Epidermal growth factor receptor vIII enhances tumorigenicity and resistance to 5-fluorouracil in human hepatocellular carcinoma

Enhanced anti-tumor efficacy of electroporation (EP)-mediated DNA vaccine boosted by allogeneic lymphocytes in pre-established tumor models

BACKGROUND

Tumor-reactive T cells play a crucial role in anti-tumor responses, but T cells induced by DNA vaccination are time-consuming processes and exhibit limited anti-tumor efficacy. Therefore, we evaluated the anti-tumor effectiveness of reactive T cells elicited by electroporation (EP)-mediated DNA vaccine targeting epidermal growth factor receptor variant III (pEGFRvIII plasmid), in conjunction with adoptive cell therapy (ACT), involving the transfer of lymphocytes from a pEGFRvIII EP-vaccinated healthy donor.

METHODS

The validation of the established pEGFRvIII plasmid and EGFRvIII-positive cell model was confirmed through immunofluorescence and western blot analysis. Flow cytometry and cytotoxicity assays were performed to evaluate the functionality of antigen-specific reactive T cells induced by EP-mediated pEGFRvIII vaccines, ACT, or their combination. The anti-tumor effectiveness of EP-mediated pEGFRvIII vaccines alone or combined with ACT was evaluated in the B16F10-EGFRvIII tumor model.

RESULTS

EP-mediated pEGFRvIII vaccines elicited serum antibodies and a robust cellular immune response in both healthy and tumor-bearing mice. However, this response only marginally inhibited early-stage tumor growth in established tumor models. EP-mediated pEGFRvIII vaccination followed by adoptive transfer of lymphocytes from vaccinated healthy donors led to notable anti-tumor efficacy, attributed to the synergistic action of antigen-specific CD4+ Th1 cells supplemented by ACT and antigen-specific CD8+ T cells elicited by the EP-mediated DNA vaccination.

CONCLUSIONS

Our preclinical studies results demonstrate an enhanced anti-tumor efficacy of EP-mediated DNA vaccination boosted with adoptively transferred, vaccinated healthy donor-derived allogeneic lymphocytes.

Splice-Switching Antisense Oligonucleotides Targeting Extra- and Intracellular Domains of Epidermal Growth Factor Receptor in Cancer Cells

Cancer is one of the leading causes of death globally. Epidermal growth factor receptor is one of the proteins involved in cancer cell proliferation, differentiation, and invasion. Antisense oligonucleotides are chemical nucleic acids that bind to target messenger ribonucleic acid and modulate its expression. Herein, we demonstrate the efficacy of splice-modulating antisense oligonucleotides to target specific exons in the extracellular (exon 3) and intracellular (exon 18, 21) domains of epidermal growth factor receptor. These antisense oligonucleotides were synthesized as 25mer 2'-O methyl phosphorothioate-modified ribonucleic acids that bind to complementary specific regions in respective exons. We found that PNAT524, PNAT525, PNAT576, and PNAT578 effectively skipped exon 3, exon 18, and exon 21 in glioblastoma, liver cancer, and breast cancer cell lines. PNAT578 treatment also skipped partial exon 19, complete exon 20, and partial exon 21 in addition to complete exon 21 skipping. We also found that a cocktail of PNAT576 and PNAT578 antisense oligonucleotides performed better than their individual counterparts. The migration potential of glioblastoma cancer cells was reduced to a greater extent after treatment with these antisense oligonucleotides. We firmly believe that using these splice-modulating antisense oligonucleotides in combination with existing EGFR-targeted therapies could improve therapeutic outcomes.

Overexpression of β-Ketoacyl-CoA Synthase From Vitis vinifera L. Improves Salt Tolerance in Arabidopsis thaliana

Grape (Vitis vinifera L.) is a fruit tree with high salt tolerance and high nutritional value, medicinal value, and economic value. Suberin in roots is characterized by long-chain fatty acids and is thought to be related to the salt tolerance of grape. The key enzyme in the fatty acid elongation process is β-ketoacyl-CoA synthase (KCS). The function and the regulatory mechanism of VvKCS in response to salt stress in grape are unclear. In this study, VvKCS was isolated from V. vinifera L. A real-time quantitative polymerase chain reaction analysis showed that salt stress enhanced VvKCS transcription levels in grapes. Overexpression of VvKCS increased the tolerance to salt stress in Arabidopsis during the germination and seedling stages. The improved salt tolerance was the result of the combined contributions of multiple mechanisms including the regulation of expression of ion transporters and channels, accumulation of osmotic regulating substances, and maintenance of membrane stability. The results of this study are valuable information on plant salt tolerance and provide a theoretical basis for the molecular mechanism of grape salt tolerance.

Sorafenib Resistance in Hepatocellular Carcinoma: The Relevance of Genetic Heterogeneity

Despite advances in biomedicine, the incidence and the mortality of hepatocellular carcinoma (HCC) remain high. The majority of HCC cases are diagnosed in later stages leading to the less than optimal outcome of the treatments. Molecular targeted therapy with sorafenib, a dual-target inhibitor targeting the serine-threonine kinase Raf and the tyrosine kinases VEGFR/PDGFR, is at present the main treatment for advanced-stage HCC, either in a single or combinatory regimen. However, it was observed in a large number of patients that its effectiveness is hampered by drug resistance. HCC is highly heterogeneous, within the tumor and among individuals, and this influences disease progression, classification, prognosis, and naturally cellular susceptibility to drug resistance. This review aims to provide an insight on how HCC heterogeneity influences the different primary mechanisms of chemoresistance against sorafenib including reduced drug intake, enhanced drug efflux, intracellular drug metabolism, alteration of molecular targets, activation/inactivation of signaling pathways, changes in the DNA repair machinery, and negative balance between apoptosis and survival of the cancer cells. The diverse variants, mutations, and polymorphisms in molecules and their association with drug response can be a helpful tool in treatment decision making. Accordingly, the existence of heterogeneous biomarkers in the tumor must be considered to strengthen multi-target strategies in patient-tailored treatment.

