Transfection of anti-sense complementary DNA of human epidermal-growth-factor receptor attenuates the proliferation of human non-small-cell-lung-cancer cells

ErbB receptor-driven prolactinomas respond to targeted lapatinib treatment in female transgenic mice

As ErbB receptors are expressed in prolactinomas and exhibit downstream effects on prolactin (PRL) production and cell proliferation, we generated transgenic mice using a PRL enhancer/promoter expression system to restrict lactotroph-specific expression of human epidermal growth factor receptor (EGFR) or human EGFR2 (HER2). EGFR or HER2 transgenic mice developed prolactinomas between 13 and 15 months, and confocal immunofluorescence and Western blot analysis confirmed lactotroph-restricted PRL and EGFR or HER2 coexpression. Circulating PRL levels in EGFR and HER2 transgenic mice were increased 5- and 3.8-fold, respectively. Inhibiting EGFR or HER2 signaling with oral lapatinib (100 mg/kg), a dual tyrosine kinase inhibitor for both EGFR and HER2, suppressed circulating PRL by 72% and attenuated tumor PRL expression by 80% and also attenuated downstream tumor EGFR/HER2 signaling. This model demonstrates the role of ErbB receptors underlying prolactinoma tumorigenesis and the feasibility of targeting these receptors for translation to treatment of refractory prolactinomas.

Tamoxifen resistance in breast cancer cells is accompanied by an enhanced motile and invasive phenotype: inhibition by gefitinib ('Iressa', ZD1839)

Despite an initial response to antihormonal therapies, the development of resistance will occur in a significant number of breast cancer patients. The mechanisms that underlie acquired resistance are not yet clear. Using a previously established in vitro cell model of tamoxifen resistance in MCF7 cells, shown to display autocrine epidermal growth factor receptor (EGFR) signalling, we assessed how resistance might modulate their metastatic phenotype in vitro, as metastatic disease is the single most important factor affecting the mortality of cancer patients. Furthermore, we investigated the effect of the EGFR tyrosine kinase inhibitor (EGFR-TKI), gefitinib ('Iressa', ZD1839; AstraZeneca), on this behaviour. The acquisition of tamoxifen resistance in MCF7 cells was accompanied by a dramatic and significant increase in their invasive and motile nature. The affinity of these cells for matrix components was also enhanced. Inhibition of EGFR signalling with gefitinib reduced both basal and TGF-alpha-stimulated invasion and motility and reduced cell-matrix adhesion. In conclusion, we demonstrate here that resistance to tamoxifen in breast cancer cells is accompanied by a significant increase in their basal motile and invasive activity, properties associated with increased metastatic potential. Inhibition of EGFR signalling by gefitinib significantly inhibited cell motility and invasion thus suggesting a role for the EGF receptor in the aggressive phenotype of tamoxifen-resistant breast cancer cells.

Epidermal growth factor receptor as a target to improve treatment of lung cancer

Despite considerable efforts to reduce tobacco use, lung cancer remains the most common cancer in both men and women. Recent advances in radiation therapy and chemotherapy for lung cancer have yielded encouraging results, but survival in patients with locally advanced non-small-cell lung cancer (NSCLC) remains poor. As more and more molecular changes and their importance in malignant tissues continue to be characterized, approaches to target those aberrant pathways are being actively explored. The epidermal growth factor receptor (EGFR) is commonly overexpressed in NSCLC, particularly squamous cell carcinoma, and has been implicated in the development and progression of this disease, although a clear correlation with prognosis has not been established. Several different strategies have been developed to target and block the EGFR and its downstream effects, and some of them have been intensively studied in preclinical and clinical studies as a single-agent approach or in combination with radiation therapy or chemotherapy. In this article, we review the role of EGFR in lung cancer, as well as preclinical and clinical data on strategies to interfere with EGFR signaling alone or in combination with chemotherapy, radiation, or both.

