro data have indicated a role in trastuzumab resistance. The aims of our study were to examine expression levels of calpastatin, calpain-1 and calpain-2 in breast tumours from patients treated with trastuzumab following adjuvant chemotherapy to determine their potential as biomarkers to predict therapeutic response. The expression of calpastatin, calpain-1 and calpain-2 was determined, using immunohistochemistry (IHC), in tumours from a series of 93 patients with primary breast cancer treated with surgery and adjuvant chemotherapy with or without trastuzumab followed by trastuzumab to complete 1 year of therapy. IHC was performed using tissue microarrays constructed from cores taken from intratumour and peripheral tumour areas. Expression was correlated with clinicopathologic variables and patient outcome. Calpastatin expression was correlated with Nottingham prognostic index (p = 0.003) and lymph node status (p = 0.007). Trastuzumab resistance was defined as disease relapse during therapy. Calpain-1 expression is associated with relapse-free survival (p = 0.001) and remained significant in multivariate analysis accounting for confounding pathological and treatment variables (hazard ratio 4.60, 95% confidence interval 1.05-20.25; p = 0.043). Calpain-1 may be a useful biomarker to predict relapse-free survival in breast cancer patients treated with adjuvant trastuzumab and chemotherapy. A larger verification study is warranted.     

ADAM10 mediates trastuzumab resistance and is correlated with survival in HER2 positive breast cancer

Trastuzumab prolongs survival in HER2 positive breast cancer patients. However, resistance remains a challenge. We have previously shown that ADAM17 plays a key role in maintaining HER2 phosphorylation during trastuzumab treatment. Beside ADAM17, ADAM10 is the other well characterized ADAM protease responsible for HER ligand shedding. Therefore, we studied the role of ADAM10 in relation to trastuzumab treatment and resistance in HER2 positive breast cancer. ADAM10 expression was assessed in HER2 positive breast cancer cell lines and xenograft mice treated with trastuzumab. Trastuzumab treatment increased ADAM10 levels in HER2 positive breast cancer cells (p≤0.001 in BT474; p≤0.01 in SKBR3) and in vivo (p≤0.0001) compared to control, correlating with a decrease in PKB phosphorylation. ADAM10 inhibition or knockdown enhanced trastuzumab response in naïve and trastuzumab resistant breast cancer cells. Trastuzumab monotherapy upregulated ADAM10 (p≤0.05); and higher pre-treatment ADAM10 levels correlated with decreased clinical response (p≤0.05) at day 21 in HER2 positive breast cancer patients undergoing a trastuzumab treatment window study. Higher ADAM10 levels correlated with poorer relapse-free survival (p≤0.01) in a cohort of HER2 positive breast cancer patients. Our studies implicate a role of ADAM10 in acquired resistance to trastuzumab and establish ADAM10 as a therapeutic target and a potential biomarker for HER2 positive breast cancer patients.     

HER2 loss in HER2‐positive gastric or gastroesophageal cancer after trastuzumab therapy: Implication for further clinical research

Mechanisms of acquired resistance to trastuzumab‐based treatment in gastric cancer are largely unknown. In this study, we analyzed 22 pairs of tumor samples taken at baseline and post‐progression in patients receiving chemotherapy and trastuzumab for advanced HER2‐positive [immunohistochemistry (IHC) 3+ or 2+ with in‐situ hybridization (ISH) amplification] gastric or gastroesophageal cancers. Strict clinical criteria for defining acquired trastuzumab resistance were adopted. Loss of HER2 positivity and loss of HER2 over‐expression were defined as post‐trastuzumab IHC score <3+ and absence of ISH amplification, and IHC “downscoring” from 2+/3+ to 0/1+, respectively. HER2 IHC was always performed, while ISH was missing in 3 post‐progression samples. Patients with initial HER2 IHC score 3+ and 2+ were 14 (64%) and 8 (36%), respectively. Loss of HER2 positivity and HER2 over‐expression was observed in 32 and 32% samples, respectively. The chance of HER2 loss was not associated with any of the baseline clinicopathological variables. The only exception was in patients with initial IHC score 2+ versus 3+, for both endpoints of HER2 positivity (80 vs. 14%; p = 0.008) and HER2 over‐expression (63 vs. 14%; p = 0.025). As already shown in breast cancer, loss of HER2 may be observed also in gastric cancers patients treated with trastuzumab‐based chemotherapy in the clinical practice. This phenomenon may be one of the biological reasons explaining the failure of anti‐HER2 second‐line strategies in initially HER2‐positive disease.     

