Autocrine stimulation by insulin-like growth factor I is involved in the growth, tumorigenicity and chemoresistance of human esophageal carcinoma cells

IGF-1-mediated FOXC1 overexpression induces stem-like properties through upregulating CBX7 and IGF-1R in esophageal squamous cell carcinoma

Substantial evidence attests to the pivotal role of cancer stem cells (CSC) in both tumorigenesis and drug resistance. A member of the forkhead box (FOX) family, FOXC1, assumes significance in embryonic development and organogenesis. Furthermore, FOXC1 functions as an overexpressed transcription factor in various tumors, fostering proliferation, enhancing migratory capabilities, and promoting drug resistance, while maintaining stem-cell-like properties. Despite these implications, scant attention has been devoted to its role in esophageal squamous cell carcinoma. Our investigation revealed a pronounced upregulation of FOXC1 expression in ESCC, correlating with a poor prognosis. The downregulation of FOXC1 demonstrated inhibitory effects on ESCC tumorigenesis, proliferation, and tolerance to chemotherapeutic agents, concurrently reducing the levels of stemness-related markers CD133 and CD44. Further studies validated that FOXC1 induces ESCC stemness by transactivating CBX7 and IGF-1R. Additionally, IGF-1 activated the PI3K/AKT/NF-κB and MEK/ERK/NF-κB pathways through its binding to IGF-1R, thereby augmenting FOXC1 expression. Conversely, suppressing FOXC1 impeded ESCC stemness induced by IGF-1. The presence of a positive feedback loop, denoted by IGF-1-FOXC1-IGF-1R, suggests the potential of FOXC1 as a prognostic biomarker for ESCC. Taken together, targeting the IGF-1-FOXC1-IGF-1R axis emerges as a promising approach for anti-CSC therapy in ESCC.

Serological levels of IGF-1 and IGFBP-3 in patients with Barrett's esophagus and esophageal adenocarcinoma: Longitudinal study

BACKGROUND

Barrett's esophagus (BE) is an entity with a known histological progression to malignancy. The insulin-like growth factor (IGF) system is involved in the carcinogenesis through obesity-related mechanisms that include IGF and it has been associated with several types of cancer.

OBJECTIVES

To evaluate the serological levels of IGF-1 and IGFBP-3 in patients with BE and esophageal adenocarcinoma.

PATIENTS AND METHODS

Prospective study of patients with BE and esophageal adenocarcinoma who underwent upper endoscopy between September 2012 and December 2015. A baseline determination of IGF-1 and IGFBP-3 was performed. We included a control group of patients without BE.

RESULTS

One hundred sixteen patients were included: 36 controls, 62 with BE (42 without dysplasia and 20 with dysplasia) and 18 with adenocarcinoma. IGF-1 and IGF-1/IGFBP-3 molar ratio showed a progression to high levels in BE and adenocarcinoma than in controls (IGF-1: 135.55±66.07ng/ml, 148.33±81.5ng/ml, 108.19±46.69ng/ml, respectively; P=.049) (molar ratio: 0.23±0.91, 0.29±0.11, 0.19±0.06, respectively; P=.001), without differences between the histological types of BE. Fifty-four out of the 65 patients with BE were followed up (median of 58.50 months, range 12-113) and 11 of them (20.4%) presented progression to low-grade dysplasia (n=8) or high-grade dysplasia/adenocarcinoma (n=3), without differences in the IGF system compared with patients without progression.

CONCLUSIONS

Patients with BE and esophageal adenocarcinoma have changes in the IGF system although the serological levels of IGF-1 and IGFBP-3 do not correlate with histological progression of BE.

Advances in Drug Resistance of Esophageal Cancer: From the Perspective of Tumor Microenvironment

Drug resistance represents the major obstacle to get the maximum therapeutic benefit for patients with esophageal cancer since numerous patients are inherently or adaptively resistant to therapeutic agents. Notably, increasing evidence has demonstrated that drug resistance is closely related to the crosstalk between tumor cells and the tumor microenvironment (TME). TME is a dynamic and ever-changing complex biological network whose diverse cellular and non-cellular components influence hallmarks and fates of tumor cells from the outside, and this is responsible for the development of resistance to conventional therapeutic agents to some extent. Indeed, the formation of drug resistance in esophageal cancer should be considered as a multifactorial process involving not only cancer cells themselves but cancer stem cells, tumor-associated stromal cells, hypoxia, soluble factors, extracellular vesicles, etc. Accordingly, combination therapy targeting tumor cells and tumor-favorable microenvironment represents a promising strategy to address drug resistance and get better therapeutic responses for patients with esophageal cancer. In this review, we mainly focus our discussion on molecular mechanisms that underlie the role of TME in drug resistance in esophageal cancer. We also discuss the opportunities and challenges for therapeutically targeting tumor-favorable microenvironment, such as membrane proteins, pivotal signaling pathways, and cytokines, to attenuate drug resistance in esophageal cancer.

Epigenetic silencing of IGFBPL1 promotes esophageal cancer growth by activating PI3K-AKT signaling

Background

There are seven insulin-like growth factor binding proteins (IGFBPs) that bind insulin-like growth factors (IGFs). IGFBP like protein1 (IGFBPL1) is a new member of this family. The function and mechanism of IGFBPL1 in esophageal cancer remains to be elucidated.

Methods

Eight esophageal cancer cell lines, 114 cases of esophageal dysplasia, and 501 cases of primary esophageal cancer samples were examined in this study. Methylation-specific polymerase chain reaction (MSP), immunohistochemistry, Western blot, flow cytometry, RNA interference assay, and xenograft mouse models were employed.

Results

The expression of IGFBPL1was lost and complete methylation was found in KYSE150 and KYSE410 cells. Reduced expression and partial methylation of IGFBPL1 was found in Bic1, KYSE140, KYSE450, KYSE520, and COLO680N cells. High expression and unmethylation was detected in KYSE510 cells. Restoration of IGFBPL1 expression was found in KYSE150 and KYSE410 cells and the expression of IGFBPL1 was increased in Bic1, KYSE140, KYSE450, KYSE520, and COLO680N cells, after 5-AZA-2′-deoxycytidine treatment. IGFBPL1 was methylated in 47.3% (53/114) of esophageal dysplasia and 49.1% (246/501) of human primary esophageal squamous cell carcinoma (ESCC). Methylation of IGFBPL1 was significantly associated with TNM stage (p = 0.012), and tumor size (p = 0.009). IGFBPL1 inhibited esophageal cancer cell clonal formation and proliferation and induced cell apoptosis and G1/S phase arrest. Further study found that IGFBPL1 is involved in PI3K-AKT signaling and IGFBPL1 suppressed human ESCC xenografts growth in mice.

