Overexpression Of Proliferating Cell Nuclear Antigen Research Articles

Squalene monooxygenase facilitates bladder cancer development in part by regulating PCNA

Bladder cancer (BC) is one of the most common cancers worldwide. Although the treatment and survival rate of BC are being improved, the risk factors and the underlying mechanisms causing BC are incompletely understood. Squalene monooxygenase (SQLE) has been associated with the occurrence and development of multiple cancers but whether it contributes to BC development is unclear. In this study, we performed bioinformatics analysis on paired BC and adjacent non-cancerous tissues and found that SQLE expression is significantly upregulated in BC samples. Knockdown of SQLE impairs viability, induces apoptosis, and inhibits the migration and invasion of BC cells. RNA-seq data reveals that SQLE deficiency leads to dysregulated expression of genes regulating proliferation, migration, and apoptosis. Mass spectrometry-directed interactome screening identifies proliferating cell nuclear antigen (PCNA) as an SQLE-interacting protein and overexpression of PCNA partially rescues the impaired viability, migration, and invasion of BC cells caused by SQLE knockdown. In addition, we performed xenograft assays and confirmed that SQLE deficiency inhibits BC growth in vivo. In conclusion, these data suggest that SQLE promotes BC development and SQLE inhibition may be therapeutically useful in BC treatment.

The amelioration of ovarian dysfunction by hesperidin in malathion-treated mice through the overexpression of PCNA and FSHR proteins

ObjectiveMalathion (MAL), a pesticide used for decades, is a highly toxic substance. Several studies have documented the negative effects of such agents on reproductive organ physiology, but the precise mechanism of action in the induction of ovarian dysfunction remains unclear. Therefore, the purpose of this research was to examine the effects of the antioxidant hesperidin (HES) on ovarian damage and toxicity caused by malathion. Materials and methodsIn this experiment, forty adult female bulb/c mice weighing 27–30 g were categorized into four groups, namely hesperidin (20 mg/kg, i.p.), malathion (3 mg/kg, i.p.), malathion + hesperidin, and control groups. Following a period of 35 consecutive days of treatment, mice were euthanized, and their ovarian tissues were gathered for the purposes of histopathological analysis by H&E staining, immunohistochemical assessment via proliferating cell nuclear antigen (PCNA) and follicle-stimulating hormone receptor (FSHR) immunostaining, and biochemical evaluation via measuring the levels of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1β). In addition, serum samples were collected from the blood of mice to perform hormonal analyses, especially 17β-estradiol (E2), progesterone (P4), luteinizing hormone (LH), and follicle-stimulating hormone (FSH). ResultsThe results demonstrated that MAL exposure resulted in the development of abnormalities in the architecture and structure of ovaries. Also, the treatment of mice with MAL led to declined follicular counts at all three stages, namely, primary, secondary, and tertiary, reduced serum levels of sex hormones, decreased immunoreactivity of FSHR and PCNA, and diminished activity of CAT and SOD enzymes. In contrast, it caused an increase in MDA, IL-1β, and TNF-α, as well as the count of atretic follicles. Nonetheless, it was observed that HES exhibited the ability to ameliorate the deleterious impacts of malathion across all the aforementioned parameters. ConclusionTreatment with HES via upregulating the protein expression of PCNA and FSHR and activating antioxidant defense was able to ameliorate the adverse effects of MAL on ovarian tissues.

The E301R protein of African swine fever virus functions as a sliding clamp involved in viral genome replication.

Sliding clamp is a highly conserved protein in the evolution of prokaryotic and eukaryotic cells. The sliding clamp is required for genomic replication as a critical co-factor of DNA polymerases. However, the sliding clamp analogs in viruses remain largely unknown. We found that the ASFV E301R protein (pE301R) exhibited a sliding clamp-like structure and similar functions during ASFV replication. Interestingly, pE301R is assembled into a unique ring-shaped homotetramer distinct from sliding clamps or proliferating cell nuclear antigens (PCNAs) from other species. Notably, the E301R gene is required for viral life cycle, but the pE301R function can be partially restored by the porcine PCNA. This study not only highlights the functional role of the ASFV pE301R as a viral sliding clamp analog, but also facilitates the dissection of the complex replication mechanism of ASFV, which provides novel clues for developing antivirals against ASF.

