anti-HER2 Monoclonal Antibody Trastuzumab Research Articles

HER2 Testing in Gastric Cancer

Molecular therapies targeting HER2 are part of the established drug armamentarium in breast carcinoma. Now the ToGA trial, an international multicenter phase III clinical study, involving 24 countries globally, has shown that the anti-HER2 humanized monoclonal antibody Trastuzumab is effective in prolonging survival in HER2-positive carcinoma of the stomach and the gastroesophageal junction (GEJ). Similarly to breast carcinoma, >20% of gastric cancers show HER2 overexpression and/or amplification, and this percentage increases to 33% in GEJ tumors. Thus, as in breast carcinoma, pathologists are now asked to evaluate HER2 status in gastric carcinoma samples. As validated in the ToGA trial, the HER2 testing criteria that must be used in evaluating both gastric carcinoma biopsies and surgical specimens significantly differ from those routinely applied in breast carcinoma. The main variations with regard to the pattern of reactivity in HER2-expressing cells are as follows: the completeness of membrane staining is not a "conditio sine qua non" and the number of stained cells necessary to consider a case as positive is different. We must also take note of the much more frequent heterogeneity of HER2 positivity in gastric cancer compared with breast carcinoma and the less stringent correlation between HER2 amplification and protein overexpression that is observed in gastric carcinoma, where more than 20% of cases may carry HER2 amplification, although of low level, without HER2 expression. In these patients, in the ToGA trial, there was no apparent benefit from adding Trastuzumab to chemotherapy: for this reason the European Medicines Agency, while approving usage of Trastuzumab for metastatic adenocarcinoma treatment, indicated HER2 testing by immunohistochemistry as first evaluation assay, followed by fluorescence in situ hybridization in 2+ equivocal cases. HER2 testing in gastric carcinoma is a new field, opening several opportunities: for patients with gastric cancer, this is a new promising therapeutic option; for pathologists, strengthening our role in therapy selection and emphasizing our duty of providing accurate and reproducible HER2 testing results; for all interested in understanding the biology of gastric and GEJ cancer and in discovering new possible molecular therapy targets.

Triple negative breast cancer: unmet medical needs

Triple negative breast cancer (TNBC) is an aggressive clinical phenotype characterized by lack of expression (or minimal expression) of estrogen receptor (ER) and progesterone receptor (PR) as well as an absence of human epidermal growth factor receptor-2 (HER2) overexpression. It shows substantial overlap with basal-type and BRCA1-related breast cancers, both of which also have aggressive clinical courses. However, this overlap is not complete, and the expression of ER, PR, and HER2 has been noted in basal-like tumors. TNBC also includes the normal-like subtype, and not all patients with TNBC harbor BRCA1 mutations. Because of its expression profile, TNBC is not amenable to treatment with hormone therapy or the anti-HER2 monoclonal antibody trastuzumab, and systemic treatment options are currently limited to cytotoxic chemotherapy. Overall survival, whether in early-stage or advanced disease, is poor compared with that in patients who have other phenotypes. A number of targeted approaches to TNBC are undergoing clinical evaluation, including the use of agents with poly(ADP-ribose) polymerase inhibitory properties such as iniparib (the United States Adopted Name for the investigational agent BSI-201), olaparib (AZD2281), and veliparib (ABT-888), antiangiogenic agents such as bevacizumab and sunitinib, and epidermal growth factor receptor blockers such as cetuximab and erlotinib. Encouraging results with some of these agents have been reported, thereby offering the promise for improved outcomes in patients with TNBC. The clinical characteristics of TNBC and clinical experience to date with novel targeted agents under development for this aggressive phenotype is reviewed.

