Proliferation, cell cycle and apoptosis in cancer

Dynamic expression profile of p21WAF1/CIP1 and Ki-67 predicts survival in rectal carcinoma treated with preoperative radiochemotherapy

PURPOSE

We investigated p53 and its downstream effectors p21WAF1/CIP1, BAX, and hMSH2 as well as the proliferation marker Ki-67 (mki-67/MIB-1) in patients undergoing preoperative radiochemotherapy for rectal carcinoma to identify prognostic and predictive factors. The focus of this study was on the dynamics of these genetic markers in a longitudinal study-that is, before and after radiochemotherapy.

PATIENTS AND METHODS

Expression of p53, BAX, p21WAF1/CIP1, Ki-67, and hMSH2 was investigated by immunohistochemistry in pre- and posttherapeutic tumor samples in 66 patients. Tumor DNA was screened for p53 mutations by single-strand conformation polymorphism-polymerase chain reaction (SSCP-PCR). Paired tumor samples (pretherapy and posttherapy) were collected prospectively.

RESULTS

Patients with a decrease in p21 expression following radiochemotherapy had better disease-free survival (P =.03). Similarly, patients with an increase in proliferative activity as measured by increased Ki-67 expression posttherapy had better disease-free survival (P <.005). In addition, we observed a significantly better prognosis for patients with high hMSH2 expression. In contrast, pretherapeutic levels of p53, BAX, or p21 expression and p53 mutation had no prognostic value, indicating that the combination of radiotherapy and chemotherapy might override defects in these genes.

CONCLUSION

These findings are novel and support the clinical relevance of p21 in the suppression of both proliferation and apoptosis. Thus, the dynamic induction of p21WAF1/CIP1 was associated with a lower proliferative activity but an ultimately worse treatment outcome following neoadjuvant radiochemotherapy and tumor resection. Induction of p21, therefore, represents a novel resistance mechanism in rectal cancer undergoing preoperative radiochemotherapy.

Quantitative tumor apoptosis imaging using technetium-99m-HYNIC annexin V single photon emission computed tomography

PURPOSE

Radiolabeled annexin V may allow for repetitive and selective in vivo identification of apoptotic cell death without the need for invasive biopsy. This study reports on the relationship between quantitative technetium-99m- (99mTc-) 6-hydrazinonicotinic (HYNIC) radiolabeled annexin V tumor uptake, and the number of tumor apoptotic cells derived from histologic analysis.

PATIENTS AND METHODS

Twenty patients (18 men, two women) suspected of primary (n = 19) or recurrent (n = 1) head and neck carcinoma were included. All patients underwent a spiral computed tomography (CT) scan, 99mTc-HYNIC annexin V tomography, and subsequent surgical resection of the suspected primary or recurrent tumor. Quantitative 99mTc-HYNIC annexin V uptake in tumor lesions divided by the tumor volume, derived from CT, was related to the number of apoptotic cells per tumor high-power field derived from terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling (TUNEL) assays performed on sectioned tumor slices.

RESULTS

Diagnosis was primary head and neck tumor in 18 patients, lymph node involvement of a cancer of unknown primary origin in one patient, and the absence of recurrence in one patient. Mean percentage absolute tumor uptake of the injected dose per cubic centimeter tumor volume derived from tomographic images was 0.0003% (standard deviation [SD], 0.0004%) at 1 hour postinjection (PI) and 0.0001% (SD, 0.0000%) at 5 to 6 hours PI (P =.012). Quantitative 99mTc-HYNIC annexin V tumor uptake correlated well with the number of apoptotic cells if only tumor samples with no or minimal amounts of necrosis were considered.

CONCLUSION

In the absence of necrosis, absolute 99mTc-HYNIC annexin V tumor uptake values correlate well with the number of apoptotic cells derived from TUNEL assays.

Prognostic factors and pathology of advanced gastric cancer

AIM

To investigate the prognostic factors and the relationship between clinicopathologic parameters and biological properties in advanced gastric cancer.

METHODS

In tumor samples from 61 primary advanced gastric cancer patients with curative resection, following parameters of sex, age, tumor size, grade of differentiation, depth of invasion, lymph node metastasis, lymphatics invasion and TNM stage were evaluated. In addition, DCs infiltration, PCNA-LI and AI were examined by TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate biotin nick end labeling) or immunohistochemical methods. The prognostic impact of these parameters was analyzed by univariate and multivariate survival analysis.

RESULTS

PCNA-LI, AI and DCs infiltration were significantly correlated to lymph node metastasis, TNM stage and differentiation grade. Univariate Kaplan-Meier analysis showed that depth of invasion, lymph node metastasis, TNM stage, PCNA-LI and infiltration of DCs had prognostic significances for survial (Log-rank test, P <0.05), while multivariate Cox analysis indicated that only tumor size (RR=2.328) and TNM stage (RR =5.251) were independent prognostic factors for survival.

CONCLUSION

In advanced gastric cancer, UICC TNM stage and tumor size are independent prognostic factors, and infiltration of DCs and proliferation of cancer cells play a role in the prognostic outcome.

Reactive oxygen species generation and mitochondrial dysfunction in the apoptotic response to Bortezomib, a novel proteasome inhibitor, in human H460 non-small cell lung cancer cells

Bortezomib, a proteasome inhibitor, shows substantial anti-tumor activity in a variety of tumor cell lines, is in phase I, II, and III clinical trials and has recently been approved for the treatment of patients with multiple myeloma. The sequence of events leading to apoptosis following proteasome inhibition by bortezomib is unclear. Bortezomib effects on components of the mitochondrial apoptotic pathway were examined: generation of reactive oxygen species (ROS), alteration in the mitochondrial membrane potential (Delta psi m), and release of cytochrome c from mitochondria. With human H460 lung cancer cells, bortezomib exposure at 0.1 microM showed induction of apoptotic cell death starting at 24 h, with increasing effects after 48-72 h of treatment. After 3-6 h, an elevation in ROS generation, an increase in Delta psi m, and the release of cytochrome c into the cytosol, were observed in a time-dependent manner. Co-incubation with rotenone and antimycin A, inhibitors of mitochondrial electron transport chain complexes I and III, or with cyclosporine A, an inhibitor of mitochondrial permeability transition pore, resulted in inhibition of bortezomib-induced ROS generation, increase in Delta psi m, and cytochrome c release. Tiron, an antioxidant agent, blocked the bortezomib-induced ROS production, Delta psi m increase, and cytochrome c release. Tiron treatment also protected against the bortezomib-induced PARP protein cleavage and cell death. Benzyloxycarbonyl-VAD-fluoromethyl ketone, an inhibitor of pan-caspase, did not alter the bortezomib-induced ROS generation and increase in Delta psi m, although it prevented bortezomib-induced poly(ADP-ribose) polymerase cleavage and apoptotic death. In PC-3 prostate carcinoma cells (with overexpression of Bcl-2), a reduction of bortezomib-induced ROS generation, Delta psi m increase was correlated with cellular resistance to bortezomib and the attenuation of drug-induced apoptosis. The transient transfection of wild type p53 in p53 null H358 cells caused stimulation of the bortezomib-induced apoptosis but failed to enhance ROS generation and Delta psi m increase. Thus ROS generation plays a critical role in the initiation of the bortezomib-induced apoptotic cascade by mediation of the disruption of Delta psi m and the release of cytochrome c from mitochondria.

