Differential radiosensitisation by ZD1839 (Iressa), a highly selective epidermal growth factor receptor tyrosine kinase inhibitor in two related bladder cancer cell lines

Lapatinib, a Dual Inhibitor of Epidermal Growth Factor Receptor (EGFR) and HER-2, Enhances Radiosensitivity in Mouse Bladder Tumor Line-2 (MBT-2) Cells In Vitro and In Vivo

Background

The aim of this study was to evaluate the effect of lapatinib, a dual inhibitor of epidermal growth factor receptor (EGFR) and HER-2, on the radiosensitivity of murine bladder tumor line-2 (MBT-2) cells in vitro and in vivo.

Material/Methods

MBT-2 cells were pretreated with lapatinib at doses ranging from 200–1,000 nM for 30 min followed by radiation at doses ranging from 2.5–10 Gy for 30 min. A clonogenic assay (colony formation assay) assessed cell survival. Western blot measured phosphorylated epidermal growth factor receptor (p-EGFR), phosphorylated AKT (p-AKT), and phosphorylated HER-2 (p-HER2) and the apoptosis marker, PARP. The C3H/HeN mouse tumor xenograft model underwent subcutaneous injection of MBT-2 cells; mice were divided into four groups, treated with lapatinib (200 mg/kg), radiation (15 Gy), a combination of both, and with vehicle (control).

Results

Lapatinib pretreatment, combined with radiation, decreased MBT-2 cell survival, and suppressed radiation-activated levels of p-EGFR and p-HER-2. MBT-2 cells treated with a 10 Gy dose of radiation and 1000 nM of lapatinib showed combination index (CI) values of <1 indicating synergy. Increased expression of γ-H2AX, indicated increased apoptosis. In mice with tumor xenografts, a daily dose of lapatinib (200 mg/kg/day) for seven days combined with radiation on the fourth day suppressed tumor growth to a greater degree than radiation alone.

Conclusions

Lapatinib treatment enhanced the radiation sensitivity in an in vitro and in vivo murine bladder cancer model by decreasing radiation-mediated EGFR and HER-2 activation, and by causing DNA damage leading to cell apoptosis.

Synergistic Blockade of EGFR and HER2 by New-Generation EGFR Tyrosine Kinase Inhibitor Enhances Radiation Effect in Bladder Cancer Cells

Blockade of EGFR has been proved useful in enhancing the effect of radiotherapy, but the advantages of new-generation EGFR tyrosine kinase inhibitors (TKI) in radiosensitization are not well known. We used two human bladder cancer cells with wild-type EGFR to study the synergism between irradiation and afatinib (an EGFR/HER2 dual kinase inhibitor) or erlotinib (an EGFR kinase inhibitor). Here, we showed that afatinib has better radiosensitizing effect than erlotinib in increasing cancer cell killing, the percentage of apoptotic cells, and DNA damage. Afatinib is also superior to erlotinib in combining radiation to decrease tumor size, inhibit glucose metabolism, and enhance apoptotic proteins in vivo. Finally, erlotinib suppressed cell growth and induced more DNA damage in bladder cancer cells transfected with HER2 shRNA, but not in control vector-treated cells. In conclusion, concomitant blockade of radiation-activated EGFR and HER2 signaling by a new-generation EGFR TKI better inhibits the growth of bladder cancer cells both in vitro and in vivo. The absence of radiosensitization by EGFR inhibition alone and the greater radiosensitizing effect of EGFR inhibitor in HER2 knocked down cells suggest the synergism between HER2 and EGFR in determining radiosensitivity. The regained radiosensitizing activity of erlotinib implies that with proper HER2 inhibition, EGFR tyrosine kinase is still a potential target to enhance radiotherapy effect in these seemingly unresponsive bladder cancer cells.