Pathway-focused proteomic signatures in HER2-overexpressing breast cancer with a basal-like phenotype: New insights into de novo resistance to trastuzumab (Herceptin)

Pioneering clinical studies in de novo refractoriness to the anti-HER2 monoclonal antibody trastuzumab have suggested that HER2 gene-amplification can take place also in a basal-like molecular background to generate basal/HER2+ tumors intrinsically resistant to trastuzumab. Here, we first investigated the unique histogenesis of the basal/HER2+ phenotype in breast carcinomas. The presence of basal CK5/CK6 cytokeratin expression in HER2+ tumors revealed a significant overlap in the histological features of HER2+/CK5/6+ and basal-like breast carcinomas. Basal/HER2+ tumors were typically poorly differentiated, high-grade invasive ductal carcinomas with large geographic necrosis, pushing margins of invasion, syncytial arrangement of tumor cells, ribbon- or festoon-like architecture, squamous metaplasia, stromal lymphocytic infiltrates, high mitotic index and strong p53 positivity. Secondly, we performed low-scale proteomic approaches in JIMT-1 cells, a unique model of HER2-gene amplified trastuzumab-resistant breast carcinoma with a basal-like phenotype, to develop biomarker signatures that may differentiate trastuzumab-responsive from non-responsive tumors. When applying antibody-based array technology to the extracellular milieu of trastuzumab-refractory JIMT-1 and trastuzumab-sensitive SKBR3 cell cultures, JIMT-1 cells were found to secrete higher amounts of several growth factors including amphiregulin, EGF, IGFBP-6, PDGF-AA, neurotrophins, TGFbeta and VEGF. Semi-quantitative signaling node multi-target sandwich ELISAs revealed that JIMT-1 cells drastically overactivate RelA, the prosurvival subunit of NF-kappaB as compared to trastuzumab-sensitive luminal/HER2+ SKBR3 cells. When simultaneously assessing the activation status of 42 receptor tyrosine kinases (RTK) using a human phospho-RTK array, JIMT-1 cells were found to constitutively display hyperactivation of the insulin-like growth factor-I receptor (IGF-1R). High-content immunofluorescence imaging revealed that activated IGF-1R mainly localized at focal adhesion-like structures in JIMT-1 cells. In vitro wound healing assays suggested that this functional reorganization of the JIMT-1 cytoskeletal reorganization may account for an exacerbated trastuzumab-refractory 'migratogenic' phenotype. Forthcoming studies should validate the notion that identification of basal-like immunophenotypes and/or basal-like molecular signatures within HER2+ breast carcinomas may provide rapid means to define subgroups of breast cancer patients likely to display resistance to trastuzumab ab initio.

Dynamic emergence of the mesenchymal CD44posCD24neg/low phenotype in HER2-gene amplified breast cancer cells with de novo resistance to trastuzumab (Herceptin)

Evidence is mounting that the occurrence of the CD44pos/CD24neg/low cell population, which contains potential breast cancer (BC) stem cells, could explain BC clinical resistance to HER2-targeted therapies. We investigated whether de novo refractoriness to the anti-HER2 monoclonal antibody trastuzumab (Tzb; Herceptin) may relate to the dynamic regulation of the mesenchymal CD44pos/CD24neg/low phenotype in HER2-positive BC. We observed that the subpopulation of Tzb-refractory JIMT-1 BC cells exhibiting CD44pos/CD24neg/low-surface markers switched with time. Low-passage JIMT-1 cell cultures were found to spontaneously contain ∼10% of cells bearing the CD44pos/CD24neg/low immunophenotype. Late-passage (>60) JIMT-1 cultures accumulated ∼80% of CD44pos/CD24neg/low cells and closely resembled the CD44pos/CD24neg/low-enriched (∼85%) cell population constitutively occurring in HER2-negative MDA-MB-231 mesenchymal BC cells. Dynamic expression of mesenchymal markers was not limited to CD44/CD24 because high-passages of JIMT-1 cells exhibited also reduced expression of the HER2 protein and over-secretion of pro-invasive/metastatic chemokines and metalloproteases. Accordingly, late-passage JIMT-1 cells displayed an exacerbated migratogenic phenotype in plastic, collagen, and fibronectin substrates. Intrinsic genetic plasticity to efficiently drive the emergence of the CD44pos/CD24neg/low mesenchymal phenotype may account for de novo resistance to HER2 targeting therapies in basal-like BC carrying HER2 gene amplification.

