Differential gene expression of transforming growth factors alpha and beta, epidermal growth factor, keratinocyte growth factor, and their receptors in fetal and adult human prostatic tissues and cancer cell lines

OBJECTIVES

Recent studies have shown that growth factors may play a role in the etiology of benign prostatic hyperplasia (BPH) and prostatic carcinoma. Several growth factors have been reported to be expressed by prostatic tissues, but these growth factors have never been examined in human fetal prostate and compared with adult prostates and cancer cell lines. The present study was designed to investigate the messenger ribonucleic acid (mRNA) expression of transforming growth factor (TGF)-alpha, TGF-beta 1, TGF-beta 2, TGF- beta 3, keratinocyte growth factor (KGF), epidermal growth factor (EGF), EGF receptor (EGF-R), and KGF receptor (KGF-R) in human fetal and adult prostatic tissues and cancer cell lines by reverse-transcriptase-polymerase chain reaction-(RT-PCR) using specific oligonucleotide primers.

METHODS

Total RNA was extracted from human fetal and adult prostates (BPH tissues) and cancer cell lines. The gene expression of these growth factors and their receptors was determined by RT-PCR using specific oligonucleotide primers.

RESULTS

The results of these experiments suggest that: (1) human fetal prostate expressed mRNA transcripts for TGF-alpha, TGF-beta 1, TGF-beta 2, TGF-beta 3, and EGF. However, KGF, KGF-R, and EGF-R mRNA were not expressed by human fetal prostate; (2) human adult prostate (BPH tissues) showed mRNA transcripts for all growth factors and their receptors except KGF-R; (3) human BPH-1 cell lines expressed mRNA transcripts for TGF-alpha, TGF-beta 1, TGF-beta 2, TGF-beta 3, EGF, and KGF-R, but not for EGF-R and KGF growth factors; (4) human primary prostate cancer cell line (ND-1) showed mRNA transcripts for all growth factors except EGF and KGF; and (5) human prostate cancer cell lines (LNCaP, DU-145, PC-3) expressed mRNA transcripts for all growth factors except KGF, which was absent in all cell lines. However, KGF-R mRNA was absent in the PC-3 prostate cancer cell line.

CONCLUSIONS

These results suggest that the differential gene expression for various growth factors and their receptors in human fetal and adult prostatic tissues and cancer cell lines may be important in understanding the role of these factors in the pathophysiology of prostatic diseases.

Alzheimer-associated presenilin-2 confers increased sensitivity to apoptosis in PC12 cells

Presenilin-2 is a gene of unknown function recently identified based upon linkage with some forms of familial Alzheimer's disease. To investigate potential effects of PS-2 on cell viability, rat pheochromocytoma (PC12) cells were stably transfected with cDNA constructs encoding either full-length human PS-2 or, for comparison, mouse Bcl-X(L). Overexpression of PS-2 conferred increased sensitivity to the apoptotic stimuli staurosporine and hydrogen peroxide. In contrast, Bcl-X(L) overexpression significantly reduced cell death induced by these stimuli. These results suggest that one function of PS-2 may involve modulation of cell viability.

Amplifications of oncogene erbB-2 and chromosome 20q in breast cancer determined by differentially competitive polymerase chain reaction

A new method of measuring gene copy number in small samples of DNA was used to measure amplification of the erbB-2 gene and of chromosome 20q in breast cancer. This method, termed 'differentially competitive polymerase chain reaction' (DC-PCR) combines the advantages of two other techniques for measuring amplification by PCR, namely differential PCR and competitive PCR. The DC-PCR methodology was evaluated for sensitivity and specificity by comparing amplification of erbB-2 measured by DC-PCR with that obtained by fluorescence in situ hybridization (FISH) for 42 cases or Southern blotting and/or slot blot analysis for 34 cases. There was over 90 percent concordance with both FISH and Southern blotting and/or slot blot analysis. DC-PCR was used to further characterize the newly described amplicon at chromosome 20q. By analyzing DNA from 10 breast cancer cell lines at 7 different loci, we identified a potential common region of amplification of approximately 5 centimorgans at chromosome 20q13 bordered by loci D20S52 and RMC20C100-S1. One hundred and seventeen cases of primary breast cancer were evaluated for amplification at these two loci. Amplification at one or more loci, defined as > 1.5 fold higher copy number than that of normal DNA, was found in 25 cases (21%). Sixteen cases were amplified at only one of the two probes (12 cases for RMC20C001-S1 and 4 cases for D20S52), suggesting that the target gene lies between the two markers or that there are two independent target genes within a small chromosome region.

