The Her-2/neu gene and protein in breast cancer 2003: biomarker and target of therapy

A personalized approach to cancer treatment: how biomarkers can help

BACKGROUND

The present approach to cancer treatment is often referred to as "trial and error" or "one size fits all." This practice is inefficient and frequently results in inappropriate therapy and treatment-related toxicity. In contrast, personalized treatment has the potential to increase efficacy and decrease toxicity.

CONTENT

We reviewed the literature relevant to prognostic, predictive, and toxicity-related markers in cancer, with particular attention to systematic reviews, prospective randomized trials, and guidelines issued by expert panels. To achieve personalized treatment for cancer, we need markers for determining prognosis, predicting response to therapy, and predicting severe toxicity related to treatment. Among the best-validated prognostic markers currently available are serum concentrations of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and lactate dehydrogenase (LDH) for patients with nonseminoma germ cell tumors and tissue concentrations of both urokinase plasminogen activator and plasminogen activator inhibitor 1 (PAI-1) for breast cancer patients. Clinically useful therapy predictive markers are estrogen and progesterone receptors to select patients with breast cancer for treatment with endocrine therapy and human epidermal growth factor receptor 2 (HER-2) to select breast cancer patients for treatment with trastuzumab (Herceptin). Markers available for identifying drug-induced adverse reactions include thiopurine methyltransferase (TPMT) to predict toxicity from thiopurines in the treatment of acute lymphoblastic leukemia and uridine diphosphate glucuronyltransferase to predict toxicity from irinotecan in the treatment of colorectal cancer.

CONCLUSIONS

Validated prognostic, predictive, and toxicity markers should help cancer treatment move from the current trial-and-error approach to more personalized treatment.

Continuing trastuzumab beyond disease progression: outcomes analysis in patients with metastatic breast cancer

INTRODUCTION

We performed a retrospective analysis of HER2-overexpressing metastatic breast cancer patients to describe clinical outcomes of those who, despite progression of the disease (PD), maintained trastuzumab for multiple chemotherapy lines. We also compared survival of these patients with that of those who halted trastuzumab at first PD.

METHODS

We identified 101 patients treated between July 2000 and January 2007. Nineteen were still receiving the first-line trastuzumab-based treatment without evidence of PD and were not included in this analysis. Of the remaining 82 patients, 59 retained trastuzumab for one or more additional lines of chemotherapy after PD, according to our institution policy. Twenty-three patients who changed treating institution and stopped trastuzumab at first progression were used as a control group.

RESULTS

For patients retaining trastuzumab, the median follow-up was 39.6 months. Clinical outcomes showed the typical degradation between first and second lines of therapy which we would expect by halting trastuzumab at first progression. Response rates were 35% and 16% and median times to progression were 7.25 and 5.25 months for the first and second lines of trastuzumab therapy, respectively. The median overall survival (OS) rates were 70 months for patients who retained trastuzumab and 56 months for patients who halted the drug (hazard ratio [HR] 0.87, 95% confidence interval [CI] 0.51 to 1.18; P = 0.52). If we consider OS from the start of trastuzumab therapy, the figures are 53.9 and 34.8 months, respectively (HR 0.78, 95% CI 0.58 to 1.32; P = 0.2).

CONCLUSION

A nonstatistically significant trend of improved survival for patients retaining trastuzumab is observed. This is in line with most retrospective analyses and recent randomized data. Retaining trastuzumab after progression is a reasonable option, but further randomized data are warranted to better define its role in comparison with other available options.

Trastuzumab as adjuvant therapy for early breast cancer: the importance of accurate human epidermal growth factor receptor 2 testing

CONTEXT

Overexpression of human epidermal growth factor receptor 2 (HER2) is an adverse prognostic parameter for patients with breast cancer. Patients with HER2-positive tumors are, however, likely to gain significant benefit from targeted therapy with trastuzumab. Four large-scale trials have assessed the efficacy and safety of adjuvant trastuzumab. In all 4 trials, disease-free survival and overall survival were significantly improved with adjuvant trastuzumab (36%-52% and 33%-41%, respectively), and improvements were observed in all patient subgroups.

OBJECTIVE

To describe, in detail, the clinical benefits of using trastuzumab in the adjuvant setting, and to emphasize the importance this places on the pathologist to correctly identify all patients with HER2-positive tumors with a high degree of accuracy.

DATA SOURCES

Published literature on both HER2 testing and the adjuvant use of trastuzumab.

CONCLUSIONS

Immunohistochemistry and/or fluorescence in situ hybridization are routinely used to determine HER2 status. Maintaining quality assurance throughout a standardized testing process is essential to achieve accurate and reproducible assay results. Adherence to the new American Society of Clinical Oncology/College of American Pathologists HER2 testing guidelines will help to ensure correct identification of all patients who may benefit from adjuvant trastuzumab and has significant implications for patient outcomes.

Correlation between NK function and response to trastuzumab in metastatic breast cancer patients

BACKGROUND

Trastuzumab is a monoclonal antibody selectively directed against Her2 and approved for the treatment of Her2 overexpressing breast cancer patients. Its proposed mechanisms of action include mediation of antibody-dependent cellular cytotoxicity (ADCC) by triggering FcgammaRIII on natural killer (NK) cells. This study addresses the correlation between overall NK function and trastuzumab's clinical activity.

SUBJECTS AND METHODS

Clinical and immunological responses were assessed in 26 patients receiving trastuzumab monotherapy as maintenance management after chemotherapy (8 mg/kg load and then standard doses of 6 mg/kg every 3 weeks). Cytotoxic activity against the MHC class I-negative standard NK target K562 cell line and HER2-specific ADCC against a trastuzumab-coated Her2-positive SKBR3 cell line were assessed in peripheral blood mononuclear cells (PBMC) harvested after the first standard dose. After six months, seventeen patients were scored as responders and nine as non-responders according to the RECIST criteria, while Progression-Free Survival (PFS) was calculated during a 12 months follow-up.

RESULTS

The responders had significantly higher levels of both NK and ADCC activities (p < 0.05) that were not different from those of eleven normal controls. The NK activity of the non-responders was significantly (p < 0.05) lower than that of the normal controls. At twelve months, there was a marked correlation between PFS and NK activity only. PFS was significantly longer in patients with high levels of NK activity, whereas its pattern was unrelated to high or low ADCC activity.

