Synergistic interaction between the EGFR tyrosine kinase inhibitor gefitinib ("Iressa") and the DNA topoisomerase I inhibitor CPT-11 (irinotecan) in human colorectal cancer cells

Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors in Cancer: Current Use and Future Prospects

Tyrosine kinase inhibitors (TKIs) have emerged as a leading targeted cancer therapy, reducing the side effects often seen with non-targeted treatments, especially the damage to healthy cells. To tackle resistance, typically caused by epidermal growth factor receptor (EGFR) mutations, four generations of TKIs have been developed. Each generation has shown improved effectiveness and fewer side effects, resulting in better patient outcomes. For example, patients on gefitinib, a first-generation TKI, experienced a progression-free survival (PFS) of 10 months compared to 5 months with conventional chemotherapy. Second-generation TKI afatinib outperformed erlotinib and extended PFS to 11.1 months compared to 6.9 months with cisplatin. Third-generation TKIs further increased survival to 38.6 months, compared to 31.8 months with first-generation TKIs. This progress demonstrates the ability of newer TKIs to overcome resistance, particularly the T790M mutation, while reducing adverse effects. Ongoing research focuses on overcoming resistance from newer mutations like C797S to further improve patient survival. These developments highlight the significant progress in TKI therapy and the continued effort to refine cancer treatment. Recent research in South Korea shows that third-generation TKIs are ineffective against non-small cell lung cancer (NSCLC) with the C797S mutation. Several trials have started showing promising in vitro and in vivo results, but more trials are needed before clinical approval. This review underscores notable advancements in the field of EGFR TKIs, offering a comprehensive analysis of their mechanisms of action and the progression of various TKI generations in response to resistance.

Functional genomics reveals an off-target dependency of drug synergy in gastric cancer therapy

BACKGROUND

Integrating molecular-targeted agents into combination chemotherapy is transformative for enhancing treatment outcomes in cancer. However, realizing the full potential of this approach requires a clear comprehension of the genetic dependencies underlying drug synergy. While the interactions between conventional chemotherapeutics are well-explored, the interplay of molecular-targeted agents with conventional chemotherapeutics remains a frontier in cancer treatment. Hence, we leveraged a powerful functional genomics approach to decode genomic dependencies that drive synergy in molecular-targeted agent/chemotherapeutic combinations in gastric adenocarcinoma, addressing a critical need in gastric cancer therapy.

METHODS

We screened pharmacological interactions between fifteen molecular-targeted agent/conventional chemotherapeutic pairs in gastric adenocarcinoma cells, and examined the genome-scale genetic dependencies of synergy integrating genome-wide CRISPR screening with the shRNA-based signature assay. We validated the synergy in cell death using fluorescence-based and lysis-dependent inference of cell death kinetics assay, and validated the genetic dependencies by single-gene knockout experiments.

RESULTS

Our combination screen identified SN-38/erlotinib as the drug pair with the strongest synergism. Functional genomics assays unveiled a genetic dependency signature of SN-38/erlotinib identical to SN-38. Remarkably, the enhanced cell death with improved kinetics induced by SN-38/erlotinib was attributed to erlotinib's off-target effect, inhibiting ABCG2, rather than its on-target effect on EGFR.

CONCLUSION

In the era of precision medicine, where emphasis on primary drug targets prevails, our research challenges this paradigm by showcasing a robust synergy underpinned by an off-target dependency. Further dissection of the intricate genetic dependencies that underlie synergy can pave the way to developing more effective combination strategies in gastric cancer therapy.

Update on Emerging Therapies for Advanced Colorectal Cancer

Colorectal cancer (CRC) is the third most common malignancy worldwide. It is projected to increase by 3.2 million new cases and account for 1.6 million deaths by 2040. Mortality is largely due to limited treatment options for patients who present with advanced disease. Thus, the development of effective and tolerable therapies is crucial. Chemotherapy has been the backbone of systemic treatment of advanced CRC, but utility has been limited because of invariable resistance to therapy, narrow mechanisms of action, and unfavorable toxicity profile. Tumors that are mismatch repair-deficient have demonstrated remarkable response to immune checkpoint inhibitor therapy. However, most CRC tumors are mismatch repair-proficient and represent an unmet medical need. Although ERBB2 amplification occurs only in a few cases, it is associated with left-sided tumors and a higher incidence of brain metastasis. Numerous combinations of HER2 inhibitors have demonstrated efficacy, and antibody-drug conjugates against HER2 represent innovative strategies in this area. The KRAS protein has been classically considered undruggable. Fortunately, new agents targeting KRAS G12C mutation represent a paradigm shift in the management of affected patients and could lead the advancement in drug development for the more common KRAS mutations. Furthermore, aberrant DNA damage response is present in 15%-20% of CRCs, and emerging innovative combinations with poly (ADP-ribose) polymerase (PARP) inhibitors could improve the current therapeutic landscape. Multiple novel biomarker-driven approaches in the management of patients with advanced CRC tumors are reviewed in this article.

An empirical review on the resistance mechanisms of epidermal growth factor receptor inhibitors and predictive molecular biomarkers in colorectal cancer

Despite advances in cytotoxic treatments, colorectal cancer remains a leading cause of death. Metastatic colorectal cancer (mCRC) patients have a poor prognosis despite improved treatments and more prolonged median survival. Monoclonal antibodies like cetuximab and panitumumab target the epidermal growth factor receptor (EGFR). They play an essential role in the treatment of metastatic colorectal cancer (mCRC) due to their efficacy in multiple phase III clinical trials across multiple treatment lines. It was discovered that anti-EGFR moAbs were only effective for a small number of patients. Mutations in KRAS and NRAS have been identified as biomarkers of drug resistance. New molecular predictors and prognostic markers are used clinically. The K-Ras mutation is the first molecular marker of a lack of response to EGFR-targeted therapy in K-Ras-mutant patients. Validating predictive and prognostic markers will improve cancer treatments. This article examines molecular markers that can predict colorectal cancer prognosis.

6-Shogaol Overcomes Gefitinib Resistance via ER Stress in Ovarian Cancer Cells

In women, ovary cancer is already the fifth leading cause of mortality worldwide. The use of cancer therapies, such as surgery, radiotherapy, and chemotherapy, may be a powerful anti-cancer therapeutic strategy; however, these therapies still have many problems, including resistance, toxicity, and side effects. Therefore, natural herbal medicine has the potential to be used for cancer therapy because of its low toxicity, fewer side effects, and high success. This study aimed to investigate the anti-cancer effect of 6-shogaol in ovarian cancer cells. 6-shogaol induces ER stress and cell death via the reduction in cell viability, the increase in LDH cytotoxicity, caspase-3 activity, and Ca²⁺ release, and the upregulation of GRP78, p-PERK, p-eIF2α, ATF-4, CHOP, and DR5. Moreover, 6-shogaol treatment medicates endoplasmic reticulum (ER) stress and cell death by upregulating Nox4 and releasing ROS. The knockdown of Nox4 in ovarian cancer cells inhibits ER stress and cell death by blocking the reduction in cell viability and the enhancement of LDH cytotoxicity, caspase-3 activity, Ca²⁺, and ROS release. In gefitinib-resistant ovarian cancer cells, A2780R and OVCAR-3R, 6-shogaol/gefitinib overcomes gefitinib resistance by inhibiting EMT phenomena such as the reduction in E-cadherin, and the increase in N-cadherin, vimentin, Slug, and Snail. Therefore, our results suggest that 6-shogaol exerts a potential anti-cancer effect in ovarian cancer and combination treatment with 6-shogaol and gefitinib may provide a novel anti-tumor therapeutic strategy in gefitinib-resistant ovarian cancer.

