The molecular genetics of cancer

Suppression of genetic melanoma in the fish Xiphophorus

Hybrids between certain species of the teleost Xiphophorus predictably develop melanomas. Classical Mendelian crossing experiments have allowed us to identify genetic loci involved in eliciting and in suppressing tumorigenesis. The overall picture is that melanoma formation results from functional elimination of a suppressor locus allowing abnormal expression of a melanoma locus. Melanoma formation in Xiphophorus behaves like a recessive trait. The fish melanomas consist of incompletely differentiated pigment cells and in many aspects resemble their murine and human counterparts. Cytogenetic studies of cells of the genetic melanomas have provided evidence for chromosomal abnormalities. In particular, cytogenetic manifestations of amplified DNA were detected in a cell line derived from a malignant melanoma. Amplified DNA was isolated and was found to be amplified in a particular type of genetic melanoma. Our results suggest that genetic changes in addition to elimination of suppressor genes contribute to the malignant phenotype of melanoma in Xiphophorus. It is possible that a similar situation occurs in cancers of higher vertebrates, including humans.

Functional role of specific secreted and cell surface molecules in tumour cell invasion and metastasis

The invasion and metastatic spread of tumour cells are complex biological processes involving an array of cell surface and secreted protein molecules which function as specific recognition and catalytic agents in each step of the malignant cascade. In order to begin to identify these molecules and implicate them as true functioning agents, our laboratory has developed selected panels of monoclonal antibodies that have been screened for their ability to inhibit specific manifestations of the malignant phenotype in various model systems. Since monoclonal antibodies recognize only single and unique determinants, it is hypothesized that any monoclonal antibody which is specifically antifunctional will allow for the identification and isolation of relevant protein molecules.

fos-jun conspiracy: implications for the cell

Two nuclear oncoproteins, fos and jun (AP-1), cooperate in forming a very stable heterodimeric complex that binds to the AP-1 site on DNA with high affinity. The 'leucine zipper' domain of both fos and jun is necessary for the formation of this heterodimer. Mutations of single residues within the leucine zipper domain have no effect on protein complex formation. However, results from mutagenesis of the first leucine of the heptad repeat in either fos or jun basic regions and alteration of the spacing between the basic and leucine zipper domains indicate that the basic region of fos plays a crucial role in determining the DNA binding affinity of the transcriptional complex. Mutations of the basic amino acids in fos protein prevent binding to the tumour promoter response element (TRE) in the presence of wild-type jun protein. Thus fos protein appears to be dominant in jun-fos binding to DNA, even though fos alone cannot bind to TRE. Mutants in the basic region of fos and jun can be exploited as dominant-negative mutants to ablate the normal fos cellular function.

From Nutraceuticals to Pharmaceuticals to Nanopharmaceuticals: A Case Study in Angiogenesis Modulation During Oxidative Stress

This report reviews the potential applications of nanotechnology in various therapeutics and diagnostics areas with special emphasis on key frontiers in angiogenesis modulation using naturally driven drug targets including compounds that modulate oxidative stress and inflammatory pathways for the potential treatment of vascular, cancer, inflammatory, and ocular disorders. Recent advances of the nanotechnology mediated gene delivery are also described in this paper.

Detection of p53 Protein in Induced Sputum After Occupational Exposure to Crystalline Silica

OBJECTIVE

To examine the possibility of detecting p53 protein in the supernatant of induced sputum (IS) of workers exposed to crystalline silica.

METHODS

Personal interviews were used to obtain demographic data, occupational and exposure histories, and health habits of the study participants. Sputum samples were collected from all subjects.

RESULTS

The all-male study cohort included 35 workers (mean age 43.8 years) exposed to silica and 7 unexposed workers (34.7 years, P < 0.05). The mean duration of exposure was 13.4 years, and the range of exposure levels to silica was 0.02 to 0.33 ppm. The mean level of p53 protein was higher in the exposed group compared with in the unexposed group (76.47 pg/mL and 62.43 pg/mL, respectively).

CONCLUSIONS

p53 may serve as a biomarker to identify workers at high risk for developing pulmonary malignancies. IS can detect p53 protein in sputum.

Novel inhibitor for fibroblast growth factor receptor tyrosine kinase

NP603, the 6-dimethoxy phenyl indolin-2-one, was designed as FGF receptor 1 inhibitor by computational study. NP603 was synthesized and found to be more active against endothelial proliferation of HUVEC after the rhFGF-2 stimulation than SU6668 with minimum effective dose of 0.4 microM but with similar potency as SU16g. NP603 inhibited the tyrosine phosphorylation in FGF receptor and the activation of extracellular signal-regulated kinase and c-Jun-N-terminal-kinase after the rhFGF-2 stimulation. The increase in activity of NP603 supports the role of Lys514 movement in ligand-receptor binding in modeling study as the movement accommodates the hydrophobic interaction at the receptor pocket leading to the enhancement of binding capacity.

Assessment of Cell Proliferation in Benign, Premalignant and Malignant Skin Lesions

A deeper understanding of the variance of epidermal cell proliferation may eventually increase the reproducibility of diagnostic classification. A prospective study of 46 consecutive, unselected biopsies from benign (keratoacanthoma n=14), premalignant (actinic keratosis n=15 and Bowen disease n=10) and malignant (squamous cell carcinoma n=7) skin lesions was studied to assess the presence and extent of differences in expression of the proliferation marker Ki-67 using a monoclonal antibody directed against a c-DNA defined subsegment (MIB-1) and a noncross-linking, proprietary fixative BoonFix. MIB-1 was expressed in the adjacent, non-affected skin in a scattered to confluent linear pattern in the basal/suprabasal cell layer. In actinic keratosis, MIB-1 expression, in addition to basal/suprabasal layers, extended to mid-zones of the epidermis. An interesting feature in actinic keratosis as well as in Bowen disease was the expression of MIB-1 in the epithelium lining the hair follicles. In Bowen disease, MIB-1 was observed throughout the full thickness of the epidermis, unequivocally separating this entity from others under study. In invasive squamous cell carcinoma, MIB-1 expression was not consistent between and within cases. MIB-1 positivity was variably found in all layers of the epidermis, but showed a chaotic and haphazard pattern with total loss of polarity. Keratoacanthoma cases showed highly variable MIB-1 expression, ranging from no expression to expression in both basal/suprabasal and mid-zone layers of the epidermis. These results warrant further study of modulation of cell proliferation in actinic keratosis.