CONCLUSION

One of the mechanisms of action of trastuzumab is NK cell-mediated ADCC lysis of the Her2-positve target cell. We show here that its potency is correlated with the short-term response to treatment, whereas longer protection against tumor expansion seems to be mediated by pure NK activity.

Development of new targeted therapies for breast cancer

Clinical application of truly targeted therapy relies on identification of a specific molecular feature (the target) that is biologically relevant, reproducibly measurable and definably correlated with clinical benefit. Ideally the target should be crucial to the tumor's malignant phenotype. The target must be easily measurable in readily obtained clinical samples. Interruption, interference or inhibition of the target should yield a clinical response in a significant proportion of patients whose tumors express the target but in few patients whose tumors do not express the target. As such, targeted therapy offers the twin hopes of maximizing efficacy while minimizing toxicity. A critical review of the hallmarks of malignancy provides a framework for considering potential targets and novel therapeutic interventions. The hallmarks of malignancy include uncontrolled proliferation, insensitivity to negative growth regulation, evasion of apoptosis, lack of senescence, invasion and metastasis, angiogenesis, and genomic elasticity. Existing therapies predominantly target proliferation either with cytotoxic agents, ionizing radiation or inhibition of estrogen receptor and HER2 growth factor signaling pathways. Further improvements in therapy must attack the other hallmarks of malignancy and will undoubtedly be accompanied by better means of individual patient selection for such therapies. Indeed, each of these hallmarks presents a therapeutic opportunity. To believe otherwise would be to assume that a feature is both biologically crucial yet therapeutically unimportant, an unlikely paradox.

No strong association between HER-2/neu protein overexpression and gene amplification in high-grade invasive urothelial carcinomas

The generation of urothelial carcinoma is caused by the accumulation of various molecular changes, as in most malignancies. There are conflicting data about the status of HER-2/neu oncogene in urothelial carcinomas. The aim of this study was to determine the status of HER-2/neu oncogene in high-grade invasive urothelial carcinoma of urinary bladder both in protein and DNA level. We evaluated HER-2/neu protein overexpression by immunohistochemistry (IHC) and gene amplification by fluorescent in situ hybridization (FISH) and real-time quantitative PCR in paraffin-embedded samples of high-grade invasive urothelial carcinoma obtained from 36 patients. Polysomy 17 was also assessed by FISH. Immunohistochemically, HER-2/neu protein overexpression was observed in 22 (61.1%) tumors (ten tumors with score 3+ and 12 with score 2+). Fourteen of 36 tumors (38.9%) were evaluated as negative (score 0 or 1+). Complete concordance between FISH and the PCR was seen in all of the samples scored as 0 and 1+ by IHC. HER-2/neu gene amplification was observed in three of 27 (11.1%) tumors by FISH (nine samples were non-informative) and in eight of 36 (22.2%) tumors by the PCR. The complete concordance between HER2-2/neu protein overexpression and gene amplification was seen only in three of 27 tumors. Polysomy 17 was seen in nine tumors (33.3%). The results indicated that, in contrast to breast cancer, there was no strong association between HER-2/neu overexpression and gene amplification in invasive urothelial carcinomas, and polysomy 17 was higher in tumors showing HER-2/neu overexpression.

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.

Fulvestrant (Faslodex) -- how to make a good drug better

Fulvestrant (Faslodex); AstraZeneca Pharmaceuticals, Wilmington, DE) is an estrogen receptor (ER) antagonist with a novel mode of action; it binds, blocks, and increases degradation of ER. Fulvestrant (at the approved dose [250 mg/month]) is at least as effective as anastrozole (1 mg/day) in the treatment of postmenopausal women with hormone receptor-positive advanced breast cancer (HR(+) ABC) progressing or recurring on antiestrogen therapy, and is also an active first-line treatment. Although fulvestrant (250 mg/month) is clearly effective, it takes 3-6 months to achieve steady-state plasma levels. Steady-state concentrations are approximately twofold higher than those achieved with a single dose; reaching this earlier, for example, via a loading-dose (LD) regimen (250 mg/month plus 500 mg on day 0 and 250 mg on day 14 of month 1), may allow responses to be achieved more quickly and limit the possibility of early relapse. Fulvestrant high-dose (HD) regimens (500 mg/month) offer the possibility of greater antitumor activity, because (a) ER downregulation is a dose-dependent process (an approximately 70% reduction is observed with a single 250 mg dose of fulvestrant) and (b) evidence correlates greater ER downregulation with superior efficacy. A fulvestrant HD regimen offers the potential of achieving near 100% ER downregulation. There is also potential to increase fulvestrant-ER binding by reducing plasma estrogen levels, for example, with concomitant aromatase inhibitor treatment. Several ongoing trials use LD, HD, and combination regimens; results from these studies are awaited with interest. Meanwhile, fulvestrant (250 mg/month) remains a valuable additional endocrine treatment for postmenopausal women with HR(+) ABC recurring or progressing on antiestrogen therapy.

Soluble fragment of HER2/neu receptor in the serum of patients with breast cancer with different levels of this protein expression in the tumor

Serum level of soluble HER2/neu in patients with tumors characterized by high expression of this protein (2+/3+ according to immunohistochemical analysis) was significantly higher than in patients with low expression of HER2/neu and in women with benign diseases of the mammary glands. The level of HER2/neu in the serum decreased after removal of the primary tumor in the majority of patients.

Expression of small breast epithelial mucin (SBEM) protein in tissue microarrays (TMAs) of primary invasive breast cancers

AIMS

Small breast epithelial mucin (SBEM) is a recently described gene product that shows promise as a new breast biomarker. The aim was to investigate for the first time SBEM protein expression in a large cohort (n = 300) of invasive breast cancers, its relationship to established clinical variables and its association with clinical outcome.