CXCR4 promotes gefitinib resistance of Huh7 cells by activating the c-Met signaling pathway

C-X-C chemokine receptor type 4 (CXCR4) expression is associated with poor prognosis of hepatocellular carcinoma (HCC). The aim of this study was to explore the biological role of CXCR4 in gefitinib resistance of HCC. Compared with a normal, non-gefitinib-resistant, human HCC cell line (Huh7), CXCR4 mRNA and protein were highly expressed in gefitinib-resistant Huh7 cells (Huh7-R). Cell proliferation was decreased, and apoptosis was enhanced in Huh7 cells in the presence of gefitinib. These influences conferred by gefitinib treatment on proliferation and apoptosis of Huh7 cells were abolished by CXCR4 overexpression. CXCR4 knockdown reduced the proliferation ability of HuH-7R cells after gefitinib treatment. Importantly, CXCR4 overexpression had no influence on caveolin 1 (Cav-1) expression; similarly, Cav-1 silencing did not cause a substantive change in CXCR4 expression. However, CXCR4 activated Cav-1, c-Met, and Raf-1 in Huh7 cells, whereas Cav-1 silencing repressed the expression of Raf-1 and phosphorylated c-Met in Huh7 cells. CXCR4 overexpression promoted proliferation and repressed apoptosis in gefitinib-treated Huh7 cells, which was partly rescued by PHA-665752 (a c-Met inhibitor) treatment or c-Met deficiency. Finally, we constructed a tumor xenograft model to determine the influence of CXCR4 overexpression on tumor growth of HCC. CXCR4 overexpression accelerated tumor growth of HCC, which was abrogated by c-Met deficiency. These findings demonstrate that CXCR4 overexpression activates c-Met via the Cav-1 signaling pathway, thereby promoting gefitinib resistance of Huh7 cells. Thus, this study highlights novel insights into the mechanism of gefitinib resistance of HCC and CXCR4 may become a potential target for HCC treatment.

A four-component combination derived from Huang-Qin Decoction significantly enhances anticancer activity of irinotecan

Huang-Qin Decoction (HQD) is a classic prescription for diarrhea in Chinese medicine treatment. Recent studies have demonstrated that HQD and its modified formulation PHY906 could ameliorate irinotecan (CPT-11) induced gastrointestinal (GI) toxicity and enhance its anticancer therapeutic efficacy. Nevertheless, which constituents in HQD are effective is still unclear so far. The study aims to screen out the key bioactive components combination from HQD that could enhance the anticancer effect of CPT-11. First, the potential bioactive constituents were obtained through system pharmacology strategy. Then the bioactivity of each constituent was investigated synthetically from the aspects of NCM460 cell migration, TNF-α release of THP-1-derived macrophage and MTT assay in HCT116 cell. The contribution of each constituent in HQD was evaluated using the bioactive index E_i, which taken the content and bioactivity into comprehensive consideration. And then, the most contributing constituents were selected out to form a key-component combination. At last, the bioefficacy of the key-component combination was validated in vitro and in vivo. As a result, a key-component combination (HB4) consisting of four compounds baicalin, baicalein, glycyrrhizic acid and wogonin was screened out. In vitro assessment indicated that HB4 could enhance the effect of CPT-11 on inhibiting cell proliferation and inducing apoptosis in HCT116. Furthermore, the in vivo study confirmed that HB4 and HQD have similar pharmacological activity and could both enhance the antitumor effect of CPT-11 in HCT116 xenograft model. Meanwhile, HB4 could also reduce the CPT-11 induced GI toxicity.

Role of thyroid hormone-integrin αvβ3-signal and therapeutic strategies in colorectal cancers

Thyroid hormone analogues-particularly, L-thyroxine (T₄) has been shown to be relevant to the functions of a variety of cancers. Integrin αvβ3 is a plasma membrane structural protein linked to signal transduction pathways that are critical to cancer cell proliferation and metastasis. Thyroid hormones, T₄ and to a less extend T₃ bind cell surface integrin αvβ3, to stimulate the extracellular signal-regulated kinase 1/2 (ERK1/2) pathway to stimulate cancer cell growth. Thyroid hormone analogues also engage in crosstalk with the epidermal growth factor receptor (EGFR)-Ras pathway. EGFR signal generation and, downstream, transduction of Ras/Raf pathway signals contribute importantly to tumor cell progression. Mutated Ras oncogenes contribute to chemoresistance in colorectal carcinoma (CRC); chemoresistance may depend in part on the activity of ERK1/2 pathway. In this review, we evaluate the contribution of thyroxine interacting with integrin αvβ3 and crosstalking with EGFR/Ras signaling pathway non-genomically in CRC proliferation. Tetraiodothyroacetic acid (tetrac), the deaminated analogue of T₄, and its nano-derivative, NDAT, have anticancer functions, with effectiveness against CRC and other tumors. In Ras-mutant CRC cells, tetrac derivatives may overcome chemoresistance to other drugs via actions initiated at integrin αvβ3 and involving, downstream, the EGFR-Ras signaling pathways.

Interactions between anti-EGFR therapies and cytotoxic chemotherapy in oesophageal squamous cell carcinoma: why clinical trials might have failed and how they could succeed

Purpose

Oesophageal squamous cell carcinoma (ESCC) has a poor prognosis. Advanced tumours are treated with fluoropyrimidine/platinum chemotherapy followed by irinotecan or taxane monotherapy, but resistance is common and new treatments are needed. Approximately 20% of ESCCs carry copy number gain (CNG) of the epidermal growth factor receptor (EGFR) gene. Previous trials show that while anti-EGFR monotherapy benefits biomarker-selected patients with EGFR CNG and/or high EGFR expression, combining anti-EGFR therapies with platinum fluoropyrimidine chemotherapies is not effective, and uncertainty remains regarding the optimal cytotoxic chemotherapy partner for anti-EGFR therapies in ESCC.

Methods

The effects of EGFR CNG on fluoropyrimidine/platinum chemotherapy sensitivity in a cohort of gastroesophageal cancer patients (n = 302) was evaluated. Drug combination studies using the EGFR inhibitor gefitinib with cytotoxic chemotherapies, docetaxel, cisplatin, oxaliplatin and irinotecan, on cell proliferation and cell death of EGFR CNG ESCC cell lines were assessed.

Results

EGFR CNG in gastroesophageal cancer patients was associated with improved overall survival following fluoropyrimidine/platinum chemotherapy. However, co-administration of gefitinib and oxaliplatin or cisplatin was frequently antagonistic in cell-based assays in EGFR CNG ESCC, whereas the combination of gefitinib with docetaxel or irinotecan was more efficacious. Co-administration of gefitinib/docetaxel and sequential administration of docetaxel before gefitinib showed synergy, but docetaxel given after gefitinib was antagonistic.

Conclusion

Gefitinib/platinum co-administration demonstrated antagonism suggesting a possible explanation for the lack of benefit from addition of anti-EGFR therapies to fluoropyrimidine/platinum chemotherapy in trials. Gefitinib/docetaxel co-administration demonstrated synergy suggesting taxanes could be the most effective cytotoxic partner for anti-EGFR therapies in EGFR CNG-positive ESCC, but careful consideration of drug scheduling is required.

NDAT Targets PI3K-Mediated PD-L1 Upregulation to Reduce Proliferation in Gefitinib-Resistant Colorectal Cancer

The property of drug-resistance may attenuate clinical therapy in cancer cells, such as chemoresistance to gefitinib in colon cancer cells. In previous studies, overexpression of PD-L1 causes proliferation and metastasis in cancer cells; therefore, the PD-L1 pathway allows tumor cells to exert an adaptive resistance mechanism in vivo. Nano-diamino-tetrac (NDAT) has been shown to enhance the anti-proliferative effect induced by first-line chemotherapy in various types of cancer, including colorectal cancer (CRC). In this work, we attempted to explore whether NDAT could enhance the anti-proliferative effect of gefitinib in CRC and clarified the mechanism of their interaction. The MTT assay was utilized to detect a reduction in cell proliferation in four primary culture tumor cells treated with gefitinib or NDAT. The gene expression of PD-L1 and other tumor growth-related molecules were quantified by quantitative polymerase chain reaction (qPCR). Furthermore, the identification of PI3K and PD-L1 in treated CRC cells were detected by western blotting analysis. PD-L1 presentation in HCT116 xenograft tumors was characterized by specialized immunohistochemistry (IHC) and the hematoxylin and eosin stain (H&E stain). The correlations between the change in PD-L1 expression and tumorigenic characteristics were also analyzed. (3) The PD-L1 was highly expressed in Colo_160224 rather than in the other three primary CRC cells and HCT-116 cells. Moreover, the PD-L1 expression was decreased by gefitinib (1 µM and 10 µM) in two cells (Colo_150624 and 160426), but 10 µM gefitinib stimulated PD-L1 expression in gefitinib-resistant primary CRC Colo_160224 cells. Inactivated PI3K reduced PD-L1 expression and proliferation in CRC Colo_160224 cells. Gefitinib didn’t inhibit PD-L1 expression and PI3K activation in gefitinib-resistant Colo_160224 cells. However, NDAT inhibited PI3K activation as well as PD-L1 accumulation in gefitinib-resistant Colo_160224 cells. The combined treatment of NDAT and gefitinib inhibited pPI3K and PD-L1 expression and cell proliferation. Additionally, NDAT reduced PD-L1 accumulation and tumor growth in the HCT116 (K-RAS mutant) xenograft experiment. (4) Gefitinib might suppress PD-L1 expression but did not inhibit proliferation through PI3K in gefitinib-resistant primary CRC cells. However, NDAT not only down-regulated PD-L1 expression via blocking PI3K activation but also inhibited cell proliferation in gefitinib-resistant CRCs.

