Expression Of Mutant P53 Protein Research Articles

Overexpression of human ortholog of mammalian enabled (hMena) is associated with the expression of mutant p53 protein in human breast cancers

The human ortholog of mammalian enabled (hMena), a member of the enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) family, is an actin regulatory protein involved in the regulation of cell motility. Increasing evidence suggests that hMena overexpression is involved in human cancers, but the upstream events that influence the expression of hMena remain to be elucidated. In this study, we performed immunohistochemical analysis of the expression of hMena protein in paraffin-embedded archival tissues of infiltrating ductal carcinomas (IDCs) obtained from 52 cases. We found that elevated hMena expression is associated with larger tumor size (>2.5 cm, p<0.01), HER2 expression (p<0.05), p53 index (p<0.03) and Ki67 index (p<0.01), suggesting that hMena is a predictor of poor prognosis in IDCs. The histological characteristics of each specimen showed that hMena was overexpressed in the tumor cells at the invasive front of IDCs, indicating that hMena expression is at least partly mediated by tumor cell-matrix interactions. To explore the role of the absence of p53 function in hMena overexpression of IDCs, wild-type p53 cDNA was introduced into SW620 cells, which originally express mutant p53. In wild-type p53-transfected cells, hMena mRNA expression was decreased to 70% of the levels in mock transfected cells (p<0.01). In conclusion, our study indicates that hMena overexpression is involved in the progression of IDCs, and raises the possibility that wild-type p53 may suppress hMena expression.

Expression of mutant protein p53 and Hsp70 and Hsp90 chaperones in cockles Cerastoderma edule affected by neoplasia

High prevalence of disseminated neoplasia has been found in cockles Cerastoderma edule of Galicia (NW Spain). Disseminated neoplasia has been associated with high mortalities of various bivalve species. In vertebrates, proteins such as p53 and heat shock proteins (HSPs) play important roles in carcinogenesis. The protein p53 has been detected in neoplastic cells of bivalve molluscs such as Mytilus edulis, Mytilus trossulus, Mya arenaria, Spisula solidissima, Crassostrea rhizophorae and Crassostrea gigas. In this study, western blotting analyses were used to test the expression of Hsp70, Hsp90 and mutant p53 proteins in the cells and plasma of the haemolymph of cockles showing various intensities of neoplasia. Disseminated neoplasia was previously diagnosed by examination of stained haemolymph monolayers with light microscopy. In the present study, mutant p53 was detected in haemolymph cells of cockles diagnosed as affected by moderate and heavy neoplasia intensity, whereas it was not detected in cockles with either no or light neoplasia. The higher the neoplasia intensity, the higher the levels of Hsp70 and Hsp90. These proteins were not found in plasma. The results reveal the possible association between p53 and HSPs in neoplastic cells of cockles, which could prevent p53 from carrying out its functions, as occurs in human cancers.

Abstract 1629: Restoration of the wild type function to mutant p53 by chemopreventive agent phenethyl isothiocyanate

Abstract p53 mutations occur in more than 50% of all human tumor. Mutant p53 is incapable of activating downstream target genes necessary for cell cycle arrest and apoptosis. Phenethyl isothiocyanate (PEITC), a cruciferous vegetable-derived compound, has been shown to possess anti-cancer property by causing cell growth arrest or apoptosis in tumor cell lines and animal models. Recently, we have found that PEITC can selectively reduce mutant p53, but not wild type protein levels in a variety of tumor cell lines. Here, we demonstrate that PEITC can increase sequence specific DNA binding of p53 in NSCLC H596 cells expressing mutant p53 and induce the expression of p53-dependent target proteins, such as p21 and Noxa. Similar effects were observed in human glioblastoma T98G cells which also express mutant p53. H596 cells incubated with sulforaphane (SFN), another widely studied ITC compound with much weaker cytotoxicity, showed no increased specific DNA binding of p53. In addition, PEITC induced p53-responsive p21 and Noxa promoter luciferase activity. Blocking mutant p53 protein expression with shRNA in T98G cells entirely prevented p21 protein induction triggered by PEITC. Immunoprecipitation studies with conformation-specific p53 antibodies (Pab1620 and Pab240) show that treatment with PEITC alters mutant p53 to wild type conformation in H596 cells. Currently, we are investigating the significance of function restoration to mutant p53 by phenethyl isothiocyanate in the regulation of apoptosis by PEITC or other conventional chemotherapeutic drugs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1629.

