Molecular themes in oncogenesis

External imaging of CCND1, MYC, and KRAS oncogene mRNAs with tumor-targeted radionuclide-PNA-peptide chimeras

In 2005, breast cancer will kill approximately 40,410 women in the U.S., and pancreatic cancer will kill approximately 31,800 men and women in the U.S. Clinical examination and mammography, the currently accepted breast cancer screening methods, miss almost half of breast cancers in women younger than 40 years, approximately one-quarter of cancers in women aged 40-49 years, and one-fifth of cancers in women over 50 years old. Pancreatic cancer progresses rapidly, with only 1% of patients surviving more than 5 years after diagnosis. However, if the disease is diagnosed when it is localized, the 5-year survival is approximately 20%. It would be beneficial to detect breast cancer and pancreatic cancer at the earliest possible stage, when multimodal therapy with surgery, radiotherapy, and chemotherapy have the greatest chance of prolonging survival. Human estrogen receptor-positive breast cancer cells typically display elevated levels of Myc protein due to overexpression of MYC mRNA, elevated cyclin D1 protein due to overexpression of CCND1 mRNA, and elevated insulin-like growth factor 1 receptor (IGF1R) due to overexpression of IGF1R mRNA. We hypothesized that scintigraphic detection of MYC or CCND1 peptide nucleic acid (PNA) probes with an IGF1 peptide loop on the C-terminus, and a Tc-99m-chelator peptide on the N-terminus, could measure levels of MYC or CCND1 mRNA noninvasively in human IGF1R-overexpressing MCF7 breast cancer xenografts in immunocompromised mice. Similarly, human pancreatic cancer cells typically display elevated levels of KRAS mRNA and elevated IGF1R. Hence, we also hypothesized that a KRAS Tc-99m-chelator PNA-peptide probe could detect overexpression of KRAS mRNA in pancreatic cancer xenografts by scintigraphic imaging, or by positron emission tomography (PET) with a KRAS Cu-64-chelator PNA-peptide. Human MCF7 breast cancer xenografts in immunocompromised mice were imaged scintigraphically 4-24 h after tail-vein administration of MYC or CCND1 Tc-99m-chelator PNA-peptides, but not after administration of mismatch controls. Similarly, human Panc-1 pancreatic cancer cells xenografts were imaged scintigraphically 4 and 24 h after tail-vein administration of a KRAS Tc-99m-chelator PNA-peptide, and AsPC1 xenografts were imaged by PET 4 and 24 h after tail-vein adminstration of a KRAS Cu-64-chelator PNA-peptide. The radioprobes distributed normally to the kidneys, livers, tumors, and other tissues. External molecular imaging of oncogene mRNAs in solid tumors with radiolabel-PNA-peptide chimeras might in the future provide additional genetic characterization of pre-invasive and invasive breast cancers.

The new era in cancer research

For many years, discoveries about the genetic determinants of cancer appeared to be having only minor effects on efforts to control the disease in the clinic. Following advances made over the past decade, however, a description of cancer in molecular terms seems increasingly likely to improve the ways in which human cancers are detected, classified, monitored, and (especially) treated. Achieving the medical promise of this new era in cancer research will require a deeper understanding of the biology of cancer and imaginative application of new knowledge in the clinic, as well as political, social, and cultural changes.

Mechanisms and markers of carcinogenesis and neoplastic progression

Neoplastic transformation evolves over a period of time involving the progression of the cellular immunophenotype (IP) from normal to hyperplastic to dysplastic, and finally, to fully malignant IPs. Superimposed on these changes is the interaction of the initiated cell with its microenvironment, whereby the neoplastically transformed cells, through the regulation or dysregulation of cytoskeletal, integrin, protease and adhesion molecules, develop a novel manner of relation with their surrounding microenvironment. Studies of the neuroendocrine-immune network revealed that the hormonal and cytokine milieu plays an important role impacting the growth and dedifferentiation capabilities of neoplastic cells. This is further affected by the tumour cells themselves determining the constitution of this hormonal microenvironment, allowing the most aggressive and invasive of neoplastically transformed cell clones to promote their own growth and dissemination. The elucidation of the steps of the progression of cancer from premalignant to metastatic and invasive forms is of utmost importance in the differential diagnosis of neoplasms and in the establishment of more efficacious therapeutic regimens. These regimens will certainly begin to take on a more individualised form. The functional characterisation of various human malignancies as to the neoplastically transformed cells' IP, the bases of their interaction with tissue stromal elements, and the molecules involved in the humoral microenvironment of the particular stage of tumour will certainly allow for the better diagnosis, staging, prognostication and treatment of cancers in the future. This paper reviews carcinogenesis from nutritional, genetic and molecular, and humoral aspects, and discusses the importance of tumour markers in the diagnosis and therapeutic management of human cancer.

c-Myc, genome instability, and tumorigenesis: the devil is in the details

The c-myc oncogene acts as a pluripotent modulator of transcription during normal cell growth and proliferation. Deregulated c-myc activity in cancer can lead to excessive activation of its downstream pathways, and may also stimulate changes in gene expression and cellular signaling that are not observed under non-pathological conditions. Under certain conditions, aberrant c-myc activity is associated with the appearance of DNA damage-associated markers and karyotypic abnormalities. In this chapter, we discuss mechanisms by which c-myc may be directly or indirectly associated with the induction of genomic instability. The degree to which c-myc-induced genomic instability influences the initiation or progression of cancer is likely to depend on other factors, which are discussed herein.

Genotoxicity of vesicular fluid and saline extract of Taenia solium metacestodes in somatic cells of Drosophila melanogaster

Neurocysticercosis, the most common parasitic disease of the central nervous system, is caused by cysticerci of the helminth Taenia solium, which is prevalent in developing countries and is reemerging in affluent societies. This helminth is associated with brain tumors and hematological malignancies in humans. In the present study, we analyzed the genotoxicity of vesicular fluid (VF) and a saline extract (SE) of T. solium metacestodes in the Drosophila melanogaster wing somatic mutation and recombination test (SMART). Third-instar larvae derived from standard and high bioactivation crosses were treated for approximately 48 hr with 12.5, 25.0, and 50.0 microg/ml of VF and SE of T. solium metacestodes. Negative (phosphate buffered saline) and positive (10 mM urethane) controls were also included. The results showed that the two test compounds were genotoxic in both crosses of Drosophila. Nevertheless, further research is needed to determine the genotoxic potential of specific compounds present in VF and SE and their role in the development of cancer.

