Reappraisal of the biological role of epidermal growth factor receptor in transitional cell carcinoma

Emerging concepts on drug resistance in bladder cancer: Implications for future strategies

The combination chemotherapies with methotrexate plus vinblastine, doxorubicin and cisplatin (MVAC or CMV regimens) or gemcitabine plus cisplatin represent the standard as first-line therapy for patients with metastatic urothelial cancer. In Europe, vinflunine is an option for second-line therapy for patients progressed during first-line or perioperative platinum-containing regimen. Alternative regimens containing taxanes and/or gemcitabine may be valuated case by case. Furthermore, carboplatin should be considered in patients unfit for cisplatin both in the first and second-line setting. Based on these findings, a better comprehension of the mechanisms underlying the development of drug resistance in patients with bladder cancer will represent a major step forward in optimizing patients' outcome. This article reviews the current knowledge of the mechanisms and emerging strategies to overcome resistance in patients with advanced urothelial cancer.

Epidermal growth factor enhances androgen receptor‑mediated bladder cancer progression and invasion via potentiation of AR transactivation

Androgen receptor (AR) plays a critical role in bladder cancer (BCa) development. Our early studies found AR knock-out mice (with few androgens and deleted AR) failed to develop BCa, yet 50% of castrated mice (with few androgens and existing AR) still developed BCa in an N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) carcinogen-induced BCa mouse model, suggesting the existing AR in BCa of castrated mice may still play important roles in promoting BCa development at the castration level of androgens. The mechanism underlying this and/or which factors potentiate AR function at the castration level of androgen remains unclear. Epidermal growth factor (EGF), a key player in BCa progression, has been demonstrated to be able to potentiate AR transactivation in prostate cancer. In the present study, we found that EGF could increase BCa cell growth, migration and invasion in the presence of AR under the low amount of androgen and EGF was able to potentiate AR transactivation through EGFR by activating PI3K/AKT and MAPK pathway at castration androgen level. The increased suppression effects by EGFR inhibitor of PD168393 on AR function after addition of anti-androgen, Casodex, further suggested AR might play a key role in the effects of EGF on BCa progression and metastasis. Collectively, our results indicate that EGF may be able to potentiate AR transactivation that leads to enhancing BCa progression, which may help us to develop a better therapeutic approach to treat BCa via targeting both EGF and AR signaling.

Effect of an epidermal growth factor receptor tyrosine kinase inhibitor on actin remodeling in an in vitro bladder cancer carcinogenesis model

Alteration of actin remodeling is a marker of malignant-associated field defect and a potential surrogate biomarker for chemoprevention trials. We tested erlotinib, a specific tyrosine kinase inhibitor of epidermal growth factor receptor (EGFR), on actin remodeling in a bladder carcinogenic model consisting of untransformed HUC-PC cells and transformed MC-T11 cells, both derived from the same normal human urothelial clone immortalized by SV40. Erlotinib had a selective growth inhibitory and actin remodeling effect on MC-T11 cells over HUC-PC cells, as examined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and immunofluorescence labeling with laser scan cytometer analysis, respectively. The IC(50) of untransformed HUC-PC cells was significantly higher than that of transformed MC-T11 cells (P < 0.05, t test). The actin remodeling effect was more prominent at lower dosage levels (1/8-1/4 of IC(50)), which was accompanied by an increased cell adhesion and decreased motility. At higher dosage levels (1/2 of IC(50)), erlotinib induced a decreased adhesion and anoikis (detachment-associated apoptosis). The transformed MC-T11, but not HUC-PC, showed a weak constitutive EGFR phosphorylation activity, which was inhibited by erlotinib in a dose-response manner. However, on epidermal growth factor stimulation, both cell lines showed a similar dose-response inhibitory effect on phosphorylated EGFR and mitogen-activated protein kinase (MAPK; P44/P42) activities, and MAPK inhibitor PD98059 showed no specific effect on erlotinib-induced actin remodeling, suggesting that pathways other than MAPK (P44/P42) may be responsible for erlotinib-induced actin remodeling. The findings provide evidence to support erlotinib-based bladder cancer chemoprevention and using actin remodeling as a marker for erlotinib-based intervention trials.