METHODS AND RESULTS

Immunohistochemical analysis was performed on tissue microarrays consisting of 149 oestrogen receptor (ER) alpha- and 151 ERalpha+ breast cancers. Overall, 18% of tumours were SBEM+ (n = 53/300). However, SBEM protein was more frequently observed in ER- (22%) than in ER+ cancers (13%; P = 0.049). A significant association with psoriasin/S100A7 expression (P < or = 0.0001) was observed in the entire cohort. SBEM was also positively associated with HER-2 (P = 0.046) in ER- cancers, and increased levels of SBEM were strongly associated with higher tumour grade (P = 0.0015). Furthermore, SBEM expression showed a trend towards an association with reduced overall survival and relapse-free survival in the ER+ cohort (P = 0.063 and P = 0.072, respectively).

CONCLUSIONS

Our results suggest that SBEM may identify a unique subset of breast cancers with poor prognosis and may have future implications for therapeutic management of this disease.

t10,c12-Conjugated linoleic acid stimulates mammary tumor progression in Her2/ErbB2 mice through activation of both proliferative and survival pathways

The t10,c12 isomer of conjugated linoleic acid (CLA) inhibits rat mammary carcinogenesis, metastasis from a transplantable mouse mammary tumor and angiogenesis; however, it stimulates mammary tumorigenesis in transgenic mice overexpressing ErbB2 in the mammary epithelium (ErbB2 transgenic mice). In the current study, we report that a 4-week supplementation of the diet with 0.5% trans-10, cis-12 conjugated linoleic acid (t10,c12-CLA) stimulated the growth of established ErbB2-overexpressing mammary tumors by 30% and increased the number of new tumors from 11% to 82%. Additionally, when t10,c12-CLA supplementation of ErbB2 transgenic mice was initiated at 21 weeks of age, a time just prior to tumor appearance, overall survival was decreased from 46.4 weeks in the control to 39.0 weeks in the CLA group, and survival after detection of a palpable tumor from 7.5 to 4.6 weeks. Short-term supplementation from 10 to 14 weeks or 21 to 25 weeks of age temporarily accelerated tumor development, but over the long term, there was no significant effect on mammary tumorigenesis. Long term as well as a short 4-week supplementation increased mammary epithelial hyperplasia and lobular development, and altered the mammary stroma; this was reversible in mice returned to the control diet. t10,c12-CLA altered proliferation and apoptosis of the mammary epithelium, although this differed depending on the length of administration and/or the age of the mice. The increased tumor development with t10,c12-CLA was associated with increased phosphorylation of the IGF-I/insulin receptor, as well as increased signaling through the mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase and phosphatidylinositol 3-kinase/Akt pathways; however, neither phospho-ErbB2 nor ErbB2 was altered.

Predicting the efficacy of trastuzumab-based therapy in breast cancer: current standards and future strategies

Breast cancer is the most common female malignancy in many industrialized countries. Approximately one fourth of all women diagnosed with early breast cancer present with tumors that are characterized by erbB2 amplification. While the associated Her-2/neu receptor overexpression results in a high risk of relapse and poor prognosis, these tumors also represent a target for a selective monoclonal antibody therapy with trastuzumab (Herceptin). The combination of trastuzumab with chemotherapy has led to a considerable reduction of recurrences and to a significant reduction in breast cancer mortality both in the adjuvant and metastatic setting. Unfortunately, despite Her-2/neu overexpression, not all patients equally benefit from trastuzumab treatment, and almost all women with metastatic breast cancer eventually progress during antibody therapy. Moreover, trastuzumab is burdened with cardiotoxicity, thus increasing the risk of symptomatic congestive heart failure. In addition, the marginal costs for a 1 year therapy of trastuzumab-based therapy, which is currently considered to be the most effective treatment regimen in the adjuvant setting, may amount for up to US$ 40.000. Testing for erbB2 oncogene amplification by fluorescence in situ hybridization (FISH) and chromogenic in situ hybridization (CISH), respectively, and staining for Her-2/neu receptor overexpression by immunohistochemistry (IHC) represent the current standard for determining patient eligibility for trastuzumab-based therapy. However, while the negative predictive value of these assays for predicting the absence of benefit from trastuzumab-based therapy is sufficiently high, their positive predictive value remains insufficient, i.e. only a proportion of patients selected by these tests substantially benefit from trastuzumab-containing regimen. Accordingly, over the last years a number of biomarkers have been evaluated in their potential to predict response to trastuzumab-based therapies. These include markers auf activation of Her-2/neu (e.g., tyrosine phosphorylated Her-2/neu in tissue and cleaved Her-2/neu extracellular domain in serum) and its dimerization partners (e.g., EGFR), respectively, but also components of Her-2/neu-induced downstream signaling pathways that are crucial for the growth inhibitory effects of trastuzumab (e.g., PTEN and PI3K). Other parameters, such as topoisomerase-II alpha and c-myc co-amplifications, have also been identified as potentially useful predictors of response to trastuzumab-based chemotherapy regimen. While the benefit of these predictive biomarkers in the metastatic setting is currently explored, their usefulness in the adjuvant setting is still largely unknown. It is, however, undisputable that, within the group of Her-2/neu overexpressing tumors, further response predictors are needed in order to minimize trastuzumab-associated side effects, and to reduce the considerable societal costs that are associated with trastuzumab-based treatment regimen.

Estrogen receptor, progesterone receptor, HER-2, and response to postmastectomy radiotherapy in high-risk breast cancer: the Danish Breast Cancer Cooperative Group

PURPOSE

To examine the importance of estrogen receptor (ER), progesterone receptor (PgR), human epidermal growth factor receptor 2 (HER-2), and constructed subtypes in a large study randomly assigning patients to receive or not receive postmastectomy radiotherapy (PMRT).

PATIENTS AND METHODS

The present analysis included 1,000 of the 3,083 high-risk breast cancer patients randomly assigned to PMRT in the Danish Breast Cancer Cooperative Group (DBCG) protocol 82 trials b and c. Tissue microarray sections were stained for ER, PgR, and HER-2. Median follow-up time for patients alive was 17 years. End points were locoregional recurrence as isolated first event, distant metastases, and overall survival. For statistical analyses four subgroups were constructed from hormonal receptors (Rec). Rec+ was defined as ER+ and/or PgR+. Rec-as both ER-and PgR-. The four subgroups were Rec+/HER-2-, Rec+/HER-2+, Rec-/HER-2-(triple negative), and Rec-/HER-2+.