Neratinib overcomes trastuzumab resistance in HER2 amplified breast cancer

Trastuzumab has been shown to improve the survival outcomes of HER2 positive breast cancer patients. However, a significant proportion of HER2-positive patients are either inherently resistant or develop resistance to trastuzumab. We assessed the effects of neratinib, an irreversible panHER inhibitor, in a panel of 36 breast cancer cell lines. We further assessed its effects with or without trastuzumab in several sensitive and resistant breast cancer cells as well as a BT474 xenograft model. We confirmed that neratinib was significantly more active in HER2-amplified than HER2 non-amplified cell lines. Neratinib decreased the activation of the 4 HER receptors and inhibited downstream pathways. However, HER3 and Akt were reactivated at 24 hours, which was prevented by the combination of trastuzumab and neratinib. Neratinib also decreased pHER2 and pHER3 in acquired trastuzumab resistant cells. Neratinib in combination with trastuzumab had a greater growth inhibitory effect than either drug alone in 4 HER2 positive cell lines. Furthermore, trastuzumab in combination with neratinib was growth inhibitory in SKBR3 and BT474 cells which had acquired resistance to trastuzumab as well as in a BT474 xenograft model. Innately trastuzumab resistant cell lines showed sensitivity to neratinib, but the combination did not enhance response compared to neratinib alone. Levels of HER2 and phospho-HER2 showed a direct correlation with sensitivity to neratinib. Our data indicate that neratinib is an effective anti-HER2 therapy and counteracted both innate and acquired trastuzumab resistance in HER2 positive breast cancer. Our results suggest that combined treatment with trastuzumab and neratinib is likely to be more effective than either treatment alone for both trastuzumab-sensitive breast cancer as well as HER2-positive tumors with acquired resistance to trastuzumab.     

Addition of GM-CSF to trastuzumab stabilises disease in trastuzumab-resistant HER2+ metastatic breast cancer patients

Background:

One of the proposed mechanisms of trastuzumab-induced regression of human epidermal growth factor receptor 2-positive (HER2+) tumours includes facilitation of antibody-dependent cell-mediated cytotoxicity (ADCC). Granulocyte-macrophage colony-stimulating factor (GM-CSF) mediates ADCC. We presented our pilot study of adding GM-CSF to trastuzumab in patients with trastuzumab-resistant HER2+ metastatic breast cancer.

Methods:

Patients with HER2+ metastatic breast cancer that progressed after trastuzumab +/− chemotherapy were continued on trastuzumab 2 mg kg^–1 intravenous weekly and GM-CSF 250 μg m^–2 subcutaneous daily. Patients were assessed for response every 8 weeks. Treatment was continued until disease progression or intolerable toxicity.

Results:

Seventeen patients were evaluable (median age 48 years, range 27–75 years). The median number of metastatic sites was 2 (range 1–3); the most common site was the liver (n=10). The median number of prior regimens for metastatic disease was 2 (range 1–5). No objective disease response was observed, but five patients (29%) had stable disease for a median duration of 15.8 (range 10–53.9) weeks. The most common adverse event was rash at the injection site. No grade 4 or irreversible adverse event was seen.

Conclusion:

The addition of GM-CSF to trastuzumab alone had a modest clinical benefit and acceptable safety profile in heavily pretreated patients with trastuzumab-resistant HER2+ metastatic breast cancer.     