Enhancement by Nano-Diamino-Tetrac of Antiproliferative Action of Gefitinib on Colorectal Cancer Cells: Mediation by EGFR Sialylation and PI3K Activation

Drug resistance complicates the clinical use of gefitinib. Tetraiodothyroacetic acid (tetrac) and nano-diamino-tetrac (NDAT) have been shown in vitro and in xenografts to have antiproliferative/angiogenic properties and to potentiate antiproliferative activity of other anticancer agents. In the current study, we investigated the effects of NDAT on the anticancer activities of gefitinib in human colorectal cancer cells. β-Galactoside α-2,6-sialyltransferase 1 (ST6Gal1) catalyzes EGFR sialylation that is associated with gefitinib resistance in colorectal cancers, and this was also investigated. Gefitinib inhibited cell proliferation of HT-29 cells (K-ras wild-type), and NDAT significantly enhanced the antiproliferative action of gefitinib. Gefitinib inhibited cell proliferation of HCT116 cells (K-ras mutant) only in high concentration, and this was further enhanced by NDAT. NDAT enhancedd gefitinib-induced antiproliferation in gefitinib-resistant colorectal cancer cells by inhibiting ST6Gal1 activity and PI3K activation. Furthermore, NDAT enhanced gefitinib-induced anticancer activity additively in colorectal cancer HCT116 cell xenograft-bearing nude mice. Results suggest that NDAT may have an application with gefitinib as combination colorectal cancer therapy.

Anti-EGFR-iRGD recombinant protein conjugated silk fibroin nanoparticles for enhanced tumor targeting and antitumor efficiency

In this study, we report a novel kind of targeting with paclitaxel (PTX)-loaded silk fibroin nanoparticles conjugated with iRGD–EGFR nanobody recombinant protein (anti-EGFR-iRGD). The new nanoparticles (called A-PTX-SF-NPs) were prepared using the carbodiimide-mediated coupling procedure and their characteristics were evaluated. The cellular cytotoxicity and cellular uptake of A-PTX-SF-NPs were also investigated. The results in vivo suggested that NPs conjugated with the recombinant protein exhibited more targeting and anti-neoplastic property in cells with high EGFR expression. In the in vivo antitumor efficacy assay, the A-PTX-SF-NPs group showed slower tumor growth and smaller tumor volumes than PTX-SF-NPs in a HeLa xenograft mouse model. A real-time near-infrared fluorescence imaging study showed that A-PTX-SF-NPs could target the tumor more effectively. These results suggest that the anticancer activity and tumor targeting of A-PTX-SF-NPs were superior to those of PTX-SF-NPs and may have the potential to be used for targeted delivery for tumor therapies.

Bench to bedside molecular functional imaging in translational cancer medicine: to image or to imagine?

Ongoing research on malignant and normal cell biology has substantially enhanced the understanding of the biology of cancer and carcinogenesis. This has led to the development of methods to image the evolution of cancer, target specific biological molecules, and study the anti-tumour effects of novel therapeutic agents. At the same time, there has been a paradigm shift in the field of oncological imaging from purely structural or functional imaging to combined multimodal structure-function approaches that enable the assessment of malignancy from all aspects (including molecular and functional level) in a single examination. The evolving molecular functional imaging using specific molecular targets (especially with combined positron-emission tomography [PET] computed tomography [CT] using 2- [(18)F]-fluoro-2-deoxy-D-glucose [FDG] and other novel PET tracers) has great potential in translational research, giving specific quantitative information with regard to tumour activity, and has been of pivotal importance in diagnoses and therapy tailoring. Furthermore, molecular functional imaging has taken a key place in the present era of translational cancer research, producing an important tool to study and evolve newer receptor-targeted therapies, gene therapies, and in cancer stem cell research, which could form the basis to translate these agents into clinical practice, popularly termed "theranostics". Targeted molecular imaging needs to be developed in close association with biotechnology, information technology, and basic translational scientists for its best utility. This article reviews the current role of molecular functional imaging as one of the main pillars of translational research.

Treatment with cucurbitacin B alone and in combination with gefitinib induces cell cycle inhibition and apoptosis via EGFR and JAK/STAT pathway in human colorectal cancer cell lines

The epidermal growth factor receptor (EGFR) associated with signaling pathways, such as Janus kinase (JAK)/signal transducer and activator of transcription (STAT), plays an important role in colorectal cancers (CRCs). Gefitinib (Gef) is an orally active inhibitor targeting the adenosine tri phosphate-binding domain of EGFR, and cucurbitacin B (CuB) is a selective inhibitor of JAK/STAT signaling with potent antitumor activity via suppression of STAT3 phosphorylation, but the underlying mechanism is not clear. We aimed to investigate the apoptotic and antiproliferative effects of CuB as a single agent and in combination with Gef on both HT-29 and HCT-116 cell lines. Cell proliferation, cell cycle distribution, and apoptosis were evaluated using viability assay, fluorescent microscopy, cytotoxicity assay, proliferation, DNA fragmentation, and cleaved caspase 3 levels. Real-time polymerase chain reaction and Western blot analyses were performed to determine the expression of relevant genes and proteins including antiapoptotic, proapoptotic, and cell cycle regulation. EGFR, phosphorylated EGFR (pEGFR), STAT3, and pSTAT3 proteins were evalutaed with Western blot analysis. Our results showed that, compared to CuB alone, CuB plus Gef treatment caused a significant growth and cell cycle inhibition and induced apoptosis in both cell lines. Also CuB plus Gef treatment decreased DNA synthesis rate more effectively than CuB alone. Treatment with CuB alone and in combination with Gef decreased the expression levels of B-Cell CLL/Lymphoma 2 (Bcl-2), BCL2-like 1 (BCL2L1), cyclin D1, pSTAT3, and pEGFR and increased the expression levels of Bcl-2-like protein 4, Bcl-2 homologous antagonist/killer, Bcl-2-associated death promoter, Bcl-2-like protein 11, and p27kip1 levels. Our results suggest that treatment with CuB alone and more likely in combination with Gef may be a considerable alternative therapeutic approach for CRC, at least in vitro.

Modification of topoisomerases in mammospheres derived from breast cancer cell line: clinical implications for combined treatments with tyrosine kinase inhibitors

BACKGROUND

Accumulating evidences suggest that tumors are driven by a small population of cells, termed "cancer stem cells" (CSCs), which may be resistant to current therapeutic approaches. In breast carcinoma, the CSCs have been identified as a CD44+/CD24- cell population. These rare cells are able to grow as non-adherent sphere-like structures, termed "mammospheres", which enables their isolation and expansion in culture. To design efficient strategies for the complete eradication of CSCs, it is important to identify enzymes and proteins that are known as anti-cancer targets, and differ in their properties from those present in the none CSCs. Here we investigated the activity and expression of type I and type II DNA topoisomerases (topo I and topo II) in CSCs and their response to anti-topoisomerase inhibitors.

METHODS

MCF7 breast cancer cells, PC3 prostate cancer cells and 4 T1-Luc-Oct3/4pG mouse mammary carcinoma cells were grown on low-attachment dishes in specific medium and allowed to form spheres. Enrichment of CSC population was verified by immunostaining, flow cytometry or fluorescent microscopy imaging. Nuclear protein extracts were prepared and topoisomerases activity and protein levels were determined. Cell viability was examined by the MTT and Neutral Red assays.

RESULTS

Unlike the adherent MCF7 cell line, topo I activity is decreased and topo II activity is increased in the CSCs. However, the relative levels of the enzyme proteins were similar in both mammospheres and adherent cells. Topo I activity in mammospheres is regulated, at least in part, by PARP-1, as observed by the recovery of topo I activity after treatment with PARP-1 inhibitor 3-Aminobenzamide. Mammosphere-derived cells show reduced sensitivity to topo I inhibitor, camptothecin, and increased sensitivity to topo II inhibitor etoposide. Intact mammospheres show increased resistance to both drugs. A combined treatment of intact mammospheres with either CPT and gefitinib, or etoposide and erlotinib, increased the anti-cancer effect of both drugs.

CONCLUSIONS

The data of this study suggest that the understanding of biological behavior of essential enzymes such as topoisomerases, in CSCs' progression and early stages of tumor development, is important for developing new strategies for cancer treatment as well as new therapies for advanced disease.