Colon cancer and gene alterations: their immunological implications and suggestions for prognostic indices and improvements in biotherapy

Studies have shown that changes occur in c-Ki-ras, p53, and Bcl2 gene structure and function during the various stages of human colon carcinogenesis. Alterations of these genes are responsible for the establishment of a state of continuous stimulus for cell division and apoptotic inhibition at physiological and pharmacological levels. This paper focuses on the results of our research aimed at investigating how these gene alterations influence tumoral mechanisms on an immunological level and how immunological parameters can be used as prognostic markers for the passage of normal tissue to adenoma and adenoma to carcinoma. Overall, our data suggest that an alteration in the c-Ki-ras gene results in a switch to a suppressive type of immune response, determining an impairment of immune cell activation at both antigen- presenting-cell and T-cell levels. c-Ki-ras gene mutations, p53 deletions, and Bc12 expression, on the other hand, can be used as prognostic markers for the passage of normal tissue to adenoma and adenoma to carcinoma. The p53 oncogene does not appear to impair patients' immunological response further. In conclusion, an evaluation of c-Ki-ras, rather than p53 gene alterations, would seem to be more relevant in colon cancer prevention programs and biotherapy improvement.

Point mutation in codons 12 and 61 of the Ha-ras gene in rat urinary bladder carcinomas induced by N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide

Male F344 rats were fed N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT) for up to 4 wk, then were given the basal diets (Prolab 3200 or AIN-76A) with or without 5% sodium saccharin for up to 100 wk. Eleven transitional cell carcinomas (TCCs), one undifferentiated carcinoma, and two sarcomas of the urinary bladder were examined for the expression of ras gene product, p21, by immunohistochemical staining and western blot analysis. Point mutation in codons 12 or 61 of the Ha-ras genes amplified by polymerase chain reaction was examined by a slot-blot screening procedure using allele-specific oligonucleotide probes. Immunohistochemical staining showed enhanced immunoreactivity with the antibody to ras p21 in seven TCCs and one undifferentiated carcinoma. Western blot analysis showed faster migration of the p21 band in 6 of 11 TCCs. Oligonucleotide hybridization revealed the point mutation in codon 12 of Ha-ras gene (GGA----GTA in 1 TCC) and in codon 61 (CAA----CGA in 5 TCCs and CAA----CTA in 1 TCC). Two mutations in codons 12 and 61 coexisted in one tumor, which were found to be present in different Ha-ras alleles. The incidence of Ha-ras gene mutations were similar in groups treated with (3 of 6) or without (3 of 8) sodium saccharin. These results suggest the involvement of activated Ha-ras gene in rat urinary bladder carcinogenesis induced by FANFT.

Distinct patterns of hypoxic expression of carbonic anhydrase IX (CA IX) in human malignant glioma cell lines

The hypoxia-inducible enzyme carbonic anhydrase IX (CA IX) has recently been discussed as a surrogate marker of tumor hypoxia, an indicator of prognosis and a potential therapeutic target in malignant glioma. To characterize patterns of expression of CA IX in human malignant glioma cells, we studied CA IX protein, CA9 mRNA and hypoxia-inducible factor-1alpha (HIF-1alpha) protein levels in U87-MG, U251, U373 and GaMG cells exposed to in vitro hypoxia (1, 6 or 24 h at 5%, 1% or 0.1% O(2)). All cell lines displayed a strong hypoxic induction of CA9 mRNA in response to prolonged severe hypoxia with cell-line specific patterns at moderate to mild hypoxia and shorter treatment times. Only U87-MG exhibited a strong constitutive, normoxic expression of CA IX protein without a detectable change under hypoxia. In U251 and GaMG cell lines, a marked induction of CA IX protein in response to severe hypoxia was seen. CA IX changes under severe hypoxia and the inhibitory effect of the glycolysis inhibitor iodoacetate (IAA, 50 microM) on hypoxic CA IX overexpression were paralleled by the results for HIF-1alpha protein. Therefore, immunohistochemical CA IX staining in human malignant glioma specimens can result from low oxygen concentrations or constitutive, oncogene-related, overexpression both of which may be prognostically relevant.

Multiple forms of genetic instability within a 2-Mb chromosomal segment of 3q26.3-q27 are associated with development of esophageal adenocarcinoma

Gene amplification is one of the mechanisms to activate oncogenes in many cancers, including esophageal adenocarcinoma (EA). In the present study, we used two-dimensional restriction landmark genome scanning to clone a NotI/DpnII fragment that showed increased genomic dosage in 1 of 44 EAs analyzed. This fragment maps to 3q26.3-q27, and subsequent experiments identified two intrachromosomal amplicons within a 10-Mb DNA segment in 7 of 75 (9%) EAs. The distal amplified-core region maps centromeric to the PIK3CA locus, and a microsatellite (D3S1754) within this region exhibited significant instability (MSI), in stark contrast to the genomewide microsatellite stability found in EA. D3S1754-MSI arises in premalignant Barrett's dysplastic cells and preceded amplification of the nascent MSI allele in the corresponding EA. Seven ESTs within the amplified-core were overexpressed in amplicon-containing EAs. One of these, EST AW513672, represents a chimeric transcript that initiated from an antisense promoter sequence in the 5'UTR of a full-length LINE-1 element (L1-5'ASP). Similar chimeric transcripts encoding portions of the MET oncogene and the BCAS3 gene also were overexpressed in EAs, suggesting that L1-5'ASP activation may occur at a broad level in primary EAs. Thus, the fine dissection of a 2-Mb amplified DNA segment in 3q26.3-q27 in EA revealed multiple genetic alterations that had occurred sequentially and/or concurrently during EA development.