Gene expression of Alzheimer-associated presenilin-2 in the frontal cortex of Alzheimer and aged control brain

The presenilin-2 (PS2) gene expression pattern in Alzheimer's disease (AD) and control brains was examined using nonradioactive in situ hybridization. Message for PS2 was primarily detectable in neurons, particularly in somal cytoplasm. Intense staining signal was most commonly found in large pyramidal neurons, whereas moderate or faint staining was usually present in smaller neurons. The pattern of PS2 gene expression exhibited a laminar distribution profile in the frontal cortex. A small subset of tangle-bearing neurons exhibited PS2 hybridization signal in AD. PS2 mRNA expression appeared correlated to a high degree with lipofuscin autofluorescence in a large subset of neurons.

Is plasminogen activator inhibitor-1 the molecular switch that governs urokinase receptor-mediated cell adhesion and release?

Induction of the urokinase type plasminogen activator receptor (uPAR) promotes cell adhesion through its interaction with vitronectin (VN) in the extracellular matrix, and facilitates cell migration and invasion by localizing uPA to the cell surface. We provide evidence that this balance between cell adhesion and cell detachment is governed by PA inhibitor-1 (PAI-1). First, we demonstrate that uPAR and PAI-1 bind to the same site in VN (i.e., the amino-terminal somatomedin B domain; SMB), and that PAI-1 competes with uPAR for binding to SMB. Domain swapping and mutagenesis studies indicate that the uPAR-binding sequence is located within the central region of the SMB domain, a region previously shown to contain the PAI-1-binding motif. Second, we show that PAI-1 dissociates bound VN from uPAR and detaches U937 cells from their VN substratum. This PAI-1 mediated release of cells from VN appears to occur independently of its ability to function as a protease inhibitor, and may help to explain why high PAI-1 levels indicate a poor prognosis for many cancers. Finally, we show that uPA can rapidly reverse this effect of PAI-1. Taken together, these results suggest a dynamic regulatory role for PAI-1 and uPA in uPAR-mediated cell adhesion and release.

P53 tumour-suppressor gene mutations are mainly localised on exon 7 in human primary and metastatic prostate cancer

Mutations in the p53 tumour-suppressor gene are among the most common genetic alterations in human cancers. In the present study we analysed the mutations in the p53 tumor-suppressor gene in 25 primary and 20 metastatic human prostate cancer specimens. DNA extracted from the paraffin-embedded sections was amplified by hot-start polymerase chain reaction, and p53 gene mutations in the conserved mid-region (exons 4-9) were examined using single-strand conformation polymorphism (SSCP) analysis and immunohistochemistry. In the present study, we used a novel hot-start PCR-SSCP technique using DNA Taq polymerase antibody, which eliminates primer-dimers and non-specific products. Because of this new technique, the results of PCR-SSCP showed very high resolution. Polymerase chain reaction products were sequenced directly for point mutations for the p53 gene. Mutations were found in 2 out of 25 primary prostate cancers (8%) and 4 out of 20 metastatic cancers (20%). Mutations were observed exclusively in exon 7 and not in exons 4, 5, 6, 8 or 9. Nuclear accumulation of p53 protein, determined by immunohistochemistry, correlated with the degree of metastasis in prostatic cancer.

Structural and functional analysis of the plasminogen activator inhibitor-1 binding motif in the somatomedin B domain of vitronectin

Plasminogen activator inhibitor 1 (PAI-1) binds to the somatomedin B (SMB) domain of vitronectin (VN), a domain present in at least seven other proteins. In this study, we investigate the PAI-1 binding activity of these SMB homologs and attempt to more specifically localize the PAI-1 binding site within this domain. SMBVN and several of its homologs were expressed in Escherichia coli, purified, and tested for PAI-1 binding activity in a competitive ligand binding assay. Although recombinant SMBVN was fully active in this assay, none of the homologs bound to PAI-1 or competed with VN for PAI-1 binding. These inactive homologs are structurally related to SMBVN, having 33-45% sequence identity and containing all 8 cysteines at conserved positions. Thus, homolog-scanning experiments were conducted by exchanging progressively larger portions of the NH2- or COOH-terminal regions of active SMBVN with the corresponding regions of the inactive homologs. These experiments revealed that the minimum PAI-1-binding sequence was present in the central region (residues 12-30) of SMBVN. Alanine scanning mutagenesis further demonstrated that each of the 8 cysteines as well as Gly12, Asp22, Leu24, Try27, Tyr28, and Asp34 were critical for PAI-1 binding and were required to stabilize PAI-1 activity. These results indicate that the PAI-1 binding motif is localized to residues 12-30 of SMBVN and suggest that this motif is anchored in the active conformation by disulfide bonds.