The anti-diabetic drug metformin suppresses self-renewal and proliferation of trastuzumab-resistant tumor-initiating breast cancer stem cells

We here demonstrate that the anti-diabetic drug metformin interacts synergistically with the anti-HER2 monoclonal antibody trastuzumab (Tzb; Herceptin™) to eliminate stem/progenitor cell populations in HER2-gene-amplified breast carcinoma cells. When using the mammosphere culture technique, graded concentrations of single-agent metformin (range 50-1,000 μmol/l) were found to dose-dependently reduce the number of mammospheres formed by SKBR3 (a Tzb-naïve model), SKBR3 TzbR (a model of acquired auto-resistance to Tzb) and JIMT-1 (a model of refractoriness to Tzb and other HER2-targeted therapies ab initio) HER2-overexpressing breast cancer cells. Single-agent Tzb likewise reduced mammosphere-forming efficiency (MSFE) in Tzb-naïve SKBR3 cells, but it failed to significantly decrease MSFE in Tzb-resistant SKBR3 TzbR and JIMT-1 cells. Of note, CD44-overexpressing Tzb-refractory SKBR3 TzbR and JIMT-1 cells retained an exquisite sensitivity to single-agent metformin. Concurrent combination of metformin with Tzb synergistically reduced MSFE as well as the size of mammospheres in Tzb-refractory SKBR3 TzbR and JIMT-1 cells. Flow cytometry analyses confirmed that metformin and Tzb functioned synergistically to down-regulate the percentage of Tzb-refractory JIMT-1 cells displaying the CD44(pos)/CD24(neg/low) stem/progenitor immunophenotype. Given that MSFE and mammosphere size are indicators of stem self-renewal and progenitor cell proliferation, respectively, our current findings reveal for the first time that: (a) Tzb refractoriness in HER2 overexpressors can be explained in terms of Tzb-resistant/CD44-overexpressing/tumor-initiating stem cells; (b) metformin synergistically interacts with Tzb to suppress self-renewal and proliferation of cancer stem/progenitor cells in HER2-positive carcinomas.

Ocular metastases from HER2 positive breast carcinoma and the response to combination therapy with Paclitaxel and Trastuzumab: a case report

PurposeBreast cancer is the most common tumour to metastasize to the uveal tract. The mean survival period after diagnosis of metastasis to the eye, ranges from 10 to 32 months. However, recent advances in therapy including the use of monoclonal antibody therapy, will hopefully improve treatment outcomes and prolong survival rates.MethodsWe report a case of a 45 year old woman with a HER2 positive breast cancer, who developed two metastatic lesions in the left choroid, and the left optic nerve sheath. She underwent treatment with a combination of chemotherapy (Paclitaxel) and anti-HER2 monoclonal antibodies (Trastuzumab).ResultsNine months after treatment, a B-scan showed resolution of the superior choroidal focus, as well as absence of blood flow within the optic nerve sheath. The inferonasal lesion was still present but the dimensions were reduced.ConclusionThe patient underwent a combined treatment of chemotherapy and Trastuzumab to increase the response rate. Trastuzumab is a humanized monoclonal antibody, which binds to the extracellular segment of the HER2/neu receptor. Nine months following the therapy her vision was stable, whilst one focus of the tumour in the affected eye, had regressed. The favourable response highlights the significant impact of this new therapy, as an alternative to external beam radiotherapy in patients with ocular metastasis from HER2 (+) breast cancer.