Induction of p53 and drug resistance following treatment with cisplatin or paclitaxel in ovarian cancer cell lines

Treatment failures result from resistance to chemotherapy in ovarian cancer. The effect of cisplatin and paclitaxel treatments on chemosensitivity was studied in ovarian cancer cells developed from a patient with stage IIIC disease. Cells (UL-3A, UL-3B) that recovered from cisplatin (Cis) and paclitaxel (Tax) treatments showed higher levels of p53, mdr-1 and chemoresistance than untreated controls. EC50 values of Cis and Tax for UL-3A clones were 7.2-34.6, average 20.9 microg/ml, while UL-3B clones ranged from 11.8-252.0 microg/ml, with a mean value of 73.2 microg/ml for Cis, and 260.0-4400.0 nM (mean 2555.0 nM) for Tax. Selection pressures during treatment may contribute to drug resistance.

The bone morphogenetic protein antagonist gremlin 1 is overexpressed in human cancers and interacts with YWHAH protein

BACKGROUND

Basic studies of oncogenesis have demonstrated that either the elevated production of particular oncogene proteins or the occurrence of qualitative abnormalities in oncogenes can contribute to neoplastic cellular transformation. The purpose of our study was to identify an unique gene that shows cancer-associated expression, and characterizes its function related to human carcinogenesis.

METHODS

We used the differential display (DD) RT-PCR method using normal cervical, cervical cancer, metastatic cervical tissues, and cervical cancer cell lines to identify genes overexpressed in cervical cancers and identified gremlin 1 which was overexpressed in cervical cancers. We determined expression levels of gremlin 1 using Northern blot analysis and immunohistochemical study in various types of human normal and cancer tissues. To understand the tumorigenesis pathway of identified gremlin 1 protein, we performed a yeast two-hybrid screen, GST pull down assay, and immunoprecipitation to identify gremlin 1 interacting proteins.

RESULTS

DDRT-PCR analysis revealed that gremlin 1 was overexpressed in uterine cervical cancer. We also identified a human gremlin 1 that was overexpressed in various human tumors including carcinomas of the lung, ovary, kidney, breast, colon, pancreas, and sarcoma. PIG-2-transfected HEK 293 cells exhibited growth stimulation and increased telomerase activity. Gremlin 1 interacted with homo sapiens tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, eta polypeptide (14-3-3 eta; YWHAH). YWHAH protein binding site for gremlin 1 was located between residues 61-80 and gremlin 1 binding site for YWHAH was found to be located between residues 1 to 67.

CONCLUSION

Gremlin 1 may play an oncogenic role especially in carcinomas of the uterine cervix, lung, ovary, kidney, breast, colon, pancreas, and sarcoma. Over-expressed gremlin 1 functions by interaction with YWHAH. Therefore, Gremlin 1 and its binding protein YWHAH could be good targets for developing diagnostic and therapeutic strategies against human cancers.

Transgenic mice with mammary gland targeted expression of human cortactin do not develop (pre-malignant) breast tumors: studies in MMTV-cortactin and MMTV-cortactin/-cyclin D1 bitransgenic mice

Background

In human breast cancers, amplification of chromosome 11q13 correlates with lymph node metastasis and increased mortality. To date, two genes located within this amplicon, CCND1 and EMS1, were considered to act as oncogenes, because overexpression of both proteins, respectively cyclin D1 and cortactin, correlated well with 11q13 amplification. Cyclin D1 is involved in cell cycle regulation and the F-actin-binding protein cortactin in cytoskeletal dynamics and cell migration. To study the role of cortactin in mammary gland tumorigenesis, we examined mouse mammary tumor virus (MMTV)-cortactin transgenic mice and MMTV-cortactin/-MMTV-cyclin D1 bitransgenic mice.

Methods

MMTV-cortactin transgenic mice were generated and intercrossed with previously described MMTV-cyclin D1 transgenic mice. Immunohistochemical, Northern and Western blot analyses were performed to study the expression of human transgene cortactin during mammary gland development and in mammary tumors. For tumor incidence studies, forced-bred, multiparous mice were used to enhance transgene expression in the mammary gland. Microscopical examination was performed using haematoxylin and eosin staining.

Results

Mammary gland tumors arose stochastically (incidence 21%) with a mean age of onset at 100 weeks. This incidence, however, did not exceed that of aged-matched control FVB/N mice (38%), which unexpectedly, also developed spontaneous mammary gland tumors. We mimicked 11q13 amplification by generating MMTV-cortactin/-MMTV-cyclin D1 bitransgenic mice but did not observe any synergistic effect of cortactin on cyclin D1-induced mammary hyperplasias or carcinomas, nor development of distant metastasis.

Conclusion

From this study, we conclude that development of (pre-malignant) breast tumors in either wild type or MMTV-cyclin D1 mice was not augmented due to mammary gland targeted overexpression of human cortactin.

Low correspondence between K-ras mutations in pancreatic cancer tissue and detection of K-ras mutations in circulating DNA

OBJECTIVE

K-ras is the most frequently mutated gene in pancreatic cancer; reported rates range from 70% to 90%. The aim of this study was to evaluate the correspondence between K-ras mutations in pancreatic cancer tissue and in circulating DNA and the value of K-ras mutations as serological marker.

METHODS

The research was conducted in 30 patients with pancreatic cancer in whom both plasma and neoplastic tissues were available. Such research was extended to circulating DNA isolated from 40 patients with chronic pancreatitis. Mutations in codon 12 were examined by mutant allele-specific amplification method and by direct sequencing. Serum values of routinely used tumor markers such as carbohydrate antigen (Ca) 19.9, carcinoembryonic antigen, Ca 50, and Ca 242 have been tested in all the patients enrolled in this study.

RESULTS

K-ras mutations were detected in 70% of neoplastic tissue samples, but no mutated DNA resulted in circulating DNA samples. The 60% of patients with tissue K-ras mutation showed elevation of some tumor markers among Ca 19.9, carcinoembryonic antigen, Ca 50, and Ca 242. As a whole, these last showed low sensitivity (20%-56.67%) and specificity (56.67%-77.5%) when compared with chronic pancreatitis.

CONCLUSION

Over the years, there has been no change in the direction of an earlier diagnosis by serological markers, and also, these data indicate that K-ras mutation in serum is an unsatisfactory method for the detection in patients with pancreatic cancer as well as in patients with high risk of progression toward neoplastic pancreatic disease.