Effect of two new polysaccharides on growth, agglomeration and zeta potential of calcium phosphate crystals

PURPOSE

To study the effect of semisynthetic sulphated polysaccharides in the different calcium phosphate crystallization processes in vitro.

MATERIALS AND METHODS

Crystallization of hydroxyapatite (HAP) and brushite (DCPD) in the presence and absence of 2 new semisynthetic sulphated polysaccharides (G871, G872) were defined by a constant composition technique, particle size analysis and zeta potential measurement.

RESULTS

These polysaccharides demonstrated strong inhibitory effect on HAP and DCPD crystal growth and agglomeration. The increase of negative zeta potential values after addition of polysaccharides suggests the binding of these polysaccharides to HAP and DCPD crystals.

CONCLUSION

We conclude that both G871 and G872 could be of potential use for calcium phosphate urolithiasis prevention in addition to their use for calcium oxalate.

Pleiotropic effects of Bcl-2 on transcription factors in T cells: potential role of NF-kappa B p50-p50 for the anti-apoptotic function of Bcl-2

Bcl-2 functions to repress apoptosis by regulation of genes which encode proteins required for programmed cell death and by interference with peroxidative damage. We investigated the interrelationship between expression of bcl-2 and regulation of transcription factor DNA binding activities in the 2B4 T cell hybridoma and IL-2-dependent CTLL T cell line. Over-expression of bcl-2 in 2B4 resulted in enhanced basal levels of activator protein (AP)-1, octamer binding factor (Oct)-1, lymphoid enhancer binding factor (LEF)-1, RelA-p50 and NF-kappa B p50-p50 DNA binding activities. After apoptotic signaling, down-regulation of AP-1, NF-AT and Oct-1 binding activities was observed in control 2B4 and CTLL, whereas suboptimal, but higher, levels of these transcription factors were found in bcl-2-transfected cells, potentially promoting cell survival. Furthermore, after apoptotic signaling, expression of bcl-2 led to differential changes of NF-kappa B levels, resulting in a decrease in RelA-p50 and an increase in NF-kappa B p50-p50, altering the ratio of these DNA binding activities such that now p50-p50 markedly predominated in both 2B4-Bcl-2 and CTLL-Bcl-2. Apoptotic signaling in the presence or absence of Bcl-2 resulted in induction of the RelB-p50 heterodimer in 2B4. The changes in NF-kappa B/Rel levels raise the possibility that this family of transcription factors may play an important role in the regulation of apoptosis.

[Experimental study and clinical application of rapid diagnosis of systemic candida albicans infection in burns by polymerase chain reaction]

For rapid diagnosis of systemic candidiasis, the polymerase chain reaction (PCR) was used to amplify a segment of Candida albican DNA coding for the cytochrome P450 L1 A1 in vitro. The technique provided unambiguous evidence of the presence of Candida albicans in as short as 8 hours with a detection threshold of 20 organisms. 200 blood and 120 urine specimens were collected from thirty rabbits with burn and candidiasis. Specimens of blood (n = 6), urine (n = 6), sputum (n = 7) and wound exudate (n = 7) were also collected from eight serious burn patients. PCR technique was used in all the specimens, and the result was compared with conventional fungus culture. It was shown that: (1) The positive detection rate of Candida by PCR was significantly higher than by culture for blood specimens (P < 0.01) and serial specimens of urine (P < 0.05) in infected burn animals. The clinical specimens showed the same results; (2) In evaluating diagnostic value of PCR for systemic Candida albicans infection, it was found that sensitivity, accuracy and negative prediction rate were superior to the conventional culture method. These results suggest that PCR technic may provide a rapid sensitive and specific means for the diagnosis of systemic Candida albicans infection. In addition, it may be helpful in the evaluation of therapeutic response or recurrence of infection.