A Novel Toll-Like Receptor 9 Agonist Cooperates with Trastuzumab in Trastuzumab-Resistant Breast Tumors through Multiple Mechanisms of Action

Resistance to anti-HER2 monoclonal antibody trastuzumab is a relevant issue in breast cancer patients. Among the mechanisms implicated in trastuzumab resistance, increasing evidence supports a role of tumor microenvironment. We previously found that a novel toll-like receptor 9 agonist, referred to as immune modulatory oligonucleotide (IMO) and currently under clinical investigation, acts through epidermal growth factor receptor (EGFR) and shows direct antiangiogenic effects by cooperating with anti-EGFR or anti-VEGF drugs, thus interfering with cancer cells and microenvironment. In this study, we used KPL-4 and JIMT-1 trastuzumab-resistant breast cancer cells to evaluate the combination IMO plus trastuzumab as a therapeutic option for trastuzumab-resistant breast cancers. IMO inhibits KPL-4 and JIMT-1 xenografts growth and potentiates trastuzumab antitumor effect, with complete suppression of tumor growth, potent enhancement of trastuzumab-mediated antibody-dependent cell-mediated cytotoxicity, and strong inhibition of EGFR/HER2-related signaling. In KPL-4 xenografts, IMO alone interferes with HER signal transduction, whereas trastuzumab is ineffective. IMO induces an HER-dependent signal inhibition also in vitro by modulating a functional interaction between toll-like receptor 9 and HER receptors occurring at membrane level. Finally, IMO plus trastuzumab produces a cooperative antiangiogenic effect related to suppression of endothelial HER-related signaling. We showed a cooperative effect of IMO plus trastuzumab in trastuzumab-resistant breast cancers due to IMO direct antitumor and antiangiogenic activity and antibody-dependent cell-mediated cytotoxicity enhancement. Moreover, we provided first evidence of a toll-like receptor 9/HER interaction at membrane level as novel mechanism of action. Altogether, we propose IMO plus trastuzumab as an effective strategy in trastuzumab-resistant breast cancers.

Development and characterization of a fully functional small anti-HER2 antibody

The penetrating of monoclonal antibodies (mAbs) into solid tumor may be hampered by their large size. The antibody mimetics, composed of two complementarity-determining regions (CDRs) through a cognate framework region (FR), have been demonstrated to have the capacity to penetrate tumors superior to its parental intact IgG. In this study, we used CDR and FR sequences from the humanized anti-HER2 monoclonal antibody trastuzumab to design four antibody mimetics. Then these antibody mimetics were fused to human IgG Fc to generate mimetics-Fc small antibodies. One of the four mimetics-Fc antibodies binds well to HER2-overexpressing SK-BR3 cells and effectively inhibits the binding of trastuzumab. This mimetics-Fc, denoted as HMTI-Fc, was shown to be effective in mediating antibody-dependent cellular cytotoxicity and exhibit an antiproliferative effect in SK-BR3 cells. To our knowledge, the HMTI-Fc antibody shown here is the smallest fully functional antibody and may have a potential for treatment of cancer.

Treatment of Metastatic Breast Cancer

This observational study aimed at analyzing adherence to prescribing guidelines of anti-HER2 monoclonal antibody trastuzumab treatment for metastatic breast cancer. Efficacy and costs were also evaluated. The adherence to the trastuzumab treatment plan was analyzed according to both the French postlicensing guidelines published in 2001 and clinical guidelines from the regional cancer network in a cohort of 131 consecutive patients. The level of appropriateness to the molecular target was very high (92% of the patients showed a positive HER2 status, defined as HER2 3+ confirmed by immunohistochemistry or 2+ confirmed by fluorescent in situ hybridization). The treatment plan was made according to the French postlicensing guidelines in 41 patients (31.3%) and to the regional clinical guidelines for 109 patients (83.2%). The main reason for the difference was the type of molecules authorized for combination to trastuzumab. The median overall survival of the studied population was 18.6 months and the median progression-free survival rate was 7.7 months. Up to death or end of the study, the overall cost for the treatment of breast cancer with trastuzumab per patient and per year was 47,832 euro. This quite low adherence of clinicians to the French postlicensing guidelines is in contrast with the high level of adherence to the regional clinical guidelines. The reason is that the latter are less rigid about previously received treatments and enlarge the potential associated cytotoxics to vinorelbine. This supports the French National Cancer Institute decision to get expert clinicians involved together with the French agency for sanitary security of health products and the high health authority in a common elaboration of guidelines.