Structural analysis of protein kinase A mutants with Rho-kinase inhibitor specificity

Controlling aberrant kinase-mediated cellular signaling is a major strategy in cancer therapy; successful protein kinase inhibitors such as Tarceva and Gleevec verify this approach. Specificity of inhibitors for the targeted kinase(s), however, is a crucial factor for therapeutic success. Based on homology modeling, we previously identified four amino acids in the active site of Rho-kinase that likely determine inhibitor specificities observed for Rho-kinase relative to protein kinase A (PKA) (in PKA numbering: T183A, L49I, V123M, and E127D), and a fifth (Q181K) that played a surprising role in PKA-PKB hybrid proteins. We have systematically mutated these residues in PKA to their counterparts in Rho-kinase, individually and in combination. Using four Rho-kinase-specific, one PKA-specific, and one pan-kinase-specific inhibitor, we measured the inhibitor-binding properties of the mutated proteins and identify the roles of individual residues as specificity determinants. Two combined mutant proteins, containing the combination of mutations T183A and L49I, closely mimic Rho-kinase. Kinetic results corroborate the hypothesis that side-chain identities form the major determinants of selectivity. An unexpected result of the analysis is the consistent contribution of the individual mutations by simple factors. Crystal structures of the surrogate kinase inhibitor complexes provide a detailed basis for an understanding of these selectivity determinant residues. The ability to obtain kinetic and structural data from these PKA mutants, combined with their Rho-kinase-like selectivity profiles, make them valuable for use as surrogate kinases for structure-based inhibitor design.

Knockdown of contactin-1 expression suppresses invasion and metastasis of lung adenocarcinoma

Numerous genetic changes are associated with cancer cell metastasis and invasion. In search for key regulators of invasion and metastasis, a panel of lung cancer cell lines with different invasive ability was screened. The gene for contactin-1 was found to play an essential role in tumor invasion and metastasis. Suppression of contactin-1 expression abolished the ability of lung adenocarcinoma cells to invade Matrigel in vitro as well as the polymerization of filamentous-actin and the formation of focal adhesion structures. Furthermore, knockdown of contactin-1 resulted in extensive inhibition of tumor metastasis and in increased survival in an animal model. RhoA but not Cdc42 or Rac1 was found to serve a critical role in contactin-1-mediated invasion and metastasis. Contactin-1-specific RNA interference resulted in loss of metastatic and invasive capacity in both in vitro and in vivo models. This loss was overturned by constitutive expression of the active form of RhoA. Contactin-1 was differentially expressed in tumor tissues, and its expression correlated with tumor stage, lymph node metastasis, and patient survival. Contactin-1 is proposed to function importantly in the invasion and metastasis of lung adenocarcinoma cells via RhoA-mediated mechanisms.

Activation of stat3 in primary tumors from high-risk breast cancer patients is associated with elevated levels of activated SRC and survivin expression

PURPOSE

Constitutive activation of signal transducer and activator of transcription 3 (Stat3) protein has been observed in a wide variety of tumors, including breast cancer, and contributes to oncogenesis at least in part by prevention of apoptosis. In a study of 45 patients with high-risk breast cancer enrolled in a phase II neoadjuvant chemotherapy trial with docetaxel and doxorubicin, we evaluated the levels of Stat3 activation and potentially associated molecular biomarkers in invasive breast carcinoma compared with matched nonneoplastic tissues.

EXPERIMENTAL DESIGN

Using immunohistochemistry and image analysis, we quantified the levels of phospho-Stat3 (pY-Stat3), phospho-Src (pY-Src), epidermal growth factor receptor, HER2/neu, Ki-67, estrogen receptor, Bcl-2, Bcl-xL, Survivin, and apoptosis in formalin-fixed, paraffin-embedded sections from invasive carcinomas and their paired nonneoplastic parenchyma. The levels of molecular biomarkers in nonneoplastic and tumor tissues were analyzed as continuous variables for statistically significant correlations.

RESULTS

Levels of activated pY-Stat3 and pY-Src measured by immunohistochemistry were significantly higher in invasive carcinoma than in nonneoplastic tissue (P < 0.001). In tumors, elevated levels of pY-Stat3 correlated with those of pY-Src and Survivin. Levels of pY-Stat3 were higher in partial pathologic responders than in complete pathologic responders. In partial pathologic responders, pY-Stat3 levels correlated with Survivin expression.

CONCLUSIONS

Our findings suggest important roles for elevated activities of Stat3 and Src, as well as Survivin expression, in malignant progression of breast cancer. Furthermore, elevated Stat3 activity correlates inversely with complete pathologic response. These findings suggest that specific Stat3 or Src inhibitors could offer clinical benefits to patients with breast cancer.

Transposable elements – Is there a link between evolution and cancer?

Currently, the most predominant theory concerning the formation of cancer is that it is a genetic accident. Accordingly, various agents are thought to cause DNA damage which then subsequently activates oncogenes and inactivates tumor suppressor genes. This article, however, describes a theory that interprets cancer as a misguided adaptation. Stressors, which cannot be compensated for with the usual cell possibilities might arouse evolutionary mechanisms intended to create new protein variants. One of these is the activation of transposable elements which leads to a reformatting of the genome. The result of this process is either a cell that survives very well under stress (and will, therefore, never be detected), a dead cell (in case the process is ineffective), or a more or less abnormal and harmful cell that builds up a new but cancerous organ. This theory explains the complex genetic alterations which are present in almost all cancer cells. It also explains the action of non-mutagenic carcinogens. As part of the reformatting process of the cancer cell genome, activation of oncogenes and inactivation of tumor suppressor genes are not stochastic events but the result of an unlucky genomic composition.

N4,N9-dioleoyl spermine is a novel nonviral lipopolyamine vector for plasmid DNA formulation

PURPOSE

To study the effect of synthesized N4,N9-dioleoyl spermine on DNA condensation and then measure its transfection efficiency in cell culture.

METHODS

The lipopolyamine was synthesized from the naturally occurring polyamine spermine. The ability of this novel compound to condense DNA was studied using ethidium bromide fluorescence quenching and light scattering assays. Transfection efficiency was studied in primary skin cells (FEK4) and in an immortalized cancer cell line (HtTA), and compared with the commercially available transfection formulations Lipofectin and Lipofectamine.

RESULTS

The synthesized N4,N9-dioleoyl spermine formula is efficient at condensing calf thymus and circular plasmid DNA and effectively transfects both primary skin cells and cancer cell lines at low charge ratios of (+/- ammonium/phosphate) 2.5.

CONCLUSIONS

N4,N9-Dioleoyl spermine condenses DNA and achieves high transfection levels in cultured cells.