曲妥珠单抗治疗后进展的转移性乳腺癌继续曲妥珠单抗治疗的疗效及安全性分析

目的：评价曲妥珠单抗治疗后进展的转移性乳腺癌患者继续行曲妥珠单抗治疗的疗效及安全性。方法回顾性分析曲妥珠单抗治疗过程中出现疾病进展,继续行曲妥珠单抗治疗,仅更换化疗方案的30例HER2阳性转移性乳腺癌患者的临床资料,并评价疗效及不良反应。结果30例HER2阳性转移性乳腺癌患者,均在复发转移阶段接受过曲妥珠单抗治疗,中位治疗时间6.0个月（95%CI为1.7~10.3个月）;30例患者在出现疾病进展后,均继续进行曲妥珠单抗治疗,仅更换联合的化疗方案。30例患者均可评价疗效,其中部分缓解（PR）7例（23.3%）,疾病稳定（SD）12例（40.0%）,疾病进展（PD）11例（36.7%）,无完全缓解（CR）患者。客观缓解率为23.3%,临床获益率为43.3%。总无进展生存期（PFS）为5.0个月（95%CI为3.0~7.0个月）。有临床获益的13例患者的PFS明显长于17例无临床获益者（9.0个月vs 3.0个月,P﹤0.001）。最常见的不良反应为血液学不良反应,考虑主要与化疗药物相关。结论对于曲妥珠单抗治疗过程中出现疾病进展的患者,继续使用曲妥珠单抗,更换化疗方案有较好的临床获益。     

Beyond trastuzumab: novel therapeutic strategies in HER2-positive metastatic breast cancer

The use of trastuzumab, a monoclonal antibody that targets the human epidermal growth factor receptor 2 (HER2) alteration present in 25 to 30% of breast cancers, has been associated with improved survival outcomes in both the adjuvant and metastatic settings. However, despite the robust clinical efficacy of trastuzumab in HER2-positive metastatic breast cancer (MBC), primary and secondary resistance remains a clinical challenge. Although lapatinib has demonstrated modest activity in this setting, trials reported to date have yet to demonstrate improvements in overall survival with its use. Novel therapeutic strategies to circumvent trastuzumab resistance are warranted, and agents targeting the HER, vascular endothelial growth factor, heat shock protein 90, phosphoinositide 3 kinase/Akt/mammalian target of rapamycin, and insulin-like growth factor-1 receptor pathways represent rational approaches in the management of HER2-positive disease. In this review, early-phase and emerging trial data surrounding the use of these promising agents in HER2-positive MBC will be discussed.     

The HER2 amplicon includes several genes required for the growth and survival of HER2 positive breast cancer cells

About 20% of breast cancers are characterized by amplification and overexpression of the HER2 oncogene. Although significant progress has been achieved for treating such patients with HER2 inhibitor trastuzumab, more than half of the patients respond poorly or become resistant to the treatment. Since the HER2 amplicon at 17q12 contains multiple genes, we have systematically explored the role of the HER2 co-amplified genes in breast cancer cell growth and their relation to trastuzumab resistance. We integrated aCGH data of the HER2 amplicon from 71 HER2 positive breast tumors and 10 cell lines with systematic functional RNA interference analysis of 23 core amplicon genes with several phenotypic endpoints in a panel of trastuzumab responding and non-responding HER2 positive breast cancer cells. Silencing of HER2 caused a greater growth arrest and apoptosis in the responding compared to the non-responding cell lines, indicating that the resistant cells are inherently less dependent on the HER2 pathway. Several other genes in the amplicon also showed a more pronounced effect when silenced; indicating that expression of HER2 co-amplified genes may be needed to sustain the growth of breast cancer cells. Importantly, co-silencing of STARD3, GRB7, PSMD3 and PERLD1 together with HER2 led to an additive inhibition of cell viability as well as induced apoptosis. These studies indicate that breast cancer cells may become addicted to the amplification of several genes that reside in the HER2 amplicon. The simultaneous targeting of these genes may increase the efficacy of the anti-HER2 therapies and possibly also counteract trastuzumab resistance. The observed additive effects seem to culminate to both apoptosis and cell proliferation pathways indicating that these pathways may be interesting targets for combinatorial treatment of HER2+ breast cancers.     

