Iressa induces cytostasis and augments Fas-mediated apoptosis in acinic cell adenocarcinoma overexpressing HER2/neu

The Role of ERBB2/HER2 Tyrosine Kinase Receptor in the Regulation of Cell Death

HER2 (Human Epidermal Growth Factor Receptor 2), also known as ERBB2, CD340, and Neu protooncogene, is a member of the epidermal growth factor receptor (EGRF) family. Members of the ERBB family, including HER2, activate molecular cascades that stimulate proliferation and migration of cancer cells, as well as their resistance to the anticancer therapy. These proteins are often overexpressed and/or mutated in various cancer types and represent promising targets for the anti-cancer therapy. Currently, anti-HER2 drugs have been approved for the treatment of several types of solid tumors. HER2-specific therapy includes monoclonal antibodies and low-molecular weight inhibitors of tyrosine kinase receptors, such as lapatinib, neratinib, and pyrotinib. In addition to the activation of molecular pathways responsible for cell proliferation and survival under stress conditions, HER2 directly regulates programmed cell death. Here, we review the studies focused on the involvement of HER2 in various signaling pathways and its role in the regulation of apoptosis.

Salivary acinic cell carcinoma: reappraisal and update

Epidemiologic and clinicopathologic features, therapeutic strategies, and prognosis for acinic cell carcinoma of the major and minor salivary glands are critically reviewed. We explore histopathologic, histochemical, electron microscopic and immunohistochemical aspects and discuss histologic grading, histogenesis, animal models, and genetic events. In the context of possible diagnostic difficulties, the relationship to mammary analog secretory carcinoma is probed and a classification is suggested. Areas of controversy or uncertainty, which may benefit from further investigations, are also highlighted.

Gefitinib induces apoptosis in human glioma cells by targeting Bad phosphorylation

Gefitinib, a selective epidermal growth factor receptor tyrosine kinase inhibitor, is under clinical testing and use in cancer patients, including glioma. However, the molecular mechanisms involved in gefitinib-mediated anticancer effects against glioma remain largely uncharacterized. Gefitinib inhibits cell growth and induces apoptosis in human glioma cells. Gefitinib also induces death of H4 cells with characteristics of the intrinsic apoptotic pathway, including Bax mitochondrial translocation, mitochondrial outer membrane permeabilization, cytochrome c cytosolic release, and caspase-9/caspase-3 activation. The importance of Bax in mediating gefitinib-induced apoptosis was confirmed by the attenuation of apoptosis by Bax siRNA and Bax channel blocker. Gefitinib caused Bad dephosphorylation, particularly in serine-112, and increased its binding preference to Bcl-2 and Bcl-xL. The dephosphorylation of Bad in gefitinib-treated cells was accompanied by reduced intracellular cyclic AMP content and protein kinase A (PKA) activity. Adenylyl cyclase activator forskolin attenuated, but PKA inhibitor H89 augmented, gefitinib-induced Bad dephosphorylation, Bax mitochondrial translocation, caspase-9/caspase-3 activation, and viability loss. Intriguingly, a nonselective protein phosphatase inhibitor okadaic acid alleviated gefitinib-induced alterations, except Bad dephosphorylation. In parallel with the higher basal PKA activity, response of U87 cells to gefitinib treatment was delayed and relatively resistant compared with that of H4 and T98G cells. Inactivation of PKA sensitized H4, T98G, and U87 cells to gefitinib cytotoxicity, Bad dephosphorylation in serine-112, and caspase-9/caspase-3 activation. Our findings suggest the involvement of the Bad/Bax signaling pathway in gefitinib-induced glioma apoptosis. Furthermore, the inactivation of PKA was shown to play a role in triggering the proapoptotic function of Bad.

Modeling and optimization of combined cytostatic and cytotoxic cancer chemotherapy

OBJECTIVES

This study extends a previous mathematical model of cancer cytotoxic chemotherapy, which considered cycling tumor cells and interactions with the immune system, by incorporating a different type of drug: a cytostatic agent. The effect of a cytostatic drug is to arrest cells in a phase of their cycle. In consequence, once tumor cells are arrested and synchronized they can be targeted with a cytotoxic agent, thus maximizing cell kill fraction and minimizing normal cell killing. The goal is to incorporate the new drug into the chemotherapy protocol and devise optimal delivery schedules.

