Overexpression of ErbB2 in cancer and ErbB2-targeting strategies

Assay for isolation of inhibitors of her2-kinase expression

Her2 (ErbB2) protein is overexpressed in breast and other solid tumors, and its expression is associated with progressive disease. Current therapies directed toward Her2 either block dimerization of the receptor or inhibit tyrosine kinase activity to disrupt intracellular signaling. However, little is known about alternative mechanisms for suppressing Her2 expression, possibly by inducing degradation or blocking synthesis. Here, we describe a hybrid western-blotting and enzyme-linked immunosorbent assay (ELISA) designed to identify in low- to medium-throughput format noncytotoxic compounds that reduce expression of Her2 protein.

Evidence for a role of the Simian Virus 40 in human breast carcinomas

AIMS OF THE STUDY

The aim of this study was to investigate whether the Simian Virus 40 (SV40) is implicated in human breast carcinomas (BC).

EXPERIMENTAL DESIGN

SV40 presence was investigated by PCR assays targeting the Tag, the regulatory, and the VP1 regions in 109 invasive breast ductal carcinomas from Tunisian women. We also examined the relationship between the presence of SV40 and promoter methylation status of 15 tumor-related genes. Immunohistochemistry was used to investigate the expression of Tag, estrogen and progesterone receptors, HER2, and P53.

RESULTS

SV40 DNA sequences were detected in 22% of tumors and in only 1.8% of the matched non-tumoral tissues. Using immunohistochemistry, SV40 was detected in the tumor cells. Hypermethylation frequencies were 78% for RASSF1A, 66% for SHP1, 61% for HIN1 and BRCA1, 47% for P16 and ER, 42% for CDH1 and APC, 40% for BLU, 35% for DAPK, 34% for RARbeta2, 27% for GSTP1, 17% for TIMP3, 14% for CCND2, and 8% for hMLH1. Interestingly, the frequencies of RASSF1A, SHP1, BRCA1, and TIMP3 methylation, and the mean of the methylation index (MI) were significantly higher in SV40-positive than in SV40-negative cases (P-values ranging from 0.043 to 0.003). Moreover, SV40 presence correlates with P53 protein accumulation (32.7% vs. 13.3%; P=0.015) and HER2 low expression (3.7% vs. 28%; P=0.008). We also found SV40 more frequently in patients over 50 years than in younger patients (34.8% vs. 12.3%; P=0.006).

CONCLUSIONS

This study is the first to demonstrate the presence of SV40 in human BC and provides data supporting a role for this virus in the pathogenesis of these tumors.

The genetic polymorphisms of HER-2 and the risk of lung cancer in a Korean population

Background

Human Epidermal Growth Factor Receptor 2 (HER-2; also known as erbB-2 or neu), a proto-oncogene of the receptor tyrosine kinase superfamily, has been associated with carcinogenesis and prognosis of human cancers, acting as a binding partner of other epidermal growth factor receptor (EGFR) family in the activation of EGFR signaling. Amplification of the HER-2 gene has been reported in lung cancer, where it has been associated with poor prognosis. In this study, we investigated whether the four polymorphisms (-3444C>T, -1985 G>T, I655A A>G and P1170A C>G) of the HER-2 gene are associated with the risk of lung cancer in Korean populations.

Methods

The frequencies of 4 polymorphisms of the HER-2 gene were examined by the polymerase chain reaction-restriction fragment length polymorphism or the single-nucleotide polymorphism-identification technology assay in the 407 lung cancer patients and 407 healthy controls.

Results

The frequencies of the 4 polymorphisms were not significantly different between patient and control groups in overall subjects. However, in the subgroup analysis, the 3 single nucleotide polymorphisms (-3444C>T, -1985G>T and P1170A C>G) showed statistically significant differences in the subgroups of females, non-smokers, and non-drinkers (p < 0.05). Additionally, we found the association between the risk of lung cancer and the polymorphisms of HER-2 gene in non-smoker subgroups with adenocarcinoma (p < 0.05).

Conclusion

Our results suggest that the polymorphisms of the HER-2 gene are associated with an increased susceptibility to lung cancer in females, non-smokers and non-drinkers subgroups in the Korean population.

Successful treatment of pulmonary metastatic salivary ductal carcinoma with trastuzumab-based therapy

BACKGROUND

Salivary ductal carcinoma (SDC) is an uncommon malignant tumor of the salivary glands. Although there is no known standard of care for the treatment of advanced disease, the vast majority of patients with SDC may be offered palliative systemic therapy. We report a case of epidermal growth factor receptor 2 (HER2)-positive metastatic submandibular SDC with a complete and durable clinical response to treatment with trastuzumab in combination with chemotherapy.

METHODS AND RESULTS

A 62-year-old man was diagnosed with SDC of the left submandibular gland with extensive cervical lymph node involvement. The lesion was completely resected, and the patient underwent postoperative radiotherapy. After 6 months, multiple pulmonary metastatic lesions were detected. A complete response was reached with trastuzumab-based combination therapy, and no evidence of disease progression has been observed after 14 months of initiation of systemic therapy.

CONCLUSION

Trastuzumab-based combination therapies should be considered for advanced SDC.

Triple negative breast cancer compared to hormone receptor negative/HER2 positive breast cancer

The aim of this study is to reveal likely demographic, clinical, and pathological differences among hormone receptor negative breast cancer patients according to their HER-2 status. The medical records of hormone receptor negative breast cancer patients with known HER-2 status between January 1999 and December 2006 were reviewed, retrospectively. A total of 91 cases were included in the study (68 HER-2 negative cases and 23 HER-2 positive cases). The results obtained showed that median age, menarche age, childbearing age, number of children, menopause age, and body-mass indexes were similar in both groups. The HER-2 negative patients had more family history of breast cancer than HER-2 positive patients (13.2% and 0%, respectively, P = 0.091). Eighty-three patients received neoadjuvant/adjuvant chemotherapy. Recurrence occurred in 41 (46.6%) patients. Neither recurrence nor disease-free survival of those patients was associated with HER-2 status. Tumor size (P = 0.042) and number of involved lymph nodes (P = 0.001) were found to be independent prognostic factors for disease-free survival. A tendency for more frequent cerebral metastasis was found in HER-2 positive advanced stage patients (P = 0.052). HER-2 positive patients were less responsive to taxanes (P = 0.071). The number of involved lymph nodes (P = 0.004) and HER-2 status (P = 0.043) were found to be prognostic factors for overall survival. HER-2 positive and negative patients should be followed and treated with different strategies. HER-2 positive patients are at least as resistant to systemic therapies as the HER-2 negative patients. Genetic counseling should be routinely provided to triple negative patients and their families. HER-2 positive patients may be candidates for prophylactic treatment strategies concerning cerebral metastasis.

Biodegradable quantum dot nanocomposites enable live cell labeling and imaging of cytoplasmic targets

Semiconductor quantum dots (QDs) offer great promise as the new generation of fluorescent probes to image and study biological processes. Despite their superior optical properties, QDs for live cell monitoring and tracking of cytoplasmic processes remain limited due to inefficient delivery methods available, altered state or function of cells during the delivery process and the requirement of surface-functionalized QDs for specific labeling of subcellular structures. Here, we present a noninvasive method to image subcellular structures in live cells using bioconjugated QD nanocomposites. By incorporating antibody-coated QDs within biodegradable polymeric nanospheres, we have designed a bioresponsive delivery system that undergoes endolysosomal to cytosolic translocation via pH-dependent reversal of nanocomposite surface charge polarity. Upon entering the cytosol, the polymer nanospheres undergo hydrolysis thus releasing the QD bioconjugates. This approach facilitates multiplexed labeling of subcellular structures inside live cells without the requirement of cell fixation or membrane permeabilization. As compared to conventional intracellular delivery techniques, this approach allows the high throughput cytoplasmic delivery of QDs with minimal toxicity to the cell. More importantly, this development demonstrates an important rational strategy for the design of a multifunctional nanosystem for biological applications.