Expression of mutant p53 and of the multidrug resistant proteins P-glycoprotein and glutathione S-transferase-pi correlated in colorectal adenocarcinoma

Objective. Accumulating studies suggest that multidrug resistance is related to expression of p53, P-glycoprotein (Pgp) and Glutathione S-Transferase-pi (GST-pi). This study was to estimate mutant p53 expression and its correlation with drug resistance related proteins Pgp and GST-pi expression in colorectal adenocarcinoma patients. Material and methods. Immunohistochemical ABC technique was used to detect the expression of mutant p53 protein, Pgp and GST-pi in 404 cases with colorectal adenocarcinoma. Results. A low frequency of mutant p53 accumulation was observed, consistent with findings in colorectal cancers (CRCs) from other Asian populations. Accumulation of mutant p53 was related to AJCC staging (p < 0.05). Pgp expression was significantly correlated with tumor location (p = 0.039) and gender (p = 0.043). The positive percentage of Pgp and GST-pi expression was all significantly higher in mutant p53 protein positive group than mutant p53 protein negative cases (r = 0.634, p < 0.001 and r = 0.680, p < 0.001, respectively). Conclusions. These findings demonstrate association of three biomarkers with clinicopathologic parameters of colorectal carcinoma, and overexpression of Pgp and GST-pi was closely correlated with mutant p53.

The ubiquitin–proteasome system is inhibited by p53 protein expression in human ovarian cancer cells

The ubiquitin–proteasome system (UPS) and autophagy provide major cellular pathways for protein degradation. Since the p53 pathway controls autophagy, we investigated whether p53 regulates UPS in ovarian tumour cell lines. A reporter cell line (SKOV3-EGFPu) was established to measure UPS function against a constant genetic background. Transient expression of either wild type or mutant p53 in SKOV3-EGFPu cells reduced UPS activity as compared to vector control. These results, together with those from endogenous p53 expression in seven ovarian cancer cell lines, suggest that expression of both wild-type and mutant p53 protein impairs UPS function. Thus, p53 expression may regulate protein homeostasis by down-regulating UPS function in response to cellular stress.

Serological levels of mutated p53 protein are highly detected at early stages in breast cancer patients.

The aim of this study was to compare the sensitivity of the serological level of anti-p53 antibodies in breast cancer patients and to correlate its expression level with patient age, histological stage and grade of tumor differentiation. Total p53 protein expression (mutant and wild-type) was also determined in the breast cancer tissues using immunohistochemistry (IHC). The serological levels of mutant p53 expression were found to be age-dependent, reaching the highest level at 50 years of age. Faint or low detection was observed in patients ≤30 years of age. Anti-p53-antibodies were detected in patients ≤40 and ≥61 years of age. The serological levels of mutant p53 protein were highly detected in all stages of breast cancer, including the early stages. However, anti-p53 antibodies reached a high level of detection only in stage III breast carcinomas. No expression was found in patients with benign breast disease. The detection of p53 mutations was dependent on the grade of tumor differentiation, achieving the highest level in the poorly differentiated breast carcinomas. Results from IHC were highly correlated with serological p53 mutational analysis. Our findings indicate that mutant p53 in serum is a promising novel parameter for the evaluation of cellular biology and the prognosis of breast cancer from its early stages using blood samples. Anti-p53 antibodies were demonstrated to be less sensitive in this study. It is also possible to use the expression of mutant p53 protein as a molecular marker to differentiate benign breast disease from breast carcinoma prior to surgery.