Conclusion

IGFBPL1 suppresses esophageal cancer cell growth by inhibiting PI3K-AKT signaling in vitro and in vivo. IGFBPL1 is a novel tumor suppressor in human esophageal cancer.

Characterization of Iron Core⁻Gold Shell Nanoparticles for Anti-Cancer Treatments: Chemical and Structural Transformations During Storage and Use

Finding a cancer-selective drug that avoids damaging healthy cells and organs is a holy grail in medical research. In our previous studies, gold-coated iron (Fe@Au) nanoparticles showed cancer selective anti-cancer properties in vitro and in vivo but were found to gradually lose that activity with storage or "ageing." To determine the reasons for this diminished anti-cancer activity, we examined Fe@Au nanoparticles at different preparation and storage stages by means of transmission electron microscopy combined with and energy-dispersive X-ray spectroscopy, along with X-ray diffraction analysis and cell viability tests. We found that dried and reconstituted Fe@Au nanoparticles, or Fe@Au nanoparticles within cells, decompose into irregular fragments of γ-F₂O₃ and agglomerated gold clumps. These changes cause the loss of the particles' anti-cancer effects. However, we identified that the anti-cancer properties of Fe@Au nanoparticles can be well preserved under argon or, better still, liquid nitrogen storage for six months and at least one year, respectively.

Expression, regulation and targeting of receptor tyrosine kinases in esophageal squamous cell carcinoma

Esophageal cancer is one of the most common types of cancer, which is a leading cause of cancer-related death worldwide. Based on histological behavior, it is mainly of two types (i) Esophageal squamous cell carcinoma (ESCC), and (ii) esophageal adenocarcinoma (EAD or EAC). In astronomically immense majority of malignancies, receptor tyrosine kinases (RTKs) have been kenned to play a consequential role in cellular proliferation, migration, and metastasis of the cells. The post-translational modifications (PTMs) including phosphorylation of tyrosine (pY) residue of the tyrosine kinase (TK) domain have been exploited for treatment in different malignancies. Lung cancer where pY residues of EGFR have been exploited for treatment purpose in lung adenocarcinoma patients, but we do not have such kind of felicitously studied and catalogued data in ESCC patients. Thus, the goal of this review is to summarize the studies carried out on ESCC to explore the role of RTKs, tyrosine kinase inhibitors, and their pertinence and consequentiality for the treatment of ESCC patients.

IGFBP2 modulates the chemoresistant phenotype in esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) patients commonly present with advanced stage disease and demonstrate resistance to therapy, with response rates below 40%. Understanding the molecular mechanisms of resistance is crucial for improvement of clinical outcomes. IGFBP2 is a member of the IGFBP family of proteins that has been reported to modulate both IGF and integrin signaling and is a mediator of cell growth, invasion and resistance in other tumor types. In this study, high IGFBP2 expression was observed in a subset of primary EACs and was found to be significantly higher in patients with shorter disease-free intervals as well as in treatment-resistant EACs as compared to chemonaive EACs. Modulation of IGFBP2 expression in EAC cell lines promoted cell proliferation, migration and invasion, implicating a role in the metastatic potential of these cells. Additionally, knockdown of IGFBP2 sensitized EAC cells to cisplatin in a serum-dependent manner. Further in vitro exploration into this chemosensitization implicated both the AKT and ERK pathways. Silencing of IGFBP2 enhanced IGF1-induced immediate activation of AKT and reduced cisplatin-induced ERK activation. Addition of MEK1/2 (selumetinib or trametinib) or AKT (AKT Inhibitor VIII) inhibitors enhanced siIGFBP2-induced sensitization of EAC cells to cisplatin. These results suggest that targeted inhibition of IGFBP2 alone or together with either the MAPK or PI3K/AKT signaling pathway in IGFBP2-overexpressing EAC tumors may be an effective approach for sensitizing resistant EACs to standard neoadjuvant chemotherapy.

Risk factors for Barrett's esophagus

Barrett's esophagus (BE) is a well-recognized precursor of esophageal adenocarcinoma (EAC) and is defined as ≥1 cm segment of salmon-colored mucosa extending above the gastroesophageal junction into the tubular esophagus with biopsy confirmation of metaplastic replacement of the normal squamous epithelium by intestinal-type columnar epithelium. The incidence of both BE and EAC has been increasing over the past few decades. As a result, preventing the development of BE by identifying and understanding its modifiable and non-modifiable risk factors may help reduce the incidence of EAC. Over the recent past, a tremendous amount of progress has been made towards improving our knowledge of risk factors and pathogenesis of BE. This article reviews the evidence for the various risk factors for developing BE.

Role of insulin-like growth factor-binding proteins in the pathophysiology and tumorigenesis of gastroesophageal cancers

The insulin family of proteins include insulin-like growth factor binding proteins (IGFBPs) that are classified into two groups based on their differential affinities to IGFs: IGF high-affinity binding proteins (IGFBP1-6) and IGF low-affinity IGFBP-related proteins (IGFBP-rP1-10). IGFBPs interact with many proteins, including their canonical ligands insulin-like growth factor 1 (IGF-I) and IGF-II. Together with insulin-like growth factor 1 (IGF1) receptor (IGF1R), IGF2R, and ligands (IGF1 and IGF2), IGFBPs participate in a complex signaling axis called IGF-IGFR-IGFBP. Numerous studies have demonstrated that the IGF-IGFR-IGFBP axis is relevant in gastrointestinal (GI) and other cancers. The presence of different IGFBPs have been reported in gastrointestinal cancers, including esophageal squamous cell carcinoma (ESCC), esophageal adenocarcinoma (EAD or EAC), and gastric adenocarcinoma (GAD or GAC). A literature-based survey clearly indicates that an urgent need exists for a focused review of the role of IGFBPs in gastrointestinal cancers. The aim of this review is to present the biochemical and molecular characteristics of IGFBPs with an emphasis specifically on the role of these proteins in the pathophysiology and tumorigenesis of gastroesophageal cancers.