Cetuximab-mediated ADCC activity is correlated with the cell surface expression level of EGFR but not with the KRAS/BRAF mutational status in colorectal cancer

Cetuximab, an IgG1 monoclonal antibody against the epidermal growth factor receptor (EGFR), is widely used for the treatment of metastatic colorectal cancer (mCRC). One of the mechanisms of action is considered to be antibody-dependent cell-mediated cytotoxicity (ADCC) triggered by Fcγ-R on natural killer cells. However, whether ADCC is associated with EGFR expression and/or the mutational status of EGF downstream effectors (KRAS and BRAF) in colorectal cancer (CRC) remains unclear. The aim of the present study was to verify whether ADCC activities are associated with the cell surface expression levels of EGFR and/or the mutational status of KRAS and BRAF. Five human CRC cell lines with different cell surface expression levels of EGFR and different KRAS and BRAF mutational statuses were selected to evaluate ADCC activity using peripheral blood mononuclear cells (PBMCs) from healthy human donors. Furthermore, tumor cells from resected specimens of CRC patients were used to evaluate the cell surface expression level of EGFR using immunohistochemistry and the KRAS and BRAF mutational statuses using direct sequencing, while the ADCC activity was examined using PBMCs from the same CRC patients. A strong correlation was observed between the expression levels of EGFR and the ADCC activities in the cell lines (correlation coefficient: 0.949; P=0.003). Of the 13 resected specimens, a high ADCC activity level was significantly observed in tumor cells with high expression levels of cell surface EGFR, when compared with that in the tumor cells with low expression levels (P=0.027). In both CRC cell lines and tumor cells from CRC patients, the ADCC activities were significantly associated with the cell surface expression levels of EGFR [standard partial regression coefficients: 0.911 (P=0.017) and 0.660 (P=0.018), respectively], but not with the mutational status of KRAS and BRAF [standard partial regression coefficient: -0.101 (P=0.631) and 0.160 (P=0.510), respectively]. Cetuximab-mediated ADCC activity may be correlated with the cell surface expression level of EGFR, regardless of the mutational statuses of KRAS and BRAF, in CRC.

Formulation and evaluation of irinotecan suppository for rectal administration

Irinotecan suppository was prepared using the moulding method with a homogeneous blend. A sensitive and specific fluorescence method was developed and validated for the determination of irinotecan in plasma using HPLC. The pharmacokinetics of intravenous administered and rectal administered in rabbits was investigated. Following a single intravenous dose of irinotecan (50 mg/kg), the plasma irinotecan concentration demonstrated a bi-exponential decay, with a rapid decline over 15 min. C_max, t_1/2, AUC_0–30h and AUC_0-∞ were 16.1 ± 2.7 g/ml, 7.6 ± 1.2 h, 71.3 ± 8.8 μg·h/ml and 82.3 ± 9.5 μg·h/ml, respectively. Following rectal administration of 100 mg/kg irinotecan, the plasma irinotecan concentration reached a peak of 5.3 ± 2.5 μg/ml at 4 h. The AUC_0–30h and AUC_0-∞ were 32.2 ± 6.2 μg·h/ml and 41.6 ± 7.2 μg·h/ml, respectively. It representing ∼50.6% of the absolute bioavailability.

MicroRNA-147 induces a mesenchymal-to-epithelial transition (MET) and reverses EGFR inhibitor resistance

Background

The epithelial-mesenchymal transition (EMT) is a key developmental program that is often activated during cancer progression and may promote resistance to therapy. An analysis of patients (n = 71) profiled with both gene expression and a global microRNA assessment (∼415 miRs) identified miR-147 as highly anti-correlated with an EMT gene expression signature score and postulated to reverse EMT (MET).

Methods and Findings

miR-147 was transfected into colon cancer cells (HCT116, SW480) as well as lung cancer cells (A-549). The cells were assessed for morphological changes, and evaluated for effects on invasion, motility, and the expression of key EMT markers. Resistance to chemotherapy was evaluated by treating cells with gefitinib, an EGFR inhibitor. The downstream genes regulated by miR-147 were assayed using the Affymetrix GeneChip U133 Plus2.0 platform. miR-147 was identified to: 1. cause MET primarily by increasing the expression of CDH1 and decreasing that of ZEB1; 2. inhibit the invasion and motility of cells; 3. cause G1 arrest by up-regulating p27 and down-regulating cyclin D1. miR-147 also dramatically reversed the native drug resistance of the colon cancer cell line HCT116 to gefitinib. miR-147 significantly repressed Akt phosphorylation, and knockdown of Akt with siRNA induced MET. The morphologic effects of miR-147 on cells appear to be attenuated by TGF-B1, promoting a plastic and reversible transition between MET and EMT.

Conclusion

miR-147 induced cancer cells to undergo MET and induced cell cycle arrest, suggesting a potential tumor suppressor role. miR-147 strikingly increased the sensitivity to EGFR inhibitor, gefitinib in cell with native resistance. We conclude that miR-147 might have therapeutic potential given its ability to inhibit proliferation, induce MET, as well as reverse drug sensitivity.

Topoisomerase I as a target of erlotinib and gefitinib: efficacy of combined treatments with camptothecin

Topoisomerases are essential nuclear enzymes that work to resolve topological problems that normally occur during DNA metabolism. Their involvement in crucial DNA associated-processes, such as replication, transcription and repair, mark them as a target of chemotherapeutic drugs such as camptothecins (CPTs). Therefore, finding other agents that may alter their activity is of great importance. Previous data showed that certain tyrosine kinase antagonists, tyrphostins, inhibit the catalytic activity of the cellular topoisomerase I (topo I). We examined the effect of clinically used tyrosine kinase inhibitors (TKIs), erlotinib and gefitinib, on topo I in breast and prostate cancer cells. While erlotinib and gefitinib inhibit cellular topo I in treated cells without affecting the levels of the enzyme protein, in vitro assays show that erlotinib, but not gefitinib, inhibits the DNA relaxation activity of purified topo I. Erlotinib was found to reduce the DNA-binding ability of topo I, however, the reduction in topo I activity in gefitinib-treated cells is probably due to post-translational modifications of the enzyme protein. A combined treatment of either erlotinib or gefitinib with CPT increased the effect of CPT on the activity of cellular topo I, which supports the increased anticancer effect observed in MCF7 cells. These results suggest that topo I is a novel target of erlotinib and a combination of TKIs with topo I inhibitors may be an effective treatment for breast cancer.

Synergistic interactions between camptothecin and EGFR or RAC1 inhibitors and between imatinib and Notch signaling or RAC1 inhibitors in glioblastoma cell lines

PURPOSE

The current treatment strategies for glioblastoma have limited health and survival benefits for the patients. A common obstacle in the treatment is chemoresistance. A possible strategy to evade this problem may be to combine chemotherapeutic drugs with agents inhibiting resistance mechanisms. The aim with this study was to identify molecular pathways influencing drug resistance in glioblastoma-derived cells and to evaluate the potential of pharmacological interference with these pathways to identify synergistic drug combinations.

METHODS

Global gene expressions and drug sensitivities to three chemotherapeutic drugs (imatinib, camptothecin and temozolomide) were measured in six human glioblastoma-derived cell lines. Gene expressions that correlated to drug sensitivity or resistance were identified and mapped to specific pathways. Selective inhibitors of these pathways were identified. The effects of six combinations of inhibitors and chemotherapeutic drugs were evaluated in glioblastoma-derived cell lines. Drug combinations with synergistic effects were also evaluated in non-cancerous epithelial cells.

RESULTS

Four drug combinations had synergistic effects in at least one of the tested glioblastoma-derived cell lines; camptothecin combined with gefitinib (epidermal growth factor receptor inhibitor) or NSC 23766 (ras-related C3 botulinum toxin substrate 1 inhibitor) and imatinib combined with DAPT (Notch signaling inhibitor) or NSC 23766. Of these, imatinib combined with DAPT or NSC 23766 did not have synergistic effects in non-cancerous epithelial cells. Two drug combinations had at least additive effects in one of the tested glioblastoma-derived cell lines; temozolomide combined with gefitinib or PF-573228 (focal adhesion kinase inhibitor).

CONCLUSION

Four synergistic and two at least additive drug combinations were identified in glioblastoma-derived cells. Pathways targeted by these drug combinations may serve as targets for future drug development with the potential to increase efficacy of currently used/evaluated chemotherapy.

Panitumumab combined with irinotecan for patients with KRAS wild-type metastatic colorectal cancer refractory to standard chemotherapy: a GERCOR efficacy, tolerance, and translational molecular study

BACKGROUND

The purpose of this study was to evaluate the combination of panitumumab and irinotecan in patients with KRAS wild-type metastatic colorectal cancer refractory to standard chemotherapy (oxaliplatin, fluoropyrimidines-irinotecan and bevacizumab).

