miRNAs and their role in the correlation between schizophrenia and cancer (Review)

Schizophrenia (SZ) and cancer (Ca) have a broad spectrum of clinical phenotypes and a complex biological background, implicating a large number of genetic and epigenetic factors. SZ is a chronic neurodevelopmental disorder signified by an increase in the expression of apoptotic molecular signals, whereas Ca is conversely characterized by an increase in appropriate molecular signaling that stimulates uncontrolled cell proliferation. The rather low risk of developing Ca in patients suffering from SZ is a hypothesis that is still under debate. Recent evidence has indicated that microRNAs (miRNAs or miRs), a large group of small non-coding oligonoucleotides, may play a significant role in the development of Ca and major psychiatric disorders, such as SZ, bipolar disorder, autism spectrum disorders, suicidality and depression, through their interference with the expression of multiple genes. For instance, the possible role of let-7, miR-98 and miR-183 as biomarkers for Ca and SZ was investigated in our previous research studies. Therefore, further investigations on the expression profiles of these regulatory, small RNA molecules and the molecular pathways through which they exert their control may provide a plausible explanation as to whether there is a correlation between psychiatric disorders and low risk of developing Ca.

The KLK5 protease suppresses breast cancer by repressing the mevalonate pathway

Kallikrein-related peptidase 5 (KLK5) displays aberrant expression in cancer. However, any functional association is missing. Here, we show that reconstitution of KLK5 expression in non-expressing MDA-MB-231 breast cancer cells suppresses malignancy in vitro and in vivo dose-dependently. Reactivation of KLK5 suppressed key EMT genes. Unexpectedly, we identified altered expression of genes encoding enzymes of the mevalonate pathway typical of those observed upon cholesterol starvation. Consistently, we found that SREBF1, the master regulator of the mevalonate pathway was induced. KLK5 re-expression leads to reduced cellular cholesterol and fatty acid synthesis and enhanced uptake of LDL-cholesterol. Suppression of the mevalonate pathway in KLK5 transfectants was further shown by reduced synthesis of isoprenoids. Indeed, we found diminished levels of active RhoA, a signaling oncoprotein that requires prenylation for activation. We propose that reduced RhoA activation plays a dominant role in suppression of malignancy by KLK5, since geranylgeranyl pyrophosphate restored active RhoA in KLK5-reverted cells resulting in increased malignancy. For the first time, we suggest that a protease may suppress breast cancer by modulating the mevalonate pathway.

Specific lipofuscin staining as a novel biomarker to detect replicative and stress-induced senescence. A method applicable in cryo-preserved and archival tissues

There is shortage of extensive clinicopathologic studies of cellular senescence because the most reliable senescence biomarker, the detection of Senescence-Associated-beta-galactosidase activity (SA-β-gal), is inapplicable in archival material and requires snap-frozen tissues. We validated the histochemical Sudan-Black-B (SBB) specific stain of lipofuscin, an aggregate of oxidized proteins, lipids and metals, known to accumulate in aged tissues, as an additional reliable approach to detect senescent cells independently of sample preparation. We analyzed cellular systems in which senescence was triggered by replicative exhaustion or stressful stimuli, conditional knock-in mice producing precancerous lesions exhibiting senescence, and human preneoplastic lesions known to contain senescent cells. In the above settings we demonstrated co-localization of lipofuscin and SA-β-gal in senescent cells in vitro and in vivo (cryo-preserved tissue), strongly supporting the candidacy of lipofuscin for a biomarker of cellular senescence. Furthermore, cryo-preserved tissues positive for SA-β-gal were formalin-fixed, paraffin-embedded, and stained with SBB. The corresponding SA-β-gal positive tissue areas stained specifically for lipofuscin by SBB, whereas tissues negative for SA-β-gal were lipofuscin negative, validating the sensitivity and specificity of the SBB staining to visualize senescent cells in archival material. The latter unique property of SBB could be exploited in research on widely available retrospective tissue material.

TGF-beta 1 overexpression in breast cancer

TGF-beta 1 belongs to a family of pluripotent growth factors (TGF beta s) and has been implicated in the development and progression of human breast cancer. There are conflicting data though, suggesting that TGF-beta has the pontency both to promote and inhibit the progression of mammary neoplasia. We examined the expression of TGF-beta 1 mRNA in 24 breast carcinomas using the technique of the reverse transcription polymerase chain reaction (RT-PCR) to obtain quantitative results. Overexpression of TGF-beta 1 gene was found in 75% of the cases. We also correlated the overexpression of the TGF-beta 1 gene with clinicopathological parameters including histological grade, tumour cellularity, oestrogen receptor status (ER), progesterone receptor status (PR) and lymph node involvement. The results led us to the conclusion that the increasing ratio of overexpression related to the stage of cancer in an analogous way (P similar to 1). No significant association was identified between the ratio of overexpression and the grade, ER, PR, or lymph node involvement (r(s) = 0.5, 0.2, 0.1, 0.1 respectively; P < 0.0001) in all categories.

Specific recognition of a transcriptional element within the human h-ras protooncogene by the p53 tumor-suppressor

The nuclear phosphoprotein p53 is frequently inactivated in human cancer. Although it was previously classified as an oncoprotein, p53 has emerged as a tumor suppressor controlling cell cycle progression by regulating gene transcription. A major biochemical property of wild-type p53 is its ability to bind DNA in a sequence-specific manner. The human c-H-ras gene contains within its first intron sequences that partially match the p53 consensus binding site. We determined that these sequences represent a bona fide p53 element, since in vitro translated wild-type p53 recognized them with high affinity. Furthermore, wild-type p53 activated transcription from a reporter plasmid containing the c-H-ras element as an enhancer. These findings suggest that p53 regulates cellular growth by coordinate transcription of genes that suppress and promote cellular proliferation.