RESULTS

A significantly improved overall survival after PMRT was seen only among patients characterized by good prognostic markers such as hormonal receptor-positive and HER-2- patients (including the two Rec+ subtypes). No significant overall survival improvement after PMRT was found among patients with an a priori poor prognosis, the hormonal receptor-negative and HER-2+ patients, and in particular the Rec-/HER-2+ subtype. Furthermore, comparing hazard ratios and 95% CIs, significantly smaller improvements in locoregional recurrence control after PMRT were found for ER-and PgR-tumors compared with the ER+ and PgR+ tumors (P = .003 and .04, respectively), and for the triple-negative (P = .02), and the Rec-/HER-2+ subtypes (P = .003) compared with the Rec+/HER-2-subtype.

CONCLUSION

Hormonal receptor status, HER-2, and the constructed subtypes may be predictive of locoregional recurrence and survival after postmastectomy radiotherapy.

Hyaluronan-induced masking of ErbB2 and CD44-enhanced trastuzumab internalisation in trastuzumab resistant breast cancer

Although trastuzumab, a recombinant humanised anti-ErbB2 antibody, is widely used in the treatment of breast cancer, neither its mechanism of action, nor the factors leading to resistance are fully understood. We have previously shown that antibody-dependent cellular cytotoxicity is pivotal in the in vivo effect of trastuzumab against JIMT-1, a cell line showing in vitro resistance to the antibody, and suggested that masking of the trastuzumab-binding epitope by MUC-4, a cell surface mucin, took place. Here, we further explored the role of masking of ErbB2 in connection with CD44 expression and synthesis of its ligand, hyaluronan. We show that high expression of CD44 observed in JIMT-1 cells correlates with ErbB2 downregulation in vivo, while siRNA-mediated inhibition of CD44 expression leads to decreased rate of trastuzumab internalisation and low cell proliferation in vitro. An inhibitor of hyaluronan synthesis, 4-methylumbelliferon (4-MU) significantly reduced the hyaluronan level of JIMT-1 cells both in vivo and in vitro leading to enhanced binding of trastuzumab to ErbB2 and increased ErbB2 down-regulation. Furthermore, the inhibitory effect of trastuzumab on the growth of JIMT-1 xenografts was significantly increased by 4-MU treatment. Our results point to the importance of the CD44-hyaluronan pathway in the escape of tumour cells from receptor-oriented therapy.

Trastuzumab and gemcitabine as salvage therapy in heavily pre-treated patients with metastatic breast cancer

PURPOSE

In Her2-postive metastatic breast carcinoma, first-line trastuzumab-based therapy is well established; many centres continue antibody treatment beyond disease progression. In this trial, we evaluated the efficacy and safety of gemcitabine and trastuzumab after earlier exposure to anthracyclines, docetaxel and/or vinorelbine, and trastuzumab.

METHODS

Twenty-nine consecutive patients were included as eligible. Patients received gemcitabine at a dose of 1,250 mg/m2 on day one and eight, every 21 days. Trastuzumab was administered in three-week cycles. Clinical benefit rate (CBR; CR + PR + SD > or = 6 months) was defined as primary endpoint.

RESULTS

As of July 2007, all patients are evaluable for toxicity, and 26 for response. Earlier therapies consisted of trastuzumab (100%), anthracyclines (100%), vinorelbine (96.6%), docetaxel (72.4%), and capecitabine (72.4%). 19.2% of patients experienced PR, and SD > or = 6 months was observed in a further 26.9%, resulting in a CBR of 46.2%. Time to progression was median 3 months, and overall survival 17 months. Neutropenia (20.7%), thrombocytopenia (13.8%), and nausea (3.4%) were the only treatment-related adverse events that occurred with grade 3 or 4 intensity. Four patients (13.8%) developed brain metastases while on therapy.

CONCLUSIONS

While CBR was low when compared to trastuzumab-based first-line therapy, it is higher than what would be expected from gemcitabine monotherapy in a similar setting. Together with the favourable toxicity profile, this regimen appears to be a safe and potentially effective salvage therapy option in a heavily pre-treated population.

Tight correlation between expression of the Forkhead transcription factor FOXM1 and HER2 in human breast cancer

Background

FOXM1 regulates expression of cell cycle related genes that are essential for progression into DNA replication and mitosis. Consistent with its role in proliferation, elevated expression of FOXM1 has been reported in a variety of human tumour entities. FOXM1 is a gene of interest because recently chemical inhibitors of FOXM1 were described to limit proliferation and induce apoptosis in cancer cells in vitro, indicating that FOXM1 inhibitors could represent useful anticancer therapeutics.

Methods

Using immunohistochemistry (IHC) we systematically analysed FOXM1 expression in human invasive breast carcinomas (n = 204) and normal breast tissues (n = 46) on a tissue microarray. Additionally, using semiquantitative realtime PCR, a collection of paraffin embedded normal (n = 12) and cancerous (n = 25) breast tissue specimens as well as benign (n = 3) and malignant mammary cell lines (n = 8) were investigated for FOXM1 expression. SPSS version 14.0 was used for statistical analysis.

Results

FOXM1 was found to be overexpressed in breast cancer in comparison to normal breast tissue both on the RNA and protein level (e.g. 8.7 fold as measured by realtime PCR). We found a significant correlation between FOXM1 expression and the HER2 status determined by HER2 immunohistochemistry (P < 0.05). Univariate survival analysis showed a tendency between FOXM1 protein expression and unfavourable prognosis (P = 0.110).

Conclusion

FOXM1 may represent a novel breast tumour marker with prognostic significance that could be included into multi-marker panels for breast cancer. Interestingly, we found a positive correlation between FOXM1 expression and HER2 status, pointing to a potential role of FOXM1 as a new drug target in HER2 resistant breast tumour, as FOXM1 inhibitors for cancer treatment were described recently. Further studies are underway to analyse the potential interaction between FOXM1 and HER2, especially whether FOXM1 directly activates the HER2 promoter.

Do medulloblastoma tumors meet the Food and Drug Administration criteria for anti-erbB2 therapy with trastuzumab?