EGFRvIII-specific CAR-T cells produced by piggyBac transposon exhibit efficient growth suppression against hepatocellular carcinoma

Adoptive cellular immunotherapy employing chimeric antigen receptors-modified T (CAR-T) cells has demonstrated promising antitumor effects in hematologic cancers. However, CAR-T therapy confront many challenges in solid tumors like immunosuppressive microenvironment, molecular heterogeneity, etc. The cancer genome atlas (TCGA) of hepatocellular carcinoma (HCC) revealed many genetic characteristic and molecular tumorigenesis. EGFRvIII is a tumor specific antigen widely expressed in a variety of cancers including HCC and an ideal therapeutic target for cancer therapy. The liver cancer cell line SMMC7721 express high level EGFRvIII and widely applied in HCC investigations. Herein, we developed EGFRvIII CAR-T cells by piggyBac transposon system, and detected its specific killing effect against SMMC7721 cells in vitro and in vivo. Results indicated that transduction efficiency of CAR reached 53.1%. Expression of CAR protein was verified by immunoblotting as a band of approximate 57KD. The killing effect of CAR-T cells against SMMC7721 was positively correlated with E/T ratio (E:T=5:1, 10:1, 20:1, 40:1), and exceeded 50% at 20:1 ratio. Significant increase in IFN-γ and TNF-α secretion were detected in the co-culture supernatant of CAR-T cells and SMMC7721, comparable to the level of exogenous EGFRvIII-expressing U87 cells. The killing activity and cytokine secretion were both dependent on the expression level of EGFRvIII in target cells. In HCC xenograft models, CAR-T cells could effectively suppress the growth of SMMC7721. In conclusion, EGFRvIII CAR-T cells demonstrated specific antitumor effect against SMMC7721 in vitro and in vivo, providing basis for immunotherapy of HCC in future clinical use.

Numerical simulation of scaling-up an inverted frusto-conical shaking bioreactor with low shear stress for mammalian cell suspension culture

Shear stress is one of the key factors affecting the large-scale culture of mammalian cells. In this study, numerical simulation based on computational fluid dynamics was used to conduct a flow-field analysis of 7, 50, 200, and 1200 L inverted frusto-conical shaking bioreactors. The results show that the shear rate, specific mass transfer area (a), and volumetric oxygen mass transfer coefficient (kLa) gradually decreased as the scale of the bioreactor increased. Through application of BHK21 and CHO cells in 7, 200, and 1200 L bioreactors, it was found that the cell density and antibody expression level increased as the volume of the bioreactor increased. Moreover, the antibody expression level in a 1200 L bioreactor was nearly 30% and 35% higher than that of 7 and 200 L bioreactors, respectively. The results demonstrate that the environment with a larger volume is more suitable for the growth and antibody expression of CHO cells, indicating shear stress might be the most critical factor affecting the scale-up of mammalian cells.

Dexamethasone in Glioblastoma Multiforme Therapy: Mechanisms and Controversies

Glioblastoma multiforme (GBM) is the most common and malignant of the glial tumors. The world-wide estimates of new cases and deaths annually are remarkable, making GBM a crucial public health issue. Despite the combination of radical surgery, radio and chemotherapy prognosis is extremely poor (median survival is approximately 1 year). Thus, current therapeutic interventions are highly unsatisfactory. For many years, GBM-induced brain oedema and inflammation have been widely treated with dexamethasone (DEX), a synthetic glucocorticoid (GC). A number of studies have reported that DEX also inhibits GBM cell proliferation and migration. Nevertheless, recent controversial results provided by different laboratories have challenged the widely accepted dogma concerning DEX therapy for GBM. Here, we have reviewed the main clinical features and genetic and epigenetic abnormalities underlying GBM. Finally, we analyzed current notions and concerns related to DEX effects on cerebral oedema, cancer cell proliferation and migration and clinical outcome.

Growth suppression of colorectal cancer expressing S492R EGFR by monoclonal antibody CH12

Colorectal cancer (CRC) is a common malignant tumor in the digestive tract, and 30%-85% of CRCs express epidermal growth factor receptors (EGFRs). Recently, treatments using cetuximab, also named C225, an anti-EGFR monoclonal antibody, for CRC have been demonstrated to cause an S492R mutation in EGFR. However, little is known about the biological function of S492R EGFR. Therefore, we attempted to elucidate its biological function in CRC cells and explore new treatment strategies for this mutant form. Our study indicated that EGFR and S492R EGFR accelerate the growth of CRC cells in vitro and in vivo and monoclonal antibody CH12, which specifically recognizes an EGFR tumor-specific epitope, can bind efficiently to S492R EGFR. Furthermore, mAb CH12 showed significantly stronger growth suppression activities and induced a more potent antibody-dependent cellular cytotoxicity effect on CRC cells bearing S492R EGFR than mAb C225. mAb CH12 obviously suppressed the growth of CRC xenografts with S492R EGFR mutations in vivo. Thus, mAb CH12 may be a promising therapeutic agent in treating patients with CRC bearing an S492R EGFR mutation.