Binding of the glucocorticoid and estrogen-receptors to the human h-ras oncogene sequences

There is evidence that hormone regulation of cellular oncogenes plays an essential role in human cancer. The c-H-ras gene is implicated through both mutation and abnormal gene expression in many types of human cancer. Computer scanning of this gene has revealed two putative hormone response motifs: A possible Glucocorticoid Response Element (GRE) at position 1261 of the first intron of the H-ras1 gene and a putative Estrogen Response Element (ERE), at position 3007 of the fourth intron of the gene. In DNA binding assays, using the HeLa and LATK-cell lines, we showed specific binding of the corresponding receptors at both putative H-ras glucocorticoid and estrogen response sequences, suggesting that hormones could be contributing to H-ras transcriptional regulation through interaction with their corresponding Hormone Response Elements (HREs).

Ap-1 recognizes sequence elements on hiv-1 LTR in human epithelial tumor-cell lines

Investigation of the nucleotide sequence of the HIV-1 LTR showed the presence of four novel short DNA regions which are homologous to the recognition site for the cellular transcription factor AP-1. Four short oligonucleotide hybrids containing these potential AP-1 sites were constructed and used in gel retardation assays and in competition experiments in order to determine the role of the AP-L protein in the regulation of HIV-1 expression. The breast MDA MB 468 and cervical HeLa turner cell lines, which are known to overexpress the AP-1 protein were used in a gel retardation assay as a control to study the affinity of the AP-1 to synthesized oligonucleotide sequences. We have observed specific binding of nuclear factor AP-1 to three of these oligonucleotide hybrids. These results demonstrate the presence of three novel AP-1 binding sites on HIV-1 LTR, one of which was found within the TAR element and in the Tat protein binding region. Moreover, they suggest that AP-1 could be contributing to HIV-1 transcriptional regulation through its interaction with the AP-1 binding sites of HIV-1 LTR.

miR-183 as a molecular and protective biomarker for cancer in schizophrenic subjects

Previous studies have suggested that schizophrenia is associ-ated with a reduced risk of cancer. Genes that are involved in cell cycle regulation seem to have additional functions in post-mitotic neurons involved in neuronal migration and synaptic plasticity. MicroRNAs (miRNAs) play a dominant role in the regulation of gene expression in the central nervous system (CNS). Due to their involvement in a large number of CNS pathways, miRNAs pose as appealing molecules for further investigation, with potential diagnostic, prognostic and therapeutic value. In the present study, we investigated the potential association between cancer and schizophrenia in 2 patient sample groups. We analyzed a large number of miRNAs in a control group of 6 schizophrenic patients and a study group of 8 schizophrenic patients with a solid tumor. A comparison between the control and study groups showed that only miR-183 was differentially expressed. Specifically, a significant downregulation of miR-183 in the samples of the study group was observed. Although a larger sample size is required to validate this result for the general patient population, our findings provide a first indication that miR-183 may play a role in regulating the expression of other genes with onco-suppressor activity. Our results are in agreement with the theory that patients with schizophrenia may have a tumor suppressor gene or enhanced neuronal apoptotic activities. Further studies are required in order to shed light on the role of miRNAs and particularly, on the suppressive role of miR-183 in the neurobiological pathways involved in schizophrenia.

Abstract 4916: Molecular basis for the concentration-dependent tumor suppressing effects of KLK6 in breast cancer

Human kallikrein-related peptidase 6 (KLK6) is a serine protease exerting versatile (patho)physiological functions (J Biol Chem 284:32989-32994, 2009). Recently, we showed that KLK6 acts as a tumor suppressor in human breast cancer. Interestingly, the tumor suppressing effects of KLK6 depend on its expression levels (Cancer Res 69:3779-3797, 2009). Namely, KLK6 re-expression at physiological levels (i.e. levels found in normal mammary cells and tissues) in KLK6-negative MDA-MB-231 breast cancer cells resulted in strong inhibition of tumor cell proliferation, anchorage-independent growth and cell motility, while it remarkably abolished their ability to form tumors in SCID mice. Contrary, when KLK6 was highly overexpressed (&gt;50-fold compared to normal cells) in MDA-MB-231 cells, its tumor suppressor activity in vivo was lost. Importantly, overexpression of KLK6 is a characteristic of a small subgroup of breast tumors. Here, we investigated molecular pathways underlying these concentration-dependent effects of KLK6 in breast cancer. In addition, we tested whether the enzymatic activity of KLK6 is required for the observed phenotypes or they may result from non-proteolysis-related protein-protein interactions. To address these questions we carried out genome-wide differential transcriptomic profiling using the Illumina bead microarrays. The profiles of KLK6-negative MDA-MB-231 parental cells was compared in parallel with three different MDA-MB-231 clones stably transfected with wt or mutant KLK6 cDNA, namely C28WT (expresses KLK6 at normal levels), C5WT (highly overexpresses KLK6) and C22MS (expresses a mutant form of KLK6 with a point substitution at the active site serine residue, i.e. S192A, that completely inhibits its protease activity). Detailed proteomic profiles were determined for all the aforementioned MDA-MB-231 clones using one-dimensional (1D) SDS-PAGE analysis of cell lysates, combined with in gel trypsin digestion and LC-ESI-MS/MS (liquid chromatography electrospray ionization tandem mass spectrometry). In all cases, we were able to identify in total 3779 cellular proteins with 2487 having ≥2 peptides distributed as: 1776 in parental, 2020 in C28WT, 1228 in C5WT and 1593 in C22MS. Hierarchical clustering proteome analysis clustered C22MS together with parental. Sorting the proteins relative to ≥4 fold-expression over parental resulted in identification of 377 proteins differentially expressed in C28WT, 449 in C5WT and 169 C22MS. The derived datasets were used to infer potential networks using Ingenuity Pathway Analysis (IPA). Important pathways (including NF-kB, TP53 and apoptosis-related) were found differentially deregulated upon KLK6 expression. For the first time, we describe KLK6-associated gene expression signatures and proteomes that were integrated in an effort to derive putative pathways underlying the emerging role(s) of KLK6 in breast cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4916. doi:1538-7445.AM2012-4916

