Acquired resistance to EGFR inhibitors: mechanisms and prevention strategies

TMED2 promotes glioma tumorigenesis by being involved in EGFR recycling transport

Aberrant epidermal growth factor receptor (EGFR) signaling is the core signaling commonly activated in glioma. The transmembrane emp24 protein transport domain protein 2 (TMED2) interacts with cargo proteins involved in protein sorting and transport between endoplasmic reticulum (ER) and Golgi apparatus. In this study, we found the correlation between TMED2 with glioma progression and EGFR signaling through database analysis. Moreover, we demonstrated that TMED2 is essential for glioma cell proliferation, migration, and invasion at the cellular levels, as well as tumor formation in mouse models, underscoring its significance in the pathobiology of gliomas. Mechanistically, TMED2 was found to enhance EGFR-AKT signaling by facilitating EGFR recycling, thereby providing the initial evidence of TMED2's involvement in the membrane protein recycling process. In summary, our findings shed light on the roles and underlying mechanisms of TMED2 in the regulation of glioma tumorigenesis and EGFR signaling, suggesting that targeting TMED2 could emerge as a promising therapeutic strategy for gliomas and other tumors associated with aberrant EGFR signaling.

A promising anoikis-related prognostic signature predicts prognosis of skin cutaneous melanoma

BACKGROUND

Skin cutaneous melanoma (SKCM) is a highly aggressive disease with a poor prognosis for advanced tumors. Anoikis is a caspase-dependent cell death process triggered by extracellular matrix (ECM) detachment, rectifies detachment-induced metabolic defects that compromise cell survival, recent study revealed the crucial role of anoikis for cancer cells to survive during metastasis. However, limited research focused on the role of anoikis in SKCM.

METHODS

Our study utilized the 27 anoikis-related genes (ARGs) to divide SKCM patients into two clusters, and obtain differentially expressed genes (DEGs) for each cluster. These DEGs were used in stepwise Cox regression analysis to develop a prediction model for SKCM patients consisting of nine ARGs, called the anoikis-related signature (ARS). Subsequently, we used the risk scores calculated from the ARS to divide SKCM patients into two groups and explored differences in immune microenvironment, immune checkpoint reactivity, and drug sensitivity between the groups.

RESULTS

Nine ARGs were identified to stratify SKCM patients into two risk groups, patients in the high-risk group had a poor prognosis and suppressed immune cell infiltration. Moreover, higher expression of immune checkpoint molecules and a greater sensitivity to immunotherapy and chemotherapy drugs were observed in the low-risk group. Finally, all of the ARS hub genes were found to be upregulated in SKCM tissues and cell lines.

CONCLUSION

A novel ARGs signature was identified for predicting the prognosis of SKCM. Based on the immune landscape associated with ARS discovered in our study, targeting ARS hub genes may be a promising treatment for SKCM.

Combination Therapy as a Promising Way to Fight Oral Cancer

Oral cancer is a highly aggressive tumor with invasive properties that can lead to metastasis and high mortality rates. Conventional treatment strategies, such as surgery, chemotherapy, and radiation therapy, alone or in combination, are associated with significant side effects. Currently, combination therapy has become the standard practice for the treatment of locally advanced oral cancer, emerging as an effective approach in improving outcomes. In this review, we present an in-depth analysis of the current advancements in combination therapies for oral cancer. The review explores the current therapeutic options and highlights the limitations of monotherapy approaches. It then focuses on combinatorial approaches that target microtubules, as well as various signaling pathway components implicated in oral cancer progression, namely, DNA repair players, the epidermal growth factor receptor, cyclin-dependent kinases, epigenetic readers, and immune checkpoint proteins. The review discusses the rationale behind combining different agents and examines the preclinical and clinical evidence supporting the effectiveness of these combinations, emphasizing their ability to enhance treatment response and overcome drug resistance. Challenges and limitations associated with combination therapy are discussed, including potential toxicity and the need for personalized treatment approaches. A future perspective is also provided to highlight the existing challenges and possible resolutions toward the clinical translation of current oral cancer therapies.

The mechanism of action and biodistribution of a novel EGFR/VEGF bispecific fusion protein that exhibited superior antitumor activities

Despite the promising clinical benefits of therapies targeting epidermal growth factor receptor (EGFR) or vascular endothelial growth factor (VEGF) with antibodies in various cancers, resistance to these therapies will inevitably develop following treatment. Recent studies suggest that crosstalk between the EGFR and VEGF signaling pathways might be involved in the development of resistance. Therefore, simultaneous blockade of EGFR and VEGF signaling may be able to counteract this resistance and improve clinical outcomes. Here, we devised a fusion protein with two copies of VEGFR1 domain 2 connected to the C-terminus of cetuximab that can simultaneously bind to EGFR and VEGF and effectively inhibit target cell growth mediated by these two pathways. Furthermore, the fusion protein could bring soluble VEGF into target cells for degradation through internalization upon binding to EGFR. Tissue distribution in mice confirmed that the fusion protein effectively accumulated in tumors compared to its mAb counterpart cetuximab. These features resulted in stronger antitumor efficacies in vivo than the combination of bevacizumab and cetuximab. Thus, we provide a promising new strategy for the treatment of EGFR-overexpressing cancers.

Antitumor effects of erlotinib in combination with berberine in A431 cells

BACKGROUND

First-generation epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), such as erlotinib, have been shown to target tumors with L858R (exon 21) and exon 19 deletions, resulting in significant clinical benefits. However, acquired resistance often occurs due to EGFR mutations. Therefore, novel therapeutic strategies for treatment of patients with EGFR-positive tumors are needed. Berberine (BBR) is an active alkaloid extracted from pharmaceutical plants such as Coptis chinensis. Berberine has been shown to significantly inhibit EGFR activity and mediate anticancer effects in multiple preclinical studies. We investigated whether combining BBR with erlotinib could augment erlotinib-induced cell growth inhibition of EGFR-positive cells in a mouse xenograft model.

METHODS

We examined the antitumor activities and potential mechanisms of erlotinib in combination with berberine in vitro and in vivo using the MTT assay, immunoblotting, flow cytometry, and tumor xenograft models.

RESULTS

In vitro studies with A431 cells showed that synergistic cell growth inhibition by the combination of BBR and erlotinib was associated with significantly greater inhibition of pEGFR and pAKT, and inhibition of cyclin D and Bcl-2 expression compared to that observed in response to BBR or erlotinib alone. The efficacy of the combination treatment was also investigated in nude mice. Consistent with the in vitro results, BBR plus erlotinib significantly reduced tumor growth.

CONCLUSION

Our data supported use of BBR in combination with erlotinib as a novel strategy for treatment of patients with EGFR positive tumors.