Combination of an anti-EGFRvIII antibody CH12 with Rapamycin synergistically inhibits the growth of EGFRvIII+PTEN-glioblastoma in vivo

There are still unmet medical needs for the treatment of glioblastoma (GBM), the most frequent and aggressive brain tumor worldwide. EGFRvIII, overexpressed in approximately 30% of GBM, has been regarded as a potential therapeutic target. In this study, we demonstrated that CH12, an anti-EGFRvIII monoclonal antibody, could significantly suppress the growth of EGFRvIII⁺ GBM in vivo; however, PTEN deficiency in GBM reduced the efficacy of CH12 by attenuating its effect on PI3K/AKT/mTOR pathway. To overcome this problem, CH12 was combined with the mTOR inhibitor rapamycin, leading to a synergistic inhibitory effect on EGFRvIII⁺PTEN⁻ GBM in vivo. Mechanistically, the synergistic antitumor effect was achieved via attenuating EGFR and PI3K/AKT/mTOR pathway more effectively and reversing the STAT5 activation caused by rapamycin treatment. Moreover, the combination therapy suppressed angiogenesis and induced cancer cell apoptosis more efficiently. Together, these results indicated that CH12 and rapamycin could synergistically suppress the growth of EGFRvIII⁺PTEN⁻ GBM, which might have a potential clinical application in the future.

Peptide-Au Cluster Probe: Precisely Detecting Epidermal Growth Factor Receptor of Three Tumor Cell Lines at a Single-Cell Level

Alterations in protein (e.g., biomarkers) expression levels have a significant correlation with tumor development and prognosis; therefore, it is desired to develop precise methods to differentiate the expression level of proteins in tumor cell lines, especially at the single-cell level. Here, we report a precise and versatile approach of quantifying the protein expression levels of three tumor cell lines in situ using a peptide-Au cluster probe. The probe (Au₅Peptide₃) consists of a peptide with a specific cell membrane epidermal growth factor receptor (EGFR) targeting ability and an Au cluster for both cell membrane EGFR imaging using confocal microscopy and cell membrane EGFR counting by laser ablation inductively coupled plasma mass spectrometry. Utilizing the peptide-Au cluster probe, we successfully quantify the EGFR expression levels of SMMC-7721, KB, and HeLa cells at a single-cell level and differentiate the EGFR expression levels among these cell lines. The peptide-Au cluster probe, with the ability to differentiate the protein expression level of different cell lines, shows exceptional promise for providing reliable predictive and prognostic information of tumors at a single-cell level.

Synergistic antitumor efficacy against the EGFRvIII+HER2+ breast cancers by combining trastuzumab with anti-EGFRvIII antibody CH12

Although Trastuzumab, an anti-HER2 antibody, benefits certain patients with HER2-overexpressing breast cancer, de novo or acquired trastuzumab resistance remains a haunting issue. EGFRvIII, co-expressing with HER2 in some breast tumors, indicates a poor clinical prognosis. However, the role of EGFRvIII in the function of trastuzumab is not clear. Here, we demonstrated that EGFRvIII overexpression contributed to de novo trastuzumab resistance and the feedback activation of STAT3 caused by trastuzumab also resulted in acquired resistance in EGFRvIII(+)HER2(+) breast cancers. CH12, a highly effective anti-EGFRvIII monoclonal antibody that preferentially binds to EGFRvIII, significantly suppressed the growth of EGFRvIII+HER2(+) breast cancer cells in vitro and in vivo. Importantly, CH12 in combination with trastuzumab had a synergistic inhibitory effect on EGFRvIII(+)HER2(+) breast cancers in vitro and in vivo via attenuating the phosphorylation of EGFR and HER2 and their downstream signal pathways more effectively and reversing STAT3 feedback activation. Moreover, the combination therapy suppressed angiogenesis and induced cell apoptosis significantly. Together, these results suggested a synergistic efficacy of the combination of trastuzumab with CH12 against EGFRvIII(+)HER2(+) breast cancers, which might be a potential clinical application in the future.

GRP78 confers the resistance to 5-FU by activating the c-Src/LSF/TS axis in hepatocellular carcinoma

5-FU is a common first-line chemotherapeutic drug for the treatment of hepatocellular carcinoma. However the development of acquired resistance to 5-FU confines its clinical usages. Although this phenomenon has been the subject of intense investigation, the exact mechanism of acquired resistance to 5-FU remains elusive. Here, we report that over-expression of GRP78 contributes to acquired resistance to 5-FU in HCC by up-regulating the c-Src/LSF/TS axis. Moreover, we found that the resistance to 5-FU conferred by GRP78 is mediated by its ATPase domain. The ATPase domain differentially increased the expression of LSF, TS and promoted the phosphorylation of ERK and Akt. We further identified that GRP78 interacts physically with c-Src through its ATPase domain and promotes the phosphorylation of c-Src, which in turn increases the expression of LSF in the nucleus. Together, GRP78 confers the resistance to 5-FU by up-regulating the c-Src/LSF/TS axis via its ATPase domain.

EGFR Signaling in Liver Diseases

The epidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase that is activated by several ligands leading to the activation of diverse signaling pathways controlling mainly proliferation, differentiation, and survival. The EGFR signaling axis has been shown to play a key role during liver regeneration following acute and chronic liver damage, as well as in cirrhosis and hepatocellular carcinoma (HCC) highlighting the importance of the EGFR in the development of liver diseases. Despite the frequent overexpression of EGFR in human HCC, clinical studies with EGFR inhibitors have so far shown only modest results. Interestingly, a recent study has shown that in human HCC and in mouse HCC models the EGFR is upregulated in liver macrophages where it plays a tumor-promoting function. Thus, the role of EGFR in liver diseases appears to be more complex than what anticipated. Further studies are needed to improve the molecular understanding of the cell-specific signaling pathways that control disease development and progression to be able to develop better therapies targeting major components of the EGFR signaling network in selected cell types. In this review, we compiled the current knowledge of EGFR signaling in different models of liver damage and diseases, mainly derived from the analysis of HCC cell lines and genetically engineered mouse models (GEMMs).