Perinuclear localization of slow troponin C m RNA in muscle cells is controlled by a cis-element located at its 3' untranslated region

The process of mRNA localization within a specific cytoplasmic region is an integral aspect of the regulation of gene expression. Furthermore, colocalization of mRNAs and their respective translation products may facilitate the proper assembly of multi-subunit complexes like the thick and thin filaments of muscle. This postulate was tested by investigating the cytoplasmic localization of three mRNAs-the alpha-actin, slow troponin C (sTnC), and slow troponin I (sTnI), which encode different poly-peptide partners of the thin filament. Using in situ hybridization we showed that all three thin filament mRNAs are localized in the perinuclear cytoplasm of cultured C2C12 muscle cells. Their localization differs from that of the nonmuscle beta-actin mRNA, which is localized in the peripheral region of both proliferating nondifferentiated myoblasts and the differentiated myocytes. Analysis of the localization signal of the sTnC mRNA showed that a 40-nucleotide-long region of the sTnC mRNA 3' UTR is sufficient to confer the perinuclear localization on a heterologous reporter beta-Gal mRNA. This localization signal showed tissue specificity and worked only in the differentiated myocytes, but not in the proliferating myoblasts or in HeLa cells. The predicted secondary structure of the localization signal suggests the presence of multiple stem and loop structures in this region of the 3' UTR. Mutations within the stem region of the localization signal, which abolish the base pairing in this region, significantly reduced its perinuclear mRNA localization activity. Using UV-induced photo-cross-linking of RNA and proteins we found that a myotube-specific 42-kDa polypeptide binds to the localization signal.

Phenotypic characterization of chondrosarcoma-derived cell lines

Gene expression profiling of three chondrosarcoma derived cell lines (AD, SM, 105KC) showed an increased proliferative activity and a reduced expression of chondrocytic-typical matrix products compared to primary chondrocytes. The incapability to maintain an adequate matrix synthesis as well as a notable proliferative activity at the same time is comparable to neoplastic chondrosarcoma cells in vivo which cease largely cartilage matrix formation as soon as their proliferative activity increases. Thus, the investigated cell lines are of limited value as substitute of primary chondrocytes but might have a much higher potential to investigate the behavior of neoplastic chondrocytes, i.e. chondrosarcoma biology.

A novel gene amplification system in yeast based on double rolling-circle replication

Gene amplification is involved in various biological phenomena such as cancer development and drug resistance. However, the mechanism is largely unknown because of the complexity of the amplification process. We describe a gene amplification system in Saccharomyces cerevisiae that is based on double rolling-circle replication utilizing break-induced replication. This system produced three types of amplification products. Type-1 products contain 5-7 inverted copies of the amplification marker, leu2d. Type-2 products contain 13 to approximately 100 copies of leu2d (up to approximately 730 kb increase) with a novel arrangement present as randomly oriented sequences flanked by inverted leu2d copies. Type-3 products are acentric multicopy minichromosomes carrying leu2d. Structures of type-2 and -3 products resemble those of homogeneously staining region and double minutes of higher eukaryotes, respectively. Interestingly, products analogous to these were generated at low frequency without deliberate DNA cleavage. These features strongly suggest that the processes described here may contribute to natural gene amplification in higher eukaryotes.

Zinc-finger protein ZNF165 is a novel cancer-testis antigen capable of eliciting antibody response in hepatocellular carcinoma patients

ZNF165 is a zinc-finger protein gene that was identified from human adult testis. Analysis of the origins of publicly available expressed sequence tags as presented in Unigene and SAGE databases revealed that ZNF165 mRNA was expressed in tumours of different tissues. RT–PCR, real-time PCR and Northern blotting analysis confirmed that ZNF165 mRNA was expressed in the hepatocellular carcinoma, gastric cancer, colon cancer and non-small-cell lung carcinoma. The nucleotide sequence of ZNF165 expressed in tumours is identical to that expressed in the testis. Humoral responses of hepatocellular carcinoma (HCC) patients against ZNF165 protein were determined by Western blotting using the recombinant ZNF165 protein. Antibodies against ZNF165 protein were detected in approximately 5% (four of 82) of the sera from HCC patients. These results suggest that ZNF165, a member of the ZNF family, is a novel CT antigen capable of eliciting humoral immune response and be involved in tumour biology.

Functional characterization of peanut serine/threonine/tyrosine protein kinase: molecular docking and inhibition kinetics with tyrosine kinase inhibitors

Serine/threonine/tyrosine (STY) protein kinase from peanut is developmentally regulated and is induced by abiotic stresses. In addition, STY protein kinase activity is regulated by tyrosine phosphorylation. Kinetic mechanism of plant dual specificity protein kinases is not studied so far. Recombinant STY protein kinase occurs as a monomer in solution as shown by gel filtration chromatography. The relative phosphorylation rate of kinase against increasing enzyme concentrations follows a first-order kinetics indicating an intramolecular phosphorylation mechanism. Moreover, the active recombinant STY protein kinase could not transphosphorylate a kinase-deficient mutant of STY protein kinase. Molecular docking studies revealed that the tyrosine kinase inhibitors bind the protein kinase at the same region as ATP. STY protein kinase activity was inhibited by the tyrosine kinase inhibitors, and the inhibitor potency series against the recombinant STY protein kinase was tyrphostin > genistein > staurosporine. The inhibition constant (K(i)), and the IC(50) value of STY protein kinase for tyrosine kinase inhibitors with ATP and histone are discussed. All the inhibitors competed with ATP. Genistein was an uncompetitive inhibitor with histone, whereas staurosporine and tyrphostin were linear mixed type noncompetitive inhibitors with histone. Molecular docking and kinetic analysis revealed that Y148F mutant of the "ATP-binding loop" and Y297F mutant of the "activation loop" showed a dramatic increase in K(i) values for genistein and tyrphostin with respect to wild-type STY protein kinase. Data presented here provide the direct evidence on the mechanism of inhibition of plant protein kinases by tyrosine kinase inhibitors. This study also suggests that tyrosine kinase inhibitors may be useful in unraveling the plant tyrosine phosphorylation signaling cascades.

Systematic review of genetic influences on the prognosis of colorectal cancer

Background

In terms of genetics, colorectal cancer is one of the best understood of all malignant diseases. Genetic influences on prognosis may have far-reaching implications, especially for the design of surgical and chemoradiotherapeutic regimens. However, their significance in determining prognosis remains unclear. This study aimed to review the literature on the specific role of key genes in determining the survival of patients with colorectal cancer.

