Co-prevalence of human Papillomaviruses (HPV) and Epstein-Barr virus (EBV) in healthy blood donors from diverse nationalities in Qatar.

BACKGROUND: Infections by both human oncoviruses, human Papillomaviruses (HPV) and Epstein-Barr virus (EBV) are very common in the adult human population and are associated with various malignancies. While HPV is generally transmitted sexually or via skin-to-skin contact, EBV is frequently transmitted by oral secretions, blood transfusions and organ transplants. This study aims to determine the prevalence and circulating genotypes of HPV and EBV in healthy blood donors in Qatar. METHODS: We explored the co-prevalence of high-risk HPVs and EBV in 378 males and only 7 females blood donors of different nationalities (mainly from Qatar, Egypt, Syria, Jordan, Pakistan, and India) residing in Qatar, using polymerase chain reaction (PCR). DNA was extracted from the buffy coat and genotyping was performed using PCR and nested-PCR targeting E6 and E7 as well as LMP-1 of HPV and EBV, respectively. RESULTS: We found that from the total number of 385 cases of healthy blood donors studied, 54.8% and 61% of the samples are HPVs and EBV positive, respectively. Additionally, our data revealed that the co-presence of both high-risk HPVs and EBV is 40.4% of the total samples. More significantly, this study pointed out for the first time that the most frequent high-risk HPV types in Qatar are 59 (54.8%), 31 (53.7%), 52 (49.1%), 51 (48.6%), 58 (47%) and 35 (45.5%), while the most commonly expressed low-risk HPV types are 53 (50.6%), 11 (45.5), 73 (41.7%) and 6 (41.3%), with all the cases showing multiple HPVs infection. CONCLUSION: In this study, we demonstrated for the first time that HPV and EBV are commonly co-present in healthy blood donors in Qatar. On the other hand, it is important to highlight that these oncoviruses can also be co-present in several types of human cancers where they can cooperate in the initiation and/or progression of these cancers. Therefore, more studies regarding the co-presence of these oncoviruses and their interaction are necessary to understand their cooperative role in human diseases.

Apolipoprotein E, CI and B gene polymorphisms in a sample of patients with coronary heart disease in the Kuwaiti population.

OBJECTIVES: The objective of this study was to investigate the possible association of clinical variables and apolipoprotein (APOE, APOCI and APOB) polymorphisms with the development of myocardial infraction (MI) and coronary heart disease (CHD) in Kuwaitis. SUBJECTS AND METHODS: APOE, APOCI and APOB genotypes were determined by polymerase chain reaction followed by restriction fragment length polymorphism in 143 Kuwaiti CHD patients with (n = 88) and without (n = 55) MI and in 122 controls matched for gender and age. Statistical and genetic analyses of the genotype, allele and haplotype frequencies, as well as regression analyses of genetic and clinical variables were done. RESULTS: There was a statistically significant association between CHD and medical history of diabetes mellitus (p < 0.001), hypertension (p < 0.01), high cholesterol (p < 0.05) and family history of CHD (p < 0.001). A highly significant association (p < 0.001) was found, with an adjusted odds ratio of 9.32, for family history and the development of MI. No significant differences were found for allele or genotype frequencies between CHD patients and controls. CONCLUSION: The strong effect of family history suggests a major genetic component for the development of CHD in Kuwaitis, but this association does not appear to be related to the APO genes studied here. The results in this study encourages future research into these and other polymorphisms and their potential association with MI and CHD in the Kuwaiti population.

Epstein-Barr virus (EBV) status in colorectal cancer: a mini review.