siRNA targeting of the viral E6 oncogene efficiently kills human papillomavirus-positive cancer cells

The targeted inhibition of antiapoptotic factors in tumour cells may provide a rational approach towards the development of novel anticancer therapies. Using human papillomavirus (HPV)-transformed cells as a model system, we investigated if RNA interference (RNAi)-mediated gene silencing can be employed in order to overcome the apoptosis resistance of cancer cells. We found that both vector-borne and synthetic small interfering (si)RNAs, specifically directed against the antiapoptotic HPV E6 oncogene, restored dormant tumour suppressor pathways in HPV-positive cancer cells that are otherwise inactive in the presence of E6. This ultimately resulted in massive apoptotic cell death, selectively in HPV-positive tumour cells. These findings show that RNAi provides a powerful molecular strategy to inactivate intracellular E6 function efficiently. Moreover, they define E6 as a most promising therapeutic target to eliminate HPV-positive tumour cells specifically by RNAi. Thus, by sequence-specific targeting of antiapoptotic genes, siRNAs may be developed into novel therapeutics that can efficiently correct the apoptosis deficiency of cancer cells.

Apoptosis-an introduction

Apoptosis has become a major research area in the biomedical sciences. As there are more than 13,000 papers published annually on the topic, it is impossible to keep track on all developments in the area. The individual aspects of molecular control of apoptosis are well reviewed, but more general, introductory recent reviews into the field are lacking. This review aims to give a brief overview of the field, providing an introduction into the literature for students and newcomers; as it is written for the un-initiated, wherever possible, review articles will be cited rather than original papers.

Defective double-strand DNA break repair and chromosomal translocations by MYC overexpression

DNA repair mechanisms are essential for the maintenance of genomic integrity. Disruption of gene products responsible for DNA repair can result in chromosomal damage. Improperly repaired chromosomal damage can result in the loss of chromosomes or the generation of chromosomal deletions or translocations, which can lead to tumorigenesis. The MYC protooncogene is a transcription factor whose overexpression is frequently associated with human neoplasia. MYC has not been previously implicated in a role in DNA repair. Here we report that the overexpression of MYC disrupts the repair of double-strand DNA breaks, resulting in a several-magnitude increase in chromosomal breaks and translocations. We found that MYC inhibited the repair of gamma irradiation DNA breaks in normal human cells and blocked the repair of a single double-strand break engineered to occur in an immortal cell line. By spectral karyotypic analysis, we found that MYC even within one cell division cycle resulted in a several-magnitude increase in the frequency of chromosomal breaks and translocations in normal human cells. Hence, MYC overexpression may be a previously undescribed example of a dominant mutator that may fuel tumorigenesis by inducing chromosomal damage.

The 15-lipoxygenase-1 product 13-S-hydroxyoctadecadienoic acid down-regulates PPAR-delta to induce apoptosis in colorectal cancer cells

Diminished apoptosis, a critical event in tumorigenesis, is linked to down-regulated 15-lipoxygenase-1 (15-LOX-1) expression in colorectal cancer cells. 13-S-hydroxyoctadecadienoic acid (13-S-HODE), which is the primary product of 15-LOX-1 metabolism of linoleic acid, restores apoptosis. Nonsteroidal antiinflammatory drugs (NSAIDs) transcriptionally up-regulate 15-LOX-1 expression to induce apoptosis. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors for linoleic and arachidonic acid metabolites. PPAR-delta promotes colonic tumorigenesis. NSAIDs suppress PPAR-delta activity in colon cancer cells. The mechanistic relationship between 15-LOX-1 and PPAR-delta was previously unknown. Our current study shows that (i) 13-S-HODE binds to PPAR-delta, decreases PPAR-delta activation, and down-regulates PPAR-delta expression in colorectal cancer cells; (ii) the induction of 15-LOX-1 expression is a critical step in NSAID down-regulation of PPAR-delta and the resultant induction of apoptosis; and (iii) PPAR-delta is an important signaling receptor for 13-S-HODE-induced apoptosis. The in vivo relevance of these mechanistic findings was demonstrated in our tumorigenesis studies in nude mouse xenograft models. Our findings indicate that the down-regulation of PPAR-delta by 15-LOX-1 through 13-S-HODE is an apoptotic signaling pathway that is activated by NSAIDs.

The Cdk inhibitor p21 is required for necrosis, but it inhibits apoptosis following toxin-induced liver injury

Liver injury and repair were examined in wild type, p21Waf1/Cip1, and p27Kip1-deficient mice following carbon tetrachloride (CCl4) administration. In wild type liver, p21 expression is induced in a biphasic manner following injection of CCl4, with an early peak of p21 expression occurring in pericentral hepatocytes at 6 h, prior to evidence of injury, and a second peak succeeding regenerative proliferation. In contrast, p27 is present throughout the quiescent liver, but its expression decreases following CCl4 injection. Surprisingly, p21-deficient animals were resistant to CCl4-induced necrotic injury, indicating that rapid induction of p21 in pericentral hepatocytes following CCl4 injection contributes to subsequent necrosis. Expression of cytochrome P450 2E1, which plays an essential role in CCl4-induced necrotic injury, was not affected in p21-deficient mice. Although they had the least injury, p21-deficient mice had the highest levels of hepatic proliferation that correlated with increases in hyperphosphorylated retinoblastoma protein and Cyclin A gene expression. Increased replication in p21-deficient livers was counteracted by an increase in hepatocyte apoptosis as detected by caspase-3 activation. p21 plays distinct and opposing roles regulating hepatocyte survival during injury and subsequent repair, with early induction of p21 contributing to necrotic injury and later expression to cessation of proliferation and hepatocyte survival.

p21WAF1/CIP1 is more effective than p53 in growth suppression of mouse renal carcinoma cell line Renca in vitro and in vivo

PURPOSE

Although there are many controversial reports about the effect of p53 and p21(WAF1/CIP1) overexpression in different human tumor cells, the p53 gene is shown to be a more effective candidate for cancer gene therapy because of its more pronounced ability to induce apoptosis. In the present study, we present the effect of p53 and p21(WAF1/CIP1) overexpression on mouse renal carcinoma cells in vitro and in vivo.

METHODS

p53 and p21(WAF1/CIP1) genes were introduced into Renca cells using adenoviral vectors (Ad5CMV-p53 and Ad5CMV-p21). The induction of apoptosis was measured using Annexin V assay and DNA fragmentation analysis. The expression of proteins was examined using immunocytochemistry and Western blot methods. The ability of adenoviral vectors to inhibit tumorigenicity of Renca cells, as well as the growth of pre-established tumors was measured.

RESULTS

In vitro growth assays revealed higher growth suppression after Ad5CMV-p21 infection. Although both vectors induced apoptosis, Ad5CMV-p53 was slightly more efficient. In vivo studies in Balb/c mice, demonstrated that tumorigenicity was completely suppressed by Ad5CMV-p21. Besides this, Ad5CMV-p21 significantly inhibited the growth of established tumors, while Ad5CMV-p53 did not.

CONCLUSIONS

These data suggest that p21(WAF1/CIP1) is a more potent growth suppressor than p53 of mouse tumor cells Renca. The divergent responses of tumor cells to p21(WAF1/CIP1) overexpression could be due to various networks that differ between species.