Potential clinical application of antioncogene ribozymes for human lung cancer

Non-small-cell lung cancer frequently contains oncogenetic defects (mutations in ras, retinoblastoma, and p53 genes) that contribute to disease pathophysiology. Recent studies and clinical trials have focused on gene therapy approaches that either replace the function of defective tumor-suppressor genes such as p53 or inactivate mutant oncogenes such as ras. Ribozymes are RNA molecules with highly specific intrinsic enzymatic activity against target RNA sequences, which can discriminate mutant sequences that differ by a single base from their wild-type counterparts. Following binding to the RNA substrate by base-pair complementation, the ribozyme cleaves the target RNA irreversibly, then releases itself for new rounds of subsequent cleavage, resulting in significantly improved target:effector stoichiometry as compared with antisense oligonucleotides of the same specificity. Transcript-specific ribozymes have been used extensively for experimental oncogene inactivation. Ribozymes are effective for targeting mutant ras, p53, or the multidrug-resistant gene product for lung cancer cells in vitro. However, their in vivo effect is not well defined against this malignancy. We recently characterized the antitumor properties of an anti-K-ras ribozyme specific for the K-ras codon 12 mutation (GGT-->GTT). When delivered as a transgene by an adenoviral vector (ADV), the K-ras ribozyme (KRbz) suppressed growth of lung tumor xenografts expressing the relevant mutation, whereas the corresponding antisense sequence lacking catalytic activity did not. Multiple intratumoral (3-5) injections of KRbz-ADV were effective in producing complete tumor regressions of preexisting tumor xenografts. Clinical trials are under consideration to examine the applicability of this anti-K-ras ribozyme for treatment of non-small-cell lung cancers expressing the relevant mutation.

Inhibition of MMP-1 expression by antisense RNA decreases invasiveness of human chondrosarcoma

We previously reported that an elevated level of matrix metalloproteinase-1 (MMP-1) gene expression in patients with chondrosarcoma has a strong statistical correlation with recurrence and in vitro invasion. In the present study, we used an antisense RNA strategy for MMP-1 inhibition to determine if this would affect the invasive characteristics of the cells. We transfected a human chondrosarcoma cell line with a retroviral plasmid expressing a 770 bp genomic fragment of the human MMP-1 gene in the sense or antisense orientation. The results show that cells transfected with the MMP-1 antisense fragment had a significant decrease in both MMP-1 protein and enzyme activity (p<0.05) as compared to cells transfected with an empty plasmid or the parental cells. Cells transfected with the MMP-1 antisense fragment demonstrated a significant decrease in their ability to invade the collagen I barrier (p<0.05). The gene expression for MMP-8 and MMP-13 were unaffected in cells transfected with the MMP-1 antisense fragment, MMP-1 sense fragment, or empty plasmid. These results support the hypothesis that MMP-1 facilitates tumor cell egress from chondrosarcoma tissue and demonstrate the potential of MMP-1 as a promising target for a novel biologic therapy in chondrosarcoma.

Gene therapy of lung cancer

It is estimated that there will be 157,200 deaths from lung cancer in 2003. Current regimens of surgery, chemotherapy and radiation have not significantly changed overall 5-year survival rates for this disease. Thanks to intensive molecular studies over the last three decades, new targets for treatment have been identified, including replacement of tumor suppressor genes, prevention of angiogenesis and tumor growth, and regulation of programmed cell death. Promising advances have been made but obstacles still abound before effective use of these strategies at the patient bedside can occur. One area of concentration lies in developing more accurate and complete delivery of the therapeutic constructs. In the evolution of gene therapy approaches, from beginning theory to translational research, investigators in thoracic malignancies have played a leading role, utilizing a number of methods and delivery vehicles. The objective of this review is to discuss some of the major molecular targets available for manipulation in lung cancer, describe vectors and techniques currently used by thoracic researchers to deliver therapy, and provide the p53 model as an example of progression from bench research to clinical treatment.