Prognostic value of EGF receptor and tumor cell proliferation in bladder cancer: therapeutic implications

Changes in growth factor receptor expression may confer a growth advantage on tumour cells. Epidermal growth factor-receptor (EGF-R) has been associated with the genesis of bladder tumours. We sought a link between EGF-R expression and MIB-1 cell proliferation and examined their prognostic value in the progression of bladder cancer. Fresh frozen samples from 113 transitional cell carcinomas (TCC) of the bladder and 10 healthy bladders were studied by immunohistochemistry, using monoclonal antibodies for EGF-R expression and MIB-1 for cell proliferation. Qualitative and quantitative immunostaining were analyzed in relation to time to progression and compared with clinical and pathologic parameters for prognostic significance in univariate and multivariate analysis (stepwise logistic regression). EGF-R stained more intensively in invasive tumours. Median nuclear over-expression of MIB-1 was 28%. Progression free survival rate estimates (log rank test) were significantly lower in patients EGF-R positive and with MIB-1 score above 28% (P < 0.0001, P < 0.0001, respectively). Multivariate analysis indicated that MIB-1 immunostaining was the most significant independent variable and EGF-R expression had no additional prognostic value over clinical stage and grade and cell proliferation. The MIB-1 proliferation index is a stronger predictor of bladder tumour progression than is EGF-R over-expression. This marker yield significant prognostic information in addition to stage and grade and may be of value for the clinical management of superficial and invasive bladder carcinomas. The pattern of EGF-R immunostaining and its association with tumour progression makes it a candidate for antigrowth factor therapy.

Epidermal growth factor receptor activation differentially regulates claudin expression and enhances transepithelial resistance in Madin-Darby canine kidney cells

Tight junctions (TJs) are the most apical cell-cell junctions, and claudins, the recently identified TJ proteins, are critical for maintaining cell-cell adhesion in epithelial cell sheets. Based on their in vivo distribution and the results of overexpression studies, certain claudins, including claudin-1 and -4, are postulated to increase, whereas other claudins, especially claudin-2, are postulated to decrease the overall transcellular resistance. The overall ratio among claudins expressed in a cell/tissue has been hypothesized to define the complexity of TJs. Disruption of the TJs contributes to various human diseases, and a correlation between reduction of TJ function and tumor dedifferentiation has been postulated. The epidermal growth factor (EGF) receptor (EGFR) is overexpressed in a wide spectrum of epithelial cancers, and its expression correlates with a more metastatic cancer phenotype. However, normal functioning of EGFR is essential for normal epithelial cell proliferation and differentiation. The role of EGFR-dependent signaling in the development and maintenance of epithelial TJ integrity has not been studied in detail. This study demonstrates that, in polarized Madin-Darby canine kidney II cells, EGF-induced EGFR activation significantly inhibited claudin-2 expression while simultaneously inducing cellular redistribution and increased expression of claudin-1, -3, and -4. Accompanying these EGF-induced changes in claudin expression was a 3-fold increase in transepithelial resistance, a functional measure of TJs. In contrast, there were no alterations in protein expression and/or intracellular localization of other TJ-related proteins (ZO-1 and occludin) or adherens junction-associated proteins (E-cadherin and beta-catenin), suggesting that EGF regulates TJ function through selective and differential regulation of claudins.

Mutation of cell cycle regulators and their impact on superficial bladder cancer

Early cytogenetic studies in bladder cancer identify regions of chromosomal gain or loss that can be candidate loci for oncogenes and tumor suppressor genes. Oncogenes with potential prognostic significance identified in bladder cancer the RAS family, epidermal growth factor receptor, ERBB-2, MDM2, and cyclin D1. The TP53 gene has been the most thoroughly characterized tumor suppressor gene in bladder cancer, with correlation of TP53 alterations with type of carcinogenic exposure, tumor stage and grade, as well as prognosis. Studies evaluating alterations of the retinoblastoma pathway have identified the retinoblastoma gene, RB, p161NK4A/CDKN2, and E2F-1 as tumor suppressor genes with potential prognostic significance in patients with bladder cancer. Better understanding of the genetic mechanisms underlying bladder tumor development and progression will allow better prevention, diagnosis, and treatment strategies.