Methods

A Medline search was carried out to identify all original scientific papers relating colorectal cancer genetics to patient survival, up to December 2002. Cochrane and Embase databases were also searched. Identified articles were retrieved and searched carefully for additional information. This review includes K-ras, p53, DCC, NM23 and DNA mismatch repair genes.

Results and conclusion

Conflicting evidence exists as to the prognostic significance of genes commonly implicated in the pathogenesis of colorectal carcinoma. Possible causes for such discrepancy include differences in study methods and laboratory techniques, variable duration of follow-up, statistical differences in study power, and heterogeneity in study populations. Future studies should adopt standardized protocols to define clinically relevant genetic observations.

Frequent downregulation and loss of WWOX gene expression in human hepatocellular carcinoma

The WWOX (WW-domain containing oxidoreductase) is a candidate tumour suppressor gene spanning the same chromosome region, 16q23, as the second most common fragile site (FS), FRA16D. Deletions detected by comparative genomic hybridisation (CGH) and loss of heterozygosity at microsatellite markers on chromosome 16q are common in many human cancers including hepatocellular carcinoma (HCC). The development of human HCC is closely associated with exposure to oncogenic viruses and chemical carcinogens, agents known to frequently target common FS. We examined the status of WWOX genomic DNA, RNA and protein in 18 cell lines derived from human HCC and found recurrent alterations of the gene. Loss of DNA copy-number confined to band 16q23 was detected by CGH in several cell lines. Although homozygous deletions of the WWOX gene were not detected, WWOX mRNA expression was absent or lower in 60% of cell lines. The occurrence of aberrant WWOX reverse transcription–PCR products with deletion of exons 6–8 correlated significantly with altered WWOX expression. All of the cell lines showing mRNA downregulation had a decreased or undetectable level of WWOX protein as demonstrated by Western blotting with antibody to WWOX. Furthermore, 13 out of the 18 cell lines expressed decreased levels or no WWOX protein when compared with normal liver. These results show that WWOX gene is frequently altered in HCC and raise the possibility that this gene is implicated in hepatocarcinogenesis.

SMAD5 gene expression, rearrangements, copy number, and amplification at fragile site FRA5C in human hepatocellular carcinoma

Signaling by the transforming growth factor (TGF)-family members is transduced from the cell surface to the nucleus by the Smad group of intracellular proteins. Because we detected alterations on the long arm of chromosome 5, we examined the status of the SMAD5 gene in human hepatocellular carcinoma (HCC) cell lines and primary HCC. In 16 cell lines, chromosome alterations of chromosome 5 were observed in nine cell lines by fluorescence in situ hybridization (FISH), and an increase in SMAD5 gene copy number relative to the ploidy level was found in eight lines. The breakpoints in unbalanced translocations and deletions frequently occurred near the SMAD5 locus, but apparently did not cause loss of SMAD5. In one cell line, where comparative genomic hybridization showed DNA copy number gain confined to the region 5q31, we detected by FISH high-level amplification of the SMAD5 gene located within the fragile site FRA5C. Semiquantitative polymerase chain reaction did not reveal changes in SMAD5 DNA levels in 15 of 17 primary HCC specimens. In 17 HCC cell lines, SMAD5 mRNA levels were either maintained or upregulated by an increase in gene dosage or another mechanism. Collectively, our results show that SMAD5 undergoes copy number gain and increased expression, rather than loss of expression, and therefore suggest that this gene does not act as a tumor-suppressor gene in HCC. The Hep-40 HCC cell line with high-level amplification and significant overexpression of SMAD5 may be useful in studying the interaction of SMAD5 with other genes.

Application of the micronucleus test to exfoliated epithelial cells from the oral cavity of beedi smokers, a high-risk group for oral cancer

The primary sites for occurrence of oral cancer include the buccal mucosa, tongue, alveolus, palate, lip and the floor of the mouth. In this study, an attempt was made to estimate the cytogenetic damage in different regions of the oral mucosa in people habituated to smoking beedi,which is one of the major forms of tobacco consumption in India and believed to be a major risk factor for oral cancer. By using the micronucleus assay on exfoliated cells from the buccal mucosa, palate and tongue of beedi smokers, we examined an early cellular response to the effect of beedi smoking. A total number of 50 randomly selected male subjects were included in the study. Case and control groups (smokers and non-smokers, respectively) comprised 25 subjects each. The difference in mean micronucleated cell count between cases and controls was significant (P <0.01) for buccal mucosa and palate, but not for tongue. The correlation between age and micronucleus cell count was weak for both cases (r=0.27) and controls (r=0.36).

The Runx genes: lineage-specific oncogenes and tumor suppressors

The Runx genes present a challenge to the simple binary classification of cancer genes as oncogenes or tumor suppressors. There is evidence that loss of function of two of the three mammalian Runx genes promotes cancer, but in a highly lineage-restricted manner. In human leukemias, the RUNX1 gene is involved in various chromosomal translocation events that create oncogenic fusion proteins, at least some of which appear to function as dominant-negative inhibitors of the normal gene product. Paradoxically, evidence is mounting that structurally intact Runx genes are also oncogenic when overexpressed. All the three murine genes act as targets for transcriptional activation by retroviral insertional mutagenesis, and the oncogenic potential of Runx2 has been confirmed in transgenic mice. Moreover, the RUNX1 gene is often amplified or overexpressed in cases of acute leukemia. The state of progress in elucidating the oncogenic roles of the Runx genes is the subject of this review, and we draw together recent observations in a tentative model for the effects of Runx deregulation on hematopoietic cell differentiation. We suggest that lineage-specific factors determine the sensitivity to the oncogenic effects of loss or overexpression of Runx factors.

Testicular Activity of Mos in the Frog, Rana esculenta: A New Role in Spermatogonial Proliferation1

Mos is a MAPK kinase kinase with an expression that is highly restricted to the gonads. Its function is mainly associated to the meiotic metaphase II arrest occurring during female gametogenesis, whereas to our knowledge, its role during spermatogenesis has not yet clarified. In the present paper, we report the isolation of c-mos cDNA and the identification of a 60-kDa Mos protein from the testis of the anuran amphibian, Rana esculenta. Both the transcript and the protein are always present at low levels in the testis during the frog annual sexual cycle, with single significant peaks of expression in March and May, respectively. Mos is mainly localized in the cytoplasm of primary and secondary spermatogonia (SPG). Therefore, we have used treatments with ethane-dimethane sulphonate (EDS), which blocks spermatogonial mitosis in frogs. Four days after a single EDS injection, Mos expression in SPG highly increases concomitantly with the temporary arrest of mitosis. From 8 to 28 days after the injection, the normal proliferative activity of SPG is restored, and Mos expression gradually decreases to control levels. These results strongly indicate that the c-mos proto-oncogene exerts a new role associated to the regulation of spermatogonial proliferation.