Insulin-like growth factor-1 receptor is associated with better prognosis in classical Hodgkin's lymphoma: Correlation with MET expression

The purpose of this study was to examine the prognostic significance of insulin-like growth factor-1 receptor (IGF-1R) expression alone and in relation to the expression of the MET- receptor and the MET-homologous receptor RON, in classical Hodgkin's lymphoma (cHL). Tumour samples from patients with cHL (n = 202; median age 37.5 years) were analysed retrospectively for IGF-R1, MET or RON expression by immunohistochemistry using tissue microarrays. The median follow-up time was 3.7 years (range, 0.1-20 years). Twenty-nine patients (14.3%) expressed IGF-1R protein in Hodgkin/Reed-Sternberg (HRS) cells, which was associated with a better overall survival (OS) (P = 0.036). IGF-1R expression was closely associated with MET receptor expression and low level of lactate dehydrogenase. In patients with cHL receiving doxorubicin, bleomycin, vinblastine and dacarbazine, those expressing IGF-1R showed a trend towards better OS and event-free survival than IGF-1R-negative patients (P = 0.129 and P = 0.115 respectively), but statistical significance was not reached. This study suggests that IGF-1R expression could be associated with better clinical outcome in cHL but is significantly associated with the expression of MET receptor.

Antitumor effects and molecular mechanisms of figitumumab, a humanized monoclonal antibody to IGF-1 receptor, in esophageal carcinoma

The insulin-like growth factor type 1 receptor (IGF-1R) plays an essential role in the development of numerous cancers. Figitumumab (CP) is not only a monocloncal antibody, it also has agonist activity on IGF-1R. The antitumor activity of CP in esophageal squamous cell carcinoma (ESCC) is still unclear. In our study, we identified IGF-1R as an independent prognostic factor in ESCC patients, and investigated the antitumor effects of CP in ESCC cell lines. CP suppressed tumor growth and sensitized cells to chemotherapeutic drugs. In addition, CP inhibited cell proliferation, migration, colony forming activity and anti-apoptosis induced by IGF-1. Our results showed that CP not only inhibited IGF-1 induced receptor autophosphorylation and downstream signaling, but also triggered β-arrestin1 and G protein-coupled receptor kinases (GRKs) mediated ERK1/2 activation, indicating CP as a biased agonist for IGF-1R. Inhibition of ERK1/2 enhanced the antitumor activity of CP. Furthermore, CP was a more powerful agonist for IGF-1R down-regulation than IGF-1, and dysregulation of β-arrestin1 and GRKs affected this down-regulation. Thus, we demonstrated antitumor activities of CP on ESCC, and as a biased agonist, CP induced ERK1/2 activation and receptor down-regulation required β-arrestin1 and GRKs, suggesting a promising role for targeting IGF-1R in ESCC.

Assessment of insulin-like growth factor 1 receptor as an oncogene in esophageal squamous cell carcinoma and its potential implication in chemotherapy

Insulin-like growth factor-1 receptor (IGF-1R) is a tyrosine kinase receptor implicated in the pathogenesis of multiple cancers. After ligand binding, IGF-1R can initiate the activation of the PI3K/AKT/mTOR and Ras/Raf/MEK/MAPK pathways to modulate cell proliferation, survival, differentiation, motility, invasion and angiogenesis. IGF-1R is a prerequisite for tumor progression and is one of the most attractive targets for therapeutic interventions in several types of cancer. In the present study, we determined the expression of IGF-1R in an esophageal squamous cell carcinoma (ESCC) cohort, investigated the detailed function of IGF-1R and screened the potential application of IGF-1R in the clinic. We verified the higher expression of IGF-1R in ESCC tumor tissues as compared to adjacent normal tissues. We also found that high expression of IGF-1R was associated with advanced tumor progression. We used ESCC cell lines and a mouse xenograft model to detect the function of IGF-1R in vitro and in vivo. Our results suggest the oncogenic function of IGF-1R in regulating cell proliferation, clonogenesis, the cell cycle and apoptosis. In addition, we found that IGF-1R was associated with the response to standard chemotherapy drugs 5-FU and cisplatin in an ESCC cell line. More importantly, we confirmed that the serum concentration of IGF-1/IGFBP3 can be used for predicting response to chemotherapy, and increased serum levels of IGF-1 and IGFBP-3 are associated with significantly higher rates of tumor response. In the present study, we demonstrated that IGF-1R is an important oncogene in ESCC and can be used to detect the chemotherapeutic response.

Insulin-like growth factor 1 receptor is a prognostic factor in classical Hodgkin lymphoma

The interaction between the tumor cells in classical Hodgkin lymphoma (cHL) and the microenvironment includes aberrant activity of receptor tyrosine kinases. In this study we evaluated the expression, functionality and prognostic significance of Insulin-like growth factor-1 receptor (IGF-1R) in cHL. IGF-1R was overexpressed in 55% (44/80) of cHL patients. Phosphorylated IGF-1R was detectable in a minority of the IGF-1R positive tumor cells. The overall survival (OS, 98%) and 5-year progression-free survival (PFS, 93%) was significantly higher in IGF-1R positive cHL patients compared to IGF-1R negative patients (OS 83%, p = .029 and PFS 77%, p = .047, respectively). Three cHL cell lines showed expression of IGF-1R, with strong staining especially in the mitotic cells and expression of IGF-1. IGF-1 treatment had a prominent effect on the cell growth of L428 and L1236 cells and resulted in an increased phosphorylation of IGF1R, Akt and ERK. Inhibition of IGF-1R with cyclolignan picropodophyllin (PPP) decreased cell growth and induced a G2/M cell cycle arrest in all three cell lines. Moreover, a decrease in pCcd2 and an increase in CyclinB1 levels were observed which is consistent with the G2/M cell cycle arrest. In conclusion, IGF-1R expression in HRS cells predicts a favorable outcome, despite the oncogenic effect of IGF-1R in cHL cell lines.