Abstract 4125: Suppression of the mevalonate pathway and oncogenic signaling may underlie the tumor-suppressing effects of KLK5 in breast cancer

Kallikrein-related peptidase 5 (KLK5) has been implicated in different types of cancer based on its aberrant expression in tumor cell lines and tissue specimens and in vitro data, however, functional association is missing. Here, we confirmed that KLK5 is very frequently down-regulated or inactivated in breast cancers of different subtypes. Reconstitution of KLK5 expression by stable transfection in KLK5-negative MDA-MB-231 cells remarkably reversed their malignant phenotype both in vitro (wound scratch and soft agar assay) and in vivo (orthotopic xenograft growth in SCID mice). We found that in KLK5 transfectants Snail1 and the mesenchymal marker vimentin were highly downregulated, pointing to a potential involvement of KLK5 in mesenchymal-to-epithelial transdifferentiation, however, re-expression of E-cadherin could not be demonstrated. Importantly, it appears that KLK5 may severely affect the overall output of the proteolytic web as it minimized the proteolytic activities of MMP9 and MMP3. Unexpectedly, transcriptomic profiling revealed that reconstitution of KLK5 expression suppresses the mevalonate pathway of cholesterol biosynthesis by highly up-regulating INSIG1 (insulin induced gene 1), a major negative regulator of HMGCR (3-hydroxy-3-methylgluratyl-CoA reductase), while KLK5 may also affect cholesterol uptake, as the LDLR (LDL receptor) and PCSK9 (proprotein convertase subtilisin-like/kexin type 9), the main regulator of LDLR, were both found significantly upregulated in KLK5 transfectants. A functional role of KLK5 in the regulation of the mevalonate pathway and protein-prenylation circuitries was demonstrated by reduced cellular cholesterol and prenylation levels, end products of this pathway. Reduced prenylation was shown by the remarkable reduction in the levels of activated RhoA, which must be subjected to isoprenylation (mainly geranyl-geranylation) for activation. To our knowledge, this is the first demonstration of a protease involved in the crosstalk between metabolic pathways and oncogenic signaling. Moreover, among the genes found up or down-regulated upon KLK5 re-expression (i.e. the “KLK5 signature”) were several genes known to be involved in atherosclerosis and other lipid-related metabolic disorders. Overall, KLK5 may represent a nodal interconnection of proteolytic and signaling pathways in cancer but may also participate in pathways associated with metabolic diseases, in support of the emerging concept of common genetic networks governing both cancer and lipid-associated disorders.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4125. doi:1538-7445.AM2012-4125

Expression profile of Rho kinases in urinary bladder cancer

PURPOSE

To investigate the expression of RhoA, RhoB, RhoC, Rac1 and Cdc42 kinases in urothelial cell carcinoma (UCC) of the urinary bladder and determine the expression profile of 107 Rho-associated genes, including GTPases, GDIs, GAPs and GEFs.

METHODS

Rho expression was investigated using microarrays, qPCR and Western blotting in 77 UCC specimens with paired normal urothelium. Computational analysis was also performed on Gene Expression Omnibus datasets. Further microarray analysis was carried out for the expression profiling of the Rho-associated genes.

RESULTS

RhoB mRNA and protein levels were significantly lower in UCC, suggesting a tumour-suppressor role. On the contrary, mRNA of RhoC and protein levels of RhoA, RhoC and Cdc42, respectively, were significantly higher in UCC vs. normal tissue. High Cdc42 mRNA levels correlated with worse overall survival (p=0.027), whereas high RhoB mRNA levels correlated both with better overall (p=0.0258) and cancer-specific (p=0.0272) survival. Computational analysis verified the expression profile of Rho kinases among superficial UCCs, muscle-invasive UCCs and normal tissues.

CONCLUSION

The majority of the Rho-related genes showed over-expression in UCC vs. normal tissue. Alterations in RhoA, RhoB, RhoC, Rac1 and Cdc42 expression play a significant role in the genesis and progression of UCC of the urinary bladder.

Association of serum brain-derived neurotrophic factor and duration of untreated psychosis in first-episode patients with schizophrenia

BACKGROUND/AIMS

The brain-derived neurotrophic factor (BDNF) levels in serum and the central nervous system are altered in patients with schizophrenia, suggesting that changes in the expression of BDNF might contribute to the disease pathophysiology. Long duration of untreated psychosis (DUP) has been associated with poorer prognosis in patients with schizophrenia. Such a relationship of untreated psychosis to outcome may indicate a neurodegenerative process and may have important implications for understanding the pathophysiology of schizophrenia.

METHODS

In this study, we investigated the association between serum BDNF levels and DUP in a sample of drug-naïve patients in their first episode of schizophrenia (FEP). We investigated serum BDNF levels in a sample of 37 drug-naïve FEP patients and 21 matched healthy subjects.

RESULTS

The serum BDNF level in the sample of FEP was significantly reduced compared to the healthy subjects (18.87 +/- 8.23 vs. 29.2 +/- 7.73 ng/ml, t = 4.76, d.f. = 57, p = 0.01). A negative correlation was found between serum BDNF levels and DUP in the group of patients (r = -0.346, p = 0.036).

CONCLUSIONS

Our findings indicate that low serum BDNF levels at the onset of schizophrenia were associated with a long DUP and this could reflect an acute neurodegenerative reaction during the untreated phase of psychosis.