PATIENTS AND METHODS

KRAS status was first determined locally but subsequent validation of KRAS status and additional screenings (rare KRAS, NRAS, BRAF mutations and EGFR copy number) were centrally assessed. Patients received panitumumab (6 mg/kg) and irinotecan (180 mg/m²) every 2 weeks.

RESULTS

Sixty-five eligible patients were analyzed. The objective response rate (ORR) was 29.2% [95% confidence interval (95% CI) 18.2-40.3]. Median progression-free and overall survivals were 5.5 and 9.7 months, respectively. Most frequent grade 3/4 toxic effects were skin 32.3%, diarrhea 15.4% and neutropenia 12.3%. Tissue samples were available for 60 patients. For the confirmed KRAS wild-type population codon 12 or 13 mutation (n = 54), ORR was 35.2% (95% CI 22.4.1-47.9). Thirteen patients had a NRAS, a BRAF or a rare KRAS mutation, and no tumor response was observed in this subgroup when compared with 46.3% (95% CI 31.1-61.6) ORR in the subgroup of 41 patients with no identified mutation.

CONCLUSION

Panitumumab and irinotecan is an active third-line regimen in a well-defined population based on biomarkers. ClinicalTrials.gov Identifier NCT00655499.

Serum heparan sulfate concentration is correlated with the failure of epidermal growth factor receptor tyrosine kinase inhibitor treatment in patients with lung adenocarcinoma

INTRODUCTION

The epidermal growth factor receptor (EGFR) mutation status is a validated biomarker for the stratification of EGFR-tyrosine kinase inhibitor (EGFR-TKIs) treatment in patients with non-small cell lung cancer (NSCLC); however, its use is limited in patients with wild-type EGFR, and new biomarkers are needed. We hypothesized that the serum concentration of heparan sulfate (HS), which activates oncogenic growth factor receptor signaling through EGFR and non-EGFR signaling pathways, may be a novel glycobiological biomarker for EGFR-TKIs treatment in NSCLC.

METHODS

The pretreatment serum HS concentrations were determined using enzyme-linked immunosorbent assay in 83 patients with stage IV non-small cell lung adenocarcinoma who received EGFR-TKIs treatment. The relationship between the serum HS concentrations and patient characteristics, tumor response, progression-free survival (PFS), and overall survival (OS) were analyzed.

RESULTS

Patient sex, performance status, smoking history, and EGFR mutation status were associated with tumor response. The serum HS concentrations were significantly higher among patients with progressive disease than among those without progressive disease (p = 0.003). Furthermore, the serum HS concentrations were strongly associated with a poor PFS and OS in a univariate Cox analysis (p = 0.0022 and p = 0.0003, respectively). A stratified multivariate Cox model according to the EGFR mutation status showed that higher HS concentrations were significantly associated with a shorter PFS and OS (p = 0.0012 and p = 0.0003).

CONCLUSION

We concluded that a high-serum HS concentration was strongly related to a poor treatment outcome of EGFR-TKIs and may be a promising noninvasive and repeatable glycobiological biomarker in cancer treatment.

Phase I study of irinotecan and gefitinib in patients with gefitinib treatment failure for non-small cell lung cancer

Background:

Currently, no effective treatments exist for non-small cell lung cancer (NSCLC) after failure of gefitinib therapy. Pre-clinical studies have demonstrated that gefitinib-resistant NSCLC cells are more sensitive to irinotecan than parental cells, and that combined administration of irinotecan and gefitinib has a synergistic additive effect. We conducted a phase I study to evaluate the combination of irinotecan and gefitinib as a therapeutic option for NSCLC patients with progressive disease (PD) after initial gefitinib treatment.

Methods:

Eligibility criteria included histologically confirmed NSCLC, age range of 20–74 years, refractory to or relapsed after gefitinib treatment, one or more previous chemotherapy regimens, Eastern Cooperative Oncology Group performance status 0–2, adequate organ function, and informed consent. Patients were treated with irinotecan on days 1 and 15, and treated daily with gefitinib from day 2 every 4 weeks. The treatment was continued until disease progression. The gefitinib dose was fixed at 250 mg. Irinotecan dosing started at 50 mg m⁻² and was escalated in patients by 25 mg m⁻² increments up to a maximum dose of 150 mg m⁻².

Results:

Twenty-seven patients were enrolled: male/female=14/13; median age=60 (45–75); histology, adenocarcinoma/non-adenocarcinoma=25/2; performance status 0–1/2=19/8; previous response to gefitinib, partial response/stable disease/PD=21/2/4. Dose-limiting toxicities were observed in 2 patients at level 3. Maximum tolerated dose was not determined, and the full dose of irinotecan could be combined with the full dose of gefitinib. The disease control rate (DCR) and response rate (RR) were 69.2 and 26.9%, respectively. For 12 patients at level 5 (the recommended phase II dose), the DCR and RR were 75.0% and 41.7%, respectively. The median treatment cycles were 4; median time to treatment failure, 57 days (95% confidence interval (CI), 32–82 days); median overall survival, 244 days (95% CI, 185–303 days); and 1-year survival rate, 32.6%.

Conclusion:

The combination of irinotecan and gefitinib was well tolerated and potentially beneficial for NSCLC patients failing initial gefitinib monotherapy.

Phosphorylated insulin-like growth factor 1 receptor is implicated in resistance to the cytostatic effect of gefitinib in colorectal cancer cells

INTRODUCTION

The ability of certain cancer cells to maintain signaling via the phosphoinositide-3-kinase/Akt and/or Ras/mitogen-activated protein kinase (MAPK) pathways has been repeatedly involved in resistance to epidermal growth factor receptor (EGFR) inhibition.

DISCUSSION

We investigated the potential mechanisms of the uncoupling of EGFR from its downstream signals in colorectal cancer (CRC) cells. Alternative growth factor receptors and regulation of downstream pathways in different gefitinib-responsive cell lines were determined. Basal insulin-like growth factor receptor-1β (IGFR-1β) phosphorylation was undetectable or present at very low levels in highly gefitinib-responsive cell lines and was present at strikingly high levels in less responsive cell lines. Further analysis of cell lines representing the most sensitive (Lovo), moderately sensitive (HT29), and most resistant (HCT116) strains was treated with an IGFR-1 inhibitor (AG1024), gefitinib, or both, revealing that elevated IGFR-1β phosphorylation can compensate for the loss of EGFR signaling function. Increased insulin-like growth factor II expression induced by gefitinib or heterodimerization of EGFR and IGFR-1β may trigger IGFR-1β signal transduction via activation of Akt and MAPK. In addition, high levels of EGFR and IGFR-1β phosphorylation were detected in CRC tumor tissue. We also showed that gefitinib- and/or AG1024-induced cytostatic effects could be mediated by glycogen synthase kinase-3β (GSK-3β) activation. Our data suggest that the crosstalk between EGFR and IGFR-1β signaling are likely to contribute to resistance of CRC cells to gefitinib and that measurement of GSK-3β activation may present a potential biomarker for evaluating the antitumor efficacy of receptor tyrosine kinase inhibition.

Epidermal growth factor receptor inhibition augments the expression of MHC class I and II genes

PURPOSE

Diverse immune-related effects occur with the use of epidermal growth factor receptor inhibitors (EGFRI). In addition to the cutaneous inflammation induced by EGFRIs, these agents have been associated with the exacerbation of autoimmune skin disease and contact hypersensitivity, antiviral effects, and fatal alveolar damage in the setting of lung transplantation. Because EGFR ligands can modulate MHC class I (MHCI) and II (MHCII) molecule expression, we hypothesized that some of the immune-related effects of EGFRIs are due to direct effects on the expression of MHCI and/or MHCII molecules.

EXPERIMENTAL DESIGN

Primary human keratinocytes and a malignant keratinocyte cell line (A431) were treated with EGFRIs alone or prior to IFN-γ, a potent inducer of MHCI and MHCII molecule expression. CIITA, MHCI, and MHCII RNA expression was measured using quantitative real-time reverse transcriptase PCR, and cell surface MHCI and MHCII protein expression was measured using flow cytometry. Skin biopsies from patients were analyzed for MHCI and MHCII protein expression before and during therapy with an EGFRI using immunohistochemistry.

