Microenvironment-Mediated Mechanisms of Resistance to HER2 Inhibitors Differ between HER2+ Breast Cancer Subtypes

Extrinsic signals are implicated in breast cancer resistance to HER2-targeted tyrosine kinase inhibitors (TKIs). To examine how microenvironmental signals influence resistance, we monitored TKI-treated breast cancer cell lines grown on microenvironment microarrays composed of printed extracellular matrix proteins supplemented with soluble proteins. We tested ~2,500 combinations of 56 soluble and 46 matrix microenvironmental proteins on basal-like HER2+ (HER2E) or luminal-like HER2+ (L-HER2+) cells treated with the TKIs lapatinib or neratinib. In HER2E cells, hepatocyte growth factor, a ligand for MET, induced resistance that could be reversed with crizotinib, an inhibitor of MET. In L-HER2+ cells, neuregulin1-β1 (NRG1β), a ligand for HER3, induced resistance that could be reversed with pertuzumab, an inhibitor of HER2-HER3 heterodimerization. The subtype-specific responses were also observed in 3D cultures and murine xenografts. These results, along with bioinformatic pathway analysis and siRNA knockdown experiments, suggest different mechanisms of resistance specific to each HER2+ subtype: MET signaling for HER2E and HER2-HER3 heterodimerization for L-HER2+ cells.

Lapatinib in the treatment of breast cancer

Within the past 2 years, four separate groups have reported marked improvement in relapse-free survival when trastuzumab was added to adjuvant chemotherapy in patients with HER2-overexpressing breast cancer. These results add further credence to the relevance of this receptor as a tumor target. Despite the significant benefits observed in early and advanced HER2-positive breast cancer, overexpression of the receptor is still associated with a poorer prognosis and an increased risk of disease relapse, even in patients with primary operable disease. Besides cytotoxic chemotherapy, and possibly hormonal therapy, patients whose tumors exhibit resistance to trastuzumab have few molecular-targeted options available. Recently, lapatinib, a small molecule dual inhibitor of both HER2 and EGF receptors, has been developed to expand the options for treating HER-positive breast cancer.

Cardiotoxicity of novel HER2-targeted therapies

BACKGROUND

Trastuzumab, an anti-HER2 humanized monoclonal antibody, is the standard treatment for both early and metastatic HER2-positive breast cancer. In addition to other chemotherapeutic agents, trastuzumab significantly improves response rate and survival in HER2-positive early and metastatic breast cancer. Although it is well known that trastuzumab therapy is closely associated with both symptomatic and asymptomatic cardiotoxicity, less is known about novel HER2-targeted therapies. The aim of this review is to discuss the cardiac safety data from recent studies of novel anti-HER2 drugs other than trastuzumab.

SCOPE

Novel HER2-targeted therapies showed favorable results in HER2 positive metastatic breast cancer patients. Pubmed database, ASCO and San Antonio Breast Cancer Symposium Meeting abstracts were searched until January 2013 using the following search keywords; 'trastuzumab, trastuzumab cardiotoxicity, HER-2 targeted therapies, lapatinib, pertuzumab, trastuzumab emtansine, afatinib and neratinib'; papers which were considered relevant for the aim of this review were selected by the authors. Lapatinib, pertuzumab, T-DM1, neratinib and afatinib molecules are evaluated in the study.

FINDINGS

In a comprehensive analysis, 3689 lapatinib treated patients enrolled in 49 trials; asymptomatic cardiac events were reported in 53 patients (1.4%) and symptomatic grade III and IV systolic dysfunction was observed only in 7 patients (0.2%) treated with lapatinib. In phase I-III trials of pertuzumab, cardiac dysfunction was seen in 4.5-14.5% of patients with pertuzumab treatment and cardiac dysfunction was usually grade I and II. Cardiotoxicity of pertuzumab was usually reported with the trastuzumab combination and no additive cardiotoxicity was reported with addition of pertuzumab to trastuzumab. T-DM1 had a better safety profile compared to trastuzumab, no significant cardiotoxicity was observed with T-DM1 in heavily pre-treated patients. In the EMILIA study, only in 1.7% of patients in the T-DM1 group experienced reduction of left ventricular ejection fraction (LVEF) and grade III LVEF reduction developed only in one patient (0.2%) in the T-DM1 group compared to the lapatinib plus capacitabine group. In phase I-II trials with neratinib no cardiotoxicity was reported whereas cardiotoxicity was seen between 0-5.3% with afatinib treatment.

CONCLUSION

Although cardiac toxicity has been reported as an adverse event for novel HER2-targeted therapies, cardiac dysfunction rate of the novel HER2-targeted therapies is significantly lower than the trastuzumab and combination of these agents with trastuzumab did not significantly increase the cardiac adverse events.

Alteration of topoisomerase II-alpha gene in human breast cancer: association with responsiveness to anthracycline-based chemotherapy

PURPOSE

Approximately 35% of HER2-amplified breast cancers have coamplification of the topoisomerase II-alpha (TOP2A) gene encoding an enzyme that is a major target of anthracyclines. This study was designed to evaluate whether TOP2A gene alterations may predict incremental responsiveness to anthracyclines in some breast cancers.

METHODS

A total of 4,943 breast cancers were analyzed for alterations in TOP2A and HER2. Primary tumor tissues from patients with metastatic breast cancer treated in a trial of chemotherapy plus/minus trastuzumab were studied for amplification/deletion of TOP2A and HER2 as a test set followed by evaluation of malignancies from two separate, large trials for changes in these same genes as a validation set. Association between these alterations and clinical outcomes was determined.

RESULTS

Test set cases containing HER2 amplification treated with doxorubicin and cyclophosphamide (AC) plus trastuzumab, demonstrated longer progression-free survival compared to those treated with AC alone (P = .0002). However, patients treated with AC alone whose tumors contain HER2/TOP2A coamplification experienced a similar improvement in survival (P = .004). Conversely, for patients treated with paclitaxel, HER2/TOP2A coamplification was not associated with improved outcomes. These observations were confirmed in a larger validation set, where HER2/TOP2A coamplification was again associated with longer survival when only anthracycline-containing chemotherapy was used for treatment compared with outcome in HER2-positive cancers lacking TOP2A coamplification.

CONCLUSION

In a study involving nearly 5,000 breast malignancies, both test set and validation set demonstrate that TOP2A coamplification, not HER2 amplification, is the clinically useful predictive marker of an incremental response to anthracycline-based chemotherapy. Absence of HER2/TOP2A coamplification may indicate a more restricted efficacy advantage for breast cancers than previously thought.

Trastuzumab emtansine, an antibody-drug conjugate for the treatment of HER2+ metastatic breast cancer

Roche Holding AG, and its subsidiaries Genentech Inc and Chugai Pharmaceutical Co Ltd, are developing trastuzumab emtansine (trastuzumab-DM1) for the treatment of HER2+ metastatic breast cancer. Trastuzumab emtansine is a tumor-activated prodrug resulting from the conjugation of the humanized anti-HER2 mAb trastuzumab, which has been used in the treatment of breast cancer for over 10 years, with ImmunoGen Inc's cytotoxic and antimitotic maytansine derivative DM1. The maytansinoids bind microtubules in a manner similar to the vinca alkaloids; however, maytansinoids have been recognized to be 20- to 100-fold more potent at blocking mitosis. Nevertheless, the use of these compounds as single agents is limited by toxicity. By conjugating DM1 with trastuzumab, the delivery of the cytotoxic agent to target cells is more specific and reduces the safety concerns. In preclinical studies, the conjugation was effective in breast cancer cell lines resistant to trastuzumab, and demonstrated complete tumor regression in SCID mice bearing KPL4 breast cancer xenografts. Clinically, trastuzumab emtansine exhibited efficacy in patients with HER2+ metastatic breast cancer who had progressed on previous chemotherapy regimens or with trastuzumab therapy. Furthermore, preclinical studies have reported that trastuzumab emtansine potentiates the effect of a number of chemotherapeutic agents (including carboplatin, 5-fluorouracil and docetaxel), other antibodies, receptor tyrosine kinase inhibitors and PI3K inhibitors, and many of these combinations are set to be tested in humans. Trastuzumab emtansine offers an exciting new option for the treatment of patients with refractory, metastatic breast cancer.