Additional characterization of a hexanucleotide polymorphic site in the first intron of human H-ras gene: comparative study of its alterations in non-small cell lung carcinomas and sporadic invasive breast carcinomas

Intron 1 of the human H-ras gene possesses a polymorphism consisting of repetitions of the GGGCCT consensus. Three alleles have been reported at this locus. We confirmed that two, P1 and P2, display four and two repeats, respectively, with their internal sequence structure similar to that previously described. The third, P3, previously assigned as a three-unit repetition allele according to its electrophoretic mobility and with no other information regarding its internal structure, was also found. Sequence analysis of the P3 allele revealed that it consists of three perfect repeats of the GGGCCT consensus. This polymorphism is present only in human c-H-ras gene, although single hexanucleotide repeats are found scattered within intron 1 of this gene in rodents. Analysis of this locus in matched tumor/distant normal samples from: (i) 38 patients with non-small-cell lung carcinoma (NSCLC), and (ii) 35 patients with sporadic invasive breast carcinoma, revealed: (1) 6.6% and 19% loss of heterozygosity (LOH) respectively, and (2) 10.5% and 2.9% hexanucleotide instability (HI) respectively, detected by the presence of shifted in length alleles. Shifted alleles exhibited altered internal sequence structure in comparison to normal ones, suggesting complex mutational events. The same pattern of alterations was also detected in tissues adjacent to lung adenocarcinomas and dysplasias adjacent to squamous cell carcinomas (7.7% LOH, 5.9% HI), implying that abnormalities at this locus may be early events in lung carcinogenesis. The frequency of alterations (LOH vs. HI) was significantly different among NSCLC and breast cancer (P=.005), probably due to the different tumor biology of each system. Finally, altered mRNA expression of H-ras gene was detected in all cases with HI, but this finding was also observed in samples without HI. In view of reports showing that elements in intron 1 of H-ras gene potentially influence its transcriptional regulation, from our results we cannot exclude that the hexanucleotide locus could be an element with possible involvement in expressional regulation of this gene.

Role of matrix metalloproteinase-9 in progression of mouse skin carcinogenesis

Invasion of malignant tumor cells is required for the formation of metastatic colonies. Uncontrolled expression of matrix metalloproteinase (MMP)-2 and MMP-9 is a critical part of the invasive potential of tumor cells and is affected by the balance between the enzymes and the inhibitors secreted by the cell. Here we analyzed the expression and activity of the two gelatinases (MMP-2 and MMP-9) as well as the expression levels of the tissue inhibitor of metalloproteinase (TIMP2)-, in different stages of carcinogenesis using mouse skin cell lines derived from tumors induced by chemical mutagens. Our results suggested that the expression of MMP-9 was implicated in the progression to spindle cell carcinomas in mouse keratinocytes. MMP-2 levels remained steady in all cell lines, whereas levels of TIMP-2 were increased in normal and spindle cells. The AP-1 DNA binding and transcriptional activity on the MMP-9 promoter were increased in the malignant cell lines, indicating the requirement of this binding site for its activation. The results of this study clearly suggested the important role of MMP-9, but not of MMP-2, in the metastatic properties of mouse keratinocytes.

Deregulated expression of c-mos in non-small cell lung carcinomas: relationship with p53 status, genomic instability, and tumor kinetics

Little is known about the status of the mitogen-activating protein kinase pathways in lung cancer. One of the key molecules taking part in these pathways is the product of the c-mos proto-oncogene, which plays an important role in oocyte maturation. In vitro investigations in somatic cells have shown that c-mos expression has opposing effects on the cell cycle, which suggests that this proto-oncogene may represent an important determinant of aberrant cell function (genomic instability and altered kinetics). A recent study suggests that these effects may be p53 dependent. In view of the apparent link between c-mos and p53, we investigated in a series of 56 non-small cell lung carcinomas: a) the status of c-mos; b) its relationship to genomic instability (aneuploidy) and two kinetic parameters of the tumors, proliferation and apoptotic indexes (AI); and c) its association with p53 alterations and their concomitant relationship with the above parameters. We found c-mos overexpression in 27% of the tumors. Expression was higher in stages II/III (34%) than in stage I (17%; P = 0.018). Complete concordance was observed between c-mos overexpression and elevated c-mos mRNA levels. Because c-mos gene amplification was not detected, its deregulated expression may be attributable to increased transcription. Of the c-mos positive [c-mos(P)] cases, 77% were associated with aneuploidy. Sequencing showed two silent mutations and one missense (R-->L) at codon 22, located in a region critical for c-mos stability. In contrast to the findings of some in vitro studies, c-mos(P) tumors had a lower mean AI score than the c-mos negative [c-mos(N)] tumors had, implying that induction of apoptosis may have been defective. Indeed, 86% of the tumors overexpressing c-mos showed p53 alterations. The carcinomas with concomitant alterations of c-mos and p53 [c-mos(P)/p53 positive] had significantly lower AI values (P < 0.001) and were more frequently associated with aneuploidy (P = 0.015) than the c-mos(N)/p53 negative tumors but not the c-mos(N)/p53 positive tumors, which suggests that p53 status is the main determinant of ploidy status and apoptosis in our series. This finding also strengthens the concept that wild-type p53 plays a "safeguard" role in preventing oncogene-mediated activation.

High levels of phosphorylated c-Jun, Fra-1, Fra-2 and ATF-2 proteins correlate with malignant phenotypes in the multistage mouse skin carcinogenesis model

Analysis of the functions of AP-1 transcription factor in cellular systems has shown its key role as a mediator of oncogenic signals. The employment of suitable animal model systems greatly facilitates the study of changes in the composition and activity of the AP-1 complex. Here, we have analysed the quantitative and qualitative changes of AP-1 at different stages of carcinogenesis in mouse skin cell lines, derived from tumours induced by chemical mutagens. The findings of this study suggest that elevated AP-1 DNA binding and transactivation activity characterize the carcinoma cell lines, most notably the highly malignant spindle carcinomas. In addition, increased amounts and post-translational modifications of c-Jun, Fra-1, Fra-2 and ATF-2 proteins account for a high percentage of the increased AP-1 activity. Remarkably, high levels of phosphorylated ATF-2 protein were detected in malignant cell lines, indicating a novel role of ATF-2 in tumour progression. c-Jun and ATF-2 proteins are phosphorylated by highly active JNK kinases present in tumour cells. Finally, our results indicate distinct functions for different AP-1 components in the promotion and progression of mouse skin tumours. Oncogene (2000) 19, 4011 - 4021.