RESULTS

Both EGFR tyrosine kinase inhibitors and ligand-blocking antibodies (cetuximab) augmented the induction of MHCI and MHCII molecules by IFN-γ in primary and malignant human keratinocytes. Unexpectedly, the increase in MHCI protein expression did not require the presence of IFN-γ. Consistent with these in vitro findings, skin biopsies from cancer patients exhibited increased epidermal MHCI protein expression during therapy with an EGFRI as well as increases in MHCI and MHCII molecule RNA.

CONCLUSIONS

These studies suggest that EGFRIs may influence immune/inflammatory responses by directly modulating MHC expression. Clin Cancer Res; 17(13); 4400-13. ©2011 AACR.

Cetuximab enhances the activities of irinotecan on gastric cancer cell lines through downregulating the EGFR pathway upregulated by irinotecan

PURPOSE : Treatment effects of advanced gastric cancer (AGC) are unsatisfactory, and novel therapeutic approaches are much needed. The epidermal growth factor receptor (EGFR) monoclonal antibody cetuximab inhibits the growth of several human cancer cells but has been tested rarely for the treatment of GC. The synergy between cetuximab and irinotecan has been reported in colorectal cancer, but the mechanisms are still not fully clarified. Consequently, we hypothesized cetuximab/irinotecan combination should enhance the antitumor activity of irinotecan in GC cells. METHODS : The in vitro antiproliferative, pro-apoptotic, cell cycle arrest effects and induction of senescence were examined in SGC-7901 and MKN-45 GC cell lines. The effects of cetuximab or irinotecan as single agents or the combination on the expression of p53, p16, and EGFR signaling pathways were also studied. RESULTS : The study revealed that cetuximab alone did not show any antiproliferative, pro-apoptotic, cell cycle arrest or cellular senescence effect on GC cells but when combined with irinotecan synergistically inhibits GC cell proliferation and induces apoptosis and G2/M phase arrest. Irinotecan increases phosphorylation of EGFR, MAPK, and AKT and decreases the expression of P27(Kip1), which could be all abrogated by its combination with cetuximab. The combination could also inhibit the expression of Cyclin D1 and phosphorylated mTOR while had no impact on p53, p16, PTEN, and HIF-1alpha. CONCLUSIONS : Cetuximab enhances the activities of irinotecan on GC cells via the downregulation of the EGFR pathway upregulated by irinotecan. Combination therapy with cetuximab and irinotecan, a novel therapeutic approach, warrants further study in GC.

Impact of serum hepatocyte growth factor on treatment response to epidermal growth factor receptor tyrosine kinase inhibitors in patients with non-small cell lung adenocarcinoma

PURPOSE

The epidermal growth factor receptor (EGFR) mutation status has emerged as a validated biomarker for predicting the response to treatment with EGFR-tyrosine kinase inhibitors (EGFR-TKI) in patients with non-small cell lung cancer. However, the responses to EGFR-TKIs vary even among patients with EGFR mutations. We studied several other independently active biomarkers for EGFR-TKI treatment.

EXPERIMENTAL DESIGN

We retrospectively analyzed the serum concentrations of 13 molecules in a cohort of 95 patients with non-small cell lung adenocarcinoma who received EGFR-TKI treatment at three centers. The pretreatment serum concentrations of amphiregulin, β-cellulin, EGF, EGFR, epiregulin, fibroblast growth factor-basic, heparin-binding EGF-like growth factor, hepatocyte growth factor (HGF), platelet-derived growth factor β polypeptide, placental growth factor, tenascin C, transforming growth factor-α, and vascular endothelial growth factor (VEGF) were measured using enzyme-linked immunosorbent assay and a multiplex immunoassay system. The associations between clinical outcomes and these molecules were evaluated.

RESULTS

The concentrations of HGF and VEGF were significantly higher among patients with progressive disease than among those without progressive disease (P < 0.0001). HGF and VEGF were strongly associated with progression-free survival (PFS) and overall survival (OS) in a univariate Cox analysis (all tests for hazard ratio showed P < 0.0001). A stratified multivariate Cox model according to EGFR mutation status (mutant, n = 20; wild-type, n = 23; unknown, n = 52) showed that higher HGF levels were significantly associated with a shorter PFS and OS (P < 0.0001 for both PFS and OS). These observations were also consistent in the subset analyses.

CONCLUSIONS

Serum HGF was strongly related to the outcome of EGFR-TKI treatment. Our results suggest that the serum HGF level could be used to refine the selection of patients expected to respond to EGFR-TKI treatment, warranting further prospective study.

Combination of RET siRNA and irinotecan inhibited the growth of medullary thyroid carcinoma TT cells and xenografts via apoptosis

Medullary thyroid carcinoma (MTC) is a rare endocrine tumor that frequently metastasizes, and treatment with irinotecan (CPT-11) is limited because of side effects. Mutations in the Rearranged during transfection (RET) proto-oncogene are considered the causative event of MTC. The objective of this study was to examine whether small interfering RNA (siRNA) and its combined treatment with CPT-11 could inhibit MTC cell growth in vitro and in vivo. The transfection of RET siRNA suppressed RET expression, reduced proliferation, and increased caspase-3/7 activity via the down-regulation of Bcl-2 expression. Combined treatments with CPT-11 or SN-38 significantly increased caspase 3/7 activity compared with RET siRNA, CPT-11 or SN-38 treatment alone. Importantly, intratumoral injection of RET siRNA along with intravenous injection of CPT-11 significantly inhibited the tumor growth of MTC xenografts via an increased apoptotic effect. These findings that RET siRNA enhanced sensitivity for CPT-11 will provide a novel strategy for the treatment of MTC with RET mutation.

Phase II study of paclitaxel and irinotecan with intercalated gefitinib in patients with advanced non-small-cell lung cancer

OBJECTIVES

We conducted a phase II study of combination chemotherapy with paclitaxel (Pac) and irinotecan (CPT) alternating with gefitinib (Gef) to determine the qualitative and quantitative toxicities and efficacy of this combination against advanced non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Patients with stage IIIB or IV NSCLC were treated with CPT at 60 mg/m2 and Pac at 160 mg/m2 on day 1 followed by Gef at 250 mg per day on days 8 to 14 every 3 weeks.

RESULTS

Between April 2005 and March 2006, 16 patients received the chemotherapy with Pac and CPT alternating with Gef. Eleven patients received 4 to 6 cycles, except for 5 patients who discontinued treatment in the second or third cycles because of disease progression in 2, grade 3 pneumonitis with pulmonary infiltration in 2, and decreased performance status in 1. Grade 3 toxicities were neutropenia, an increased glutamic pyruvic transaminase level, allergy, pneumonitis, anorexia, and fatigue. Elevation of the serum glutamic oxaloacetic transaminase level after 1 cycle was the only grade 4 toxicity. Seven of 16 patients achieved a partial response and the overall response rate in the prospective study was 43.8%. The median survival time was 18.1 months. The 1- and 2-year survival rates were 56.3% and 43.8%, respectively.

CONCLUSION

Pac and CPT combined with Gef was not effective enough for NSCLC.

Antitumor activity of erlotinib in combination with gemcitabine in in vitro and in vivo models of KRAS-mutated pancreatic cancers

Erlotinib treatment in combination with gemcitabine is a standard therapy for patients with locally advanced pancreatic cancer in many countries, including the US and the EU. Since mutations of the K-ras oncogene (KRAS) occur in approximately 90% of pancreatic cancers, we examined the antitumor activity of erlotinib in combination with gemcitabine in KRAS-mutated pancreatic cancer cell lines, HPAC and Capan-1, which have the KRAS mutation G12D and G12V, respectively. We analyzed the mode of inhibition of in vitro tumor cell proliferation by means of a combination index and found that a combination treatment of erlotinib plus gemcitabine had an additive effect in the two cell lines. We then examined the effect of erlotinib and gemcitabine on the phosphorylation of epidermal growth factor receptor (EGFR). Erlotinib strongly suppressed, while gemcitabine augmented the phosphorylation of EGFR, which was completely blocked by erlotinib in the two cell lines. An in vivo tumor growth inhibition test was then performed using the HPAC tumor xenograft model. The combination therapy of erlotinib and gemcitabine resulted in a significant inhibition of tumor growth compared with erlotinib or gemcitabine monotherapy. To the best of our knowledge, this is the first study to show the combination effect of erlotinib and gemcitabine in vivo using a xenograft model of a KRAS-mutated pancreatic cancer cell line.