Several publications have recently focused on the erbB2 receptor in pediatric medulloblastomas (MBs) and its prognostic consequence. We determined erbB2 expression in 23 MBs at diagnosis. After DNA extraction, quantitative PCR targeting the erbB2 gene was performed and correlated with FISH analysis and immunohistochemistry. The samples were representative of the spectrum of the disease apart from the absence of large cell MBs. Using the tools validated for breast cancers by the FDA, we did not observe any expression or amplification of erbB2 and hence we speculate that MBs are not a good target for treatment with anti-erbB2 antibodies.

Trastuzumab decreases the number of circulating and disseminated tumor cells despite trastuzumab resistance of the primary tumor

We have recently shown that despite of the fact that the ErbB2-positive JIMT-1 human breast cancer cells intrinsically resistant to trastuzumab in vitro, trastuzumab inhibited the outgrowth of early phase JIMT-1 xenografts in SCID mice via antibody-dependent cellular cytotoxicity (ADCC). Here we show that trastuzumab significantly reduces the number of circulating and disseminated tumor cells (CTCs and DTCs) in this xenograft model system at a time when the primary tumor is already unresponsive to trastuzumab. This observation suggests that ErbB2 positive CTCs and DTCs might be sensitive to trastuzumab-mediated ADCC even if when the primary tumor is already non-responsive. Thus, trastuzumab treatment might also be beneficial in the case of patients with breast cancer that is already trastuzumab resistant.

The chemokine CCL5 as a potential prognostic factor predicting disease progression in stage II breast cancer patients

PURPOSE

The aim of this study was to determine the prognostic value of the chemokine CCL5, considered as a promalignancy factor in breast cancer, in predicting breast cancer progression and to evaluate its ability to strengthen the prognostic significance of other biomarkers.

EXPERIMENTAL DESIGN

The expression of CCL5, alone and in conjunction with estrogen receptor (ER)-alpha, ER-beta, progesterone receptor (PR), and HER-2/neu (ErbB2), was determined in breast tumor cells by immunohistochemistry. The study included 142 breast cancer patients, including individuals in whom disease has progressed.

RESULTS

Using Cox proportional hazard models, univariate analysis suggested that, in stage I breast cancer patients, CCL5 was not a significant predictor of disease progression. In contrast, in stage II patients, the expression of CCL5 (CCL5(+)), the absence of ER-alpha (ER-alpha(-)), and the lack of PR expression (PR(-)) increased significantly the risk for disease progression (P = 0.0045, 0.0041, and 0.0107, respectively). The prognostic strength of CCL5, as well as of ER-alpha(-), improved by combining them together (CCL5(+)/ER-alpha(-): P = 0.0001), being highly evident in the stage IIA subgroup [CCL5(+)/ER-alpha(-) (P = 0.0003); ER-alpha(-) (P = 0.0315)]. In the stage II group as a whole, the combinations of CCL5(-)/ER-alpha(+) and CCL5(-)/PR(+) were highly correlated with an improved prognosis. Multivariate analysis indicated that, in stage II patients, ER-alpha and CCL5 were independent predictors of disease progression.

CONCLUSIONS

CCL5 could be considered as a biomarker for disease progression in stage II breast cancer patients, with the CCL5(+)/ER-alpha(-) combination providing improved prediction of disease progression, primarily in the stage IIA subgroup.

Increased survival in dogs with malignant mammary tumours overexpressing HER-2 protein and detection of a silent single nucleotide polymorphism in the canine HER-2 gene

The aims of this study were to explore the relationship between clinical outcome and HER-2 protein expression in dogs with malignant mammary tumours after surgery and to determine the sequence of the HER-2 gene. Tissues from 91 dogs diagnosed with malignant mammary tumours, six with benign lesions and two normal mammary glands were analysed for the expression of HER-2 by immunohistochemistry (IHC). Exons 14-18 of the HER-2 gene were amplified by reverse transcriptase polymerase chain reaction and sequenced in 19 tumours with IHC scores >2+; larger coding regions of HER-2 were analysed in five tumours. HER-2 protein overexpression was found in 27/91 (29.7%) of canine malignant mammary tumours. Dogs with HER-2-overexpressing malignant mammary tumours tended to have a higher survival rate than those that expressed a normal level of HER-2 within 2 years of surgery. In 3/19 cases, HER-2 sequences had a single nucleotide polymorphism, T(1725)C, with no change in the amino acid identity (Cys). No other sequence aberration of HER-2 was found.

Leptin augments proliferation of breast cancer cells via transactivation of HER2

Excessive fat mass is a risk factor for postmenopausal breast cancer. Leptin, a fat cell-derived peptide hormone, elicits a growth-stimulating effect in breast cancer cells with leptin receptor expression, although the leptin-induced signal in malignant cells is not fully understood. Here, we found that exogenous leptin induced tyrosine phosphorylation of HER2 in SKBR3 cells, which showed marked overexpression of HER2. Phosphorylation of HER2 was detected at 2 min and continued up to 120 min after the start of stimulation. Leptin-induced HER2 phosphorylation was partially reduced by an epidermal growth factor receptor inhibitor, AG1478, or a Janus-activated kinase inhibitor, AG490. Leptin also induced phosphorylation of extracellular signal-regulated kinase 1/2, which was mostly abrogated by a HER2 tyrosine kinase inhibitor, AG825. In a proliferation assay, addition of 500 ng/mL leptin increased the proliferation of SKBR3, which was totally inhibited by AG825. Collectively, our data suggest that leptin can transactivate HER2 through both epidermal growth factor receptor and Janus-activated kinase 2 activation, which can cause the growth of breast cancer cells with HER2 overexpression.

Association of low repair efficiency with high hormone receptors expression and SOD activity in breast cancer patients

OBJECTIVES

To evaluate the antioxidant status and repair capacity in breast cancer patients as well as the relationship between these parameters and expression of critical proteins in breast cancer tissue.

DESIGN AND METHODS

Blood samples were obtained from 25 female breast cancer patients and 19 healthy women. The antioxidant status was determined by the concentration of thiobarbituric-reactive substances (TBARS) and activity of superoxide dismutase (SOD) and catalase (CAT). The basal DNA damage and repair capacity in lymphocytes were evaluated by comet assay. The expression of p53, c-erbB2, Ki-67, estrogen receptor (ER) and progesterone receptor (PR) in cancer tissue was detected by immunohistochemical staining.