Dual inhibition of EGFR‑VEGF: An effective approach to the treatment of advanced non‑small cell lung cancer with EGFR mutation (Review)

On a global scale, the incidence and mortality rates of lung cancer are gradually increasing year by year. A number of bad habits and environmental factors are associated with lung cancer, including smoking, second‑hand smoke exposure, occupational exposure, respiratory diseases and genetics. At present, low‑dose spiral computed tomography is routinely the first choice in the diagnosis of lung cancer. However, pathological examination is still the gold standard for the diagnosis of lung cancer. Based on the classification and stage of the cancer, treatment options such as surgery, radiotherapy, chemotherapy, targeted therapy and immunotherapy are available. The activation of the EGFR pathway can promote the survival and proliferation of tumor cells, and the VEGF pathway can promote the formation of blood vessels, thereby promoting tumor growth. In non‑small cell lung cancer (NSCLC) with EGFR mutation, EGFR activation can promote tumor growth by promoting VEGF upregulation through a hypoxia‑independent mechanism. The upregulation of VEGF can make tumor cells resistant to EGFR inhibitors. In addition, the expression of the VEGF signal is also affected by other factors. Therefore, the use of a single EGFR inhibitor cannot completely inhibit the expression of the VEGF signal. In order to overcome this problem, the combination of VEGF inhibitors and EGFR inhibitors has become the method of choice. Dual inhibition can not only overcome the resistance of tumor cells to EGFR inhibitors, but also significantly increase the progression‑free survival time of patients with NSCLC. The present review discusses the associations between the EGFR and VEGF pathways, and the characteristics of dual inhibition of the EGFR‑VEGF pathway.

Biomarker LEPRE1 induces pelitinib-specific drug responsiveness by regulating ABCG2 expression and tumor transition states in human leukemia and lung cancer

Biomarkers for treatment sensitivity or drug resistance used in precision medicine include prognostic and predictive molecules, critical factors in selecting appropriate treatment protocols and improving survival rates. However, identification of accurate biomarkers remain challenging due to the high risk of false-positive findings and lack of functional validation results for each biomarker. Here, we discovered a mechanical correlation between leucine proline-enriched proteoglycan 1 (LEPRE1) and pelitinib drug sensitivity using in silico statistical methods and confirmed the correlation in acute myeloid leukemia (AML) and A549 lung cancer cells. We determined that high LEPRE1 levels induce protein kinase B activation, overexpression of ATP-binding cassette superfamily G member 2 (ABCG2) and E-cadherin, and cell colonization, resulting in a cancer stem cell-like phenotype. Sensitivity to pelitinib increases in LEPRE1-overexpressing cells due to the reversing effect of ABCG2 upregulation. LEPRE1 silencing induces pelitinib resistance and promotes epithelial-to-mesenchymal transition through actin rearrangement via a series of Src/ERK/cofilin cascades. The in silico results identified a mechanistic relationship between LEPRE1 and pelitinib drug sensitivity, confirmed in two cancer types. This study demonstrates the potential of LEPRE1 as a biomarker in cancer through in-silico prediction and in vitro experiments supporting the clinical development of personalized medicine strategies based on bioinformatics findings.

Ethoxy-erianin phosphate and afatinib synergistically inhibit liver tumor growth and angiogenesis via regulating VEGF and EGFR signaling pathways

The therapeutic efficacy of tyrosine kinase inhibitors (TKIs) on solid tumors is limited by drug resistance and side effects. Currently, the combination therapy comprises of TKIs and angiogenesis inhibitors have been corroborated as an effective approach in cancer therapy. Ethoxy-erianin phosphate (EBTP) is an anti-angiogenic compound with low toxicity obtained by structural modification of the natural product erianin. Here, we aimed to evaluate whether EBTP can cooperate with TKIs to inhibit the proliferation and angiogenesis of tumor cells and reduce toxic effects. First, CCK-8 results showed that EBTP can effectively inhibit the proliferation of liver cancer cell line HepG2. We combined EBTP with four TKIs (Bosutinib, Apatinib, Afatinib and Erlotinib) to treat HepG2 cells and CompuSyn software analysis suggested that EBTP/Afatinib(Afa)shows the best synergistic inhibitory effect. Meanwhile, EBTP/Afa can significantly suppress the proliferation, invasion, migration and angiogenesis of HepG2 and HUVECs. ELISA results revealed that EBTP/Afa inhibits the secretion of VEGF in HepG2. EBTP/Afa down-regulates the expression of VEGF, p-VEGFR1, p-VEGFR2 and p-EGFR in both HepG2 and HUVECs. Further, the supernatant of HepG2 cells treated with EBTP/Afa blocks the intracellular downstream signal transduction shared by VEGF and EGFR in HUVECs. Finally, EBTP/Afa significantly inhibits tumor growth and angiogenesis in vivo. To conclude, EBTP/Afa targets VEGF and EGFR signaling pathways in liver cancer cells and tumor vasculature, thereby inhibiting the proliferation, motion and angiogenesis of liver cancer cells. Overall, this study provides a new combined strategy for the clinical treatment of hepatocellular carcinoma.

Optimal Sequence and Second-Line Systemic Treatment of Patients with RAS Wild-Type Metastatic Colorectal Cancer: A Meta-Analysis

Although several sequential therapy options are available for treating patients with RAS wild-type (WT) metastatic colorectal cancer (mCRC), the optimal sequence of these therapies is not well established. A systematic review and meta-analysis of 13 randomized controlled trials and 4 observational studies were performed, resulting from a search of the Cochrane Library, PubMed, and Embase databases. Overall survival (OS) did not differ significantly in patients with RAS-WT failure who were administered a second-line regimen of changed chemotherapy (CT) plus anti-epidermal growth factor receptor (EGFR) versus only changed CT, changed CT plus bevacizumab versus changed CT plus anti-EGFR, or changed CT versus maintaining CT plus anti-EGFR after first-line therapy with CT, plus bevacizumab. However, OS was significantly different with a second-line regimen that included changed CT plus bevacizumab, versus only changing CT. Analysis of first-line therapy with CT plus anti-EGFR for treatment of RAS-WT mCRC indicated that second-line therapy of changed CT plus an anti-EGFR agent resulted in better outcomes than changing CT without targeted agents. The pooled data study demonstrated that the optimal choice of second-line treatment for improved OS was an altered CT regimen with retention of bevacizumab after first-line bevacizumab failure. The best sequence for first-to-second-line therapy of patients with RAS-WT mCRC was cetuximab-based therapy, followed by a bevacizumab-based regimen.

Treatments after first progression in metastatic colorectal cancer. A literature review and evidence-based algorithm

Prolonging survival, achieving symptoms palliation and preserving quality of life are the primary therapeutic goals of treatments administered after disease progression in mCRC. Even if the impact of these therapies on the prognosis of affected patients is less relevant than the impact of the upfront treatment, tailoring the optimal second-line therapy is increasingly important. Several therapeutic options are available, and different factors including not only patient- and disease-related characteristics, but also the first-line treatment received (i.e., type, timing of disease progression, observed outcome and reported toxicities) may drive this choice. Herein, we describe the current state of the art in the landscape of treatments after progression in mCRC. Based on a critical review of the literature, we built a patient-oriented therapeutic algorithm, aiming to guide clinicians in their daily decision-making.

Preparation and identification of an anti-idiotypic antibody antagonist (FG8) for EGFR that shows potential activity against liver cancer cells

OBJECTIVE

Currently, there are two categories of epidermal growth factor receptor (EGFR) antagonists, small molecule antagonists and anti-EGFR antibodies. In the current study, we developed a new EGFR antagonist employing the anti-idiotypic antibodies strategy.

RESULTS

First, using EGF as an antigen, through a series of immunological protocols and hybridoma technology, we obtained an anti-idiotypic antibody against EGF receptor-binding epitopes. On this basis, we screened and characterized the anti-idiotype antibodies against EGFR through competitive ELISA, co-localization analysis, competitive receptor binding analysis, and immunofluorescence. Finally, an internal image anti-idiotype antibody called FG8 was successfully prepared. Experiment result shows that FG8 inhibits EGFR-mediated signaling pathways in vitro. Additionally, FG8 inhibits liver tumor cell proliferation as well as induces tumor cell apoptosis.