5-Fluorouracil derivatives: a patent review (2012 - 2014)

INTRODUCTION

5-Fluorouracil (5-FU)-based chemotherapy is the most widely prescribed treatment for gastrointestinal solid tumors, but there are several drawbacks such as toxicities, lack of selectivity and effectiveness as well as the development of resistance that need to be overcome.

AREAS COVERED

In this review, the authors present the latest innovations in 5-FU derivatives or combinations with: i) other chemotherapeutic drugs; ii) novel targeted compounds; iii) radiotherapy; iv) mAbs; v) siRNA strategies; and vi) traditional Chinese medicine extracts. Moreover, advances to overcome or determine 5-FU adverse effects and effectiveness are described. Finally, the authors introduce the ongoing clinical trials and highlight the main challenges to be addressed in the future.

EXPERT OPINION

Although in the past few years there has been a great advancement in the antitumor effectiveness and selectivity of 5-FU-based therapies, it is envisaged that future approaches using 'omics' technologies that could determine the tumor heterogeneity may help in identifying additional candidate genes, microRNAs or cytokines involved in both the path mechanisms of 5-FU-related toxicity and its therapeutic efficacy. Moreover, the development of novel targeted 5-FU derivatives or 5-FU-based therapies tailored to individual patients opens up new possibilities in the improvement of the quality of life and survival for those suffering from this devastating disease.

Synergistic effect of puerarin and 5-fluorouracil on hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common types of human malignancy worldwide, which is becoming increasingly resistant to traditional drug treatments. Puerarin combined with 5-fluorouracil (5-FU) may be a useful treatment for liver cancer. The primary aim of the present study was to determine whether combined treatment with 5-FU and puerarin is more effective against the hepatocellular carcinoma (HCC) cell line, SMMC7721, than treatment with 5-FU or puerarin alone. The growth inhibition of SMMC7721 cells by puerarin or 5-FU alone or in combination was determined by the Cell Counting Kit-8 assay, in vitro. Apoptotic morphological features and the percentage of apoptotic cells were detected using Hoechst 33258 staining and an Annexin V/PI apoptosis kit, respectively. In addition, a tumor xenograft model was established in nude mice using SMMC7721 cells. Puerarin and 5-FU alone or in combination were injected into the mice, and the inhibition of tumor growth was evaluated by monitoring tumor volume and weight. Treatment with 6,400 or 640 μM 5-FU resulted in growth inhibition of 95.56±0.81 and 75.91±3.54%, respectively. The combination index values were <1 when the fraction of affected cells was between 0.2555 and 0.7420. Furthermore, the percentage of apoptotic cells was markedly increased in the combined treatment group when compared with that of the individual treatment groups, in vitro and in vivo. Individual treatment with puerarin resulted in a tumor volume inhibition rate (IR) of 70.58% and a tumor weight IR of 46.20%. Treatment with 5-FU was found to decrease the tumor volume by 76.26% and tumor weight by 49.86%. In the combined treatment group, the tumor volume and weight IRs were 93.11 and 75.21%, respectively. A marked increase in the inhibition of tumor growth and the number of apoptotic cells in response to combined treatment with puerarin and 5-FU was identified with no observed liver or renal toxicity. These results suggest that puerarin and 5-FU exhibit a synergistic treatment effect on the HCC SMMC7721 cell line.

The EGFR signalling system in the liver: from hepatoprotection to hepatocarcinogenesis

The liver displays an outstanding wound healing and regenerative capacity unmatched by any other organ. This reparative response is governed by a complex network of inflammatory mediators, growth factors and metabolites that are set in motion in response to hepatocellular injury. However, when liver injury is chronic, these regenerative mechanisms become dysregulated, facilitating the accumulation of genetic alterations leading to unrestrained cell proliferation and the development of hepatocellular carcinoma (HCC). The epidermal growth factor receptor (EGFR or ErbB1) signaling system has been identified as a key player in all stages of the liver response to injury, from early inflammation and hepatocellular proliferation to fibrogenesis and neoplastic transformation. The EGFR system engages in extensive crosstalk with other signaling pathways, acting as a true signaling hub for other growth factors, cytokines and inflammatory mediators. Here, we briefly review essential aspects of the biology of the EGFR, the other ErbB receptors, and their ligands in liver injury, regeneration and HCC development. Some aspects of the preclinical and clinical experience with EGFR therapeutic targeting in HCC are also discussed.

The monoclonal antibody CH12 augments 5-fluorouracil-induced growth suppression of hepatocellular carcinoma xenografts expressing epidermal growth factor receptor variant III

5-Fluorouracil (5-FU) is one of the most common chemotherapeutic agents used for the treatment of hepatocellular carcinoma (HCC). However, chemoresistance has precluded the use of 5-FU alone in clinical regimens. Combination therapies with 5-FU and other anticancer agents are considered to be a therapeutic option for patients with HCC. We previously reported that the expression of epidermal growth factor receptor variant III (EGFRvIII) can decrease the sensitivity of HCC cells to 5-FU. To overcome this problem, in this study, we elucidated the mechanism underlying EGFRvIII-mediated 5-FU resistance. We observed that EGFRvIII expression can induce miR-520d-3p downregulation and the ensuing upregulation of the transcription factor E2F-1 and the enzyme thymidylate synthase (TS), which may lead to drug resistance. Intriguingly, we found that CH12, a monoclonal antibody directed against EGFRvIII, and 5-FU together had an additive antitumor effect on EGFRvIII-positive HCC xenografts and significantly improved survival in all mice with established tumors when compared with either 5-FU or CH12 alone. Mechanistically, compared with 5-FU alone, the combination more noticeably downregulated EGFR phosphorylation and Akt phosphorylation as well as the expression of the apoptotic protector Bcl-xL and the cell cycle regulator cyclin D1. Additionally, the combination upregulated the expression of the cell cycle inhibitor p27 in in vivo treatment. More interestingly, CH12 treatment upregulated miR-520-3p and downregulated E2F-1 and TS at the mRNA and protein levels. Collectively, these observations suggest that the combination of 5-FU with mAb CH12 is a potential means of circumventing EGFRvIII-mediated 5-FU resistance in HCC.