The interface between biomarker discovery and clinical validation: The tar pit of the protein biomarker pipeline

The application of "omics" technologies to biological samples generates hundreds to thousands of biomarker candidates; however, a discouragingly small number make it through the pipeline to clinical use. This is in large part due to the incredible mismatch between the large numbers of biomarker candidates and the paucity of reliable assays and methods for validation studies. We desperately need a pipeline that relieves this bottleneck between biomarker discovery and validation. This paper reviews the requirements for technologies to adequately credential biomarker candidates for costly clinical validation and proposes methods and systems to verify biomarker candidates. Models involving pooling of clinical samples, where appropriate, are discussed. We conclude that current proteomic technologies are on the cusp of significantly affecting translation of molecular diagnostics into the clinic.

The N-terminal domain of EBNA1 acts as a suppressor of the HER2/neu oncogene

HER2/neu oncogene-mediated malignancy is clearly associated with various human cancers. Therefore, HER2/neu targeting is an effective approach to cancer therapy. We have previously demonstrated that Epstein-Barr virus nuclear antigen-1 (EBNA1) can suppress HER2/neu oncogene expression, although EBNA1 itself has oncogenic potential. Here, we found that the N-terminal domain of EBNA1 alone, named EBNA1-NT, which contains the N-terminal region of amino acid residues 1-86 of EBNA1, is required and sufficient to suppress HER2/neu oncogene expression at the transcriptional level. Furthermore, in EBNA1-NT-transfected HER2/neu-overexpressing cells, we found EBNA1-NT could down-regulate the endogenous production of p185(HER2/neu), lower transformation ability, sensitize paclitaxel-induced apoptosis and decrease tumorigenic potential. These data suggest that EBNA1-NT may act as a repressor of the HER2/neu oncogene.

Post-transcriptional regulation of chemokine receptor CXCR4 by estrogen in HER2 overexpressing, estrogen receptor-positive breast cancer cells

Expression of the chemokine receptor CXCR4, a G protein-coupled receptor, and HER2, a receptor tyrosine kinase, strongly correlates with the aggressive and metastatic potential of breast cancer cells. We studied estrogen regulation of CXCR4 in estrogen receptor (ER)-positive MCF-7 breast cancer cells overexpressing HER2 (MCF7-HER2). Although estrogen evoked no change in CXCR4 mRNA levels, CXCR4 protein was significantly up-regulated after estrogen treatment of these cells, whereas estrogen had no effect on CXCR4 protein level in parental MCF7 cells that are low in HER2. Use of the CXCR4 specific inhibitor, AMD 3100, indicated that this increase in CXCR4 protein was partially responsible for the increase in estrogen-induced migration of these cells. The estrogen-induced increase in CXCR4 protein in MCF-7-HER2 cells was abrogated by the antiestrogen ICI 182780 and by gefitinib (Iressa; a phospho-tyrosine kinase inhibitor), indicating an ER-mediated effect and confirming involvement of receptor tyrosine kinases, respectively. Using specific pathway inhibitors, we show that the estrogen-induced increase in CXCR4 involves PI3K/AKT, MAPK and mTOR pathways. PI3K/AKT and MAPK pathways are known to result in the phosphorylation and functional inactivation of tuberin (TSC2) of tuberous sclerosis complex thereby negating its inhibitory effects on mTOR, which in turn stimulates the translational machinery. Small interfering RNA (siRNA) mediated knockdown of tuberin elevated the level of CXCR4 protein in MCF7-HER2 cells and also nullified further estrogen up-regulation of CXCR4. This study suggests a pivotal role of PI3 K, MAPK and mTOR pathways, via tuberin, in post-transcriptional control of CXCR4, initiated through estrogen-stimulated crosstalk between ER and HER2. Thus, post-transcriptional regulation of CXCR4 by estrogens acting through ER via kinase pathways may play a critical role in determining the metastatic potential of breast cancer cells.

Prevalence and characteristics of the MMTV-like associated breast carcinomas in Tunisia

The involvement of a retrovirus homologous to the mouse mammary tumor virus (MMTV) in the pathogenesis of human breast cancer (BC) has long been assumed, but has never been proven. Previous studies have reported the detection of MMTV-like env sequences in variable proportions that did not exceed 40% of BC cases in several countries. However, these viral sequences have been found in higher proportion (74%) in Tunisian diagnosed with BC during the seventies. This study is an attempt to evaluate the current prevalence of MMTV-like env gene in BC in Tunisian women. We used semi-nested PCR that amplify a 190-bp MMTV-like env sequence, followed by direct sequencing to screen a series of 122 cases of BC randomly selected. The findings were correlated to clinicopathological data and immunohistochemical expression status of progesterone and oestrogen receptors, HER2, and P53. Specific MMTV-like env sequences were found in 17 (13.9%) cases of breast carcinomas, whereas the same sequences were not detected in matched normal breast tissues. The presence of the viral sequences correlates inversely with progesterone receptor expression (6.8% versus 20.3%; P=0.03) and HER2 overexpression (3.1% versus 17.7%; P=0.04). This present study confirms the presence of MMTV-like env sequences in BC in Tunisian women but describes an important decrease in the prevalence of the viral sequences compared with previous studies. This reduction may be due to some changes in the virological characteristics or exposure to the virus.

Breast cancer brain metastases

Breast cancer is the most common malignancy in woman in the USA. Metastasis is a major cause of morbidity and mortality in breast cancer patients. Total incidence of brain metastases of breast cancer is about 30%. Because of the improvements in control of systemic disease, for example the successful use of Trastuzumab, and the consequent prolonged life span, the incidence of brain metastases is increasing in breast cancer patients. The progressive neurological disabilities not only impair the quality of life, but also decrease the survival in patients. However, current treatments are of limited effectiveness. This is partially caused by the unique structure of the blood brain barrier. So far very little is known about the mechanisms how breast cancer metastizes to the brain. Some studies showed that ErbB2 overexpression is associated with the brain metastatic phenotype. Other molecules, like vascular endothelial growth factor (VEGF), matrix metalloproteinases (MMPs) and chemokine receptor CXCR4 are also involved in the metastasis of breast cancer cell to the brain. The current review will briefly overview the clinical features of brain metastasis of breast cancer and discusses the relationship of blood brain barrier and ErbB2 signal pathway to brain metastasis in breast cancer.

NF-kappa B-mediated adaptive resistance to ionizing radiation

Ionizing radiation (IR) began to be a powerful medical modality soon after Wilhelm Röntgen's discovery of X-rays in 1895. Today, more than 50% of cancer patients receive radiotherapy at some time during the course of their disease. Recent technical developments have significantly increased the precision of dose delivery to the target tumor, making radiotherapy more efficient in cancer treatment. However, tumor cells have been shown to acquire a radioresistance that has been linked to increased recurrence and failure in many patients. The exact mechanisms by which tumor cells develop an adaptive resistance to therapeutic fractional irradiation are unknown, although low-dose IR has been well defined for radioadaptive protection of normal cells. This review will address the radioadaptive response, emphasizing recent studies of molecular-level reactions. A prosurvival signaling network initiated by the transcription factor NF-kappa B, DNA-damage sensor ATM, oncoprotein HER-2, cell cyclin elements (cyclin B1), and mitochondrial functions in radioadaptive resistance is discussed. Further elucidation of the key elements in this prosurvival network may generate novel targets for resensitizing the radioresistant tumor cells.

HER-2/neu and p27Kip1 in progression of Fallopian tube carcinoma: an immunohistochemical and array comparative genomic hybridization study

AIMS

To determine expression of p53, HER-2/neu and p27(Kip1) in serous Fallopian tube carcinoma (FTC) in relation to stage and grade, and to investigate DNA copy number changes of HER-2 and P27KIP1 as a potential mechanism of altered expression status.