A perspective on challenges and issues in biomarker development and drug and biomarker codevelopment

A workshop sponsored by the National Cancer Institute and the US Food and Drug Administration addressed past lessons learned and ongoing challenges faced in biomarker development and drug and biomarker codevelopment. Participants agreed that critical decision points in the product life cycle depend on the level of understanding of the biology of the target and its interaction with the drug, the preanalytical and analytical factors affecting biomarker assay performance, and the clinical disease process. The more known about the biology and the greater the strength of association between an analytical signal and clinical result, the more efficient and less risky the development process will be. Rapid entry into clinical practice will only be achieved by using a rigorous scientific approach, including careful specimen collection and standardized and quality-controlled data collection. Early interaction with appropriate regulatory bodies will ensure studies are appropriately designed and biomarker test performance is well characterized.

First-line treatment options for patients with HER-2 negative metastatic breast cancer: the impact of modern adjuvant chemotherapy

The management of early breast cancer has evolved rapidly in recent years. Consequently, the range of first-line treatment options for metastatic breast cancer (MBC) is becoming increasingly complicated and therapy depends on a complex interaction of tumor, patient, and physician variables. Arguably one of the most important factors determining choice of first-line chemotherapy is prior adjuvant therapy. We have reviewed data from large, randomized clinical trials to identify the most effective regimens and help clinicians to select first-line treatment based on previous adjuvant therapy. In this review we provide recommendations on the most appropriate first-line therapy according to the type of previous adjuvant therapy. With such a wide array of treatment options available, none is likely to become the gold-standard first-line treatment for MBC. Furthermore, as increasing emphasis is placed on the quality as well as the duration of survival after development of MBC, treatment decisions should take into account tumor characteristics, toxicity, convenience, potential impact on quality of life, and patient preference, in addition to robust efficacy data.

Central nervous system metastases in HER-2 positive metastatic breast cancer patients treated with trastuzumab: incidence, survival, and risk factors

BACKGROUND

A higher incidence of central nervous system (CNS) metastases in HER-2-positive metastatic breast cancer (MBC) has recently been reported.

MATERIALS AND METHODS

Aims of this observational study were to evaluate the incidence of CNS metastases in HER-2-positive MBC patients, to define the outcome of patients with CNS metastases, and to identify the risk factors for CNS relapse.

RESULTS

Between April 1999 and June 2005 we treated 122 consecutive HER-2-positive MBC patients with chemotherapy and trastuzumab. At a median follow-up of 28 months from the occurrence of metastatic disease, 43 patients (35.2%) developed CNS metastases. The median time to death from the diagnosis of CNS metastases was 23.46 months. At multivariate analysis we found that only premenopausal status at diagnosis of breast cancer and visceral metastases as the dominant site at relapse were significantly associated with a higher risk for CNS metastases.

CONCLUSION

The CNS metastasis incidence is very high in HER-2-positive MBC, but the survival after CNS relapse in these patients is longer than in patients unselected for HER-2 status, because of the better control of extracranial disease obtained by trastuzumab. The identified risk factors for CNS relapse could allow us to select a subgroup of HER-2-positive MBC patients as candidates for active surveillance for CNS progression (by computed tomography or magnetic resonance imaging) and/or as candidates for accrual in trials of prevention of CNS relapse.

A multidisciplinary approach to the management of breast cancer, part 2: therapeutic considerations

New approaches to breast cancer treatment have enhanced clinical outcomes and patient care. These approaches include advances in breast irradiation and hormonal and systemic adjuvant therapies. In addition to the identification of new drug targets and targeted therapeutics (eg, trastuzumab), there is renewed re-emphasis in the development of biomarkers for the prediction of response to therapy. One example is the pharmacogenetics of tamoxifen metabolism and the individualization of hormonal therapy. The current treatment of breast cancer continues to evolve rapidly, with new scientific and clinical achievements constantly changing the standard of care and leading to substantial reductions in breast cancer mortality. The goal of this article is to provide clinicians who care for women with breast cancer a multidisciplinary, state-of-the art approach to the treatment of these patients.

Using specific cytotoxics with a targeted mind

It is largely known that clinical activity of a given cytotoxic agent may vary between different patients. This suggests that breast cancer sub-types can be identified within the endocrine-resistant cohort, each of them with a specific degree of sensitivity to different cytotoxic drugs. Pre-clinical and early clinical data suggest that in the future some molecular markers might have practical value in predicting cytotoxics activity in the clinical setting. The most relevant evidence is summarized below according to the type of cytotoxic agent: (a) Anthracyclines Topoisomerase II alpha (topo II) gene aberrations (amplification or deletion) and/or topo II protein overexpression seem to predict response to topo II inhibitors such as anthracyclines. Of note, HER-2 amplified tumors have a concomitant topo II gene aberration in approximately 50% of cases. Moreover, the majority of hyper-proliferating tumors carry topo II protein overexpression. Early clinical data suggest the existence of a direct correlation between anthracyclines activity and the presence of topo II gene aberration or topo II protein overexpression. (b) Taxanes Microtubule-associated parameters (MTAP) such as the TAU protein, HER-2 gene amplification, and p-53 gene mutations, have been suggested as potential predictive markers for taxanes. Although early clinical data support pre-clinical experiments, the lack of large prospectively designed clinical studies makes it difficult to draw conclusions on the predictive value of these molecular markers. (c) DNA-damaging agents The BRCA 1 protein seems to play a major role in activating DNA repair mechanisms. Loss-of-function BRCA 1 mutations might lead to a substantial deficit in DNA repair mechanisms. This could ultimately translate into increased tumor sensitivity to DNA-damaging agents such as alkylating compounds and platinum-derivates. Pre-clinical and early clinical data seem to suggest that some BRCA 1 gene mutations might render the tumor more sensitive to DNA-damaging agents and clinical studies have recently been activated to investigate properly this hypothesis. A new generation of ongoing clinical studies and a "focused" use of the gene micro-array technology will hopefully clarify the complex interaction existing between molecular targets and cytotoxic drug activity. This "targeted" approach to chemotherapy might ultimately lead to a more effective strategy in breast cancer medical treatment.

Genistein affects HER2 protein concentration, activation, and promoter regulation in BT-474 human breast cancer cells

The HER2 proto-oncogene, a member of the epidermal growth factor receptor family, is overexpressed in 20-30% of breast cancers. Genistein, the main soy isoflavone, interacts with estrogen receptors (ER) and it is also a potent tyrosine kinase inhibitor. Previously, our laboratory found that genistein delayed mammary tumor onset in transgenic mice that overexpress HER2 gene. Our goal was to define the mechanism through which genistein affects mammary tumorigenesis in HER2 overexpressing mice. We hypothesized that genistein inhibits HER2 activation and expression through ER-dependent and ER-independent mechanisms. Genistein inhibited total HER2 protein expression and tyrosine phosphorylation in BT-474, an ERalpha (-) and ERbeta (+) human breast cancer cell line, however, E2 had no effect. Taken together, these data suggest that genistein has an ER-independent inhibitory effect, presumably, through tyrosine kinase inhibition activity. Genistein at 1.0 microM mimicked E2 and down-regulated HER2 protein phosphorylation when BT-474 was co-transfected with ERalpha, but not ERbeta. Although E2 and overexpression of HER2 can promote mammary tumorigenesis, an inverse relationship between ER expression and HER2 overexpression has been found in human breast cancer. We cloned a 500-bp promoter region upstream of the HER2 transcription initiation site. Co-transfection with ERalpha, but not with ERbeta, down-regulated HER2 promoter reporter in BT-474. At concentrations > or =1 microM, genistein inhibited HER2 promoter reporter in the absence of ERalpha. In conclusion, genistein at > or =1 microM inhibited HER2 protein expression, phosphorylation, and promoter activity through an ER-independent mechanism. In the presence of ERalpha, genistein mimicked E2 and inhibited HER2 protein phosphorylation. These data support genistein's chemo-prevention and potential chemo-therapeutic roles in breast cancer.