Metformin-induced preferential killing of breast cancer initiating CD44+CD24-/low cells is sufficient to overcome primary resistance to trastuzumab in HER2+ human breast cancer xenografts

Trastuzumab-refractory breast cancer stem cells (CSCs) could also explain the high rate of primary resistance to single-agent trastuzumab in HER2 gene-amplified breast cancer patients. The identification of agents with strong selective toxicity for trastuzumab-resistant breast CSCs may have tremendous relevance for how HER2+ breast cancer patients should be treated. Using the human breast cancer cell line JIMT-1, which was established from the pleural metastasis of a patient who was clinically resistant to trastuzumab ab initio, we examined whether preferential killing of the putative CD44+CD24-/low breast CSC population might be sufficient to overcome primary resistance to trastuzumab in vivo. Because recent studies have shown that the anti-diabetic biguanide metformin can exert antitumor effects by targeted killing of CSC-like cells, we explored whether metformin's ability to preferentially kill breast cancer initiating CD44+CD24-/low cells may have the potential to sensitize JIMT-1 xenograft mouse models to trastuzumab. Upon isolation for breast cancer initiating CD44+CD24-/low cells by employing magnetic activated cell sorting, we observed the kinetics of metformin-induced killing drastically varied among CSC and non-CSC subpopulations. Metformin's cell killing effect increased dramatically by more than 10-fold in CD44+CD24-/low breast CSC cells compared to non-CD44+CD24-/low immunophenotypes. While seven-weeks treatment length with trastuzumab likewise failed to reduce tumor growth of JIMT-1 xenografts, systemic treatment with metformin as single agent resulted in a significant two-fold reduction in tumor volume. When trastuzumab was combined with concurrent metformin, tumor volume decreased sharply by more than four-fold. Given that metformin-induced preferential killing of breast cancer initiating CD44+CD24-/low subpopulations is sufficient to overcome in vivo primary resistance to trastuzumab, the incorporation of metformin into trastuzumab-based regimens may provide a valuable strategy for treatment of HER2+ breast cancer patients.     

Development of Lu‐177‐trastuzumab for radioimmunotherapy of HER2 expressing breast cancer and its feasibility assessment in breast cancer patients

HER2/neu is over expressed in 20–25% of breast cancers. HER2 breast cancers are aggressive and are associated with poor prognosis. The aim of this study was to develop the clinical grade Lu‐177‐trastuzumab and its preliminary evaluation for specific tumor targeting in HER2 positive breast cancer patients. Trastuzumab was conjugated to bifunctional chelator, DOTA, and characterized for integrity and the number of molecules conjugated. Radiolabeling of DOTA‐conjugated trastuzumab was optimized using Lu‐177. Quality control parameters including radiochemical purity, stability, sterility, pyrogenicity and immunoreactivity were assessed. A preliminary pilot study was conducted on breast cancer patients (n = 6 HER2 positive and n = 4 HER2 negative) to evaluate the ability of Lu‐177‐trastuzumab for HER2 specific tumor targeting. The conjugates were efficiently labeled with Lu‐177 with high radiochemical purity (up to 91%) and specific activity (6–13 µCi/µg). Lu‐177‐trastuzumab was stable up to 12 hr post labeling. The radioimmunoassay demonstrated good antigen binding ability and specificity for HER2 receptor protein. The patient studies showed the localization of Lu‐177‐trastuzumab at primary as well as metastatic sites (HER2 positive) in the planar and SPECT/CT images. No tracer uptake was observed in HER2 negative patients that indicated the specificity of Lu‐177‐trastuzumab. The study demonstrated that in‐house developed Lu‐177‐trastuzumab has specific targeting ability for HER2 expressing lesions and may in future become a palliative treatment option in the form of targeted radionuclide therapy for disseminated HER2 positive breast cancer.     