Evaluation of the antitumor activity of dacomitinib in models of human bladder cancer

Members of the human epidermal growth factor receptor (HER) family play a significant role in bladder cancer progression and may underlie the development of chemotherapy resistance. Dacomitinib is an irreversible tyrosine kinase inhibitor with structural specificity for the catalytic domains of epidermal growth factor receptor (EGFR), HER2 and HER4 that has exhibited vigorous efficacy against other solid tumors. We evaluated the antitumor activity of dacomitinib in human bladder cancer cell lines expressing varying levels of HER family receptors. These cell lines also were established as bladder cancer xenografts in nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice to assess dacomitinib activity in vivo. Significant cytotoxic and cytostatic effects were noted in cells expressing elevated levels of the dacomitinib target receptors with apoptosis and cell cycle arrest being the predominant mechanisms of antitumor activity. Cells expressing lower levels of HER receptors were much less sensitive to dacomitinib. Interestingly, dacomitinib was more active than either trastuzumab or cetuximab in vitro, and exhibited increased growth inhibition of bladder tumor xenografts compared with lapatinib. Pharmacodynamic effects of dacomitinib included decreased E-cadherin (E-cad) expression, reduction of EGFR and extracellular signal-regulated kinase (ERK) phosphorylation and reduced mitotic count. Dacomitinib also inhibited tumor growth in a chemotherapy-resistant xenograft and, when combined with chemotherapy in a sensitive xenograft, exhibited superior antitumor effects compared with individual treatments. Evaluation in xenograft-bearing mice revealed that this combination was broadly feasible and well tolerated. In conclusion, dacomitinib exhibited pronounced activity both as a single agent and when combined with chemotherapy in human bladder cancer models. Further investigation of dacomitinib in the preclinical and clinical trial settings is being pursued.

Targeting epidermal growth factor receptor/human epidermal growth factor receptor 2 signalling pathway by a dual receptor tyrosine kinase inhibitor afatinib for radiosensitisation in murine bladder carcinoma

Given the promising control of bladder cancer achieved by combined chemotherapy/radiotherapy with selective transurethral resection, obstacles remain to the treatment of unresectable bladder cancer. The aim of this study was to determine whether targeting epidermal growth factor receptor (EGFR)/human epidermal growth factor receptor 2 (HER2) can radiosensitise a murine bladder tumour (MBT-2) cell line. Cell survival, expression of signal proteins and cell cycle changes in MBT-2 cells treated in vitro and in vivo with afatinib, an irreversible EGFR/HER2 inhibitor, plus radiotherapy were investigated by colony formation assay, Western blot assay and flow cytometry, respectively. Ectopic xenografts were established by subcutaneous injection of MBT-2 cells in C3H/HeN mice. Mice were randomised into 4 groups to receive afatinib (10mg/kg/day on day 1-7) and/or radiotherapy (15Gy on day 4). Positron emission tomography (PET) on day 8 was used to evaluate the early treatment response. Afatinib (200-1000nM) increased cell killing by radiation (0-10Gy). Pre-treatment of irradiated cells with afatinib inhibited radiation-activated HER2 and EGFR phosphorylation. As compared to either treatment alone, the combination increased the level of the cleavage form of poly (ADP-ribose) polymerase, the expression of phospho-γH2AX and the percentage of cells in subG1 phase (indicating enhanced induction of apoptosis), and decreased tumour metabolism and inhibited tumour growth by 64%. Afatinib has therapeutic value as a radiosensitiser of murine bladder cancer cells. The synergism between afatinib and radiation likely enhances DNA damage, leading to increased cell apoptosis.

Discussion on the influence of HER2 status on the clinical outcome of bladder cancer continues

Evaluation of: Bolenz C, Shariat SF, Karakiewicz PI et al. Human epidermal growth factor receptor 2 expression status provides independent prognostic information in patients with urothelial carcinoma of the urinary bladder. BJUI 106, 1216-1222 (2010). The article under evaluation by Bolenz et al. reports on an association between human EGF receptor 2 (HER2) overexpression and aggressive urothelial carcinoma of the urinary bladder: more lymphovascular invasion, higher risk of recurrence and higher disease-specific mortality. These results add to the controversy regarding HER2 status and clinical outcome that is currently known. First, a consensus for the best technique and cut-off is needed. Only then can the relationship between HER2 overexpression and clinical outcome be investigated without current limitations. Although there are already trials ongoing on targeted therapy in bladder cancer, this should be viewed with caution, as patient selection is based on inconsistent definitions of HER2 overexpression. Selection of patients who might benefit from targeted therapy can only be carried out after consensus has been reached.