CONCLUSIONS

The present study suggests that FG8 is a potential therapeutic agent for liver cancer. In addition, this study provides a novel method for the preparation of EGFR antagonists.

LHX6 Affects Erlotinib Resistance and Migration of EGFR-Mutant Non-Small-Cell Lung Cancer HCC827 Cells Through Suppressing Wnt/β-Catenin Signaling

BACKGROUND

miR-214 has been reported to contribute to erlotinib resistance in non-small-cell lung cancer (NSCLC) through targeting LHX6; however, the molecular mechanisms underlying the involvement of LHX6 in mediating the resistance to EGFR-TKIs in erlotinib-resistant NSCLC HCC827 (HCC827/ER) cells remain unknown. This study aimed to investigate the mechanisms responsible for the contribution of LHX6 to EGFR-TKIs resistance in HCC827/ER cells.

MATERIALS AND METHODS

HCC827/ER cells were generated by erlotinib treatment at a dose-escalation scheme. LHX6 knockout or overexpression was modeled in HCC827 and HCC827/ER cells, and then erlotinib IC50 values were measured. The cell migration ability was evaluated using a transwell migration assay, and the TCF/LEF luciferase activity was assessed with a TCF/LEF reporter luciferase assay. LHX6, β-catenin and Cyclin D1 expression was quantified using qPCR and Western blotting assays. In addition, the LHX6 expression was detected in lung cancer and peri-cancer specimens using immunohistochemical staining, and the associations of LHX expression with the clinicopathological characteristics of lung cancer were evaluated.

RESULTS

Lower LHX6 expression was detected in HCC827/ER cells than in HCC827 cells (P < 0.0001), while higher β-catenin expression was seen in HCC827/ER cells than in HCC827 cells (P < 0.001). LHX6 knockout increased erlotinib resistance and cell migration ability in HCC827 cells, and LHX6 overexpression inhibited erlotinib resistance and cell migration ability in HCC827/ER cells. In addition, LHX6 mediated erlotinib resistance and cell migration ability in HCC827/ER cells via the Wnt/β-catenin pathway. Immunohistochemical staining showed lower LHX6 expression in lung cancer specimens relative to peri-cancer specimens, and there were no associations of LHX6 expression with pathologic stage, gender, age or tumor size in lung cancer patients (P > 0.05).

CONCLUSION

LHX6 down-regulation may induce EGFR-TKIs resistance and increase the migration ability of HCC827/ER cells via activation of the Wnt/β-catenin pathway.

Continuation of Bevacizumab vs Cetuximab Plus Chemotherapy After First Progression in KRAS Wild-Type Metastatic Colorectal Cancer: The UNICANCER PRODIGE18 Randomized Clinical Trial

Importance

Second-line treatment with chemotherapy plus bevacizumab or cetuximab is a valid option for metastatic colorectal cancer.

Objective

To evaluate the progression-free survival (PFS) rate at 4 months with chemotherapy plus bevacizumab vs cetuximab for patients with progression of metastatic colorectal cancer after bevacizumab plus chemotherapy.

Design, Setting, and Participants

A prospective, open-label, multicenter, randomized phase 2 trial was conducted from December 14, 2010, to May 5, 2015. The main eligibility criterion was disease progression after bevacizumab plus fluorouracil with irinotecan or oxaliplatin in patients with wild-type KRAS exon 2 metastatic colorectal cancer. All analyses were performed on the modified intent-to-treat population.

Interventions

Patients were randomized to arm A (FOLFIRI [fluorouracil and folinic acid combined with irinotecan] or modified FOLFOX6 [fluorouracil and folinic acid combined with oxaliplatin] plus bevacizumab) or arm B (FOLFIRI or modified FOLFOX6 plus cetuximab); the second-line chemotherapy regimen was chosen according to first-line treatment (crossover).

Main Outcomes and Measures

The primary end point was the 4-month PFS rate. Secondary end points included safety, objective response rate, overall survival, and PFS.

Results

A total of 132 patients (47 women and 85 men; median age, 63.0 years [range, 33.0-84.0 years]; 74 patients with an Eastern Cooperative Oncology Group performance status of 0, 54 patients with a performance status of 1, and 4 patients with unknown performance status) were included at 25 sites. The 4-month PFS rate was 80.3% (95% CI, 68.0%-88.3%) in arm A and 66.7% (95% CI, 53.6%-76.8%) in arm B. The median PFS was 7.1 months (95% CI, 5.7-8.2 months) in arm A and 5.6 months (95% CI, 4.2-6.5 months) in arm B (hazard ratio, 0.71; 95% CI, 0.50-1.02; P = .06), and the median overall survival was 15.8 months (95% CI, 9.5-22.3 months) in arm A and 10.4 months (95% CI, 7.0-16.2 months) in arm B (hazard ratio, 0.69; 95% CI, 0.46-1.04; P = .08). A central analysis of KRAS (exons 2, 3, and 4), NRAS (exons 2, 3, and 4), and BRAF (V600) was performed for 95 tumor samples. Eighty-one patients had wild-type KRAS and wild-type NRAS tumors.

Conclusions and Relevance

The results of the PRODIGE18 (Partenariat de Recherche en Oncologie DIGEstive) study showed a nonsignificant difference but favored continuation of bevacizumab with chemotherapy crossover for patients with wild-type RAS metastatic colorectal cancer that progressed with first-line bevacizumab plus chemotherapy.

Trial Registration

ClinicalTrials.gov identifier: NCT01442649 and clinicaltrialsregister.eu identifier: EUDRACT 2009-012942-22.

EGFR-TKIs resistance via EGFR-independent signaling pathways

Tyrosine kinase inhibitors (TKIs)-treatments bring significant benefit for patients harboring epidermal growth factor receptor (EGFR) mutations, especially for those with lung cancer. Unfortunately, the majority of these patients ultimately develop to the acquired resistance after a period of treatment. Two central mechanisms are involved in the resistant process: EGFR secondary mutations and bypass signaling activations. In an EGFR-dependent manner, acquired mutations, such as T790 M, interferes the interaction between TKIs and the kinase domain of EGFR. While in an EGFR-independent manner, dysregulation of other receptor tyrosine kinases (RTKs) or abnormal activation of downstream compounds both have compensatory functions against the inhibition of EGFR through triggering phosphatidylinositol 3-kinase (PI3K)/Akt and mitogen-activated protein kinase (MAPK) signaling axes. Nowadays, many clinical trials aiming to overcome and prevent TKIs resistance in various cancers are ongoing or completed. EGFR-TKIs in accompany with the targeted agents for resistance-related factors afford a promising first-line strategy to further clinical application.

Intrapleural targeted therapies (anti-VEGF and anti-EGFR) in the model of malignant pleural effusion

Rationale

Malignant pleural effusion has few options of treatment and drugs administrated by different routes can lead to a less permissive microenvironment for the development of malignant pleural disease.

Objectives

To analyze therapies administered intrapleurally in malignant pleural disease and to study EGFR and KRAS mutations in adenocarcinoma.