Selective cell culture of primary breast carcinoma

We have used culture conditions which simulate the microenvironment of breast tumors for the isolation and propagation of primary breast tumor cells in vitro. In this monolayer setup, the mixture of cells dissociated from primary breast tumors is subjected to self-created gradients of oxygen and nutrients as well as metabolic waste and extracellular pH. The tumor populations isolated under these novel conditions have displayed phenotypic properties characteristic of breast carcinomas, including homogeneous expression of cytokeratin 19, and increased mitochondrial retention of the cationic dye rhodamine 123. Nonmalignant cultures from reduction mammoplasty were unable to survive these conditions. One tumor population which reached passage 10 was aneuploid for chromosomes 15 and 17, and displayed a p53 mutation in exon 8. These studies strongly suggest that the culture conditions described here can suppress the growth of normal breast cells, thereby allowing selective isolation of some populations of slow-growing primary tumor cells in vitro.

Deoxyribonuclease induction in apoptotic cytotoxic T lymphocytes

IL-2-dependent CTLL2 cells, upon IL-2 deprivation, die by apoptosis, which is accompanied by the fragmentation of genomic DNA. Two major deoxyribonuclease activities were detected in the extract of IL-2-deprived CTLL2 cells in a zymographic assay. They were designated nuc-58 and nuc-40, based on their apparent molecular mass of 58 and 40 kDa. The activity of both DNases was greatly induced in CTLL2 cells deprived of IL-2 or treated with the kinase inhibitor staurosporine. Deregulated expression of bcl-2 cDNA suppressed the induction of both nuclease activities. Nuc-58 was dependent on both Ca2+ and Mg2+ ions alone. Nuc-40 showed a preferential nuclear localization over that of nuc-58, which was found primarily in the cytoplasm. Optimal activity of both DNases required neutral pH and was inhibited by zinc ions. The physicochemical characteristics of the nucleases indicate that they are novel DNases associated with apoptosis in CTLL2 cells.

The study of logarithmic image processing model and its application to image enhancement

Describes a new implementation of Lee's (1980) image enhancement algorithm. This approach, based on the logarithmic image processing (LIP) model, can simultaneously enhance the overall contrast and the sharpness of an image. A normalized complement transform has been proposed to simplify the analysis and the implementation of the LIP model-based algorithms. This new implementation has been compared with histogram equalization and Lee's original algorithm.

An amplifiable DNA region from the Mycoplasma hyorhinis genome

A novel amplifiable genomic region that displays variability in the number of tandem copies of a 1,368-bp DNA sequence (designated RS-2) was discovered among individual clonal derivatives within Mycoplasma hyorhinis broth-grown cell populations. Clonal isolates representing variant subpopulations from the original broth culture were of a single size variant, and although continued culture under a variety of growth conditions did not result in further amplification of RS-2, evidence for deletion events which reduced RS-2 copy number, presumably by homologous recombination, was obtained. RS-2 homologous sequences were identified in all M. hyorhinis strains tested, but only the tissue culture-derived strains GDL-1 and GDL-2 showed variability in genomic dosage. The RS-2 nucleotide sequence established that each tandem copy is flanked by direct repeats of a 20-bp sequence and suggested a possible mechanism for its original duplication as the initial phase of a genetic amplification process. The coding strand was defined by PCR amplification of a reverse transcriptase-generated cDNA, and its sequence revealed that RS-2 encodes a 456-residue internal, highly cysteine-rich domain of a larger M. hyorhinis protein whose coding sequence initiates and terminates in unique genomic sequences several hundred base pairs from RS-2 on either side of it. Changes in RS-2 copy number maintain the reading frame, and therefore the coding capacity, for this predicted size-variant protein.

Fine needle aspiration techniques for the characterization of breast cancers

Fine needle aspiration biopsy (FNAB) is a well established method for diagnosing breast lesions, including cancers. FNAB does not require surgery and uses only a small amount of material. FNAB can also be used to acquire material for special studies. This is especially useful with small tumors (< or = 1 cm) when most of the material is needed to make a histologic diagnosis. Immunostaining techniques can be used on FNABs to investigate proliferation by bromodeoxyuridine uptake or Ki-67 labeling. Immunostaining techniques can also be used to identify oncoprotein expression, such as of p53. Fluorescence in situ hybridization is a technique that can be used to gather cytogenetic information directly from interphase tumor cells and is well suited for use with FNAB material because the harvested nuclei are intact and no cumbersome dissociation processing is needed. Flow cytometric techniques can be applied to FNAB material to study DNA content and S-phase fraction. Material acquired by FNAB can also be analyzed by the polymerase chain reaction followed by mutation detection. In this report, the authors show the applicability of these various analytic approaches to FNAB material from primary breast cancers. They show that it is essential that the FNAB harvest is representative, ample, and well prepared for the success of these studies.