Proliferating cell nuclear antigen promotes cell proliferation and tumorigenesis by up-regulating STAT3 in non-small cell lung cancer

Proliferating cell nuclear antigen (PCNA) functions as a bridging molecule, which targets proteins that have distinct roles in cell growth. The expression of PCNA is dysregulated in some tumors and takes part in the progression of oncogenesis. However, the roles of PCNA in the progression of non-small cell lung cancer (NSCLC) remain unknown. The present study aimed to investigate the function of PCNA in the occurrence and development of NSCLC and its underlying molecular mechanisms. Western blotting, RT-PCR, and immunohistochemistry assays were used to detect the expression pattern of PCNA in NSCLC tissues and cells. A log rank test was performed to compare the overall survival (OS) of patients with high/low expression of PCNA. Besides, the relationship between PCNA and signal transducer and activator of transcription-3 (STAT3) proteins were evaluated. Then, MTT, flow cytometry, clonal formation, and in vivo xenograft assays were conducted to investigate the effects of PCNA/STAT3 on cell growth, clonal formation, apoptosis, and tumorigenesis. Results showed that PCNA expression was elevated in NSCLC tissues and cells and it could combine with STAT3 and increased its expression and phosphorylation. Moreover, the expression of PCNA showed a positive correlation with the TNM grade and occurrence rate of the lymphatic metastasis and poor prognosis of NSCLC patients. Overexpression of PCNA promoted cell proliferation, clonal formation, and tumorigenesis in lung cancer cells and inhibited cell apoptosis. In contrast, these effects were inhibited when knockdown of STAT3. In conclusion, this study demonstrates that PCNA functions as an oncogene in the progression of NSCLC through up-regulation of STAT3. These findings point to a potentially new therapeutic strategy for NSCLC.

Selective inhibition T2AA for human PCNA over PCNA homolog in Trypanosoma brucei

Proliferating cell nuclear antigen (PCNA) coordinates many functions including cell cycle progression and DNA replication in eukaryotic cells. Inhibition of the PCNA protein function in Trypanosoma brucei could be a new strategy in controlling Human African Trypanosomiasis. In the present study, we explored the function of TbPCNA by deregulation the protein expression through the overexpression, and by applying the small molecule inhibition. Overexpression of human PCNA or T. brucei PCNA wild-type proteins inhibits the parasite proliferation. On the other hand, T. brucei that overexpress the HsPCNA M40A or TbPCNA M40A mutants grew normally, indicating that inhibition of PIP-box protein interaction is important for the lethal phenotype. In testing this hypothesis, we applied the small molecule inhibitor T2 amino alcohol (T2AA). Proliferation in parasites that overexpress HsPCNA resumed after T2AA treatment, but not parasites that overexpressed TbPCNA. We concluded that T2AA selectively inhibits HsPCNA not TbPCNA. This data presented here will be a prerequisite for investigating TbPCNA interacting proteins and discovering inhibitors that specifically target TbPCNA to kill the parasite.