Mutant p53 mediates survival of breast cancer cells

Background:p53 is the most commonly mutated tumour-suppressor gene in human cancers. Unlike other tumour-suppressor genes, most p53 cancer mutations are missense mutations within the core domain, leading to the expression of a full-length mutant p53 protein. Accumulating evidence has indicated that p53 cancer mutants not only lose tumour suppression activity but also gain new oncogenic activities to promote tumourigenesis.Methods:The endogenous mutant p53 function in human breast cancer cells was studied using RNA interference (RNAi). Gene knockdown was confirmed by quantitative PCR and western blotting. Apoptosis was evaluated by morphological changes of cells, their PARP cleavage and annexin V staining.Results:We show that cancer-associated p53 missense mutants are required for the survival of breast cancer cells. Inhibition of endogenous mutant p53 by RNAi led to massive apoptosis in two mutant p53-expressing cell lines, T47D and MDA-MB-468, but not in the wild-type p53-expressing cells, MCF-7 and MCF-10A. Reconstitution of an RNAi-insensitive mutant p53 in MDA-MB-468 cells completely abolished the apoptotic effects after silencing of endogenous mutant p53, suggesting the specific survival effects of mutant p53. The apoptotic effect induced by mutant p53 ablation, however, is independent of p63 or p73 function.Conclusion:These findings provide clear evidence of a pro-survival ‘gain-of-function’ property of a subset of p53 cancer mutants in breast cancer cells.

Expression of Mutant p53 Proteins Implicates a Lineage Relationship between Neural Stem Cells and Malignant Astrocytic Glioma in a Murine Model

Recent studies have identified genes and core pathways that are altered in human glioblastoma. However, the mechanisms by which alterations of these glioblastoma genes singly and cooperatively transform brain cells remain poorly understood. Further, the cell of origin of glioblastoma is largely elusive. By targeting a p53 in-frame deletion mutation to the brain, we show that p53 deficiency provides no significant growth advantage to adult brain cells, but appears to induce pleiotropic accumulation of cooperative oncogenic alterations driving gliomagenesis. Our data show that accumulation of a detectable level of mutant p53 proteins occurs first in neural stem cells in the subventricular zone (SVZ) and that subsequent expansion of mutant p53-expressing Olig2(+) transit-amplifying progenitor-like cells in the SVZ-associated areas initiates glioma formation.

Mutant p53 and cyclin A1 protein expression in primary laryngeal squamous cell carcinomas do not correlate to second primary tumours of the head and neck*

Field cancerization is a feature of head and neck squamous cell carcinoma. No biological marker in the index tumour has been correlated to the development of second primary tumours (SPT). Cyclin A1 is a cell cycle regulator and a downstream target of p53. This study assessed predictive correlation of cyclin A1 and mut-p53 with clinicopathological parameters and occurrence of (SPT) in the head and neck. Using immunohistochemistry 106 patients treated for primary laryngeal squamous cell carcinoma were investigated for expression of cyclin A1 and mut-p53. Expression of cyclin A1 and mut-p53 were noted in 83 of 106 (78.3%) and 25 of 106 (23.6%) patients. There was a weak but significant correlation between mut-p53 and cyclin A1 (r = 0.301, P = 0.002) expression. During the follow-up period (median 41.0 months (range 1-205 months)), 21 of 106 (19.8%) patients developed an SPT. There was no statistically significant correlation between the markers investigated and disease recurrence, SPT diagnosis or clinicopathological parameters. Second primary tumours are an intriguing problem in treatment of HNSCC and a predictive marker identifying those greatest at risk would be a leap forward.