Molecular mechanisms of human carcinogenesis

Intensive research efforts during the last several decades have increased our understanding of carcinogenesis, and have identified a genetic basis for the multi-step process of cancer development. Tumors grow through a process of clonal expansion driven by mutation. Several forms of molecular alteration have been described in human cancers, and these can be generally classified as chromosomal abnormalities and nucleotide sequence abnormalities. Most cancer cells display a phenotype characterized by genomic hypermutability, suggesting that genomic instability may precede the acquisition of transforming mutations in critical target genes. Reduced to its essence, cancer is a disease of abnormal gene expression, and these genetic abnormalities contribute to cancer pathogenesis through inactivation of negative mediators of cell proliferation (including tumor suppressor genes) and activation of positive mediators of cell proliferation (including proto-oncogenes). In several human tumor systems, specific genetic alterations have been shown to correlate with well-defined histopathological stages of tumor development and progression. Although the significance of mutations to the etiological mechanisms of tumor development has been debated, a causal role for such genetic lesions is now commonly accepted for most human cancers. Thus, genetic lesions represent an integral part of the processes of neoplastic transformation, tumorigenesis, and tumor progression, and as such represent potentially valuable markers for cancer detection and staging.

Prognostic/Predictive Factors in Breast Cancer

This can be an exciting time for pathologists and cytopathologists as we refine or knowledge of prognostic/predictive factors in breast cancer. We can become more visible in our role as consultants to the other physicians, and more engaged in our role as re-searchers. Recent advances in computer science, coupled with the availability of new biological markers, now provide unique opportunities for us to expand our diagnostic abilities and also predict the biologic behavior of a given tumor. Thus, we must become more familiar with emerging concepts and technologies in different disciplines.

Prooxidant activity of resveratrol in the presence of copper ions: mutagenicity in plasmid DNA

Resveratrol, a polyphenolic compound of plant origin, has been of much interest to researchers because of its anticancer and cardiovascular properties. Although antioxidant action of this compound is believed responsible for its reported properties, it has also been shown to exhibit prooxidant properties, especially in the presence of copper ions. Here we report the mutagenicity of resveratrol in plasmid DNA. Plasmid bluescript SK(+) DNA was treated with increasing concentrations of resveratrol in the presence and absence of copper ions, transformed into competent DH5alpha cells and sequenced. We looked for mutations caused by resveratrol treatment by comparing the sequences of treated plasmids versus control (untreated plasmid). The results show a decrease in the transformation efficiency of the plasmid after resveratrol treatment, and although all types of mutations were recorded, point mutations (deletions/substitutions) were found to be the predominant ones. Resveratrol alone resulted in deletion of mainly guanine bases. Since copper ions are known to be found in the nucleus, bound to guanine bases in chromatin, our results suggest mobilization of such endogenous copper by resveratrol resulting in prooxidant DNA cleavage at the site. Concentration of copper is reported to be elevated in various malignancies and the present studies might explain the reported anticancer activity of resveratrol in various cancer cell lines.

[Endocrine tumors associated to protein Gsalpha/Gi2alpha mutations]

Many oncogenic mutations promote tumor growth by inducing autonomous activity of proteins that normally transmit proliferative signal initiated by extracellular factors. G proteins are a family of guanine nucleotide binding proteins, which are structurally homologous and widely distributed in eukaryotic cells. They are composed of three different subunits (alpha, beta e gamma). The alpha subunit, which contains the guanine nucleotide-binding site, is unique to each G protein. The G proteins couple an array of seven transmembrane receptors at the cell surface with a variety of intracellular effectors, which produce second messenger molecules. A subset of endocrine tumors, such as GH- or ACTH-secreting pituitary adenomas, functioning thyroid adenomas, adrenocortical and gonadal tumors were associated with somatic activating mutations in the highly conserved codons of the Gs (Arg201 and Gln227) and Gi (Arg179 and Gln205) proteins. These findings indicated that the G proteins play a role as oncogenes, contributing with the human endocrine tumorigenesis.

Targeted Destruction of c-Myc by an Engineered Ubiquitin Ligase Suppresses Cell Transformation and Tumor Formation

Given that expression of c-Myc is up-regulated in many human malignancies, targeted inactivation of this oncoprotein is a potentially effective strategy for cancer treatment. The ubiquitin-proteasome pathway of protein degradation is highly specific and can be engineered to achieve the elimination of undesirable proteins such as oncogene products. We have now generated a fusion protein (designated Max-U) that is composed both of Max, which forms a heterodimer with c-Myc, and of CHIP, which is a U box-type ubiquitin ligase (E3). Max-U physically interacted with c-Myc in transfected cells and promoted the ubiquitylation of c-Myc in vitro. It also reduced the stability of c-Myc in vivo, resulting in suppression of transcriptional activity dependent on c-Myc. Expression of Max-U reduced both the abundance of endogenous c-Myc in and the proliferation rate of a Burkitt lymphoma cell line. Furthermore, expression of Max-U but not that of a catalytically inactive mutant thereof markedly inhibited both the anchorage-independent growth in vitro of NIH 3T3 cells that overexpress c-Myc as well as tumor formation by these cells in nude mice. These findings indicate that the targeted destruction of c-Myc by an artificial E3 may represent an effective therapeutic strategy for certain human malignancies.

Tumor dormancy and MYC inactivation: pushing cancer to the brink of normalcy

Upon MYC inactivation, tumors variously undergo proliferative arrest, cellular differentiation, and apoptosis and in some cases, apparently permanently revoking tumorigenesis. In liver tumor cells, we recently showed that MYC inactivation uncovers stem cell properties and triggers differentiation, but in this case, their neoplastic properties are restorable by MYC reactivation. Thus, whereas oncogene inactivation can push cancer to the brink of normalcy, some cells retain the latent capacity to turn cancerous again, arguing that they may exist in a state of tumor dormancy.

Disabling poxvirus pathogenesis by inhibition of Abl-family tyrosine kinases

The Poxviridae family members vaccinia and variola virus enter mammalian cells, replicate outside the nucleus and produce virions that travel to the cell surface along microtubules, fuse with the plasma membrane and egress from infected cells toward apposing cells on actin-filled membranous protrusions. We show that cell-associated enveloped virions (CEV) use Abl- and Src-family tyrosine kinases for actin motility, and that these kinases act in a redundant fashion, perhaps permitting motility in a greater range of cell types. Additionally, release of CEV from the cell requires Abl- but not Src-family tyrosine kinases, and is blocked by STI-571 (Gleevec), an Abl-family kinase inhibitor used to treat chronic myelogenous leukemia in humans. Finally, we show that STI-571 reduces viral dissemination by five orders of magnitude and promotes survival in infected mice, suggesting possible use for this drug in treating smallpox or complications associated with vaccination. This therapeutic approach may prove generally efficacious in treating microbial infections that rely on host tyrosine kinases, and, because the drug targets host but not viral molecules, this strategy is much less likely to engender resistance compared to conventional antimicrobial therapies.