Activation of Stat3 by receptor tyrosine kinases and cytokines regulates survival in human non-small cell carcinoma cells

Overexpression of receptor tyrosine kinases including the epidermal growth factor receptor (EGF-R) as well as nonreceptor tyrosine kinases, such as Src, have been implicated in the formation of human lung cancers. In addition, cytokines like interleukin-6 (IL-6) have been demonstrated to modulate lung cancer cell growth and elevated levels of IL-6 have been shown to be an adverse prognostic factor for patients with lung cancer. Despite a large body of evidence pointing to their potential importance, few direct studies into the role of signal transducers and activators of transcription (STAT) pathways in human lung cancer have been undertaken. Here we demonstrate that multiple nonsmall cell lung cancer cell lines demonstrate constitutive Stat3 DNA-binding activity. Stat3 DNA-binding activity is specifically upregulated by the addition of epidermal growth factor (EGF), IL-6, and hepatocyte-derived growth factor (HGF). Furthermore, the stimulation of Stat3 DNA-binding activity by EGF requires the activity of EGF-R tyrosine kinase as well as Src-kinase, while the upregulation of Stat3 activity by IL-6 or HGF requires only Src-kinase activity. Treatment of A549 lung cancer cells with PD180970 or SU6656, both pharmacological inhibitors of Src-kinase, resulted in reduced Src and Stat3 activity, cell cycle arrest in G2, and reduced viability of cells accompanied by induction of apoptosis. Treatment of Stat3-positive A549 and H358 cells with antisense Stat3 oligonucleotides results in complete loss of Stat3 DNA-binding activity and apoptosis, while Stat3-positive H1299 cells remained healthy. Finally, an adenoviral vector expressing a dominant-negative Stat3 isoform results in loss of Stat3 DNA-binding activity, apoptosis, and reduced cellular viability. These results demonstrate a role of Stat3 in transducing survival signals downstream of tyrosine kinases such as Src, EGF-R, and c-Met, as well as cytokines such as IL-6, in human nonsmall cell lung cancers.

Small interfering RNAs suppress the expression of endogenous and GFP-fused epidermal growth factor receptor (erbB1) and induce apoptosis in erbB1-overexpressing cells

Deregulated and excessive expression of epidermal growth factor receptor (EGFR or erbB1), a transmembrane receptor tyrosine kinase specific for the epidermal growth factor (EGF), is a feature and/or cause of a wide range of human cancers, and thus inhibition of its expression is potentially therapeutic. In RNA interference (RNAi), duplexes of 21-nucleotide RNAs (small interfering RNA, siRNA) corresponding to mRNA sequences of particular genes are used to efficiently inhibit the expression of the target proteins in mammalian cells. Here we show that by using RNAi the expression of endogenous erbB1 can be specifically and extensively (90%) suppressed in A431 human epidermoid carcinoma cells. As a consequence, EGF-induced tyrosine phosphorylation was inhibited and cell proliferation was reduced due to induction of apoptosis. We established an inverse correlation between the level of expressed erbB1 and EGF sensitivity on a cell-by-cell basis using flow cytometry. A431 cells expressing endogenous erbB1 were transfected with erbB1 fused C-terminally to enhanced green fluorescent protein (EGFP). Selective inhibition of the expression of the fusion protein was achieved with an siRNA specific for the EGFP mRNA, whereas the erbB1-specific siRNAs inhibited the expression of both molecules. siRNA-mediated inhibition of erbB1 and other erbB tyrosine kinases may constitute a useful therapeutic approach in the treatment of human cancer.