Influência da localização do tumor na expressão tecidual da proteína p53 em doentes com câncer colorretal: estudo de 100 casos

OBJETIVO: O objetivo do presente estudo foi verificar, se existem diferenças na expressão tecidual da proteína p53 segundo a localização do tumor em doentes com câncer colorretal. MÉTODO: Foram estudados 100 doentes (54 mulheres), com média de idade de 59,8 anos com adenocarcinoma colorretal. A expressão da proteína p53 foi analisada por imunoistoquímica, com anticorpo monoclonal anti-p53 pela técnica da estreptavidina-biotina-peroxidase. A expressão tecidual da proteína p53 foi relacionada às variáveis: gênero, idade, grau histológico, tipo histológico, tamanho do tumor, estadiamento TNM, profundidade de invasão da parede intestinal, comprometimento linfonodal, invasão angiolinfática, localização do tumor no intestino grosso em relação à flexura esplênica. Na avaliação estatística da relação entre expressão da proteína p53 e as variáveis consideradas empregou-se o teste qui-quadrado, estabelecendo-se nível de significância de 5% (p&lt;0,05). RESULTADOS: A proteína p53 foi positiva em 77% dos casos. Com relação as diferentes variáveis consideradas verificou-se maior tendência de expressão da proteína mutante quando se considerava a idade (p=0,001), grau histológico (p=0,001), tipo histológico (p=0,001), estádios tardios da classificação TNM (p=0,001), maior profundidade de invasão na parede cólica (p=0,001), comprometimento linfonodal (p=0,001), invasão angiolinfática (p=0,02), localização após a flexura esplênica (p=0,001), não se encontrando relação com gênero (p=0,49) e tamanho do tumor (p=0,08). CONCLUSÃO: Os resultados do presente estudo permitem concluir que a expressão da proteína p53 mutante ocorre com maior freqüência nos tumores localizados a partir da flexura esplênica.

Antitumor effects of saponin extract from Patrinia villosa (Thunb.) Juss on mice bearing U14 cervical cancer

Saponin extracted from Patrinia villosa (Thunb.) Juss (SPVJ) is a Chinese medicine which is used widely by traditional medicine doctors. In this study, the antitumor effects and the possible mechanisms of SPVJ were investigated in mice bearing U14 cervical cancer. The results showed that SPVJ (50 mg/kg and 100 mg/kg) effectively reduced the weight of U14 cervical tumor (35.1% and 57.1%, respectively). Compared with the control group, SPVJ (100 mg/kg) significantly increased tumor cells in the G0/G1 phase (38.1% vs 68.5%), increased the number of cells in apoptosis (9.4% vs 28.9%) and G0/G1 phase and decreased the number of cells in S phase (41% vs 26.2%) and G2/M (20.9% vs 5.3%), inhibited proliferating cell nuclear antigen (PCNA) of tumor cell (80.6% vs 21.8%), decreased the expression of mutant p53 (66.4% vs 33.5%) and bcl-2 protein (78.2% vs 20.3%). The mechanism of the SPVJ antitumor effect might be associated with inhibition of tumor cells in G0/G1 phase, inducing apoptosis and inhibiting the expression of PCNA, mutant P53 and Bcl-2 protein.

Induction of genetic instability by gain-of-function p53 cancer mutants

p53 plays critical roles in tumor suppression and the loss of its function is required for cancer progression. In this context, the p53 gene is the most commonly mutated tumor suppressor gene in human cancers. The majority of the p53 gene mutations in human cancers are missense mutations, leading to the expression of the full-length mutant p53 protein in cancer cells. In addition to the loss of tumor suppression activity, p53 cancer mutants gain new oncogenic activities to promote tumorigenesis and drug resistance. Recent studies have identified a novel gain-of-function of p53 cancer mutants in inducing genetic instability by inactivating critical tumor suppressors such as ATM. Genetic instability is a common mechanism by which cancer cells efficiently accumulate genetic mutations to promote their growth, survival and metastatic potential. Therefore, this gain-of-function of p53 cancer mutants could play important roles in tumorigenesis and drug resistance of various types of human cancers. In addition, because many cancer therapies such as radiation therapy suppress or kill cancer cells by activating ATM-dependent responses to DNA double-stranded break damage, elucidation of this gain-of-function of p53 cancer mutants will have important implications on cancer therapy.