Effect of sirolimus on arteriosclerosis induced by advanced glycation end products via inhibition of the ILK/mTOR pathway in kidney transplantation recipients

To investigate the effect and related mechanism of sirolimus (SRL) in arteriosclerosis(AS) induced by advanced glycation end products (AGEs) in kidney transplantation recipients (KTRs). Human kidney tissues from KTRs before and after treatment with SRL were assessed by hematoxylin-eosin and immunohistochemical staining. Rat vascular smooth muscle cells (VSMCs) were treated with AGEs and/or SRL. The expressions of α-smooth muscle actin (α-SMA), osteopontin (OPN), actinin-associated LIM protein (ALP), proliferating cell nuclear antigen (PCNA), integrin-linked kinase (ILK) and the mTOR signaling pathway proteins were examined using western blot assay. Cytosolic calcium present in VSMCs was also measured by the calcium assay kit and von Kossa staining assay. The expression of α-SMA was remarkably higher while OPN expression was significantly lower in recipients with AS after they were administered SRL. Rat VSMCs treated with AGEs exhibited significantly lower expression of α-SMA and overexpression of OPN, ALP and PCNA than the other groups. In contrast, the expression of α-SMA was significantly higher while the expression of OPN, ALP and PCNA was significantly lower in VSMCs treated with both AGEs and SRL. Moreover, the ILK/mTOR signaling pathway was activated in rat VSMCs treated with AGEs, while treatment with AGEs and SRL led to significant inhibition of the ILK/mTOR signaling pathway.AGEs play a critical role in the development and progression of AS after kidney transplantation, but SRL can reverse these effects and therefore slow down the development of AS through inhibition of the ILK/mTOR signaling pathway.

Investigation on etiology of hepatic venous obstruction Budd-Chiari syndrome.

Budd-Chiari syndrome (BCS) is an uncommon clinical condition with a complex etiology. Pathogenesis of BCS is still poorly understood. We included hepatic veno-occlusive lesion tissues of 20 patients (patients group) with hepatic venous obstruction BCS and compared with 20 similar tissues with other etiologies (control group). Morphological changes in hepatic veno-occlusive lesion tissues and the positive expression of proliferating cell nuclear antigen (PCNA), C-myc, and P-53 were observed by the pathological examination (H&E staining) and immunohistochemistry assay. Our results showed that PCNA and C-myc positive cell densities were significantly higher in patient group than control group. P-53 positive cell density showed increasing trends in patients than control group. Moreover, we observed irregular hyperplasia in intimal tissue, fibrous connective tissue, and smooth muscle cell, accompanied by tissue degeneration (hyaloid degeneration and fibrinoid degeneration) and a large quantity of inflammatory cell infiltration. In conclusion, an overexpression of PCNA, C-myc, and a weak positive expression of P53 might launch the extremely irregular hepatic venous intimal hyperplasia, which is probably one of the etiologies of hepatic venous obstruction BCS.

Human papillomavirus infection a favorable prognostic factor in laryngeal squamous cell carcinoma is associated with the expression of proliferating cell nuclear antigen

It has been documented that human papilloma virus (HPV) DNA replication requires proliferating cell nuclear antigen (PCNA). However the association between them in tumors is still controversial. Up to now, the role of HPV in laryngeal squamous cell carcinoma (LSCC) has not been clearly established, and the correlation between HPV and PCNA in LSCC remains poorly explored. We retrospectively reviewed the clinicopathological features and follow-up data of 71 patients with LSCC. The lesions were examined for PCNA using immunohistochemistry, and for HPV using in situ hybridization. 31 (43.7%) cases showed infection of HPV and 38 (53.5%) showed overexpression of PCNA. No significant difference of HPV status in clinicopathological features was found. While there was a significant difference of PCNA expression in histology grade but no significant difference of PCNA expression in other clinicopathological features could be detected, and the expression of PCNA is not a significant predictor of survival in LSCC patients. However, HPV infection is a favorable prognostic factor in LSCC patients. Moreover, HPV infection is associated with PCNA overexpression. Human papilloma virus (HPV) infection is an indicator of better prognosis in LSCC and associated with the expression of PCNA.