Ectopic expression of herpes simplex virus-thymidine kinase gene in human non-small cell lung cancer cells conferred caspase-activated apoptosis sensitized by ganciclovir

Human non-small cell lung cancer (NSCLC) cells were transfected with recombinant prodrug herpes simplex virus type I thymidine kinase (HSV-tk) cDNA, and the selected clones underwent apoptosis in response to induction by antiviral ganciclovir (GCV). The efficiency of GCV-induced growth inhibition and the extent of the bystander effect were associated with the expression level of HSV-TK in stable transfectants. Development in the HSV-tk/GCV system toward cell death was initiated with cell-cycle accumulation at S and G(2)/M phases, immediately followed by the appearance of sub-G(0)/G(1) cells after drug exposure. To investigate the regulation of cell-cycle modulators during drug treatment, we analyzed release of the apoptosis initiator cytochrome c and activation of the downstream effectors caspase-9, caspase-3 and poly(ADP-ribose)polymerase 16 hr after GCV sensitization, followed by transient escalation of tumor-suppressor p53 and cell-cycle modulators cyclin A and B(1) before committing to programmed cell death. Furthermore, tumor regression was proportional to the degree of ectopic expression of the transferred HSV-tk gene. Our results demonstrate that the HSV-tk/GCV system effectively inhibits the proliferation of NSCLC cells in vitro and in vivo through potent induction of apoptosis, thus providing a rationale for further development.

[Cytosolic pS2 levels in 154 non-small-cell lung carcinomas. Correlation with other clinical and biological parameters]

INTRODUCTION

pS2 was first identified as an estrogen induced molecule in a breast cancer cell line, but its gene responds to several growth factors and oncogenic proteins. Its main clinical application lies in breast carcinomas, where it is a molecular marker to identify breast cancer patients who will respond to hormone therapy. This study was performed to evaluate the significance of the pS2 cytosolic levels in non small cell lung carcinomas classified according to different clinical and biological parameters. Likewise, the results obtained were correlated with those observed in normal tissues.

MATERIAL AND METHODS

The study group included 154 non small cell lung carcinomas (59 adenocarcinomas and 95 squamous carcinomas) and 54 normal lung samples. Cathepsin D, pS2, neuron specific enolase (NSE) and CA125 cytosolic concentrations were determined, as well as those of epidermal growth factor receptor (EGFR), erbB2 protein, CD44s, CD44v5 and CD44v6 on cell surface membranes. Likewise, clinical stage, histological grade, ploidy and cellular S-phase fraction were also considered as variables of the study.

RESULTS

We observed cytosolic pS2 values greater than 1 ng/mg protein (positive cutoff) in 18/59 adenocarcinomas and in 10/95 squamous carcinomas (p:0.00177). In adenocarcinomas, pS2 positivity was not correlated with any clinical and biological parameters, but positive cases had lower EGFR (p:0.03770) concentrations and higher CA125 (p:0.01902) levels. In squamous carcinomas, pS2 positivity was associated with lower EGFR (p:0.02270) levels and higher erbB2 protein (p:0,00563) concentrations.

CONCLUSIONS

Our results led us to suggest the following: 1) cytosolic pS2 concentrations are higher in tumoral than in normal samples; 2) adenoarcinomas had higher levels than squamous lung carcinomas; 3) in adenocarcinomas, positivity for pS2 is associated with lower EGFR levels and higher CA125 concentrations suggesting a worse outcome, and 4) in squamous lung tumors, positivity for pS2 was associated with lower EGFR and higher erbB2 oncoprotein concentrations, it not being possible to establish its clinical significance, although it may be correlated with a poor prognosis.

Gene therapy for lung neoplasms

The field of gene therapy is still in its infancy, but significant accomplishments have been achieved. The ability to transfer genes safely and successfully into animals and patients clearly has been established. It is highly likely that in the near future, gene therapy will be shown to have clear therapeutic efficacy in diseases such as the treatment of hemophilia (using adeno-associated virus vectors) and the stimulation of angiogenesis in peripheral vascular disease and myocardial ischemia. Although only Phase 1 cancer gene therapy trials for thoracic malignancy have been conducted (usually in patients with large tumor burdens and at submaximal doses), there are some hints of efficacy at higher doses of vector in trials for localized malignancy. The studies reviewed in this article demonstrate the first attempts to use gene therapy vectors for lung cancer and mesothelioma. Although none of the diseases studied was "cured," valuable lessons have been learned from these trials, especially in defining the challenges of relatively inefficient and transient delivery of transgene in vivo. Using this knowledge, the second phase of gene therapy research has begun, with a strong focus on developing improved vector technology. Given the progress so far, there is little doubt that gene therapy will become a key approach for the treatment of thoracic malignancies in the near future.