METHODS

The problem of designing efficient combined chemotherapies is formulated as an optimal control problem and tackled using a state-of-the-art evolutionary algorithm for real-valued encoding, namely the covariance matrix adaptation evolution strategy. Alternative solution representations and three formulations of the underlying objective function are proposed and compared.

RESULTS

The optimization problem was successfully solved by the proposed approach. The encoding that enforced non-overlapping (simultaneous) application of the two types of drugs produced competitive protocols with significant less amount of toxic drug, thus achieving better immune system health. When compared to treatment protocols that only consider a cytotoxic agent, the incorporation of a cytostatic drug dramatically improved the outcome and performance of the overall treatment, confirming in silico that the combination of a cytostatic with a cytotoxic agent improves the efficacy and efficiency of the chemotherapy.

CONCLUSION

We conclude that the proposed approach can serve as a valuable decision support tool for the medical practitioner facing the complex problem of designing efficient combined chemotherapies.

Restoration of BRAK / CXCL14 gene expression by gefitinib is associated with antitumor efficacy of the drug in head and neck squamous cell carcinoma

Clinical efficacy of gefitinib (ZD1839, Iressa), which is an inhibitor specific for epidermal growth factor (EGF) receptor tyrosine kinase, has been shown in non-small-cell lung carcinoma patients with EGF receptor mutations, so these mutations are useful marker(s) to find a responder for the drug. Recent studies have shown that the EGF receptor gene mutation is rare in squamous cell carcinoma in the esophageal and head and neck regions. We previously reported that the expression of the chemokine BRAK/CXCL14 in head and neck squamous cell carcinoma (HNSCC) cells was down-regulated by EGF treatment, and that forced expression of BRAK in tumor cells decreased the tumorigenicity of the cells in xenografts. Thus, we investigated the relationship between restoration of BRAK expression by gefitinib and the efficacy of the drug for tumor suppression. We found that EGF down-regulated BRAK expression through the MEK-extracellular signal regulated kinase pathway and that this down-regulated expression was restored by gefitinib in vitro. Oral administration of gefitinib significantly (P < 0.001) reduced tumor growth of xenografts of three HNSCC cell lines (HSC-2, HSC-3, and HSC-4), in female athymic nude mice, accompanied by an increase in BRAK expression specifically in tumor tissue. This tumor-suppressing effect of the drug was not observed in the case of BRAK non-expressing cells. Furthermore introduction of BRAK shRNA vector reduced both the expression levels of BRAK in HSC-3 cells and the antitumor efficacy of gefitinib in vivo. Our data showing an inverse relationship between BRAK expression levels in tumor cells and the tumor growth rate indicate that the gefitinib-induced increase in BRAK expression is beneficial for tumor suppression in vivo.

Current concepts in research related to oncogenes implicated in salivary gland tumourigenesis: a review of the literature

BACKGROUND

Salivary gland tumours are relatively uncommon and there exists considerable difficulty in decisions regarding prognosis and management, as well as diagnostic uncertainty that has implications for treatment.

METHOD

Literature pertaining to individual oncogenes has been reviewed and commented upon, specifically looking at the role of these as diagnostic and prognostic markers and as potential targets for treatments.

RESULTS

kit, PLAG1, Mect1-Maml2, HMGIC, HER2/neu, ras, c-fos and Sox-4 all have seminal small-scale studies in the literature with potential for further research and eventual clinical applications.

CONCLUSION

A wide variety of oncogenes are implicated in salivary gland tumourigenesis, with evidence being confined to small murine or in vitro studies more often than not. There are possible roles for different oncogenes in therapeutics, prognosis and management of specific salivary gland tumours.

Immunohistochemical expression of the oncogenic molecules active Stat3 and survivin in benign and malignant salivary gland tumors

OBJECTIVE

Signal transducer and activator of transcription 3 (Stat3) and survivin have been shown to exert oncogenic effects in various human neoplasms. The purpose of this study was to evaluate the expression of tyrosine phosphorylated (active) Stat3 and survivin in various benign and malignant salivary gland tumors (SGTs).

STUDY DESIGN

Eighty-six SGTs (65 malignant and 21 benign tumors of various histopathologic subtypes) were immunohistochemically stained with antisurvivin or anti-phosphorylated tyrosine-705 (p-tyr) Stat3 antibodies. Immunohistochemical reactivity was graded in a semiquantitative manner; a combined score of immunohistochemical positivity (0-6) was calculated for each tumor by adding the individual scores for percentage of tumor cells (0-3) and intensity of staining (0-3).