The monoclonal antibody CH12 enhances the sorafenib-mediated growth inhibition of hepatocellular carcinoma xenografts expressing epidermal growth factor receptor variant III

The multikinase inhibitor sorafenib is the first oral agent to show activity against human hepatocellular carcinoma (HCC). Although the clinical application of sorafenib has shown good tolerability in the studied populations, it also causes multiple human dose-limiting toxicities. Thus, there is a strong need to reduce the overall dose of sorafenib. We have reported that the epidermal growth factor receptor variant III (EGFRvIII) expression can decrease the sensitivity of HCC cells to chemotherapeutic drugs. Therefore, we sought to explore whether EGFRvIII can affect the sensitivity of HCC cells to sorafenib. In this study, we observed that EGFRvIII expression significantly decreased the sensitivity of HCC cells to sorafenib. To enhance the antitumor effect and reduce the overall dose of sorafenib, we evaluated the combined effects of CH12, a monoclonal antibody against EGFRvIII, and sorafenib on the growth of HCC cells expressing EGFRvIII in vitro and in vivo. The results showed that, when CH12 was combined with sorafenib, the tumor growth suppression effect was significantly increased, and the concentration of sorafenib required for growth inhibition was substantially reduced. Mechanistically, the combination could more noticeably downregulate the phosphorylation of constitutively active extracellular signal-regulated kinase (ERK), Akt (Thr308), and signal transducer and activator of transcription 3 (STAT3) than sorafenib alone. Collectively, these findings demonstrate that CH12 interacts additively with sorafenib to strongly inhibit the tumor growth of HCC xenografts expressing EGFRvIII by enhancing the sorafenib-mediated inhibition of the MEK/ERK, phosphoinositide 3-kinase/AKT, and STAT3 pathways.

Genetic variants in genes involved in mechanisms of chemoresistance to anticancer drugs

Refractoriness to the pharmacological treatment of cancer is dependent on the expression levels of genes involved in mechanisms of chemoresistance and on the existence of genetic variants that may affect their function. Thus, changes in genes encoding solute carriers may account for considerable inter-individual variability in drug uptake and the lack of sensitivity to the substrates of these transporters. Moreover, changes in proteins involved in drug export can affect their subcellular localization and transport ability and hence may also modify the bioavailability of antitumor agents. Regarding pro-drug activation or drug inactivation, genetic variants are responsible for changes in the activity of drug-metabolizing enzymes, which affect drug clearance and may determine the lack of response to anticancer chemotherapy. The presence of genetic variants may also decrease the sensitivity to pharmacological agents acting through molecular targets or signaling pathways. Recent investigations suggest that changes in genes involved in DNA repair may affect the response to platinum-based drugs. Since most anticancer agents activate cell death pathways, the evasion of apoptosis plays an important role in chemoresistance. Several genetic variants affecting death-receptor pathways, the mitochondrial pathway, downstream caspases and their natural modulators, and the p53 pathway, whose elements are mutated in more than half of tumors, and survival pathways, have been reported. The present review summarizes the available data regarding the role of genetic variants in the different mechanisms of chemoresistance and discusses their potential impact in clinical practice and in the development of tools to predict and overcome chemoresistance.

Phosphorylation of epidermal growth factor receptor and chromosome 7 polysomy in gastric adenocarcinoma

OBJECTIVE

To investigate the phosphorylation of epidermal growth factor receptor (EGFR) and its potentially associated chromosomal aberrations in gastric adenocarcinoma.

METHODS

Phosphorylated EGFR (pEGFR) was detected by immunohistochemistry on 145 specimens including 60 tumoral, 60 non-tumoral, 12 tumor-adjacent intramucosal dysplasia from patients with gastric adenocarcinoma and 13 mucosae from cancer-free patients. EGFR gene amplification and chromosome 7 (Chr-7) polysomy were detected by fluorescence in situ hybridization.

RESULTS

Positivity of pEGFR was found in 50 tumoral (83.3%) and 42 non-tumoral specimens (70.0%). There was an association between tumoral and non-tumoral zones on immunostains of pEGFR (r = 0.353, P = 0.006). Nuclear pEGFR usually presented in mucosae with Helicobacter pylori infection, stromal reaction or vascular invasion. Cytoplasmic pEGFR was correlated with local cancer extension (r = 0.337, P = 0.014) and inversely related with gastrokine 2, which had been previously detected in the same specimens. Eleven intramucosal dysplastic specimens were also positive for pEGFR while 13 mucosae from cancer-free patients were all negative. No EGFR gene amplification was observed. However, seven tumor specimens showed Chr-7 polysomy (11.7%) in which 5 were strongly positive for pEGFR.

CONCLUSIONS

EGFR phosphorylation may be one of the mechanisms that promote tumor initiation and expansion in gastric adenocarcinoma. Detection of pEGFR with analysis of its nuclear or cytoplasmic patterns could be clinicopathologically valuable. Chr-7 polysomy may partially contribute to EGFR activation in gastric adenocarcinoma, although its role does not predominate.