Molecular mechanism underlying the synergistic interaction between trifluorothymidine and the epidermal growth factor receptor inhibitor erlotinib in human colorectal cancer cell lines

The pyrimidine trifluorothymidine (TFT) inhibits thymidylate synthase (TS) and can be incorporated into the DNA. TFT, as part of TAS-102, is clinically evaluated in phase II studies as an oral chemotherapeutic agent. Erlotinib is a tyrosine kinase inhibitor of the epidermal growth factor receptor (EGFR) that is often deregulated in colorectal cancer. This study investigated molecular mechanisms underlying the cytotoxic actions of the combination of an EGFR-tyrosine kinase inhibitor with TFT in colorectal cancer cells Caco2, WiDR, Lovo92, and Colo320. Drug interactions were examined by the sulforhodamine B assay and subsequent combination index (CI) analyses, cell cycle effects by FACS analysis of propidium iodide stained cells, Akt, MAPK and EGFR phosphorylation and expression levels by Western blotting and TS activity by the TS in situ assay. All combination schedules were synergistic in wt-EGFR expressing (but with mutated downstream pathways) WiDR and Lovo92 (CI 0.4-0.8) and very synergistic in Caco2 cells (with wt-EGFR and functional downstream pathways; CI 0.1-0.3), but in EGFR-lacking Colo320 cells, no additional activity was found (CI 1.0-1.2). Synergism was mostly related to the induction of cell cycle arrest and an erlotinib-mediated inhibition of the pro-survival signaling through Akt and MAPK that was activated (phosphorylated) by TFT. Erlotinib inhibited TS activity in EGFR-expressing cell lines, probably due to cell cycle arrest in the G(1) phase. TS activity was slightly lower in the combinations, probably due to cell cycle interference. Taken together, the combination of erlotinib with TFT seems to present a potential strategy in the field of molecular therapeutics.

Inhibition of epidermal growth factor receptor over-expressing cancer cells by the aphorphine-type isoquinoline alkaloid, dicentrine

The extraordinary relevance of EGFR in tumour biology makes it an exquisite molecular target for tumour therapy. Despite considerable success with these EGFR tyrosine kinase inhibitors in cancer therapy, resistance against these chemical compounds develops owing to the selection of point-mutated variants of EGFR. Therefore, there is an urgent need for the identification of novel EGFR tyrosine kinase inhibitors for treating tumours with such EGFR mutants. We found a preferential cytotoxicity of dicentrine towards U87MG.DeltaEGFR-transduced with a constitutively deletion-activated EGFR expression vector as compared to non-transduced wild-type U87MG cells. As determined by microarray-based mRNA expression profiling, this preferential cytotoxicity was accompanied with an activation of BRCA1-mediated DNA damage response, p53 signalling, G1/S and G2/M cell cycle regulation, and aryl hydrocarbon receptor pathways. The activation of these signalling routes might be explained by the fact that dicentrine intercalates DNA and induces DNA strand break by inhibition of DNA topoisomerases. The cell cycle might be arrested by dicentrine-induced DNA lesions.

Reverse resistance to radiation in KYSE-150R esophageal carcinoma cell after epidermal growth factor receptor signal pathway inhibition by cetuximab

BACKGROUND AND PURPOSE

The purpose of our study is to examine the capacity of cetuximab to reverse radiation resistance and investigate molecular mechanisms in human radiation-resistant esophageal carcinoma cell line KYSE-150R.

MATERIALS AND METHODS

The radioresistant cell line KYSE-150R was established by using fractionated irradiation (FIR). The KYSE-150R cell line was exposed to radiation, treatment with cetuximab, and combined treatment. Cell cycle distribution and apoptosis were analyzed using flow cytometry. Radiation survival was analyzed using clonogenic assays. RT(2) profiler PCR array was performed to analyze EGF/PDGF signaling pathway genes.

RESULTS

The established esophageal carcinoma cell line KYSE-150R showed higher radioresistance than parental cell line. Cetuximab could reverse the radiation resistance of KYSE-150R cells. Cell cycle analysis showed that combination with radiation and cetuximab resulted in the accumulation of cells in G1 and G2/M phases, with the reduction of cells within the S phase. Cetuximab enhanced the apoptosis induced by radiation. RT(2) profiler array showed that some intracellular signaling genes deriving from EGF/PDGF signaling pathway regulated by cetuximab.

CONCLUSIONS

Irradiation combined with EGFR blocked by cetuximab may reverse the resistance to radiation in radioresistant esophageal carcinoma cell. The mechanisms may include cell cycle perturbation and enhancement of radiation-induced apoptosis. Further studies are needed to evaluate the role of cetuximab in combination with radiotherapy in the management of esophageal carcinoma.

Tyrosine kinase inhibitor enhances the bioavailability of oral irinotecan in pediatric patients with refractory solid tumors

PURPOSE

To assess the maximum-tolerated dosages (MTDs), and dose-limiting toxicities (DLTs) of the epidermal growth factor receptor inhibitor gefitinib and of intravenous (IV) irinotecan when administered together in children with refractory solid tumors. To assess the effect of gefitinib on the pharmacokinetics of IV irinotecan and on the bioavailability of a single oral dose of irinotecan.

PATIENTS AND METHODS

IV irinotecan (15 or 20 mg/m(2)) was given daily for 5 days of 2 consecutive weeks. Oral gefitinib (150 or 112.5 mg/m(2)) was concomitantly given daily for 12 or 21 days. A single oral dose of irinotecan was given on day 9 of course 2 to allow pharmacokinetic analysis.

RESULTS

The study enrolled 29 patients with recurrent solid tumors. The 21-day regimen of oral gefitinib with irinotecan was not tolerated. Diarrhea was the most common DLT. The MTD of the combination regimen was 15 mg/m(2)/d of IV irinotecan for 5 days of 2 consecutive weeks and 112.5 mg/m(2)/d of gefitinib given for 12 days. Gefitinib increased the bioavailability of oral irinotecan by four-fold over that observed in historical controls (median, 0.09 v 0.42; P < .000001), reducing the apparent clearance (an inverse measure of exposure) of irinotecan and SN-38 by 37% and 38%, respectively (P < .0001). A partial response was observed in a patient with refractory Ewing sarcoma.

CONCLUSION

IV irinotecan given with 12 days of oral gefitinib is well tolerated in children. We observed one partial response. Gefitinib significantly enhances the bioavailability of oral irinotecan. This combination warrants further investigation, particularly with orally administered irinotecan.

Doxorubicin and mitoxantrone drug eluting beads for the treatment of experimental peritoneal carcinomatosis in colorectal cancer

We investigated the therapeutic efficiency of sulfonate-modified polyvinyl alcohol beads loaded with doxorubicin, irinotecan or mitoxantrone in vitro and in vivo in a model of experimental peritoneal carcinomatosis (PC). In vitro, cell proliferation was efficiently impaired by doxorubicin drug eluting bead (DEB) treatment while mitoxantrone DEBs were less effective than. Irinotecan showed little effect for both DEBs and free drug. Apoptosis was not different between free mitoxantrone and the DEB form while more apoptosis induction was observed in cells incubated with free doxorubicin and irinotecan. Experimental PC was produced in mice. The therapeutic efficiency of either mitoxantrone and doxorubicin DEB or free drugs were compared. Mice were treated either once on day 12 or by 3 repetitive applications on days 7, 10 and 12. Mice treated by DEBs showed less weight loss and mortality. Therapeutic effect was determined by measuring tumor volume and tumor load on the day 15 after tumor inoculation. For the single application on the day 12, an advantage could be observed for the free drugs. After 3 repeated injections of both free and mitoxantrone DEB no difference in tumor load or tumor volume could be observed. Least tumor load and tumor volume was observed in mice that received 3 repeated injections of doxorubicin DEB. No animal survived 3 injections of free doxorubicin. We conclude that bead encapsulation of chemotherapeutic drugs may show the advantage of less toxicity in peritoneal spread of colorectal cancer.

Epidermal growth factor receptor lacking C-terminal autophosphorylation sites retains signal transduction and high sensitivity to epidermal growth factor receptor tyrosine kinase inhibitor

Constitutively active mutations of epidermal growth factor receptor (EGFR) (delE746_A750) activate downstream signals, such as ERK and Akt, through the phosphorylation of tyrosine residues in the C-terminal region of EGFR. These pathways are thought to be important for cellular sensitivity to EGFR tyrosine kinase inhibitors (TKI). To examine the correlation between phosphorylation of the tyrosine residues in the C-terminal region of EGFR and cellular sensitivity to EGFR TKI, we used wild-type (wt) EGFR, as well as the following constructs: delE746_A750 EGFR; delE746_A750 EGFR with substitution of seven tyrosine residues to phenylalanine in the C-terminal region; and delE746_A750 EGFR with a C-terminal truncation at amino acid 980. These constructs were transfected stably into HEK293 cells and designated HEK293/Wt, HEK293/D, HEK293/D7F, and HEK293/D-Tr, respectively. The HEK293/D cells were found to be 100-fold more sensitive to EGFR TKI (AG1478) than HEK293/Wt. Surprisingly, the HEK293/D7F and HEK293/D-Tr cells, transfected with EGFR lacking the C-terminal autophosphorylation sites, retained high sensitivity to EGFR TKI. In these three high-sensitivity cells, the ERK pathway was activated without ligand stimulation, which was inhibited by EGFR TKI. In addition, although EGFR in the HEK293/D7F and HEK293/D-Tr cells lacked significant tyrosine residues for EGFR signal transduction, phosphorylation of Src homology and collagen homology (Shc) was spontaneously activated in these cells. Our results indicate that tyrosine residues in the C-terminal region of EGFR are not required for cellular sensitivity to EGFR TKI, and that an as-yet-unknown signaling pathway of EGFR may exist that is independent of the C-terminal region of EGFR.