P53 and PCNA is Positively Correlated with HPV Infection in Laryngeal Epitheliopapillomatous Lesions in Patiets with Different Ethnic Backgrounds in Xinjiang

To explore the correlation of human papillomavious (HPV) infection with expression of p53 and proliferating cell nuclear antigen (PCNA) in patients with different ethnicity in Xinjiang, China. 166 biopsy specimens from 83 laryngeal squamous cell carcinomas (LSCC), 63 laryngeal papillomas (LP), and 20 laryngeal inflammatory polyps (LIP) were included in this study. HPV infection was determined by polymerase chain reaction (PCR) using specific types of HPV primers. Expression of p53 and PCNA was assessed using immunohistostaining. The frequency of HPV 6/11 was higher in LP (33.3%) than in LSCC (9.6%) (P<0.0005), whereas the frequency of HPV 16/18 was higher in LSCC (37.3%) than in LP (6.3%) (P<0.0005). Patients of the Han ethnic group with LSCC had a higher infection rate with HPV 6/11 or HPV 6/11 and HPV 16/18 coinfection than those of Uygur and Kazak ethnicity (P<0.05). Overexpression of p53 and PCNA were higher in LSCC (62.7%, 57.8%) than in LP (38%, 33.3%) (P<0.005, and P<0.005, respectively). That of p53 was not associated with lymph-node metastases and clinical stages, but overexpression of PCNA closely correlated with clinical stage. These results strongly implicate HPV6/11 infection in the carcinogenesis of LSCC and LP, respectively. There was a higher coincidence of increased malignancy of laryngeal tumors with overexpression of p53 and PCNA. Overexpression of p53 may serve as an early risk marker for malignant transformation in HPV infected cells while the overexpression of PCNA may serve as a late marker for progression of LSCC.

PCNA: a novel cancer-associated ligand for the NK cell receptor NKp44 (162.10)

Abstract Natural Cytotoxicity Receptors (NCRs: NKp30, NKp44, and NKp46) trigger NK cell-mediated lysis of tumors and virus-infected cells. Previous studies identified BAT3, B7-H6 and Vimentin as cellular ligands for NKp30 and NKp46, respectively. However, our knowledge of NCR-mediated recognition of cancer cells remains incomplete. NKp44 is expressed exclusively in primates and its expression is induced upon activation of NK cells. We have discovered that NKp44 directly recognizes Proliferating Cell Nuclear Antigen (PCNA), which is recruited within target cells to the NK immunological synapse. Over-expression of PCNA was found to inhibit NK cell cytotoxicity in an NKp44-dependent manner. Also, the cytoplasmic immunoreceptor tyrosine-based inhibitory motif (ITIM) in NKp44 is crucial for PCNA-meditated NK cell inhibition. Since PCNA over-expression can promote cancer survival, our study reveals a novel immune evasion mechanism. Our results also further emphasize the role of nuclear proteins as ligands for Natural Cytotoxicity Receptors.

Anti-oncogenic potentials of a plant coumarin (7-hydroxy-6-methoxy coumarin) against 7,12-dimethylbenz［a］anthracene-induced skin papilloma in mice: the possible role of several key signal proteins