Green tea polyphenol epigallocatechin-3-gallate enhances 5-fluorouracil-induced cell growth inhibition of hepatocellular carcinoma cells

AIM

  5-Fluorouracil (5-FU) is one of the most commonly used chemotherapeutic drugs. Resistance to 5-FU is a major cause of chemotherapy failure in advanced-stage hepatocellular carcinoma (HCC). Green tea polyphenol Epigallocatechin-3-gallate (EGCG) plays a critical role in growth inhibition and apoptotic induction in HCC cell lines. The aim of this study is to investigate whether EGCG can enhance 5-FU-induced cell growth inhibition and to explore its potential mechanisms.

METHODS

  3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to evaluate cell growth. Western blotting analysis was performed to detect the proteins expression in Hep3B cells. Small interfering RNA was used to suppress cyclooxygenase-2 (COX-2) expression. Furthermore, enzyme linked immunosorbent assay was used to test the prostaglandin E(2) (PGE(2) ) production in cell cultures.

RESULTS

  Epigallocatechin-3-gallate augmented the anti-tumor effect of 5-FU in Hep3B cells. Significant difference was observed between the treated groups and the control group (P < 0.05). EGCG (its concentrations at over 5 µmol/L) combined with 5-FU presented a synergic effect. Furthermore, the combination of EGCG and 5-FU abrogated the COX-2 overexpression and PGE(2) secretion induced by 5-FU. The upregulation of COX-2 expression decreased the phosphorylation of Akt (Thr(308) ) expression. These appeared to be followed by the AMPK hyperactivation.

CONCLUSION

  Epigallocatechin-3-gallate sensitizes HCC cells to 5-FU antitumor activity, and the combination of EGCG and 5-FU exhibits synergism in chemo-resistant cancer cells. The results suggest potential novel therapies for the treatment of advanced-stage liver cancer.

The major vault protein mediates resistance to epidermal growth factor receptor inhibition in human hepatoma cells

To better understand the response of HCC to EGFR inhibition, we analyzed factors connected to the resistance of HCC cells against gefitinib. Sensitive HCC3 cells co-expressed EGFR and ErbB3 but lacked kinase-domain mutations in EGFR. Interestingly, expression of MVP was restricted to resistant cell lines, whereas ABCB1 and ABCC1 showed no association with gefitinib resistance. Moreover, ectopic MVP expression in HCC3 cells decreased gefitinib sensitivity, increased AKT phosphorylation and reduced the expression of inflammatory pathway-associated genes, whereas silencing of MVP in Hep3B and HepG2 cells increased sensitivity. These findings suggest MVP as a novel player in resistance against EGFR inhibition.

An oligopeptide ligand-mediated therapeutic gene nanocomplex for liver cancer-targeted therapy

The epidermal growth factor receptor (EGFR) is over-expressed in a wide variety of epithelial-derived cancer cells. In this study, EGFR-targeted gene carriers were designed to complex the therapeutic acetylcholinesterase gene (AChE gene), which suppresses cell proliferation via inactivating mitogen-activated protein kinase and PI3K/Akt pathways in cells, for treatment of EGFR-positive liver cancers. Different amounts of target ligand YC21 (an oligopeptide composed of 21 amino acid units) were coupled with the PEI(600)-CD (PC) vectors composed of β-cyclodextrin (β-CD) and low-molecular-weight polyethylenimine (PEI, Mw 600) to form the EGFR-targeted gene vectors (termed as YPCs). The YPC vectors possessed the highly efficient gene delivery ability to the EGFR-positive liver cancer cells. YPCs could effectively promote AChE gene expression. The YPC/AChE complexes produced excellent gene transfection abilities in EGFR-positive liver cancer cells in vitro and in vivo.

Identification of an exon 4-deletion variant of epidermal growth factor receptor with increased metastasis-promoting capacity

Several types of epidermal growth factor receptor (EGFR) gene alternations have been observed in human tumors. Here we present a novel EGFR variant with aberrant splicing of exon 4 (named as de4 EGFR). Variant-specific polymerase chain reaction showed that de4 EGFR was expressed in some glioma (4/40), prostate cancer (3/11), and ovarian cancer (3/9) tissues but not in tissues adjacent to tumors or normal tissues. de4 EGFR displayed an enhanced transformation and a higher metastasis-promoting capacity in comparison to wild-type EGFR. With minimal EGF-binding activity, de4 EGFR underwent ligand-independent autophosphorylation and self-dimerization. Moreover, in serum-starved condition, de4 EGFR expression in U87 MG cells significantly upregulated the extracellular signal-regulated kinase and AKT phosphorylation and expression of JUN and Src. Importantly, E-cadherin expression was barely detectable in the U87 MG cells expressing de4 EGFR and restored expression of E-cadherin in these cells inhibited their metastatic behaviors. Taken together, we identified a novel EGFR variant with increased metastasis-promoting activity that may become a promising new target for cancer therapy.

A monoclonal antibody targeted against epidermal growth factor receptor variant III enhances cisplatin efficiency

PURPOSE

To investigate the effect of a monoclonal antibody (CH12), targeted against epidermal growth factor receptor type III variant (EGFRvIII), on human ovarian cancer cells when administered in combination with cisplatin chemotherapy.

METHODS

Western blot and reverse transcription polymerase chain reaction (RT-PCR) were used to determine the expression levels of EGFRvIII protein and mRNA, respectively, in the ovarian cancer cell lines SK-OV-3 and CAOV-3. Cells were left untreated or treated with either cisplatin or CH12 alone or both agents in combination (2 μg/ml cisplatin plus CH12). Cell proliferation was detected in a CCK-8 assay. The binding affinities of the CH12 mAb to the 2 cell lines were analyzed; after treatment with cisplatin and different concentrations of CH12, the apoptotic ratios and cell cycle stages of SK-OV-3 cells were determined by flow cytometry (FCM).