Altered expression of the cell cycle regulatory molecules pRb, p53 and MDM2 exert a synergetic effect on tumor growth and chromosomal instability in non-small cell lung carcinomas (NSCLCs)

BACKGROUND

Recent in vitro studies provide evidence that the cell cycle molecules pRb, p53 and MDM2 form a tightly regulated protein network. In this study, we examined the relationship of this protein network in a series of non-small cell lung carcinomas (NSCLCs), with the kinetic parameters, including proliferative activity or proliferation index (PI) and apoptotic index (AI), and ploidy status of the tumors.

MATERIAL AND METHODS

A total of 87 NSCLCs were examined using immunohistochemical and molecular methods in order to estimate the status of the pRb-p53-MDM2 network. The kinetic parameters and the ploidy status of the tumors were assessed by in situ assays. The possible associations between alterations of the network, kinetic parameters and ploidy status of the carcinomas were assessed with a series of statistical methods.

RESULTS

Aberrant expression of pRb (Ab) and overexpression of p53 (P) and MDM2 (P) proteins were observed in 39%, 57%, and 68% of the carcinomas, respectively. The comprehensive analysis revealed that concurrent alterations in all three cell cycle regulatory molecules were the most frequent pattern, pRb(Ab)/p53(P)/MDM2(P); this "full abnormal" phenotype represented approximately 27% of the cases. This immunoprofile obtained the highest PI/AI value; whereas, the "normal" phenotype was the lowest one (p = 0.004). Furthermore, the pattern pRb(Ab)/p53(P)/MDM2(P) acquired the highest PI (p < 0.001) and lowest AI (p < 0.001) scores. Interestingly, the groups of carcinomas with impaired expression of one or two molecules attained PI/AI ratio values clustered in a narrow range placed in the middle of the scores exhibited by the "normal" and "full abnormal" phenotypes. These tumors had significantly lower AI, but similar PI values, compared with those noticed in the normal pattern. In addition, it was observed that the pRb(Ab)/p53(P)/MDM2(P) phenotype was also significantly associated with aneuploidy (p = 0.002) and a tendency was observed when the expression of two components was altered (p = 0.055).

CONCLUSIONS

Our findings suggest that simultaneous deregulation of all members of the pRb-p53-MDM2 network confers an additive effect on tumor growth. The apoptotic pathway seems to be more susceptible to its defects than the cell proliferation machinery. The findings of the ploidy analysis, which are in parallel with those regarding the proliferative activity and the apoptotic rate study, further support the concept that these molecules constitute a tightly regulated network participating in cell cycle control and chromosomal stability.

Effects of p53 mutants derived from lung carcinomas on the p53-responsive element (p53RE) of the MDM2 gene

The present study represents a continuation of previous works in which we observed that lung carcinomas co-expressing MDM2 protein and p53 mutants (mt p53) exhibited more aggressive behaviour. In the above studies, we suggested a 'gain of function' mechanism of mt p53 proteins based on the fact that the MDM2 gene possesses a p53-responsive element (MDM2-p53RE). In this study, to prove our hypothesis, we selected 12 cases from a series of 51 bronchogenic carcinomas. In these 12 cases, we examined the ability of the expressed mt p53 to bind the MDM2-p53RE and correlated the findings with MDM2 expression. Furthermore, we constructed four of these p53 mutants and studied their transactivation properties by co-transfecting them with a reporter plasmid carrying MDM2-p53RE in the p53 null non-small-cell lung carcinoma cell line (NSCLC) H1299. We observed mutant p53 protein DNA-binding activity, which depended on the nature and the position of the amino acid substitution. The fact that the cases with DNA-binding activity were accompanied with MDM2 protein isoforms' overexpression is indicative of a 'gain of function' phenotype. This hypothesis was enforced by the findings of the transfection experiments, which revealed that certain p53 mutants enhanced the expression of the luciferase reporter gene either directly or indirectly via a dominant positive effect on the wild-type p53. In conclusion, this work is one first attempt to examine if the deregulation of the p53/MDM2 autoregulatory feedback loop is due to novel properties of certain p53 mutants in the specific environment of a subset of bronchogenic carcinomas.

A molecular and immunohistochemical study of the MDM2 protein isoforms and p53 gene product in bronchogenic carcinoma

Forty-one bronchogenic carcinomas were investigated for expression of MDM2 protein isoforms and their relationship to p53 protein levels and p53 gene alterations using molecular and immunohistochemical techniques. The findings were correlated with the pathological features of the carcinomas. MDM2 protein was overexpressed in 26 cases (63 percent). Western blot analysis with two monoclonal antibodies, 1B10 and IF2, revealed three MDM2 protein isoforms, p90, p57 and p76/74. p90 and p57 are capable of interacting with p53 protein, while p76/74 is not. Various patterns of MDM2 isoforms were seen. Although no correlation between the patterns and pathological features was observed, lymph node metastases were more frequent in the cases with MDM2 overexpression (P < 0.005). In 3 out of 17 specimens of normal lung tissue examined, there was a low level of expression of p90. Molecular analysis revealed that MDM2 overexpression was a consequence of increased transcription rather than MDM2 gene amplification. p53 protein was overexpressed in 21 cases (51 percent) and p53 gene alterations (mutations + allelic deletions) were detected in 23 patients (56 percent). A high degree of concordance (76 percent) between p53 mutations and p53 staining was noticed (P < 10(-5)). p53 gene alterations were significantly associated with lymph node disease (P < 0.01). MDM2 and p53 proteins were simultaneously detected in 21 cases (51 percent), of which 17 (42 percent) showed p53 and MDM2 overexpression. The latter group was positively correlated with p53 mutations (P < 0.05). A strong correlation between MDM2/p53 co-expression and lymph node metastases was observed (P < 0.001). The findings suggest that MDM2 overexpression is a common event in bronchogenic carcinoma. The selective expression of some MDM2 isoforms in neoplastic tissue and not in the surrounding normal areas underscores the pathological role of the various MDM2 products. Finally, the coexistence of MDM2 protein(s) and p53 aberrations (mutations and/or overexpression) in a subset of lung carcinomas may be indicative of a 'gain of function' phenotype, with more aggressive characteristics.