Deletion of two separate regions on chromosome 3p in breast cancers

We have characterized the copy number of various loci on chromosome 3p in a series of breast cancers. To determine the precise region(s) involved, restriction fragment length polymorphism (RFLP) analysis for loss of heterozygosity (LOH) was performed using a panel of RFLP probes at 3p13-14, 3p21-22, and 3p24-26. The incidence of LOH at the three loci was 41, 32, and 45%, respectively. To validate the LOH data and to gain insights into the mechanisms resulting in LOH, chromosome 3 pericentromeric and 3p region-specific DNA probes were used to determine the DNA copy number by fluorescence in situ hybridization (FISH). Among 22 cases examined, 15 showed loss by both LOH and FISH, indicating that the dominant mechanism of LOH at 3p in breast cancer is a physical deletion. Two of the 22 cases showed loss by RFLP analysis but not by FISH, suggesting either mitotic recombination or loss and endoreduplication. In three cases, RFLP analysis indicated allelic imbalance, which was incorrectly interpreted as LOH, since a gain of one allele was suggested by FISH. By constructing a deletion map, we found that 2 separate regions, 3p13-14 and 3p24-26, were independently deleted in some breast cancers. Additionally, four cases had break points within the 3p24-26 region and one case had a homozygous deletion at 3p13, further supporting the hypothesis that there are tumor suppressor genes at both 3p13-14 and 3p24-26. Although high frequency of LOH was observed at the 3p21-22 region, there was no direct evidence supporting the existence of a breast cancer tumor suppressor gene there as opposed to codeletion with either the proximal or distal region.

The association of p53 immunopositivity with tumor proliferation and other prognostic indicators in breast cancer

Abnormal accumulation of the p53 tumor suppressor gene product was analyzed in 198 primary invasive human breast carcinomas. In 47 of these cases, single-strand conformational polymorphism was used to detect mutations in the highly conserved exons 5-9 of the gene. Mutations as determined by single-strand conformational polymorphism were found in 15 of 15 strongly immunopositive cases (100%) and 3 of 23 immunonegative cases (13%). There were also nine cases with < 1% immunopositive cells (borderline immunopositivity); p53 mutations were detected in seven of these cases. The results suggest that p53 immunopositivity is a highly specific, albeit somewhat insensitive surrogate for p53 mutations. p53 accumulation, detected by immunohistochemical methods using antibody PAb 1801, was noted in 29.8% of the cases and was associated with estrogen receptor (ER) negativity (P = 0.0003), progesterone receptor (PR) negativity (P = 0.008), and high histological grade (P = 0.037) by univariate analysis. Incorporation of bromodeoxyuridine was used to determine the percentage of cells synthesizing DNA (proliferative fraction). When bromodeoxyuridine was administered either in vivo (n = 93) or in vitro (n = 79), p53 accumulation was only marginally related to proliferative fraction (P = 0.067 by chi 2; P = 0.055 by Mann-Whitney). When tumors were segregated by ER status, the aforementioned associations of p53 immunopositivity with PR negativity, high histological grade, and increased proliferation rate lost their significance. p53 accumulation did not correlate with tumor size, clinical stage, axillary node metastases, or age at diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Physical deletion of the p53 gene in bladder cancer. Detection by fluorescence in situ hybridization

To understand better the role of physical p53 deletion in bladder cancer, 106 formalin-fixed and 45 unfixed bladder tumors were examined using fluorescence in situ hybridization. Probes for centromere 17 and the p53 locus were hybridized simultaneously to interphase tumor cells to analyze p53 and chromosome 17 copy number on a cell by cell basis. 17p deletion was found in four of 43 pTa tumors, 18 of 43 pT1 tumors and 29 of 58 pT2-4 tumors (P = 0.0001). 17p deletion was also highly correlated with grade (P = 0.0001) and with p53 immunostaining (P = 0.0005). Chromosome 17 polysomy was associated with stage, grade, 17p deletions, and p53 immunostaining (P = 0.0001). The strong difference in centromere 17 copy number and 17p deletions between pTa and pT1 tumors supports a relevant biological distinction between pTa and pT1 tumors.