Anti-cancer potentials of scopoletin (7-hydroxy-6-methoxy coumarin) separated from plant extract (Gelsemium sempervirens) were demonstrated earlier from our in vitro studies. In the present study, its in vivo effects have been evaluated in mice. Mice were chronically administered 7,12-dimethylbenz [a] anthracene (DMBA) once a week and croton oil twice a week on their back, which resulted in the development of fully grown finger-like projections (papilloma) after 24 weeks. Two subgroups of mice (drug-treated) were treated with two doses of scopoletin (50 mg and 100 mg/kg body weight) respectively while control received 2% ethyl alcohol (the "vehicle" of scopoletin). After the 24-week drug administration, expressions of several key receptors such as aryl hydrocarbon receptor (AhR) and signal proteins like p53, cytochrome P450 1A1 (CYP1A1), proliferating cell nuclear antigen (PCNA), signal transducer and activator of transcription-3 (Stat-3), survivin, matrix metalloproteinase-2 (MMP-2), cyclin D1, c-myc, tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) and caspase-3, and some anti-oxidant markers were studied. Lipid peroxidation, superoxide dismutase, catalase, glutathione peroxidase and glutathione-s-transferase in supernatant were also detected. Carcinogens induced toxicity, and over-expression of AhR, CYP1A1, PCNA, Stat-3, survivin, MMP-2, cyclin D1 and c-myc and down-regulation of p53, caspase-3 and TIMP-2. In mice treated with scopoletin, the expressions of these proteins and toxicity biomarkers were reverted. Since AhR is known to be ligand-activated by DMBA to release signals for several downstream proteins initiating reactive oxygen species generation, the down-regulation of AhR by scopoletin appeared to play a significant role in subsequent down-regulation of some key signal proteins. One possible mechanism of down-regulation of AhR may be through competitive inhibition by scopoletin. Mitogen-activated protein kinases may also have some critical role. This compound can be considered as a possible candidate for chemoprevention.

Effects of isorhynchophylline on angiotensin II-induced proliferation in rat vascular smooth muscle cells

Abstract Proliferation of vascular smooth muscle cells (VSMCs) is a crucial event in cardiovascular diseases. Isorhynchophylline, an alkaloid from a traditional Chinese medicine Gambirplant, has been used to treat cardiovascular diseases. The aim of this study was to investigate the effects of isorhynchophylline on angiotensin II (Ang II)-induced proliferation of rat VSMCs. VSMCs were isolated from rat artery and cultured for 14 days before experimentation. The effect of isorhynchophylline on Ang II-induced proliferation was evaluated by cell number, MTT assay and flow cytometry, and nitric oxide (NO) content and activity of NO synthase (NOS) were measured. The expression of proto-oncogene c-fos, osteopontin (OPN) and proliferating cell nuclear antigen (PCNA) mRNAs was measured by real-time RT-PCR. VSMC cultures were verified by morphology and immunostaining with α-smooth muscle actin. Isorhynchophylline (0.1–10.0 μM) was not toxic to VSMCs, but markedly decreased Ang II (1.0 μm)-enhanced cell number and MTT intensity, and blocked cell transition from G0/G1 to S phase. Furthermore, isorhynchophylline increased the NO content and NOS activity, and suppressed Ang II-induced over-expression of c-fos, OPN and PCNA. Thus, isorhynchophylline was effective against Ang-II induced cell proliferation, an effect that appears to be due, at least in part, to increased NO production, regulation of the cell cycle, and depressed expression of c-fos, OPN and PCNA related to VMSC proliferation.

Effects of isorhynchophylline on angiotensin II-induced proliferation in rat vascular smooth muscle cells

Proliferation of vascular smooth muscle cells (VSMCs) is a crucial event in cardiovascular diseases. Isorhynchophylline, an alkaloid from a traditional Chinese medicine Gambirplant, has been used to treat cardiovascular diseases. The aim of this study was to investigate the effects of isorhynchophylline on angiotensin II (Ang II)-induced proliferation of rat VSMCs. VSMCs were isolated from rat artery and cultured for 14 days before experimentation. The effect of isorhynchophylline on Ang II-induced proliferation was evaluated by cell number, MTT assay and flow cytometry, and nitric oxide (NO) content and activity of NO synthase (NOS) were measured. The expression of proto-oncogene c-fos, osteopontin (OPN) and proliferating cell nuclear antigen (PCNA) mRNAs was measured by real-time RT-PCR. VSMC cultures were verified by morphology and immunostaining with alpha-smooth muscle actin. Isorhynchophylline (0.1-10.0 microM) was not toxic to VSMCs, but markedly decreased Ang II (1.0 microM)-enhanced cell number and MTT intensity, and blocked cell transition from G(0)/G(1) to S phase. Furthermore, isorhynchophylline increased the NO content and NOS activity, and suppressed Ang II-induced over-expression of c-fos, OPN and PCNA. Thus, isorhynchophylline was effective against Ang-II induced cell proliferation, an effect that appears to be due, at least in part, to increased NO production, regulation of the cell cycle, and depressed expression of c-fos, OPN and PCNA related to VMSC proliferation.