RESULTS

The breast cancer patients presented significantly elevated endogenous DNA damage in lymphocytes and lower susceptibility to DNA damage induced by H(2)O(2) when compared to the control group. There is a negative correlation between TBARS and sensitivity to peroxide induced DNA damage in patients. The percentage of residual damage after H(2)O(2) treatment followed by 3h of post-incubation is significantly higher in patients and also correlates positively with SOD activity, ER and PR expression and negatively with the basal DNA damage.

CONCLUSIONS

Our results demonstrate low repair capacity in lymphocytes of breast cancer patients and suggest that the regulation of DNA repair is sensitive to cellular redox state and can be modulated by ER/PR status.

Progesterone receptor expression is a marker for early stage breast cancer: implications for progesterone receptor as a therapeutic tool and target

We determined the association of estrogen receptor (ER) and progesterone receptor (PR) expression in invasive breast cancer with stage at diagnosis. Univariate analyses indicated that although ER and PR expression were inversely associated with grade (P<0.0001), only PR expression (P<0.01) was inversely associated with stage. Multivariate analyses, adjusted for covariates, including HER-2/neu expression, indicated that PR (odds ratio (OR), 0.88; confidence interval (CI), 0.77-0.99; P=0.03) and not ER expression (OR, 1.04; CI, 0.94-1.16; P=0.45) was inversely associated with stage. PR and not ER expression is a marker for early stage breast cancer.

HER2 status in breast cancer--an example of pharmacogenetic testing

The development of new drugs and associated pharmacogenetic tests will provide an increasing number of challenges to health care systems. In particular, how to evaluate their benefits, prioritize for commissioning purposes and implement a service to provide them in a timely manner. This paper presents an overview of HER2 testing for trastuzumab (Herceptin) treatment in breast cancer cases. Immunohistochemistry and fluorescence in situ hybridization laboratory techniques are described and their HER2 testing performances are compared. Future options for the national provision of HER2 testing by the National Health Service in the UK are also discussed.

HER2 status in breast cancer--an example of pharmacogenetic testing

The development of new drugs and associated pharmacogenetic tests will provide an increasing number of challenges to health care systems. In particular, how to evaluate their benefits, prioritize for commissioning purposes and implement a service to provide them in a timely manner. This paper presents an overview of HER2 testing for trastuzumab (Herceptin) treatment in breast cancer cases. Immunohistochemistry and fluorescence in situ hybridization laboratory techniques are described and their HER2 testing performances are compared. Future options for the national provision of HER2 testing by the National Health Service in the UK are also discussed.

The role of osteopontin in tumor progression and metastasis in breast cancer

The use of cancer biomarkers to anticipate the outlines of disease has been an emerging issue, especially as cancer treatment has made such positive steps in the last few years. Progress in the development of consistent malignancy markers is imminent because advances in genomics and bioinformatics have allowed the examination of immense amounts of data. Osteopontin is a phosphorylated glycoprotein secreted by activated macrophages, leukocytes, and activated T lymphocytes, and is present in extracellular fluids, at sites of inflammation, and in the extracellular matrix of mineralized tissues. Several physiologic roles have been attributed to osteopontin, i.e., in inflammation and immune function, in mineralized tissues, in vascular tissue, and in kidney. Osteopontin interacts with a variety of cell surface receptors, including several integrins and CD44. Binding of osteopontin to these cell surface receptors stimulates cell adhesion, migration, and specific signaling functions. Overexpression of osteopontin has been found in a variety of cancers, including breast cancer, lung cancer, colorectal cancer, stomach cancer, ovarian cancer, and melanoma. Moreover, osteopontin is present in elevated levels in the blood and plasma of some patients with metastatic cancers. Therefore, suppression of the action of osteopontin may confer significant therapeutic activity, and several strategies for bringing about this suppression have been identified. This review looks at the recent advances in understanding the possible mechanisms by which osteopontin may contribute functionally to malignancy, particularly in breast cancer. Furthermore, the measurement of osteopontin in the blood or tumors of patients with cancer, as a way of providing valuable prognostic information, will be discussed based on emerging clinical data.

Trastuzumab causes antibody-dependent cellular cytotoxicity-mediated growth inhibition of submacroscopic JIMT-1 breast cancer xenografts despite intrinsic drug resistance

Trastuzumab is a recombinant antibody drug that is widely used for the treatment of breast cancer. Despite encouraging clinical results, some cancers are primarily resistant to trastuzumab, and a majority of those initially responding become resistant during prolonged treatment. The mechanisms of trastuzumab resistance have not been fully understood. We examined the role of antibody-dependent cellular cytotoxicity (ADCC) using JIMT-1 cells that are ErbB2 positive but intrinsically resistant to trastuzumab in vitro. Unexpectedly, in experiments mimicking adjuvant therapy of submacroscopic disease in vivo (JIMT-1 cells inoculated s.c. in severe combined immunodeficiency mice), trastuzumab was able to inhibit the outgrowth of macroscopically detectable xenograft tumors for up to 5-7 weeks. The effect is likely to be mediated via ADCC because trastuzumab-F(ab')(2) was ineffective in this model. Moreover, in vitro ADCC reaction of human leukocytes was equally strong against breast cancer cells intrinsically sensitive (SKBR-3) or resistant (JIMT-1) to trastuzumab or even against a subline of JIMT-1 that was established from xenograft tumors growing despite trastuzumab treatment. These results suggest that ADCC may be the predominant mechanism of trastuzumab action on submacroscopic tumor spread. Thus, measuring the ADCC activity of patient's leukocytes against the tumor cells may be a relevant predictor of clinical trastuzumab responsiveness in vivo.

HER-2 overexpression/amplification and its interaction with taxane-based therapy in breast cancer

Breast cancer (BC) is the most common cancer in women and it is incurable when metastases are diagnosed. Taxanes, namely docetaxel and paclitaxel, are effective chemotherapeutic agents in the metastatic, neoadjuvant and adjuvant settings. HER-2 overexpression/amplification is detected in 25-30% of BCs and confers aggressive tumor behavior as well as resistance to some systemic treatments; nevertheless, its association with response to taxane-based chemotherapy is still unclear, with conflicting results in both in vitro and in vivo preclinical studies. This review will address the impact of HER-2 overexpression/amplification in BC patients treated with taxanes. Prospective, randomized trials incorporating important biological hypotheses are either ongoing or just closed, and their results will hopefully help to shed more light on this issue.