LFIRE-1/HFREP-1, a liver-specific gene, is frequently downregulated and has growth suppressor activity in hepatocellular carcinoma

We have previously identified several novel genes, which are differentially expressed among human normal liver and hepatocellular carcinomas (HCCs). The full-length liver fibrinogen-related gene-1 (LFIRE-1) cDNA was cloned from the human normal liver cDNA library. LFIRE-1 is highly homologous to HFREP-1 with discrepancy at 5' untranslated region (UTR) and encodes the same fibrinogen-related protein, which suggest that these two sequences might be alternative splicing forms of the same gene, LFIRE-1/HFREP-1, located at human chromosome 8p22. The LFIRE-1 and HFREP-1 are specifically expressed in normal human liver tissue, but reduced or undetectable in most of HCC specimens at both RNA and protein level. Furthermore, the reduction or nonexpression of LFIRE-1/HFREP-1 is significantly associated with the degree of tumor differentiation. Loss of heterozygosity (LOH) analysis revealed allelic loss of LFIRE-1/HFREP-1 on chromosome 8p22 in 57.1% (24/42) of HCC specimens. We detected three inactivation mutations among 45 cases of HCC specimens examined, two of which lost the remaining allele and the third had a replacement of conserved cysteine residue with glycine residue. Notably, the downregulation of LFIRE-1/HFREP-1 expression is frequently associated with allelic loss. The reduction of LFIRE-1/HFREP-1 expression by antisense approach enhances cancer cell proliferation and colony formation in soft agar. Moreover, restoration of exogenous wild-type LFIRE-1/HFREP-1 expression but not LFIRE-1/HFREP-1 missense mutations in human HCC cells inhibited their anchorage-dependent or -independent growth in vitro, and suppressed their tumorigenicity in nude mice. In conclusion, our data demonstrated that liver-specific gene LFIRE-1/HFREP-1 was frequently downregulated and might possess growth suppressor activity in HCC.

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.

Suicide gene therapy in liver tumors

Charaterization of a variety of genomic defects in malignant cells (1) has led to attempts to treat cancer by gene therapy. Gene therapy is a therapeutic approach in which therapeutic nucleic acids are transferred into the affected organs. Although the ideal concept would be the replacement of the abnormal gene by a copy of the functional gene, currently there have not been reliable and safe techniques to allow the site-specific integration of DNA into the human genome (2). Thus, almost all gene therapies are developed by simply transferring the therapeutic gene into somatic cells without replacing the abnormal gene. The goal is to identify and correct genetic abnormalities interfering with the cell cycle and to correct them in all cells. Technically, there are two methods amenable for gene transfer: reintroduction of in vitro transferred gene into the body and direct transfer of gene into the target cells in vivo.

HCRP1, a novel gene that is downregulated in hepatocellular carcinoma, encodes a growth-inhibitory protein

One of the most frequent allelic deletions in hepatocellular carcinoma (HCC) has been found at chromosome 8p21-23. We reported here the identification and characterization of a novel gene for a hepatocellular carcinoma related protein 1 (HCRP1) localized at 8p22, which was isolated by positional candidate cloning. The expression of the gene for HCRP1 was most abundant in normal human liver tissue and significantly reduced or undetected in HCC tissues. The analysis of subcellular distribution showed that HCRP1 diffused in the cytoplasm with a significant fraction accumulated in the nuclei. After introduction of the sense and antisense cDNA of HCRP1 into HCC cell line SMMC-7721, we observed that the overexpression of HCRP1 significantly inhibited both anchorage-dependent and anchorage-independent cell growth in vitro. Using the transgenic short hairpin RNA (shRNA) to knock down the expression of HCRP1 gene in the other HCC cell line BEL-7404 resulted in the cell growth greatly enhanced. Moreover, reduction of the HCRP1 gene expression could also elevate the invasive ability of BEL-7404 cells. Our results strongly suggest that HCRP1 might be a growth inhibitory protein and associated with decreasing the invasion of HCC cells.

Development and validation of a real-time PCR assay for the detection and quantitation of p53 recombinant adenovirus in clinical samples from patients treated with Ad5CMV-p53 (INGN 201)

The purpose of this study was to assess the usefulness of real-time PCR as a quantitative, highly reproducible, and sensitive method, for detecting and quantifying p53 recombinant adenovirus in biological samples from cancer patients receiving injections of Ad5CMV-p53. The dynamic range of this real-time PCR-based assay was wide (at least five orders of magnitude). Our assay used an internal positive control in the same PCR tube that is capable of detecting residual PCR inhibitors. Serial spiked samples in plasma with known quantities of Ad5CMV-p53 were evaluated. The minimum detection limit was 2 pfu per PCR (approximately 50 pfu per ml of plasma) and the quantification values were reproducible. A total of 2069 controls tested with 1780 plasma samples from 286 patients enrolled in gene therapy trials using Ad5CMV-p53 were investigated. Using calibrators to adjust the quantitation value, the results confirmed the good performance of the assay. In conclusion, the high sensitivity, simplicity and reproducibility of the real-time Ad5CMV-p53 assay, allowing screening of large numbers of samples, combined with its wide dynamic range, make this method particularly suitable for monitoring gene therapy trials.

Cooperative roles of Fyn and cortactin in cell migration of metastatic murine melanoma

Src family kinases are major regulators of various integrin-mediated biological processes, although their functional roles and substrates in cancer metastasis are unknown. We explored the roles of Src family tyrosine kinases in cell migration and the spread of K-1735 murine melanoma cell lines with low or high metastatic potential. Corresponding to elevated cell motility and spreading ability, Fyn was selectively activated among Src family kinases, and the cell motility was blocked by an inhibitor of Src family kinases. Significant tyrosine phosphorylation of cortactin, stable complex formation between activated Fyn and cortactin, and co-localization of cortactin with Fyn at cell membranes were all observed only in cells with high metastatic potential. Both integrin-mediated Fyn activation and hyperphosphorylation of cortactin were observed 2-5 h after stimulation in highly metastatic cells, and they required de novo protein synthesis. We demonstrate that cortactin is a specific substrate and cooperative effector of Fyn in integrin-mediated signaling processes regulating metastatic potential.