Methods

Mice received LLC cells and were treated intrapleurally with anti-VEGF, anti-EGFR, anti-VEGF+anti-EGFR or saline. Animal survival, weight and mobility, volume, biochemistry and immunology of fluid, gene expression, KRAS and EGFR mutation were evaluated.

Results

All animals developed malignant effusion and presented progressive weight loss without difference between groups; however, groups treated with anti-EGFR were more active. No difference in mortality was observed. Temporal increase of volume and inflammatory markers was observed mainly in the untreated group. Gene expression in tumors was overexpressed in VEGF, EGFR and KRAS compared with normal tissue. Mutation in exon 2 of the KRAS gene was observed.

Conclusions

Intrapleural Anti-VEGF and/or anti-EGFR reduced volume and inflammatory mediators in pleural fluid. Anti-EGFR and anti-VEGF+anti-EGFR decreased morbidity although without impact on survival. LLC tumors presented KRAS mutation, this could have influenced the action of these therapies.

Impact of the putative cancer stem cell markers and growth factor receptor expression on the sensitivity of ovarian cancer cells to treatment with various forms of small molecule tyrosine kinase inhibitors and cytotoxic drugs

Increased expression and activation of human epidermal growth factor receptor (EGFR) and HER-2 have been reported in numerous cancers. The aim of this study was to determine the sensitivity of a large panel of human ovarian cancer cell lines (OCCLs) to treatment with various forms of small molecule tyrosine kinase inhibitors (TKIs) and cytotoxic drugs. The aim was to see if there was any association between the protein expression of various biomarkers including three putative ovarian cancer stem cell (CSC) markers (CD24, CD44, CD117/c-Kit), P-glycoprotein (P-gp), and HER family members and response to treatment with these agents. The sensitivity of 10 ovarian tumour cell lines to the treatment with various forms of HER TKIs (gefitinib, erlotinib, lapatinib, sapitinib, afatinib, canertinib, neratinib), as well as other TKIs (dasatinib, imatinib, NVP-AEW541, crizotinib) and cytotoxic agents (paclitaxel, cisplatin and doxorubicin), as single agents or in combination, was determined by SRB assay. The effect on these agents on the cell cycle distribution, and downstream signaling molecules and tumour migration were determined using flow cytometry, western blotting, and the IncuCyte Clear View cell migration assay respectively. Of the HER inhibitors, the irreversible pan-TKIs (canertinib, neratinib and afatinib) were the most effective TKIs for inhibiting the growth of all ovarian cancer cells, and for blocking the phosphorylation of EGFR, HER-2, AKT and MAPK in SKOV3 cells. Interestingly, while the majority of cancer cells were highly sensitive to treatment with dasatinib, they were relatively resistant to treatment with imatinib (i.e., IC50 >10 µM). Of the cytotoxic agents, paclitaxel was the most effective for inhibiting the growth of OCCLs, and of various combinations of these drugs, only treatment with a combination of NVP-AEW541 and paclitaxel produced a synergistic or additive anti-proliferative effect in all three cell lines examined (i.e., SKOV3, Caov3, ES2). Finally, of the TKIs, only treatment with afatinib, neratinib and dasatinib were able to reduce the migration of HER-2 overexpressing SKOV3 cells. We did not find any significant association between the expression of putative ovarian CSC marker, HER family members, c-MET, ALK, and IGF-IR and the response to the irreversible HER TKIs. Our results support the need for further investigations of the therapeutic potential of these irreversible HER family blockers in ovarian cancer, and the therapeutic potential of dasatinib when used in combination with the inhibitors of the HER family members in ovarian cancer.

Squamous carcinoma of the ovary

Squamous ovarian cancer (SOC) represents a (very) rare subtype of ovarian cancer. The lack of evidence on which to base management presents significant challenges. The small number of patients prohibits randomised studies to establish level 1 evidence, and no non-randomised studies or prospective series have been reported. Here, we present a review of the available literature on squamous ovarian cancer and explore some lessons learnt from squamous cancers originating from other primary sites to see if these can be applied to SOC.

Erlotinib Pretreatment Improves Photodynamic Therapy of Non-Small Cell Lung Carcinoma Xenografts via Multiple Mechanisms

Aberrant expression of the epidermal growth factor receptor (EGFR) is a common characteristic of many cancers, including non-small cell lung carcinoma (NSCLC), head and neck squamous cell carcinoma, and ovarian cancer. Although EGFR is currently a favorite molecular target for the treatment of these cancers, inhibition of the receptor with small-molecule inhibitors (i.e., erlotinib) or monoclonal antibodies (i.e., cetuximab) does not provide long-term therapeutic benefit as standalone treatment. Interestingly, we have found that addition of erlotinib to photodynamic therapy (PDT) can improve treatment response in typically erlotinib-resistant NSCLC tumor xenografts. Ninety-day complete response rates of 63% are achieved when erlotinib is administered in three doses before PDT of H460 human tumor xenografts, compared with 16% after PDT-alone. Similar benefit is found when erlotinib is added to PDT of A549 NCSLC xenografts. Improved response is accompanied by increased vascular shutdown, and erlotinib increases the in vitro cytotoxicity of PDT to endothelial cells. Tumor uptake of the photosensitizer (benzoporphyrin derivative monoacid ring A; BPD) is increased by the in vivo administration of erlotinib; nevertheless, this elevation of BPD levels only partially accounts for the benefit of erlotinib to PDT. Thus, pretreatment with erlotinib augments multiple mechanisms of PDT effect that collectively lead to large improvements in therapeutic efficacy. These data demonstrate that short-duration administration of erlotinib before PDT can greatly improve the responsiveness of even erlotinib-resistant tumors to treatment. Results will inform clinical investigation of EGFR-targeting therapeutics in conjunction with PDT.

Chemotherapy for oral and maxillofacial tumors: an update

Surgery is the primary intervention in oral and maxillofacial tumors and under ideal circumstances is curative. There is no evidence to support the use of induction or adjuvant chemotherapy in initial therapy of early stage tumors. Locally advanced tumors, non-resectable tumors as well as recurrence in early stage disease, need a multi-modality therapeutic approach involving chemotherapy. Palliative chemotherapy plays an important role in the treatment patients with metastatic oral and maxillofacial tumors. Chemotherapy and targeted agents plays an important role in the treatment of patients with rare oral and maxillofacial tumors such as sarcomas, lymphomas, and giant cell tumors.

Nuclear localization of epidermal growth factor receptor (EGFR) in ameloblastomas

BACKGROUND

Ameloblastoma is a locally invasive neoplasm often associated with morbidity and facial deformities, showing increased Epidermal Growth Factor Receptor (EGFR) expression. Inhibition of EGFR was suggested as a treatment option for a subset of ameloblastomas. However, there are resistance mechanisms that impair anti-EGFR therapies. One important resistance mechanism for EGFR-inhibition is the EGFR nuclear localization, which activates genes responsible for its mitogenic effects, such as Cyclin D1.

METHODS

We assessed EGFR nuclear localization in encapsulated (unicystic, n = 3) and infiltrative (multicystic, n = 11) ameloblastomas and its colocalization with Cyclin D1 by using anti-EGFR and anti-lamin B1 double labeling immunofluorescence analyzed by confocal microscopy. Oral inflammatory fibrous hyperplasia and oral squamous cell carcinoma samples were used for comparison.