Invasion of the bladder by transitional cell carcinoma: its relation to histologic grade and expression of p53, MIB-1, c-erb B-2, epidermal growth factor receptor, and bcl-2

BACKGROUND

Although pathologic level of invasion and histologic grade are helpful in predicting the clinical outcome of transitional cell carcinoma of the bladder, they also create uncertainty. Immunohistochemical staining for p53, MIB-1, epidermal growth factor receptor (EGFR), c-erb B-2, and bcl-2 have shown promise as prognostic factors when evaluated singly, although multivariate analyses that include histologic grade and the interactive effects of these markers have not been studied extensively. The authors have initiated a prospective study to determine whether these markers add prognostic information to that provided by level of invasion and histologic grade. This initial report details how these five markers relate to invasion of the bladder after controlling for the effects of histologic grade.

METHODS

The authors evaluated 229 transitional cell carcinomas in 229 patients using the World Health Organization grading schema and immunohistochemical staining with antigen retrieval for p53, MIB-1, EGFR, c-erb B-2, and bcl-2, and they related these markers to invasion after controlling for grade with a multivariate logistic regression model.

RESULTS

Although Grades 2 and 3 were the most important for predicting invasion, Grade 2 tumors that stained for either MIB-1 or p53 indicated a significantly greater probability of invasion than suggested by grade alone. bcl-2 and p53 had an opposing and interactive effect: when p53 was absent, the presence of bcl-2 implied less probability of invasion; but when both bcl-2 and p53 were present, the protective effect of bcl-2 was no longer observed. Although neither EGFR nor c-erb B-2 were as important as the other three markers in determining the risk of invasion, Grade 3 tumors that stained for one, and especially both, of these markers were less likely to be invasive.

CONCLUSIONS

These five markers sort into three interactive pairs: MIB-1 and p53, bcl-2 and p53, and EGFR and c-erb B-2. MIB-1 and p53 together imply a greater probability of invasion. bcl-2 appears to have a dual role, which depends on the presence of accumulated p53. Finally, EGFR and c-erb B-2 related closely to each other and in Grade 3 tumors imply a lesser probability of invasion. It is likely that combinations of markers, or correlations between markers and grades, will yield prognostic information that is more powerful than what histologic grade alone can provide.

Flow cytometric evaluation of transferrin receptor in transitional cell carcinoma

We evaluated flow cytometric (FCM) analysis of transferrin receptor (TFR) expression as a marker for the malignant potential in transitional cell carcinoma (TCC). TCCs from 55 patients were analyzed by FCM using an anti-TFR monoclonal antibody (CD71) and a TCC-specific monoclonal antibody (EH14), which recognizes most TCC cells irrespective of the grade. The cells were divided into subpopulations according to DNA ploidy determined simultaneously. TFR expression correlated well with the grade and the stage of the tumors. TFR expression of the aneuploid tumors was significantly higher than that of the euploid tumors in all subpopulations. EH14 expression did not correlate with the grade or the stage of the tumors. EH14 expression of the aneuploid tumors was significantly higher than that of the euploid tumors in the whole cell population but not in the subpopulations. In moderately differentiated tumors or in T1 tumors, TFR expression was higher in multiple or recurrent tumors than in simple tumors. The cell size or shape were not the primary reasons for the enhanced expression of TFR in the high-grade or the high-stage tumors; instead, overproduction of TFR may take place in these tumors. Clinically, many of the TCC tumors are grouped into G2 or T1 tumors, some of which will be invasive cancers. Quantitative analysis of TFR expression using FCM may be useful to predict the prognosis of these tumors.

A comparison of epidermal growth factor receptor levels and other prognostic parameters in non-small cell lung cancer

Epidermal growth factor receptor (EGFR) was measured using a competitive radioligand binding assay in membrane preparations from 74 primary human non-small cell lung cancer (NSCLC) tissues and 20 pathologically normal peripheral lung tissues. The mean EGFR level in tumours was 30.38 fmol/mg (+/-41.95 S.D.) of membrane protein (mg.p), significantly higher (P = 0.00016) than in normal tissues (mean, 10.26 +/- 10.02 fmol/mg.p). The mean EGFR concentration was also significantly higher in pathological stage IV tissue than in stages I (P = 0.049) and II (P = 0.040), and the mean EGFR concentration was significantly higher in cases with mediastinal involvement than in cases without it (P = 0.029). The mean EGFR level was higher in DNA aneuploid and multiploid cases than in DNA diploid cases, but there was no significant difference. No significant relationships were found to exist between receptor concentrations and pathological tumour size or histological type, or patient gender or age. From the above findings, a possible prognostic role for EGFR in primary NSCLC should be investigated.