Epstein-Barr virus (EBV) is a well-characterized oncovirus, associated with several malignancies. The complex and heterogeneous nature of colorectal cancer (CRC) has led to many epidemiological causal associations with CRC. However, a direct causal link between microbial infections and CRC has not been established yet. Our review indicates that the current evidence for the presence and role in EBV in CRC is insufficient and contradictory. The design of the analyzed studies, sample size as well as methodology used for EBV detection varied markedly and consequently may not lead to meaningful conclusions. The presence of EBV in other colorectal tumors (lymphomas, smooth muscle tumors) is in line with their status at other anatomic locations and may have therapeutic implications with EBV-specific vaccines. On the other hand, studies exploring EBV in colorectal adenoma-carcinoma sequence and its molecular genetic characteristics are largely missing and may significantly contribute to a better understanding of the role of EBV in CRC.

Resveratrol reverses hydrogen peroxide-induced proliferative effects in human coronary smooth muscle cells: a novel signaling mechanism.

BACKGROUND: In human coronary smooth muscle cells (HCSMCs), we tested the proatherogenic/proliferative potential of the reactive oxygen species (ROS), hydrogen peroxide (HP), and the ability of the polyphenol stilbene resveratrol (RSVL) to protect against such effects. METHODS: Activity for ERK1/2 and the kinase-G cascade were determined and correlated with HCSMC count before and after treatment with HP and/or RSVL. RESULTS: HP evoked concentration-dependent cell proliferation and stimulated ERK1/2 phosphorylation at active sites. Pretreatment with the MEK-ERK inhibitor (PD98059) reversed these effects of HP. RSVL (1-100 microM) elicited more prominent inhibition of HP-evoked cell proliferation and ERK1/2 activation. In addition, RSVL markedly enhanced cGMP formation, a response that was insensitive to the soluble guanylyl-cyclase (sGC) inhibitor (ODQ, 10 microM) but was obliterated with the phorbol ester, (PMA, 0.1 microM), a desensitizer of the pGC enzyme. Likewise, the RSVL-evoked cytostatic and ERK inhibitory effects were significantly reversed by the kinase-G-inhibitor, KT-5823 (10 microM). CONCLUSIONS: Collectively, RSVL activates the kinase-G system to counteract HP-induced ERK1/2 activation and coronary arterial proliferation. These effects for RSVL remain functional in endothelium-disrupted arteries, scenarios that commonly occur in advanced coronary heart disease.

Resveratrol-induced apoptosis in human breast cancer cells is mediated primarily through the caspase-3-dependent pathway.

BACKGROUND: Resveratrol (RSVL), a nontoxic natural compound found in a wide variety of plants with known antioxidant and anti-inflammatory properties, is emerging as a potent chemopreventive and anticancer drug. Recently, we demonstrated that RSVL-induced apoptosis in several human cancer cell lines was associated with cleavage of the proapoptotic 116 kDa poly(ADP-ribose) polymerase protein (PARP) into its 89-kDa fragment. METHODS: Western blotting was used to check the levels of caspase-3 and PARP proteins. The caspase activity was analyzed with the caspase-3 colorimetric substrate DEVD-pNA. Apoptotic cells were quantified by annexin V-FITC-propidium iodide double staining. RESULTS: We show that RSVL cleaved the immature caspase-3 (35 kDa) into the active fragments (p12, p17, p20) in a dose- and time-dependent manner. In addition, RSVL markedly increased caspase-3 activity (5-fold) in cells. Interestingly, RSVL-induced PARP cleavage and apoptosis was blocked specifically by inhibiting caspase-3. CONCLUSIONS: Collectively, the data suggest that caspase-3 activation by RSVL is required for PARP degradation and induction of apoptosis in MDA-MB-231 cells and provide additional insights into the action of RSVL, thus substantiating the chemopreventive potential of RSVL against human breast cancer.

Consumption of green tea alters glial fibriliary acidic protein immunoreactivity in the spinal cord astrocytes of STZ-diabetic rats.