HER2 gene status in primary breast cancers and matched distant metastases

Introduction

The status of the gene encoding human EGF-like receptor 2 (HER2) is an important prognostic and predictive marker in breast cancer. Only breast cancers with HER2 amplification respond to the targeted therapy with trastuzumab. It is controversial to what degree the primary tumour is representative of distant metastases in terms of HER2 status. Discrepancies in HER2 status between primary tumours and distant metastases have been described, but their reasons remain unclear. Here, we compared HER2 status on cytological specimens of distant metastases with the result from the primary carcinomas, and explored the prevalence of and the reasons for discrepant results.

Methods

HER2 status was determined by fluorescence in situ hybridisation. HER2 gene amplification was defined as a HER2/chromosome 17 signal ratio of 2 or more. HER2 results from cytological specimens of matched distant metastases were compared with the results from the corresponding primary tumours (n = 105 patients). In addition, lymph node metastases were analysed in 31 of these patients.

Results

HER2 amplification was found in 20% of distant metastases. HER2 status was discordant between the primary tumour and distant metastasis in 7.6% of the 105 patients. Re-evaluation revealed that in five patients (4.7%), discrepancies were due to interpretational difficulties. In two of these patients, focal amplification had initially been overlooked as a result of heterogeneity in the primary tumours or in the metastases, respectively. A further three patients had borderline amplification with a ratio close to 2. Discrepancy remained unexplained in three patients (2.9%).

Conclusion

HER2 gene status remains highly conserved as breast cancers metastasise. However, discrepant results do occur because of interpretational difficulties and heterogeneity of HER2 amplification. Cytological specimens from distant metastases are well suited for HER2 fluorescence in situ hybridisation analysis.

Evaluation of the prognostic value of 2005 St Gallen risk categories for operated breast cancers in Hong Kong

Incorporating various new and conventional risk factors, the 2005 St Gallen risk categorization is a potentially useful prognostic tool for breast cancers. We conducted a retrospective study to evaluate its application in Hong Kong. Of the 902 included female breast cancers with median follow-up of 5.4 years, 7%, 63% and 30% patients were classified as low-, intermediate- and high-risk categories, respectively. Their corresponding 5-year distant disease-free survivals (DDFS) were 100%, 92% and 72%, respectively (p<0.00005). In the intermediate-risk category, node-positive patients had marginally inferior 5-year DDFS than node-negative patients (89% vs. 93%, p=0.0551). In the high-risk category, patients having HER2 overexpressed tumors and 1-3 positive nodes had significantly better DDFS than other patients with > or = 4 positive nodes (89% vs. 65%, p=0.0001). Overall, the 2005 St Gallen risk categorization had high prognostic value. However, the impact of HER2 overexpression might be affected by reproducibility of HER2 tests.

Capecitabine and Trastuzumab in Heavily Pretreated Metastatic Breast Cancer

Purpose

In human epidermal growth factor 2 (HER-2)–positive advanced breast cancer, taxanes or vinorelbine plus trastuzumab are among the most widely applied options in the first-line setting. We evaluated the efficacy and tolerability of capecitabine plus trastuzumab after anthracycline and docetaxel or vinorelbine failure and prior trastuzumab exposure.

Patients and Methods

Forty consecutive patients were included. Capecitabine was administered at a dose of 1,250 mg/m2bid for 14 consecutive days in 3-week cycles, with dose modifications if necessary. Trastuzumab was administered every 3 weeks. Time to progression (TTP) was defined as primary end point. Response was evaluated every 3 months using International Union Against Cancer criteria.

Results

TTP was a median of 8 months, and overall survival was 24 months. No significant difference was found for second-line and beyond second-line treatment. A complete response (CR) was observed in 2.5%, partial response (PR) in 17.5%, stable disease lasting at least 6 months (SD) in 50%, resulting in a clinical benefit rate (CR + PR + SD ≥ 6 months) of 70%. Diarrhea (5%) and hand-foot syndrome (15%) were the only treatment-related adverse events that occurred with grade 3 or 4 intensity. Three patients (7.5%) developed brain metastases while receiving therapy.

Conclusion

Capecitabine plus trastuzumab appears to be an effective and safe option in a heavily pretreated population. Therefore, a direct comparison of this regimen with capecitabine monotherapy in this setting is warranted.

Bénéfice et risques potentiels de l'association du trastuzumab à la chimiothérapie et à la radiothérapie dans le cancer du sein non métastatique

Trastuzumab (Herceptin) is the first humanised monoclonal antibody targeting the HER2 antigen in breast cancer. HER2 receptor has been individualised 20 years ago. During the past 10 years, trastuzumab administration has radically modified the prognosis of the patients that are treated for HER2 positive breast cancer. Its efficacy has been demonstrated in the metastatic and adjuvant settings. While, trastuzumab based-regimens became the standard of care in the treatment of HER2/neu positive breast cancer, the optimal combination (concurrently or sequentially) to chemotherapy and radiation therapy is still unknown. Indeed, while the concurrent administration of trastuzumab and anthracyclines is not recommended because of a high risk of cardiac toxicity, there is no published data on the best sequence of trastuzumab and radiation therapy administration, particularly when internal mammary chain is involved. The benefit/risk ratio of the concurrent and sequential administration of trastuzumab with chemotherapy and radiation therapy will be discussed in this review.