METHODS AND RESULTS

Immunohistochemistry was performed on 28 serous FTCs and 10 normal Fallopian tubes. p53 protein accumulated and p27(Kip1) was down-regulated significantly in early-stage FTCs compared with normal Fallopian tubes. HER-2/neu overexpression was absent in normal Fallopian tubes and in all stage I FTCs (n = 6) but present in 57% (12/21) of advanced-stage FTCs. No differences in expression between grade 2 and 3 tumours were detected. HER-2 gain/amplification was found by array comparative genomic hybridization in 23% (3/13) of analysed FTCs and all showed overexpression. HER-2/neu overexpression also occurred without DNA copy number changes in three other cases. For p27(Kip1), expression and DNA copy number were unrelated.

CONCLUSIONS

p53 accumulation and p27(Kip1) down-regulation seem to be early events in Fallopian tube carcinogenesis. HER-2/neu showed overexpression, caused by gain/amplification in 50%, and may be involved in progression of FTC. These data contribute to a better understanding of the molecular carcinogenesis of FTC and to possible new therapeutic approaches.

Diosgenin, a naturally occurring steroid, suppresses fatty acid synthase expression in HER2-overexpressing breast cancer cells through modulating Akt, mTOR and JNK phosphorylation

Fatty acid synthase (FAS) expression is markedly elevated in HER2-overexpressing breast cancer cells. In this study, diosgenin, a plant-derived steroid, was found to be effective in suppressing FAS expression in HER2-overexpressing breast cancer cells. Diosgenin preferentially inhibited proliferation and induced apoptosis in HER2-overexpressing cancer cells. Furthermore, diosgenin inhibited the phosphorylation of Akt and mTOR, and enhanced phosphorylation of JNK. The use of pharmacological inhibitors revealed that the modulation of Akt, mTOR and JNK phosphorylation was required for diosgenin-induced FAS suppression. Finally, we showed that diosgenin could enhance paclitaxel-induced cytotoxicity in HER2-overexpressing cancer cells. These results suggested that diosgenin has the potential to advance as chemopreventive or chemotherapeutic agent for cancers that overexpress HER2.

Sensitizing HER2-overexpressing cancer cells to luteolin-induced apoptosis through suppressing p21(WAF1/CIP1) expression with rapamycin

HER2 overexpression, which confers resistance to various therapeutic regimens, correlates with a poor clinical prognosis. In this study, we showed that luteolin, a naturally occurring flavonoid, is a potent stimulator of HER2 degradation. Luteolin effectively inhibited cell proliferation and induced apoptosis in HER2-overexpressing cancer cells. Furthermore, we found that low doses of luteolin up-regulated p21 expression and high doses of luteolin down-regulated its expression. Examination of the Akt/mammalian target of rapamycin (mTOR) signaling revealed that this signaling was only transiently inhibited by low doses of luteolin, which suggested that the inability to cause sustained Akt/mTOR inhibition may contribute to p21 induction and provide a survival advantage to HER2-overexpressing cancer cells. To test this hypothesis, we showed that the combined use of luteolin and mTOR inhibitor rapamycin prevented low doses of luteolin from inducing p21 expression, and HER2-overexpressing cancer cells would be sensitized toward luteolin-induced apoptosis. In addition, p21 small interfering RNA also increased the luteolin-induced cell death. In nude mice with xenografted SKOV3.ip1-induced tumors, luteolin significantly inhibited HER2 expression and tumor growth in a dose-dependent manner, and rapamycin further enhanced the effect of luteolin with a concomitant p21 inhibition. These results reveal an intriguing finding that suppressing p21 expression might have therapeutic implications and further suggest that combination of mTOR inhibitors may be a promising strategy to help increase the efficacy of preventive or therapeutic compounds against HER2-overexpressing tumors.

Human manganese superoxide dismutase suppresses HER2/neu-mediated breast cancer malignancy

The up-regulation of HER2/neu is associated with human malignancies and is a useful target for developing anticancer drugs. Overexpression of human manganese superoxide dismutase (MnSOD) has been demonstrated to effectively suppress various carcinoma cells, including breast carcinomas, in vitro and in vivo. This study demonstrates that MnSOD effectively suppresses HER2/neu oncogene expression at the transcriptional level. Additionally, stable transfection was used and the MnSOD-transfected human breast cancer clones were found to be able to down-regulate the endogenous production of p185(HER2/neu). Furthermore, the MnSOD-overexpressing stable transfectants exhibited reduced soft-agarose colony-forming ability and metastatic properties, unlike control cell lines. These data suggest that MnSOD may be useful in treating HER2/neu-mediated human breast tumor malignancy.

Metastatic potential of 21T human breast cancer cells depends on Akt/protein kinase B activation

Most cancer lethality is caused by metastasis. To gain insight into the molecular basis of tumor progression to metastasis, we used the 21T series of human mammary epithelial cells obtained by successive biopsies from one breast cancer patient. The c-erbB2 gene is amplified and overexpressed in each of three 21T tumor lines. The erbB receptor tyrosine kinase-activated phosphatidylinositol 3-kinase/Akt signaling cascade is crucial for the development and maintenance of epithelial cells, and dysregulation of this pathway is frequently associated with cellular transformation and cancer. For Akt to be fully activated, Ser(473) on its COOH terminus needs to be phosphorylated. We detected more Ser(473) Akt phosphorylation in MT cells, derived from a pleural effusion, compared with cells from the primary tumor. This phosphorylation has recently been shown to be catalyzed by mammalian target of rapamycin (mTOR)/rictor kinase. By using genetic and pharmacologic activators and inhibitors, we showed that Ser(473) Akt phosphorylation is more sensitive to mTOR/rictor inhibition in metastatic tumor cells than normal mammary epithelial and primary tumor cells. The mTOR/rictor kinase activity was indispensable for both Ser(473) Akt phosphorylation and migration of metastatic MT2 cells. In addition, a large decrease of protein phosphatase PH domain leucine-rich repeat protein phosphatase (PHLPP) was found, which could be responsible for the overexpression of Ser(473) Akt in MT cells. Our data indicate that these breast cancer cells acquire new vulnerabilities, rictor and PHLPP, which might provide an Achilles' heel for therapeutic intervention of breast cancer metastasis.

Inhibitor of heat-shock protein 90 enhances the antitumor effect of DNA vaccine targeting clients of heat-shock protein

Geldanamycin (GA), a heat-shock protein (HSP) 90 inhibitor, induces degradation of HSP90 client proteins, which may promote the presentation of degradation peptides with major histocompatibility complex class I on cancer cells. We hypothesized that GA may enhance the efficacy of DNA vaccination, and investigated the therapeutic effect of the combination of GA and a DNA vaccine against HSP90 clients p185(neu) and Met. The efficacy of various doses of GA combined with an N-terminal neu (N'-neu) DNA vaccine was investigated in a transplanted tumor constitutively overexpressing endogenous p185(neu). Low-dose (2.5 mug) but not high-dose (10 microg) GA enhanced the effect of N'-neu DNA vaccination on the inhibition of murine bladder tumor-2 tumors in syngeneic C3H mice. Anti-p185(neu) antibody titers were similar among all treated groups. Significantly increased infiltrations of CD8(+) T cells and NK cells were observed at tumor sites. GA sensitized tumor cells to the cytotoxic effects of lymphocytes. Depletion of CD8(+) T cells eliminated most of the therapeutic efficacy; in contrast, depletion of CD4(+) T cells enhanced the therapeutic efficacy. A similar enhancing effect was observed for the combination of GA and a DNA vaccine targeting the Met oncogene. Our results support the use of combination of GA and DNA vaccination against GA-targeted proteins.