We examined the effect of green tea consumption on glial fibriliary acidic protein (GFAP) expression in spinal cord of streptozotocin (STZ) treated rats. Three groups (n = 10) were used in this study: (i) controls; (ii) STZ-induced diabetic rats given tap water; and (iii) an STZ-induced diabetic group given green tea. Immunohistochemistry showed a significant (P < 0.001) decrease in the number of GFAP immunoreactive astrocytes in spinal cord sections of diabetic rats compared to non-diabetic controls. Diabetic rats treated with green tea showed a significant (P < 0.01) increase in the number GFAP-immunoreactive astrocytes in all the spinal cord gray areas as compared to water-drinking diabetic rats. Immunoblotting confirmed that the diabetic spinal cord tissue expressed 71.0 +/- 7.0% less GFAP compared to non-diabetic controls and that the GFAP content in diabetic rats increased up to 86.34 +/- 18.74% compared to non-diabetic controls after 12 weeks of green tea consumption. In conclusion, consumption of green tea may represent an achievable adjunct therapy for improving changes seen in diabetic spinal cord.

Resveratrol-induced growth inhibition in MDA-MB-231 breast cancer cells is associated with mitogen-activated protein kinase signaling and protein translation.

Resveratrol (3,4',5-trans-trihydroxystilbene) is a natural compound found in grapes and several medicinal plants and has been shown to have anticancer effects on various human cancer cells. The aim of this study was to further investigate the molecular mechanism of this anticancer effect. Resveratrol effect on cell growth, morphology and gene expression was investigated in estrogen receptor-negative MDA-MB-231 human breast cancer cell line. We show here that resveratrol-induced growth inhibition in the estrogen receptor negative MDA-MB-231 breast cancer cells is due to the induction of apoptosis as demonstrated by morphological, nuclear staining and PARP cleavage analysis. Resveratrol-induced growth inhibition was associated with transient activation of p44/42 mitogen-activated protein kinase (MAPK) (Thr202/Tyr204). Most importantly, resveratrol inhibited both the phosphorylation at Ser240/244 and the expression of the pS6 ribosomal protein. This protein is known to play an important role in the translation of mRNAs that have oligopyrimidine tracts in their 5' untranslated regions. Interestingly, only MAPK inhibitor was able to block resveratrol-induced growth inhibition suggesting that effects of resveratrol on cell growth are dependent on MAPK signaling. The data demonstrated that resveratrol-induced apoptosis is associated with MAPK signaling and with the inhibition of proteins that are involved in protein translation. This is the first data linking resveratrol with downregulation of protein translation via p44/42 MAPK and S6 ribosomal protein. We propose to use these proteins as predictive biomarkers to evaluate the treatment efficacy of resveratrol in estrogen receptor-negative human breast cancer.

Detection of a novel chromosomal translocation and chromosomal instability in women with recurrent abortions.

OBJECTIVE: To identify a novel chromosomal translocation associated with recurrent abortion and measure DNA chromosomal instability in cells from these patients. STUDY DESIGN: Chromosomal karyotyping analysis was performed on cultures of peripheral blood lymphocytes by using the GTG-banding method. The chromosomal instability of patients and matched controls was tested by measuring the hypersensitivity to the clastogenic effect of the DNA cross-linking agent 1-3-butadiene diepoxide. RESULTS: A novel chromosomal translocation, t(2;10) (p21;pl5), was found in 2 young women who had a reproductive history of early recurrent spontaneous abortions (7-10 weeks). In addition to the abnormal karyotypes, cultured patient lymphocytes showed increased chromosomal fragility/instability as compared with normal controls. This chromosomal instability was further enhanced by the DNA clastogenic agent diepoxybutane. CONCLUSION: Although the relationship between this chromosomal translocation and the DNA fragility in these patients is not well understood, this study showed for the first time a link between the presence of this novel chromosomal translocation and complete early embryonic lethality. Additional studies should be undertaken to identify the gene or genes affected by this translocation and may shed some light on the relationship between this chromosomal translocation and chromosomal instability.

Potent antiproliferative effects of resveratrol on human osteosarcoma SJSA1 cells: Novel cellular mechanisms involving the ERKs/p53 cascade.