Arsenic salt-induced DNA damage and expression of mutant p53 and COX-2 proteins in SV-40 immortalized human uroepithelial cells

Arsenic is widely distributed in the environment, and is a proven toxic and carcinogenic agent that is associated with various human malignancies, including bladder cancer. However, the mechanisms of its carcinogenic action are still not well understood. In addition, over-expression of mutant p53 and cyclooxygenase-2 (COX-2) frequently occurs in a variety of human malignancies. It is therefore of interest to study the genotoxicity of arsenic salts on human uroepithelial cells and the expression of oncoproteins p53 and COX-2. In this study, the relative genotoxicity of sodium arsenite was evaluated in SV-40 immortalized human uroepithelial cells (SV-HUC-1) using the alkaline comet assay. The expression of mutant p53 and COX-2 was also evaluated by immunocytochemistry and western blotting. Our results revealed that sodium arsenite was able to induce DNA damage, and that its genotoxicity is correlated with its concentration. In addition, the expression of mutant p53 increased in parallel with comet scores, and the maximal expression of mutant p53 was observed at 4 microM arsenite. Similarly, sodium arsenite stimulated a concentration-dependent increase in COX-2 expression. In conclusion, this study demonstrated that sodium arsenite is genotoxic to uroepithelial cells in vitro, and that it will induce expression of mutant p53 and COX-2 proteins, indicating a possible key event in carcinogenesis. This study provides us with knowledge of the relationship between p53 and COX-2 over-expression in arsenite-treated urothelial cells and suggests a potential therapeutic role of COX-2 inhibitors in human urothelial malignancies.

Antitumor Activity of the Procyanidins from &lt;i&gt;Pinus koraiensis&lt;/i&gt; Bark on Mice Bearing U14 Cervical Cancer

Pinus koraiensis Bark Procyanidins Extract (PKBPE) has been used in traditional Chinese medicine for thousands of years. In this study, we determined PKBPE effect on tumor weight, SOD (superoxidate dismutase) activity, the content of MDA (malondialdehyde) through colorimetric analysis antigenic, and expression of Ki-67, p53 and Bcl-2 on mice bearing U14 cervical cancer. Treatment with PKBPE (158 and 250 mg/kg body weight, p.o.) could inhibit U14 cervical carcinoma growth up to 47.68 and 58.94%. In addition, PKBPE enhance the activity of SOD (p<0.01) and decrease MDA content. Furthermore, we also observed that PKBPE treatment significantly inhibited the expression of Ki-67, mutant p53 and Bcl-2 protein (p<0.01). The results suggested that PKBPE showed antitumor activities on U14 cervical carcinoma mice. The mechanism of PKBPE antitumor activity might be associated with free radical production inhibition and regulation of the expression of Ki-67, mutant p53 and Bcl-2 protein.

Detection of Mutant p53 Protein in Workers Occupationally Exposed to Benzidine

To investigate the expression of mutant p53 protein in workers occupationally exposed to benzidine, we detected mutant p53 protein by immuno-PCR assay in the serum of 331 benzidine-exposed healthy workers, while we classified exfoliated urothelial cells in urine samples with Papanicoloau's grading (PG). The Papanicoloau's grading classified exfoliated urothelial cells of the subjects from grade I (normal cells) to grade III (suspicious malignant cells). The subjects were also divided into high, medium and low exposure groups according to the exposure intensity index. The results revealed that mutant p53 protein in the medium and high exposure groups were significantly higher than the in low exposure group (p<0.05), and in PG II and III were significantly higher than in the PG I (p<0.05). There was no significant differences among Papanicoloau's gradings strata in the low exposure group on the incidence and quantity of mutant p53 protein. In the medium and high exposure groups, the incidence and/or quantity of mutant p53 protein in the stratum of PG II and/or III were significantly higher than that of PG I (p<0.05). Detection of mutant p53 protein in conjunction with benzidine exposure level and Papanicoloau's gradings of exfoliated urothelial cells could provide more information to help us elevate surveillance efficiency and diagnose bladder cancer in the early period.