Serum HER2 extracellular domain in metastatic breast cancer patients treated with weekly trastuzumab and paclitaxel: association with HER2 status by immunohistochemistry and fluorescence in situ hybridization and with response rate.

PURPOSE: We explored the relationship between circulating HER2 extracellular domain (ECD) and tissue HER2 status as determined by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). We also examined its predictive value in a cohort of metastatic breast cancer patients treated with weekly trastuzumab and paclitaxel. METHODS: Eligible patients had pre- and post-treatment stored serum specimens and were treated on a previously reported phase II trial. Retrospective analysis evaluated: the association between pretreatment serum HER2 ECD and tissue HER2 status by IHC and FISH; and the association between change in serum HER2 ECD after 12 weeks of therapy and response proportion. RESULTS: Stored serum samples were available for 55/95 (58%) patients. Statistically significant associations were found between HER2 status as assessed by IHC and FISH, and baseline serum HER2 ECD level. Patients whose ECD normalized after 12 weeks of therapy had a higher response proportion compared with patients with persistently high ECD levels (68% versus 15%, P=0.005). A relative decline of over 55% from baseline HER2 ECD predicted response to therapy. CONCLUSION: A statistically significant association was observed between pretreatment serum HER2 ECD and tissue HER2 status as assessed by IHC and FISH. A decrease in serum HER2 ECD level was a significant predictor of response to trastuzumab-based therapy.     

Src,a potential target for overcoming trastuzumab resistance in HER2-positive breast carcinoma

Background:

Src is a non-receptor tyrosine kinase involved in signalling and crosstalk between growth-promoting pathways. We aim to investigate the relationship of active Src in response to trastuzumab of HER2-positive breast carcinomas.

Methods:

We selected 278 HER2-positive breast cancer patients with (n=154) and without (n=124) trastuzumab treatment. We performed immunohistochemistry on paraffin-embedded tissue microarrays of active Src and several proteins involved in the PI3K/Akt/mTOR pathway, PIK3CA mutational analysis and in vitro studies (SKBR3 and BT474 cancer cells). The results were correlated with clinicopathological factors and patients'' outcome.

Results:

Increased pSrc-Y416 was demonstrated in trastuzumab-resistant cells and in 37.8% of tumours that correlated positively with tumour size, necrosis, mitosis, metastasis to the central nervous system, p53 overexpression and MAPK activation but inversely with EGFR and p27. Univariate analyses showed an association of increased active Src with shorter survival in patients at early stage with HER2/hormone receptor-negative tumours treated with trastuzumab.

Conclusions:

Src activation participates in trastuzumab mechanisms of resistance and indicates poor prognosis, mainly in HER2/hormone receptor-negative breast cancer. Therefore, blocking this axis may be beneficial in those patients.     

Pertuzumab in combination with trastuzumab and docetaxel for HER2-positive metastatic breast cancer

Overexpression of HER2 – found in approximately 15–20% of all breast cancers – is a negative prognostic factor. Although trastuzumab significantly improves the prognosis of HER2-positive breast cancer, half of the patients with metastatic breast cancer experience disease progression within 1 year. Pertuzumab is a novel HER2-targeted humanized monoclonal antibody that binds to the dimerization domain of HER2 and acts synergically with trastuzumab in inhibiting tumor progression. The CLEOPATRA trial demonstrated that adding pertuzumab to trastuzumab plus docetaxel significantly prolonged progression-free survival and overall survival without increasing severe adverse events. Conclusively, pertuzumab was approved by the US FDA in June 2012 for use in combination with trastuzumab and docetaxel for the treatment of patients with HER2-positive metastatic breast cancer. Furthermore, various clinical trials to evaluate the efficacy and safety of pertuzumab combined with other cytotoxic agents are ongoing at present. Thus, pertuzumab has been becoming important for the treatment of patients with HER2-positive metastatic breast cancer.     