The chemopreventive activity of resveratrol (RSVL) has been demonstrated in several types of cancer. However, its effects and the underling mechanisms remain poorly understood. In this study, we investigated the involvement of the mitogen activated protein kinase (MAPK)/p53 signal transduction mechanism in RSVL-induced growth inhibition using a human osteosarcoma cell line. We demonstrate that RSVL reduces cell viability and growth of SJSA1 osteosarcoma cells. Morphological profiles and 4,6-diamidino-2-phenylindole nuclear staining of RSVL-treated cells indicated marked nuclear fragmentation. Cleavage of the (116-kDa) poly(ADP-ribose) polymerase protein into an 89-kDa fragment (a proapoptotic marker system) was substantially augmented by RSVL treatment. RSVL-dependent growth impairment was preceded by enhanced phosphorylation of extracellular signal-regulated kinase (ERK)1/2 (at Thr202/Tyr204). Likewise, RSVL increased the phosphorylation of p53 tumor suppressor protein (at Ser15). The effects of RSVL on ERKs and on p53 phosphorylation were abrogated by either the MAPK inhibitor PD98059 or the p53 inhibitor pifithrine-alpha. The present study indicates that RSVL antiproliferative effects on osteosarcoma cells are mediated by the activation of the ERKs/p53 signaling pathway and therefore identifies new targets for strategies to treat and/or prevent osteosarcoma.

Glycolaldehyde induces growth inhibition and oxidative stress in human breast cancer cells.

Glycolaldehyde (GA) is formed by oxidative degradation of glucose, from glycated proteins, lipid peroxidation, and oxidation of amino acids, and by human neutrophils during phagocytosis. The exact purpose of GA production by phagocytes is unclear, but it is tempting to speculate that it is part of the defense against invading bacteria and tumor cells. We have already reported that GA induces apoptosis in breast cancer cells. Because the GA carbonyl group cannot be blocked by cyclization, it is prone to enolization followed by air oxidation with concomitant production of glyoxal and superoxide. Since both these products can induce oxidative stress, in this work we focused on the ability of GA to cause oxidative cell damage. MCF7 human breast cancer cells were incubated with different GA concentrations and O2*- production, lipid peroxidation, and carbonylated protein were assessed. GA was cytotoxic at 20 microM, inhibiting cell proliferation, and at 100 microM, induced p53 expression and caused apoptosis. These events were accompanied by increases of O2*- production, lipid peroxidation, and accumulation of protein carbonyl. It thus appears that alpha-hydroxy aldehydes can induce oxidative stress. Prevention of oxidative stress, however, did not abolish the effects of GA on cell growth and viability, which appeared to be a direct consequence of glyoxal toxicity.

Cytotoxic activity of methanolic extract of Mentha longifolia and Ocimum basilicum against human breast cancer.

Labiatae family is represented in Saudi Arabia. The aim of the present study was to go insight to investigate the anticancer activity and antioxidative potentials of methanolic extracts of Mentha longifolia L. (ML) and Ocimum basilicum L. (OB) that grown in Madina province, western region, Saudi Arabia. OB exhibited the greater phenolic contents as mg gallic acid equivalent/g weight (mg GAE/g) for a value of 105 +/- 5.5 mg GAE/g. On the other hand, ML produced 29 +/- 3.12 mg GAE/g. The standard antioxidant vitamin E used in this experiment elicited a value of total phenolic contents equal 22 +/- 2.2 mg GAE/g. The percentage scavenging activity of against diphenylpicrylhydrazyl (DPPH) was 850 and 160% for OB and ML extracts, respectively. Vitamin E elicited% scavenging activity of against DPPH equal to 198%. Brine shrimp cytotoxic assay clearly indicated the cytotoxic effects of either ML or OB extract. The brine shrimp survival is inversely proportional to the concentration of either ML or OB extract used with LD50 191.23 and 235.50 ppm, respectively. Toxic effects on brine shrimps indicated the anticancer potential of ML or OB extract. The ML or OB extract was unable to produce pbluescript (pBS) plasmid DNA damage, while the plasmid DNA treated with EcoRI produced a single band as a result of DNA damage. Also, both ML and OB extract exhibited marked cytotoxic activity against MCF-7 cells at various concentrations (20, 40, 80, 160 and 320 microg mL(-1)). The 160 and 320 microg mL(-1) showed more cytotoxic effect against MCF-7 cells. Based on results achieved, we can concluded that, OB and ML extracts have the potency to act as powerful antioxidants and protect against DNA damage and have cytotoxic activity against MCF-7 cell line.