Autophagy Facilitates the Development of Breast Cancer Resistance to the Anti-HER2 Monoclonal Antibody Trastuzumab

Autophagy has been emerging as a novel cytoprotective mechanism to increase tumor cell survival under conditions of metabolic stress and hypoxia as well as to escape chemotherapy-induced cell death. To elucidate whether autophagy might also protect cancer cells from the growth inhibitory effects of targeted therapies, we evaluated the autophagic status of preclinical breast cancer models exhibiting auto-acquired resistance to the anti-HER2 monoclonal antibody trastuzumab (Tzb). We first examined the basal autophagic levels in Tzb-naive SKBR3 cells and in two pools of Tzb-conditioned SKBR3 cells (TzbR), which optimally grow in the presence of Tzb doses as high as 200 µg/ml Tzb. Fluorescence microscopic analyses revealed that the number of punctate LC3 structures -a hallmark of autophagy- was drastically higher in Tzb-refractory cells than in Tzb-sensitive SKBR3 parental cells. Immunoblotting analyses confirmed that the lipidation product of the autophagic conversion of LC3 was accumulated to high levels in TzbR cells. High levels of the LC3 lipidated form in Tzb-refractory cells were accompanied by decreased p62/sequestosome-1 protein expression, a phenomenon characterizing the occurrence of increased autophagic flux. Moreover, increased autophagy was actively used to survive Tzb therapy as TzbR pools were exquisitely sensitive to chemical inhibitors of autophagosomal formation/function. Knockdown of LC3 expression via siRNA similarly resulted in reduced TzbR cell proliferation and supra-additively interacted with Tzb to re-sensitize TzbR cells. Sub-groups of Tzb-naive SKBR3 parental cells accumulated LC3 punctate structures and decreased p62 expression after treatment with high-dose Tzb, likely promoting their own resistance. This is the first report showing that HER2-overexpressing breast cancer cells chronically exposed to Tzb exhibit a bona fide up-regulation of the autophagic activity that efficiently works to protect breast cancer cells from the growth-inhibitory effects of Tzb. Therapeutic targeting autophagosome formation/function might represent a novel molecular avenue to reduce the emergence of Tzb resistance in HER2-dependent breast carcinomas.

HER2 status testing by immunohistochemical and fFluorescence in situ hybridization in China

e22233 Background: HER2 gene overexpression is associated with aggressive breast cancer and poor clinical prognosis. Humanized anti-HER2 monoclonal antibody trastuzumab, which is targeted HER2 protein has showed to improve overall survival in patients with HER2-positive breast cancer in both the metastatic and adjuvant settings. There are some differences in HER2 positive rate among difference reports in China. This study tested HER2 status by immunohistochemistry(IHC) and fluorescence in situ hybridization (FISH) and compared HER2 testing at central and regional laboratories in China. Methods: Assessment of HER2 status was performed by FISH using the HercepTeast kit at central laboratory and by IHC using commercial available anti-HER2 probe in formalin-fixed and paraffin-embedded tissue section of 280 breast cancer samples. IHC HER2 testing was performed on 149 samples in the central laboratory. IHC HER2 testing was performed on 80 samples at both central laboratory and regional laboratory. Results: 280 samples were tested 373 times testing by IHC and FISH. The results were showed in table 1 . 80 samples was tested by IHC at central and regional laboratory and testing results of 36.4% samples were accordant (K=0.038). 94.1% IHC3+ at central laboratory were HER2 FISH positive and 83.3% IHC 3+ at regional laboratory were HER2 FISH positive. 86.7% IHC 2+ at central laboratory were HER2 FISH positive and 62.7% IHC 2+ at regional laboratory were HER2 FISH positive. 17 samples were observed HER2 FISH positive in the 27 IHC 0/1+ tested at regional laboratoty. So good correlation was obsearved between FISH HER2 status and IHC results from central laboratory but not from regional laboratory. Conclusions: This study emphasized the important of accurate HER2 testing. HER2 FISH test should be performed for the IHC 2+ samples. Even HER2 FISH test maybe performed for IHC 0/1 sample according to clinical characteristics in China in order to make the patients have targeted therapy chance. [Table: see text] No significant financial relationships to disclose.