RESULTS

Survivin was immunohistochemically detected in all studied benign and malignant SGTs; p-tyr Stat3 was also detected in the majority (91%) of SGTs. The average combined scores for survivin and p-tyr Stat3 immunohistochemical expression in the studied malignant SGTs was 4.40 and 3.35, respectively; the corresponding combined scores for survivin and p-tyr Stat3 in the studied benign SGTs were 4.37 and 3.22, respectively. No statistically significant differences (P > .05) in p-tyr Stat3 or survivin expression were detected between the benign and malignant groups, or among the various examined histopathologic subtypes of SGTs. In contrast, normal salivary gland tissues revealed only weak and focal survivin or p-tyr Stat3 immunoreactivity, mainly localized to ductal and mucous cells.

CONCLUSIONS

Our data indicate an almost universal expression of activated Stat3 and survivin in benign and malignant SGTs. Considering the well established proliferative and antiapoptotic properties of these molecules and their functional interrelationship, selective targeting techniques against Stat3 and/or survivin may represent promising therapeutic strategies against neoplasms of salivary gland origin.

Trichostatin A sensitizes human ovarian cancer cells to TRAIL-induced apoptosis by down-regulation of c-FLIPL via inhibition of EGFR pathway

TRAIL-resistant cancer cells can be sensitized to TRAIL by combination therapy. In this study, we investigated the effect of trichostatin A (TSA), a histone deacetylase inhibitor, to overcome the TRAIL resistance in human ovarian cancer cells. Co-treatment of human ovarian cancer cells with TSA and TRAIL synergistically inhibited cell proliferation and induced apoptosis. The combined treatment of ovarian cancer SKOV3 cells with TSA and TRAIL significantly activated caspase-8 and truncated Bid, resulting in the cytosolic accumulation of cytochrome c as well as the activation of caspase-9 and -3. Moreover, we found that down-regulation of c-FLIP(L) might contribute to TSA-mediated sensitization to TRAIL-induced apoptosis in SKOV3 cells, and this result was supported by showing that down- or up-regulation of c-FLIP(L) with transfection of siRNA or plasmid sensitized or made SKOV3 cells resistant to TRAIL-induced apoptosis, respectively. TSA or co-treatment with TSA alone and TRAIL also resulted in down-regulation of EGFR1/2 and dephosphorylation of its downstream targets, AKT and ERK. Treatment of SKOV3 cells with PKI-166 (EGFR1/2 inhibitor), LY294002 (AKT inhibitor), and PD98059 (ERK inhibitor) decreased c-FLIP(L) expression and co-treatment with TRAIL further reduced the level of c-FLIP(L,) respectively, as did TSA. Collectively, our data suggest that TSA-mediated sensitization of ovarian cancer cells to TRAIL is closely correlated with down-regulation of c-FLIP(L) via inhibition of EGFR pathway, involving caspase-dependent mitochondrial apoptosis, and combination of TSA and TRAIL may be an effective strategy for treating TRAIL-resistant human ovarian cancer cells.

New agents in the treatment for malignancies of the salivary and thyroid glands

The treatment of relatively rare malignancies, such as those of the salivary glands and iodine refractory thyroid cancer, has been invigorated by the development of novel molecular targeting agents. Accrual to clinical trials for these disease sites continues to be limited by their relatively low incidence. Nonetheless, multicenter collaborations have contributed greatly to the development of a number of emerging systemic therapies. This article briefly summarizes the epidemiology and pathogenesis of salivary gland and thyroid cancer, and then describes some of the new drugs under evaluation for these malignancies.