Simian virus 40 and its association with human lymphomas

Simian virus 40 (SV40) is a potent DNA tumor virus that is known to induce cancer in laboratory animals. The neoplasias induced by SV40 in animal models are brain cancers, mesothelioma, bone cancers, and systemic lymphomas. SV40 oncogenesis is mediated primarily by the viral large tumor antigen, which inactivates the tumor suppressor proteins p53 and pRb family members. Evidence indicates that SV40 is an emergent human pathogen and that a significant excess risk of SV40 is associated with primary human brain cancers, malignant mesothelioma, bone cancers, and non-Hodgkin's lymphoma. Therefore, the major types of tumors induced by SV40 in laboratory animals are the same as those human malignancies found to contain SV40 markers. Experimental and clinical data indicate that SV40 may be functionally important in the development of some of those malignancies. Recently, the Institute of Medicine of the National Academies concluded that SV40 infections could lead to cancer in humans under natural conditions (based on moderate strength biologic evidence). This review examines the data implicating SV40 in the pathogenesis of human lymphomas and discusses future directions to define the causative role for SV40 in these malignancies.

Cellular transformation by the HTLV-I Tax protein, a jack-of-all-trades

The human T-cell leukemia virus type I (HTLV-I) is an oncogenic retrovirus that is responsible for adult T-cell leukemia and a neurological disease, HTLV-I-associated myelopathy/tropical spastic paraparesis. HTLV-I encodes an oncogenic protein, Tax, which affects a variety of cellular functions prompting it to be referred to as a jack-of-all trades. The ability of Tax to both transcriptionally regulate cellular gene expression and to functionally inactivate proteins involved in cell-cycle progression and DNA repair provide the basis for Tax-mediated transformation and leukemogenesis. This review will concentrate on the effects of Tax on the dysregulation of the G(1)/S and G(2)/M checkpoints as well as the suppression of DNA damage repair leading to cellular transformation.

High susceptibility of p53 knockout mice to esophageal and urinary bladder carcinogenesis induced by N, N-dibutylnitrosamine

In human cancer, alterations in the p53 tumor suppressor gene are the most common genetic alterations. The aim of the present study was to detect sensitivity of the p53 (+/-) mice and their littermates p53 (+/+) mice to N, N-dibutylnitrosamine (DBN) carcinogenicity. In experiment 1, 6-7-week-old p53 (+/-) and p53 (+/+) mice were treated with 0, 0.025 and 0.05% DBN, respectively, in drinking water for 20 weeks. Esophageal squamous cell and urinary bladder transitional cell carcinomas (TCCs) and fibrosarcomas were found to be significantly increased in p53 (+/-) mice treated with doses of DBN compared to p53 (+/+) mice administered similar doses. In experiment 2, 6-7-week-old p53 (+/-) and p53 (+/+) mice were administered 0 or 0.05 % DBN in drinking water for 8 weeks. Immunohistochemical staining revealed a significant increase in numbers of p53 and bromodeoxyuridine (BrdU) positive cells in the esophageal and urinary bladder epithelia of DBN-treated p53 (+/-) mice compared to p53 (+/+) mice administered DBN. Molecular analysis revealed point mutations in the residual p53 allele in four of eight (50%) esophageal mucosa of DBN-treated p53 (+/-) mice, and in three of eight (38%) of treated p53 (+/+) mice. The results show that p53 (+/-) mice were sensitive to DBN treatment with respect to esophageal and bladder tumor development, with a mechanism that could be confined to early mutations of the residual p53 allele and increased cellular proliferation in the target organs.

Genetic alterations in cancer as a result of breakage at fragile sites

The organization and replication of DNA render fragile sites (FSs) prone to breakage, recombination as well as becoming preferential targets for mutagens-carcinogens and integration of oncogenic viruses. For many years, attempts to link FSs and cancer generated mostly circumstantial evidence. The discoveries that chromosome translocations, amplification of proto-oncogenes, deletion of tumor suppressor genes, and integration of oncogenic viruses all result from the specific breakage of genomic DNA at FSs, however, have provided compelling support for such a link, further suggesting a causative role for FSs in cancer.

Amplification and overexpression of the EMS 1 oncogene, a possible prognostic marker, in human hepatocellular carcinoma

DNA amplification in cancer cells frequently involves oncogenes whose increased expression confers a selective advantage on tumor cell growth. In an attempt to identify novel oncogenes involved in hepatocarcinogenesis, representational difference analysis (RDA) was performed using DNA from a primary human hepatocellular carcinoma (HCC) that showed high-level DNA amplifications on chromosomes 1p32 and 11q13 by comparative genomic hybridization. Ten amplification fragments were isolated by RDA, and when used to probe Southern blots of tumor DNA, there was a 5- to 50-fold increase in hybridization intensity relative to normal DNA. The sequence of one amplification product matched that of the EMS1 oncogene, which is located on chromosome 11q13 and is amplified in other cancers. We detected EMS1 amplification in 3 of 17 primary HCC. Overexpression of EMS1 mRNA was observed in 12 of 14 HCC cell lines in the absence of gene amplification or an increased copy-number of the gene. The EMS1 gene encodes cortactin, a cortical actin-associated protein that is a substrate for Src kinase and is involved in cytoskeleton organization. Alterations of the EMS1 gene that lead to overexpression of cortactin may be associated with tumor development in HCC. EMS1 amplification and overexpresion is indicative of unfavorable prognosis in several cancers and may have similar prognostic implications in liver cancer.