Chemotherapy and Targeted Agents for Elderly Women with Advanced Breast Cancer

Breast cancer is the most common malignancy in women worldwide, and represents the leading cause of death in the female population. Incidence of breast cancer increases with age, and older patients are more likely to have disseminated disease at diagnosis. For those patients who relapse after endocrine treatment or in which the tumor does not express hormone receptors, chemotherapy should be considered. Single agent sequential regimens should be preferred to combination regimens, which are usually more toxic and provide a limited survival gain. New drugs which have proven efficacy against metastatic breast cancer are Taxanes (Paclitaxel and Docetaxel), Vinorelbine, Capecitabine, Gemcitabine, various and newer formulations of Anthracyclines (Epirubicin, oral Idarubicin, liposomal Doxorubicin). The anti-HER2 monoclonal antibody Trastuzumab in association with chemotherapy can be administered to elderly patients who present with HER2 overexpressing tumors, though cardiac monitoring is necessary due to cardiac adverse events. Bevacizumab, an anti-VEGF monoclonal antibody, was recently patented and approved in combination with Paclitaxel for the treatment of metastatic breast cancer. Globally, there is need to develop therapeutics able to circumvent resistance against hormonal and other therapies for advanced breast cancer, which are expected to be safe and effective in this age class.

Retrospective Evaluation of Clinical Outcomes in Patients with HER2-Positive Advanced Breast Cancer Progressing on Trastuzumab-Based Therapy in the Pre-Lapatinib Era

Background Patients with HER2-positive breast cancer whose disease has become resistant to the anti-HER2 monoclonal antibody trastuzumab can benefit from lapatinib, a dual epidermal growth factor receptor/HER2 tyrosine kinase (TK) inhibitor. Before the availability of this compound, trastuzumab was often continued beyond disease progression, usually in addition to further chemotherapy, an approach which was not based on randomized studies. We sought to retrospectively compare the clinical outcomes of patients who, upon progression during an initial trastuzumab-based regimen, stopped or continued trastuzumab in addition to further chemotherapy. Patients and Methods From the clinical records of 407 patients with HER2-positive advanced breast cancer, we identified 279 patients progressing during an initial trastuzumab-based treatment. Of these patients, 83 continued trastuzumab in addition to chemotherapy, and 112 received chemotherapy alone. Results We found no difference in response rate (28% vs. 30%; P = .5), median time to second tumor progression (8.4 months vs. 7 months; P = .24), or median postprogression survival (20.6 months and 15.4 months; P = .29) according to whether patients continued or stopped trastuzumab. At multivariate analysis, continuation of trastuzumab was associated with a statistically insignificant trend toward reduced risk of second progression (hazard ratio, 0.753; P = .08). Conclusion Patients with HER2-positive advanced breast cancer developing tumor progression during an initial trastuzumab-based regimen did not seem to benefit significantly from the continuation of trastuzumab in addition to chemotherapy. For these patients, there is evidence from a large randomized trial that effective HER2 targeting can be accomplished by inhibiting the HER2 TK activity with lapatinib.

Imaging of HER-2 Overexpression in Tumors for Guiding Therapy

Human epidermal growth factor receptor type 2 (HER2) is a transmembrane tyrosine kinase receptor, which is overexpressed in a large fraction of breast, ovarian, urinary bladder and a number of other carcinomas. Overexpression of HER2 is associated with poor prognosis. Treatment of patients with HER2-expressing breast cancer with a humanized anti-HER2 monoclonal antibody trastuzumab has resulted in improved survival. Several kinds of other anti-HER2 therapies are under development. Radionuclide molecular imaging of HER2 expression may influence patient management by selecting patients, who would benefit form anti-HER2 therapy. Other applications, such as therapy response monitoring and follow-up are also possible. In this case, the use of radionuclide imaging may overcome problems associated with biopsies, including sampling errors and discordance of expression between primary tumors and metastases. Important preconditions for development of a successful tracer for radionuclide imaging are high affinity of a targeting agent and suitable chemistry of labeling. The paper reviews information concerning major classes of HER2-targeting agents, including full-length monoclonal antibodies, their enzymatically produced fragments, engineered immunoglobulin based tracers, and alternative high affinity binders. Available information suggests that Affibody molecules or other small non-immunoglobulin based tracers have the best potential for development of high-contrast imaging agents for visualization of HER2 in vivo.