Downregulation of erbB3 abrogates erbB2-mediated tamoxifen resistance in breast cancer cells

Receptor tyrosine kinase activity is essential for erbB2 (HER2/neu) promotion of breast carcinogenesis, metastasis and therapeutic resistance. erbB2 kinase can be activated by dimerization with another erbB receptor, most of which bind ligands. Of these, the erbB2/erbB3 heterodimer is the most potent oncogenic complex. erbB2 reportedly requires erbB3 to promote cellular proliferation, although this may occur without changes in erbB2 tyrosine kinase activity in some model systems. Our investigations focus on the role(s) of erbB3 in erbB2-associated kinase activity and tamoxifen resistance. Using tumor-derived cell lines from wild type rat c-neu transgenic mice and human breast cancers, we demonstrate that erbB3 plays a critical role in the activation of erbB2 tyrosine kinase activity and erbB2-associated tumorigenesis. Mechanistically, downregulation of erbB3 by specific siRNA reduces erbB2 tyrosine phosphorylation, decreases the PI-3K/Akt signaling, and inhibits mammary/breast cancer cell proliferation and colony formation. Specific erbB3 siRNA sensitizes erbB2 transfected MCF-7 cells (MCF-7/erbB2) to tamoxifen-associated inhibition of both cell growth and colony formation and enhances tamoxifen-induced apoptosis, in contrast to control siRNA transfected MCF-7/erbB2 cells which are tamoxifen-resistant. Our data indicates that erbB2/erbB3 heterodimerization is a prerequisite for erbB2 tyrosine kinase activation in mammary/breast cancer cells and that downregulation of erbB3 inhibits erbB2-associated procarcinogenic activity via inactivation of the PI-3K/Akt pathway. Furthermore, erbB3 also contributes to erbB2-mediated tamoxifen resistance and therefore may be a clinically relevant therapeutic target in addition to erbB2.

Lapatinib antitumor activity is not dependent upon phosphatase and tensin homologue deleted on chromosome 10 in ErbB2-overexpressing breast cancers

Trastuzumab antitumor activity in ErbB2-overexpressing breast cancers seems to be dependent upon the presence of phosphatase and tensin homologue deleted on chromosome 10 (PTEN), a phosphatase that dampens phosphatidylinositol 3-kinase-Akt signaling. Consequently, PTEN deficiency, which occurs in 50% of breast cancers, predicts for resistance to trastuzumab monotherapy. Here, we show that lapatinib, a small-molecule inhibitor of ErbB1 and ErbB2 tyrosine kinases, exerts its antitumor activity in a PTEN-independent manner. Steady-state phosphorylated ErbB2 (p-ErbB2) and p-Akt (S473) protein levels were inhibited within 30 min following lapatinib but not in response to trastuzumab in BT474 and Au565 cells (two ErbB2-overexpressing breast cancer cell lines that are sensitive to the proapoptotic effects of lapatinib). Whereas trastuzumab reportedly inhibits SRC phosphorylation (Y416), which in turn reduced SRC-ErbB2 protein interactions, lapatinib had no effect on either variable. To assess the potential functional role that PTEN might play in lapatinib antitumor activity, we selectively knocked down PTEN in BT474 and Au565 cells using small interfering RNA transfection. Loss of PTEN did not affect induction of tumor cell apoptosis by lapatinib in either cell line. In addition, lapatinib inhibited Akt phosphorylation in MDA-MB-468 cells, an ErbB1-expressing/ErbB2 non-overexpressing breast cancer line, despite their PTEN-null status. Moreover, patients with ErbB2-overexpressing inflammatory breast cancers responded to lapatinib monotherapy regardless of PTEN status. Thus, lapatinib seems to exert its antitumor activity in ErbB2-overexpressing breast cancers in a PTEN-independent manner. These data emphasize the importance of assessing PTEN status in tumors when selecting ErbB2-targeted therapies in patients with breast cancer.

Proteasome inhibitor bortezomib increases PTEN expression and enhances trastuzumab-induced growth inhibition in trastuzumab-resistant cells

PTEN (phosphatase and tension homolog deleted on chromosome 10) has been shown to be inactivated in a wide range of cancers and the role of this gene product is associated with the suppression of the phosphatidylinositol-3-kinase (PI3K)/Akt pathway in many cancers. Recently, some reports demonstrated that the degree of PTEN expression could predict trastuzumab chemosensitivity in ErbB2-overexpressing breast cancer. Here, we demonstrate the possible involvement of a proteasome inhibitor (PS341) in PTEN expression and elucidate the influence of PI3K/Akt, one of the main cascades of the ErbB2 downstream pathway, and discuss the role of the proteasome inhibitors in trastuzumab resistance. ErbB2-overexpressing SKBR3 human breast cancer cells and trastuzumab-resistant SKBR3/R cells were analyzed in this study. We show that the expression of phosphorylated Akt was highly increased in trastuzumab-resistant cells, although the expression of PI3K, phosphorylated PI3K and non-phosphorylated Akt was unchanged in comparison with wild-type SKBR3 cells. However, following treatment with PS341, the level of phosphorylated Akt was decreased in a dose-dependent manner. Conversely, the level of PTEN was increased in the same fashion. PS341 showed sufficient cytotoxicity in resistant cells in combination with trastuzumab and the efficacy of trastuzumab was inclined to be better in resistant cells under PS341 treatment. Remarkable activity of Akt was observed in trastuzumab-resistant SKBR3 breast cancer cells and this phenomenon could be associated with the decreased expression of PTEN. The proteasome inhibitor PS341 could increase the level of PTEN and inhibit the downstream pathway of ErbB2, interfering with phosphorylation of Akt.

Regulation of transcription by synthetic DNA-bending agents

Gene expression is regulated by a complex interplay between binding and the three-dimensional arrangement of transcription factors with RNA polymerase and DNA. Previous studies have supported a direct role for DNA bending and conformation in gene expression, which suggests that agents that induce bends in DNA might be able to control gene expression. To test this hypothesis, we examined the effect of triple-helix-forming oligonucleotide (TFO) bending agents on the transcription of luciferase in an in vitro transcriptional/translational system. We find that transcription is regulated only by a TFO that induces a bend in the DNA. Related TFOs that do not induce bends in DNA have no effect on transcription. Reporter expression can be increased by as much as 80 % or decreased by as much as 50 % depending on the phasing of the upstream bend relative to the promoter. We interpret the results as follows: when the bend is positioned such that the upstream DNA is curved toward the RNA polymerase on the same DNA face, transcription is enhanced. When the upstream DNA is curved away, transcription is attenuated. These results support the hypothesis that DNA-bending agents might have the capability to regulate gene expression, thereby opening up a previously undervalued avenue in research on the artificial control of gene expression.

Topoisomerase 2α plays a pivotal role in the tumor biology of stage IV thymic neoplasia

BACKGROUND

Microsatellite studies in histologic types B3 and C thymic neoplasia detected gains on chromosome 17q, which contains the Her-2/neu and its juxtaposed topoisomerase 2alpha (T2alpha) genes. The study aimed to evaluate their impact on tumor biology and survival of advanced thymic neoplasia patients.

METHODS

From 1991 to 2005, 36 consecutive stage IV thymic carcinoma patients were treated, 18 men and 18 women, aged 11 to 84 years. There were 22 thymic carcinoma, 13 type B3, and 1 type B2 thymoma. Patients received treatment consisting of surgical resection, combination chemotherapy with the CAP (cyclophosphamide, Adriamycin, cisplatin) regimen, or radiation therapy potentiated by high-dose weekly 5-fluorouracil infusion. Permutations of these 3 treatment modalities were prescribed as necessary.