Carotenoids suppress proliferating cell nuclear antigen and cyclin D 1 expression in oral carcinogenic models

The purpose of this study was to investigate the chemopreventive effect of carotenoids on proliferating cell nuclear antigen (PCNA) and cyclin D 1 expression in betel ( Areca catechu) quid extract (BQE)-induced hamster oral cancer and human KB cell models, respectively. In the in vivo animal study, 41 hamsters were divided into six groups and treated with 0.3 ml of 0.5% 9,10-dimethyl-1,2-benz[a]-anthracene, BQE, α-tocopherol, β-carotene, lycopene, lutein and mixed carotenoids for 12 weeks. After treatment, the pouches were excised and graded using an immunohistochemical assay of PCNA. In the in vitro cell experiment, KB cells were cultured, and the inhibitory effect of carotenoids (β-carotene, lycopene and lutein) on cell proliferation was evaluated. Cyclin D 1 and PCNA were evaluated in terms of cell differentiation. In the results, most of the animal lesions showed no overexpression of PCNA. However, in dysplastic lesions, PCNA expressions by the β-carotene, lutein, lycopene, mixed and vitamin E groups were less than that of the control group. In papilloma lesions, PCNA expressions by the β-carotene, mixed and vitamin E groups were less severe than that of the control group. PCNA expression by the vitamin E-treated group was less severe than that of the control group. No carcinoma was found in the lycopene or mixed groups. In the cell study, all carotenoids exerted a significant inhibitory effect on KB cell proliferation. Although lycopene suppressed KB cell proliferation at the G 0/G 1 phase with a significant decrease in PCNA expression, β-carotene and lutein possessed less of an inhibitory effect and even exhibited elevated cell proliferation at the G 2/M phase. These results indicate that different carotenoids present various suppressive abilities against PCNA and cyclin D 1 expressions in cell proliferation. In conclusion, carotenoids suppressed the carcinogenesis of induced hamster oral cancer and a cancer cell line by acting as a suppressor which inhibited the expressions of PCNA and cyclin D 1.

Effect of lipo-prostaglandin E1 on mesangial proliferative glomerulonephritis in rats.

The antinephritic effect of lipo-prostaglandin E1 prostaglandin E1 incorporated in lipid microspheres was investigated using an experimental model of mesangial proliferative glomerulonephritis (MsPGN). Twenty-two female rats were randomly divided into nephritic group (N, n = 6), lipo-prostaglandin E1 treated group (NL, n = 8) and control group (C, n = 6). Lipo-prostaglandin E1 was given intravenously at 40 microg x kg(-1) x d(-1) from the 6th week to the 8th week. Twenty-four h urinary protein contents and blood creatinine (Cr) were determined and the pathological changes were observed in the experiment. The expression of proliferating cell nuclear antigen (PCNA), extracellular matrix (fibronectin, FN; collagen type IV, Col IV) and transforming growth factor beta1 (TGFbeta1) was detected by using immunohistochemistry. The results showed that lipo-prostaglandin E1 significantly inhibited the glomerular histopathological changes as well as the elevation of plasma Cr (P < 0.05). The overexpression of PCNA, FN, Col IV and TGFbeta1 were also obviously inhibited in group NL as compared with the group N (P < 0.01). It was suggested that lipo-prostaglandin E1 could improve renal function, inhibit the proliferation of glomerular cells and reduce the deposition of extracellular matrix, which may be related to the down-regulation of the TGFbeta1 expression.