Targeting the DNA-damage response as a therapeutic strategy

Evidence is mounting that the occurrence of the CD44pos/CD24neg/low cell population, which contains potential breast cancer (BC) stem cells, could explain BC clinical resistance to HER2-targeted therapies. We investigated whether de novo refractoriness to the anti-HER2 monoclonal antibody trastuzumab (Tzb; Herceptin) may relate to the dynamic regulation of the mesenchymal CD44pos/CD24neg/low phenotype in HER2-positive BC. We observed that the subpopulation of Tzb-refractory JIMT-1 BC cells exhibiting CD44pos/CD24neg/low-surface markers switched with time. Low-passage JIMT-1 cell cultures were found to spontaneously contain ∼10% of cells bearing the CD44pos/CD24neg/low immunophenotype. Late-passage (>60) JIMT-1 cultures accumulated ∼80% of CD44pos/CD24neg/low cells and closely resembled the CD44pos/CD24neg/low-enriched (∼85%) cell population constitutively occurring in HER2-negative MDA-MB-231 mesenchymal BC cells. Dynamic expression of mesenchymal markers was not limited to CD44/CD24 because high-passages of JIMT-1 cells exhibited also reduced expression of the HER2 protein and over-secretion of pro-invasive/metastatic chemokines and metalloproteases. Accordingly, late-passage JIMT-1 cells displayed an exacerbated migratogenic phenotype in plastic, collagen, and fibronectin substrates. Intrinsic genetic plasticity to efficiently drive the emergence of the CD44pos/CD24neg/low mesenchymal phenotype may account for de novo resistance to HER2 targeting therapies in basal-like BC carrying HER2 gene amplification.

Application of intrathecal trastuzumab for treatment of meningeal carcinomatosis in HER2-overexpressing metastatic breast cancer

1138 Background: When the humanized anti-HER2 monoclonal antibody trastuzumab is given intravenously, very little reaches the cerebrospinal fluid (CSF). Thus, carcinomatous meningitis may occur in ...

Synergistic Growth Inhibition by 9-cis-Retinoic Acid Plus Trastuzumab in Human Hepatocellular Carcinoma Cells

A malfunction of retinoid X receptor-alpha (RXRalpha) due to phosphorylation by the Ras/mitogen-activated protein kinase signaling pathway is associated with the development of hepatocellular carcinoma (HCC). The humanized anti-HER2 monoclonal antibody trastuzumab inhibits the activation of HER2 and its multiple downstream signaling pathways, including the Ras/mitogen-activated protein kinase pathway. In this study, the effects of phosphorylation of RXRalpha on the ability of RXRalpha ligand 9-cis-retinoic acid (9cRA) and trastuzumab to inhibit growth of HCC cells was examined. The effects of a combination of 9cRA plus trastuzumab on the inhibition of cell growth in HLF human HCC cells which express constitutive activation of HER2 protein were examined. The combination of 9cRA plus trastuzumab synergistically inhibited the growth of HLF cells without affecting the growth of Hc normal human hepatocytes. Combined treatment with these agents acted synergistically to induce apoptosis in HLF cells. The treatment of HLF cells with trastuzumab alone inhibited the phosphorylation of HER2, RXRalpha, ERK, Akt, and Stat3 proteins and these effects were enhanced when the cells were cotreated with 9cRA. Reporter assays indicated that the combination of 9cRA plus trastuzumab markedly increased both the retinoic acid responsive element and retinoid X responsive element promoter activities in HLF cells. 9cRA and trastuzumab cooperatively inhibit the activation of HER2 and its downstream signaling pathways, subsequently inhibiting the phosphorylation of RXRalpha and the growth of HCC cells. This combination might therefore be effective for the chemoprevention and chemotherapy of HCC.