An epidermal growth factor inhibitor, Gefitinib, induces apoptosis through a p53-dependent upregulation of pro-apoptotic molecules and downregulation of anti-apoptotic molecules in human lung adenocarcinoma A549 cells

A selective epidermal growth factor receptor inhibitor, Gefitinib, has been clinically demonstrated to be effective for certain cancer cell types including lung cancer. Our previous study indicated that Gefitinib induced Fas/caspase-dependent apoptosis in human lung adenocarcinoma A549 cells. However, the pathway relaying the signals of Gefitinib-induced cell death has not been fully elucidated. Loss of normal function of p53 facilitates the development of neoplastic lesions and possibly contributes to the development of resistance to chemotherapy. Thus, the current study was designed to examine the role of p53 in Gefitinib-induced apoptosis. Incubation of human lung adenocarcinoma A549 cells with 25 microM Gefitinib resulted in phosphorylation and activation of p53 such as enhanced DNA binding activity, which was accompanied by the upregulation of PUMA (p53 upregulated modulator of apoptosis) and Fas, and downregulation of survivin and XIAP (X-linked inhibitor of apoptosis protein). The Gefitinib-mediated Fas, PUMA, survivin, XIAP regulation and subsequent apoptosis were significantly inhibited in stable p53-shRNA transfectants. Similarly, H1299/p53 cells were more sensitive to Gefitinib compared to H1299 cells in clonogenic survival assay. This event was accompanied by p53 phosphorylation, as well as Fas, PUMA, survivin, and XIAP modulation. Collectively, the results support an important role of p53 in Gefitinib-induced apoptosis in human lung cancer cells. p53 may induce apoptosis through the regulation of apoptotic (Fas and PUMA) and anti-apoptotic (XIAP and survivin) genes. Our studies not only pave a way to the understanding of pharmacological mechanisms of Gefitinib, but also implicate for the necessity to prescreen p53 expression level before clinical application of Gefitinib in human cancer therapy.

The epidermal growth factor receptor family: biology driving targeted therapeutics

The epidermal growth factor family of receptor tyrosine kinases (ErbBs) plays essential roles in regulating cell proliferation, survival, differentiation and migration. The ErbB receptors carry out both redundant and restricted functions in mammalian development and in the maintenance of tissues in the adult mammal. Loss of regulation of the ErbB receptors underlies many human diseases, most notably cancer. Our understanding of the function and complex regulation of these receptors has fueled the development of targeted therapeutic agents for human malignancies in the last 15 years. Here we review the biology of ErbB receptors, including their structure, signaling, regulation, and roles in development and disease, then briefly touch on their increasing roles as targets for cancer therapy.

A stable explant culture of HER2/neu invasive carcinoma supported by alpha-Smooth Muscle Actin expressing stromal cells to evaluate therapeutic agents

Background

To gain a better understanding of the effects of therapeutic agents on the tumor microenvironment in invasive cancers, we developed a co-culture model from an invasive lobular carcinoma. Tumor cells expressing HER2/neu organize in nests surrounded by alpha-Smooth Muscle Actin (α-SMA) expressing tumor stroma to resemble the morphology of an invading tumor. This co-culture, Mammary Adenocarcinoma Model (MAM-1) maintains a 1:1 ratio of HER2/neu positive tumor cells to α-SMA-reactive stromal cells and renews this configuration for over 20 passages in vitro.

Methods

We characterized the cellular elements of the MAM-1 model by microarray analysis, and immunocytochemistry. We developed flow cytometric assays to evaluate the relative responses of the tumor and stroma to the tyrosine kinase inhibitor, Iressa.

Results

The MAM-1 gene expression profile contains clusters that represent the ErbB-2 breast cancer signature and stroma-specific clusters associated with invasive breast cancers. The stability of this model and the ability to antigenically label the tumor and stromal fractions allowed us to determine the specificity of Iressa, a receptor tyrosine kinase inhibitor, for targeting the tumor cell population. Treatment resulted in a selective dose-dependent reduction in phospho-pMEK1/2 and pp44/42MAPK in tumor cells. Within 24 h the tumor cell fraction was reduced 1.9-fold while the stromal cell fraction increased >3-fold, consistent with specific reductions in phospho-pp44/42 MAPK, MEK1/2 and PCNA in tumor cells and reciprocal increases in the stromal cells. Erosion of the tumor cell nests and augmented growth of the stromal cells resembled a fibrotic response.

Conclusion

This model demonstrates the specificity of Iressa for HER2/neu expressing tumor cells versus the tumor associated myofibroblasts and is appropriate for delineating effects of therapy on signal transduction in the breast tumor microenvironment and improving strategies that can dually or differentially target the tumor and stromal elements in the microenvironment.