Building a human kinase gene repository: bioinformatics, molecular cloning, and functional validation

Kinases catalyze the phosphorylation of proteins, lipids, sugars, nucleosides, and other important cellular metabolites and play key regulatory roles in all aspects of eukaryotic cell physiology. Here, we describe the mining of public databases to collect the sequence information of all identified human kinase genes and the cloning of the corresponding ORFs. We identified 663 genes, 511 encoding protein kinases, and 152 encoding nonprotein kinases. We describe the successful cloning and sequence verification of 270 of these genes. Subcloning of this gene set in mammalian expression vectors and their use in high-throughput cell-based screens allowed the validation of the clones at the level of expression and the identification of previously uncharacterized modulators of the survivin promoter. Moreover, expressions of the kinase genes in bacteria, followed by autophosphorylation assays, identified 21 protein kinases that showed autocatalytic activity. The work described here will facilitate the functional assaying of this important gene family in phenotypic screens and their use in biochemical and structural studies.

Expression, purification, and characterization of rat protein tyrosine phosphatase η catalytic domain

Receptor-like protein tyrosine phosphatases generally contain one or two conserved intracellular catalytic domains with a conserved sequence motif ([I/V]HCXAGXXR[S/T]G), a single transmembrane domain, and an external highly variable part. Here, we describe cloning of the intracellular catalytic domain of the rat protein tyrosine phosphatase eta (rPTPetaCD) into pET28a(+) vector, its expression in Escherichia coli, purification and initial characterization. The purification of His6-tagged rPTPetaCD to near homogeneity was achieved by a combination of affinity and size exclusion chromatography. The His-tag was subsequently removed by thrombin digestion. PhastGel IEF electrophoresis demonstrated that the isoelectric point of this 41 kDa His6-tag free recombinant protein was 7.3, which is just slightly higher than the theoretically predicted value of 7.2. To assess the functionality of the rPTPetaCD we used the pNPP hydrolysis assay and observed that the enzyme has a specific activity of 9 nmol/min/mug. The secondary structure and stability of the recombinant protein was also analyzed by circular dichroism and fluorescence spectroscopy. In summary, the rPTPetaCD is stable at 18 degrees C, properly folded, and fully active, which makes it a suitable candidate for structural and functional studies.

Endo180 binds to the C-terminal region of type I collagen

Type I collagen is a fibril-forming heterotrimer composed of two alpha1 and one alpha2 chains and plays a crucial role in cell-matrix adhesion and cell differentiation. Through a comprehensive differential display screening of oncogenic ras target genes, we have shown that the alpha1 chain of type I collagen (col1a1) is markedly down-regulated by the ras oncogene through the mitogen-activated protein kinase pathway. Although ras-transformed cells are no longer able to produce and secrete endogenous collagen, they can still adhere to exogenous collagen, suggesting that the cells express a collagen binding factor(s) on the cell surface. When the region of col1a1 encompassing the C-terminal glycine repeat and C-prodomain (amino acids 1000-1453) was affinity-labeled with human placental alkaline phosphatase, the secreted trimeric fusion protein could bind to the surface of Ras-transformed cells. Using biochemical purification followed by matrix-assisted laser desorption/ionization mass spectrometry analysis, we identified this collagen binding factor as Endo180 (uPARAP, CD280), a member of the mannose receptor family. Ectopic expression of Endo180 in CosE5 cells followed by in situ staining and quantitative binding assays confirmed that Endo180 indeed recognizes and binds to placental alkaline phosphatase. The interaction between Endo180 and the C-terminal region of type I collagen appears to play an important role in cell-matrix adhesion.

A novel human homologue of Drosophila polycomblike gene is up-regulated in multiple cancers

Polycomb group (PcG) proteins function to maintain the stable epigenetic repression of homeotic genes and other important developmental and cell cycle regulatory genes. Such maintenance establishes a form of cellular memory for its identity or state of differentiation. Accumulating evidence indicates that perturbation of this transcriptional memory may be required for tumor progression and may represent a hallmark of cancer. We have identified a novel gene encoding a human homologue of the Drosophila polycomblike protein, hPCL3. Through alternative polyadenylation and/or splicing, the gene encodes two nuclear proteins, hPCL3S and hPCL3L. Both proteins repressed transcription upon recruitment to the proximity of an HSV-tk promoter by a Gal4 DNA binding domain. Interestingly, the products of the hPCL3 gene, particularly the short form, hPCL3S, are markedly overexpressed in many types of cancers, including colon, skin, lung, rectal, cervical, uterus, and liver cancers. This increase in expression correlated with tumor progression. Both hPCL3S and hPCL3L messages were increased dramatically in most cell lines derived from various stages of melanoma and glioma tumor progression. Thus, our data link PcG deregulation to the progression of multiple cancers and may have important implications for unraveling the mechanisms of tumor progression.

Molecular biological design of novel antineoplastic therapies

Novel therapies represent a new strategy for the development of anticancer agents. New targets derived from the knowledge of the molecular structure and genetic defects has been useful in developing anticancer drugs that prolong or stabilise the progression of tumours with minimal systemic toxicities. In this review, the mechanism of action and the most significant trials regarding monoclonal antibodies, tyrosine kinase inhibitors, angiogenesis and cyclooxygenase inhibitor-based therapies, farnesyl transferase inhibitors and proteasome inhibitors are discussed. The potential biological end points and toxicities are also described. In conclusion, novel therapies present a promising class of anticancer agents, acting through different mechanisms and offering a new perspective in the treatment of cancer.