Tumor progression and chemoradiosensitivity in relation to the expression of apoptosis related proteins in esophageal squamous cell carcinoma

4588 To study apoptosis related protein expression and their impact on patient’s survival time and sensitivity to postoperative chemoradiotherapy (CRT), we examined the expression of RB, mutant p53, MDM2 and Bax proteins using immunohistochemistry in 115 (CRT; 42) surgically resected esophageal squamous cell carcinoma (ESCC). We also investigated the survivin mRNA expression with quantitative analysis by real-time RT-PCR in 57 (CRT; 30) patients with ESCC. CRT contained 40–60 Gy radiation and continuous infusion of 5-FU (300mg/sqm, day1–5qw). Expression of RB, mutant p53, MDM2, Bax proteins and survivin mRNA were detected in 65%, 46%, 33%, 37% and 32% of patients, respectively. Patients with RB(+), MDM2(-), Bax(+) or survivin(-) tumor had significantly better survival rates than those with RB(-), MDM2(+), Bax(-) or survivin(+) tumor, respectively. However, there was no significant difference in survival between patients with and without mutant p53 expression. In patients not treated with CRT, those with RB(+) or survivin(-) tumor survived significantly longer than those with RB(-) or survivin(+) tumor, respectively. In patients treated with CRT, the expression of Bax protein and survivin mRNA was prognostic indicator. The 5-year survival rates of patients with Bax(+) and survivin(-) tumors were 65% and 39%, significantly superior to 21% and 0% of those with Bax(-) and survivin(+) tumors (P&lt;0.05 and P&lt;0.01, respectively). These results indicate that the expression levels of apoptosis related proteins are important for predicting the prognosis of ESCC patients. Furthermore, CRT may be effective in patients with Bax(+) or survivin(-) tumors. Further investigations are required for clarifying the relationship between the efficacy of postoperative CRT and apoptosis promoting status of ESCC. No significant financial relationships to disclose.

Photodynamic Therapy Resistant Human Colon Carcinoma HT29 Cells Show Cross‐Resistance to UVA but not UVC Light

The isolation of photodynamic therapy (PDT)-resistant HT29 human colon adenocarcinoma cells has been reported previously. These PDT-resistant variants show increased expression of the Hsp27 and BNip3 proteins and a decreased expression of mutant p53 protein compared with parental HT29 cells. Because mutant p53 and increased expression of Hsp27 have been associated with resistance to various chemotherapeutic agents, whereas BNip3 is a potent inducer of apoptosis, we were interested in determining whether these PDT-resistant cells were cross-resistant to other cytotoxic agents. In the present report, we examined the colony survival of the PDT-resistant HT29 variants and several other clonal variants of HT29 cells to ultraviolet light (UV) treatment. The HT29 PDT-resistant variants showed cross-resistance to long-wavelength UVA (320-400 nm) but not to short-wavelength UVC (200-280 nm) light. Cell sensitivity to UVA or UVC was then correlated with Hsp27, BNip3 and mutant p53 protein levels in the PDT-resistant variants as well as in several clonal variants of HT29 cells that express different levels of Hsp27, BNip3 and mutant p53. We show that increased expression of Hsp27 and BNip3 and decreased expression of mutant p53 correlated with increased resistance to UVA. In contrast, increased expression of Hsp27 and BNip3 correlated with increased sensitivity to UVC, whereas increased expression of mutant p53 showed no significant correlation with sensitivity to UVC. These results suggest that the PDT-resistant HT29 cell variants are differentially sensitized to UVA compared with UVC due, in part at least, through the altered expression levels of BNip3, Hsp27 and mutant p53.