[Paradigm shift in surgical pathology of cancer: molecular diagnostics, prognosticators and predictive pathology]

Classical methodology of surgical pathology extended first with ultrastructural methods, then with immunohistochemistry and more recently with molecular/ genomic techniques. These changes added new dimensions to the classical tissue-and cellular levels of diagnostics: the molecular level. This change is the primary motor of the development of the diagnostic as well as the prognostic and predictive pathology. It is now possible to identify an etiological factor (HPV) or reclassify an entire entity (soft tissue tumors). Prognosis of cancer relies more and more on molecular/genetic parameters such as microsatellite instability, gene amplifications etc. Targeted therapy of cancer develops parallel with the molecular predictive pathology such as the anti-HER2 or anti-EGFR therapies. In conclusion, it is fair to say that molecular pathology contributes significantly to the development of clinical oncology.

Olive oil's bitter principle reverses acquired autoresistance to trastuzumab (Herceptin) in HER2-overexpressing breast cancer cells

Background

A low incidence of breast cancer in the Mediterranean basin suggests that a high consumption of Extra Virgin Olive Oil (EVOO) might confer this benefit. While the anti-HER2 oncogene effects of the main ω-9 fatty acid present in EVOO triacylglycerols (i.e., oleic acid) have been recently described, the anti-breast cancer activities of EVOO non-glyceridic constituents -which consist of at least 30 phenolic compounds-, remained to be evaluated.

Methods

Semi-preparative HPLC was used to isolate EVOO polyphenols (i.e., tyrosol, hydroxytyrosol, oleuropein). Both the anti-proliferative and the pro-apoptotic effects of EVOO phenolics were evaluated by using MTT-based quantification of metabolically viable cells and ELISA-based detection of histone-associated DNA fragments, respectively. The nature of the interaction between oleuropein aglycone and the anti-HER2 monoclonal antibody trastuzumab (Herceptin™) was mathematically evaluated by the dose-oriented isobologram technique. HER2-specific ELISAs were employed to quantitatively assess both the basal cleavage of the HER2 extracellular domain (ECD) and the expression level of total HER2. The activation status of HER2 was evaluated by immunoblotting procedures using a monoclonal antibody specifically recognizing the tyrosine phosphorylated (Phosphor-Tyr1248) form of HER2.

Results

Among EVOO polyphenols tested, oleuropein aglycone was the most potent EVOO phenolic in decreasing breast cancer cell viability. HER2 gene-amplified SKBR3 cells were ~5-times more sensitive to oleuropein aglycone than HER2-negative MCF-7 cells. Retroviral infection of the HER2 oncogene in MCF-7 cells resulted in a "SKBR3-assimilated" phenotype of hypersensitivity to oleuropein aglycone. An up to 50-fold increase in the efficacy of trastuzumab occurred in the presence of oleuropein aglycone. A preclinical model of acquired autoresistance to trastuzumab (SKBR3/Tzb100 cells) completely recovered trastuzumab sensitivity (> 1,000-fold sensitization) when co-cultured in the presence of oleuropein aglycone. Indeed, the nature of the interaction between oleuropein aglycone and trastuzumab was found to be strongly synergistic in Tzb-resistant SKBR3/Tzb100 cells. Mechanistically, oleuropein aglycone treatment significantly reduced HER2 ECD cleavage and subsequent HER2 auto-phosphorylation, while it dramatically enhanced Tzb-induced down-regulation of HER2 expression.

Conclusion

Olive oil's bitter principle (i.e., oleuropein aglycone) is among the first examples of how selected nutrients from an EVOO-rich "Mediterranean diet" directly regulate HER2-driven breast cancer disease.

Analysis of the Pathologic Response to Primary Chemotherapy in Patients with Locally Advanced Breast Cancer Grouped According to Estrogen Receptor, Progesterone Receptor, and HER2 Status

PURPOSE

In clinical practice, it is possible to classify breast tumors according to estrogen receptor (ER), progesterone receptor (PgR), and HER2 overexpression: ER negative, PgR negative, and HER2 overexpressing; ER negative, PgR negative, and HER2 negative; ER positive, PgR positive, and HER2 negative; ER positive, PgR positive, and HER2 overexpressing; and the less frequent remaining 4 combinations. The aim of this study was to determine the percentage of pathologic complete response (pCR) in patients with locally advanced breast cancer (LABC) treated with neoadjuvant or primary chemotherapy with anthracyclines and taxanes grouped according to ER, PgR, and HER2 status.

PATIENTS AND METHODS

Patients with LABC treated with primary chemotherapy including anthracyclines and taxanes were grouped according to ER, PgR, and HER2 status; pCR rates were analyzed using the chi(2) test; and correlations with a P value of < or = 0.05 were considered statistically significant.

RESULTS

A total of 103 patients were treated. Only 100 patients were included for the analysis of pCR. Eighteen patients exhibited pCR. The pCR rate for each subgroup was as follows: 39.1% (9 of 23) had ER-negative, PgR-negative, and HER2-negative disease (P < 0.01); 35.7% (5 of 14) had ER-negative, PgR-negative, and HER2-overexpressing disease; 33.3% (3 of 9) had ER-positive, PgR-positive, and HER2-overexpressing disease; and 2.8% (1 of 36) had ER-positive, PgR-positive, and HER2-negative disease (P < 0.01).

CONCLUSION

In patients with LABC, grouping breast tumors according to ER, PgR, and HER2 status can help predict pCR to primary chemotherapy.

TOP2A and HER2 gene amplification as predictors of response to anthracycline treatment in breast cancer

The purpose of this study was to evaluate amplification of topoisomerase IIalpha (TOP2A) and HER2 genes as predictors of response to chemotherapy in advanced breast cancer. Gene copy number of TOP2A and HER2 were analysed with chromogenic in situ hybridization (CISH) on paraffin-embedded tissue sections from the primary tumour of 85 patients treated with anthracycline containing chemotherapy. TOP2A gene amplification was present in 14 (16%) and HER2 gene amplification in 38 (45%) of the primary tumours. Two of the 14 cases with TOP2A amplification were amplified without concurrent HER2 amplification. Neither TOP2A nor HER2 gene amplification were significantly associated with response to chemotherapy (p = 0.35 and p = 0.49, respectively).

Si-Wu-Tang and its constituents promote mammary duct cell proliferation by up-regulation of HER-2 signaling

OBJECTIVE

The consumption of over-the-counter natural products by perimenopausal women remains a challenging problem. It is our aim to investigate the proliferative effect of Si-Wu-Tang (SWT) and its constituents on MCF7 breast cancer cells as well as the SWT-modulated cell signaling and HER-2 gene expression.

DESIGN

By using the MCF7 (ER+, HER-2 low), BT474 (ER+, HER-2 high), MDAMB231 (ER-, HER-2 low), and SKBR3 (ER-, HER-2 high) mammary duct cell lines as our in vitro model, the mitogenic effects of SWT and its constituents were assessed by trypan blue dye exclusion assay and DNA flow cytometry. SWT-modulated cell signaling and HER-2 gene expression were evaluated in the MCF7 line by Western blot and reverse transcriptase-polymerase chain reaction analyses.

RESULTS

The results showed that SWT and some of its constituents dose-dependently stimulated cell proliferation of MCF7 cells. The activation of HER-2, its downstream signaling molecules AKT and ERK1/2, as well as HER-2 gene up-regulation were involved in SWT-stimulated cell proliferation. The addition of neutralizing antibody against HER-2 abrogated the SWT-up-regulated HER-2 expression, indicating a positive feedback control for the action of HER-2 in this setting. Ferulic acid, one of the major compounds in SWT, not only promoted cell proliferation of MCF7, BT474, MDAMB231, and SKBR3 cells, but also increased the phosphorylation of HER-2, AKT, and ERK1/2, as well as overexpression of HER-2, on MCF7 cells.

CONCLUSIONS

We conclude that SWT and its active constituents stimulate mammary duct cell proliferation by modulating HER-2, PI3K/AKT, and MAPK signaling and the positive feedback of HER-2 gene expression. This provides important information for perimenopausal women who are at risk of or have breast cancer or other growths in breast tissue.