The effect of IGF-I receptor blockade for human esophageal squamous cell carcinoma and adenocarcinoma

Insulin-like growth factor-I receptor (IGF-IR) signaling is required for carcinogenicity and tumor development, and this pathway has not been well studied in human esophageal carcinomas. Esophageal cancer is one of the human cancers with the worst prognosis and has two main histologies: squamous cell carcinomas (ESCC) and adenocarcinoma (EAC). Previously, we have reported that detection of the IGF axis may be useful for the prediction of recurrence and poor prognosis of ESCC. We have also shown the successful therapy for several gastrointestinal cancers using recombinant adenoviruses expressing dominant negative IGF-IR (ad-IGF-IR/dn). The aim of this study is to develop potential targeted therapeutics to IGF-IR and to assess the effect of IGF-IR blockade in both of these types of esophageal cancer. We determined immunohistochemical expression of IGF-IR in a tissue microarray. We then assessed the effect of IGF-IR blockade on signal transduction, proliferation, apoptosis, and motility. Ad-IGF-IR/dn, a tyrosine kinase inhibitor, BMS-536924, and adenovirus expressing shRNA for IGF-IR were used. IGF-IR expression was common in both tumor types but not in normal tissues. IGF-IR was detected in metastatic sites at similar levels compared to the primary site. IGF-IR inhibition suppressed proliferation and colony formation in both cancers. IGF-IR blockades up-regulated both stress- and chemotherapy-induced apoptosis and reduced migration. Although IGF-IR/dn blocked ligand-induced activation of Akt-1 mainly, BMS-536924 effectively blocked both activation of Akt and MAPK. The IGF axis might play a key role in tumor progression of esophageal carcinomas. The IGF-IR targeting strategies might thus be useful anticancer therapeutics for human esophageal malignancies.

Association of Barrett's esophagus with type II Diabetes Mellitus: results from a large population-based case-control study

BACKGROUND & AIMS

Central obesity could increase the risk for Barrett's esophagus (BE) and esophageal adenocarcinoma by mechanical and/or metabolic mechanisms, such as hyperinsulinemia. We performed an epidemiologic study to determine whether prior type 2 diabetes mellitus (DM2) is associated with BE.

METHODS

We performed a population-based case-control study using the General Practice Research Database, a UK primary care database that contains information on more than 8 million subjects, to identify cases of BE (using previously validated codes; n = 14,245) and matched controls without BE (by age, sex, enrollment date, duration of follow-up evaluation, and practice region by incidence density sampling; n = 70,361). We assessed the association of a prior diagnosis of DM2 with BE using conditional univariate and multivariable regression analysis. Confounders assessed included smoking, obesity measured by body mass index (BMI), and gastroesophageal reflux disease.

RESULTS

BE cases were more likely than controls to have smoked (52.4% vs 49.9%), have a higher mean BMI (27.2 vs 26.9), and a higher prevalence of DM2 than controls (5.8% vs 5.3%). On multivariable analysis, DM2 was associated with a 49% increase in the risk of BE, independent of other known risk factors (odds ratio, 1.49; 95% confidence interval, 1.16-1.91). This association was stronger in women than men. Results remained stable with sensitivity analyses.

CONCLUSIONS

In a large population-based case-control study, DM2 was a risk factor for BE, independent of obesity (as measured by BMI) and other risk factors (smoking and gastroesophageal reflux disease). These data suggest that metabolic pathways related to DM2 should be explored in BE pathogenesis and esophageal carcinogenesis.

Resveratrol-induced apoptosis is enhanced by inhibition of autophagy in esophageal squamous cell carcinoma

The anti-cancer activity of resveratrol in human esophageal squamous cell carcinoma (ESCC) was investigated focusing on the role of autophagy and its effects on apoptotic cell death. We demonstrated that resveratrol inhibits ESCC cell growth in a dose-dependent manner by inducing cell cycle arrest at the sub-G1 phase and resulting in subsequent apoptosis. Mechanistically, resveratrol-induced autophagy in the ESCC cells is AMPK/mTOR pathway independent. Since both pharmacological and genetic inhibition of autophagy enhanced the resveratrol-induced cytotoxicity to the ESCC cells, this provided a novel strategy in potentiating the anti-cancer effects of resveratrol and other chemotherapeutic reagents in ESCC cancer treatment.

Alternative cytotoxic effects of the postulated IGF-IR inhibitor picropodophyllin in vitro

The insulin-like growth factor-1 (IGF-I) and its receptors play an important role in transformation and progression of several malignancies. Inhibitors of this pathway have been developed and evaluated but generally performed poorly in clinical trials, and several drug candidates have been abandoned. The cyclolignan picropodophyllin (PPP) has been described as a potent and selective IGF-IR inhibitor and is currently undergoing clinical trials. We investigated PPP's activity in panels of human cancer cell lines (e.g., esophageal squamous carcinoma cell lines) but found no effects on the phosphorylation or expression of IGF-IR. Nor was the cytotoxic activity of PPP related to the presence or spontaneous phosphorylation of IGF-IR. However, its activity correlated with that of known tubulin inhibitors, and it destabilized microtubule assembly at cytotoxic concentrations also achievable in patients. PPP is a stereoisomer of podophyllotoxin (PPT), a potent tubulin inhibitor, and an equilibrium between the two has previously been described. PPP could thus potentially act as a reservoir for the continuous generation of low doses of PPT. Interestingly, PPP also inhibited downstream signaling from tyrosine kinase receptors, including the serine/threonine kinase Akt. This effect is associated with microtubule-related downregulation of the EGF receptor, rather than the IGF-IR. These results suggest that the cytotoxicity and pAkt inhibition observed following treatment with the cyclolignan PPP in vitro result from microtubule inhibition (directly or indirectly by spontaneous PPT formation), rather than any effect on IGF-IR. It is also suggested that PPT should be used as a reference compound in all future studies on PPP.

Targeting the insulin growth factor receptor 1

The IGF axis is a tightly controlled endocrine system that regulates cell growth and development, known to have an important function in cancer biology. IGF1 and IGF2 can promote cancer growth in a GH-independent manner both through paracrine and autocrine secretion and can also confer resistance to chemotherapy and radiation. Many alterations of this system have been found in neoplasias, including increased expression of ligands and receptors, loss of heterozygosity of the IGF2 locus and increased IGF1R gene copy number. The IGF1 network is an attractive candidate for targeted therapy, including receptor blockade with monoclonal antibodies and small molecule inhibitors of receptor downstream signaling. This article reviews the role of the IGF axis in the initiation and progression of cancer, and describes the recent advances in IGF inhibition as a therapeutic tool.

IGF-1 and its receptor in esophageal cancer: association with adenocarcinoma and visceral obesity

OBJECTIVES

The insulin-like growth factor (IGF) pathway and visceral obesity have been independently linked with esophageal cancer. This study aimed to delineate the differential and interlinked role of visceral obesity and the IGF-1 system in esophageal adenocarcinoma and esophageal squamous-cell carcinoma (SCC).