Transcriptional Activation of the Human Immunodeficiency Virus Long Terminal Repeat Sequences by Retinoic Acid in Human Epithelial and Fibroblast Tumor Cell Lines

We employed a recombinant plasmid, pBHIV1, carrying the long terminal repeat (LTR) sequences of HIV-1 linked to the reporter chloramphenicol acetyl transferase (CAT) gene and to the aminoglycoside phosphotransferase (aph) gene as a selectable marker. We introduced pBHIV1 into human epithelial and fibroblast tumor cell lines (HeLa and MRCSV40TGR), and obtained stable geneticin-resistant HLHIV1-A and SVTGHIV1-A cells, respectively. The response to the retinoic acid was studied on the LTR regulated CAT activity in both cell lines. It was found that retinoic acid at a concentration of 1×10−5effects a 3.2 - fold increase in CAT expression compared to HIV LTR in HLHIV1-A, but requires a concentration of 5×10−5M to enhance this expression 4.6-fold in SVTGHIV1-A cells. These data show that retinoic acid may play a critical role in HIV-1 expression in human epithelial and fibroblast cell lines.

Binding of wild-type and mutant forms of p53 protein from human tumors to a specific DNA-sequence of the first intron of the h-ras oncogene

p53 is the most frequent target for genetic alterations in a wide variety of human cancers. The product of the p53 tumor suppressor gene binds to DNA and activates transcription from promoters containing its consensus binding site. In the accompanying paper we have found that P53 tumor suppressor protein recognizes specifically a transcriptional element within the human H-ras protooncogene (Spandidos DA, et al, Int J Oncol 7: 1029-1034, 1995). We transfected Saos-2 cells, which are p53-null cells, with plasmids encoding for the wild type (wt) and for one 'hot spot' mutant (mt) of the p53 gene (H 273). Using the resulted nuclear extracts for gel retardation assays, we showed binding of both the wild-type and the mutant form of p53 to the H-ras DNA. Furthermore, using nuclear extracts from head and neck tumors and from adjacent normal tissues in gel retardation assays, we found binding of both the wild-type and the p53 mutant in the same responsive element of the H-ras oncogene. These experimental results suggest a direct role of p53 in regulation of H-ras. Identification of cellular proto-oncogenes as mediators of the transcriptional effects of wild-type and mutant forms of p53 gene, will be a step towards a better understanding of the role of oncogenes and once-suppressor genes in tumor promotion.

Allelotype of squamous cell carcinoma of the head and neck: fractional allele loss correlates with survival

Allelic imbalance or loss of heterozygosity (LOH) studies have been used extensively to identify regions on chromosomes that may contain putative tumour-suppressor genes. We have undertaken an extensive allelotype of 80 specimens of squamous cell carcinoma of the head and neck (SCCHN) using 145 polymorphic microsatellite markers on 39 chromosome arms. Allelic imbalances were found most frequently on chromosome arms 3p, 9p, 17p and 18q with over 45% LOH and imbalances on 1p, 1q, 2p, 5q, 6p, 6q, 8p, 8q, 9q, 11q, 13q, 17q and 19q were found in more than 20% of SCCHN. These LOH data were analysed against a range of clinicopathological parameters which included previously untreated and previously treated tumours; correlations were found between LOH on 9q and nodes at pathology (P = 0.02) and between histopathological grade and LOH on 12q (P = 0.02) and 13q (P = 0.01). In the group of previously untreated tumours, a correlation was found between site of tumour and LOH on 3p (P = 0.019), and 8p (P = 0.029), while TNM staging correlated with LOH on 3p (P = 0.019) and 17p (P = 0.016). Fractional allele loss (FAL) was calculated for 52 tumours with LOH data on nine or more chromosomal arms and found to have a median value of 0.22 (range 0.0-0.80). Correlations were found between FAL > median value and nodes at pathology (P = 0.01) and tumour grade (P = 0.06), demonstrating that advanced tumours with lymph node metastasis often had LOH at multiple sites. FAL > median value was found to correlate with a poor survival (P < 0.03) and, furthermore, FAL > median value correlated with poor survival in the previously untreated patients (P < 0.019). These results indicate that assessment of the accumulation of genetic damage, as provided by allelotype data, provides a useful molecular indicator of the tumour behaviour and clinical outcome.