RESULTS

T2alpha gene amplification was detected in 4 of 14 thymic carcinoma and 1 of 15 type B3 thymoma. Three thymic carcinoma patients had Her-2/neu coamplification and these 3 patients had rapidly growing tumor and extensive disease at initial diagnosis. CAP was prescribed in 28 patients and 20 patients responded (response rate, 71.4%, 95% confidence interval [CI]: 52.8% to 85%); all responders overexpressed (> or = 10% nuclei positive) the T2alpha protein, whereas 4 nonresponders had very low expression. T2alpha overexpression predicts CAP response, and its absence predicts resistance (P = .001). Overall survival was significantly prolonged if the tumor was resectable (P = .001), of type B3 histology (P = .0039), and had no Her-2 gene amplification (P = .0081).

CONCLUSION

T2alpha and Her-2/neu genes play a pivotal role in the tumor biology, CAP response, and survival of advanced thymic neoplasia patients.

Development of a Conditionally Replicating Pseudorabies Virus for HER-2/neu-overexpressing Bladder Cancer Therapy

Overexpression of the HER-2/neu oncogene, a frequent molecular event in a variety of cancers including bladder cancer, is associated with tumor progression and poor prognosis. Therapeutic strategies to targeting HER-2/neu-overexpressing cancer cells have shown promise. Pseudorabies virus (PrV), a herpesvirus of swine, may be exploited as an oncolytic agent for human cancer. Herein, we generated a conditionally replicating glycoprotein E-defective PrV mutant carrying glycoprotein D and herpes simplex virus type 1 thymidine kinase genes, which are essential for viral entry and replication, under the transcriptional control of the HER-2/neu promoter. The recombinant PrV, designated YP2, selectively replicated in and lysed HER-2/neu-overexpressing human bladder, mouse bladder, and hamster oral cancer cells in vitro. Notably, YP2 retarded MBT-2 bladder tumor growth in mice by more than 50% and more than half of the mice survived for over 50 days, whereas all the control mice survived less than 30 days. Taken together, our results suggest that YP2 may have therapeutic potential for the treatment of invasive bladder cancer. Furthermore, because HER-2/neu is overexpressed in a broad spectrum of cancers, this conditionally replicating PrV may be broadly applicable.

Bad expression predicts outcome in patients treated with tamoxifen

AIMS

Activation of the PI3K/Akt signal transduction pathway has been linked to endocrine resistance in tamoxifen treated breast cancer patients. Activation of the PI3K/Akt pathway causes phosphorylation of Bad leading to modulation of cellular apoptosis. The present study was carried out to test the hypothesis that disruption of apoptosis in breast cancer, via Akt activation, is linked with hormone resistance.

METHODS

Immunohistochemistry (IHC) was performed on 402 oestrogen receptor (ER) positive breast cancers using antibodies against Bad, pBad (ser 112), Bcl-2, Bcl-xl and Bax.

RESULTS

Bad, pBad (ser 112), Bcl-2 and Bax expression was observed in the cellular cytoplasmic compartment only. Patients, whose tumours had high levels of Bad expression, had a significantly improved disease-free survival when compared to patients whose tumours had low levels of Bad expression (P = 0.049). Activation of the PI3K/Akt pathway by either heregulin or oestrogen had no effect on expression of Bad, Bcl-2, Bax or Bcl-xl. However, heregulin increased pBad (ser 112) expression.

DISCUSSION

Data presented here shows that Bad expression is associated with relapse in tamoxifen-treated breast cancer patients, supporting our hypothesis that the apoptosis pathway is involved in tamoxifen resistance.

HER-2/neu genotype of breast cancer may change in bone metastasis

The genotype of breast cancer (BRC) is considered to be relatively stable during tumor progression, accordingly, determination of the estrogen receptor and HER-2/neu status is currently based on the primary tumor. However, recent data suggest that the gene expression profile of the metastatic lesion can be different compared to that of the primary BRC. Accordingly, it is possible that the HER-2/neu status is different in the metastatic lesion and the primary BRC. Since the bone is the most frequent metastatic site during the progression of BRC, we have analyzed the HER-2/neu status of 48 bone metastatic BRC cases by immunohistochemistry and fluorescent in situ hybridization, and it was possible to compare it to the primary site in 23 cases. The frequency of HER-2/neu amplification of BRC in the primary tumors was found to be 17.4% compared to 10.5% in bone metastases. Half of BRC cases with HER-2/neu amplification lost this genotype in bone metastases (4/23 versus 2/23, respectively) and even in the 2 cases where HER-2/neu amplification was retained in the metastases, the copy number was found to be decreased compared to the primary tumor. Based on our data and previous reports in the literature, we suggest to perform HER-2/neu testing both on primary tumor and samples obtained from BRC metastases, at least in case of primary tumors with HER-2/neu amplification, before introduction of HER-2/neu-targeting therapy.

Mechanisms of trastuzumab resistance and their clinical implications

Trastuzumab (Herceptin) is an excellent model of rationally designed targeted cancer treatment. However, less than 35% of patients with ErbB2-positive breast tumors respond to trastuzumab as a single agent, and 2-5% of trastuzumab-treated patients suffer from severe side effects, including cardiac dysfunction. Recent progress in understanding the mechanisms of trastuzumab antitumor function and cellular defects leading to trastuzumab resistance is summarized. Also explored is the potential of combination therapies for reversing trastuzumab resistance.

Combinatorial synergy induced by adenoviral-mediated mda-7 and Herceptin in Her-2+ breast cancer cells

The melanoma differentiation-associated gene-7 (mda-7) is a member of the interleukin-10 cytokine family and a novel tumor suppressor gene. Adenoviral-mediated mda-7 (Ad-mda7) gene transfer has tumor-specific growth inhibitory and proapoptotic effects in a broad spectrum of cancer cells. In breast cancer cells, adenoviral-induced mda-7 expression triggers antiproliferative effects by downregulation of survival signals, such as Bcl-2 and Akt. The anti-human epidermal growth factor receptor-2 (Her-2) monoclonal antibody, Trastuzumab (Herceptin), increases the sensitivity of Her-2/neu-overexpressing breast cancer cells to chemotherapeutic agents and radiotherapy. In this study, we evaluate the effects of treatment with Ad-mda7 and Herceptin combination therapy in a panel of Her-2/neu-overexpressing cell lines, and in established tumors in nude mice. Compared to individual treatments, the combination of Ad-mda7 and Herceptin elicits supra-additive antitumor activity in Her-2/neu-overexpressing tumor cell lines: increased cell death, cell cycle block and apoptosis. The Ad-mda7 and Herceptin interaction was shown to be synergistic by isobologram analysis. Ad-mda7 does not alter cell surface Her-2/neu levels, but the combination of Ad-mda7+Herceptin results in increased expression of cell surface E-cadherin with concomitant translocation of beta-catenin from the nucleus to the cell membrane. In vivo, the combination of Ad-mda7 and Herceptin showed significantly increased antitumor activity (P<0.003) against Her-2/neu-overexpressing tumors. These data suggest that the combination of Ad-mda7 with Herceptin may be a novel therapy for breast cancer patients whose tumors overexpress Her-2/neu. The observed synergistic effect may improve treatment options for otherwise poorly responsive, Her-2-positive, breast cancer patients.

Investigation of HER-2 codon 655 single nucleotide polymorphism frequency and c-ErbB-2 protein expression alterations in gastric cancer patients

AIM: To investigate both whether the risk of gastric cancer is associated with the Ile/Val single nucleotide polymorphism (SNP) of human epidermal growth factor receptor-2 (HER-2) transmembrane domain-coding region at codon 655 and the suggested existence of HER-2 expression in gastric cancer cases in a Turkish patient group.

METHODS: Polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) strategy was used to analyze the presence of HER-2 SNP at codon 655. c-erbB-2 expression pattern was analyzed by immunohistochemistry. The results were compared between gastric carcinoma group and chronic gastritis group, as well as between clinicopathological parameters and carcinoma.