The cell-type-specificity of inherited predispositions to tumours: review and hypothesis

Most hereditary predispositions to tumours affect only one particular cell type of the body but the genes bearing the relevant germ-line mutation are not cell-type-specific. Some predisposition syndromes include increased risks of lesions (developmental or tumourous) of unrelated cell types, in any individual predisposed to the main lesion (e.g. osteosarcoma in patients predisposed to retinoblastoma). Other predispositions to additional lesions occur only in members of some families with the predisposition to the basic lesion (e.g. Gardner's syndrome in some families suffering familial adenomatous polyposis). In yet other predisposition syndromes, different mutations of the same gene are associated with markedly differing family-specific clinical syndromes. In particular, identical germline mutations (e.g. in APC, RET and PTEN genes), have been found associated with differing clinical syndromes in different families. This paper reviews previously suggested mechanisms of the cell-type specificity of inherited predispositions to tumour. Models of tumour formation in predisposition syndromes are discussed, especially those involving a germline mutation (the first 'hit') of a tumour suppressor gene (TSG) and a second (somatic) hit on the second allele of the same TSG. A modified model is suggested, such that the second hit is a co-mutation of the second allele of the TSG and a regulator which is specific for growth and/or differentiation of the cell type which is susceptible to the tumour predisposition. In some cases of tumour, the second hit may be large enough to be associated with a cytogenetically-demonstrable abnormality of the part of the chromosome carrying the TSG, but in other cases, the co-mutation may be of 'sub-cytogenetic' size (i.e. 10(2)-10(5) bases). For the latter, mutational mechanisms of frameshift and impaired fidelity of replication of DNA by DNA polyerases may sometimes be involved. Candidate cell-type-specific regulators may include microRNAs and perhaps transcription factors. It is suggested that searching the introns within 10(5)-10(6) bases either side of known of exonic mutations of TSGs associated with inherited tumour predisposition might reveal microRNA cell-type-specific regulators. Additional investigations may involve fluorescent in situ hybridisations on interphase tumour nuclei.

Downregulation of gene expression with negatively charged peptide nucleic acids (PNAs) in zebrafish embryos

We found that negatively charged, highly soluble PNA analogs with alternating phosphonates (HypNA-pPNAs) are effective and specific antisense agents in zebrafish embryos, showing comparable potency and greater specificity against chordin, ntl and uroD. In addition, we successfully phenocopied a dharma mutant that had not been found susceptible to MO knockdown. Both MO and HypNA-pPNAs against a tumor suppressor gene induced comparable upregulation of p53, illustrating similar effects on transcription profiles. HypNA-pPNAs are therefore a valuable alternative for reverse genetic studies, enabling the targeting of previously inaccessible genes in zebrafish or validating newly identified orthologs, and perhaps for reverse genetic studies in other organisms.

Promoter hypermethylation profile of kidney cancer

PURPOSE

Promoter hypermethylation is an important mechanism of inactivation of tumor suppressor genes in cancer cells. Kidney tumors are heterogeneous in their histology, genetics, and clinical behavior. To gain insight into the role of epigenetic silencing of tumor suppressor and cancer genes in kidney tumorigenesis, we determined a hypermethylation profile of kidney cancer.

EXPERIMENTAL DESIGN

We examined the promoter methylation status of 10 biologically significant tumor suppressor and cancer genes in 100 kidney tumors (50 clear cell, 20 papillary, 6 chromophobe, 5 collecting duct, 5 renal cell unclassified, 7 oncocytoma, 6 transitional cell carcinomas of the renal pelvis, and 1 Wilms' tumor) by methylation-specific PCR. The hypermethylation profile was examined with regard to clinicopathological characteristics of the kidney cancer patients.

RESULTS

Hypermethylation of one or more genes was found in 93 (93%) of 100 tumors. A total of 33% of kidney tumors had one gene, 35% two genes, 14% three genes, and 11% four or more genes hypermethylated. The frequency of hypermethylation of the 10 genes in the 100 tumor DNAs was VHL 8% (all clear cell), p16(INK4a) 10%, p14(ARF) 17%, APC 14%, MGMT 7%, GSTP1 12%, RARbeta2 12%, RASSF1A 45%, E-cadherin 11%, and Timp-3 58%. Hypermethylation was observed in all of the histological cell types and grades and stages examined. No hypermethylation was observed in specimens of normal kidney or ureteral tissue from 15 patients. Hypermethylation of VHL was specific to clear cell tumors. RASSF1A methylation was detected at a significantly higher frequency in papillary renal cell tumors and in high-grade tumors of all cell types. MGMT methylation was more frequent in nonsmokers. Simultaneous methylation of five or more genes was observed in 3 (3%) of 100 tumors and may indicate a methylator phenotype in kidney cancer. In addition, the CpG island in the promoter of the fumarate hydratase (FH) tumor suppressor gene was bisulfite sequenced and was found to be unmethylated in 15 papillary renal tumors.

CONCLUSIONS

Promoter hypermethylation is common, can occur relatively early, may disrupt critical pathways, and, thus, likely plays an important role in kidney tumorigenesis. A hypermethylation profile may be useful in predicting a patient's clinical outcome and provide molecular markers for diagnostic and prognostic approaches to kidney cancer.

Oncogenes as Novel Targets for Cancer Therapy (Part I)

In the past 10 years, progress made in cancer biology, genetics, and biotechnology has led to a major transition in cancer drug design and development. There has been a change from an emphasis on non-specific, cytotoxic agents to specific, molecular-based therapeutics. Mechanism-based therapy is designed to act on cellular and molecular targets that are causally involved in the formation, growth, and progression of human cancers. These agents, which may have greater selectivity for cancer versus normal cells, and which may produce better anti-tumor efficacy and lower host toxicity, can be small molecules, natural or engineered peptides, proteins, antibodies, or synthetic nucleic acids (e.g. antisense oligonucleotides, ribozymes, and siRNAs). Novel targets are identified and validated by state-of-the-art approaches, including high-throughput screening, combinatorial chemistry, and gene expression arrays, which increase the speed and efficiency of drug discovery and development. Examples of oncogene-based, molecular therapeutics that show promising clinical activity include trastuzumab (Herceptin), imatinib (Gleevec), and gefitinib (Iressa). However, the full potential of oncogenes as novel targets for cancer therapy has not been realized and many challenges remain, from the validation of novel targets, to the design of specific agents, to the evaluation of these agents in both preclinical and clinical settings. In maximizing the benefits of molecular therapeutics in monotherapy or combination therapy of cancer, it is necessary to have an understanding of the underlying molecular abnormalities and mechanisms involved. This is the first part of a four-part review in which we discuss progress made in the last decade as it relates to the discovery of novel oncogenes and signal transduction pathways, in the context of their potential as targets for cancer therapy. This part delineates the latest discoveries about the potential use of growth factors and protein tyrosine kinases as targets for therapy. Later parts focus on intermediate signaling pathways, transcription factors, and proteins involved in cell cycle, DNA damage, and apoptotic pathways.

RNA interference against retroviruses

Bang and Ellerman, and later Peyton Rous, reported the first identification of transmissible cancer-causing agents, which later turned out to be avian retroviruses. Today avian retroviruses are important models for study of retrovirus replication and pathogenesis, and also important pathogens of domestic fowl. Here we describe the use of RNA interference (RNAi) in live chick embryos to block replication of an avian retrovirus. We also describe inhibition of ASLV and HIV replication in cell culture with RNAi.