METHODS

IGF-1 receptor (IGF-1R) mRNA and protein were examined in esophageal SCC (KYSE 410, OE21) and esophageal adenocarcinoma (OE19, OE33) cell lines by western blotting. Tumor cell proliferation in response to IGF-1 was assessed by bromodeoxyuridine incorporation assay. In esophageal tumor sections, expression of IGF-1R and CD68(+) cell numbers were assessed by immunohistochemistry. IGF-1 was measured in serum from esophageal cancer patients, Barrett's esophagus patients, and healthy controls by enzyme-linked immunosorbent assay.

RESULTS

Higher IGF-1R protein expressions were observed in SCC cells compared with esophageal adenocarcinoma cells however only adenocarcinoma cell lines significantly increased proliferation in response to IGF-1 (P<0.01). Serum IGF-1 levels were highest in esophageal adenocarcinoma patients (P<0.01) and higher in viscerally obese vs. nonobese (P<0.05) patients. In resected esophageal cancer, increased expression of IGF-1R was observed in the tumor and invasive edge compared with tumor-associated stroma (P<0.05), which coincided with increased CD68(+) cells in stromal tissue surrounding invasive tumor edge (P<0.01).

CONCLUSIONS

This novel study examined the differential role of the IGF system in esophageal adenocarcinoma and SCC, and its association with visceral obesity. These results indicate that the IGF-1 axis has a key role in malignant progression of esophageal cancer, and represents a plausible mechanism through which visceral obesity impacts on esophageal adenocarcinoma risk and tumor biology.

Role of the insulin-like growth factor 1 axis and visceral adiposity in oesophageal adenocarcinoma

BACKGROUND

Epidemiological studies have linked obesity with many cancers. The insulin-like growth factor (IGF) 1 axis may be an important mediator in obesity-associated cancer. This study examined the relationship between IGF-1 and its receptor (IGF-1R) in oesophageal adenocarcinoma, a cancer strongly linked to obesity.

METHODS

Patients with oesophageal adenocarcinoma considered suitable for attempted curative treatment were studied. Visceral adiposity was defined by waist circumference or visceral fat area. Free and total IGF-1 in serum were measured by enzyme-linked immunosorbent assay. Quantitative polymerase chain resection was used to determine mRNA expression of IGF-1 and IGF-1R in resected tumour samples. IGF-1R expression in tissue microarrays (TMAs) was quantified by immunohistochemistry.

RESULTS

A total of 220 patients were studied. Total and free IGF-1 levels were significantly increased in the serum of viscerally obese patients. Gene expression analysis revealed a significant association between obesity status and both IGF-1R (P = 0·021) and IGF-1 (P = 0·031) in tumours. TMA analysis demonstrated that IGF-1R expression in resected tumours was significantly higher in viscerally obese patients than in those of normal weight (P = 0·023). Disease-specific survival was longer in patients with negative IGF-1R expression than in those with IGF-1R-positive tumours (median 60·0 versus 23·4 months; P = 0·027).

CONCLUSION

This study highlighted the association of the IGF axis with visceral obesity, and a potential impact on the biology of oesophageal adenocarcinoma through its receptor. Targeting the IGF axis may have a rationale in future studies.

mTORC1 activity as a determinant of cancer risk--rationalizing the cancer-preventive effects of adiponectin, metformin, rapamycin, and low-protein vegan diets

Increased plasma levels of adiponectin, metformin therapy of diabetes, rapamycin administration in transplant patients, and lifelong consumption of low-protein plant-based diets have all been linked to decreased risk for various cancers. These benefits may be mediated, at least in part, by down-regulated activity of the mTORC1 complex, a key regulator of protein translation. By boosting the effective availability of the translation initiator eIF4E, mTORC1 activity promotes the translation of a number of "weak" mRNAs that code for proteins, often up-regulated in cancer, that promote cellular proliferation, invasiveness, and angiogenesis, and that abet cancer promotion and chemoresistance by opposing apoptosis. Measures which inhibit eIF4E activity, either directly or indirectly, may have utility not only for cancer prevention, but also for the treatment of many cancers in which eIF4E drives malignancy. Since eIF4E is overexpressed in many cancers, strategies which target eIF4E directly--some of which are now being assessed clinically--may have the broadest efficacy in this regard. Many of the "weak" mRNAs coding for proteins that promote malignant behavior or chemoresistance are regulated transcriptionally by NF-kappaB and/or Stat3, which are active in a high proportion of cancers; thus, regimens concurrently targeting eIF4E, NF-kappaB, and Stat3 may suppress these proteins at both the transcriptional and translational levels, potentially achieving a very marked reduction in their expression.

Advances in rodent models of human esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a common form of malignant disease. Appropriate animal models recapitulating human cancers, which are powerful not only for the elucidation of in vivo process and relevant mechanisms of the diseases but also for the evaluation of efficacy and safety of new drugs and management concepts, are critical for the success of translational research. In this context, compared with other malignancies, the present situation for human ESCC that novel discoveries for either diagnostic markers or therapeutic targets as well as the clinical application are out of step (laggard) is largely attributed to the lack of suitable in vivo animal model for this human disease. This article provides an overview of the currently available animal models established for human ESCC, encompassing chemically induced and genetically engineered rodents. Genetically engineered mice coupling induction with 4-nitroquinoline-1-oxide (4NQO) are discussed in more detail.

Insulin-like growth factor-1 receptor as a novel prognostic marker and its implication as a cotarget in the treatment of human adenocarcinoma of the esophagus

Insulin-like growth factor-1 receptor (IGF-1R) and human epidermal growth factor receptor-2 (HER2) receptor expression has been found to be a key regulator of tumorigenesis. The purpose of our study was to establish the prognostic significance of IGF-1R in esophageal cancer and to determine the effect of IGF-1R and HER2 targeting with alpha-IR3 and Herceptin antibodies on the proliferation of esophageal cancer cells in vitro. IGF-1R expression and clinicopathological correlations were analyzed with a tissue microarray containing 234 esophageal cancer specimens (133 adenocarcinomas and 101 squamous cell carcinomas). Proliferation changes associated with Herceptin and alpha-IR3 blockage were evaluated with the unique human esophageal cancer cell lines Pt1590 and LN1590. IGF-1R and HER2 expression levels, activation and phosphorylation status of downstream signaling proteins involved in the activation pathways were analyzed by Western blotting. IGF-1R overexpression was detected in 121 (52%) of the 234 esophageal tumors examined. In the subgroup of 87 HER2-positive tumors, 93.1% showed concordant overexpression for IGF-1R. IGF-1R was identified as a variable associated with reduced overall survival for adenocarcinoma (p = 0.05), but not for squamous cell carcinoma. The combination of Herceptin and alpha-IR3 was more effective in inhibiting in vitro proliferation than treatment with either agent alone (p < 0.01). This was associated with a decrease in HER2 and IGF-1R protein levels and suppression of Akt- and MAP kinase phosphorylation. IGF-1R expression can be used as a novel prognostic marker for adenocarcinomas of the esophagus. Cotreatment with IGF-1R and HER2 antibodies might become a valuable and effective treatment option in esophageal adenocarcinoma.