RESULTS: Results showed that Ile/Val genotype accounted for 20% within the Turkish gastric carcinoma group, and none in chronic gastritis group, and this genotyping was associated with stage IV gastric cancers (P = 0.04). Positive membranous HER-2 immunoreactivity, on the other hand, accounted for 24% within the Turkish gastric carcinoma group and none from chronic gastritis cases; further, it was correlated with intestinal type carcinomas (P = 0.007), and stage III-IV carcinomas (P = 0.004).

CONCLUSION: These observations imply that the tested HER-2 SNP may participate in the development and progression of gastric cancer. Thus, after confirming these results with large sample groups, HER-2 codon 655 SNP and/or c-erbB-2 overexpression may also be used as a poor prognostic indicator for gastric carcinomas.

ERBB2-mediated transcriptional up-regulation of the alpha5beta1 integrin fibronectin receptor promotes tumor cell survival under adverse conditions

Oncogenic activation of the receptor tyrosine kinase ERBB2 is a key event in the development of a number of epithelial malignancies. In these tumors, high levels of ERBB2 are strongly associated with metastatic disease and poor prognosis. Paradoxically, an inherent cellular response to hypermitogenic signaling by ERBB2 and other oncogenes seems to be growth arrest, rather than proliferation. Molecular characterization of this yet undefined antiproliferative state in independent cell lines overexpressing either wild-type ERBB2 or the mutationally activated receptor unveiled a dramatic induction of the alpha5beta1 integrin fibronectin receptor. alpha5 Integrin up-regulation is mainly a transcriptional response mediated by the hypoxia-inducible transcription factors (HIF), leading to a massive increase in membrane-resident receptor molecules and enhanced fibronectin adhesiveness of the respective cells. Functionally, ERBB2-dependent ligation of fibronectin results in improved survival of mammary adenocarcinoma cells under adverse conditions, like serum withdrawal, hypoxia, and chemotherapy. HIF-1alpha is an independent predictor of poor overall survival in patients with breast cancer. In particular, HIF-1alpha overexpression correlates significantly with early local relapse and distant metastasis, a phenotype also highly characteristic of ERBB2-positive tumors. As HIF-1alpha is known to be stabilized by ERBB2 signaling under normoxic conditions, we propose that alpha5 integrin is a major effector in this regulatory circuit and may represent the molecular basis for the HIF-1alpha-dependent aggressiveness observed in ERBB2-overexpressing breast carcinomas. Hypermitogenic ERBB2 signaling and tumor hypoxia may act synergistically to favor the establishment of chemoresistant dormant micrometastatic cells frequently observed in patients with breast cancer. This new insight could be the basis for additional approaches complementing current cancer therapy.

HER2 signaling modulates the equilibrium between pro- and antiangiogenic factors via distinct pathways: implications for HER2-targeted antibody therapy

We determined the impact of HER2 signaling on two proangiogenic factors, vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8), and on an antiangiogenic factor, thrombospondin-1 (TSP-1). Re-expression of HER2 in MCF-7 and T-47D breast cancer cells that endogenously express low levels of HER2 resulted in elevated expression of VEGF and IL-8 and decreased expression of TSP-1. Inhibition of HER2 with a humanized anti-HER2 antibody (trastuzumab, or Herceptin) or a retrovirus-mediated small interfering RNA against HER2 (siHER2) decreased VEGF and IL-8 expression, but increased TSP-1 expression in BT474 breast cancer cells that express high levels of HER2. These in vitro results were further evaluated by treatment of BT474 xenografts in immunosuppressed mice with trastuzumab. Trastuzumab inhibited growth of BT474 xenografts and decreased microvascular density associated with downregulation of VEGF and IL-8 and with upregulation of TSP-1 expression. Inhibiting the PI3K-AKT pathway decreased VEGF and IL-8 expression. AKT1 overexpession increased VEGF and IL-8 expression, but did not increase TSP-1 expression. A p38 kinase inhibitor, SB203580, instead blocked TSP-1 expression and a p38 activator, MKK6, increased TSP-1 expression. Trastuzumab stimulated sustained p38 activation and SB203580 attenuated the TSP-1 upregulation induced by trastuzumab. HER2 signaling therefore influences the equilibrium between pro- and antiangiogenic factors via distinct signaling pathways. Trastuzumab inhibits angiogenesis and tumor growth, at least in part, through activation of the HER2-p38-TSP-1 pathway and inhibition of the HER2-PI3K-AKT-VEGF/IL-8 pathway.

A model of acquired autoresistance to a potent ErbB2 tyrosine kinase inhibitor and a therapeutic strategy to prevent its onset in breast cancer

The development of acquired resistance to ErbB2 tyrosine kinase inhibitors limits the clinical efficacy of this class of cancer therapeutics. Little is known about the mechanism(s) of acquired resistance to these agents. Here we establish a model of acquired resistance to N-{3-chloro-4-[(3-fluorobenzyl) oxy]phenyl}-6-[5-({[2 (methylsulfonyl)ethyl]amino}methyl)-2-furyl]-4-quinazolinamine (lapatinib), an inhibitor of ErbB2 and ErbB1 tyrosine kinases by chronically exposing lapatinib-sensitive ErbB2-overexpressing breast cancer cells to lapatinib, simulating the clinic where lapatinib is administered on a daily chronic basis. Analysis of baseline gene expression in acquired lapatinib-resistant and parental cells indicates estrogen receptor (ER) signaling involvement in the development of resistance. Using gene interference, we confirm that acquired resistance to lapatinib is mediated by a switch in cell survival dependence and regulation of a key antiapoptotic mediator from ErbB2 alone to codependence upon ER and ErbB2 rather than loss of ErbB2 expression or insensitivity of ErbB2 signaling to lapatinib. Increased ER signaling in response to lapatinib is enhanced by the activation of factors facilitating the transcriptional activity of ER, notably FOXO3a and caveolin-1. Importantly, we confirm that lapatinib induces ER signaling in tumor biopsies from patients with ErbB2-overexpressing breast cancers receiving lapatinib therapy. These findings provided the rationale for preventing the development of acquired resistance by simultaneously inhibiting both ER and ErbB2 signaling pathways. Establishing clinically relevant models of acquired resistance to ErbB2 kinase inhibitors will enhance therapeutic strategies to improve clinical outcomes for patients with ErbB2-overexpressing breast cancers.

Role of IkappaB kinase in tumorigenesis

IkappaB kinase plays a central role in regulating NF-kappaB, is a key signaling molecule involved in controlling cell proliferation, survival, antiapoptosis, and tumorigenesis. Alternative pathways can also regulate NF-kappaB in an IkappaB kinase-independent manner. Emerging evidence indicates that IKK phosphorylates and inactivates forkhead box, class O (FOXO)-3a and promotes cell growth and tumorigenesis. Moreover, IKK and NF-kappaB play an important role in linking inflammation and tumorigenesis, and facilitate tumor maintenance and invasion. Thus, IKK and NF-kappaB are promising targets for drug discovery, and agents targeting the IKK/NF-kappaB and FOXO pathways may become therapeutic intervention for those patients with IKK/NF-kappaB-overexpressing cancers in the future.