Expression of cell cycle regulator p57kip2, cyclinE protein and proliferating cell nuclear antigen in human pancreatic cancer: An immunohistochemical study

To investigate the effects of p57(kip2), cyclinE protein and proliferating cell nuclear antigen (PCNA) on occurrence and progression of human pancreatic cancer. The expression of p57(kip2), cyclinE protein and PCNA in tumor tissues and adjacent tissues from 32 patients with pancreatic cancer was detected by SP immunohistochemical technique. The positive expression rate of p57(kip2) protein in tumor tissues was 46.9%, which was lower than that in adjacent pancreatic tissues (chi(2) = 5.317, P<0.05). p57(kip2) protein positive expression remarkably correlated with tumor cell differentiation (P<0.05), but not with lymph node metastasis (P>0.05). The positive expression rate of cyclinE protein in tumor tissues was 68.8%, which was higher than that in adjacent pancreatic tissues (chi(2) = 4.063, P<0.05). CyclinE protein positive expression significantly correlated with tumor cell differentiation and lymph node metastasis (P<0.05). The positive expression rate of PCNA in the tumor tissues was 71.9%, which was higher than that in adjacent pancreatic tissues (chi(2) = 5.189, P<0.05). PCNA positive expression remarkably correlated with tumor cell differentiation and lymph node metastasis (P<0.05). The decreased expression of p57(kip2) and/or overexpression of cyclinE protein and PCNA may contribute to the occurrence and progression of pancreatic cancer. p57(kip2), cyclinE protein, and PCNA play an important role in occurrence and progression of pancreatic cancer.

Expression of p120, Ki‐67 and PCNA as proliferation biomarkers in imprint smears of prostate carcinoma and their prognostic value

The cell proliferation markers p120, Ki-67 and proliferating cell nuclear antigen (PCNA) recognize nuclear antigens. The expression of these proteins by immunostaining methods was reported to be of value in determining the prognosis of patients with malignant diseases. In this study, we evaluated the prognostic significance of the expression of nuclear antigens p120, PCNA and Ki-67 in prostate cancer and compared the results with other prognostic factors. Imprint smear samples obtained from 70 patients immediately after radical prostatectomy for prostatic carcinoma were immunostained with monoclonal antibodies against p120, Ki-67 and PCNA. The immunostaining results were correlated with Gleason score, tumour differentiation, stage and prostatic specific antigen (PSA) levels. Our findings demonstrate that p120, Ki-67 and PCNA expression in prostatic carcinoma smears, correlated significantly with the degree of Gleason score (P < 0.001). When combining p120, Ki-67 and PCNA positivity with tumour differentiation there was a significant association among these parameters (P < 0.001). Overexpression of p120, Ki-67 and PCNA, was also associated with increased PSA serum levels (>4 ng/ml) (P < 0.001). The distribution of p120, Ki-67 and PCNA expression in prostate carcinomas was not statistically significant for Ki-67 (P = 0.69) and p120 (P = 0.22) but was significant for PCNA (P < 0.001) as far as the histological stage (T2a, T2b, T2c, T3a). P120, Ki-67 and PCNA expression had significant prognostic value for disease-free survival. Our results conclude that nuclear antigens p120, Ki-67 and PCNA appear to be additional markers in the field of prognosis of prostatic carcinoma.

Dominant-negative cAMP-responsive Element-binding Protein Inhibits Proliferating Cell Nuclear Antigen and DNA Repair, Leading to Increased Cellular Radiosensitivity