Novel targets in esophageal and gastric cancer: beyond antiangiogenesis

Cancers of the stomach, gastroesophageal junction and esophagus are a major cause of cancer-related deaths worldwide. In Western countries, adenocarcinomas of the distal esophagus, gastroesophageal junction and proximal stomach have been increasing in frequency more rapidly than other malignancies. The majority of newly diagnosed patients present with advanced disease and the overall survival remains dismal at approximately 10% at 5 years. Better understanding of tumor biology has led to the development of promising novel therapeutic strategies. There is therefore increasing optimism that some of these approaches will improve the outcomes in these increasingly common cancers. Given the success of antiangiogenesis as a therapeutic strategy in various types of cancer, there are ongoing efforts to investigate the utility of other targeted therapies in the treatment of gastric and esophageal cancers. This review will focus on novel therapeutic targets other than angiogenesis and provide a rationale for the further clinical evaluation of these agents in patients with upper gastrointestinal tract cancers.

Esophagogastric cancer: targeted agents

Because of the poor prognosis for patients with locally advanced and metastatic esophageal, gastroesophageal junction and gastric cancers, increasing attention has focused on the integration of targeted agents into current therapies. The molecular targets of these agents include epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF) or its receptor, cyclooxygenase-2 (COX-2), mammalian target of rapamycin (mTOR) and components and regulators of the cell cycle. In this review article, we briefly discuss pre-clinical data and the rationale for targeting these pathways and summarize the results of clinical trials to-date, including completed and ongoing phase III evaluations.

Does diabetes mellitus influence pathologic complete response and tumor downstaging after neoadjuvant chemoradiation for esophageal and gastroesophageal cancer? A two-institution report

BACKGROUND

Esophageal carcinoma is an aggressive disease that is often treated with neoadjuvant therapy followed by surgical resection. Diabetes mellitus (DM) has been associated with reduced efficacy of chemoradiation (CRT) in other gastrointestinal cancers. The goal of this study was to determine if DM affects response to neoadjuvant CRT in the management of gastroesophageal carcinoma.

METHODS

We retrospectively reviewed the esophageal cancer patient databases and subsequently analyzed those patients who received neoadjuvant CRT followed by surgical resection at two institutions, Thomas Jefferson University (TJUH) and Fox Chase Cancer Center (FCCC). Comparative analyses of rates of pathologic complete response rate (pCR) and pathologic downstaging in DM patients versus non-DM patients was performed.

RESULTS

Two hundred sixty patients were included in the study; 36 patients had DM and 224 were non-diabetics. The average age of the patients was 61 years (range 24-84 years). The overall pCR was 26%. The pCR rate was 19% and 27% for patients with DM and without DM, respectively (P = 0.31). Pathologic downstaging occurred in 39% of study patients, including of 33% of DM patients and 40% of non-DM patients (P = 0.42).

CONCLUSIONS

Although the current analysis does not demonstrate a significant reduction in pCR rates or pathologic downstaging in patients with DM, the observed trend suggests that a potential difference may be observed with a larger patient population. Further studies are warranted to evaluate the influence of DM on the effectiveness of neoadjuvant CRT in esophageal cancer.

Hsp90 is expressed and represents a therapeutic target in human oesophageal cancer using the inhibitor 17-allylamino-17-demethoxygeldanamycin

Heat shock protein 90 (Hsp90) has been demonstrated to protect oncogenic variants of signalling molecules from degradation and may consequently serve as a therapeutic target for the treatment of oesophageal cancer for which adequate therapy is often lacking. We studied the expression of Hsp90 in tumour tissues of human oesophageal cancer and the impact of Hsp90 inhibition on oesophageal cancer cell lines using the drug 17-allylamino-17-demethoxygeldanamycin (17-AAG). Quantitative immunohistochemistry was performed on formalin-fixed paraffin-embedded tissues from patients with oesophageal cancer. In squamous cell carcinoma, a marked upregulation of Hsp90 could be noted in dysplastic epithelium and invasive cancer compared with normal epithelium. In adenocarcinoma, Hsp90 was expressed in neoplastic epithelium and also in normal non-neoplastic glands weakly. The inhibition of Hsp90 using 17-AAG led to a significant decrease in cell proliferation and viability in human oesophageal cancer cell lines. Using a clonogenic cell survival assay, Hsp90 inhibition significantly sensitised the cells for γ-photon irradiation. Heat shock protein 90 was found to be critical for proper signalling induced by both epidermal growth factor and insulin-like growth factor-1, in which the inhibition of signalling by 17-AAG correlated with the observed reduction in cell proliferation and viability. These results showed that Hsp90 was selectively expressed in oesophageal cancer tissue compared with the corresponding normal tissue, and the inhibition of Hsp90 resulted in decreased proliferation and viability as well as radiosensitisation of oesophageal cancer cells. Heat shock protein 90 represents a potential therapeutic target in the treatment of patients with oesophageal cancer, alone or in combination with radiotherapy.

A pilot study of the association of low plasma adiponectin and Barrett's esophagus

BACKGROUND AND AIMS

Gastroesophageal reflux disease (GERD) and obesity are associated with esophageal adenocarcinoma (EAC). We hypothesized that the obesity-EAC relation is mediated by factors secreted from adipocytes. Adiponectin is a peptide secreted by adipocytes, and its plasma levels are inversely associated with obesity. We aimed to estimate the effect of circulating adiponectin on the risk of Barrett's esophagus (BE), an accepted precursor of EAC, controlling for GERD symptoms and other potential confounders.

METHODS

We conducted a case-control study in cases of BE compared with controls without BE; most controls had GERD. Odds ratios (OR), corresponding to associations with BE, were estimated from conditional and unconditional logistic regression analyses of 50 matched pairs.