PTEN activity could be a predictive marker of trastuzumab efficacy in the treatment of ErbB2-overexpressing breast cancer

Trastuzumab is the only HER2/neu-directed therapy to have received Food and Drug Administration approval for the treatment of patients with metastatic breast cancer. The efficacy of trastuzumab depends on the HER2/neu status of the tumour and the patient's prior treatment, but even when patients are selected on the basis of HER2/neu gene amplification, the single-agent response rate ranges from 12 to 30% and few patients respond to trastuzumab monotherapy. Here, we propose PTEN as a predictive biomarker for trastuzumab efficacy. Human breast cancer SKBR3 and drug-resistant SKBR3/R cells were investigated. We also examined clinical samples from patients who had been treated with trastuzumab and analysed the relationship between trastuzumab efficacy and PTEN level. The PI3K/Akt signalling pathway was observed to be highly active in the drug-resistant cells, and their level of PTEN was low. Delivery of antisense PTEN duplex siRNA significantly decreased the trastuzumab chemosensitivity of parental SKBR3 cells, and marked activation of Akt signalling pathway was also recognised. Moreover, immunohistochemical investigation revealed that trastuzumab treatment was remarkably successful in cells with elevated PTEN expression. Along with the immune-system-associated cytotoxic mechanism, several mechanisms have been proposed for the effect of trastuzumab. PTEN activity might play an important and major role in its HER2/PI3K/Akt-mediated antitumour effect, and could be a useful biomarker for predicting the efficacy of trastuzumab in the treatment of breast cancer.

Phosphoinositide 3-kinase: from viral oncoprotein to drug target

The catalytic subunit p110alpha of the phosphoinositide 3-kinase (PI3K) and the serine-threonine protein kinase Akt have been extensively studied as retroviral oncoproteins. The experimental tools developed with the retroviral vectors are now being applied to PI3K mutations in human cancer. The most frequently occurring mutants of p110alpha are oncogenic in vitro and in vivo, show gain of enzymatic function, activate Akt, and their oncogenic activity is sensitive to rapamycin. The related isoforms p110beta, gamma and delta induce oncogenic transformation as wild-type proteins. Mutated p110alpha proteins are ideal drug targets. Identification of small molecule inhibitors that specifically target these mutant proteins is a realistic and urgent goal.

Synthesis and testing of a triaza-cyclopenta[b]phenanthrene scaffold as a DNA binding agent

A novel DNA binding agent based upon a triaza-cyclopenta[b]phenanthrene scaffold, compound 1, has been synthesized. dsDNA binding analysis of this compound using the ethidium bromide displacement assay indicated a preference for GC-rich sequences. However, equilibrium dialysis experiments against a variety of nucleic acids showed that the target compound bound about 20-fold tighter to G-quartet DNA than to dsDNA under physiological salt concentrations. The binding of 1 to G-quartet DNA was verified by the ability of the compound to promote the formation of the quartet and to compete with TmPyP4 for binding to the quadruplex. Given the importance of G-quartet binding agents in the treatment of cancer and in the understanding of drug-DNA interactions, 1 and its related analogs should find utility as a new class of G-quartet specific agents.

Inefficient proteasomal-degradation pathway stabilizes AP-2alpha and activates HER-2/neu gene in breast cancer

HER-2/neu proto-oncogene is overexpressed in about one fourth of human breast cancers. AP-2 transcription factors bind to the HER-2/neu gene promoter and activate its expression. In a striking concurrence, anomalous abundance of AP-2alpha protein or its homolog AP-2gamma is also detected with HER-2/neu protein in mammary tumor-derived cell lines. This suggests that the deregulation of AP-2 is the preceding pathogenic event and probably the pivotal one in this type of mammary carcinogenesis. We examined the process of AP-2alpha gene expression in mammary carcinoma cell lines to identify where the aberration had occurred. We found no amplification of the AP-2alpha gene. Its promoter was marginally upregulated; however, it did not significantly increase the mRNA levels. When the AP-2alpha protein was examined, a remarkable stability was seen in breast cancer cell lines MDA-MB-453 and SK-BR-3, with a half-life of over 30 hr. This is sharply higher than the approximate 1 hr observed in mammary epithelial cell line MCF-10A and murine cell line NIH 3T3. Treatment of MCF-10A and NIH 3T3 cells with the proteasome inhibitor MG-132 showed that AP-2alpha was ubiquitinated and its level significantly increased. Moreover, this increase was accompanied by elevated levels HER-2/neu protein. In contrast, weaker ubiquitination of AP-2alpha was seen in MDA-MB-453 and SK-BR-3 cancer cells, and MG-132 treatment did not raise the AP-2alpha level any further. These results uncover that unusual stability is the main mechanism that raises the levels of AP-2 proteins, and in addition, provide the first clue that defective ubiquitin-dependent proteasomal-degradation pathway is possibly the prime cause that affects the HER-2/neu gene and culminates in breast cancer.

Frequency and clinicopathologic correlates of ErbB1, ErbB2, and ErbB3 immunoreactivity in urothelial tumors of upper urinary tract

OBJECTIVES

To investigate the frequency and clinicopathologic correlates of ErbB1, ErbB2, and ErbB3 receptor expression in patients with upper urothelial carcinoma.

METHODS

Immunohistochemical staining for ErbB1, ErbB2, and ErbB3 was done with serial sections from archival specimens of 94 patients who underwent nephroureterectomy plus bladder cuff resection for urothelial carcinoma of the renal pelvis and ureter (median follow-up 40 months, range 1 to 177). The correlates between ErbB receptor expression and clinical outcome in terms of recurrence, progression, disease-free survival, and overall survival were analyzed by Kaplan-Meier plots, with the log-rank test and Cox proportional hazards model.

RESULTS

ErbB1, ErbB2, and ErbB3 expression was present in 9 (9.5%), 13 (13.8%), and 26 (27.7%) tumors, respectively. Thirty-seven patients (39.4 %) had at least one receptor expressed and eight (8.5%) had coexpression of two or three receptors. ErbB2 expression was significantly associated with tumor invasiveness (P = 0.03), and ErbB1 and ErbB3 expression was not. The incidence of subsequent tumor recurrence in the urinary bladder correlated significantly with ureteral tumor involvement and ErbB2 expression (P = 0.04 and P = 0.04, respectively). On univariate and multivariate analyses, tumor staging and ErbB2 expression were independent predictors of disease progression (P = 0.01 and P = 0.01, respectively), disease-free survival (P = 0.02 and P = 0.002, respectively), and overall survival (P = 0.01 and P = 0.02, respectively).

CONCLUSIONS

ErbB2 expression predicts for disease progression and disease-related survival in upper urothelial carcinoma.

Effect of gamma-linolenic acid on the transcriptional activity of the Her-2/neu (erbB-2) oncogene

The omega-6 polyunsaturated fatty acid gamma-linolenic acid (GLA; 18:3n-6), which is found in several plant oils and is used as an herbal medicine, has antitumor activity in vitro. We examined the effect of GLA on the expression of the Her-2/neu (erbB-2) oncogene, which is involved in development of numerous types of human cancer. Flow cytometric and immunoblotting analyses demonstrated that GLA treatment substantially reduced Her-2/neu protein levels in the Her-2/neu-overexpressing cell lines BT-474, SK-Br3, and MDA-MB-453 (breast cancer), SK-OV3 (ovarian cancer), and NCI-N87 (gastrointestinal tumor derived). GLA exposure led to a dramatic decrease in Her-2/neu promoter activity and a concomitant increase in the levels of polyomavirus enhancer activator 3 (PEA3), a transcriptional repressor of Her-2/neu, in these cell lines. In transient transfection experiments, a Her-2/neu promoter bearing a PEA3 site-mutated sequence was not subject to negative regulation by GLA in Her-2/neu-overexpressing cell lines. Concurrent treatments of Her-2/neu-overexpressing cancer cells with GLA and the anti-Her-2/neu antibody trastuzumab led to synergistic increases in apoptosis and reduced growth and colony formation.