RAL GTPases are linchpin modulators of human tumour-cell proliferation and survival

The monomeric RAL (RAS-like) GTPases have been indirectly implicated in mitogenic regulation and cell transformation. Here, we show that RALA and RALB collaborate to maintain tumorigenicity through regulation of both proliferation and survival. Remarkably, this task is divided between these highly homologous isoforms. RALB is specifically required for survival of tumour cells but not normal cells. RALA is dispensable for survival, but is required for anchorage-independent proliferation. Reducing the 'oncogenic burden' in human tumour cells relieves the sensitivity to loss of RALB. These observations establish RAL GTPases as crucial components of the cellular machinery that are exploited by factors that drive oncogenic transformation.

Differential effects of cell cycle regulatory protein p21(WAF1/Cip1) on apoptosis and sensitivity to cancer chemotherapy

p21(WAF1/Cip1) was initially identified as a cell cycle regulatory protein that can cause cell cycle arrest. It is induced by both p53-dependent and p53-independent mechanisms. This mini-review briefly discusses its currently known functions in apoptosis and drug sensitivity. As an inhibitor of cell proliferation, p21(WAF1/Cip1) plays an important role in drug-induced tumor suppression. Nevertheless, a number of recent studies have shown that p21(WAF1/Cip1) can assume both pro- or anti-apoptotic functions in response to anti-tumor agents depending on cell type and cellular context. This dual role of p21(WAF1/Cip1) in cancer cells complicates using p21(WAF1/Cip1) status to predict response to anti-tumor agents. However, it is possible to develop p21(WAF1/Cip1)-targeted reagents or p21(WAF1/Cip1) gene transfer techniques to have a beneficial effect within a well-defined therapeutic context. Better understanding of the roles of p21(WAF1/Cip1) in tumors should enable a more rational approach to anti-tumor drug design and therapy.

Neoplastic development in plasma cells

An increasing number of model systems of plasma cell tumor (PCT) formation have been and are being developed. Discussed here are six models in mice and multiple myeloma (MM) in humans. Each model illustrates a unique set of biological factors. There are two general types of model systems: those that depend upon naturally arising mutagenic changes (pristane-induced PCTs, 5TMM, and MM) and those that are associated with oncogenes (Emu-v-abl), growth factors [interleukin-6 (IL-6)], and anti-apoptotic factors (Bcl-xL/Bcl-2). PCTs develop in several special tissue microenvironments that provide essential cytokines (IL-6) and cell-cell interactions. In mice, the activation and deregulation of c-myc by chromosomal translocations is a major feature in many of the models. This mechanism is much less a factor in MM and the 5T model in mice. Genetically determined susceptibility is involved in many of the mouse models, but only a few genes have been implicated thus far.

Prolactin induces ERalpha-positive and ERalpha-negative mammary cancer in transgenic mice

The role of prolactin in human breast cancer has been controversial. However, it is now apparent that human mammary epithelial cells can synthesize prolactin endogenously, permitting autocrine/paracrine actions within the mammary gland that are independent of pituitary prolactin. To model this local mammary production of prolactin (PRL), we have generated mice that overexpress prolactin within mammary epithelial cells under the control of a hormonally nonresponsive promoter, neu-related lipocalin (NRL). In each of the two examined NRL-PRL transgenic mouse lineages, female virgin mice display mammary developmental abnormalities, mammary intraepithelial neoplasias, and invasive neoplasms. Prolactin increases proliferation in morphologically normal alveoli and ducts, as well as in lesions. The tumors are of varied histotype, but papillary adenocarcinomas and adenosquamous neoplasms predominate. Neoplasms can be separated into two populations: one is estrogen receptor alpha (ERalpha) positive (greater than 15% of the cells stain for ERalpha), and the other is ERalpha- (<3%). ERalpha expression does not correlate with tumor histotype, or proliferative or apoptotic indices. These studies provide a mouse model of hormonally dependent breast cancer, and, perhaps most strikingly, a model in which some neoplasms retain ERalpha, as occurs in the human disease.

Characterization of mutations and loss of heterozygosity of p53 and K-ras2 in pancreatic cancer cell lines by immobilized polymerase chain reaction

BACKGROUND

The identification of known mutations in a cell population is important for clinical applications and basic cancer research. In this work an immobilized form of the polymerase chain reaction, referred to as polony technology, was used to detect mutations as well as gene deletions, resulting in loss of heterozygosity (LOH), in cancer cell lines. Specifically, the mutational hotspots in p53, namely codons 175, 245, 248, 249, 273, and 282, and K-ras2, codons 12, 13 and 61, were genotyped in the pancreatic cell line, Panc-1. In addition LOH analysis was also performed for these same two genes in Panc-1 by quantifying the relative gene copy number of p53 and K-ras2.

RESULTS

Using polony technology, Panc-1 was determined to possess only one copy of p53, which possessed a mutation in codon 273, and two copies of K-ras2, one wildtype and one with a mutation in codon 12. To further demonstrate the general approach of this method, polonies were also used to detect K-ras2 mutations in the pancreatic cell lines, AsPc-1 and CAPAN-1.

CONCLUSIONS

In conclusion, we have developed an assay that can detect mutations in hotspots of p53 and K-ras2 as well as diagnose LOH in these same genes.

The N-myc paradox: N-myc overexpression in neuroblastomas is associated with sensitivity as well as resistance to apoptosis

Neuroblastomas are characterized by defects in tumor necrosis factor-related apoptosis inducing ligand (TRAIL) induced apoptosis, especially down-regulation and methylation of Caspase-8 (CASP8). This defect is associated with amplification of N-myc. However, N-myc has also been implicated in induction of apoptosis, especially activation of CASP9 mediated apoptosis. Here we found that ectopic N-myc expression induces TRAIL susceptibility, both by CASP8 and CASP9 mediated apoptosis. N-myc did not modify CASP8 expression and methylation. CASP8 defects therefore represent an independent event in neuroblastoma, counteracting the N-myc induced susceptibility to apoptosis. Analysis of the CASP9 mediated route in a series of neuroblastoma cell lines, we found normal expression and no aberrant methylation of four apoptotic intermediates, including CASP9 itself.

The requirement for evasion of programmed cell death in neuroblastomas with MYCN amplification

Neuroblastoma is a tumour of the peripheral nervous system that accounts for 15% of cancer-related deaths in childhood. Amplification and overexpression of the MYCN proto-oncogene occurs in 25% of neuroblastomas and is highly correlated with treatment failure and mortality. MYCN stimulates cell cycle entry but does not alleviate the requirement for ongoing mitogenic signalling to support this proliferation. In fact, deregulated MYCN potently heightens cell sensitivity to myriad stressors that induce programmed cell death, although the mechanisms of this effect are poorly understood. To circumvent this safeguard against oncogene-driven neoplasia, cancer cells with deregulated MYC frequently exhibit defects in apoptotic pathways. It is similarly proposed that neuroblasts with MYCN amplification have obligate defects in pathways that engage or execute apoptosis, and these defects contribute to the malignant phenotype. Investigations into the molecular genetics of both primary human neuroblastomas with MYCN amplification, as well as tumours arising in genetically engineered mice with targeted MYCN overexpression, should help to define these cooperating genetic lesions. Elucidating the mechanisms whereby non-transformed neural cells engage MYCN-primed apoptosis, as well as the mechanisms neuroblasts with MYCN amplification use to evade this process, will define useful targets for biological therapeutics that exploit the inherent apoptosis-priming function of deregulated MYCN.