Thyroid hormone upregulates gene expression, synthesis and release of pro-epidermal growth factor in adult rat kidney

Attempts were made to elucidate whether thyroid hormone upregulates renal pro-epidermal growth factor (pro-EGF) gene expression, biosynthesis and release in adult rats which were rendered hypothyroid. Predominantly pro-EGF was detected in renal cortex, whereas pro-EGF and its degraded species were found in urine. We demonstrated that T3 increased pro-EGF levels in renal cortex to 2.2 +/- 0.17, 2.37 +/- 0.19, 2.73 +/- 0.25, and 3.10 +/- 0.45 fold within day 1, 2, 4 and 8, respectively following treatment. Immunoreactive EGF, assessed by immunohistochemical methods, was confined in the distal convoluted tubule and thick ascending limb of Henle. T3 markedly enhanced the density of irEGF in these nephrons. T3 augmented the concentration of urinary irEGF to 2.1, 2.2, 2.8 and 3.6 fold within day 1, 2, 4 and 8 and the abundance of urine pro-EGF to 2.53 +/- 1.39, 3.8 +/- 0.70, 3.59 +/- 1.48 fold within day 1, 2, 4, respectively. Moreover, we employed reverse transcriptase/polymerase chain reaction method to analyze relative abundance of pro-EGF mRNA in kidneys of various thyroid states and found T3 markedly increased pro-EGF mRNA levels after treatment of 1, 2 and 4 days. These results indicated that thyroid hormone augmented the gene expression, biosynthesis and excretion of pro-EGF in adult rat kidney.

Near-diploid transitional cell carcinoma: a preliminary report

DNA ploidy analysis has been accepted as an important prognostic factor for patients with transitional cell carcinoma (TCC). However, there was few information dealing with the clinical relevance of slightly aberrant DNA content by flow cytometry (FCM). Here we present five cases of near-diploid (ND) tumours, with DNA index (DI) varying from 0.92 to 1.14, obtained from a prospective study of fifty-one cases (9.8%). The frequency of ND tumours showed a tendency to decrease with increasing tumour stage. Higher fraction of tumour proliferation, defined by Ki-67 index, showed a steady increment from 3.4 to 23.5% with occurrence of gross chromosomal changes. In contrast, the expression of epidermal growth factor receptor (EGFR) decreased from 48.3 to 35.3% for diploid (n = 29) through aneuploid (n = 17) tumours. All three ND bladder cancers had recurrence of one to three times with median follow-up of 36 months. The incidences of tumour recurrence (60%) and cancer death (20%) in ND tumours were intermediate between the aneuploid and diploid TCCs. But, flow DNA analysis of paraffin-embedded ND tumours revealed wide and symmetrical G0/G1 peak with DI varying from 5.6 to 13.0. Our limited experience suggests the necessity of special treatment for G0/G1 peaks having CV values greater than 5.5% from paraffin-embedded urothelial carcinomas.

An assessment of immunoreactive epidermal growth factor in urine of patients with urological diseases

To examine the excretion of urinary epidermal growth factor (EGF) in urological diseases and the relationship of EGF urine levels with transitional cell carcinoma (TCC), we measured the concentration of EGF by radioimmunoassay. The series comprised patients with active TCC (n = 52), others in tumor-free status (n = 29) and with non-neoplastic inflammatory diseases (n = 43), and normal controls (n = 50). Urinary EGF values were lower in patients with urological diseases of different etiologies than in normal controls (P < 0.005). Mean EGF levels of patients who had previous bladder tumor resection (n = 21) were not statistically different from normal controls (P = 0.2). For patients with active TCC, EGF urine levels showed a significant inverse relationship to increasing tumor grade (P = 0.02). In addition, subjects who had received nephrectomy for pelvic carcinoma (n = 8) showed significantly lower mean EGF values than those with intact kidneys (n = 21), irrespective of sex (P < 0.05). Immunostaining of EGF on non-neoplastic kidney (n = 9) revealed reactivity in the distal convoluted tubules and thick ascending limbs of Henle. Our results suggest that the kidney is the major source of urinary EGF. Its excretion in urine is decreased in both inflammatory and neoplastic diseases of the urinary tract. EGF may play an important part in the biological activity of TCC. Further study is indicated to investigate the monitoring of EGF urine levels as a marker of recurrence for EGF receptor-positive TCC.