The biochemical, biological, and pathological kaleidoscope of cell surface substrates processed by matrix metalloproteinases

Matrix metalloproteinases (MMPs) constitute a family of more than 20 endopeptidases. Identification of specific matrix and non-matrix components as MMP substrates showed that, aside from their initial role as extracellular matrix modifiers, MMPs play significant roles in highly complex processes such as the regulation of cell behavior, cell-cell communication, and tumor progression. Thanks to the comprehensive examination of the expanded MMP action radius, the initial view of proteases acting in the soluble phase has evolved into a kaleidoscope of proteolytic reactions connected to the cell surface. Important classes of cell surface molecules include adhesion molecules, mediators of apoptosis, receptors, chemokines, cytokines, growth factors, proteases, intercellular junction proteins, and structural molecules. Proteolysis of cell surface proteins by MMPs may have extremely diverse biological implications, ranging from maturation and activation, to inactivation or degradation of substrates. In this way, modification of membrane-associated proteins by MMPs is crucial for communication between cells and the extracellular milieu, and determines cell fate and the integrity of tissues. Hence, insights into the processing of cell surface proteins by MMPs and the concomitant effects on physiological processes as well as on disease onset and evolution, leads the way to innovative therapeutic approaches for cancer, as well as degenerative and inflammatory diseases.

Novel therapeutic strategies combining antihormonal and biological targeted therapies in breast cancer: focus on clinical trials and perspectives

Several models have been proposed to explain the mechanisms of endocrine resistance including aberrant growth-signaling pathways, and have led to the rational design of studies combining hormonotherapy with signal transduction inhibitors (STI) in advanced breast cancer. This article reviews the current status of these clinical trials. Preliminary results from the randomized controlled trials are rather disappointing. The mTOR inhibitor temsirolimus and the farnesyl transferase inhibitor tipifarnib combined with letrozole did not show any benefit compared to letrozole alone. As neoadjuvant therapy, gefinitib did not enhance the response rate induced by anastrozole. Interesting results were obtained with exemestane combined to celecoxib but should be further explored with adequate cardiac monitoring. Trastuzumab combined with anastrozole was more effective than anastrozole in terms of response rate and progression-free survival but not survival. Several controlled trials as first- or second-line therapy have started recently and over the next few years we should learn whether this approach will provide significant gains in efficacy.

Adjuvant trastuzumab in the treatment of her-2-positive early breast cancer: a meta-analysis of published randomized trials

BACKGROUND

Breast cancer is the most common cancer in women in the U.S. and Western Europe. Amplification of the her-2/neu gene occurs in approximately 25% of invasive ductal carcinomas of the breast. The first HER-2/neu-targeted approach to reach the clinic was trastuzumab, a humanized monoclonal antibody directed against the extracellular domain of the HER-2/neu protein. Trastuzumab therapy prolongs the survival of patients with metastático HER-2/neu-overexpressing breast cancer when combined with chemotherapy and has recently been demonstrated to lead to dramatic improvements in disease-free survival when used in the adjuvant therapy setting in combination with or following chemotherapy. Here, we performed a meta-analysis of completed clinical trials of adjuvant trastuzumab in the adjuvant setting. Survival, recurrence, brain metastases, cardiotoxicity and directions for future research are discussed.

METHODS

A meta-analysis of randomized controlled trials (RCT) was performed comparing adjuvant trastuzumab treatment for HER2-positive early breast cancer (EBC) to observation. The MEDLINE, EMBASE, CANCERLIT and Cochrane Library databases, and abstracts published in the annual proceedings were systematically searched for evidence. Relevant reports were reviewed by two reviewers independently and the references from these reports were searched for additional trials, using guidelines set by QUOROM statement criteria.

RESULTS

Pooled results from that five randomized trials of adjuvant Trastuzumab showed a significant reduction of mortality (p < 0.00001), recurrence (p < 0.00001), metastases rates (p < 0.00001) and second tumors other than breast cancer (p = 0.007) as compared to no adjuvant Trastuzumab patients. There were more grade III or IV cardiac toxicity after trastuzumab (203/4555 = 4.5%) versus no trastuzumab (86/4562 = 1.8%). The likelihood of cardiac toxicity was 2.45-fold higher (95% CI 1.89 - 3.16) in trastuzumab arms, however that result was associated with heterogeneity. The likelihood of brain metastases was 1.82-fold higher (95% CI 1.16 - 2.85) in patients who received trastuzumab.

CONCLUSION

The results from this meta-analysis are sufficiently compelling to consider 1 year of adjuvant trastuzumab treatment for women with HER-2-positive EBC based on the risk: benefit ratio demonstrated in these studies. Adequate assessment of HER-2/neu status is critical, and careful cardiac monitoring is warranted because of cardiac toxicity. Clinical trials should be designed to answer unsolved questions.

Protein kinases as targets for cancer treatment

In various types of malignancies, conventional forms of therapy (surgery, radiation and chemotherapy) are often ineffective, as well as harmful. In the last few years, a convergence of scientific advances has enabled the identification of molecular targets and signaling pathways specific to cancer cells, resulting in therapies with enhanced selectivity and efficacy and reduced toxicity. Compound validation has relied on target validation first, although some of the most successful drugs often have effects outside of their postulated mechanism. Protein kinases represent such molecular targets; considerable research effort has been devoted to the development of targeted drugs that inhibit the action of pathogenic kinases, and clinical studies performed so far have validated the positive effects of kinase inhibitors for cancer treatment. In this review, the specificity, mechanism of action and antitumor activity of several new small-molecule inhibitors of tyrosine and serine/threonine kinases are discussed.

A multidisciplinary approach to the management of breast cancer, part 1: prevention and diagnosis

Breast cancer is the most common cancer among women in the United States, with an estimated 200,000 new cases diagnosed annually. A multidisciplinary focus that entails prevention, diagnosis, and treatment has led to significant strides in the reduction of breast cancer incidence and mortality. Additionally, breast cancer management has become increasingly complex, requiring comprehensive assessment and review of multiple issues that include the role of genetic testing, imaging and breast magnetic resonance imaging, surgical and reconstructive options, and a variety of new adjuvant therapies. It has become more evident that a multidisciplinary team approach that involves a spectrum of breast experts is necessary to provide optimal care to patients. This team includes medical oncologists, breast radiologists, breast pathologists, surgical breast specialists, radiation oncologists, geneticists, and primary care physicians. Furthermore, patient knowledge has increased use of the Internet, and more patients are seeking a multidisciplinary approach to treatment. This review considers information for health care professionals who will facilitate optimal patient care for women at increased risk for or presenting with a new diagnosis of breast cancer. The multidisciplinary team of authors, representing the different disciplines, has selected important state-of-the-art issues that arise in their daily practices for consideration, rather than summarizing what is already available in textbooks.