A candidate tumor suppressor gene in human breast cancers

We have isolated a candidate gene (designated Brush-1) located at 13q12-q13, proximal to the retinoblastoma gene (RB1). Brush-1 codes for a 4.7-kilobase mRNA expressed at high levels in normal breast epithelium but drastically reduced in 6 of 13 breast cancer cell lines. RB1 mRNA expression is at normal levels for 5 of these 6 lines suggesting a greater importance of Brush-1 for breast cancer. Four primary breast tumors which showed no loss of heterozygosity in the 13q13-q14 region demonstrated normal levels of mRNA for both Brush-1 and RB1. However, four additional primary tumors which displayed loss of heterozygosity for this region had markedly decreased levels of Brush-1 mRNA while maintaining the normal levels for RB1. This differential loss of Brush-1 mRNA expression for both primary tumors and breast cancer cell lines is the expected pattern for a breast tumor suppressor gene.

Activation of oncogene c-Ha-ras in gastric cancer of Chinese patients

A transforming gene was cloned from a focus of rat fibroblast cell line Rat 1 transfected with DNA of a gastrocarcinoma cell line. The transforming gene is the activated form of oncogene c-Ha-ras, and the lesion was identified as a single nucleotide substitution at codon 12 by sequencing. We further used polymerase chain reaction (PCR)-restriction analysis to detect the mutations at codon 12 of c-Ha-ras. By using this method, 11 cases out of 24 solid tumors and 3 cell lines of gastric cancer were shown to contain mutations, and there was a strong correlation between mutations and metastasis and survival of the patients. The role of the activated c-Ha-ras in tumorigenesis of stomach cancer was further proved through the assay in which the malignant phenotypes of the c-Ha-ras-transformed cells were partially inhibited by blocking the c-Ha-ras expression with antisense oligonucleotides or exogenous plasmid expressing antisense RNA.

Loss of heterozygosity and p53 gene mutations in breast cancer

Immunopositivity for the p53 tumor suppressor gene product was evaluated in 133 breast cancers and compared to loss of heterozygosity (LOH) at various chromosomal loci. The validity of p53 immunopositivity as an indicator for p53 mutations was verified using two molecular assays of p53 mutations: single stranded conformational polymorphism (32 cases) and/or direct sequencing (14 cases). Immunopositivity was highly specific for mutations, since all of 15 strongly immunopositive tumors (> 10% of the cells are positive) and seven of nine cases with borderline immunopositivity had mutations by molecular analysis but were somewhat lower in sensitivity, p53 mutations being also detected in three of 23 (13%) immunonegative cases. LOH was measured at loci on the following chromosomes (1p,q; 2p; 3p; 7q; 11p,q; 13q; 16q; 17p; 18p,q; and 22q) by Southern blotting, polymerase chain reaction amplification of restriction fragment length polymorphisms, or repetitive cytidine and adenine stretches (CA repeats). There was no association between p53 mutations and one measure of genomic instability, namely, high incidence of overall LOH. In contrast, p53 mutations strongly associated with LOH at two specific loci, 3p24-26 (P < 0.001) and 7q31 (P < 0.05). There was no association between p53 mutations and LOH at 17p (site of the p53 gene), suggesting that breast cancers often have only one defective allele of the p53 gene.

Suppression of apoptosis in a cytotoxic T-cell line by interleukin 2-mediated gene transcription and deregulated expression of the protooncogene bcl-2

Absence of interleukin 2 (IL-2) from IL-2-dependent cells, such as the cytotoxic T-cell line CTLL2, causes DNA fragmentation and programmed cell death (apoptosis). We found that, upon initiation, DNA degradation proceeds rapidly. IL-2-deprived CTLL2 cells can be rescued from apoptosis by the addition of IL-2 2 h prior to the onset of detectable DNA breakdown. Addition of inhibitors of transcription with IL-2 abolished the IL-2-mediated rescue of CTLL2 cells. Thus it appears that IL-2-mediated gene transcription is necessary for survival. Deregulated expression of a protooncogene, bcl-2, inhibits apoptosis of cells dependent on other hematopoietic growth factors. To determine whether bcl-2 was active in CTLL2 cells, we transfected CTLL2 cells with a plasmid containing bcl-2 cDNA expressed under the metallothionein promoter and observed prolonged survival of the transfected cells upon IL-2 deprivation. Cell growth, however, was arrested in the G0/G1 or G2/M phases of the cell cycle. The prolonged survival of bcl-2 transfectants allowed the analysis of endogenous bcl-2 mRNA levels by Northern blot analysis. The expression of endogenous bcl-2 was down-regulated within 8 h of IL-2 withdrawal and was not detected after 3 days. Addition of IL-2 induced endogenous bcl-2 expression within 8 h. Full recovery of bcl-2 expression was achieved by 24 h after IL-2 addition. We conclude that the survival of death-prone CTLL2 cells may be viewed as IL-2-dependent suppression of suicide, probably by the IL-2-induced expression of the cellular bcl-2 gene.