Immune responses in cancer

The complex of humoral factors and immune cells comprises two interleaved systems, innate and acquired. Immune cells scan the occurrence of any molecule that it considers to be nonself. Transformed cells acquire antigenicity that is recognized as nonself. A specific immune response is generated that results in the proliferation of antigen-specific lymphocytes. Immunity is acquired when antibodies and T-cell receptors are expressed and up-regulated through the formation and release of lymphokines, chemokines, and cytokines. Both innate and acquired immune systems interact to initiate antigenic responses against carcinomas. A new approach to the treatment of cancer has been immunotherapy, which aims to up-regulate the immune system in order that it may better control carcinogenesis. Currently, several forms of immunotherapy that use natural biological substances to activate the immune system are being explored therapeutically. The various forms of immunotherapy fall into three main categories: monoclonal antibodies, immune response modifiers, and vaccines. While these modalities have individually shown some promise, it is likely that the best strategy to combat cancer may require multiple immunotherapeutic strategies in order to demonstrate benefit in different patient populations. It may be that the best results are obtained with vaccines in combination with a variety of immunotherapy combinations. Another potent strategy may be in combining with more traditional cancer drugs as evidenced from the benefit derived from enhancing the efficacy of chemotherapy with cytokines. Through such concerted efforts, a durable, therapeutic antitumour immune response may be achieved and maintained over the course of a patient's lifespan.

Clinical applications of proteomics

Proteomics, the systematic evaluation of changes in the protein constituency of a cell, is more than just the generation of lists of proteins that increase or decrease in expression as a cause or consequence of disease. The ultimate goal is to characterize the information flow through protein pathways that interconnect the extracellular microenvironment with the control of gene transcription. The nature of this information can be a cause or a consequence of disease processes. Clinical applications of proteomics involve the use of proteomic technologies at the bedside. The analysis of human cancer as a model for how proteomics can have an impact at the bedside is now employing several new proteomic technologies that are being developed for early detection, therapeutic targeting and finally, patient-tailored therapy.

Ovarian cancer: strategies for overcoming resistance to chemotherapy

Ovarian cancer is responsible for 4% of deaths from cancer in women. Treatment comprises a combination of surgery and chemotherapy, but patients typically experience disease relapse within 2 years of the initial treatment. Further treatment can extend survival, although relapse eventually occurs again. A better understanding of the mechanisms that underlie this drug resistance should allow treatment to be optimized, so that substantial improvements in the outlook for women with this disease can be achieved.

Pharmacogenomics in cancer drug discovery and development: inhibitors of the Hsp90 molecular chaperone

Drug discovery is being revolutionised by a number of technological developments. These include high throughput screening, combinatorial chemistry and genomics. The impact of the new technologies is to accelerate the pace of anticancer discovery. The completion of the Human Genome Project and the ongoing high throughput sequencing of cancer genomes will facilitate the identification of a range of new molecular targets for drug discovery. Over the next few years we will have a complete molecular understanding of the various combinations of genes and cognate pathways that drive the malignant phenotype and tumour progression. The vision for postgenomic cancer drug discovery must be to identify therapeutic agents that correct or exploit each of these molecular abnormalities. In this way, it will be possible to develop personalised drug combinations that are targeted to the molecular make up of individual tumours. It is anticipated that these therapies will be more effective and less toxic than current approaches, although combinations of novel agents with existing cytotoxic therapies are likely to continue for some time. Examples of postgenomic, mechanism-based drugs include Glivec, Herceptin and Iressa, with many more agents undergoing preclinical and clinical development. An interesting new approach involves the development of inhibitors of heat shock protein (Hsp90) molecular chaperone. Because Hsp90 is required for the correct folding, stability and function of a range of oncoproteins that are mutated or over expressed in cancer, Hsp90 inhibitors have the potential to provide a simultaneous, combinatorial attack on multiple oncogenic pathways. By depleting the levels of multiple oncoproteins in cancer cells and blocking a wide range of oncogenic pathways, Hsp90 inhibitors have the potential to inhibit all of the hallmark characteristics of cancer cells. Progress in the preclinical and clinical development of Hsp90 inhibitors will be described, including an update on clinical studies with the first-in-class agent 17AAG. The use of the postgenomic technology of gene expression microarrays in cancer pharmacology and drug development will be exemplified.

Cell-cycle responses to DNA damage in G2

Cellular reproduction, at its basic level, is simply the passing of genetic information from a single parent cell into two daughter cells. As the cellular genome encodes all the information that defines a cell, it is crucial that the genome be accurately replicated. Furthermore, the duplicated genome must be properly segregated so that each daughter cell contains the exact same information as the parent cell. The processes by which this occurs is known as the cell cycle. The failure of either duplication or segregation of the genome can have disastrous consequences for an organism, including cancer and death. This article discusses what is known about checkpoints, the surveillance mechanisms that monitor both the fidelity and accuracy of DNA replication and segregation. Specifically, we will focus on the G2 checkpoint that is responsible for ensuring proper segregation of the duplicated genome into the daughter cells and how this checkpoint functions to arrest entry into mitosis in response to DNA damage.

Formation of an active form of the interleukin-2/15 receptor beta-chain by insertion of the intracisternal A particle in a radiation-induced mouse thymic lymphoma and its role in tumorigenesis

Although many reports suggest that aberrant regulation of cytokine signaling pathways via the interleukin-2 receptor (IL-2R) induces tumorigenic transformation, constitutively active IL-2R in tumors has not been reported. We searched for genomic alteration of the IL-2/15R beta-subunit gene (IL-2/15R beta) in cytokine-independent cell lines established from radiation-induced mouse thymic lymphomas. In the TL34 cell line and its primary tumor, one of the IL-2/15R beta alleles was rearranged by the insertion of an intracisternal A particle (IAP) retrotransposon. The IAP-IL2/15R beta chimeric gene expressed chimeric mRNA in which IAP-coding Gag-Pol mRNA was fused to IL-2/15R beta mRNA and coded for Gag-Pol-IL-2/15R beta chimeric protein. Forced expression of the Gag-Pol-IL-2/15R beta chimeric cDNA in a mouse cytotoxic T-cell line (CTLL-2) converted IL-2-dependent cell growth to IL-2-independent growth, suggesting that the chimeric protein activates some of the IL-2 signaling pathways necessary for cell proliferation. Downregulation of the expression of the Gag-Pol-IL-2/15R beta chimeric protein in TL34 by antisense RNA inhibited cell growth, and concomitantly reduced the level of c-myc protein. These results suggest that the Gag-Pol-IL-2/15R beta is a constitutively active form that transmits proliferative signals by expressing downstream target genes, including c-myc. Thus, we demonstrated that the chimeric receptor gene produced by the insertion of an IAP functions as an oncogene by providing IL-2-independent autonomous growth potential.