MYC inactivation uncovers pluripotent differentiation and tumour dormancy in hepatocellular cancer

Hepatocellular carcinoma is generally refractory to clinical treatment. Here, we report that inactivation of the MYC oncogene is sufficient to induce sustained regression of invasive liver cancers. MYC inactivation resulted en masse in tumour cells differentiating into hepatocytes and biliary cells forming bile duct structures, and this was associated with rapid loss of expression of the tumour marker alpha-fetoprotein, the increase in expression of liver cell markers cytokeratin 8 and carcinoembryonic antigen, and in some cells the liver stem cell marker cytokeratin 19. Using in vivo bioluminescence imaging we found that many of these tumour cells remained dormant as long as MYC remain inactivated; however, MYC reactivation immediately restored their neoplastic features. Using array comparative genomic hybridization we confirmed that these dormant liver cells and the restored tumour retained the identical molecular signature and hence were clonally derived from the tumour cells. Our results show how oncogene inactivation may reverse tumorigenesis in the most clinically difficult cancers. Oncogene inactivation uncovers the pluripotent capacity of tumours to differentiate into normal cellular lineages and tissue structures, while retaining their latent potential to become cancerous, and hence existing in a state of tumour dormancy.

Genes involved in stem cell fate decisions and commitment to differentiation play a role in skin disease

Multipotent stem cells residing in the bulge region of the hair follicle give rise to cells of different fates including those forming hair follicles, interfollicular epidermis, and associated glands. Stem cell fate determination is regulated by genes involved in both proliferation and differentiation, which are tightly regulated processes. Understanding the molecular mechanisms by which proliferation and differentiation are regulated will provide useful insight into treating human diseases caused by the deregulation of these processes. Two genes involved in regulating proliferation and differentiation are c-Myc and p63, both of which have been found to be deregulated/mutated in several human diseases. Accelerating proliferation leads to neoplastic human diseases and deregulated c-Myc has been implicated in a variety of cancers. Evidence indicates that c-Myc also diverts stem cells to an epidermal and sebaceous gland fate at the expense of the hair follicle fate. Therefore, deregulation of c-Myc has the potential to not only accelerate tumorigenesis, but also influence skin tumor phenotype. In addition, the inhibition of differentiation may also predispose to the development of skin cancer. Recent evidence suggests that the transcription factor p63, is not only responsible for the initiation of an epithelial stratification program during development, but also the maintenance of the proliferative potential of basal keratinocytes in mature epidermis. Mutations in the p63 gene have been shown to cause ectodermal dysplasias and deregulated expression of p63 has been observed in squamous cell carcinomas. In this review, we will discuss recent data implicating a role for both c-Myc and p63 in human skin diseases.

The molecular markers for prognostic evaluation of areca-associated buccal squamous cell carcinoma

BACKGROUND

Buccal squamous cell carcinoma (BSCC) is the most frequently occurring oral cancer in Asians due to the popularity of areca use in this area. The aim of the present study was to evaluate the survival of areca-associated BSCC associated with multiple molecular markers.

METHODS

Using immunohistochemistry, we evaluated the survival of a cohort of 55 patients with BSCC being followed long term, as correlated to the expression of variable markers.

RESULTS

We found that p53, p21, Rb, cyclin D1 (CCD1), MDM2, and gamma-catenin were positive in 81, 60, 70, 31, 88, and 44% of patients, respectively. Subjects with -ve immunoreactivity for CCD1, and +ve immunoreactivity for MDM2 and gamma-catenin had significantly better survival than subjects with the opposite immunoreactive pattern. KAPLAN-meier survival curves confirmed this association.

CONCLUSION

The data indicate that expression of CCD1, MDM2, and gamma-catenin might serve as potential prognostic markers for BSCC in areca-using patients.

Factors contributing to the outcome of oxidative damage to nucleic acids

Oxidative damage to DNA appears to be a factor in cancer, yet explanations for why highly elevated levels of such lesions do not always result in cancer remain elusive. Much of the genome is non-coding and lesions in these regions might be expected to have little biological effect, an inference supported by observations that there is preferential repair of coding sequences. RNA has an important coding function in protein synthesis, and yet the consequences of RNA oxidation are largely unknown. Some non-coding nucleic acid is functional, e.g. promoters, and damage to these sequences may well have biological consequences. Similarly, oxidative damage to DNA may promote microsatellite instability, inhibit methylation and accelerate telomere shortening. DNA repair appears pivotal to the maintenance of genome integrity, and genetic alterations in repair capacity, due to single nucleotide polymorphisms or mutation, may account for inter-individual differences in cancer susceptibility. This review will survey these aspects of oxidative damage to nucleic acids and their implication for disease.

Parvovirus vectors for cancer gene therapy

Parvoviruses comprise a group of single-stranded DNA viruses with greater potential for gene therapy applications. Unique characteristics of paroviruses, such as non-pathogenicity, antioncogenicity and methods of efficient recombinant vector production, have drawn more attention towards utilising parvovirus-based vectors in cancer gene therapy. Although > 30 different parvoviruses have been identified so far, recombinant vectors derived from adeno-associated virus (AAV), minute virus of mice (MVM), LuIII and parvovirus H1 have been successfully tested in many preclinical models of human diseases, including cancer. The present article will focus on the potential of non-replicating and autonomously replicating parvoviral vectors in cancer gene therapy, including strategies that target tumour cells directly or indirectly.

Transplacental lung carcinogenesis: molecular mechanisms and pathogenesis

A wide variety of studies in both animal models and human populations have demonstrated age-related differences in the susceptibility of the developing organism to environmentally prevalent toxicants. While this differential susceptibility has been clearly established, the mechanistic basis for these age-related differences is still poorly understood. The developing fetus utilizes many of the same metabolic and signaling pathways as adult organisms in responding to environmental agents. However, it is becoming increasingly evident that the fetus is not a "little adult" and exhibits unique biochemical responses and gene expression profiles to chemical and physical agents. Because of the rapid growth and developmental changes that occur during gestation, the fetus represents a particularly challenging research subject as a result of the dynamic alterations that occur in gene expression pathways as gene systems are activated or repressed during specific stages of development. Thus, an understanding of the mechanism(s) that render the developing organism more or less susceptible to specific carcinogenic agents is crucial for both regulatory decisions regarding the determination of safe levels of toxic chemicals released into the environment and also for determining the effects of therapeutic compounds in younger age groups and pregnant women. Concentrating on studies from the author's laboratory, this review will highlight recent research on the molecular pathogenesis of transplacentally induced tumors. While focusing on the lung, other animal models and recent human epidemiological studies will also be discussed to contrast similarities and differences in the developing and adult organisms in terms of responses to toxic chemicals, including metabolism of environmentally prevalent toxicants and alterations in gene systems at the molecular level.