Molecular aspects of early stages of breast cancer progression

It is clear that breast cancer progression is associated with inactivation of a number of different recessive oncogenes. The most widely evaluated tumor suppressor gene, p53, is mutated in approximately 30-50% of sporadic breast cancers. Mutations usually occur early in malignant progression. Loss of heterozygosity (LOH) studies have identified numerous chromosomal regions where other recessive oncogenes relevant to breast cancer may be located. Each LOH is seen in a varying proportion of breast cancers and may appear either early or late in progression. High-grade ductal carcinoma in situ (DCIS) and invasive carcinoma have similar genetic lesions, showing that aberrations can occur before invasive disease. Direct evidence that the same aberrations can be acquired later in progression comes from a study of multiple metastases from the same patient; other studies found that primary invasive cancers are characterized by marked intratumor heterogeneity for each lesion examined. The model we propose to account for these results hypothesizes that multiple genetic lesions can accomplish each phenotype required for malignancy (i.e., dysregulated proliferation, invasion, angiogenesis, etc.) and that, for a given tumor, at least one aberrant gene for each phenotypic change is stochastically selected. Biological heterogeneity of breast cancer results from the stochastic acquisition of various genetic aberrations. We further propose that the lymphocytic reaction in high-grade DCIS may select for aggressive tumor subpopulations capable of escaping immune surveillance. Another aspect of tumor heterogeneity may be the multiple mechanisms employed by various tumors to escape immune surveillance.

Transcriptional regulation of the human placental-like alkaline phosphatase gene and mechanisms involved in its induction by sodium butyrate

The human alkaline phosphatases constitute a multigene family with at least four members. Placental-like alkaline phosphatase (PLAP) is of particular interest because it is frequently present in tumors, where it serves as a marker of malignant transformation. Moreover, its expression is highly inducible by differentiating agents such as sodium butyrate. In the present study we have examined the PLAP gene promoter in order to better understand the mechanisms involved in its expression and induction. The PLAP promoters from four colon cancer cell lines with widely varied butyrate-inducible alkaline phosphatase activity were thermally amplified and sequenced. The overall sequence similarity of this region was found to be 99% between cell lines; thus, sequence variation of the promoter does not appear to account for the differential expression of this marker. We therefore analyzed the activity of the LS174T cell PLAP promoter using transient transfection experiments. Here, the 5'-flanking region of the gene was found to have positive regulatory elements in nucleotides -1 to -170 and -363 to -512 (relative to the start of transcription). A negative control element was also found to be present in the region between nucleotides -170 and -363. Mobility shift electrophoresis indicated that a nuclear factor bound to the promoter between bases -182 and -341. Furthermore, the activity of the PLAP promoter was found to be inducible by sodium butyrate. In contrast, the closely related placental alkaline phosphatase gene promoter exhibited almost no response to this agent. These results confirm that the activity of the PLAP promoter is stimulated by sodium butyrate and delineate regions that control this induction process.

An improved procedure for utilizing terminal transferase to add homopolymers to the 3' termini of DNA

Terminal deoxynucleotidyl transferase (E.C.2.7.7.3.1.) from calf thymus was used to add homopolymer tails to duplex DNA with 3' protruding, even, or 3' recessive ends. A gel electrophoresis method was employed to analyze the tail length and the percent of DNA with tails. In all the tailing reactions, dA, dT, and dC tails from CoCl2-containing buffer were longer than those from MnCl2 - or MgCl2 - containing buffers, whereas dG tails from MnCl2 -containing buffer were the longest. By varying the ratio of dNTP over DNA terminus and the concentration of terminal transferase, optimal conditions were found for adding dG or dC tails of 10-25 nucleotides in length and dA and dT tails of 20-40 nucleotides in length to duplex DNA with all types of 3' termini.