Recent advances in understanding apoptosis: new therapeutic opportunities in cancer chemotherapy

Major advances have been made in our understanding of the regulation of the molecular machinery of apoptosis in vitro. Molecules linking proliferation and apoptosis in healthy cells are being identified and here apoptotic cell death provides the 'fail-safe' mechanism to counteract excess proliferation. More recently, pioneering work on the regulation of apoptosis, in animal models of tumour development, has shown that suppression of apoptosis in the presence of a proliferative stimulus is sufficient for tumour development. Progress has also been made towards clarifying the contribution of drug-induced apoptosis to tumour response. With increasing evidence that failure to engage apoptosis after drug treatment contributes to drug resistance in vivo comes renewed confidence that new therapeutic approaches based on drug targets in apoptotic pathways will improve the treatment of cancer patients. As ever, tumour specificity is the major issue to be resolved.

Genome-wide comparison of human keratinocyte and squamous cell carcinoma responses to UVB irradiation: implications for skin and epithelial cancer

To gain insight into the transformation of epidermal cells into squamous carcinoma cells (SCC), we compared the response to ultraviolet B radiation (UVB) of normal human epidermal keratinocytes (NHEK) versus their transformed counterpart, SCC, using biological and molecular profiling. DNA microarray analyses (Affymetrix), approximately 12000 genes) indicated that the major group of upregulated genes in keratinocytes fall into three categories: (i). antiapoptotic and cell survival factors, including chemokines of the CXC/CC subfamilies (e.g. IL-8, GRO-1, -2, -3, SCYA20), growth factors (e.g. HB-EGF, CTGF, INSL-4), and proinflammatory mediators (e.g. COX-2, S100A9), (ii). DNA repair-related genes (e.g. GADD45, ERCC, BTG-1, Histones), and (iii). ECM proteases (MMP-1, -10). The major downregulated genes are DeltaNp63 and PUMILIO, two potential markers for the maintenance of keratinocyte stem cells. NHEK were found to be more resistant than SCC to UVB-induced apoptosis and this resistance was mainly because of the protection from cell death by secreted survival factors, since it can be transferred from NHEK to SCC cultures by the conditioned medium. Whereas the response of keratinocytes to UVB involved regulation of key checkpoint genes (p53, MDM2, p21(Cip1), DeltaNp63), as well as antiapoptotic and DNA repair-related genes - no or little regulation of these genes was observed in SCC. The effect of UVB on NHEK and SCC resulted in upregulation of 251 and 127 genes, respectively, and downregulation of 322 genes in NHEK and 117 genes in SCC. To further analyse these changes, we used a novel unsupervised coupled two-way clustering method that allowed the identification of groups of genes that clearly partitioned keratinocytes from SCC, including a group of genes whose constitutive expression levels were similar before UVB. This allowed the identification of discriminating genes not otherwise revealed by simple static comparison in the absence of UVB irradiation. The implication of the changes in gene profile in keratinocytes for epithelial cancer is discussed.

Lack of Fas (APO-1/CD95) gene structural alterations or transcript variant ratio changes in breast cancer

Fas (APO-1/CD95) is a transmembrane receptor protein involved in cell death signaling. Fas receptor and ligand are both expressed in breast cancer cells, however these cells are resistant to apoptosis. Fas gene mutations were detected in hematological and solid tumors, while overexpression of a soluble Fas isoform in serum was related to cancer stage and prognosis. In this work, direct sequencing of exons 6 and 9 of the Fas gene from 90 patients did not reveal any structural alterations. Moreover, no decrease was found in the ratio of the corresponding mRNA species of transmembrane versus soluble Fas isoforms in 31 breast cancer samples compared to 14 controls. Therefore, inhibition of Fas-mediated apoptosis may not be due to structural alterations in the critical exons 6 and 9 of the Fas gene or a shift of expression towards the soluble Fas isoform, but to other mechanisms operating in breast cancer cells.

Morphology transitions induced by chemotherapy in carcinomas in situ

Recently, we have proposed a nutrient-limited model for the avascular growth of tumors including cell proliferation, motility, and death [S. C. Ferreira, Jr., M. L. Martins, and M. J. Vilela, Phys. Rev. E 65, 021907 (2002)], which qualitatively reproduces commonly observed morphologies for carcinomas in situ. In the present work, we analyze the effects of distinct chemotherapeutic strategies on the patterns, scaling, and growth laws obtained for the nutrient-limited model. Two kinds of chemotherapeutic strategies were considered, namely, those that kill cancer cells and those that block cell mitosis but allow the cell to survive for some time. Depending on the chemotherapeutic schedule used, the tumors are completely eliminated, reach a stationary size, or grow following power laws. The model suggests that the scaling properties of the tumors are not affected by the mild cytotoxic treatments, although a reduction in growth rates and an increase in invasiveness are observed. For the strategies based on antimitotic drugs, a morphological transition in which compact tumors become more fractal under aggressive treatments was seen.

Increased expression of the bcl6 and CD10 proteins is associated with increased apoptosis and proliferation in diffuse large B-cell lymphomas

There is increasing evidence that bcl6 and CD10 expression may be related to apoptosis and cell cycle progression. Therefore, 79 cases of de novo diffuse large B-cell lymphomas were studied for the expression of bcl6 and CD10 proteins in relation to 1) the apoptotic index; 2) the proliferation-associated proteins Ki67, cyclin A, and cyclin B1; and 3) the expression of the bcl2, p53, Rb, p16, and p27 proteins. Expression of bcl6, CD10, and bcl2 proteins was found in 54/79 (68%), 28/79 (35%), and 47/74 (63%) cases, respectively. The bcl6/CD10 patterns were as follows: bcl6+/CD10+ (26 cases, 32%), bcl6+/CD10- (28 cases, 33%), bcl6-/CD10- (23 cases, 31%), and bcl6-/CD10+ (2 cases, 4%). Significant positive correlations were found between bcl6/Ki67 (r =.328, P =.003), bcl6/cyclin A (r =.265, P =.018), bcl6/apoptotic index (r =.327, P =.010), CD10/Ki67 (r =.296, P =.008), and CD10/apoptotic index (r =.397, P =.001). In addition, high expression of bcl6 showed significant correlation with negative (null/low) bcl2 expression (chi(2) test, P =.002). The above findings indicate that increased expression of the bcl6 and CD10 proteins is associated with increased apoptosis and proliferation in diffuse large B-cell lymphomas. The association between increased bcl6 expression and enhanced apoptosis might be due, at least in part, to the null/low bcl2 expression because previous in vitro data showed that bcl6 overexpression induces apoptosis accompanied by bcl2 and bcl-xl downregulation. Moreover, significant correlation was found between increased apoptotic index and the bcl6+/CD10+ pattern (t test: P =.014, Mann-Whitney test: P =.046). This finding and the positive correlation of the apoptotic index with bcl6 and CD10 expression may be related to previous results showing that the expression of these proteins has favorable effects on the clinical outcome of diffuse large B-cell lymphomas.

Oncogenic potential of a dominant negative mutant of interferon regulatory factor 3

Interferon regulatory factor 3 (IRF3) is activated in response to various environmental stresses including viral infection and DNA-damaging agents. However, the biological function of IRF3 in cell growth is not well understood. We demonstrated that IRF3 markedly inhibited growth and colony formation of cells. IRF3 blocked DNA synthesis and induced apoptosis. Based on this negative control of cell growth by IRF3, we examined whether functional loss of IRF3 may contribute to oncogenic transformation. IRF3 activity was specifically inhibited by expression of its dominant negative mutant. This mutant lacks a portion of the DNA binding domain like IRF3a, an alternative splice form of IRF3 in the cells. This dominant negative inhibition blocked expression of specific IRF3 target genes. Mutant IRF3 efficiently transformed NIH3T3 cells, as demonstrated by anchorage-independent growth in soft agar and tumorigenicity in nude mice. These results imply that IRF3 may function as a tumor suppressor and suggest a possible role for the relative levels of IRF3 and its dominant negative mutant in tumorigenesis.