RESULTS

BE was inversely associated with plasma adiponectin level (OR for each 10-microg/mL decrement 4.7, 95% confidence interval [CI] 1.4-15.0) and positively associated with GERD duration >or=10 yr, male gender, tobacco smoking, body mass index (BMI), waist circumference, and waist-to-hip ratio. Further adjustment for GERD duration, tobacco use, and BMI increased the adiponectin-BE association (OR 6.4, 95% CI 1.1-37.0), but the estimated OR was reduced when adjusting for measures of abdominal obesity (e.g., OR 2.5, 95% CI 0.49-13.00) and further adjusting for gender (OR 1.8, 95% CI 0.66-4.70).

CONCLUSIONS

Despite methodologic limitations, including the small sample size, our findings suggest that adiponectin may be involved in the etiology of BE. Rather than simply a mechanical effect of obesity promoting GERD, the effects of abdominal obesity on the risk of BE might be mediated by adiponectin and other circulating factors.

Longitudinal study of insulin-like growth factor, insulin-like growth factor binding protein-3, and their polymorphisms: risk of neoplastic progression in Barrett's esophagus

BACKGROUND

Insulin-like growth factor-I (IGF-I) is a potent mitogen. IGF-I and its main binding protein, IGF binding protein-3 (IGFBP-3), and their polymorphisms have been investigated in relation to risk of many cancers, but not esophageal adenocarcinoma.

MATERIALS AND METHODS

We used data and specimens from a longitudinal study of persons with Barrett's esophagus (n=344; median, 5.4 years follow up) to determine whether baseline serum concentrations of IGF-I and IGFBP-3 and associated polymorphisms were related to the risk of developing esophageal adenocarcinoma or flow cytometric abnormalities.

RESULTS

Overall, circulating concentrations of IGF-I and IGBP-3 were not associated with risk of esophageal adenocarcinoma or flow cytometric abnormalities, with the exception of an approximate tripling of risk of aneuploidy among participants with higher IGFBP-3 levels [above median; adjusted hazard ratio (HR) comparing subjects with levels lower than median versus higher of equal to median, 2.7; 95% confidence interval (95% CI), 1.2-6.0; P=0.01]. Genotypic analyses revealed that persons with the IGF-I [cytosine-adenine (CA)](19) or the IGFBP-3 A-202C C allele were associated with lower circulating concentrations of IGF-I (P(trend)=0.01) and IGFBP-3 (P(trend)=0.002), respectively. Persons with two copies of the IGF-I receptors 2-bp deletion allele had a nonsignificant 2-fold increased risk of tetraploidy (HR, 2.3; 95% CI, 0.9-5.9; P(trend)=0.11). After adjustment for IGFBP-3 levels, participants carrying two IGFBP-3 C alleles had a significantly higher risk of developing aneuploidy (HR, 3.8; 95% CI, 1.0-14.0; P(trend)=0.04) than carriers of A alleles; whereas no associations were observed between the outcomes studied and the IGF-I receptors AGG trinucleotide repeat polymorphism at position 97.

CONCLUSION

Our findings, although based on a relatively small number of outcomes and subject to several limitations, indicate a potential role of the complex IGF system in neoplastic progression among persons with Barrett's esophagus.

Activation of growth factor receptors in esophageal cancer--implications for therapy

Esophageal cancer is a highly aggressive disease and is the seventh most common cause of cancer-related death in the western world. Worldwide, it ranks as the sixth most frequent cause of cancer death. Despite advances in surgical techniques and treatment, the prognosis of esophageal cancer remains poor, with very few long-term survivors. The need for novel strategies to detect esophageal cancer earlier and to improve current therapy is urgent. It is well established that growth factors and growth factor receptor-mediated signaling pathways are important components of the transformation process in many forms of cancer, including esophageal cancer. With the recent advances in drug development, there are emerging possibilities to use growth factor signal transduction pathways in targeted therapy. This review provides a summary of the role of growth factors and their receptors in esophageal cancer and discusses their potential roles as biomarkers and as targets in therapy.

Requirement of MMP-3 in anchorage-independent growth of oral squamous cell carcinomas

BACKGROUND

Matrix metalloproteinase-3 (MMP-3) is expressed in various carcinomas; however, its function is not clearly established. This study was to assess its possible role in oral squamous cell carcinomas (OSCCs).

MATERIALS AND METHODS

Specimens of seven oral pre-malignant lesions (OPMLs) and 92 OSCCs were subjected to MMP-3 detection by RT-PCR and Western blot. Antisense oligodeoxynucleotides (AODNs) of MMP-3 were used to transfect OSCC (OECM-1 and SCC-9) and esophageal carcinoma (CE81T/VGH) cell lines, and their growth was subsequently analyzed by XTT and soft-agar colony assay.

RESULTS

MMP-3 transcript was preferentially expressed in OSCCs (71 of 92, 77%) than in OPMLs (two of seven, 29%; P = 0.012). Both MMP-3 transcript and protein levels were significantly higher in OSCC masses than in neighboring tissues (P < 0.0001 and P = 0.04, respectively). Growth of the three cell lines was not affected, while the colony numbers of OECM-1 and CE81T/VGH were significantly reduced by the transfection of MMP-3 AODNs (P = 0.002 and P = 0.004, respectively). SCC-9 did not form colonies in soft-agar/medium.

CONCLUSIONS

MMP-3 function may be required in most OSCCs, and it may support the anchorage-independent growth of both OSCC and esophageal carcinoma.

Up-regulation of matrix metalloproteinase-8 by betel quid extract and arecoline and its role in 2D motility

Betel quid (BQ) and matrix metalloproteinase-8 (MMP-8) play roles in oral diseases. Here, we analyzed the regulation of MMP-8 by BQ and its effect on cell migration. We found that BQ extract (BQE) increased the secretion of an 85kDa caseinolytic proteinase, specifically precipitated by an anti-MMP-8 antibody, in the culture medium of OECM-1, an oral squamous cell carcinoma (OSCC) cell line. BQE also stimulated MMP-8 secretion in an esophageal carcinoma cell line, CE81T/VGH, in a dose-dependent manner, and MMP-8 protein was maximally expressed at 24h after BQE treatment in OECM-1. The BQE-induced MMP-8 expression was dose-dependently inhibited by PD98059. Arecoline, the major alkaloid of areca nut, was tested to dose-dependently up-regulate MMP-8 protein level. Moreover, both arecoline- (4.7-fold) and BQE-selected (5.5-fold) CE81T/VGH cells expressed higher MMP-8 protein level and exhibited enhanced two-dimensional (2D) motility (p=0.009 in both cells) than parental cells. The enhanced motility of arecoline- (p=0.006) and BQE-selected (p=0.002) cells was both specifically blocked by an anti-MMP-8 antibody. We conclude that BQ may accelerate tumor migration by stimulating MMP-8 expression through MEK pathway in at least some carcinomas of the upper aerodigestive tract. Furthermore, arecoline may be one of the positive MMP-8 regulators among BQ ingredients.