Role of Na+/H+ exchanger in resveratrol-induced growth inhibition of human breast cancer cells.

Cancer cells maintain low intracellular pH [pHi]; therefore, it is likely that resveratrol [RSVL] inhibits cell growth through interference with regulation of pHi. Na-H exchanger [NHE] regulates pHi and NaCl uptake. In this study, we investigated a putative role of NHE-1 and NHE-3 isoforms in the RSVL-induced cell death using MDA-MB-231 estrogen receptor-negative [ER-] and MCF-7 [ER+] human breast cancer cell lines. ECL Western blot analysis and fluorescence morphometeric analysis were used. Cell viability and counting were performed using standard procedures. RSVL caused a dose- and time-dependent induction of NHE-1 and NHE-3 proteins in both cancer cell lines as shown by ECL Western blot analysis and fluorescence measurement. Interestingly, the level of actin, an internal control, remains unaltered. Thus, it is concluded that RSVL-inhibited cell growth and viability, increased cell size, and volume along with an increased apoptotic activity are due to the induction of NHE-1 and NHE-3 isoforms in the present breast cancer cell lines. Induction of NHE will increase the uptake of NaCl and decrease pHi leading to disturbance in Ca(2+) homeostasis, which is responsible for cell death.

P53 gene polymorphisms and breast cancer risk in Arab women.

The association between polymorphisms in the p53 tumor suppressor gene and breast cancer risk has been studied in many human populations with conflicting conclusions. However, similar studies in Arab women are not available, and the status of these polymorphisms in this ethnic population is not known. We investigated the status of four known p53 gene polymorphisms and their possible role in breast cancer risk in Arab women. Genotyping was performed for 288 breast cancer women and 188 controls to determine Pro47Ser, Arg72Pro, Intron 3 Ins16 bp and intron 6 (G > C) polymorphisms. The p53 variant Pro47Ser was detected only in one Kuwaiti breast cancer patient and was not detected in any of the control subjects. Frequency of Arg/Arg at codon 72 was 26.6% in controls and 28.1% in patients, Arg/Pro frequency was 59.6% in controls and 69.4% in patients, the Pro/Pro genotype was 13.8% in controls and 2.4% in patients. We observed that women with Pro/Pro genotype have decreased risk for developing breast cancer (OR=0.166, 95% CI=0.067-0.411, p<0.001). The intron 3 genotypes were A1/A1 (48.9%), A1/A2 (40.6%) and A2/A2 (10.5%) in controls and A1/A1(42.4%), A1/A2 (52.8%) and A2/A2 (4.8%) in cases. The intron 6 genotypes were 92.4% (GG), 7.6% (GC) and 0% (CC) in controls and 96.5% (GG), 3.5% (GC) and 0% (CC) in cases. No statistically significant differences between patients and controls were observed for intron 3 and intron 6 polymorphisms. Our data show that proline homozygosity at p53 codon 72 is associated with decreased breast cancer risk in Arab women.

A comparative study of excitatory and inhibitory amino acids in three different brainstem nuclei.