C-Raf controlled pathways in the protection of tumor cells from apoptosis

The Raf serine-threonine kinase is upregulated in many human tumors and plays a pivotal role in tumor cell proliferation and survival. Abrogation of c-Raf expression by specific antisense oligonucleotides (Raf-AS-ODN) efficiently blocks tumor cell growth and induces apoptosis in human cancer cells. The signaling pathways and molecular mechanisms c-Raf utilizes to mediate the survival of tumor cells are, however, not well understood. Here we show that apoptosis triggered by Raf depletion cannot be overcome by ectopic Bcl-2 expression and occurs in the absence of cytochrome c release, arguing against a direct impact of c-Raf on mitochondrial pathways of apoptosis regulation. We also show that c-Raf depletion leads to a clearly decreased expression of different epidermal growth factor (EGF) receptor ligands, suggesting that the autocrine stimulation of an EGF receptor-mediated survival pathway might be involved in the blockade of tumor cell apoptotis by c-Raf.

The apoptosis-associated protein BNIPL interacts with two cell proliferation-related proteins, MIF and GFER

Bcl-2/adenovirus E1B 19 kDa interacting protein 2-like, BNIP-2-like (BNIPL) is a recently cloned and characterized apoptosis-associated protein that shares 72% homology with BNIP-2. It is highly expressed in human placenta and lung. A yeast two-hybrid system was used to obtain two BNIPL-interacting proteins, MIF (macrophage migration inhibitory factor) and GFER (growth factor erv1 (Saccharomyces cerevisiae)-like). The interactions were confirmed by glutathione S-transferase pull-down assay in vitro and co-immunoprecipitation assay in vivo. Colony formation assay and cell proliferation test suggest that overexpression of BNIPL could inhibit the growth of BEL-7402 cells. These findings suggest that BNIPL may physically bind to cell proliferation-related proteins, MIF and GFER.

New analogues of the anticancer E7070: synthesis and pharmacology

Cell cycle control in the G1 phase has attracted considerable attention in recent cancer research, because many of the important proteins involved in G1 progression or G1/S transition have been found to play a crucial role in proliferation, differentiation, transformation, and programmed cell death (apoptosis). E7070 is a novel antitumor sulfonamide, with a unique mode of action that affects G1 progression of the cell cycle. A series of compounds containing an N-[1-(3,4,5-trimethoxybenzyl)-1H-indol-5-yl]benzene sulfonamide, analogues of E7070, was synthesized and evaluated as potential antitumor agents. Cell cycle analysis with PC3 human prostate cancer cells revealed a cellular accumulation in the G1 phase.

Apoptosis and plastic surgery

Apoptosis, or programmed cell death, is a phenomenon that is integral to development and cellular homeostasis. In the last decade, many of the essential molecules and pathways that control this phenomenon have been elucidated. Because apoptosis is involved in almost all physiologic and pathologic processes, the understanding of its regulation has significant clinical ramifications. This article reviews the basic understanding of programmed cell death in terms of the effector molecules and pathways. Areas of interest to plastic surgeons are reviewed as they pertain to apoptosis. These areas include allotransplantation, craniofacial and limb development, flap survival, wound healing, stem cell science, and physiologic aging. These topics have not yet been studied extensively in the context of cell death. In this review article, other related and more comprehensively studied scientific areas are used to extrapolate their relevance to apoptosis. Apoptosis is an increasingly better understood process. With the knowledge of how programmed cell death is controlled, combined with the improved ability to effectively perform genetic manipulation and to design specific chemical approaches, apoptosis is gaining clinical relevance. In the next few years, practical clinical breakthroughs will help the medical community to understand the phenomenon of apoptosis and how it relates to the needs of patients.

The mechanisms of apoptosis in biology and medicine: a new focus for ophthalmology

Defects in apoptosis (programmed cell death) have recently emerged as being closely involved in the pathogenesis of most ocular diseases and, therefore, apoptosis is now a topic of exponential interest in ophthalmology. This review summarizes recent works on mechanisms of apoptosis, from its initiation and modulation to the switching-on of its execution machinery. Interactions of cell death with cell division programs to orchestrate ontogenesis, aging, and adult life and their alterations in human diseases are pointed out. Two main apoptotic signaling pathways are identified: a death receptor-dependent (extrinsic) pathway and a mitochondrion-dependent (intrinsic) pathway. Mitochondrion harbors both antiapoptotic (Bcl-2, Bcl-XL) and apoptotic factors (Smac/Diablo, Apaf-1, cytochrome c). Its permeability transition pore (mPTP) is the main trigger of cell suicide. The process of mPTP opening, in association with extrusion to cytoplasm of a variety of apoptotic factors, is shown. Cytochrome c is one of these apoptotic factors. When expelled to cytoplasm, this double-faced respiratory chain component assembles with two other modules, Apaf-1 and procaspase 9, to form a protein complex--the apoptosome--that starts apoptosis execution. Another respiratory chain component, the CoQ10, is believed to counteract mPTP opening. What makes apoptosis particularly exciting for medicine is that its dysfunctions play a central role in the pathogenesis of several human diseases. For instance, excesses of apoptosis lead to cell loss that accompanies neurodegenerative diseases, whereas genetically determined defects of apoptosis lead to the deregulated cell proliferation typical of cancer. A variety of ophthalmologic diseases, such as post-keratectomy haze, corneal lesions, cataract, glaucoma, senile maculopathies, and genetic ocular pathologies, that underlie apoptosis dysfunctions are treated in detail in the other reviews of this issue.

Apoptosis in hematological disorders

Apoptosis, the cell's intrinsic death program, plays a critical role in the regulation of tissue homeostasis, especially in cell systems with a high turnover rate such as hematopoietic cells. Imbalances between proliferation and cell death may result in premature death, uncontrolled polyclonal or monoclonal expansion or tumor formation. Also, cytotoxic therapy and immunotherapy of leukemia and lymphoma predominantly mediates cell death through induction of apoptosis. Understanding the molecular events by which tumor cells evade apoptotic deletion and which induce apoptosis by cytotoxic therapies, have provided a paradigm to link normal growth control, malignant transformation and response to therapy.

MIB-1 index in thyroid tumors: a predictor of the clinical course in papillary thyroid carcinoma

MIB-1 is useful in evaluating proliferative activity and in predicting the aggressiveness in a variety of tumors. To investigate if MIB-1 immunoreactivity can add prognostic information to conventional prognostic variables in papillary thyroid carcinoma (PTC), 30 PTCs were evaluated using the MIB-1 antibody. For comparison, 10 follicular thyroid carcinomas (FTC), 8 anaplastic thyroid carcinomas (ATC), and 96 follicular thyroid adenomas (FTA) were similarly analyzed. The median MIB-1 index was 0.5% in FTA, 1.9% in PTC, 2.7% in FTC, and 16.2% in ATC. The 13 tumors from patients classified as having aggressive PTC (defined as dead from disease, persisting disease, or the occurrence of distant metastases) had significantly higher MIB-1 index (median, 5.4%) than the 17 patients with nonaggressive disease (median, 1.1%). MIB-1 index 1.85% or more was found to be an independently significant risk factor for a less favorable clinical course in PTC. Because of overlap of single values the utility of MIB-1 index as a clinical test is somewhat limited. Still, at levels where no overlap occurs (MIB-1 index 2 3.2% or ' 0.5%) the index seems to add information to the established prognostic parameters. MIB-1 index should therefore be considered in routine histopathology of PTC.