Transphosphorylation of kinase-dead HER3 and breast cancer progression: a new standpoint or an old concept revisited?

Although neither kinase-dead human epidermal growth factor receptor (HER)3 nor orphan HER2 can be activated by HER-related ligands on their own, the formation of HER2/HER3 heterodimers creates the most mitogenic and transforming receptor complex within the HER (erbB) family of transmembrane receptor tyrosine kinases. The incorporation of markers such as HER3 transactivation, HER2/HER3 dimer, or others that may provide information regarding the level of HER pathway engagement has been demonstrated to allow identification of patients who respond to or escape HER-targeted therapies. Pioneering studies showed that high expression of kinase-dead HER3 can predict early escape from the anti-HER2 monoclonal antibody trastuzumab. Also, the growth-inhibitory effects of HER1/2 tyrosine kinase inhibitors (TKIs) were previously found to be attenuated in the presence of heregulin, which is a high-affinity combinatorial ligand for HER3. All of these concepts are being revisited with respect to the efficacy of HER family TKI therapies; in particular, HER3 signalling buffered against incomplete inhibition of HER2 kinase activity has been suggested to be the mechanism that allows HER2 over-expressing breast cancer cells to escape HER TKIs. It remains to be elucidated whether reactivation of HER3 signalling can also account for the poor efficacy of HER TKIs in treating breast carcinomas that contain low overall levels of HER2 receptors. However, it appears that regardless of the mechanism that triggers the formation of oncogenic HER2/HER3 heterodimers (HER2 over-expression or overall low HER2 but high levels of the HER3 ligand heregulin), HER3 transphosphorylation is a common response of breast cancer cells upon treatment with current inhibitors of the HER receptor tyrosine kinase network. Because kinase-inactive HER3 is not presently an amenable target for forthcoming HER TKIs, molecular approaches that can efficiently block heregulin-triggered HER3 transactivation or nucleocytoplasmic trafficking of heregulin might offer novel strategies with which to manage HER-driven breast cancer disease.

2032 ORAL Detection of minimal residual disease (MRD) in peripheral blood of primary breast cancer patients – Translational research in the SUCCESS-Study

The anti-HER2 monoclonal antibody trastuzumab is central to the treatment of HER2-positive gastric cancer (GC); however, its responses are limited. HER3 seems to be the preferred dimerization partner with HER2 and is emerging as a key target for complete blockade of downstream pathways and better clinical response. In this study, we report that novel anti-HER3 antibodies (1A5–3D4) that can neutralize multiple modes of HER3 activation, combined with trastuzumab, exhibited synergistic inhibitory effect on the cell proliferation in HER2-positive GC cell lines. Follow-up studies revealed that the combination treatment significantly inhibited phosphorylation of HER3 as well as AKT and ERK signals. In vivo experiments further showed that the anti-tumor effect of trastuzumab was enhanced by its combination with 1A5–3D4 in NCI-N87 xenograft and patient derived xenografts (PDX). Particularly in an HER2-negative whereas neuregulin1 (a ligand of HER3) positive PDX, the combination was also superior to monotherapy. 1A5–3D4 in combination with trastuzumab exhibits a synergistic inhibitory effect on tumor activity, suggesting that targeting both HER2 and HER3 resulted in an improved treatment effects on HER2-positive GC.

ErbB-Dependent Signaling as a Determinant of Trastuzumab Resistance

The pathogenesis of breast cancer is profoundly influenced by the signaling cascades downstream of the human epidermal growth factor receptor (HER; also known as the ErbB receptor) family of receptor tyrosine kinases and by the HER ligands ([1][1], [2][2]). Abnormalities in the expression and