Antisense oligonucleotides targeting the epidermal growth factor receptor inhibit proliferation, induce apoptosis, and cooperate with cytotoxic drugs in human cancer cell lines

We have constructed a series of 22 phosphorothioate 20-mer antisense oligonucleotides directed against different regions of the human (EGFR) mRNA. Treatment with EGFR antisense oligonucleotides showed a dose-dependent inhibition of human GEO colon cancer cell growth in soft agar. Western blot analysis demonstrated a significant reduction in EGFR expression after treatment with each EGFR antisense oligonucleotide. The ability to inhibit GEO anchorage-independent growth, however, varied among the EGFR antisense sequences with an IC(50) ranging between 0.5 and 3.5 microM. Two of these antisense oligonucleotides targeting the regions between 2457-2476 and 614-4633 bases of the human EGFR mRNA have been modified as hybrid DNA/RNA mixed backbone oligonucleotides (MBO) to examine their anticancer properties in vivo. The 2 EGFR antisense MBOs retained the same biological properties of the fully phosphorothioate EGFR antisense oligonucleotides targeting the same EGFR mRNA sequences, such as blocking EGFR synthesis, inhibiting cell growth and enhancing programmed cell death in human cancer cell lines that express functional EGFRs. Furthermore, a potentiation in the growth inhibitory effect on GEO cancer cells was observed after treatment with these EGFR antisense MBOs in combination with cytotoxic drugs, including cisplatin, doxorubicin, paclitaxel, or topotecan. These results show the antiproliferative activity of specific EGFR antisense oligonucleotides and allow to identify novel EGFR antisense MBOs that deserve further evaluation as potential selective anticancer agents alone or in combination with cytotoxic drugs in human carcinomas that express functional EGFRs.

Gene Therapy for Lung Cancer

Gene therapy is emerging as a promising modality for the treatment of lung cancer. Diverse strategies employing gene therapy for lung cancer have been investigated in vitro and in animal models, and a number of these approaches have met with promising results. Several phase I and II clinical trials have been undertaken, and early results suggest that it may be safe to administer gene therapy to lung cancer patients. It remains to be determined whether this modality will be efficacious as primary or adjunctive therapy in the setting of lung cancer.

Lectin enhancement of the lipofection efficiency in human lung carcinoma cells

Poor transfection efficiency of human lung carcinoma cells by lipofection begs further development of more efficient gene delivery strategies. The purpose of this study was to determine whether lectins can improve the lipofection efficiency in lung carcinoma cells. A549, Calu3, and H292 cells grown to 90% confluence were transfected for 18 h with a plasmid DNA containing a beta-galactosidase reporter gene (pCMVlacZ) using lipofectin plus a lectin as the vector. Ten different lectins, which exhibit a wide range of carbohydrate-binding specificities, were examined for their abilities to enhance the efficiency of lipofection. The transfected cells were assessed for transfection efficiency by beta-galactosidase activity (units/microg protein) and % blue cells following X-Gal stain. Lipofectin supplemented with Griffonia simplicifolia-I (GS-I) yields largest enhancement of the lipofection efficiency in A549 and Calu3 cells (5.3- and 28-fold, respectively). Maackia amurensis gives the largest enhancement (6.5-fold) of lipofection efficiency in H292 cells. The transfection efficiency correlates with the amounts of DNA delivered to the nucleus. Binding of FITC-labeled GS-I and the enhancement of the lipofection efficiency by GS-I were inhibited by alpha-methyl-D-galactopyranoside, indicating an alpha-galactoside-mediated gene transfer to lung carcinoma cells. We conclude that lectin-facilitated lipofection is an efficient gene delivery strategy. Employment of cell type-specific lectins may allow for efficient cell type-specific gene targeting.