A macrocyclic zinc(II) fluorophore as a detector of apoptosis

Our originally designed dansylamidoethylcyclen 4 as a biomimetic Zn(2+)-selective fluorophore has been demonstrated to be a good detector of the apoptosis (induced by an anticancer agent, etoposide, and H(2)O(2)) in cancer cells such as HeLa and HL60 cells. The macrocyclic Zn(2+) ligand 4 (mostly as a deprotonated form) is cell-permeable to show weak fluorescence (emission at 550 nm), which forms a strong fluorescent 1:1 Zn(2+) complex 5 (emission at 530 nm) when Zn(2+) is incorporated into the cells by a zinc(II) ionophore pyrithione. Thus formed, Zn(2+) complex 5 is cell-impermeable and remains intact over a few hours. When apoptosis in HeLa or HL60 cells is artificially induced, 4 selectively and strongly stains apoptotic cells only at early stages, which was verified by using the conventional apoptosis detection probe annexin V-Cy3. Detection of the apoptotic cells by 4 was perhaps due to significantly increased free Zn(2+) flux at early stages of apoptosis. Apoptotic detection by 4 has been compared with a presently available Zn(2+) fluorophore, Zinquin 1. We present that 4 has advantages in detection of apoptosis over annexin V-Cy3 and Zinquin 1.

NF-kappaB in cancer: a marked target

The imbalance between proliferation and programmed cell death (apoptosis) is one of the critical cellular events that lead to oncogenesis. While there is no doubt that uncontrolled cell proliferation is essential for the development of cancer, deregulation of apoptosis may play an equally important role in this process. Inhibition of apoptosis prevents the death of tumor cells with DNA damage either associated with carcinogenic initiation or cancer therapy. The transcription factor NF-kappaB is a key regulator in oncogenesis. By promoting proliferation and inhibiting apoptosis, NF-kappaB tips the balance between proliferation and apoptosis toward malignant growth in tumor cells.

Clinical, cellular, and molecular aspects of cancer invasion

Invasion causes cancer malignancy. We review recent data about cellular and molecular mechanisms of invasion, focusing on cross-talk between the invaders and the host. Cancer disturbs these cellular activities that maintain multicellular organisms, namely, growth, differentiation, apoptosis, and tissue integrity. Multiple alterations in the genome of cancer cells underlie tumor development. These genetic alterations occur in varying orders; many of them concomitantly influence invasion as well as the other cancer-related cellular activities. Examples discussed are genes encoding elements of the cadherin/catenin complex, the nonreceptor tyrosine kinase Src, the receptor tyrosine kinases c-Met and FGFR, the small GTPase Ras, and the dual phosphatase PTEN. In microorganisms, invasion genes belong to the class of virulence genes. There are numerous clinical and experimental observations showing that invasion results from the cross-talk between cancer cells and host cells, comprising myofibroblasts, endothelial cells, and leukocytes, all of which are themselves invasive. In bone metastases, host osteoclasts serve as targets for therapy. The molecular analysis of invasion-associated cellular activities, namely, homotypic and heterotypic cell-cell adhesion, cell-matrix interactions and ectopic survival, migration, and proteolysis, reveal branching signal transduction pathways with extensive networks between individual pathways. Cellular responses to invasion-stimulatory molecules such as scatter factor, chemokines, leptin, trefoil factors, and bile acids or inhibitory factors such as platelet activating factor and thrombin depend on activation of trimeric G proteins, phosphoinositide 3-kinase, and the Rac and Rho family of small GTPases. The role of proteolysis in invasion is not limited to breakdown of extracellular matrix but also causes cleavage of proinvasive fragments from cell surface glycoproteins.

Apoptosis and lung cancer: a review

It is important to understand the molecular events that contribute to drug-induced apoptosis, and how tumors evade apoptotic death. Defects in apoptosis are implicated in both tumorigenesis and drug resistance, and these defects are cause of chemotherapy failures. These studies should explain the relationship between cancer genetics and treatment sensitivity, and should enable a more rational approach to anticancer drug design and therapy. Lung cancer is a major cause of cancer deaths throughout the world. Small cell lung carcinoma (SCLC) and non-small cell lung carcinoma (NSCLC) represent the two major categories of lung cancer that differ in their sensitivity to undergo apoptosis. The role of apoptosis regulation in lung cancer with major focus on the differential sensitivities of the major subtypes is reviewed.

Genomic dissection for characterization of cancerous oral epithelium tissues using transcription profiling

Genome-wide and high-throughput functional genomic tools offer the potential of identifying disease-associated genes and dissecting disease regulatory patterns. There is a need for a set of systematic bioinformatic tools that handles efficiently a large number of variables for extracting biological meaning from experimental outputs. We present well-characterized statistical tools to discover genes that are differentially expressed between malignant oral epithelial and normal tissues in microarray experiments and to construct a robust classifier using the identified discriminatory genes. Those tools include Wilks' lambda score, error rate estimated from leave-one out cross-validation (LOOCV) and Fisher Discriminant Analysis (FDA). High Density DNA microarrays and Real Time Quantitative PCR were employed for the generation and validation of the transcription profile of the oral cancer and normal samples. We identified 45 genes that are strongly correlated with malignancy. Of the 45 genes identified, six have been previously implicated in the disease, and two are uncharacterized clones.

Myc-Mediated Proliferation and Lymphomagenesis, but Not Apoptosis, Are Compromised by E2f1 Loss

Myc and E2f1 promote cell cycle progression, but overexpression of either can trigger p53-dependent apoptosis. Mice expressing an Emu-Myc transgene in B lymphocytes develop lymphomas, the majority of which sustain mutations of either the Arf or p53 tumor suppressors. Emu-Myc transgenic mice lacking one or both E2f1 alleles exhibited a slower onset of lymphoma development associated with increased expression of the cyclin-dependent kinase inhibitor p27(Kip1) and a reduced S phase fraction in precancerous B cells. In contrast, Myc-induced apoptosis and the frequency of Arf and p53 mutations in lymphomas were unaffected by E2f1 loss. Therefore, Myc does not require E2f1 to induce Arf, p53, or apoptosis in B cells, but depends upon E2f1 to accelerate cell cycle progression and downregulate p27(Kip1).

Role of homeobox genes in normal mammary gland development and breast tumorigenesis

The role of homeobox-containing genes in embryogenesis and organogenesis is well documented. Also, a sizeable body of evidence has accumulated and supports the fact that homeobox genes, when dysregulated, are involved in tumorigenesis. However, the precise mechanisms of homeobox gene functions are largely unknown. The mammary gland, in which most maturation occurs postnatally, provides an ideal model for studying the functions of homeobox genes in both development and tumorigenesis. The expression of many homeobox genes has been detected in both normal mammary gland and neoplastic breast tissues. In the normal mammary gland, the expression of homeobox genes is coordinately regulated by hormone and extracellular matrix (ECM) and other unknown factors in a spatial and temporal manner in both stromal and epithelial cells. Animals with misexpressed homeobox genes displayed different extents of defects in ductal proliferation, side branching, and alveoli formation, implying that homeobox genes are important for normal mammary gland development. Recent studies of homeobox genes in breast cancer cells and primary tumors indicate that they may also play a contributory or causal role in tumorigenesis by regulating the cell cycle, apoptosis, angiogenesis, and/or metastasis.