Abnormality of the DNA double-strand-break checkpoint/repair genes, ATM, BRCA1 and TP53, in breast cancer is related to tumour grade

The role of the DNA double-strand-break (DSB) checkpoint/repair genes, ATM, BRCA1 and TP53, in sporadic breast cancer requires clarification, since ATM and BRCA1 mutations are rare in sporadic tumours. In an attempt to explain this phenomenon, we postulated that (i) in addition to genetic deletion, abnormal expression of DSB checkpoint/repair proteins might abolish the function of these genes and (ii) there might be a combined effect of individual defective genes during breast cancer pathogenesis. Using a largely homogenous group of 74 specimens of early-onset (⩽35 years of age) infiltrating ductal carcinomas, we examined associations between pathological grade and genetic deletion and/or abnormal protein expression of ATM, BRCA1 and TP53. The results showed that high-grade tumours displayed a high frequency of loss of heterozygosity (LOH) at, and/or abnormal expression of, ATM, BRCA1 and TP53. Multigenetic analysis showed abnormalities in BRCA1 to be independently associated with high-grade tumours. ATM and TP53 appeared to play an assistant role, abnormalities in these genes significantly increasing the possibility of poor differentiation in tumours with abnormalities in BRCA1. Furthermore, a higher number of abnormalities (LOH or abnormal expression) in these three genes correlated with poor tumour differentiation. Thus, this study suggests that combined changes in several DSB checkpoint/repair genes belonging to a common functional pathway are associated with breast cancer pathogenesis.

Detoxifying cancer causing agents to prevent cancer

Different vitamins and other micronutrients in vegetables, fruits, and other natural plant products may prevent cancer development (carcinogenesis) by interfering with detrimental actions of mutagens, carcinogens, and tumor promoters. The goal of current studies in cancer prevention is to determine the mechanisms of synergistic action of the natural source compounds known to inhibit one or more stages of carcinogenesis, that is, initiation and promotion/progression. Many natural cancer preventive agents are effective inhibitors of tumor initiation, promotion, and/or progression. The mechanism of action is related to their abilities to prevent critical carcinogen metabolism and to increase detoxification of carcinogens and tumor promoters. The authors review here the potential role of the detoxification system and, in particular, the roles of D-glucaric acid and the enzyme beta-glucuronidase in early detection and prevention of cancer. There is now growing evidence for the possible control of different stages of the cancer induction by inhibiting beta-glucuronidase with D-glucaric acid derivatives, especially with its salts (D-glucarates). D-Glucaric acid has been found in many vegetables and fruits. Therefore, the consumption of fruits and vegetables naturally rich in D-glucaric acid or self-medication with D-glucaric acid derivatives such as calcium D-glucarate offers a promising cancer prevention approach.

Molecular detection of noninvasive and invasive bladder tumor tissues and exfoliated cells by aberrant promoter methylation of laminin-5 encoding genes

Laminin-5 (LN5) anchors epithelial cells to the underlying basement membrane, and it is encoded by three distinct genes: LAMA3, LAMB3, and LAMC2. To metastasize and grow, cancer cells must invade and destroy the basement membrane. Our previous work has shown that epigenetic inactivation is a major mechanism of silencing LN5 genes in lung cancers. We extended our methylation studies to resected bladder tumors (n = 128) and exfoliated cell samples (bladder washes and voided urine; n = 71) and correlated the data with clinicopathologic findings. Nonmalignant urothelium had uniform expression of LN5 genes and lacked methylation. The methylation frequencies for LN5 genes in tumors were 21-45%, and there was excellent concordance between methylation in tumors and corresponding exfoliated cells. Methylation of LAMA3 and LAMB3 and the methylation index were correlated significantly with several parameters of poor prognosis (tumor grade, growth pattern, muscle invasion, tumor stage, and ploidy pattern), whereas methylation of LAMC2 and methylation index were associated with shortened patient survival. Of particular interest, methylation frequencies of LAMA3 helped to distinguish invasive (72%) from noninvasive (12%) tumors. These results suggest that methylation of LN5 genes has potential clinical applications in bladder cancers.

Multiple regulatory pathways of vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) expression in tumors

VPF/VEGF is a multi-functional cytokine with important roles in both vasculogenesis and angiogenesis. Its production is generally regulated by local oxygen concentration. Hypoxia stimulates VPF/VEGF production by increasing its gene transcription and the stability of its mRNA. The increase in transcription in hypoxia occurs mainly through the stabilization and activation of the transcription factor, Hypoxia Inducible Factor (HIF). Cellular oxygen concentration is not the only regulator of VPF/VEGF synthesis. Some cancer cells can produce high levels of VPF/VEGF even in normoxia. Clear cell renal carcinoma cell line (RCC) like 786-0, pancreatic carcinoma cell line, ASPC-1, fibrocarcinoma cell line, HT1080, ovarian cancer cells, etc. produce an elevated level of VPF/VEGF, which is not dependent on hypoxia. In this article, we discuss different regulatory pathways in tumor cells comprised of oncogenes, tumor suppressor genes etc. that play important roles, in both the transcription and stability of VPF/VEGF mRNA.

Gene replacement therapy for non-small cell lung cancer: a review

Current therapy such as radiation and chemotherapy controls less than 50% of lung cancers, summoning the development of novel therapeutic strategies that can directly target the underlying mechanisms of tumorigenesis. The clinical trials summarized in this article clearly demonstrate that contrary to initial predictions that gene therapy would not be suitable for cancer, gene replacement therapy is a viable potential addition to the arsenal for cancer. Gene expression has been documented and occurs even in the presence of an antiadenovirus immune response. Clinical trials have demonstrated that direct intratumor injection can cause tumor regression or prolonged stabilization of local disease, and the low toxicity associated with gene transfer indicates that tumor suppressor gene replacement can be readily combined with existing and future treatments. Initial concerns that the wide diversity of genetic lesions in cancer cells would prevent the application of gene therapy to cancer appear unfounded; on the contrary, correction of a single genetic lesion has resulted in significant tumor regression. Studies combining transfer of tumor suppressor genes with conventional DNA-damaging treatments indicate that correction of a defect in apoptosis induction can restore sensitivity to radiation and chemotherapy in some resistant tumors, and indications that sensitivity to killing might be enhanced in already sensitive tumors may eventually lead to reduced toxicity from chemotherapy and radiation therapy. The most recent data from the laboratory demonstrating damage to tumor suppressor genes in normal tissue and premalignant lesions even suggest that these genes may someday be useful in early intervention, diagnosis, and even prevention of cancer. Despite the obvious promise evident in the results of these studies, however, it is critical to recognize that there are still gaps in knowledge and technology to address. At the current rate of biotechnology development, it is only a matter of time until technical limitations that currently prevent the widespread application of gene therapy to cancer are overcome by development of more efficient vectors, discovery of novel genes, and development of combined modality approaches.