Type II combi-molecules: design and binary targeting properties of the novel triazolinium-containing molecules JDD36 and JDE05

We recently designed molecules termed "type II combi-molecules" to block the epidermal growth factor receptor and to damage DNA without the requirement for hydrolytic cleavage. Here, we studied two such combi-molecules (JDD36 and JDE05), containing a novel quinazoline-linked chloroethyltriazolinium system. The epidermal growth factor receptor-targeting potential of these novel structures was studied by ELISA for isolated epidermal growth factor receptor and by Western blotting for whole-cell assays. DNA damage was analyzed using the single-cell microelectrophoresis comet assay. Antiproliferative effects were determined by the sulforhodamine B assay. JDD36 showed an IC50 of 0.6 micromol/l in the ELISA for epidermal growth factor receptor tyrosine kinase, a dose-dependent inhibition of epidermal growth factor receptor phosphorylation and significant levels of DNA damage in the human DU145 prostate cancer cell line. JDD36 was an overall 2- to 15-fold stronger antiproliferative agent than JDE05 that showed potent epidermal growth factor receptor inhibitory activity (IC50 epidermal growth factor receptor, 0.035 micromol/l) but weak DNA-damaging potential. In a panel of LNCaP erbB transfectants, in contrast to JDE05, JDD36 showed remarkable and selective potency against the LNCaPerbB2 transfectant. The results in toto suggest that the overall superior potency of JDD36 when compared with JDE05 may be imputed to its balanced binary epidermal growth factor receptor-DNA-targeting properties that may induce a tandem blockade of epidermal growth factor receptor-mediated mitogenic signaling while depleting alternative survival mechanism by damaging DNA.

[Inhibition of invasive and chemotactic abilities of SKOV3 cells by human epithelial growth receptor-2 small interfering RNA]

OBJECTIVE

To investigate the effects of RNA interference (RNAi) targeting human epithelial growth receptor-2 (HER-2) gene on the invasive and chemotactic ability of SKOV3 cells.

METHODS

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as the positive control. Lipofectamine 2000 mediated transient transfection was conducted to transmit the siRNA into SKOV3 cells. Three pairs of specifically targeted (HER-2 siRNAI, HER-2 siRNAII, HER-2 siRNAIII) sequence were selected in the coding region of HER-2 mRNA. Transfection of HER-2 siRNA was conducted with lipofectamine 2000 in ovarian carcinoma cell line SKOV3. The HER-2 gene expression was assessed by real-time PCR and western blot assays. Changes of invasive and chemotactic capacity of SKOV3 cells were measured by polycarbonates coated with or without matrigal.

RESULTS

Western blot results showed that the expression of GAPDH protein was decreased in specifically transfected cells and with the increase of siRNA dose, the expression of GAPDH protein was decreased. GAPDH protein gray value in control group, different doses (0.5, 1.0, 1.5, 2.0 microg) GAPDH siRNA interference groups were 0.6855 +/- 0.0259, 0.5698 +/- 0.0275, 0.4542 +/- 0.0296, 0.3341 +/- 0.0178 and 0.1816 +/- 0.0180, respectively. There was a significant difference in each group (F = 198.126, P < 0.01). Both HER-2 siRNAII and siRNAIII could inhibit the expression of HER-2 protein. There was a significant difference in inhibition of HER-2 expression between the siRNAIII (0.1562 +/- 0.0067), siRNAII (0.2162 +/- 0.1589) groups and the other groups (F = 69.461, P < 0.01). In comparison of the relative expression levels in each dose (0.5, 1.0, 1.5, 2.0 microg) group, the difference was significant (F = 174.53, P < 0.01). The relative expression of HER-2 mRNA in HER-2 siRNA group after the 1(st), 3(rd), 6(th) interference were 0.0506 +/- 0.0017, 0.0266 +/- 0.0011 and 0.0154 +/- 0.0020, respectively. There was a decreasing trend in expression levels at different times (P < 0.01). The invasion and chemotactic capacity of SKOV3 cells were decreased after transfection of HER-2 siRNA into the cell line (F = 53.707, P < 0.01 vs F = 11.361, P < 0.01).

CONCLUSIONS

HER-2 siRNAIII can silence the mRNA expression in a time and dose dependent manner. HER-2 siRNA can inhibit cell invasion and chemotactic capacity of SKOV3 cells. The application of HER-2 siRNA extends the list of available therapeutic modalities in the treatment of human ovarian cancers.

[Targeted therapies in breast cancer: current status and perspectives]

The introduction of targeted therapies has largely modified the treatment strategies in oncology. Two targets are currently used for defining the systemic treatment of breast cancer: hormone receptors and HER2 overexpression. Trastuzumab, a monoclonal antibody, is the only registered antiHER2 treatment in Belgium. The association of trastuzumab with chemotherapy is now the recommended adjuvant treatment for early breast cancer overexpressing HER2. Other antiHER2 medications are available and some will probably be registered soon. Angiogenesis is another potential target for improving the treatment results. The CHU Liège, as a reference center for the systemic treatment of solid tumors, participates in many international trials in order to validate these new approaches. The highest quality of care is required to be in compliance with the conduct of these clinical trials. Another benefit for the patient is the easy access to last generation medical treatments, generally not accessible in our health care system in Belgium outside of clinical trials.

Efficacy of c-erbB-2 antisense oligonucleotide transfection on uterine endometrial cancer HEC-1A cell lines

OBJECTIVE

Antigene therapy targeting only one oncogene has made much progress although it still has some limitations. To explore the potential for antigene therapy in uterine endometrial cancer, we examined the in vitro inhibitory effects of liposmal anti-sense phosphorothioate oligonucleotides targeting c-erbB-2 in the human uterine endometrial cancer HEC-1A cell line.

METHODS

1) To detect c-erbB-2 protein expression on HEC-1A cell membranes by immunohisto- chemistry. 2) To assay cellular growth inhibition by MTT after transfecting 0.1-0.6 microM ASODN. 3) To observe cellular and ultra-structural changes under transmission electron microscope and to assay the cellular apoptotic rate by flow cytometry and c-erbB-2 mRNA, and protein expression by RT-PCR and Western blot after transfecting 0.3 microM ASODN.

RESULTS

1) c-erbB-2 protein expression was positive on HEC-1A cell membranes. 2) With the increase of the transfecting ASODN concentration from 0.1-0.6 microM, HEC-1A cellular growth inhibition was also enhanced. The results of MTT showed that when the transfecting concentration of ASODN was 0.3 microM, the HEC-1A cellular growth inhibition rate was 50% while when the transfecting concentration of ASODN was 0.6 microM, the HEC-1A cell growth inhibition rate was 75%. 3) When the concentration of transfecting ASODNs was 0.3 microM, there were obvious vacuolar degenerations in the plasma of HEC-1A cells, disappearance of organelle and nuclear structure and obvious shrinkage of nuclei under transmission electron microscope. The cellular apoptotic rate was 62.80%, while c-erbB-2 mRNA and protein expression were 47.18% and 33.60%, respectively, compared with those of the normal control cells.

CONCLUSION

Transfecting c-erbB-2 ASODNs can obviously suppress the mRNA and protein expression in HEC-1A cells, cause cellular apoptosis and inhibit cell growth. It may be a more useful gene therapy for endometrial cancer.

HER2 (erbB-2)-targeted effects of the ϖ-3 polyunsaturated. Fatty acid α-linolenic acid (ALA; 18:3n-3) in breast cancer cells: the «fat features» of the «Mediterranean diet» as an «anti-HER2 cocktail»

BACKGROUND

Data derived from epidemiological and experimental studies suggest that alphalinolenic acid (ALA; 18:3n-3), the main omega-3 polyunsaturated fatty acid (PUFA) present in the Western diet, may have protective effects in breast cancer risk and metastatic progression. A recent pilot clinical trial assessing the effects of ALA-rich dietary flaxseed on tumor biological markers in postmenopausal patients with primary breast cancer demonstrated significant reductions in tumor growth and in HER2 (erbB-2) oncogene expression.

HYPOTHESIS

The molecular mechanism by which ALA inhibits breast cancer cell growth and metastasis formation may involve a direct regulation of HER2, a well-characterized oncogene playing a key role in the etiology, progression and response to some chemo- and endocrine therapies in approximately 20% of breast carcinomas.

METHODS

Using HER2-specific ELISA, flow cytometry, immunofluorescence microscopy, Western blotting, RT-PCR and HER2 promoter-reporter analyses, we characterized the effects of exogenous supplementation with ALA on the expression of HER2 oncogene, a master key player in the onset and metastasis formation of breast cancer disease. Metabolic status (MTT) assays were performed to evaluate the nature of the cytotoxic interaction between ALA and the humanized anti-HER2 monoclonal antibody trastuzumab (Herceptin). To study these issues we used BT-474 and SKBr-3 breast cancer cells, which naturally exhibit amplification of the HER2 oncogene.