Mechanisms of drug combinations: interaction and network perspectives

Understanding the molecular mechanisms underlying synergistic, potentiative and antagonistic effects of drug combinations could facilitate the discovery of novel efficacious combinations and multi-targeted agents. In this article, we describe an extensive investigation of the published literature on drug combinations for which the combination effect has been evaluated by rigorous analysis methods and for which relevant molecular interaction profiles of the drugs involved are available. Analysis of the 117 drug combinations identified reveals general and specific modes of action, and highlights the potential value of molecular interaction profiles in the discovery of novel multicomponent therapies.

Inhibition of Src tyrosine kinase reverts chemoresistance toward 5-fluorouracil in human pancreatic carcinoma cells: an involvement of epidermal growth factor receptor signaling

Resistance to chemotherapy is believed to be a major cause of treatment failure in pancreatic cancer. Thus, it is necessary to explore alternative therapeutic modalities to overcome drug resistance in pancreatic cancer treatment. We tested the hypothesis that Src tyrosine kinase inhibition could augment the chemosensitivity of 5-fluorouracil (5-FU)-resistant human pancreatic cancer cells to 5-FU. As detected by MTT proliferation assay, propidium iodide and annexin V staining, a combination of 5-FU+Src kinase inhibitor PP2 (4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine) reflected the chemotherapeutic sensitivity and restored the 5-FU-induced apoptosis in 5-FU-resistant cells. Furthermore, when small-interfering RNA approach to silence Src gene expression was applied, the degree of 5-FU-induced apoptosis was increased in all cell lines independently of the chemoresistance status. Western blotting and RT-PCR analysis revealed that the expression of thymidylate synthase (TS) was higher in 5-FU-resistant cells, however, decreased significantly after pretreatment with PP2. Furthermore, the combination of 5-FU+PP2 decreased the 5-FU-induced activation of epidermal growth factor receptor (EGFR)-AKT pathway. Finally, PP2 in combination with 5-FU substantially decreased the in vivo tumor growth and inhibited distant metastases. Taken together, 5-FU chemoresistance can be reversed through indirect TS regulation by inhibiting Src tyrosine kinase. A potential mechanism of action of Src kinase inhibitors on 5-FU chemosensitivity might be linked to the inhibition of 5-FU-induced EGFR-AKT activation.

N-Glycan fucosylation of epidermal growth factor receptor modulates receptor activity and sensitivity to epidermal growth factor receptor tyrosine kinase inhibitor

The glycosylation of cell surface proteins is important for cancer biology processes such as cellular proliferation or metastasis. alpha1,6-Fucosyltransferase (FUT8) transfers a fucose residue to n-linked oligosaccharides on glycoproteins. Herein, we study the effect of fucosylation on epidermal growth factor receptor (EGFR) activity and sensitivity to an EGFR-specific tyrosine kinase inhibitor (EGFR-TKI). The increased fucosylation of EGFR significantly promoted EGF-mediated cellular growth, and the decreased fucosylation by stable FUT8 knockdown weakened the growth response in HEK293 cells. The overexpression of FUT8 cells were more sensitive than the control cells to the EGFR-TKI gefitinib, and FUT8 knockdown decreased the sensitivity to gefitinib. Finally, to examine the effects in a human cancer cell line, we constructed stable FUT8 knockdown A549 cells, and found that these cells also decreased EGF-mediated cellular growth and were less sensitive than the control cells to gefitinib. In conclusion, we demonstrated that the modification of EGFR fucosylation affected EGF-mediated cellular growth and sensitivity to gefitinib. Our results provide a novel insight into how the glycosylation status of a receptor may affect the sensitivity of the cell to molecular target agents.

A phase II randomized multicenter trial of gefitinib plus FOLFIRI and FOLFIRI alone in patients with metastatic colorectal cancer

BACKGROUND

Gefitinib inhibits the epidermal growth factor receptor tyrosine kinase and preclinical studies indicate that it may enhance CPT-11 cytotoxicity. This randomized phase II trial investigates the feasibility and efficacy of gefitinib and 5-fluorouracil, folinic acid, irinotecan (FOLFIRI) in patients with metastatic colorectal cancer.

PATIENTS AND METHODS

Patients were randomized to FOLFIRI +/- gefitinib 250 mg daily p.o. Patients randomized to FOLFIRI + gefitinib without disease progression after 6 months continued to receive gefitinib alone until disease progression.

RESULTS

From October 2002 to September 2004, 100 patients were enrolled. Twenty-three patients (47.9%) in the FOLFIRI arm and 23 (45.1%) in the FOLFIRI + gefitinib arm experienced an objective response. The median progression-free survival and overall survival were 8.3 and 18.6 months in the FOLFIRI arm, and 8.3 and 17.1 months in the FOLFIRI + gefitinib arm, respectively. In the combination arm, grades 3-4 adverse events were experienced by 35 (67.3%) patients versus 25 patients (52.1%) in the FOLFIRI arm; 12 patients (23.1%) withdrew for an adverse event in the FOLFIRI + gefitinib arm and 5 (10.4%) in the FOLFIRI arm.

CONCLUSIONS

These data show that adding gefitinib to FOLFIRI does not improve the efficacy of FOLFIRI regimen. These disappointing results could be related to the high toxicity observed that led to significant dose reductions and delays.

Synergistic antitumor effect of S-1 and the epidermal growth factor receptor inhibitor gefitinib in non-small cell lung cancer cell lines: role of gefitinib-induced down-regulation of thymidylate synthase

Somatic mutations in the epidermal growth factor receptor (EGFR) gene are associated with the therapeutic response to EGFR tyrosine kinase inhibitors (TKI) in patients with advanced non-small cell lung cancer (NSCLC). The response rate to these drugs remains low, however, in NSCLC patients with wild-type EGFR alleles. Combination therapies with EGFR-TKIs and cytotoxic agents are considered a therapeutic option for patients with NSCLC expressing wild-type EGFR. We investigated the antiproliferative effect of the combination of the oral fluorouracil S-1 and the EGFR-TKI gefitinib in NSCLC cells of differing EGFR status. The combination of 5-fluorouracil and gefitinib showed a synergistic antiproliferative effect in vitro in all NSCLC cell lines tested. Combination chemotherapy with S-1 and gefitinib in vivo also had a synergistic antitumor effect on NSCLC xenografts regardless of the absence or presence of EGFR mutations. Gefitinib inhibited the expression of the transcription factor E2F-1, resulting in the down-regulation of thymidylate synthase at the mRNA and protein levels. These observations suggest that gefitinib-induced down-regulation of thymidylate synthase is responsible, at least in part, for the synergistic antitumor effect of combined treatment with S-1 and gefitinib and provide a basis for clinical evaluation of combination chemotherapy with S-1 and EGFR-TKIs in patients with solid tumors.

The use of xenograft models for the selection of cancer treatments with the EGFR as an example

Mouse models of cancer have consistently been used to qualify new anti-cancer drugs for development of human clinical trials. The most used models are xenografts of human tumors grown subcutaneously in immunodeficient mice such as athymic (nude) or severe combined immune deficient (SCID) mice. However, the number of anti-cancer agents that fail in the clinic far outweighs those considered effective, suggesting that the selection procedure for progression of molecules into the clinic requires improvement. This has provoked considerable skepticism about the value of using such preclinical models. As a result, a shift has occurred towards developing and using spontaneous mouse tumor arising in transgenic and/or knockout mice engineered to recapitulate various genetic alterations thought to be causative of specific types of human cancers. Alternatively, the option has been to improve human tumor xenograft models by using orthotopic transplantation and, therefore, promotion of metastatic spread of the resultant 'primary' tumors. Here we review the value and the limitations of xenograft models and their role in developing new anti-cancer treatments.