RESULTS

The express of EGFRvIII mRNA and protein in the two ovarian cancer cell lines were both detected. Analysis of the combination index yielded a value of 0.915, indicating that 2 drugs have a synergistic therapeutic effect. SK-OV-3 cells were observed to be much more resistant to cisplatin than CAOV-3 cells. The primary combinatorial effect of the 2 drugs was the induction of apoptosis, but we also observed synergic co-inhibition of the cell cycle of SK-OV-3 in the S phase.

CONCLUSIONS

We conclude that CH12 antibody is a promising candidate for clinical therapy for ovarian cancer cells, which has lower sensitivity to cisplatin treatment; however, the underlying mechanism needs further study.

Metronomic S-1 chemotherapy and vandetanib: an efficacious and nontoxic treatment for hepatocellular carcinoma

BACKGROUND

Metronomic chemotherapy involves frequent, regular administration of cytotoxic drugs at nontoxic doses, usually without prolonged breaks. We investigated the therapeutic efficacies of metronomic S-1, an oral 5-fluorouracil prodrug, and vandetanib, an epidermal growth factor receptor and vascular endothelial growth factor (VEGF) receptor tyrosine kinase inhibitor, in models of hepatocellular carcinoma (HCC).

METHODS

We compared anti-HCC effects and toxicity in the six treatment groups: control (untreated), maximum tolerated dose (MTD) S-1, metronomic S-1, vandetanib, MTD S-1 with vandetanib, and metronomic S-1 with vandetanib. Tumor microvessel density (MVD) and tumor apoptosis were evaluated by immunohistochemistry. The expression of VEGF and thrombospondin-1, an endogenous inhibitor of angiogenesis, was analyzed by Western blot.

RESULTS

Metronomic S-1 significantly inhibited tumor growth, which was enhanced by combination with vandetanib. With respect to toxicities, MTD S-1 caused severe body weight loss and myelosuppression, whereas metronomic S-1 did not cause any overt toxicities. Moreover, metronomic S-1 or metronomic S-1 with vandetanib prolonged survival, the latter treatment providing the greatest benefit. Metronomic S-1 and metronomic S-1 with vandetanib decreased MVDs and increased apoptosis in tumor tissues. The expression of VEGF in tumor tissues was upregulated by vandetanib and metronomic S-1 with vandetanib, whereas the expression of thrombospondin-1 was upregulated by metronomic S-1 and metronomic S-1 with vandetanib.

CONCLUSION

Metronomic S-1 with an antiangiogenic agent seems to be an effective and safe therapeutic strategy for HCC.

Epidermal Growth Factor Receptor (EGFR) Crosstalks in Liver Cancer

Hepatocarcinogenesis is a complex multistep process in which many different molecular pathways have been implicated. Hepatocellular carcinoma (HCC) is refractory to conventional chemotherapeutic agents, and the new targeted therapies are meeting with limited success. Interreceptor crosstalk and the positive feedback between different signaling systems are emerging as mechanisms of targeted therapy resistance. The identification of such interactions is therefore of particular relevance to improve therapeutic efficacy. Among the different signaling pathways activated in hepatocarcinogenesis the epidermal growth factor receptor (EGFR) system plays a prominent role, being recognized as a “signaling hub” where different extracellular growth and survival signals converge. EGFR can be transactivated in response to multiple heterologous ligands through the physical interaction with multiple receptors, the activity of intracellular kinases or the shedding of EGFR-ligands. In this article we review the crosstalk between the EGFR and other signaling pathways that could be relevant to liver cancer development and treatment.

Bioprocess development for the production of mouse-human chimeric anti-epidermal growth factor receptor vIII antibody C12 by suspension culture of recombinant Chinese hamster ovary cells

The mouse-human chimeric anti-epidermal growth factor receptor vIII (EGFRvIII) antibody C12 is a promising candidate for the diagnosis of hepatocellular carcinoma (HCC). In this study, 3 processes were successfully developed to produce C12 by cultivation of recombinant Chinese hamster ovary (CHO-DG44) cells in serum-free medium. The effect of inoculum density was evaluated in batch cultures of shaker flasks to obtain the optimal inoculum density of 5 × 10(5) cells/mL. Then, the basic metabolic characteristics of CHO-C12 cells were studied in stirred bioreactor batch cultures. The results showed that the limiting concentrations of glucose and glutamine were 6 and 1 mM, respectively. The culture process consumed significant amounts of aspartate, glutamate, asparagine, serine, isoleucine, leucine, and lysine. Aspartate, glutamate, asparagine, and serine were particularly exhausted in the early growth stage, thus limiting cell growth and antibody synthesis. Based on these findings, fed-batch and perfusion processes in the bioreactor were successfully developed with a balanced amino acid feed strategy. Fed-batch and especially perfusion culture effectively maintained high cell viability to prolong the culture process. Furthermore, perfusion cultures maximized the efficiency of nutrient utilization; the mean yield coefficient of antibody to consumed glucose was 44.72 mg/g and the mean yield coefficient of glutamine to antibody was 721.40 mg/g. Finally, in small-scale bioreactor culture, the highest total amount of C12 antibody (1,854 mg) was realized in perfusion cultures. Therefore, perfusion culture appears to be the optimal process for small-scale production of C12 antibody by rCHO-C12 cells.