This study was designed to shed more light onto the three different brainstem regions which are implicated in the pain pathway for the level of various excitatory and inhibitory neurotransmitters before and following neuronal stimulation. The in vivo microdialysis technique was used in awake, freely moving adult Sprague-Dawley rats. The neurotransmitters studied included aspartate, glutamate, GABA, glycine, and taurine. The three brainstem regions examined included the mid-brain periaqueductal gray (PAG), the medullary nucleus raphe magnus (NRM), and the spinal trigeminal nucleus (STN). Neuronal stimulation was achieved following the administration of the sodium channel activator veratridine. The highest baseline levels of glutamate (P < 0.0001), aspartate (P < 0.0001), GABA (P < 0.01), taurine (P < 0.0001), and glycine (P < 0.001) were seen in the NRM. On the other hand, the lowest baseline levels of glutamate, GABA, glycine, and taurine were found in the PAG, while that of aspartate was found in the STN. Following the administration of veratridine, the highest release of the above neurotransmitters except for the aspartate and glycine was found in the PAG where the level of glutamate increased by 1,310 +/- 293% (P < 0.001), taurine by 1,008 +/- 143% (P < 0.01), and GABA by 10,358 +/- 1,920% (P < 0.0001) when comparison was performed among the three brainstem regions and in relation to the baseline levels. The highest release of aspartate was seen in the STN (2,357 +/- 1,060%, P < 0.001), while no significant difference was associated with glycine. On the other hand, the lowest release of GABA and taurine was found in the STN (696 +/- 91 and 305 +/- 25%, respectively), and glutamate and aspartate in the NRM (558 +/- 200 and 874 +/- 315%, respectively). Our results indicate, and for the first time, that although some differences are seen in the baseline levels of the above neurotransmitters in the three regions studied, there are quite striking variations in the level of release of these neurotransmitters following neuronal stimulation in these regions. In our opinion this is the first study to describe the pain activation/modulation related changes of the excitatory and inhibitory amino acids profile of the three different brainstem areas.

Resveratrol-induced apoptosis is associated with activation of p53 and inhibition of protein translation in T47D human breast cancer cells.

BACKGROUND AND PURPOSE: Trans-resveratrol (RSVL; 3,4',5-trihydroxystilbene), a natural compound found in grapes, berries, peanuts and red wine exerts certain anticancer roles in different human cancer types. However, the exact molecular mechanism(s) behind such a role remains to be elucidated, thus the aim of this study. EXPERIMENTAL APPROACH: T47D human breast cancer cells were treated with RSVL and cell proliferation was measured by cell counting. Apoptosis was analyzed by Giemsa staining, poly(ADP-ribose) polymerase (PARP) fragmentation analysis and annexin V assay. Regulation of p53 tumor suppressor protein, p70S6K, and pS6 ribosomal protein was measured by detecting their phosphorylated active forms using ECL-immunoblot analysis. RESULTS: The present results show that RSVL-induced growth inhibition in T47D cells is caused by apoptosis as demonstrated by morphological changes and PARP fragmentation. RSVL-induced apoptosis is associated with the activation of the p53 in a dose- and a time-dependent manner. Phosphatidylinositol 3-kinase (PI3K) inhibitors, wortmannin and LY294002 abolished the effect of RSVL on p53 activation. Interestingly, RSVL inhibits the expression of p70S6K and the phosphorylation of pS6RP. CONCLUSIONS AND IMPLICATIONS: These findings demonstrate that RSVL affects multiple intracellular signaling transduction pathways such as p53 activation/protein translation inhibition/apoptosis, and strongly support a contemplated use of this natural compound as a preventive and/or an adjuvant therapeutic drug for breast cancer. The data indicate that these proteins may be used as predictive biomarkers to evaluate the treatment efficacy of RSVL in clinical trials.

Polymorphism of p53 gene codon 72 in Kuwaiti with coronary artery disease and diabetes.