Tobacco smoking, harm reduction, and biomarkers

The only known way to reduce cancer risk in smokers is complete cessation, but many smokers are unable or unwilling to quit. Consequently, tobacco companies are now marketing products that purport to reduce carcinogen exposure, with the implication that such products provide a safer way to smoke. Moreover, researchers are exploring ways to reduce the amount of cigarette smoke carcinogens to which the smokers are exposed. Although these methods are, in theory beneficial, it is possible that the perceived availability of "safe" ways to smoke will cause some former smokers to resume smoking and some current smokers to delay quitting. Thus, the extent of exposure reduction and the impact on public health of these methods need to be considered carefully. However, risk reduction and its relation to exposure are not simple to estimate. The way people smoke and the way they respond to carcinogen exposure are both highly variable, as evidenced by the previous history of smokers who switched to light, or low-tar cigarettes. This can actually increase risk in some smokers. The evaluation of exposure reduction will therefore need to be multidisciplinary and include in vitro cell culture studies, animal studies, human clinical studies, and epidemiologic studies. Biomarkers will be critical for rapidly evaluating the effects of new strategies or products to reduce exposure to tobacco smoke carcinogens. No single biomarker will likely satisfy our assessment needs, and so a panel of biomarkers should be used that includes biomarkers of exposure, biologically effective dose, and potential harm. In addition, usefulness of new products will need to be tested in people of different susceptibilities (i.e., who vary in behavior, sex, age, genetics, and prior tobacco use). Even if the new products are shown to be effective at reducing lung carcinogens, they should not be used alone but rather be incorporated into a comprehensive tobacco control program.

Carcinogenicity of dimethylarsinic acid in male F344 rats and genetic alterations in induced urinary bladder tumors

Arsenic is a well-documented human carcinogen, and contamination with this heavy metal is of global concern, presenting a major issue in environmental health. However, the mechanism by which arsenic induces cancer is unknown, in large part due to the lack of an appropriate animal model. In the present set of experiments, we focused on dimethylarsinic acid (DMA), a major metabolite of arsenic in most mammals including humans. We provide, for the first time, the full data, including detailed pathology, of the carcinogenicity of DMA in male F344 rats in a 2-year bioassay, along with the first assessment of the genetic alteration patterns in the induced rat urinary bladder tumors. Additionally, to test the hypothesis that reactive oxygen species (ROS) may play a role in DMA carcinogenesis, 8-hydroxy-2'-deoxyguanosine (8-OHdG) formation in urinary bladder was examined. In experiment 1, a total of 144 male F344 rats at 10 weeks of age were randomly divided into four groups that received DMA at concentrations of 0, 12.5, 50 and 200 p.p.m. in the drinking water, respectively, for 104 weeks. From weeks 97-104, urinary bladder tumors were observed in 8 of 31 and 12 of 31 rats in groups treated with 50 and 200 p.p.m. DMA, respectively, and the preneoplastic lesion, papillary or nodular hyperplasias (PN hyperplasia), was noted in 12 and 14 rats, respectively. DMA treatment did not cause tumors in other organs and no urinary bladder tumors or preneoplastic lesions were evident in the 0 and 12.5 p.p.m.-treated groups. Urinary levels of arsenicals increased significantly in a dose-responsive manner except for arsenobetaine (AsBe). DMA and trimethylarsine oxide (TMAO) were the major compounds detected in the urine, with small amounts of monomethylarsonic acid (MMA) and tetramethylarsonium (TeMa) also detected. Significantly increased 5-bromo-2'-deoxyuridine (BrdU) labeling indices were observed in the morphologically normal epithelium of the groups treated with 50 and 200 p.p.m. DMA. Mutation analysis showed that DMA-induced rat urinary bladder tumors had a low rate of H-ras mutations (2 of 20, 10%). No alterations of the p53, K-ras or beta-catenin genes were detected. Only one TCC (6%) demonstrated nuclear accumulation of p53 protein by immunohistochemistry. In 16 of 18 (89%) of the TTCs and 3 of 4 (75%) of the papillomas, decreased p27(kip1) expression could be demonstrated. Cyclin D1 overexpression was observed in 26 of 47 (55%) PN hyperplasias, 3 of 4 (75%) papillomas, and 10 of 18 (56%) TCCs. As a molecular marker of oxidative stress, increased COX-2 expression was noted in 17 of 18 (94%) TCCs, 4 of 4 (100%) papillomas, and 39 of 47 (83%) PN hyperplasias. In experiment 2, 8-OHdG formation in urinary bladder was significantly increased after treatment with 200 p.p.m. DMA in the drinking water for 2 weeks compared with the controls. The studies demonstrated DMA to be a carcinogen for the rat urinary bladder and suggested that DMA exposure may be relevant to the carcinogenic risk of inorganic arsenic in humans. Diverse genetic alterations observed in DMA-induced urinary bladder tumors imply that multiple genes are involved in stages of DMA-induced tumor development. Furthermore, generation of ROS is likely to play an important role in the early stages of DMA carcinogenesis.

Damaged DNA and miscounted chromosomes: human T cell leukemia virus type I tax oncoprotein and genetic lesions in transformed cells

Genetic instability is a recurring theme in human cancers. Although the molecular mechanisms mediating this effect commonly observed in transformed cells are not completely understood, it has been proposed to involve either the loss of DNA repair capabilities or the loss of chromosomal stability. The transforming retrovirus human T cell leukemia virus type I (HTLV-I) encodes a viral oncoprotein Tax, which is believed to cause the genomic instability characteristic of HTLV-I-infected cells. This review focuses on the ability of HTLV-I Tax to disrupt the cellular processes of DNA repair and chromosomal segregation. The consequences of these effects as well as the evolutionary advantage this may provide to HTLV-I are discussed.

Frequent expression of new cancer/testis gene D40/AF15q14 in lung cancers of smokers

We found a significant correlation between lung cancer in smokers and the expression of a human gene, D40, predominantly expressed in testis and cancers. In an attempt to clone a novel human gene, we screened a cDNA library derived from a human B cell line and obtained a cDNA clone that we refer to as D40. A search for public databases for sequence homologies showed that the D40 gene is identical to AF15q14. D40 mRNA is predominantly expressed in normal testis tissue. However, this gene is also expressed in various human tumour cell lines and primary tumours derived from various organs and tissues, such as lung cancer. We examined the relationship between D40 expression and clinico-pathological characteristics of tumours in primary lung cancer. D40 expression did not significantly correlate with either histological type or pathological tumour stage. However, D40 expression was observed more frequently in poorly differentiated tumours than in well or moderately differentiated ones. Furthermore, the incidence of D40 expression was significantly higher in tumours from patients who smoke than in those from non-smokers. D40/AF15q14 is the first gene in the cancer/testis family for which expression is related to the smoking habits of cancer patients.