Growth suppression of human hepatocellular carcinoma xenografts by a monoclonal antibody CH12 directed to epidermal growth factor receptor variant III

Human hepatocellular carcinoma (HCC) is considered difficult to cure because it is resistant to radio- and chemotherapy and has a high recurrence rate after curative liver resection. Epidermal growth factor receptor variant III (EGFRvIII) has been reported to express in HCC tissues and cell lines. This article describes the efficacy of an anti-EGFRvIII monoclonal antibody (mAb CH12) in the treatment of HCC xenografts with EGFRvIII expression and the underlying mechanism of EGFRvIII as an oncogene in HCC. The results demonstrated that CH12 bound preferentially to EGFRvIII with a dissociation constant (K(d)) of 1.346 nm/liter. In addition, CH12 induces strong antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity in Huh7-EGFRvIII (with exogenous expression of EGFRvIII) and SMMC-7721 (with endogenous expression of EGFRvIII) cells. Notably, CH12 significantly inhibited the growth of Huh7-EGFRvIII and SMMC-7721 xenografts in vivo with a growth inhibition ratio much higher than C225, a U. S. Food and Drug Administration-approved anti-EGFR antibody. Treatment of the two HCC xenografts with CH12 significantly suppressed tumor proliferation and angiogenesis. Mechanistically, in vivo treatment with CH12 reduced the phosphorylation of constitutively active EGFRvIII, Akt, and ERK. Down-regulation of the apoptotic protectors Bcl-x(L), Bcl-2, and the cell cycle regulator cyclin D1, as well as up-regulation of the cell-cycle inhibitor p27, were also observed after in vivo CH12 treatment. Collectively, these results indicate that the monoclonal antibody CH12 is a promising therapeutic agent for HCC with EGFRvIII expression.

Identification and characterization of Ch806 mimotopes

The chimeric antibody 806 (Ch806) is a promising antitumor agent that recognizes both the epidermal growth factor receptor variant III (EGFRvIII) and the overexpressed epidermal growth factor receptor (EGFR) in cancer tissues but does not recognize the wild type EGFR in normal tissues. However, passive antibody immunization could not produce effective antitumor titers unless the immunization was administered repeatedly over long periods. To overcome this limitation, we generated epitope mimics that bind to Ch806 and tested whether the peptide mimics could induce the production of similar antibodies when actively immunizing mice with the peptides. We used the PH.D-12 phage display peptide library to identify peptides that bind to the monoclonal antibody (mAb) 12H23, which also recognizes similar epitopes of Ch806. Two mimotopes (WHTEILKSYPHE and LPAFFVTNQTQD) were shown to mimic the mAb 12H23 and Ch806 epitope using immunoassays. The mimotopes were conjugated to immunogenic carrier proteins and used to intraperitoneally immunize BALB/c mice. Interestingly, sera from the mice immunized with the isolated mimotopes not only recognize the recombinant or synthetic 806 eptitope, but can also recognize EGFR that is overexpressed in A431 cells and EGFRvIII expressed in Huh7-EGFRvIII cells, whereas sera from mice immunized with the control peptide-KLH (keyhole limpet hemocyanin) and carrier KLH alone failed to show a similar reactivity. Furthermore, in an antibody-dependent cellular cytotoxicity assay (ADCC), the mimotope-induced antibodies specifically lysed human Huh-7-EGFRvIII cells. Our data indicate that the isolated mimotopes reported here may potentially be used as new alternative agents for treating cancer with EGFRvIII expression or EGFR overexpression.

TRAIL-induced apoptosis of hepatocellular carcinoma cells is augmented by targeted therapies

AIM: To analyze the effect of chemotherapeutic drugs and specific kinase inhibitors, in combination with the death receptor ligand tumor necrosis factor-related apoptosis inducing ligand (TRAIL), on overcoming TRAIL resistance in hepatocellular carcinoma (HCC) and to study the efficacy of agonistic TRAIL antibodies, as well as the commitment of antiapoptotic BCL-2 proteins, in TRAIL-induced apoptosis.

METHODS: Surface expression of TRAIL receptors (TRAIL-R1-4) and expression levels of the antiapoptotic BCL-2 proteins MCL-1 and BCL-x_L were analyzed by flow cytometry and Western blotting, respectively. Knock-down of MCL-1 and BCL-x_L was performed by transfecting specific small interfering RNAs. HCC cells were treated with kinase inhibitors and chemotherapeutic drugs. Apoptosis induction and cell viability were analyzed via flow cytometry and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

RESULTS: TRAIL-R1 and -R2 were profoundly expressed on the HCC cell lines Huh7 and Hep-G2. However, treatment of Huh7 and Hep-G2 with TRAIL and agonistic antibodies only induced minor apoptosis rates. Apoptosis resistance towards TRAIL could be considerably reduced by adding the chemotherapeutic drugs 5-fluorouracil and doxorubicin as well as the kinase inhibitors LY294002 [inhibition of phosphoinositol-3-kinase (PI3K)], AG1478 (epidermal growth factor receptor kinase), PD98059 (MEK1), rapamycin (mammalian target of rapamycin) and the multi-kinase inhibitor Sorafenib. Furthermore, the antiapoptotic BCL-2 proteins MCL-1 and BCL-x_L play a major role in TRAIL resistance: knock-down by RNA interference increased TRAIL-induced apoptosis of HCC cells. Additionally, knock-down of MCL-1 and BCL-x_L led to a significant sensitization of HCC cells towards inhibition of both c-Jun N-terminal kinase and PI3K.

CONCLUSION: Our data identify the blockage of survival kinases, combination with chemotherapeutic drugs and targeting of antiapoptotic BCL-2 proteins as promising ways to overcome TRAIL resistance in HCC.