Molecular analysis of p53 gene in laryngeal premalignant and malignant lesions. p53 protein immunohistochemical expression is positively related to proliferating cell nuclear antigen labelling index

This study was undertaken in order to investigate the molecular nature of the p53 gene in 19 laryngeal squamous cell carcinomas and dysplasias. Moreover, we have examined the possible relationship between proliferating cell nuclear antigen (PCNA) expression and p53 protein detection status in 42 laryngeal premalignant and malignant lesions in which 14 of the 19 samples used in the molecular study were included. p53 gene analysis was performed with the single-strand conformation polymorphism technique. PCNA was stained with the peroxidase/antiperoxidase immunohistochemical method using the monoclonal antibody PC-10. Data from previous work concerning p53 expression was used. We found that 9 of 12 of the immunohistochemically p53 positive (+) cases had mutations in exons 5 or 6. In the remaining immunohistochemically p53(+) and p53 negative (-) specimens there was no indication of sequence alterations. Furthermore, we did not observe any deletions in the chromosomal region 17p31.1 which encodes exons 4-8 of the p53 gene. The PCNA labelling index (LI) increased progressively with p53 protein detection status (percentage of cells immunohistochemically positive for p53). The difference between the group with the higher percentage of p53(+) cells and the others was statistically significant. These data show that although there is a discrepancy between immunohistochemical demonstration of p53 and molecular analysis, a large proportion of the former harbours the mutant form of the protein. In addition, p53 overexpression is positively correlated with PCNA LI, a finding which accompanies tumour progression.

Human lung, bladder and head and neck tumors as compared to their adjacent normal-tissues have elevated ap-1 activity and recognize sequence elements of hiv-1 LTR

We have previously reported the specific binding of nuclear factor AP-1 isolated from human breast MDA MB 468 and HeLa cervical tumor cell lines to oligonucleotides complementary to three newly elucidated sequences within the HIV-1 LTR. These synthesized oligonucleotides, which bear high homology to the AP-1 recognition sequence, were used in the present study in gel retardation assays together with unfractionated nuclear protein extracts from human lung, bladder and head and neck tumors and adjacent normal tissue to study the role of the AP-1 protein in the regulation of HIV-1 expression. We found increased binding of AP-1 to these oligonucleotides in 9/12 lung tumors, 9/14 bladder tumors and 7/7 head and neck tumors as compared to adjacent normal tissues. This confirms previous results obtained when using MDA MB 468 and HeLa nuclear protein extracts. These results indicate that, AP-1 could be contributing to the HIV-1 transcriptional regulation through its interaction with the AP-I binding sites of HIV-I LTR.

Mitomycin C stimulates the expression of human immunodeficiency virus long terminal repeat sequences in rat and human fibroblasts

We have employed a recombinant plasmid, pBHIV1, carrying the long terminal repeat (LTR) sequences of the human immunodeficiency virus-1 (HIV-1) linked to the reporter chloramphenicol acetyl transferase (CAT) gene and to the aminoglycoside phosphotransferase (aph) gene as a selectable marker. We have introduced pBHIV1 into rat 208F and human MRCSV40TGR fibroblasts and obtained stable geneticin resistant RFBHIV1-1 and SVTGHIV1-1 cells, respectively. Both transfectant cells express CAT activity from the HIV LTR promoter. The response to the antineoplastic drug mitomycin C was studied on the LTR regulated CAT activity in both cell lines. It was found that mitomycin C at 10 micrograms/mL concentration stimulates the expression of CAT from the HIV LTR 77-fold in rat RFBHIV1-1 and 3.1-fold in human SVTGHIV1-1 cells.

Differential interaction of cisplatin with the HIV-1 long terminal repeat in a resistant ovarian carcinoma cell line

We constructed a recombinant plasmid, pBHIV1, carrying the long terminal repeat (LTR) sequences of HIV-1 linked to the reporter chloramphenicol acetyl transferase (CAT) gene and to the aminoglycoside phosphotransferase (aph) gene as a selectable marker. We have introduced pBHIV1 in a human ovarian cancer cell line A2780 and in a cisplatin resistant variant 2780CP, and obtained stable geneticin resistant A27HIV1-1 and 27CPHIV1-1 cells, respectively. Both transfectant cells expressed CAT activity from the HIV LTR promoter. The response to the anti-neoplastic drug cisplatin was studied on the LTR regulated CAT activity in both cell lines. It was found that cisplatin at 2.5 x 10(-5) M concentration stimulates the expression of CAT by 26-fold from the HIV LTR in A27HIV1-1, but requires a concentration of 5 x 10(-5) M to enhance expression by 4.1-fold in the cisplatin resistant 27CPHIV1-1 cells. Carboplatin, over a range of concentrations (1 x 10(-6) to 1 x 10(-4) M), does not stimulate expression of CAT from the HIV-1 LTR in either of the transfected cells.

Transcriptional activation of the human immunodeficiency virus long terminal repeat sequences by tumor necrosis factor

The recombinant plasmid pBHIV-1 carrying the long terminal repeat (LTR) of the human immunodeficiency virus 1 (HIV-1), linked to the reported chloramphenicol acetyl transferase (CAT) gene, was introduced into human and rat fibroblasts. Stable transfectants were obtained which were resistant to genetecin and expressed CAT-activity from the HIV-1 LTR. The response to TNF alpha was studied. It was found that, at the optimum concentration of 100 IU/ml in human and 1000 IU/ml in rat fibroblasts, the expression of CAT was stimulated by 2.1 and 2.5-fold respectively. Our findings suggest that TNF-alpha in physiological concentrations can transcriptionally activate the HIV-1 LTR sequences and this may play an important role in the pathogenesis of HIV infection.

Hexamethylene bisacetamide stimulates the expression of human immunodeficiency virus long terminal repeat sequences in rat and human fibroblasts

We have employed a recombinant plasmid, pBHIV1, carrying the long terminal repeat (LTR) sequence of the human immunodeficiency virus-1 (HIV-1) linked to the reporter chloramphenicol acetyl transferase (CAT) gene and to the aminoglycoside phosphotransferase (aph) gene as a selectable marker. We have introduced pBHIV1 in rat 208F and human MRCSV40TGR fibroblasts and obtained stable geneticin resistant RFBHIV1-1 and SVTGHIV1-1 cells, respectively. Both transfectant cells express CAT activity from the HIV LTR promoter. The response to anti-neoplastic drug hexamethylene bisacetamide (HMBA) was studied on the LTR regulated CAT activity in both cell lines. It was found that HMBA at 5mM concentration stimulates the expression of CAT from the HIV LTR in rat and human cells by 28- and 1.9-fold, respectively.