Epidermal growth factor receptor inhibitors enhance susceptibility to Fas-mediated apoptosis in oral squamous cell carcinoma cells

Molecular inhibition of epidermal growth factor receptor (EGFR) signaling is a promising cancer treatment strategy. We examined whether inhibition of EGFR signaling would affect the susceptibility of oral squamous cell carcinoma (OSCC) cells to Fas-mediated apoptosis. Treatment of OSCC cells with an anti-EGFR monoclonal antibody, C225, and an EGFR tyrosine kinase inhibitor, AG1478, which target the extracellular and intracellular domains of the receptor, respectively, inhibited phosphorylation of EGFR and its downstream effector molecule Akt and amplified the induction of Fas-mediated apoptosis. In OSCC cells treated with EGFR inhibitors, Fas-mediated apoptosis was accompanied by caspase-8 activation but not Bid cleavage. Caspase-3 and -8 inhibitors reduced the effect of EGFR inhibitors on Fas-mediated apoptosis in OSCC cells, but a caspase-9 inhibitor did not. These results indicate that the pro-apoptotic activity of EGFR inhibitors in OSCC cells depends on the extrinsic pathway of the caspase cascade. Although EGFR inhibitors did not affect the expression of Fas, the Fas-associated death domain protein, or procaspase-8 in OSCC cells, the inhibition downregulated cellular FLICE-inhibitory protein (c-FLIP). Moreover, knockdown of c-FLIP in HSC-2 cells with a small interfering RNA strongly enhanced Fas-mediated apoptosis. These results suggest that the EGFR signaling pathway may, in part, regulate Fas-mediated apoptosis in OSCC cells through c-FLIP expression.

Gefitinib prevents cancer progression in mice expressing the activated rat HER2/neu

We tested the efficacy of gefitinib in the prevention of HER2/neu-mediated breast cancer development in BALB-NeuT transgenic mice. Oral administration of gefitinib to female transgenic mice from 5 to 14 weeks of age reduced tumor multiplicity from 9.6 +/- 0.82 to 0.58 +/- 1.1 (83%). We observed a decrease in the number and size of lobules and lobular nodules in treated mice with a reduction in the overall disease burden per gland. Normal duct development in the mammary glands was not affected by gefitinib. The development of acinic cell carcinoma in the parotid glands of these animals was also reduced coincident with decreased stromal involvement during progression. Gefitinib eliminated phosphorylation of HER2 and HER3 and signaling through MAPK and Akt in lobular hyperplasias and carcinomas. At the same time MAPK activity and cytokine production in splenocytes and lymph nodes was increased in gefitinib-treated animals coincident with an increase in lymph node size. Delaying gefitinib treatment until mammary glands exhibited atypical lobular hyperplasias reduced efficacy. These studies demonstrate the critical role of HER2 signal transduction in the onset and progression of HER2/neu-dependent breast cancer and suggest a role for specific inhibitors to prevent the outgrowth of early hyperplastic disease.

Juxtacrine activation of epidermal growth factor (EGF) receptor by membrane-anchored heparin-binding EGF-like growth factor protects epithelial cells from anoikis while maintaining an epithelial phenotype

Loss of cell-matrix adhesion is often associated with acute epithelial injury, suggesting that "anoikis" may be an important contributor to cell death. Resistance against anoikis is a key characteristic of transformed cells. When nontransformed epithelia are injured, activation of the epidermal growth factor (EGF) receptor (EGFR) by paracrine/autocrine release of soluble ligands can induce a prosurvival program, but there is generally evidence for concomitant dedifferentiation. The EGFR ligand, heparin-binding EGF-like growth factor (HB-EGF), is synthesized as a membrane-anchored precursor that can activate the EGFR via juxtacrine signaling or can be released and act as a soluble growth factor. In Madin-Darby canine kidney cells, expression of membrane-anchored HB-EGF increases cell-cell and cell-matrix adhesion. Therefore, these studies were designed to test the effects of juxtacrine HB-EGF signaling upon cell survival and epithelial integrity when cells are denied proper cell-matrix interactions. Cells expressing a noncleavable mutated form of membrane-anchored HB-EGF demonstrated increased survival from anoikis, formed larger cell aggregates, and maintained epithelial characteristics even following prolonged detachment from the substratum. Physical association between membrane-anchored HB-EGF and EGFR was observed. Signaling studies indicated synergistic effects of EGFR activation and phosphatidylinositol 3-kinase signaling to regulate apoptotic and survival pathways. In contrast, although administration of exogenous EGF partially suppressed anoikis in wild type cells, it also led to an increased expression of mesenchymal markers, suggesting dedifferentiation. Taken together, we propose a novel role for membrane-anchored HB-EGF in the cytoprotection of epithelial cells.