RESULTS

Twelve cases of ameloblastoma exhibited nuclear EGFR colocalization with lamin B1. This positive staining was mainly observed in the ameloblast-like cells. The EGFR nuclear localization was also observed in control samples. In addition, nuclear EGFR colocalized with Cyclin D1 in ameloblastomas.

CONCLUSIONS

Nuclear EGFR occurs in ameloblastomas in association with Cyclin D1 expression, which is important in terms of tumor biology clarification and raises a concern about anti-EGFR treatment resistance in ameloblastomas.

Addition of bevacizumab enhances antitumor activity of erlotinib against non-small cell lung cancer xenografts depending on VEGF expression

PURPOSE

Erlotinib, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), and bevacizumab, an anti-vascular endothelial growth factor (VEGF) agent, are promising therapies for advanced non-small cell lung cancer (NSCLC). Our study was aimed to determine whether there were conditions under which the addition of bevacizumab would enhance the antitumor activity of erlotinib against NSCLC tumors in vitro and in vivo.

METHODS

MTS was for NSCLC cell (PC9, 11-18, H1975, H157, H460 and A549) growth assay in vitro. ELISA was for VEGF protein assay in cells and tumor tissues. Mouse xenograft models were established with H157, H460 and A549 with primary resistance to erlotinib and treated with erlotinib plus bevacizumab or each agent alone. Erlotinib concentrations in tumors were determined by high-performance liquid chromatography.

RESULTS

Bevacizumab alone did not inhibit NSCLC cell growth in vitro. In primarily erlotinib-resistant NSCLC cells, the levels of VEGF protein were highest in H157 cell followed in order by H460 and A549 cells. In vivo, bevacizumab alone significantly inhibited tumor growth only in xenograft models with high (H157) and/or moderate (H460) levels of VEGF protein. A combination of erlotinib and bevacizumab partially reversed resistance to erlotinib in H157 xenografts (high VEGF level) with increasing intratumoral erlotinib concentrations, but not in H460 (moderate) or A549 (low) xenografts.

CONCLUSIONS

These results support that combined with anti-VEGF therapy could enhance antitumor activity of anti-EGFR therapy and/or partially reverse resistance to EGFR TKI, by increasing EGFR TKI concentration in specific tumors that express high levels of VEGF protein.

Drug resistance to molecular targeted therapy and its consequences for treatment decisions in non-small-cell lung cancer

Our ability to detect and directly target the oncogenic alterations responsible for tumor proliferation has contributed significantly to the management of lung cancer in the last decade. The therapeutic efficacy of molecularly targeted therapy is, however, mainly limited to patients harboring certain genetic mutations and is generally short-lived. Herein, we review primary and secondary drug resistance using the most well-studied of the molecularly targeted agents, the tyrosine kinase inhibitors targeting the epidermal growth factor (EGF) receptor, and the anaplastic lymphoma kinase (ALK) rearrangement, the current limitations of targeted therapies and their consequences on the management of patients with lung cancer.

Predicting response to epidermal growth factor receptor-targeted therapy in colorectal cancer

The discovery over 20 years ago by the Nobel Laureate Stanley Cohen of epidermal growth factor and its receptor, followed by the recognition that this receptor is overexpressed in multiple cancer types, has been of phenomenal significance. From these events the 'Holy Grail' of targeted therapy has looked increasingly realistic. Over the last 5 years this work has come of age with the licensing of multiple agents targeting this important mitogenic pathway in multiple tumor types. However, these agents and the technology behind them, while impressive, have resulted in lower clinical response rates than anticipated. In this review we will focus on the epidermal growth factor receptor-targeted therapies in colorectal cancer, why our expectations from these therapies have not yet been fulfilled and how we may predict those cancers that are likely to respond or be resistant to these therapies through a greater appreciation of the intricacy, diversity and dynamism of cellular signaling mechanisms.

Cetuximab and bevacizumab: preclinical data and phase II trial in recurrent or metastatic squamous cell carcinoma of the head and neck

BACKGROUND

We evaluated combined targeting with cetuximab, an anti-epidermal growth factor receptor (EGFR) monoclonal antibody, and bevacizumab, an anti-vascular endothelial growth factor (VEGF) monoclonal antibody, in squamous cell carcinoma of the head and neck (SCCHN).

PATIENTS AND METHODS

The combination was studied in human endothelial cells and head and neck and lung cancer xenograft model systems. Patients with recurrent or metastatic SCCHN were treated with weekly cetuximab and bevacizumab, 15 mg/kg on day 1 given intravenously every 21 days, until disease progression. Analysis of tumor biomarkers and related serum cytokines was performed.

RESULTS

Cetuximab plus bevacizumab enhanced growth inhibition both in vitro and in vivo, and resulted in potent reduction in tumor vascularization. In the clinical trial, 46 eligible patients were enrolled. The objective response rate was 16% and the disease control rate 73%. The median progression-free survival and overall survival were 2.8 and 7.5 months, respectively. Grade 3-4 adverse events were expected and occurred in less than 10% of patients. transforming growth factor alpha, placenta-derived growth factor, EGFR, VEGFR2 increased and VEGF decreased after treatment but did not correlate with treatment efficacy.

CONCLUSIONS

Cetuximab and bevacizumab are supported by preclinical observations and are well tolerated and active in previously treated patients with SCCHN.

Anti-angiogenic therapy renders large tumors vulnerable to immunotherapy via reducing immunosuppression in the tumor microenvironment

We have recently demonstrated that a 4-in-1 gene therapy strategy that contains two anti-angiogenic genes [endostatin and pigment epithelium-derived factor] and two cytokine genes [granulocyte macrophage colony-stimulating factor and interleukin 12] has a considerable antitumor effect on large tumors in a woodchuck hepatoma model. The current study further investigates the underlying mechanisms for the antitumor effect observed by using small rodent models. We found that immunotherapy alone increased immunosuppressive cells in large tumors over time, whereas the anti-angiogenic therapy contained in the 4-in-1 strategy alleviated immunosuppression and made tumors vulnerable to immunotherapy, thus resulting in a synergistic antitumor effect.

Androgen-independent prostate cancer cells circumvent EGFR inhibition by overexpression of alternative HER receptors and ligands

The deregulation of the epidermal growth factor receptor (EGFR) pathway plays a major role in the pathogenesis of prostate cancer (PCa). However, therapies targeting EGFR have demonstrated limited effectiveness in PCa. A potential mechanism to overcome EGFR blockade in cancer cells is the autocrine activation of alternative receptors of the human EGFR (HER) family through the overexpression of the HER receptors and ligands. In the present study, we were interested in analyzing if this intrinsic resistance mechanism might contribute to the inefficacy of EGFR inhibitors in PCa. To this end, we selected two androgen-independent human prostate carcinoma cell lines (DU145 and PC3) and established DU145 erlotinib-resistant cells (DUErR). Cells were treated with three EGFR inhibitors (cetuximab, gefinitib and erlotinib) and the sensitivity to each treatment was assessed. The gene expression of the four EGFR/HER receptors and seven ligands of the HER family was analyzed by real-time PCR prior to and after each treatment. The receptors expression and activation were further characterized by flow cytometry and western blot analysis. EGFR inhibition rapidly induced enhanced gene expression of the EGF, betacellulin and neuregulin-1 ligands along with HER2, HER3 and HER4 receptors in the DU145 cells. In contrast, slight changes were observed in the PC3 cells, which are defective in the phosphatase and tensin homolog (PTEN) tumor suppressor gene. In the erlotinib-resistant DUErR cells, the expression of HER2 and HER3 was increased at mRNA and protein levels together with neuregulin-1, leading to enhanced HER3 phosphorylation and the activation of the downstream PI3K/Akt survival pathway. HER3 blockage by a monoclonal antibody restored the cytostatic activity of erlotinib in DUErR cells. Our results confirm that the overexpression and autocrine activation of HER3 play a key role in mediating the resistance to EGFR inhibitors in androgen-independent PCa cells.