Serum levels of IGF-I and IGFBP-III and their relation with carcinoembryonic antigen and carbohydrate antigen 19-9 in cases of esophageal cancer

Tumour markers are used for diagnosis, staging, evaluation of response to treatment, prognosis and detection of recurrences in clinical oncology. In this study, we aim to investigate the levels of insulin-like growth factor (IGF)-I and IGF-binding protein (IGFBP)-III in cases with oesophageal carcinoma. We investigated their possible use as tumour markers and their relation to other tumour markers. Forty patients who were diagnosed as having oesophageal carcinoma by histopathological evaluation of endoscopic biopsies between January 2003 and July 2004 and 40 healthy people as the control group were included in the study. The serum levels of tumour markers including IGF-I, IGFBP-III, carcinoembryonic antigen (CEA) and carbohydrate antigen (CA) 19-9 were measured in both groups. Data were compared statistically, and the importance of IGF-I and IGFBP-III levels were investigated in cases with oesophageal carcinoma. IGF-I levels were significantly higher in patients with oesophageal carcinoma when compared with the control group (p < 0.05), whereas IGFBP-III levels were significantly lower (p < 0.05). The increase in CEA levels was not statistically significant when compared with the control group. The increase in CA 19-9 levels was statistically significant when compared with the control group (p < 0.05). No correlation was detected between levels of IGF-I and IGFBP-III and levels of CEA and CA 19-9. We suggest that the serum IGF-I level may be used as a tumour marker in oesophageal carcinoma. A low level of serum IGFBP-III is also significant in cases with oesophageal carcinoma. We believe that drugs which inhibit IGF-I function or which stimulate the function of IGFBP-III may open new horizons in extra-surgical modalities for the treatment of oesophageal cancer.

Functional role of matrix metalloproteinase-28 in the oral squamous cell carcinoma

The newly identified MMP-28 has been shown to be expressed in several types of carcinomas, however, its functional role in transformation events is unknown. This study was to assess whether this proteinase plays a role in oral tumor malignancy. By using RT-PCR, we found that expression of MMP-28 was significantly higher in 92 oral squamous cell carcinomas (OSCCs) (52/92, 56.5%) than in seven oral premalignant lesions (OPMLs) (0/7, 0%) (P=0.004). No statistically significant correlation was found between MMP-28 expression and tumor stage, thickness, size, and metastasis. Both mRNA and protein of MMP-28 were preferentially concentrated in OSCC specimens than in neighboring tissues as analyzed by semi-quantitative RT-PCR (P=0.015) and immunohistochemistry, respectively. Transfection of OSCC and esophageal carcinoma cell lines with MMP-28 antisense oligodeoxynucleotide (AODN) resulted in the reduced secretion of MMP-28 protein and the ability of colony formation in soft agar without affecting cell growth. Our findings show the close correlation between MMP-28 and OSCC, and support a role for MMP-28 in the anchorage-independent growth of both OSCC and esophageal carcinomas.

Inhibition of bone-derived insulin-like growth factors by a ligand-specific antibody suppresses the growth of human multiple myeloma in the human adult bone explanted in NOD/SCID mouse

Multiple myeloma (MM) is a fatal disease that affects plasma cells. Patients with MM have 1 or more osteolytic lesions in their bone tissues, where insulin-like growth factors (IGFs; IGF-I and IGF-II) are mainly stored. The role of bone-derived IGFs in the development of MM has not been extensively studied because reliable animal models are lacking. We established an animal model using a human MM cell line, RPMI8226, in nonobese diabetic/severe-combined immunodeficient (NOD/SCID) mice implanted with human adult bone (HAB) fragments. Treatment with an anti-human IGF-neutralizing monoclonal antibody, KM1468, inhibited the IGF-I-stimulated phosphorylation of type-I IGF receptors (IGF-IR) in RPMI8226 cells and the activation of the downstream PI3-K/Akt signaling pathway in vitro. KM1468 inhibited IGF-I-mediated RPMI8226 cell growth in a dose-dependent manner. In the NOD/SCID-HAB model, treatment with KM1468 significantly inhibited the growth of RPMI8226 cells (p<0.02). These results indicated that the growth of MM cells was predominantly stimulated not by serum-derived IGFs, but by bone-derived IGFs. Furthermore, the targeting of bone-derived IGFs, using a neutralizing antibody, may offer a new therapeutic strategy for MM.

Targeting the epidermal growth factor receptor by erlotinib (Tarceva) for the treatment of esophageal cancer

Esophageal cancer is the sixth most common cause of cancer-related death worldwide. Because of very poor 5-year survival new therapeutic approaches are mandatory. Erlotinib (Tarceva), an inhibitor of epidermal growth factor receptor tyrosine kinase (EGFR-TK), potently suppresses the growth of various tumors but its effect on esophageal carcinoma, known to express EGFR, remains unexplored. We therefore studied the antineoplastic potency of erlotinib in human esophageal cancer cells. Erlotinib induced growth inhibition of the human esophageal squamous cell carcinoma (ESCC) cell lines Kyse-30, Kyse-70 and Kyse-140, and the esophageal adenocarcinoma cell line OE-33, as well as of primary cell cultures of human esophageal cancers. Combining erlotinib with the EGFR-receptor antibody cetuximab, the insulin-like growth factor receptor tyrosine kinase inhibitor tyrphostin AG1024, or the 3-hydroxy-3-methylglutaryl coenzyme. A reductase (HMG-CoAR) inhibitor fluvastatin resulted in additive or even synergistic antiproliferative effects. Erlotinib induced cell cycle arrest at the G1/S checkpoint. The erlotinib-mediated signaling involved the inactivation of EGFR-TK and ERK1/2, the upregulation of the cyclin-dependent kinase inhibitors p21(Waf1/CIP1) and p27(Kip1), and the downregulation of the cell cycle promoter cyclin D1. However, erlotinib did not induce immediate cytotoxicity or apoptosis in esophageal cancer cells. The inhibition of EGFR-TK by erlotinib appears to be a promising novel approach for innovative treatment strategies of esophageal cancer, as it powerfully induced growth inhibition and cell cycle arrest in human esophageal cancer cells and enhanced the antineoplastic effects of other targeted agents.