Urothelial carcinomas: a focus on human epidermal receptors signaling

Bladder cancer is a common malignancy and a frequent cause of cancer-related death worldwide. The benefit from current chemotherapy has reached a relative plateau, thus identification of molecular targets for better therapy is a high priority. Human epidermal receptors constitute a family of receptor tyrosine kinases, which appear to be implicated in cellular transformation and can be over-expressed in a variety of solid tumors. There is preclinical and clinical data suggesting the role of EGFR and HER2 in urothelial carcinoma, thus prompting clinical investigation of anti-HER targeted therapies attempting to inhibit HER-induced tumor-promoting signaling. There is significant and dynamic cross-talk between HER and other signaling pathways and the identification of the structure and function of such cellular networks in the setting of urothelial cancer is a complex and difficult task. The development of prognostic and predictive biomarkers is needed in order to improve the personalized management of patients with urothelial cancer.

EGFR expression in urothelial carcinoma of the upper urinary tract is associated with disease progression and metaplastic morphology

EGFR represents a promising therapeutic target in urothelial cancer (UC). Our study aimed to investigate the clinicopathological significance of EGFR in upper urinary tract UC. EGFR was immunohistochemically assessed (EGFR pharmDX kit(TM)) in 268 consecutive tumours using a tissue microarray technique and correlated with other histopathological parameters as well as patient outcome. EGFR immunoreactivity was observed in 140/253 (55%) evaluable UCs and was associated with high tumour stage (47% pTa/pT1 vs 66% pT2-pT4; p=0.003) and high tumour grade (45% low grade vs 67% high grade; p<0.001). In addition, EGFR expression was associated with metaplastic squamous and/or glandular differentiation (p<0.001). EGFR staining intensity was 1+ in 49%, 2+ in 31%, and 3+ in 20% of cases. EGFR 3+ staining intensity was associated with the occurrence of metastatic disease by univariate analysis (p=0.016). Multivariate analysis, however, proved only pT stage >1 (p<0.001) and high tumour grade (p<0.001) to be independent predictors of patient outcome. In conclusion, EGFR was significantly associated with advanced disease and metaplastic squamous and/or glandular differentiation. Since UCs with metaplastic morphology have been shown to be more resistant to conventional radiotherapy or chemotherapy, the strikingly strong EGFR expression in these tumours may offer a new perspective for affected patients.

Mutations within the kinase domain and truncations of the epidermal growth factor receptor are rare events in bladder cancer: implications for therapy

PURPOSE

It has previously been reported that the patient response to gefitinib depends on the presence of mutations within the kinase domain of epidermal growth factor receptor (EGFR) or the expression of its truncated form, EGFR variant III (EGFRvIII). The focus of this study was to determine if these alterations are present within the tyrosine kinase and ligand-binding domain of EGFR in urothelial carcinoma.

EXPERIMENTAL DESIGN

The kinase domain found within exons 18 to 21 of the EGFR from 11 bladder cancer cell lines and 75 patient tumors were subjected to automated sequencing. EGFRvIII expression was determined by immunohistochemistry using a urothelial carcinoma tissue microarray, and its expression was subsequently verified by reverse transcription PCR, real-time PCR, and Western blot analysis, using an EGFRvIII-transfected glioblastoma cell line and glioblastoma tumors as positive controls.

RESULTS

Our analysis failed to detect mutations within the tyrosine kinase domain of EGFR in the 11 cell lines and 75 patients tested. The initial analysis of EGFRvIII expression by immunohistochemistry revealed that at least 50% of the patient tumors expressed EGFRvIII in a urothelial carcinoma tissue microarray. Conflicting reports exist, however, regarding the extent of EGFRvIII expression in tissues owing to the specificity of the antibodies and the methodologies used. Therefore, we sought to validate this observation by reverse transcription PCR, real-time PCR, and Western blot analysis. In these assays, none of the samples were positive for EGFRvIII except for control transfectants and glioblastomas.