Selective inhibition of the epidermal growth factor receptor or mitogen-activated protein kinase (MAPK) results in radiosensitization of cancer cells. One potential mechanism involves cAMP-responsive element-binding protein, which is activated by radiation via the epidermal growth factor receptor/MAPK pathway and which regulates synthesis of proliferating cell nuclear antigen (PCNA), a protein involved in repair of ionizing radiation-induced DNA damage. To test for a role of CREB in cellular radiosensitivity, CHO cells were transfected with plasmids expressing dominant-negative CREB mutants (CR133 or KCREB), and various end-points were measured 48 h later. Basal levels of PCNA-CAT reporter construct activity were reduced by 60 and 40% following expression of CR133 and KCREB, respectively; similar decreases were observed in PCNA protein levels. Pulsed-field gel electrophoresis measurements showed that CR133 inhibited the repair of radiation-induced DNA double-strand breaks, and this effect was reversed by over-expression of PCNA; dominant-negative CREB also significantly inhibited split-dose recovery. Clonogenic assays were used to determine surviving fraction; the dose enhancement ratios for dominant-negative CREB-expressing cells compared with control (vector alone) were 1.5 and 1.3 for CR133 and KCREB, respectively. Importantly, co-transfection of mutant CREB and a construct constitutively expressing PCNA protein restored radiosensitivity of CHO cells back to wild-type levels. Moreover, cells expressing either CREB mutant showed no significant cell cycle redistribution. These data demonstrate that genetic disruption of CREB results in radiosensitization, and that this effect can be explained by a mechanism involving decreased PCNA expression and inhibition of DNA repair.

Role of the increase in p21 in cisplatin-induced acute renal failure in rats.

The goal of this study was to clarify the role of p21, a cyclin-dependent kinase inhibitor, in acute renal failure (ARF). This was accomplished with the examination of the renal expression of p21 in cisplatin (CDDP)-induced ARF and in rechallenge injury with CDDP. The injection of CDDP (5 mg/kg) into rats induced increases in serum creatinine and tubular damage and the number of in situ DNA nick end labeling-positive cells, which peaked at day 5, followed by recovery to control levels by day 14. The rechallenge with the same dose of CDDP 14 d after the first dose of CDDP induced significantly less injury and no significant increase in in situ DNA nick end labeling-positive cells. The first CDDP dose significantly increased p53-positive nuclei at day 1, which disappeared by day 5, and the number of p21-positive nuclei, which had two peaks on days 3 and 9. The number of proliferating cell nuclear antigen (PCNA)-positive nuclei peaked at days 3 and 12. A significant increase in the incorporation of 5-bromo 2'-deoxyuridine (BrdU) was found at day 5 and peaked at day 7. The second injection of CDDP induced significant increases in the number of p21-, p53-, and PCNA-positive nuclei within 2 d but did not affect the incorporation of BRDU: These findings suggested that (1) CDDP induced two peaks of the increase in p21; (2) the first peak occurred shortly after CDDP and was accompanied by overexpression of p53 and PCNA but not with BrdU incorporation, possibly reflecting G1 arrest and DNA repair; (3) the second peak of p21 occurred through an p53-independent pathway and may contribute to cell differentiation; and (4) the overexpression of p21 and PCNA in rechallenge injury may contribute to acquired resistance in CDDP-induced ARF via enhanced DNA repair.

Disruption of nucleotide excision repair by the human T-cell leukemia virus type 1 Tax protein.

The Tax protein of human T-cell leukemia virus type 1 (HTLV-1) is a transcriptional transactivator and viral oncogene. Since cellular transformation has been frequently linked to alterations in genome stability, we investigated the effect of Tax on nucleotide excision repair (NER), a prominent cellular DNA repair pathway. Cells expressing Tax exhibited a reduced capacity for NER as measured by unscheduled DNA synthesis and host cell reactivation assays. The cellular proliferating cell nuclear antigen (PCNA) gene product regulates DNA replication and repair pathways, including NER. Since Tax activates transcription of the PCNA promoter, we investigated whether this activity contributes to the reduction of NER. Tax increased endogenous PCNA protein expression, and analysis of Tax mutant proteins demonstrated that the reduction in NER correlated with Tax transactivation of PCNA gene expression. Direct overexpression of PCNA also reduced NER. We propose that overexpression of PCNA, and disruption of NER induced by Tax, predisposes cells to accumulate DNA damage and contributes to HTLV-1 transformation.