Breast cancer expressing the activated HER2/neu is sensitive to gefitinib in vitro and in vivo and acquires resistance through a novel point mutation in the HER2/neu

The HER2/neu oncogene is an important diagnostic and prognostic factor and therapeutic target in breast and other cancers. We developed and characterized a breast cancer cell line (Bam1a) that overexpresses the activated HER2/neu and ErbB-3 and has a gene expression profile consistent with the ErbB-2 genetic signature. We evaluated the effects of the epidermal growth factor receptor (EGFR)/HER2 inhibitor, gefitinib, on this breast tumor line in vitro and in vivo. We characterized the effects of gefitinib on EGFR, HER2, and ErbB-3 phosphorylation by Western blot and determined the effects on downstream signaling through growth, survival, and stress pathways and the effect on proliferation, cell cycle, and apoptosis. Gefitinib treatment diminished phosphorylation of the ErbB-3 > EGFR > HER2/neu and signal transducers and activators of transcriptions in a dose-dependent fashion. Downstream mitogenic signaling through mitogen-activated protein (MAP)/extracellular signal regulated kinase kinase, p44/42 MAP kinase (MAPK) and stress signaling through c-Jun-NH(2)-kinase (JNK) 1 and c-Jun was impaired (1 micromol/L, 4-24 h), leading to cytostasis and cell cycle arrest within 24 h by decreased cyclin D1, cyclin B1, and p(Ser795)Rb and increased p27. Proliferation and colony formation were inhibited at 0.5 and 1 micromol/L, respectively, and correlated with altered gene expression profiles. Diminished survival signaling through Akt, induction of bim, loss of connexin43, and decreased production of vascular endothelial growth factor-D preceded caspase-3 and poly(ADP)ribose polymerase (PARP) cleavage and apoptosis (>50% 2 micromol/L, 48 h). Oral administration of gefitinib was able to prevent the outgrowth of Bam1a tumor cells from palpable lesions, shrink established tumors, eliminate HER2 and HER3 phosphorylation, and decrease MAPK and Akt signaling in vivo. A variant of the Bam1a cell line, IR-5, with acquired ability to grow in 5 micromol/L gefitinib was developed and characterized. IR-5 bears a novel point mutation in the HER2/neu that corresponds to a L726I in the ATP-binding pocket and correlates with a log decrease in sensitivity to gefitinib, increased heterodimerization with EGFR and HER3, and impaired down-regulation. Gene expression profiling of IR-5 showed increased expression of EMP-1, NOTCH-1, FLT-1, PDGFB, and several other genes that may contribute to the resistant phenotype and sustain signaling through MAPK and Akt. This model will be useful in understanding the differences between intrinsic drug sensitivity and acquired resistance in the context of therapeutic strategies that target oncogene addicted diseases.

BH3 mimetic ABT-737 neutralizes resistance to FLT3 inhibitor treatment mediated by FLT3-independent expression of BCL2 in primary AML blasts

FLT3 defines a promising target for the treatment of acute myeloid leukemia (AML). In contrast to their efficacy in cell lines, FLT3-specific inhibitors as single agents have only modest clinical activity in patients with AML. As demonstrated here, overexpression of anti-apoptotic proteins of the BCL2 family leads to resistance against FLT3 inhibitors in a hematopoietic cell line model with activating FLT3 mutations. The susceptibility to FLT3 inhibition could be restored by treatment with the novel BH3 mimetic ABT-737. Primary AML samples tested in our study showed a high expression of BCL2 protein, but not of BCL-xL or MCL1. BCL2 protein levels were not reduced after dephosphorylation of FLT3 and its downstream target STAT5 in patient samples with FLT3 internal tandem duplications. Interestingly, treatment with ABT-737 caused apoptotic cell death in all primary AML samples at submicromolar level and synergized efficiently with FLT3 inhibition in AML samples with activating FLT3 mutations. In contrast to AML cell lines, BCR-ABL transformed human cells showed resistance to ABT-737, which might be due to the induction of MCL1 by BCR-ABL. Inhibition of BCL2 family members might define a novel highly efficient and specific strategy in the combined or monotreatment of AML.