CONCLUSIONS

When our results are taken together, we conclude that alterations within the tyrosine kinase domain and expression of EGFRvIII are rare events in bladder cancer. The present study has clinical implications in selecting tyrosine kinase inhibitors for the therapy of urothelial carcinoma.

Epidermal Growth Factor Receptor Status and the Response of Bladder Carcinoma Cells to Erlotinib

PURPOSE

We established the frequency of mutation of the epidermal growth factor receptor in bladder cancer and determined whether the activation status of epidermal growth factor receptor confers sensitivity to erlotinib.

MATERIALS AND METHODS

The identification of mutations in the kinase domain (exons 18-21) of epidermal growth factor receptor was performed using single strand conformation polymorphism. The action of erlotinib was established within a bladder carcinoma cell panel using clonogenic assays and Western blot analysis.

RESULTS

In 112 invasive bladder tumors a total of 6 mutations in 4 patients (3.6%) were identified in exon 21. Erlotinib demonstrated concentration dependent inhibition of growth where three cell lines showed high and 2 showed low sensitivity to the drug. Erlotinib inhibited activation of epidermal growth factor receptor, mitogen activated protein kinase, Akt and STAT3. However, the activation status of Akt was maintained in cell lines that were insensitive to the inhibitory action of erlotinib and were characterized as having undergone epithelial-to-mesenchymal transition.

CONCLUSIONS

Although mutations in the coding region of epidermal growth factor receptor are rare in invasive bladder tumors, differential sensitivity to erlotinib was recorded within a panel of cell lines. Maintenance of the phosphorylation status of Akt in the presence of erlotinib along with epithelial-to-mesenchymal transition correlates with insensitivity to growth inhibition in bladder carcinoma cell lines. Even in the absence of epidermal growth factor receptor mutations erlotinib shows potential as a therapeutic agent for the treatment of bladder cancer.

Combination treatment with ionising radiation and gefitinib ('Iressa', ZD1839), an epidermal growth factor receptor (EGFR) inhibitor, significantly inhibits bladder cancer cell growth in vitro and in vivo

PURPOSE

External beam radiotherapy (EBRT) is the principal bladder-preserving monotherapy for muscle-invasive bladder cancer. Seventy percent of muscle-invasive bladder cancers express epidermal growth factor receptor (EGFR), which is associated with poor prognosis. Ionising radiation (IR) stimulates EGFR causing activation of cytoprotective signalling cascades and thus may be an underlying cause of radioresistance in bladder tumours.

MATERIALS AND METHODS

We assessed the ability of IR to activate EGFR in bladder cancer cells and the effect of the anti-EGFR therapy, gefitinib on potential radiation-induced activation. Subsequently we assessed the effect of IR on signalling pathways downstream of EGFR. Finally we assessed the activity of gefitinib as a monotherapy, and in combination with IR, using clonogenic assay in vitro, and a murine model in vivo.

RESULTS

IR activated EGFR and gefitinib partially inhibited this activation. Radiation-induced activation of EGFR activated the MAPK and Akt pathways. Gefitinib partially inhibited activation of the MAPK pathway but not the Akt pathway. Treatment with combined gefitinib and IR significantly inhibited bladder cancer cell colony formation more than treatment with gefitinib alone (p = 0.001-0.03). J82 xenograft tumours treated with combined gefitinib and IR showed significantly greater growth inhibition than tumours treated with IR alone (p = 0.04).

CONCLUSIONS

Combining gefitinib and IR results in significantly greater inhibition of invasive bladder cancer cell colony formation in vitro and significantly greater tumour growth inhibition in vivo. Given the high frequency of EGFR expression by bladder tumours and the low toxicity of gefitinib there is justification to translate this work into a clinical trial.