Apoptosis-related gene expression after hyperthermia in human tongue squamous cell carcinoma cells harboring wild-type or mutated-type p53

Hyperthermia is useful for the treatment of human head and neck cancer, as it is relatively easy to perform thermoregulation when compared with deep organs. In this study, we focused attention on the p53 as a predictive indicator of hyperthermic cancer therapy. We used two kinds of cell lines of a human squamous cell carcinoma (SAS) with identical backgrounds of function except for the p53 protein. We assayed the heat sensitivity, frequency of apoptosis, and apoptosis-related gene expression after heat treatment using DNA array. The SAS/neo (wild-type p53; wtp53) cells were sensitive to heat, and the induction of Caspase-3 activation and apoptosis in the wtp53 cells was clearly high compared with the SAS/mp53 (mutated p53; mp53) cells. The gene expression of apoptosis suppressive-genes such as IL-12 p35 decreased in the wtp53 cells, and IL-12 R beta1 increased in the mp53 cells, though apoptosis-promotive genes of Caspase-9, CD30 and CD40 were induced p53-independently by hyperthermia. It is suggested that heat-induced apoptosis was suppressed by IL-12-related genes in the mp53 cells. These findings strongly imply that p53 status is a useful candidate for a predictive indicator of the effectiveness in hyperthermic therapy.

CDC91L1 (PIG-U) is a newly discovered oncogene in human bladder cancer

Genomic amplification at 20q11-13 is a common event in human cancers. We isolated a germline translocation breakpoint at 20q11 from a bladder cancer patient. We identified CDC91L1, the gene encoding CDC91L1 (also called phosphatidylinositol glycan class U (PIG-U), a transamidase complex unit in the glycosylphosphatidylinositol (GPI) anchoring pathway), as the only gene whose expression was affected by the translocation. CDC91L1 was amplified and overexpressed in about one-third of bladder cancer cell lines and primary tumors, as well as in oncogenic uroepithelial cells transformed with human papillomavirus (HPV) E7. Forced overexpression of CDC91L1 malignantly transformed NIH3T3 cells in vitro and in vivo. Overexpression of CDC91L1 also resulted in upregulation of the urokinase receptor (uPAR), a GPI-anchored protein, and in turn increased STAT-3 phosphorylation in bladder cancer cells. Our findings suggest that CDC91L1 is an oncogene in bladder cancer, and implicate the GPI anchoring system as a potential oncogenic pathway and therapeutic target in human cancers.

Rapid Detection of K-ras Mutations in Bile by Peptide Nucleic Acid-mediated PCR Clamping and Melting Curve Analysis: Comparison with Restriction Fragment Length Polymorphism Analysis

Background: Current methods for detection of K-ras gene mutations are time-consuming. We aimed to develop a one-step PCR technique using fluorescent hybridization probes and competing peptide nucleic acid oligomers to detect K-ras mutations in bile and to compare the efficacy with restriction fragment length polymorphism (RFLP) analysis.

Methods: Bile samples were obtained from 116 patients with biliary obstruction, including gallstones (n = 64), benign biliary strictures (n = 6), pancreatic cancer (n = 20), and cholangiocarcinoma (n = 26). The DNA was extracted and subjected to K-ras mutation analysis by real-time PCR and RFLP analysis. Mutations were confirmed by direct sequencing. The sensitivity and specificity were calculated according to the clinical results.

Results: The analysis time for real-time PCR was <1 h, whereas RFLP analysis took more than 2 days. With the sensor probe designed for the GAT (G12D) mutant in codon 12 of the K-ras gene, the real-time PCR method also detected the GTT (G12V) mutant. In contrast, a specific sensor probe for the TGT (G12C) mutant detected GAT (G12D), AGT (G12S), and GTT (G12V) mutants in addition to the TGT mutant. The real-time PCR assay allowed the detection of mutation in a 3000-fold excess of wild-type bile DNA. In bile, K-ras codon 12 mutations were detected in 16 of 46 malignant cases by real-time PCR with the TGT probe and 15 by RFLP analysis. All benign cases were wild type.

Conclusion: Real-time PCR with a cysteine-specific (TGT) sensor probe can rapidly detect K-ras gene mutations in bile and diagnose malignant biliary obstruction with high specificity.

Reversibility of oncogene-induced cancer

Cancer can largely be conceived as a consequence of genomic catastrophes resulting in genetic events that usurp physiologic function of a normal cell. These genetic events mediate their pathologic effects by either activating oncogenes or inactivating tumor-suppressor genes. The targeted repair or inactivation of these damaged gene products may counteract the effects of these genetic events, reversing tumorigenesis and thereby serve as an effective therapy for cancer. However, because they are the result of many genetic events, the inactivation of no single mutant gene product may be sufficient to reverse cancer. Despite this caveat, compelling recent evidence suggests that there are circumstances when even the brief interruption of activation of a single oncogene can be sufficient to reverse tumorigenesis. Understanding how and when oncogene inactivation reverses cancer will be important in both defining the molecular pathogenesis of cancer as well as developing new molecularly based treatments.

Potential clinical application of antioncogene ribozymes for human lung cancer

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

Suppressing tumor progression of in vitro prostate cancer cells by emitted psychosomatic power through Zen meditation

Human prostate cancer PC3 cells were treated in vitro with psychosomatic power emitted by a Buddhist-Zen Master. A significant decrease of growth rate was observed as determined by MTT assay after 48 hours. These cells also had two- to three-fold higher levels of prostatic acid phosphatase (PAcP) activity, a prostate tissue-specific differentiation antigen. In addition, the treated cells formed fewer and smaller colonies in soft agar as compared with control cells, which displayed anchorage-independent growth. These observations provide insight into the suppressive effects of healing power through the practice of Buddhist-Zen meditation on tumor progression. The emitted bioenergy may be suggested as an alternative and feasible approach for cancer research and patient treatment.