Induction of apoptosis by an inhibitor of EGFR in neuroblastoma cells

We aimed to examine the expression of EGFR in neuroblastoma tissues and to investigate the antitumor activity of a selective EGFR-tyrosine kinase inhibitor, gefitinib, on neuroblastoma. The expression of EGFR was detected in each of two tumor tissues by immunohistochemistry and eight of 10 cell lines by Western blotting. Gefitinib inhibited EGFR-phosphorylation and in vitro cell growth (IC(50): approximately 1.2 microM), and a high concentration of gefitinib (20-30 microM) induced apoptosis in vitro. This is the first report that EGFR protein is expressed on the cell surface in neuroblastoma tissues and in cell lines. We also demonstrated an EGFR inhibitor induced apoptosis on neuroblastoma cells. Our results suggest the feasibility of targeting EGFR as a novel strategy against neuroblastoma.

p53 enhances gefitinib-induced growth inhibition and apoptosis by regulation of Fas in non-small cell lung cancer

Treatment with gefitinib, a specific inhibitor of epidermal growth factor receptor tyrosine kinase (EGFR-TK), has resulted in dramatic responses in some patients with non-small cell lung cancer (NSCLC). Most patients who respond to gefitinib have EGFR-TK mutations; however, >10% of patients with EGFR-TK mutations do not respond. Similarly, some patients without EGFR-TK mutations respond to this drug, suggesting that other factors determine sensitivity to gefitinib. Aberrations of the tumor suppressor gene p53 are frequently associated with drug resistance. In this study, we investigated the role of p53 in growth-inhibitory and apoptotic effects of gefitinib in the human NSCLC cell lines NCI-H1299 and A549, which have no EGFR-TK mutations. NCI-H1299 cells, which had a p53-null genotype, were more resistant to gefitinib compared with A549 cells, which were wild-type p53 (IC(50), 40 micromol/L in NCI-H1299 and 5 micromol/L in A549). Treatment of A549 with gefitinib resulted in the translocation of p53 from cytosol to nucleus and the up-regulation of Fas, which was localized to the plasma membrane. In the stable H1299 cell line with tetracycline-inducible p53 expression, induced p53 enhanced growth inhibition and apoptosis by gefitinib through the up-regulation of Fas and restoration of caspase activation. A caspase inhibitor, Z-VAD-fmk, reduced these effects. Conversely, inhibition of p53 using antisense oligonucleotide in A549 caused a significant decrease in apoptosis by gefitinib and down-regulation of Fas under the same conditions. In conclusion, p53 may play a role in determining gefitinib sensitivity by regulating Fas expression in NSCLC.

Genistein induces apoptosis in human hepatocellular carcinomas via interaction of endoplasmic reticulum stress and mitochondrial insult

Hepatocellular carcinoma is a very common malignancy and is chemoresistant to currently available chemotherapeutic agents. Endoplasmic reticulum (ER) stress-induced apoptotic pathway is suggested to be less affected by the resistance mechanisms, becoming a potential target of chemotherapeutic strategy. The anticancer effects and expression of GADD153, a transcription factor induced by ER stress, were examined in hepatocellular carcinoma Hep3B cells. The correlation between these two parameters was constructed under flavonoid stimulation with a correlation coefficient (r) of 0.8. The data also showed that genistein (isoflavone) was the most effective one. Genistein induced the activation of several ER stress-relevant regulators, including m-calpain, GADD153, GRP78 and caspase-12. Furthermore, genistein-induced effect was inhibited in cells transfected with antisense GADD153 cDNA, indicating a functional role of GADD153. Notably, genistein induced the activation of caspase-2, whereas did not cause the DNA damage. It also triggered the production of ROS. The antioxidant trolox significantly reduced ROS accumulation, but did not modify genistein-induced apoptotic cell death. The long-term exposure (48 h) of cells to genistein caused Mcl-1 down-regulation and Bad cleavage; furthermore, cyclosporin A (an inhibitor of mitochondrial permeability transition pore) almost completely abolished genistein-induced loss of mitochondrial membrane potential, and induced a 30% reverse of apoptosis caused by long-term treatment (48 h) of genistein, suggesting the involvement of mitochondrial stress in the late phase of genistein-induced effect. Taken together, it is suggested that genistein induces the anticancer effect through a mechanism initiated by ER stress and facilitated by mitochondrial insult in Hep3B cells.