Carboplatin as opposed to cisplatin does not stimulate the expression of the human immunodeficiency virus long terminal repeat sequences

The recombinant plasmid pBHIV1 carrying the long terminal repeat (LTR) of the human immunodeficiency virus 1 (HIV-1), linked to the chloramphenicol acetyl transferase (CAT) gene, was introduced into human and rat fibroblasts. Stable transfectants resistant to geneticin expressed CAT activity from the HIV-1 LTR. It was found that the cytotoxic drug cis-diammine(1,1-cyclobutanedicarboxylato)platinum(II) (carboplatin) at concentrations from 1 x 10(-6) to 1 x 10(-4) M does not stimulate the expression of CAT from the HIV-1 LTR. These results differ from previous studies with the related drug cis-diamminedichloroplatinum(II) which showed stimulation of gene expression from the HIV-1 LTR and suggest that carboplatin could be used in the treatment of cancer patients with Acquired Immune Deficiency Syndrome.

Cis-platin responsive sequences in the human c-myc promoter

We have transfected recombinant plasmids carrying 5' c-myc sequences linked to the reporter gene chloramphenicol acetyl-transferase (cat) and to the selectable marker aminoglycoside phosphotransferase (aph) into rat fibroblasts and obtained stable transfectants. The response to cis-platin of these cell lines was studied. At 5 X 10(-5) M concentration cis-platin stimulates cat gene expression 9 and 11 fold respectively in cell lines containing constructs with c-myc promoter sequences truncated at -2319 and -350 relative to c-myc RNA start site P1. A third cell line expressing a myc/cat recombinant truncated at -290 shows no response to cis-platin, thus defining a cis-platin responsive element between coordinates -290 and -350 on the myc promoter region.

Doxorubicin stimulates transcription from the human immunodeficiency virus long terminal repeat sequences

A recombinant plasmid carrying the long terminal repeat (LTR) of the human immunodeficiency virus 1 (HIV-1) linked to the reporter chloramphenicol acetyl transferase (CAT) gene was stably introduced into rat liver cells. The transfectant cells expressed CAT activity from the HIV LTR. The response to doxorubicin was studied and it was found that at the optimum concentration of 20 micrograms/ml doxorubicin, the expression of CAT from the HIV LTR was stimulated by 65-fold. Our results suggest caution against therapy including doxorubicin in the treatment of AIDS patients.

Cisplatin stimulates the expression from the human immunodeficiency virus long terminal repeat sequences in human fibroblasts

A recombinant plasmid carrying the long terminal repeat (LTR) of the human immunodeficiency virus 1 (HIV-1) linked to the reporter chloramphenicol acetyl transferase (CAT) gene was stably introduced into human fibroblasts. The transfectant cells expressed CAT activity from the HIV LTR. The response to anti-neoplastic drugs, i.e. cisplatin, a platin derivative, and hexadecylphosphocholine, was studied. It was found that at 5 x 10(-6) M concentrations cisplatin stimulates by 2.2-fold the expression of CAT from the HIV LTR. Our results extend our observations on the effect of cisplatin on HIV LTR in rodent fibroblast cells and suggest caution against therapy including cisplatin in the treatment of AIDS patients.

Transcriptional activation of the human immunodeficiency virus long terminal repeat sequences by cis-platin

We constructed a recombinant plasmid, pBHIV1 carrying the long terminal repeat (LTR) of the human immunodeficiency virus 1 (HIV-1), linked to the chloramphenicol acetyl transferase (CAT) gene plasmid. Plasmid pBHIV1 also contains the aminoglycoside phosphotransferase gene as a selectable marker. We introduced pBHIV1 in rat 208F fibroblasts and obtained stable geneticin resistant RFBHIV1-1 transfectant cells. A further control used was plasmid p202A, which carries the mutant T24 H-ras1 promoter linked to the promotorless cat gene. Plasmid p202A also carries the aph gene as a selectable marker and was transfected into 208F cells to obtain stable transfectant RF202A-1 cells. Both RFBHIV1-1 and RF202A-1 cells expressed CAT activity from the HIV LTR and T24 H-ras1 promoters. The response to cis-platin, a platin derivative and hexadecyl-phosphocholine was studied on the HIV LTR and H-ras1 regulated CAT activity in RFBHIV1-1 and RF202A-1 cells. It was found that at 5 x 10(-5) M concentrations cis-platin stimulates by 22-fold the expression of CAT from the HIV LTR, whereas only a 4-fold stimulation was observed on the T24 H-ras1 promoter. Our results suggest caution against therapy including this compound at cytotoxic concentrations in the treatment of AIDS patients.

Response of human immunodeficiency virus long terminal repeat to growth factors and hormones

We have employed a recombinant plasmid, pBHIV1, carrying the long terminal repeat (LTR) of the human immunodeficiency virus-1 (HIV-1) linked to the reporter chloramphenicol acetyl transferase (cat) gene and to the aminoglycoside phosphotransferase (aph) gene as a selectable marker. We have introduced pBHIV1 in rat 208F and human MRCSV40TGR fibroblasts and obtained stable geneticin resistant RFBHIV1-1 and SVTGHIV-1 transfectant cells respectively. Both RFBHIV1-1 and SVTGHIV1-1 cells express CAT activity from the HIV LTR promoter. The response to insulin, epidermal growth factor, hydrocortisone and dexamethasone was studied on the LTR regulated CAT activity in both cell lines. It was found that, at optimal concentrations, insulin, epidermal growth factor and hydrocortisone regulate positively the expression of CAT from the HIV LTR in rat RFBHIV1-1 but not in human SVTGHIV1-1 cells. On the other hand dexamethasone at 10(-5) M stimulated CAT activity in both types of cells.