ECRG2, a novel candidate of tumor suppressor gene in the esophageal carcinoma, interacts directly with metallothionein 2A and links to apoptosis

Esophageal cancer related gene 2 (ECRG2) is a novel candidate of the tumor suppressor gene identified from human esophagus. To study the biological role of the ECRG2 gene, we performed a GAL4-based yeast two-hybrid screening of a human fetal liver cDNA library. Using the ECRG2 cDNA as bait, we identified nine putative clones as associated proteins. The interaction of ECRG2 and metallothionein 2A (MT2A) was confirmed by glutathione S-transferase pull-down assays in vitro and co-immunoprecipitation experiments in vivo. ECRG2 co-localized with MT2A mostly to nuclei and slightly to cytoplasm, as shown by confocal microscopy. Transfection of ECRG2 gene inhibited cell proliferation and induced apoptosis in esophageal cancer cells. In the co-transfection of ECRG2 and MT2A assays, cell proliferation was inhibited and apoptosis was slightly induced compared with control groups. When we used antisense MT2A to interdict the effect of MT2A, the inhibition of cell proliferation and induction of apoptosis were significantly enhanced. When we used antisense ECRG2 to interdict the effect of ECRG2 in the group of Bel7402 cells co-transfected with ECRG2 and MT2A, the inhibition of cell proliferation and induction of apoptosis disappeared. The results provide evidence for ECRG2 in esophageal cancer cells acting as a bifunctional protein associated with the regulation of cell proliferation and induction of apoptosis. ECRG2 might reduce the function of MT2A on the regulation of cell proliferation and induction of apoptosis. The physical interaction of ECRG2 and MT2A may play an important role in the carcinogenesis of esophageal cancer.

MAGE-A4 interacts with the liver oncoprotein gankyrin and suppresses its tumorigenic activity

Hepatocellular carcinoma ranks among the most common malignancies in Southeast Asia and South Africa. Although there are many modalities of treatment, the recurrence and metastasis rates are high, and the prognosis is unsatisfactory. Gankyrin, a recently found oncoprotein, is a promising target for drug therapy because it is overexpressed in all studied hepatocellular carcinomas. Gankyrin contains six ankyrin repeats and interacts with Rb, Cdk4, and the S6 ATPase of the 26 S proteasome. In this study, a yeast two-hybrid screen with gankyrin has identified MAGE-A4 as another interacting protein. The interaction, mediated by the C-terminal half of MAGE-A4, was reproduced in mammalian cells. The interaction was specific to MAGE-A4, because other MAGE family proteins structurally similar to MAGE-A4, i.e. MAGE-A1, MAGE-A2, and MAGE-A12, did not bind to gankyrin. MAGE-A4 partially suppressed both anchorage-independent growth in vitro and tumor formation in athymic mice of gankyrin-overexpressing cells. The ability of mutant MAGE-A4 to interact with gankyrin correlated with the ability to suppress the anchorage-independent growth. These results demonstrate that MAGE-A4 binds to gankyrin and suppresses its oncogenic activity. So far, the major focus of studies on the MAGE proteins has been on their potential for cancer immunotherapy. Our results may also shed light on novel functions for MAGE-A proteins.

Combination of tumor necrosis factor-alpha with sulindac augments its apoptotic potential and suppresses tumor growth of human carcinoma cells in nude mice

BACKGROUND

Resistance to apoptosis may be responsible for a principal mechanism by which cancer cells overcome anticancer therapies. Among antiapoptotic signals, the transcription factor, NF-kappaB, plays a pivotal role in the resistance because it is frequently activated in many primary carcinoma cells. However, NF-kappaB is also activated by several anticancer therapies, including tumor necrosis factor-alpha (TNF-alpha). The NF-kappaB-mediated survival signals are supposed to evade these therapies. Recently, a nonsteroidal antiinflammatory drug, sulindac, and its metabolites have been shown to inhibit the NF-kappaB pathway and to enhance TNF-alpha-mediated apoptosis in lung carcinoma cell lines. In the current study, the authors investigated whether sulindac can augment TNF-alpha-mediated apoptosis in other human carcinoma cells and whether it can be applied for in vivo clinical usage.

METHODS

Human gastric MKN45 and cervical HeLa carcinoma cells were treated with sulindac and/or TNF-alpha. Proapoptotic effects of these agents were evaluated by trypan blue exclusion assay, DNA fragmentation, and caspase-3 activity. The effect of sulindac on NF-kappaB activation was evaluated by luciferase reporter and gel-shift assays. The suppressive effects of these reagents on the subcutaneous tumor growth of MKN45 cells were evaluated by measuring tumor size in nude mice.

RESULTS

Sulindac inhibited TNF-alpha-mediated NF-kappaB activation and greatly sensitized MKN45 and HeLa cell lines to TNF-alpha. Moreover, in vivo tumor growth of MKN45 cells was inhibited most strongly by a combination of TNF-alpha with sulindac compared with TNF-alpha or sulindac alone.

CONCLUSIONS

The current study data strongly suggest that combination therapy of TNF-alpha with sulindac may sensitize tumor cells to TNF-alpha and augment its proapoptotic potential. Therefore, in combination with sulindac, TNF-alpha may become a potentially useful anticancer agent to suppress tumor growth in a wide range of carcinomas.

8q24 Copy number gains and expression of the c-myc mRNA stabilizing protein CRD-BP in primary breast carcinomas

The coding region determinant binding protein (CRD-BP) was isolated by virtue of its high affinity to the c-myc mRNA coding region stability determinant and shown to shield this message from nucleolytic attack, prolonging its half-life. CRD-BP is normally expressed during fetal life but is also activated de novo in tumors. Considering that aberrant CRD-BP expression may represent an additional mechanism interfering with c-myc regulation, we screened 118 primary breast carcinomas for CRD-BP expression, 60 of which had also been analyzed by comparative genomic hybridization (CGH). Copy number gains encompassing 8q24, the chromosome band that contains the c-myc locus, were detected in 48.3% (29/60) of tumors, whereas gains involving band 17q21, which contains the CRD-BP locus, were observed in 18.3% (11/60) of tumors. CRD-BP expression was detected in 58.5% (69/118) of tumors, implying mechanisms of activation alternative to gene amplification. Altogether, some 75% of the tumors had alterations pertaining to c-myc since they either harbored 8q24 gains and/or expressed CRD-BP. Significant associations were detected between CRD-BP expression and the absence of estrogen receptors (p = 0.005) and between the presence of 8q24 gains and an increased number of genomic changes as measured by CGH (p = 0.0017). Tumors were divided into 4 groups according to CRD-BP expression and 8q24 gains. The odds for tumors having both characteristics to be classified as poorly differentiated (grade III vs. grade I and II) were 19.6 times the corresponding odds for tumors neither expressing CRD-BP nor harboring 8q24 gains. For tumors either harboring 8q24 gains only or expressing CRD-BP alone, the corresponding odds were 6.4 and 3, respectively.