EGFR-targeted anti-cancer drugs in radiotherapy: preclinical evaluation of mechanisms

Preclinical and clinical results indicate that the EGFR can mediate radioresistance in different solid human tumours. Combination of radiotherapy and EGFR inhibitors can improve local tumour control compared to irradiation alone and has been introduced into clinical radiotherapy practice. So far several mechanisms have been identified in preclinical studies to contribute to improved local tumour control after radiation combined with EGFR inhibitors. These include direct kill of cancer stem cells by EGFR inhibitors, cellular radiosensitization through modified signal transduction, inhibition of repair of DNA damage, reduced repopulation and improved reoxygenation during fractionated radiotherapy. Effects and mechanisms may differ for different classes of EGFR inhibitors, for different tumours and for normal tissues. The mechanisms underlying this heterogeneity are currently poorly understood, and predictive assays are not available yet. Importantly, mechanisms and predictors for the combined effects of radiation with EGFR inhibitors appear to be considerably different to those for application of EGFR inhibitors alone or in combination with chemotherapy. Therefore to further evaluate the efficacy and mechanisms of EGFR-inhibition in combined treatments, radiotherapy-specific preclinical research strategies, which include in vivo experiments using local tumour control as an endpoint, as well as animal studies on normal tissue toxicity are needed.

High EGFR expression predicts poor prognosis in patients with squamous cell carcinoma of the oral cavity and oropharynx: A TMA-based immunohistochemical analysis

This retrospective study was designed to investigate the prognostic significance of EGFR overexpression in human oral squamous cell carcinoma on a long-term follow-up. EGFR expression was examined immunohistochemically on a tissue microarray (TMA) of paraffin embedded tissue specimens from 109 patients who underwent surgical treatment for squamous cell carcinoma of the oral cavity and oropharynx in the period between 1980 and 1997. High EGFR expression was found in 80 (73.42%) of the tumour samples. Kaplan-Meier curves showed that EGFR overexpression was significantly related to decreased overall survival (p=0.05). Multivariate analysis showed that EGFR overexpression is an independent prognostic marker in these patients (p=0.02, RR 3.6). These results confirm that EGFR overexpression is an independent prognostic marker in patients with squamous cell carcinoma of the oral cavity and oropharynx. The EGFR antigen represents an attractive target for targeted therapies with monoclonal antibodies or specific tyrosine-kinase inhibitors in these patients.

Epidermal Growth Factor Receptor Status Predicts Local Response to Radical Radiotherapy in Muscle-invasive Bladder Cancer

AIMS

Epidermal growth factor receptor (EGFR) is expressed by over 70% of muscle-invasive bladder tumours and is associated with diminished overall survival. In model tumour systems, ionising radiation has been shown to activate EGFR, leading to cellular proliferation and is therefore a possible mechanism of underlying radioresistance. We carried out an immunohistochemical study relating the clinical outcome of patients receiving radical radiotherapy for muscle-invasive bladder cancer to tumour EGFR status.

MATERIALS AND METHODS

Archived paraffin-embedded tumours from 110 consecutive patients receiving radical radiotherapy for muscle-invasive bladder cancer between 1991 and 1997 were immunohistochemically stained for EGFR. Data were collected concerning the tumour stage and grade, the presence of ureteric obstruction, the response to radiotherapy at 3 months, local recurrence rates, metastatic spread and survival. Multivariate analysis of potential independent prognostic factors of impaired bladder cancer-specific survival was carried out using Cox's regression.

RESULTS

Of 110 tumours, 79 (72%) stained positively for EGFR. Of 87 patients undergoing the 3-month check cystoscopy, 60 (69%) had a positive response to radiotherapy. A positive response to radiotherapy correlated significantly with a negative EGFR status (chi(2) test, P = 0.05). Kaplan-Meier survival analysis revealed a trend towards improved bladder cancer-specific survival in EGFR-negative patients (Log-rank, P = 0.10). A lack of response to radiotherapy at 3 months, local recurrence, metastatic spread and the presence of ureteric obstruction were all independent prognostic factors for diminished bladder cancer-specific survival (Cox's regression: P = 0.009, P = 0.001, P = 0.04 and P = 0.005, respectively).