HER2-amplified breast cancer: mechanisms of trastuzumab resistance and novel targeted therapies

HER2 amplification is seen in up to 20% of breast cancers and is associated with an aggressive phenotype. Trastuzumab, a monoclonal antibody to HER2, accrues significant clinical benefit in the metastatic and adjuvant settings. However, some patients suffer disease recurrence despite adjuvant trastuzumab therapy, and many patients with metastatic disease do not respond to therapy or develop refractory disease within 1 year of treatment. Given the increased recognition of de novo and acquired resistance to therapy, considerable research has been dedicated to understanding the molecular mechanisms of trastuzumab resistance. Here, we highlight putative models of resistance, including activation of the downstream PI3K-signaling pathway, accumulation of a constitutively active form of HER2, and crosstalk of HER2 with other growth factor receptors. The identification of these specific mechanisms of trastuzumab resistance has provided a rationale for the development of several novel HER2-targeted agents as the mechanisms have largely suggested a continued tumor dependence on HER2 signaling. We explore the emerging data for the treatment of trastuzumab-refractory disease with novel agents including lapatinib, neratinib, pertuzumab, trastuzumab-DM1, HSP90 and PI3K pathway inhibitors, and the future potential for these inhibitors which, if combined with reliable biomarkers of resistance, may ultimately usher in a new era of personalized medicine for this disease.     

Hormone-receptor expression and activity of trastuzumab with chemotherapy in HER2-positive advanced breast cancer patients

BACKGROUND:

The relationship between quantitative immunohistochemical hormone receptor expression and response to the combination of trastuzumab with chemotherapy in HER2‐positive advanced breast cancer is currently unknown.

METHODS:

Estrogen receptor (ER) and progesterone receptor expression was studied both as a dichotomous variable (positivity set at ≥1% of positive cells) and as a continuous variable. The effect of hormone receptor expression on overall response rate and progression‐free survival in patients receiving trastuzumab‐based treatment was studied by univariate and multivariate analysis.

RESULTS:

One hundred eleven of 227 consecutive advanced breast cancer patients treated at 2 Institutions had hormone receptor‐positive tumors (49%). High expression of ER (≥30% of tumor cells) predicted reduced probability of tumor response to trastuzumab plus chemotherapy (multivariate odds ratio, 0.422; 95% confidence interval [CI], 0.222‐0.803; P = .009). In patients with hormone receptor‐positive tumors (≥1% of tumor cells), maintenance endocrine therapy added to trastuzumab upon the completion of chemotherapy was associated with a significant progression‐free survival benefit (hazard ratio, 0.521; 95% CI, 0.3325‐0.836; P = .007).

CONCLUSIONS:

Our results suggest a predictive role of hormone receptor expression in HER2‐positive tumors. Further investigation in this patient subset is warranted to optimize the use of HER2‐targeting agents, chemotherapy, and endocrine therapy. Cancer 2012;. © 2011 American Cancer Society.     

乳腺癌新的生物标志物及其治疗靶点--HER2及trastuzumab的研究进展

近年来，HER2及其单克隆抗体trastuzumab(商品名Herceptin)是乳腺癌研究的热点之一，被认为是一新的判断乳腺癌预后的独立标志物和治疗靶点，抗HER2的单抗trastuzumab对晚期，复发性及转移性乳腺癌的治疗显示出了新的前景。     