BACKGROUND AND AIM: Polymorphism in the p53 gene at codon 72 has been linked to the development of certain diseases including cancer. A possible association between such polymorphism and the development of coronary artery disease (CAD) and diabetes is being investigated, but no conclusive evidence has been reached yet. Our study is the first pilot study to be conducted on Kuwaitis suffering from CAD and diabetes, aiming at investigating the possible existence of the above association. MATERIALS AND METHODS: We analyzed the genotype distribution and allele frequency of p53 gene at codon 72 in 158 CAD samples and 110 controls, and in 142 diabetic and 130 controls. RESULTS: Analysis of CAD patients revealed an alarming significant association between the disease and the existence of diabetes (P=0.0007). Also, the CAD patients had significantly higher level of triglyceride (P<0.0001) and cholesterol (P<0.0001) as compared to control. As for the polymorphism in p53 gene codon 72, we could not detect any association with the genotype Pro/Pro, Pro/Arg or Arg/Arg distribution (P=0.28) or allele (Pro or Arg) frequency (P=0.25) in the CAD patients. Similarly, no association was found with the genotype Pro/Pro, Pro/Arg or Arg/Arg distribution (P=0.44) or allele (Pro or Arg) frequency (P=0.26) in the diabetic patients. CONCLUSION: CAD seems to be strongly linked to diabetes in Kuwait. Polymorphism in the p53 gene at codon 72 revealed no significant association with the development of CAD or diabetes in Kuwait, which confirms other similar results obtained in the US and Asia.

Resveratrol Regulation of PI3K-AKT Signaling Pathway Genes in MDA-MB-231 Breast Cancer Cells.

BACKGROUND: Resveratrol (RSVL), a natural compound found in grapes and other food products, has been described to exert cancer chemopreventive activities. However, the cellular and molecular basis of its anticancer activity is largely undefined. The aim of the present study was to identify RSVL target genes in the MDA-MB-231 breast cancer cell line using cDNA arrays representing genes of the PI3K/AKT signaling pathway. MATERIALS AND METHODS: Total RNA from control and RSVL-treated cells was used to synthesize biotinylated cDNA probes. cDNA arrays were hybridized with the probes and signals were detected with a chemiluminescent method. Western blotting analysis was used to validate the arrays' gene expression. RESULTS: At the cDNA level, 13 genes were altered (at least 2-fold difference) by RSVL treatment. At the protein level, both c-fos and P70S6K were also regulated. CONCLUSION: Using gene arrays it was shown for the first time that c-fos and p70S6 kinase were regulated by RSVL.

Progesterone inhibition of MDM2 p90 protein in MCF-7 human breast cancer cell line is dependent on p53 levels.

The mdm2 gene encodes several protein isoforms with different molecular weights (p90, p80, p76 and p57). MDM2 p90 (usually considered to be the major MDM2 protein) binds to and inactivates P53. We have recently shown that growth inhibition of MCF-7 human breast cancer cells by progesterone is associated with P53 down-regulation. In this work, we analyzed the expression pattern of MDM2 proteins in three human breast cancer cell lines by western blotting with anti-MDM2 antibodies. We found a prominent expression of MDM2 p57 protein in cell lines which have non-functional P53 protein (T47D and MDA-MB-231) as compared to the p90, p80 isoforms, whereas p90 was the major protein isoform in MCF-7 cells that contain functional P53 protein. When MCF-7 cells were treated with 100 nM of progesterone, MDM2 p90 was inhibited but the highly expressed MDM2 p57 isoform was not. The inhibition of MDM2 p90 protein by progesterone was abrogated in MCF-7 cells transfected with a P53 expressing vector. To our knowledge, this is the first report linking progesterone-induced growth inhibition with down-regulation of the MDM2 protein. We present evidence that reestablishing of P53 expression by transient transfection of P53 cDNA in these cells enhances the expression level of MDM2 p90 isoform. The data indicate that expression of MDM2 p90 is regulated through a P53-dependent pathway in response to progesterone.