Viruses – seeking and destroying the tumor program

DNA viruses have enormous utility in cancer research, both as tools for tumor target discovery as well as agents for lytic cancer therapies. This is because there is a profound functional overlap between the DNA viral and tumor cell programs. DNA viruses encode proteins that elicit growth deregulation in infected cells similar to that engendered by mutations in tumor cells. Evolution has refined viral proteins to target the critical cellular hubs that regulate growth. Thus, viral proteins are discriminating biochemical probes that can be used to identify and characterize novel tumor targets. Moreover, the overlap between the DNA viral and tumor programs can also be exploited for the development of lytic cancer therapies. Discovering whether tumor cells selectively complement the replication of viral mutants can reveal novel oncolytic viral therapies, as well as unexpected tumor properties. For example, altered RNA export was recently uncovered as a novel tumor cell property that underlies ONYX-015 replication, a promising oncolytic adenoviral therapy. A perspective is provided on how adenovirus could be systematically exploited to map the requisite role, or indeed the redundancy, of cellular pathways that act in an integrated program to elicit pathological replication. This knowledge has important applications for the rational design of the next generation of oncolytic viruses, as well as the discovery of efficacious combination cancer therapies.

The Akt/PKB pathway: molecular target for cancer drug discovery

The serine/threonine kinase Akt/PKB pathway presents an exciting new target for molecular therapeutics, as it functions as a cardinal nodal point for transducing extracellular (growth factor and insulin) and intracellular (receptor tyrosine kinases, Ras and Src) oncogenic signals. In addition, alterations of the Akt pathway have been detected in a number of human malignancies. Ectopic expression of Akt, especially constitutively activated Akt, is sufficient to induce oncogenic transformation of cells and tumor formation in transgenic mice as well as chemoresistance. Akt has a wide range of downstream targets that regulate tumor-associated cell processes such as cell growth, cell cycle progression, survival, migration, epithelial-mesenchymal transition and angiogenesis. Blockage of Akt signaling results in apoptosis and growth inhibition of tumor cells with elevated Akt. The observed dependence of certain tumors on Akt signaling for survival and growth has wide implications for cancer therapy, offering the potential for preferential tumor cell killing. In the last several years, through combinatorial chemistry, high-throughput and virtual screening, and traditional medicinal chemistry, a number of inhibitors of the Akt pathway have been identified. This review focuses on ongoing translational efforts to therapeutically target the Akt pathway.

AKT activation predicts outcome in breast cancer patients treated with tamoxifen

Oestrogen receptor (ERalpha) expression is a strong predictor of response to endocrine therapy. The PI3K/AKT/mTOR signal transduction pathway has been implicated in endocrine resistance in vitro. The present study was carried out to test the hypothesis that AKT activation mediates tamoxifen resistance in clinical breast cancer. Immunohistochemistry (IHC) using AKT1-3, pan-AKT, pAKT (Thr-308), pAKT (Ser-473), pER (Ser-167), and pHER2 antibodies was performed on 402 ERalpha-positive breast carcinomas from patients treated with tamoxifen. High pAKT (Ser-473) activity (p = 0.0406) and low AKT2 expression (p = 0.0115) alone, or in combination [high pAKT (Ser-473)/low AKT2; 'high-risk' patient group] (p = 0.0014), predicted decreased overall survival in tamoxifen-treated patients with ERalpha-positive breast cancers. There was no significant association between tumour levels of AKT expression or activity and disease-free survival (DFS); however, the 'high-risk' patient group was significantly more likely to relapse (p = 0.0491). During tamoxifen treatment, neither AKT2 nor pAKT predicted DFS. Finally, activation of AKT, via phosphorylation, was linked to activation of both HER2 and ERalpha in this patient cohort. The data presented here show that the PI3K/AKT/mTOR pathway is associated with relapse and death in ERalpha-positive breast cancer patients treated with tamoxifen, supporting in vitro evidence that AKT mediates tamoxifen resistance. Patients with a 'high-risk' expression profile were at increased risk of death (hazard ratio 3.22, p = 0.002) relative to 'low-risk' patients, highlighting the potential that tumour profiling, with multiple IHC markers predictive of therapeutic response, may improve patient selection for endocrine therapies, eg tamoxifen or aromatase inhibitor-based treatments.

Activity of suberoylanilide hydroxamic Acid against human breast cancer cells with amplification of her-2

PURPOSE

We determined the effects of suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, on hsp90 and its client proteins Her-2, AKT, and c-Raf, as well as evaluated the cytotoxic effects of co-treatment of SAHA with trastuzumab or docetaxel in human breast cancer BT-474 and SKBR-3 cells containing amplification of Her-2.

EXPERIMENTAL DESIGN

The cells were treated with SAHA (1.0-5.0 micromol/L) and/or trastuzumab (5-40 microg/mL) or docetaxel (5-20 nmol/L). Following this, apoptosis and the levels of p21(WAF1), p27(KIP1), AKT, c-Raf, and Her-2, as well as of the key regulators of apoptosis were determined. Synergistic interaction between drugs was evaluated by median dose-effect analysis.

RESULTS

Treatment with SAHA up-regulated p21(WAF1) and p27(KIP1) levels, increased the percentage of cells in G2-M phase of the cell cycle, as well as induced apoptosis in a dose-dependent manner. This was associated with up-regulation of the pro-death Bak and Bim, as well as with attenuation of the levels of Her-2 and XIAP, survivin, Bcl-2, and Bcl-x(L) proteins. SAHA treatment induced acetylation of hsp90. This reduced the chaperone association of Her-2 with hsp90, promoting polyubiquitylation and degradation of Her-2. SAHA also attenuated the levels of c-Raf and AKT. Co-treatment with SAHA significantly increased trastuzumab or docetaxel-induced apoptosis of BT-474 and SKBR-3 cells. Additionally, median dose-effect analysis revealed that co-treatment with SAHA and trastuzumab or docetaxel induced synergistic cytotoxic effects against the breast cancer cells.

CONCLUSIONS

These preclinical findings support the development of SAHA in combination with docetaxel and/or trastuzumab against Her-2-amplified breast cancer.

Cancer-specific gene therapy

Cancer cells transcriptionally activate many genes that are important for uncontrolled proliferation and cell death. Deregulated transcriptional machinery in tumor cells usually consists of increased expression/activity of transcription factors. Ideally, cancer-specific killing can be achieved by delivering a therapeutic gene under the control of the DNA elements that can be activated by transcription factors that are overexpressed and/or constitutively activated in cancer cells. Additionally, tumor-specific translation of tumor-killing genes has been also exploited in cancer gene therapy. Based on these rationales, cancer-specific expression of a therapeutic gene has emerged as a potentially successful approach for cancer gene therapy. To achieve tumor-specific expression, cancer-specific vectors are generally composed of promoters, enhancers, and/or 5'-UTR that are responsive to tumor-specific transcription factors. A number of cancer-specific promoters have been reported, such as those of probasin, human telomerase reverse transcriptase, survivin, ceruloplasmin, HER-2, osteocalcin, and carcinoembryonic antigen. Evidences suggest that the enhancer element targeted by beta-catenin can be useful to target colon cancer cells. The 5'-UTR of the basic fibroblast growth factor-2 has been reported to provide tumor specificity. Moreover, a variety of therapeutic genes demonstrated direct antitumor effects such as those encoding proapoptotic proteins p53, E1A, p202, PEA3, BAX, Bik, and prodrug metabolizing enzymes, namely thymidine kinase and cytosine deaminase. As cancerous cells of different origins vary significantly in their genetic, transcriptional/translational, and cellular profiles, the success of a cancer gene therapy will not be promised unless it is carefully designed based on the biology of a specific tumor type. Thus, tremendous research efforts have been focused on the development of non-viral vectors that selectively target various tumors resulting in minimal toxicity in the normal tissues. Significant progresses were also made in the exploitation of various novel apoptotic, cytotoxic genes as therapeutic tools that suppress the growth of different tumors. Together, these recent advances provide rationales for future clinical testing of transcriptionally targeted non-viral vectors in cancer patients.