circ-ERBB2通过抑制miR-136-5p维持乳腺癌中的HER2下游信号促进曲妥珠单抗耐药

目的:探讨circ-ERBB2/miR-136-5p轴是否参与曲妥珠单抗耐药乳腺癌的耐药性分子机制。方法:qPCR法检测曲妥珠单抗敏感和耐药乳腺癌组织,以及HER2-和HER2+乳腺癌组织中circ-ERBB2和miR-136-5p的表达水平。建立小鼠异种移植瘤模型,评估敲低/过表达circ-ERBB2联合过表达/敲低miR-136-5p对乳腺癌细胞成瘤性及对曲妥珠单抗耐药性的影响。生物信息学和双荧光素酶报告基因分析circ-ERBB2与miR-136-5p的序列互作位点。CCK-8细胞增殖能力测定敲低/过表达circ-ERBB2联合过表达/敲低miR-136-5p以及给予曲妥珠单抗治疗对于乳腺癌常规或曲妥珠单抗耐药BT-474（Trast-resist）细胞增殖能力的影响。Western blot法检测敲低/过表达circ-ERBB2联合过表达/敲低miR-136-5p后,对常规或BT-474（Trast-resist）细胞内HER2、p-Akt、p-ERK1/2表达水平的影响。结果:与曲妥珠单抗敏感乳腺癌组织相比,曲妥珠单抗耐药乳腺癌组织中circ-ERBB2的表达水平显著升高,miR-136-5p表达水平显著降低（P<0.01）。无论激素受体表达为阳性或是阴性,与HER2-乳腺癌组织相比,在HER2+乳腺癌组织中circ-ERBB2表达显著上调,miR-136-5p表达水平被显著抑制（P<0.01）。敲低circ-ERBB2的表达或过表达miR-136-5p均能够抑制BT-474（Trast-resist）细胞增殖及其胞内HER2、p-Akt和p-ERK1/2的表达水平（P<0.01）。结论:circ-ERBB2能够通过抑制miR-136-5p参与维持乳腺癌中的HER2下游信号并促进曲妥珠单抗耐药。     

High efficacy of gemcitabine and cisplatin plus trastuzumab in patients with HER2-overexpressing metastatic breast cancer: a phase II study

AimsEffective and tolerable regimens are sought specifically in women who have been pre-treated with anthracyclines and taxanes. Gemcitabine and cisplatin plus trastuzumab has shown synergistic activity in vitro, and provides a new mechanism of drug interaction. This multicentre phase II study aimed to evaluate the efficacy and tolerability of gemcitabine and cisplatin plus trastuzumab in previously treated patients with metastatic breast cancer (MBC).Materials and methodsPreviously treated patients with human epidermal growth factor receptor 2 (HER2) overexpressing MBC were enrolled in a multicentre phase II study (DAKO Hercep Test 3+). Treatment consisted of gemcitabine (750 mg/m²), cisplatin (30 mg/m²) given on days 1 and 8 every 3 weeks, and trastuzumab (4 mg/kg loading dose, 2 mg/kg weekly).ResultsTwenty patients were recruited, all of whom had previously received chemotherapy (12 pre-treated with taxanes, 18 pre-treated with anthracyclines seven pre-treated with taxanes and trastuzumab). A median of six cycles of the study treatment was delivered. There were eight partial responses, for an overall response rate of 40% (95% confidence interval 16.5–63.5%). The clinical benefit rate (complete response plus partial response plus stable disease) was 80% (95% CI 54.2–95.8%). The response rate in patients who had already received a trastuzumab-based regimen for MBC was 57.1% (95% CI 7.7–100%). Median time to progression was 10.2 months, and median overall survival was 18.8 months. Main toxicities were leukopenia (grade 3 in 55% of patients) and thrombocytopenia (grade 3 in 35% and grade 4 in 5% of patients). Non-haematological toxicity was rarely severe.ConclusionsCombination chemotherapy with gemcitabine and cisplatin plus trastuzumab is well tolerated and active in patients with HER2 overexpressing MBC, even after prior exposure to anthracyclines and taxanes.