CONCLUSIONS

EGFR status predicts the local response to radiotherapy but does not provide prognostic utility in relation to overall or bladder cancer-specific survival. As EGFR status seems to be linked to the initial response to radiotherapy, its inhibition may be a means of enhancing the radio-responsiveness of these poor prognosis tumours. Colquhoun, A. J.

Evaluation of gefitinib for treatment of refractory solid tumors and central nervous system malignancies in pediatric patients

Gefitinib (ZD1839, Iressa), a member of the 4-anilinoquinazoline class of compounds, has the chemical name 4-quinazolinamine, N-(3-chloro-4-flurophenyl)-7-methoxy-6-[3-(4-morpholinyl)propoxy]. Gefitinib often is referred to as a "specific" or "selective" inhibitor of epidermal growth factor receptor (EGFR). EGFR expression has been noted in neuroblastoma and rhabdomyosarcoma cell lines and in tumor specimens from children with Wilms tumor, osteosarcoma, and glioma. Thus, gefitinib, the first marketed EGFR tyrosine kinase inhibitor, was chosen for study in children with refractory solid tumors and central nervous system (CNS) malignancies. This review discusses findings from 3 clinical trials of gefitinib in children with refractory solid tumors and CNS malignancies, focusing on the clinical pharmacology of the compound. To date, gefitinib has been studied in children as a single agent and in combination with irinotecan. Overall, the compound has been well tolerated in children and has a safety profile similar to that observed in adults. The clinical pharmacokinetics of gefitinib in children are similar to those observed in adults. Finally, the future for the use of gefitinib in pediatrics is similar to that of other molecularly targeted agents and awaits definition of tumors and patient populations in which it will be most advantageous.

Radiotherapy in the management of common genitourinary malignancies

A continued role for radiation therapy in the multidisciplinary management of genitourinary malignancies seems certain. Treatment outcomes continue to improve, accompanied by diminishing rates of toxicity. With continued technologic advances in the delivery of radiation, including the use of adaptive radiotherapy, the discovery and application of novel treatment agents, and the combined efforts of urologists, medical oncologists, and radiation oncologists, patients who have genitourinary malignancies have an excellent chance of cure.

ZD6474, an inhibitor of VEGFR and EGFR tyrosine kinase activity in combination with radiotherapy

Radiation enhances both epithelial growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) expression, which are a part of key pathways for tumor progression. Some tumors may not respond well to EGFR inhibitors alone or may develop resistance to EGFR inhibitors. Therefore, drug therapy targeted to VEGF receptors and EGFRs, when combined with radiotherapy (RT), may improve tumor control and provide wider applicability. This article focuses on ZD6474, an inhibitor of EGFR and VEGF receptor signaling in combination with RT. We discuss preclinical and clinical studies with RT and inhibitors of VEGF or EGFR signaling first. We then address issues associated with ZD6474 pharmacokinetic dosing, and scheduling when combined with RT. We also discuss ZD6474 in the context of anti-EGFR therapy resistance. Dual inhibition of EGFR and VEGF receptor signaling pathways shows promise in enhancing RT efficacy.

Clinical applications for targeted therapy in bladder cancer

The tremendous amount of data accumulated through genomics, proteomics, and metabolomic technologies has not led to a definitive understanding of the mechanisms underlying cancer. The challenge remains as to how to integrate all of the relevant knowledge and data in a systematic manner so that researchers can gain the knowledge needed to devise the best therapeutic and diagnostic strategies. Human transitional cell carcinoma of the bladder is genetically heterogeneous, and it is surrounded by a complex tissue microenvironment involving vasculature, stromal cells, and connective tissue. One of the most challenging problems facing cancer researchers is the lack of correlation between in vitro cell lines and animal tumor models and human in vivo tumors. A few promising approaches are being devised that will help address this issue in the coming years. One such approach is the measurements of molecular levels of receptors, ligands, pathways components, and so on, directly in human tumors through in vivo imaging, or through proteomic profiling, as it has been proposed as standard protocol for cancer diagnostics and therapeutics.