RESULTS

ALA treatment dramatically suppressed the expression of HER2-coded p185Her-2/neu oncoprotein as determined by ELISA, flow cytometry, immunofluorescence microscopy and immunoblotting techniques. Interestingly, ALA-induced down-regulation of p185Her-2/neu correlated with a transcriptional response as no HER2 mRNA signal could be detected by RT-PCR upon treatment with optimal concentrations of ALA (up to 20 microM). Consistent with these findings, ALA exposure was found to dramatically repress the activity of a Luciferase reporter gene driven by the HER2 promoter. Moreover, the nature of the cytotoxic interaction between ALA and trastuzumab (Herceptin) revealed a significant synergism as assessed by MTT-based cell viability assays.

CONCLUSIONS

i) These findings reveal that the omega-3 PUFA ALA suppresses overexpression of HER2 oncogene at the transcriptional level, which, in turn, interacts synergistically with anti-HER2 trastuzumab- based immunotherapy. ii) Our results molecularly support a recent randomized double-blind placebo-controlled clinical trial suggesting that ALA may be a potential dietary alternative or adjunct to currently used drugs in the management of HER2-positive breast carcinomas. iii) Considering our previous findings demonstrating the <<HER2 upregulatory actions>> of the omega-6 PUFA linolenic acid (LA; 18:2n-6) and the <<HER2 down-regulatory actions >> of the omega-3 PUFA docosahexaenoic acid (DHA; 22:6n-3) and of the omega-9 monounsaturated fatty acid oleic acid (OA; 18:1n-9), it is reasonable to suggest that a low omega-6/omega-3 PUFA ratio and elevated MUFA levels, the two prominent <<fat features>> of the <<Mediterranean diet>>, should be extremely efficient at blocking HER2 expression in breast cancer cells.

Outcome of patients with HER2-positive advanced breast cancer progressing during trastuzumab-based therapy

We sought to describe patterns of treatment and clinical outcome in patients with HER2-positive advanced breast cancer progressing on trastuzumab-based therapy. One hundred eighty-four consecutive HER2-positive advanced breast cancer patients received trastuzumab-based therapy between September 1999 and September 2004. Patients were followed up until death or May 2005. For patients progressing on trastuzumab-based therapy, we calculated the response rate (RR) to the first post-progression treatment, overall survival (OS) from the first administration of trastuzumab, time to second progression (TT-SP), and post-progression survival (PPS), according to treatment. At the time of this analysis, 132 patients had progressed on trastuzumab-based therapy, and 89 had died. Of the progressing patients, 21 experienced rapid progression and could not receive additional anticancer treatments;40 patients continued trastuzumab either alone (12 patients with isolated central nervous system progression), with chemotherapy (23 patients), or with endocrine therapy (5 patients); and 71 stopped trastuzumab and received chemotherapy (61 patients) or endocrine therapy (10 patients) as the first post-progression treatment. Excluding patients with rapid progression, clinical outcomes were similar whether trastuzumab was continued or not, in terms of RR (18% and 27%, respectively), OS (31 and 30 months, respectively), TT-SP (6 and 7 months, respectively), and PPS (21 and 19 months, respectively). The clinical outcome of patients with HER2-positive advanced breast cancer progressing during trastuzumab-based therapy might not be influenced by continuing trastuzumab. The optimal therapeutic strategy in this setting of patients needs evaluation in randomized trials.

Cytokines fused to antibodies and their combinations as therapeutic agents against different peritoneal HER2/neu expressing tumors

We have previously generated antihuman HER2/neu-humanized IgG3 fused to interleukin-2 (IL-2), IL-12, or granulocyte macrophage colony-stimulating factor (GM-CSF) [monofunctional fusion proteins (mono-AbFP)] or fused to IL-2 and IL-12 or IL-12 and GM-CSF [bifunctional fusion proteins (bi-AbFP)]. These AbFPs retained cytokine and antigen-binding activities. We have now further characterized the AbFPs and determined the heparin-binding activity of the fused cytokines, their ability to trigger IFN-gamma secretion and natural killer (NK) activation, and their direct antitumor efficacy. Flow cytometry revealed heparin-binding activity in the AbFPs containing IL-12 and IL-2, although this activity seems to be decreased in the bi-AbFPs. However, both bi-AbFPs retained the capacity to stimulate IL-12-dependent IFN-gamma secretion in the NK cell line KY-1, and IL-12/IL-2 bi-AbFP induced NK activity in splenocytes. The antitumor effectiveness of bi-AbFPs and mono-AbFP combinations was studied in mice challenged i.p. with three different human HER2/neu murine syngeneic models (D2F2/E2, CT26-HER2/neu, and MC38-HER2/neu). Although a significant variability in the profile of antitumor response was observed in the different tumor models, the combination of IL-12 and GM-CSF mono-AbFPs protected 100% of D2F2/E2-challenged and 75% of CT26-HER2/neu-challenged mice. In contrast, bi-AbFPs protected less than the combination of mono-AbFPs and, in some models, even less than mono-AbFPs alone. However, in all cases, most of long-term survivors showed protection after s.c. rechallenge with the tumors and later with the parental tumors not expressing HER2/neu. These results show that, although the pattern of protection is tumor model dependent, treatments with AbFPs can effectively generate high levels of protection against peritoneal tumors expressing HER2/neu, which may be relevant in patients with primary or metastatic peritoneal carcinomatosis that may be observed in ovarian, colon, stomach, bladder, lung, and breast cancers.

Cardiac dysfunction associated with trastuzumab

The HER2/neu gene is amplified in approximately 25% of breast cancers, leading to HER2 protein overexpression and shortened overall survival and time to relapse. Trastuzumab is a humanised, monoclonal antibody against HER2, which improves survival for women with metastatic HER2-overexpressing breast cancer and reduces the risk of recurrence in women with early stage HER2-overexpressing breast cancer. Cardiac toxicity was an unexpected finding in the pivotal Phase III trial leading to the approval of trastuzumab, and prospective cardiac monitoring has, therefore, been incorporated into more recent clinical trials of trastuzumab. This article reviews the cardiac toxicity findings in key trastuzumab clinical trials and clinical characteristics of trastuzumab-associated cardiac toxicity.

Modulation of HER2 expression by ferulic acid on human breast cancer MCF7 cells

BACKGROUND

The molecular mechanisms underlying the mitogenic effect of ferulic acid (FA), an active compound derived from Angelica sinensis, have never been elucidated. It was the aim of this study to investigate the proliferative effect of FA on human breast cancer cell lines and to elucidate its modulation mechanism on HER2 expression in MCF7 line.

MATERIALS AND METHODS

By using MCF7 (oestrogen receptor-positive; ER+, HER2-low), BT474 (ER+, HER2-high), MDAMB231 (ER-, HER2-low) and SKBR3 (ER-, HER2-high) human breast cancer cell lines as in vitro models, the mitogenic effects of FA were assessed by trypan blue dye exclusion assay and DNA flow cytometry. Ferulic acid-modulated cell signalling and HER2 gene expression were evaluated in MCF7 line by Western blot and real-time RT-PCR analysis.

RESULTS

Ferulic acid ER-dependently stimulated cell proliferation on MCF7 cells in a concentration-dependent manner. The HER2 oncogene (one of the prognostic factors of breast cancer) and ESR1 gene (oestrogen receptor-alpha; ERalpha) transcription were markedly up-regulated by FA treatment. Besides, HER2 signalling and its downstream molecules such as AKT and ERK1/2 were involved in FA-modulated ERalpha and cyclin D1 synthesis. Addition of anti-HER2 antibody, trastuzumab, abrogated FA-enhanced proliferative effect on MCF7 cells, indicated a positive feedback control for the action of HER2 in this setting. The fact that the ER antagonist blocked most of the FA-up-regulated HER2 expression, and that trastuzumab down-regulated ERalpha gene expression, suggested a cross-talk between ERalpha and HER2 signalling on MCF7 cells.

CONCLUSION

The authors' conclude that FA causes human breast cancer cell proliferation by up-regulation of HER2 and ERalpha expression.