Targeted therapies for advanced non-small-cell lung cancer: current status and future implications

Lung cancer remains the leading cause of malignancy-related mortality worldwide, with over one million cases diagnosed yearly. Non-small-cell lung cancer (NSCLC) accounts for >80% of all lung cancers. Because lung cancer is typically diagnosed at an advanced stage, chemotherapy (CT) is the mainstay of management. Conventional treatment of NSCLC has apparently reached a plateau of effectiveness in improving survival of patients, and treatment outcomes must still be considered disappointing. Hence, considerable efforts have been made in order to identify novel targeted agents that interfere with other dysregulated pathways in advanced NSCLC patients. In order to further improve the results of targeted therapy, we should not forget that lung cancer is a heterogeneous disease with multiple mutations, and it is unlikely that any single signaling pathway drives the oncogenic behaviour of all tumours. The relative failure of some targeted therapies may be a result of multilevel cross-stimulation among the targets of the new biological agents along several pathways of signal transduction that lead to neoplastic events. Thus, blocking only one of these pathways allows others to act as salvage or escape mechanisms for cancer cells. We summarize the most promising research approaches to the treatment of NSCLC, with particular attention to drugs with multiple targets or combining targeted therapies.

RETRACTED: Antitumor activity of bortezomib in human cancer cells with acquired resistance to anti-epidermal growth factor receptor tyrosine kinase inhibitors

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief Concern has been raised about the duplication of the β-Actin protein blot in the western blots that are in Figure 3A and Figure 4C. The authors have been asked to provide an acceptable explanation for this and – after initial denial and being presented with an independent evaluation noted that the western blot for β-Actin in Figure 3A was erroneously uploaded as a partial duplication of the β-Actin western blot in Figure 4C. According to the authors, this mistake was due to the fact that both Figure 3A and Figure 4C are representing the same experiment with only different protein species presented in the two Figures and with the loading control β-Actin that is presented in both Figures. The Editor-in-Chief of the journal therefore feels that the findings of the manuscript cannot be relied upon and that the article needs to be retracted. All authors agree with this retraction and deeply regret these errors and apologize to the editorial board and readers for any inconvenience caused.

Current status of vandetanib (ZD6474) in the treatment of non-small cell lung cancer

Vandetanib (ZD6474) is an oral small molecule inhibitor of multiple intracellular receptor kinases, including the vascular endothelial growth factor receptor (VEGFR) -2 and epidermal growth factor receptor (EGFR). Both VEGFR and EGFR pathways have emerged as instrumental in the growth and metastasis of multiple malignancies, including non-small cell lung cancer (NSCLC). Indeed, inhibitors of each pathway have been approved by the US Food and Drug Administration for use in advanced NSCLC. As there is considerable cross talk between these pathways, dual inhibition with such agents has become an attractive strategy, with encouraging Phase II clinical trial data to date. The convenience of one oral agent targeting both pathways is clear, and clinical trials have established the maximum tolerated daily dose of vandetanib, with data from randomized Phase III trials emerging. This report will review completed and ongoing NSCLC clinical trials evaluating vandetanib, and speculate on the future of this agent in NSCLC.

Cetuximab may inhibit tumor growth and angiogenesis induced by ionizing radiation: a preclinical rationale for maintenance treatment after radiotherapy

BACKGROUND

The benefits of radiotherapy and cetuximab have encouraged evaluation of cetuximab after radiotherapy. The aims of this study were to preclinically evaluate the efficacy of cetuximab maintenance after radiotherapy and eventually determine its mechanisms of action.

METHODS

The A431 human carcinoma cell line was treated in culture with fractionated radiotherapy and cetuximab. The surviving cells were injected s.c. into nude mice to mimic microscopic residual disease. The animals were randomized to receive either cetuximab or saline solution. Tumor growth, cell proliferation (Ki-67), microvessel density (MVD), epidermal growth factor receptor (EGFR) and transforming growth factor (TGF-α) mRNA transcription, and vascular endothelial growth factor (VEGF) secretion were measured.

RESULTS

Tumors from irradiated cells had a faster growth rate, higher Ki-67 index, and greater angiogenesis than tumors from untreated cells. This aggressive phenotype was associated with in vitro radiation-induced extracellular signal-related kinase (ERK)-1/2 and Akt activation, greater EGFR and TGF-α transcription, and augmented VEGF secretion, all of which were inhibited by cetuximab. In cetuximab-treated mice with tumors arising from irradiated cells, time to volume was longer by a factor of 3.52, whereas the Ki-67 index and MVD were 1.57 and 1.49 times lower, respectively, a larger enhancement than seen in tumors from untreated cells. These findings suggest that cells surviving radiation may express factors that promote cell survival and induce an aggressive phenotype that may potentially be blocked by cetuximab maintenance therapy.

CONCLUSIONS

These results support the clinical evaluation of adjuvant therapy with cetuximab after radiotherapy in EGFR-dependent carcinomas.

Combining antiangiogenic therapy with immunotherapy exerts better therapeutical effects on large tumors in a woodchuck hepatoma model

Cytokine and antiangiogenic gene therapies have proved effective in implanted hepatocellular carcinoma (HCC) models in which small tumor burdens were established in small rodents. These models, however, may not reflect human HCCs, which are frequently detected at a stage when tumors are large and multifocal. In addition, HCC in patients is often associated with viral hepatitis. To investigate the effectiveness of a mixture type of gene therapy strategy on large tumor burdens, we used the woodchuck model in which woodchuck hepatitis virus-induced HCCs are large and multifocal, simulating the conditions in humans. Adenoviruses encoding antiangiogenic factors (pigment epithelium-derived factor and endostatin) or cytokines (GM-CSF and IL-12) were delivered via the hepatic artery separately or in combination into woodchuck livers bearing HCCs. Our results showed that the mixture type of strategy, which contained two cytokines and two antiangiogenic factors, had better antitumor effects on large tumors as compared with monotherapy either with antiangiogenic or cytokine genes. The immunotherapy recruited significant levels of CD3(+) T cells that infiltrated the tumors, whereas the antiangiogenesis-based therapy significantly reduced tumor vasculature. The mixture type of gene therapy achieved both effects. In addition, it induced high levels of natural killer cells and apoptotic cells and reduced the levels of immunosuppressive effectors in the tumor regions. Hence, antiangiogenic therapy may provide the advantage of reducing immune tolerance in large tumors, making them more vulnerable to the immune reactions. Our study implies that in the future, the combination therapy may prove effective for the treatment of patients with advanced HCC.

Monoclonal antibodies in the treatment of metastatic colorectal cancer: a review

BACKGROUND

Two groups of agents targeting either the vascular endothelial growth factor (VEGF) receptor or the epidermal growth factor receptor (EGFR) have been added to the therapeutic arsenal against metastatic colorectal cancer (mCRC). Currently available agents in these groups are the anti-VEGF antibody bevacizumab and the anti-EGFR antibodies cetuximab and panitumumab.