Development and therapeutic options for the treatment of raloxifene-stimulated breast cancer in athymic mice

PURPOSE

Selective estrogen receptor modulators (SERM) are used for the treatment and prevention of breast cancer (tamoxifen) and osteoporosis (raloxifene). Mechanisms of tamoxifen-resistance in breast cancer are incompletely understood but current research is focused on crosstalk between growth factor receptors and the estrogen receptor alpha (ERalpha) pathway. There is increasing clinical use of raloxifene for the treatment of osteoporosis, but the widespread use of this SERM will have consequences for the treatment of breast cancer in raloxifene-exposed women.

EXPERIMENTAL DESIGN

We took the strategic step of developing a raloxifene-resistant tumor (MCF-7RALT) model in vivo and investigating the mechanisms responsible for resistance.

RESULTS

MCF-7RALT tumors exhibited phase I SERM resistance, growing in response to SERMs and 17beta-estradiol. Epidermal growth factor receptor/HER1 and HER2/neu mRNAs were increased in MCF-7RALT tumors. The HER2/neu blocker, trastuzumab, but not the epidermal growth factor receptor blocker, gefitinib, decreased the growth of MCF-7RALT tumors in vivo. Consequently, trastuzumab decreased prosurvival/proliferative proteins: phospho-HER2/neu, total HER2/neu, phospho-Akt (protein kinase B), glycogen synthetase kinase-3, cyclin D1, and the antiapoptotic protein X chromosome-linked inhibitor of apoptosis, whereas increasing the proapoptotic protein, caspase-7, in raloxifene-treated MCF-7RALT tumors. Interestingly, ERalpha protein was overexpressed in untreated MCF-7RALT tumors and hyperactivated in cells derived from these tumors. Only fulvestrant completely inhibited the growth and ERalpha activity of MCF-7RALT tumors. The coactivator of ERalpha, amplified in breast cancer-1 protein was modestly increased in the raloxifene-treated MCF-7RALT tumors and increased both basal and estradiol-induced activity of ERalpha in cells derived from the MCF-7RALT tumors.

CONCLUSIONS

These results suggest that overexpression and increased activity of HER2/neu might be responsible for the development of raloxifene-resistant breast cancer. The results also suggest that increased expression of basal activity of ERalpha could contribute to the hypersensitivity of MCF-7RALT tumors in response to estradiol because only fulvestrant blocked growth and ERalpha activity.

Herceptin sensitizes ErbB2-overexpressing cells to apoptosis by reducing antiapoptotic Mcl-1 expression

PURPOSE

Monoclonal antibodies, such as herceptin and trastuzumab, against the epidermal growth factor receptor ErbB2 (also known as HER2/neu) are an effective therapy for breast cancer patients with overexpression of ErbB2. Herceptin, in combination with standard chemotherapy, such as taxol or etoposide, gives a synergistically apoptotic response in breast tumors.

EXPERIMENTAL DESIGN

The mechanism underlying this synergy between chemotherapy and herceptin treatment is not well understood. Herein, we have determined that addition of herceptin, sensitized breast cancer cell lines MDA-MB-231 and MCF-7 to etoposide- or taxol-induced apoptosis.

RESULTS

This treatment resulted in reduced expression of ErbB2 and the antiapoptotic Bcl-2 family member Mcl-1 in MDA-MB-231 cells. Using antisense oligonucleotides against Mcl-1, MDA-MB-231 cells were rendered sensitive to etoposide-induced apoptosis similar to herceptin, but combined treatment of antisense against Mcl-1 and herceptin failed to give a significant increase in apoptosis. In 29 human breast tumors immunostained for ErbB2 and Mcl-1, we found that when ErbB2 was overexpressed, there was a corresponding increase in Mcl-1 expression.

DISCUSSION

Using murine fibroblasts that express human ErbB2, but no other ErbB family member (NE2), these cells showed resistance to both taxol- and etoposide-induced apoptosis compared with parental cells. In addition, NE2 cells preferentially express the antiapoptotic Bcl-2 family member Mcl-1 compared with parental cells, and treatment with herceptin reduces Mcl-1 expression. Taken together, these results suggest that herceptin sensitizes ErbB2-overexpressing cells to apoptosis by reducing antiapoptotic Mcl-1 protein levels.

Mediterranean diet, olive oil and cancer

Olive oil is an integral ingredient of the "Mediterranean diet" and accumulating evidence suggests that it may have a potential role in lowering the risk of several types of cancers. The mechanisms by which the cancer-preventing effects of olive oil can be performed, however, are not known. We recently hypothesized that a novel molecular explanation concerning the anti-cancer actions of olive oil may relate to the ability of its monounsaturated fatty acid (MUFA) oleic acid (OA; 18:1n-9) to specifically regulate cancer-related oncogenes. Supporting our hypothesis, exogenous supplementation of cultured breast cancer cells with physiological concentrations of OA was found to suppress the overexpression of HER2 (Her-2/neu, erbB-2), a well-characterized oncogene playing a key role in the etiology, progression and response to chemotherapy and endocrine therapy in approximately 20% of breast carcinomas. OA treatment was also found to synergistically enhance the efficacy of trastuzumab, a humanized monoclonal antibody binding with high affinity to the ectodomain (ECD) of the Her2-coded p185(HER2) oncoprotein. Moreover, OA exposure significantly diminished the proteolytic cleavage of the ECD of HER2 and, consequently, its activation status, a crucial molecular event that determines both the aggressive behavior and the response to trastuzumab of Her2-overexpressing breast carcinomas. Our most recent findings further reveal that OA exposure may suppresses HER2 at the transcriptional level by up-regulating the expression of the Ets protein PEA3 -a DNA-binding protein that specifically blocks HER2 promoter activity- in breast, ovarian and stomach cancer cell lines. This anti-HER2 property of OA offers a previously unrecognized molecular mechanism by which olive oil may regulate the malignant behavior of cancer cells. From a clinical perspective, it could provide an effective means of influencing the outcome of Her-2/neu-overexpressing human carcinomas with poor prognosis. Indeed, OA-induced transcriptional repression of HER2 oncogene may represent a novel genomic explanation linking "Mediterranean diet", olive oil and cancer as it seems to equally operate in various types of Her-2/neu-related carcinomas.

PTEN activity could be a predictive marker of trastuzumab efficacy in the treatment of ErbB2-overexpressing breast cancer

Trastuzumab is the only HER2/neu-directed therapy to have received Food and Drug Administration approval for the treatment of patients with metastatic breast cancer. The efficacy of trastuzumab depends on the HER2/neu status of the tumour and the patient's prior treatment, but even when patients are selected on the basis of HER2/neu gene amplification, the single-agent response rate ranges from 12 to 30% and few patients respond to trastuzumab monotherapy. Here, we propose PTEN as a predictive biomarker for trastuzumab efficacy. Human breast cancer SKBR3 and drug-resistant SKBR3/R cells were investigated. We also examined clinical samples from patients who had been treated with trastuzumab and analysed the relationship between trastuzumab efficacy and PTEN level. The PI3K/Akt signalling pathway was observed to be highly active in the drug-resistant cells, and their level of PTEN was low. Delivery of antisense PTEN duplex siRNA significantly decreased the trastuzumab chemosensitivity of parental SKBR3 cells, and marked activation of Akt signalling pathway was also recognised. Moreover, immunohistochemical investigation revealed that trastuzumab treatment was remarkably successful in cells with elevated PTEN expression. Along with the immune-system-associated cytotoxic mechanism, several mechanisms have been proposed for the effect of trastuzumab. PTEN activity might play an important and major role in its HER2/PI3K/Akt-mediated antitumour effect, and could be a useful biomarker for predicting the efficacy of trastuzumab in the treatment of breast cancer.

Effect of gamma-linolenic acid on the transcriptional activity of the Her-2/neu (erbB-2) oncogene

The omega-6 polyunsaturated fatty acid gamma-linolenic acid (GLA; 18:3n-6), which is found in several plant oils and is used as an herbal medicine, has antitumor activity in vitro. We examined the effect of GLA on the expression of the Her-2/neu (erbB-2) oncogene, which is involved in development of numerous types of human cancer. Flow cytometric and immunoblotting analyses demonstrated that GLA treatment substantially reduced Her-2/neu protein levels in the Her-2/neu-overexpressing cell lines BT-474, SK-Br3, and MDA-MB-453 (breast cancer), SK-OV3 (ovarian cancer), and NCI-N87 (gastrointestinal tumor derived). GLA exposure led to a dramatic decrease in Her-2/neu promoter activity and a concomitant increase in the levels of polyomavirus enhancer activator 3 (PEA3), a transcriptional repressor of Her-2/neu, in these cell lines. In transient transfection experiments, a Her-2/neu promoter bearing a PEA3 site-mutated sequence was not subject to negative regulation by GLA in Her-2/neu-overexpressing cell lines. Concurrent treatments of Her-2/neu-overexpressing cancer cells with GLA and the anti-Her-2/neu antibody trastuzumab led to synergistic increases in apoptosis and reduced growth and colony formation.

Maspin and c-erbB-2 expression in correlation with microvessel density in invasive ductal breast cancer

Maspin is a unique member of the serpin family involved in regulation of cell migration, apoptosis and angiogenesis in breast and prostate cancers. In this study maspin expression in comparison with c-erbB-2 (HER2/neu) oncogene expression and microvessel density was investigated. The examined material included specimens of primary invasive ductal breast cancer derived from 69 patients. They were analyzed immunocytochemically to assess maspin and c-erbB-2 expression, as well as microvessel density using endothelium marker CD31. In the studied cancers, maspin expression in cancer cells was detected in more than half of the cases (50.73%). Although statistically insignificant (p=0.27), maspin expression showed decreasing tendency with the increase of tumor grade. C-erbB-2 oncogene expression was observed in 78.26% of the examined cancers. Statistically significant positive correlation was found between c-erbB-2 expression and tumor grade (p<0.005). Analysis of the dependence between maspin and c-erbB-2 expression exhibited statistically significant inverse correlation (p<0.001). Mean microvessel density (MVD) of the studied cancers was 71.64 (SD=19.36). MVD decreased with the increase of maspin expression, whereas in the cases showing c-erbB-2 overexpression MVD was clearly higher. Both correlations were statistically significant (p<0.005). In conclusion, it could be stated that increase in maspin expression is associated with weaker expression of c-erbB-2 oncogene and lower microvessel density, which implies a significant role of maspin in tumor biology. However, the exact mechanism of maspin action (including its potential role in angiogenesis), as well as the assessment of its prognostic significance in breast cancer require further studies.

Neoadjuvant chemotherapy for locally advanced breast cancer results in alterations in preoperative tumor marker status

Neoadjuvant therapy followed by breast-conserving surgery has become an acceptable option for patients with locally advanced breast cancer. Although a distinct survival benefit has not been demonstrated using this approach, several questions have been raised following such therapy including its effects on receptor status and tumor markers. The current study retrospectively reviews estrogen receptor (ER), progesterone receptor (PR), and HER2-neu status in 55 consecutive patients treated by neoadjuvant chemotherapy. Preoperative and postoperative tumor markers were available for 43 of the 55 patients (78%). The pathologic complete tumor response rate (pCR) for this group was 19 per cent (8/43). Of those patients who did not achieve a pCR (n = 35), a change in tumor markers was seen in 25.7 per cent (9/35) of patients. When compared to a control group not undergoing neoadjuvant therapy, a significantly higher percent change in marker expression was noted in the neoadjuvant group (25.7% vs 5.9%, P = 0.046). ER, PR, and HER2-neu status remain important prognostic indicators for breast cancer. Tumor markers are useful in planning adjuvant therapy regimens. In this review, nearly 19 per cent of patients achieved a pCR. In patients not achieving a pCR, one in four patients had at least one change in tumor marker status. This study demonstrates the importance of establishing receptor and marker status prior to neoadjuvant therapy, as many patients will achieve a pCR and make tumor analysis impossible. Postoperative marker studies should be performed given the possibility of a change in status. The clinical relevance of this data will require further long-term follow-up. Until such data becomes available, caution should be considered when basing adjuvant therapy regimens on preoperative tumor marker studies alone.

Downregulation of wild-type p53 protein by HER-2/neu mediated PI3K pathway activation in human breast cancer cells: its effect on cell proliferation and implication for therapy

Overexpression and activation of HER-2/neu (also known as c-erbB-2), a proto-oncogene, was found in about 30% of human breast cancers, promoting cancer growth and making cancer cells resistant to chemo- and radio-therapy. Wild-type p53 is crucial in regulating cell growth and apoptosis and is found to be mutated or deleted in 60-70% of human cancers. And some cancers with a wild-type p53 do not have normal p53 function, suggesting that it is implicated in a complex process regulated by many factors. In the present study, we showed that the overexpression of HER-2/neu could decrease the amount of wild-type p53 protein via activating PI3K pathway, as well as inducing MDM2 nuclear translocation in MCF7 human breast cancer cells. Blockage of PI3K pathway with its specific inhibitor LY294002 caused G1-S phase arrest, decreased cell growth rate and increased chemo- and radio-therapeutic sensitivity in MCF7 cells expressing wild-type p53. However, it did not increase the sensitivity to adriamycin in MDA-MB-453 breast cancer cells containing mutant p53. Our study indicates that blocking PI3K pathway activation mediated by HER-2/neu overexpression may be useful in the treatment of breast tumors with HER-2/neu overexpression and wild-type p53.

Gemcitabine in combination with trastuzumab and/or platinum salts in breast cancer cells with HER2 overexpression

Trastuzumab (Herceptin) is an effective treatment in patients with HER2-overexpressing metastatic breast cancer. Risk of trastuzumab-induced cardiotoxicity raises concerns regarding combined use with anthracyclines or other potentially cardiotoxic agents following anthracycline treatment. We characterized interactions between trastuzumab and gemcitabine (Gemzar) and the combination of gemcitabine and cisplatin or carboplatin (Paraplatin) as such combinations might help reduce the risk of cardiotoxicity. Multiple drug effect/combination index isobologram analysis was used to study the efficacy of chemotherapeutic drug plus trastuzumab combinations in HER2-overexpressing breast cancer cell lines. Combination index values were derived from parameters of the median effect plots, and statistical tests were used to determine whether the mean combination index at multiple effect levels significantly differed from a combination index value of 1.0 (values < 1.0 indicate synergy; values > 1.0, antagonism; values equal to 1.0, additivity). At a wide range of clinically achievable drug concentrations, interactions between trastuzumab and gemcitabine were synergistic at low concentrations of gemcitabine and antagonistic at high concentrations. A consistent synergistic interaction was observed with the three-drug combination of trastuzumab plus gemcitabine plus carboplatin or cisplatin. Available clinical data on the use of trastuzumab plus gemcitabine, and trastuzumab plus gemcitabine/paclitaxel, as well as clinical data on the use of gemcitabine/cisplatin in breast cancer, are discussed. These findings indicate that trastuzumab plus gemcitabine and trastuzumab plus gemcitabine plus cisplatin or carboplatin are rational combinations to evaluate in clinical trials.

Inhibition of ErbB2 causes mitochondrial dysfunction in cardiomyocytes

OBJECTIVES

We investigated the effects of erbB2 inhibition by anti-erbB2 antibody on cardiomyocyte survival and mitochondrial function.

BACKGROUND

ErbB2 is an important signal integrator for the epidermal growth factor family of receptor tyrosine kinases. Herceptin, an inhibitory antibody to the erbB2 receptor, is a potent chemotherapeutic but causes cardiac toxicity.

METHODS

Primary cultures of neonatal rat ventricular myocytes were exposed to anti-erbB2 antibody (Ab) (7.5 mug/ml) for up to 24 h. Cell viability, mitochondrial function, and apoptosis were measured using multiple complementary techniques.

RESULTS

ErbB2 inhibition was associated with a dramatic increase in expression of the pro-apoptotic Bcl-2 family protein Bcl-xS and decreased levels of anti-apoptotic Bcl-xL. There was a time-dependent increase in mitochondrial translocation and oligomerization of bcl-associated protein (BAX), as indicated by 1,6-bismaleimidohexane crosslinking. The BAX oligomerization was associated with cytochrome c release and caspase activation. These alterations induced mitochondrial dysfunction, a loss of mitochondrial membrane potential (psi) (76.9 +/- 2.4 vs. 51.7 +/- 0.1; p < 0.05; n = 4), a 35% decline in adenosine triphosphate levels (p < 0.05), and a loss of redox capacity (0.72 +/- 0.04 vs. 0.64 +/- 0.02; p< 0.01). Restoration of Bcl-xL levels through transactivating regulatory protein-mediated protein transduction prevented the decline in psi mitochondrial reductase activity and cytosolic adenosine triphosphate.