OBJECTIVES

This article reviews the results of prospective randomized clinical trials of anti-VEGF and anti-EGFR antibodies in mCRC, either as monotherapy, combined with chemotherapy, or combined with each other. Also reviewed are retrospective subset analyses of the effect of a KRAS mutation on the response to anti-EGFR antibodies.

METHODS

MEDLINE (2004-2009) was searched for randomized Phase II-III clinical trials of monoclonal antibodies in mCRC published in English. The search terms were colorectal neoplasms, bevacizumab, cetuximab, panitumumab, and KRAS mutation, alone or in combination. Information on the effect of KRAS mutation status on the response to anti-EGFR antibodies was drawn from retrospective subset analyses within the selected trials.

RESULTS

The literature search identified 5 trials of bevacizumab in mCRC. Of these trials, 3 found a significant benefit on the primary end point (progression-free survival [PFS] or overall survival [OS]) when bevacizumab was added to chemotherapy, either as first-line (2 trials) or second-line (1 trial) treatment. The literature search identified 5 trials of cetuximab and 1 trial of panitumumab in mCRC. Of these trials, 4 found a significant benefit on the primary end point (response rate, PFS, or OS) with cetuximab or panitumumab as monotherapy or added to chemotherapy, either as first-line (1 trial) or later-line (3 trials) treatment. In all trials, the benefit of anti-EGFR therapy was limited to patients who had KRAS wild-type tumors. Of 3 identified trials of combined anti-EGFR and anti-VEGF therapy, 2 found that the combination of an anti-EGFR antibody and the anti-VEGF antibody bevacizumab had a significant negative effect on the primary end point (PFS) compared with no added anti-EGFR antibody.

CONCLUSIONS

In the studies reviewed, the anti-VEGF antibody bevacizumab added to chemotherapy and the anti-EGFR antibodies cetuximab and panitumumab as monotherapy or added to chemotherapy were associated with consistent efficacy in the treatment of mCRC, although the absolute benefit differed among trials. The efficacy of anti-EGFR antibodies was limited to patients with KRAS wild-type tumors. Given the lack of benefit when anti-VEGF and anti-EGFR antibodies were combined, such regimens should not be used in clinical practice.

Nuclear EGFR contributes to acquired resistance to cetuximab

Epidermal growth factor receptor (EGFR) is a ubiquitously expressed receptor tyrosine kinase involved in the etiology of several human cancers. Cetuximab is an EGFR-blocking antibody that has been approved for the treatment of patients with head and neck squamous cell carcinoma and metastatic colorectal cancer. Previous reports have shown that EGFR translocation to the nucleus is associated with cell proliferation. Here we investigated mechanisms of acquired resistance to cetuximab using a model derived from the non-small cell lung cancer line H226. We demonstrated that cetuximab-resistant cells overexpress HER family ligands including epidermal growth factor (EGF), amphiregulin, heparin-binding EGF and beta-cellulin. Overexpression of these ligands is associated with the nuclear translocation of the EGFR and this process was mediated by the Src family kinases (SFK). Treatment of cetuximab-resistant cells with the SFK inhibitor, dasatinib, resulted in loss of nuclear EGFR, increased membrane expression of the EGFR and resensitization to cetuximab. In addition, expression of a nuclear localization sequence-tagged EGFR in cetuximab-sensitive cells increased resistance to cetuximab both in vitro and in mouse xenografts. Collectively, these data suggest that nuclear expression of EGFR may be an important molecular determinant of resistance to cetuximab therapy and provides a rationale for investigating nuclear EGFR as a biomarker for cetuximab response. Further, these data suggest a rationale for the design of clinical trials that examine the value of treating patients with cetuximab-resistant tumors with inhibitors of SFKs in combination with cetuximab.

Complex prolactin crosstalk in breast cancer: new therapeutic implications

The contributions of prolactin (PRL) to breast cancer are becoming increasingly recognized. To better understand the role for PRL in this disease, its interactions with other oncogenic growth factors and hormones must be characterized. Here, we review our current understanding of PRL crosstalk with other mammary oncogenic factors, including estrogen, epidermal growth factor (EGF) family members, and insulin-like growth factor-I (IGF-I). The ability of PRL to potentiate the actions of these targets of highly successful endocrine and molecular therapies suggests that PRL and/or its receptor (PRLR) may be an attractive therapeutic target(s). We discuss the potential benefit of PRL/PRLR-targeted therapy in combination with established therapies and implications for de novo and acquired resistance to treatment.

Combined inhibition of the VEGFR and EGFR signaling pathways in the treatment of NSCLC

Multitargeted agents represent the next generation of targeted therapies in solid tumors. The benefits of individually targeting the vascular endothelial growth factor receptor (VEGFR) and epidermal growth factor receptor (EGFR) signaling pathways have been clinically validated in recent years in a number of solid tumor types including non-small cell lung cancer (NSCLC). Given the heterogeneity of this tumor type and potential crosstalk between these key signaling pathways (which are known to play a critical role in tumor growth, metastasis, and angiogenesis), dual inhibition of the VEGFR and EGFR signaling pathways has the potential to offer additional clinical benefits in NSCLC. A number of approaches to inhibiting both VEGFR and EGFR signaling are currently under investigation, including monotherapy with a multitargeted tyrosine kinase inhibitor (e.g., vandetanib, AEE788, XL647, BMS-690514) or a combination of single-targeted therapies (e.g., bevacizumab, cetuximab, erlotinib, gefitinib). Preclinical and early clinical data (phase I and II trials) support combined inhibition of the VEGFR and EGFR pathways in NSCLC. Overall, combined inhibition strategies are well tolerated and have shown promise in early clinical studies. Ongoing phase II and phase III trials will determine the clinical potential of a number of dual inhibition strategies in the treatment of advanced NSCLC.

Establishment and characterization of a model of acquired resistance to epidermal growth factor receptor targeting agents in human cancer cells

PURPOSE

The epidermal growth factor receptor (EGFR) is recognized as a key mediator of proliferation and progression in many human tumors. A series of EGFR-specific inhibitors have recently gained Food and Drug Administration approval in oncology. These strategies of EGFR inhibition have shown major tumor regressions in approximately 10% to 20% of advanced cancer patients. Many tumors, however, eventually manifest resistance to treatment. Efforts to better understand the underlying mechanisms of acquired resistance to EGFR inhibitors, and potential strategies to overcome resistance, are greatly needed.

EXPERIMENTAL DESIGN

To develop cell lines with acquired resistance to EGFR inhibitors we utilized the human head and neck squamous cell carcinoma tumor cell line SCC-1. Cells were treated with increasing concentrations of cetuximab, gefitinib, or erlotinib, and characterized for the molecular changes in the EGFR inhibitor-resistant lines relative to the EGFR inhibitor-sensitive lines.

RESULTS

EGFR inhibitor-resistant lines were able to maintain their resistant phenotype in both drug-free medium and in athymic nude mouse xenografts. In addition, EGFR inhibitor-resistant lines showed a markedly increased proliferation rate. EGFR inhibitor-resistant lines had elevated levels of phosphorylated EGFR, mitogen-activated protein kinase, AKT, and signal transducer and activator of transcription 3, which were associated with reduced apoptotic capacity. Subsequent in vivo experiments indicated enhanced angiogenic potential in EGFR inhibitor-resistant lines. Finally, EGFR inhibitor-resistant lines showed cross-resistance to ionizing radiation.

CONCLUSIONS

We have developed EGFR inhibitor-resistant human head and neck squamous cell carcinoma cell lines. This model provides a valuable preclinical tool to investigate molecular mechanisms of acquired resistance to EGFR blockade.

Integrating biologically targeted therapy in head and neck squamous cell carcinomas

The integration of targeted therapies such as cetuximab to radiation therapy has revolutionized the management of head and neck cancers in the last decade. However, the use of targeted therapies raised several clinically relevant questions that have yet to be answered. These questions include the optimal patient and tumor profile for biologically targeted therapy, the optimal radiation fractionation to use with targeted therapies, how to integrate them into standard or new chemoradiation regimens, their schedule and duration of administration, their toxicity, and which direction to consider for novel targeted treatment. In this review, we highlight several of these important issues, discuss the clinical trials that are designed to address these issues, and introduce some novel targeted therapies that may contribute to the improvement of the therapeutic ratio for head and neck cancer therapy.

Improved therapeutic effectiveness by combining liposomal honokiol with cisplatin in lung cancer model

Background

Honokiol is a major bioactive compound extracted from Magnolia. The present study was designed to determine whether liposomal honokiol has the antitumor activity against human lung cancer as well as potentiates the antitumor activity of cisplatin in A549 lung cancer xenograft model, if so, to examine the possible mechanism in the phenomenon.

Methods

human A549 lung cancer-bearing nude mice were treated with liposomal honokiol, liposomal honokiol plus DDP or with control groups. Apoptotic cells and vessels were evaluated by fluorescent in situ TUNEL assay and by immunohistochemistry with an antibody reactive to CD31 respectively.

Results

The present study showed that liposomal honokiol alone resulted in effective suppression of the tumor growth, and that the combined treatment with honokiol plus DDP had the enhanced inhibition of the tumor growth and resulted in a significant increase in life span. The more apparent apoptotic cells in the tumors treated with honokiol plus DDP was found in fluorescent in situ TUNEL assay, compared with the treatment with control groups. In addition, the combination of honokiol and DDP apparently reduced the number of vessels by immunolabeling of CD31 in the tissue sections, compared with control groups.

Conclusion

In summary, our data suggest that honokiol alone had the antitumor activity against human lung cancer in A549 lung cancer xenograft model, and that the combination of honokiol with DDP can enhance the antitumor activity, and that the enhanced antitumor efficacy in vivo may in part result from the increased induction of the apoptosis and the enhanced inhibition of angiogenesis in the combined treatment. The present findings may be of importance to the further exploration of the potential application of the honokiol alone or the combined approach in the treatment of lung carcinoma.

Antiangiogenic therapy in nonsmall cell lung cancer

PURPOSE OF REVIEW

The use of targeted therapies, particularly those against the key mediator of angiogenesis, vascular endothelial growth factor, has the potential to improve outcomes for nonsmall cell lung cancer (NSCLC) patients. This review summarizes recent findings on targeting mediators of angiogenesis, treatment options and molecular targets in development.

RECENT FINDINGS

Bevacizumab, a recombinant humanized monoclonal antivascular endothelial growth factor antibody, in a phase III study, showed significantly improved overall and progression-free survival when used in combination with standard first-line chemotherapy in patients with advanced NSCLC and was generally well tolerated. Adverse events, including tumor-related bleeding, have been noted in some patients, predominantly those with squamous cell histology or centrally located tumors.

SUMMARY

Several small-molecule vascular endothelial growth factor receptor tyrosine kinase inhibitors have also shown promise in phase I and II trials in NSCLC. This review summarizes the most important findings on angiogenesis inhibitors in NSCLC and discusses the potential for the use of these novel agents in different settings.

Drug resistance in cancer - searching for mechanisms, markers and therapeutic agents

Treatment resistance, whether inherent or acquired, is a major problem reducing the activity of conventional and newer, molecularly targeted, cancer drugs. A more complex picture of the causes and contributions of specific forms of resistance is now emerging through application of pharmacological, proteomic and gene expression technologies and we have entered an exciting time where new molecular research tools are being applied not only to characterise the causes of such resistance, but to identify rational new treatments and treatment combinations that are being rapidly translated to clinical evaluations with increasing success. This review outlines many of the contributing causes of resistance to established cytotoxics and to the new breed of molecularly targeted agents, both monoclonal antibodies and small molecules, and the research methods being used to wage war on resistant cancer.

EGF-receptor targeting with monoclonal antibodies in colorectal carcinomas: rationale for a pharmacogenomic approach

Monoclonal antibodies directed against the EGF-receptor (EGFR) have recently been approved for the treatment of metastatic colorectal cancer (CRC) patients with EGFR-positive tumors at immunohistochemistry (IHC). Surprisingly, data demonstrate a lack of correlation between the tumor’s EGFR expression at IHC and outcome. Indeed, as pointed out from small experiences, patients with EGFR-IHC-negative metastatic CRC have the same chance as EGFR-IHC-positive patients to benefit from an anti-EGFR monoclonal antibody, underlying the importance of different, more reliable, selection criteria. In particular, the identification of such predictive factors is important as these agents are expensive, have side effects and are really only effective in a minority of patients. Several potential clinical and biological predictive markers of activity and/or efficacy for such agents have been evaluated in retrospective series with promising results. Moving from clinical data suggesting that there could be a subpopulation of CRC patients that are more liable to benefit from anti-EGFR monoclonal antibodies, here we review major studies on determinants of outcome in this field.

Blockade of an angiotensin type I receptor enhances effects of radiation on tumor growth and tumor-associated angiogenesis by reducing vascular endothelial growth factor expression

OBJECTIVE

Angiogenesis, the formation of new capillary blood vessels, is essential for tumor progression. We had reported that Type 1 angiotensin receptor (AT1-R) antagonist reduced tumor-associated angiogenesis. Since antiangiogenic agents were reported to enhance efficacy of radiation therapy, we tested here whether or not AT1-R blockade facilitates the effects of radiation.

METHODS

1 x 10(6) LLC cells were injected into the subcutaneous tissue of male C57BL/6 mice, and when the average tumor volume reached around 0.1 cm(3), radiation doses (3, 5, 10, and 15 Gy) were given on day 1.

RESULTS

The mean tumor volumes at day 22 were 6.39 (3 Gy), 6.15 (5 Gy), 5.15 (10 Gy), and 3.07 (15 Gy) cm(3), respectively. Combination of 10 Gy radiation with AT1R antagonist TCV-116 (30 mg/kg) significantly inhibited tumor growth by 83% (1.47 +/- 0.11 cm(3), P < 0.01) in comparison with its inhibition of control tumors (8.81 +/- 0.45 cm(3)). The same was true for mean vessel density, and the combination therapy markedly reduced tumor-associated angiogenesis. This was confirmed by the reduced expression of CD31. LLC tumor growth was blocked by neutralizing antibody against vascular endothelial growth factor (VEGF). Real-time PCR analysis of VEGF disclosed a marked reduction in the mice under combination therapy, compared with control mice.

CONCLUSIONS

These results suggest that combination of radiation with AT1-R blockade markedly reduced the LLC growth rate, and that this was due to reduction of neovascularization by reducing VEGF levels. Combination therapy consisting of radiation and AT1R blockade may become an effective novel strategy for cancer treatment.