CONCLUSIONS

Anti-erbB2 activates the mitochondrial apoptosis pathway through a previously undescribed modulation of Bcl-xL and -xS, causing impairment of mitochondrial function and integrity and disruption of cellular energetics.

Heat shock protein 90

PURPOSE OF REVIEW

Heat shock protein 90 (Hsp90) is a molecular chaperone required for the stability and function of a number of conditionally activated and/or expressed signaling proteins, as well as multiple mutated, chimeric, or overexpressed signaling proteins, which promote cancer cell growth or survival or both. Hsp90 inhibitors, by interacting specifically with a single molecular target, cause the inactivation, destabilization, and eventual degradation of Hsp90 client proteins, and they have shown promising antitumor activity in preclinical model systems. One Hsp90 inhibitor, 17-AAG, has completed Phase I clinical trial, and several Phase II trials are in progress. Hsp90 inhibitors are unique in that, although they are directed towards a specific molecular target, they simultaneously inhibit multiple signaling pathways that frequently interact to promote cancer cell survival.

RECENT FINDINGS

Recently identified clients of Hsp90 participate, frequently in overlapping pathways, in mediating cancer cell survival. These include Akt, Her2, and HIF-1 alpha. Thus, by inhibiting multiple survival pathways used by cancer cells, combination of an Hsp90 inhibitor with standard chemotherapeutic agents may dramatically increase the in vivo efficacy of the standard agent. Furthermore, Hsp90 modulates androgen receptor activity and the activity of several mutated kinases characteristic of several leukemias and lymphomas, making Hsp90 inhibition an attractive modality in these cases.

SUMMARY

Hsp90 inhibitors may circumvent the characteristic genetic plasticity that has allowed cancer cells to eventually evade the toxic effects of most molecularly targeted agents. The mechanism-based use of Hsp90 inhibitors, both alone and in combination with other drugs, should augment the treatment of multiple forms of cancer.

A wrench-shaped synthetic molecule that modulates a transcription factor-coactivator interaction

Development of synthetic molecules that provide external control over the transcription of a given gene represents a challenge in medicinal and bioorganic chemistry. Here we report design and analysis of wrenchnolol, a wrench-shaped synthetic molecule that impairs the transcription of the Her2 oncogene by disrupting association of transcription factor ESX with its coactivator Sur-2. The "jaw" part of the compound mimics the alpha-helical interface of the activation domain of ESX, and the "handle" region accepts chemical modifications for a range of analysis. A water-soluble handle permitted NMR study in aqueous solution; a biotinylated handle verified the selectivity of the interaction, and a fluorescent handle confirmed the cell permeability of the compound. The case study of wrenchnolol foreshadows the promise and the challenge of targeting protein-protein interactions in the nucleus and may lead to the development of unique synthetic modulators of gene transcription.

Effect of epidermal growth factor receptor inhibitor on development of estrogen receptor-negative mammary tumors

BACKGROUND

Although antiestrogens have been effective in preventing estrogen receptor (ER)-positive breast cancer, chemopreventive agents are still needed to prevent ER-negative breast cancer. Tyrosine kinase inhibitors are promising agents for the treatment and prevention of human cancers. ZD1839 (gefitinib or Iressa) is an orally active epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor that blocks signal transduction pathways in epithelial cells. We examined whether ZD1839 blocks signal transduction and prevents the development of ER-negative breast cancer.

METHODS

The ability of ZD1839 to block signal transduction in normal, immortalized, and malignant breast cells was assessed by western blotting with specific antibodies to detect phosphorylation of cytoplasmic signaling molecules. The effect of ZD1839 on growth of these breast cells was assessed with anchorage-dependent and anchorage-independent growth assays. Its effect on ER-negative mammary tumorigenesis was assessed in MMTV-erbB2 transgenic mice. All statistical tests were two-sided.

RESULTS

ZD1839 suppressed the phosphorylation of EGFR and mitogen-activated protein kinase in normal and malignant breast cells. ZD1839 treatment statistically significantly suppressed mammary tumorigenesis in MMTV-erbB2 transgenic mice; median time to tumor development was approximately 230 days in vehicle-treated mice and more than 310 days in mice treated with ZD1839 at 100 mg/kg (P<.001). ZD1839 reduced proliferation of normal breast cells by 20.3% (95% confidence interval [CI] = -13.7% to 44.2%) and of tumor cells by 42.0% (95% CI = 20.2% to 58.2%). ZD1839 also increased expression of the cell cycle regulator p27 in normal mammary tissue by 48.7% (95% CI = 27.0% to 74.2%) and in tumor tissue by 50.3% (95% CI = 35.8% to 66.7%).

CONCLUSION

This study appears to provide the preclinical rationale for the development of these EGFR tyrosine kinase inhibitors for the prevention of human breast cancer.

Unraveling the complexities of targeted therapy treatment in cancer care

This program discussed the rationale for treatment choices in non-Hodgkin lymphoma and HER-2 positive breast cancer. The mechanisms and management of infusion, cytokine-mediated, and allergic reactions related to monoclonal antibody (MOAB) therapy were covered, as well as a summary of the mechanisms of action and toxicities of MOAB therapy in breast cancer.

Small interfering RNA (siRNA) inhibits the expression of the Her2/neu gene, upregulates HLA class I and induces apoptosis of Her2/neu positive tumor cell lines

Silencing of a specific mRNA using double stranded RNA oligonucleotides represents one of the newest technologies for suppressing a specific gene product. Small interfering RNA (siRNA) are 21 nucleotides long, double stranded RNA fragments that are identical in sequence to the target mRNA. We designed 3 such siRNA against the Her2/neu (HER2) gene. The HER2 gene is known to play an important role in the oncogenesis of several types of cancers, such as breast, ovarian, colon and gastric cancers. Introduction of the siRNA into HER2 positive tumor lines in vitro greatly reduced the cell surface expression of the HER2 protein. Concurrently, a range of effects on cell physiology, such as growth inhibition or apoptosis, was observed. The expression of HLA class I was observed to be upregulated when HER2 was silenced with siRNA. Treatment of SKBr3 and MCF7/HER2 tumor cell lines with the HER2 siRNA resulted in growth arrest of cells in the late G(1)/S-phase. Our results suggest that siRNA may be an effective method of abrogating the effect of HER2 in tumorigenesis.

The cyclooxygenase-2 inhibitor, celecoxib, prevents the development of mammary tumors in Her-2/neu mice

Evidence is now available showing that cyclooxygenase (COX)-2, which is involved in prostaglandin production, is overexpressed in many types of tumors including breast. Several reports have indicated that HER-2/neu-positive breast tumors are associated with an increased amount of COX-2 protein. In this study, we evaluated the effectiveness of the select COX-1 and COX-2 inhibitors in preventing mammary tumor development in HER-2/neu transgenic mice. At 4 weeks of age, female HER-2/neu mice were fed a #5020 rodent diet supplemented with 900 ppm celecoxib, a COX-2 inhibitor, 64 ppm of SC560, a COX-1 inhibitor, or the unsupplemented #5001 diet (control). The incidence of mammary tumors was significantly lower in the celecoxib-fed mice (71%; P = 0.001 versus control) than in the control mice (95%) or in the SC560-fed mice (91%). Celecoxib-treated mice also developed fewer tumors (1.3 +/- 1.1 SD; P = 0.039 versus control) than the control mice (2.2 +/- 1.2) or the SC560 treated mice (2.3 +/- 1.3). The median time to tumor development was 266 days in the control group versus 291 days in the celecoxib-treated group (P = 0.003 versus control). Lung metastasis was also reduced by treatment with celecoxib. The COX-1 inhibitor SC560 had no protective effect. The protection offered by celecoxib was associated with significantly lower concentrations of prostacyclin and prostaglandin E(2) in mammary tumors and their adjacent mammary glands. Our findings provide additional preclinical evidence to support the clinical studies to investigate the potential effectiveness of COX-2 inhibitors in protecting woman who are at high risk for breast cancer.