Gene expression signature of parathion-transformed human breast epithelial cells

Environmental substances seem to be involved in the etiology of breast cancers. Many studies have found an association between human cancer and exposure to agricultural pesticides such as the organophosphorous pesticides. Parathion is a cholinesterase inhibitor that induces the hydrolysis of body choline esters, including acetylcholine at cholinergic synapses. The primary target of action in insects is the nervous system whereby pesticides inhibit the release of the enzyme acetylcholinesterase at the synaptic junction. Atropine is a parasympatholytic alkaloid used as an antidote to acetylcholinesterase inhibitors. The aim of this study was to determine the effect of parathion and atropine on cell transformation of human breast epithelial cells in vitro. These studies showed that parathion alone was able to induce malignant transformation of an immortalized human breast epithelial cell line, MCF-10F as indicated by increased cell proliferation, anchorage independency and invasive capabilities. There was also an increase in c-kit, Trio, Rho-A, Rac-3, EGFR, Notch-4, Dvl-2, Ezrin, beta catenin and mutant p53 protein expression in the parathion-treated cells. However, atropine significantly inhibited this increase. In a human cell cycle array of 96 genes, 13 of them were altered by parathion treatment. Among the genes affected were the cyclins, such as cyclin D3, the cyclin-dependent kinases (CDKs) such as CDK41 and the minichromosome maintenance deficient (MCM) MCM2 and MCM3. It is suggested that parathion influences human breast epithelial cell transformation and is an initiator factor in the transformation process in breast cancer.

Gene and Protein Expressions Induced by 17β-estradiol and Parathion in Cultured Breast Epithelial Cells

Cancer of the breast is the most common form of malignant disease occurring among women of the western world and environmental substances seem to be involved in the etiology of this disease. Many studies have found an association between human cancer and exposure to agricultural pesticides and among them parathion, the organophosphorous pesticide used in agriculture to control mosquito plagues. The association between breast cancer and prolonged exposure to estrogens suggests that this hormone also may have a role in such process. However, the causative factors for breast carcinogenesis remain an enigma. The objective of this study was to determine the effects of 17β-estradiol (E2) and parathion on cell transformation of human breast epithelial cells in vitro. The results of this study showed that parathion alone and in combination with E2 induced malignant transformation of an immortalized human breast epithelial cell line, MCF-10F, and the malignant feature was confirmed by anchorage independency and invasive capabilities. Parathion alone efficiently elevated the expression of EGFR, c-Kit, Trio, Rac 3, Rho-A, and mutant p53 proteins. Analysis of gene expression using commercially available human cell cycle array revealed transcriptional alterations in 22 out of a total of 96 genes. Among them, nine genes involved in the regulation of cell cycle were altered. These included cyclins (A1, A2, C, G1, G2, and H), cyclin-dependent kinases (CDKs), and minichromosome maintenance deficient (MCM). Results suggest that parathion has the potency to cause malignant transformation of breast epithelial cells through modulation of expression of cell cycle regulated genes.

Gene and protein expressions induced by 17beta-estradiol and parathion in cultured breast epithelial cells.

Cancer of the breast is the most common form of malignant disease occurring among women of the western world and environmental substances seem to be involved in the etiology of this disease. Many studies have found an association between human cancer and exposure to agricultural pesticides and among them parathion, the organophosphorous pesticide used in agriculture to control mosquito plagues. The association between breast cancer and prolonged exposure to estrogens suggests that this hormone also may have a role in such process. However, the causative factors for breast carcinogenesis remain an enigma. The objective of this study was to determine the effects of 17beta-estradiol (E2) and parathion on cell transformation of human breast epithelial cells in vitro. The results of this study showed that parathion alone and in combination with E2 induced malignant transformation of an immortalized human breast epithelial cell line, MCF-10F, and the malignant feature was confirmed by anchorage independency and invasive capabilities. Parathion alone efficiently elevated the expression of EGFR, c-Kit, Trio, Rac 3, Rho-A, and mutant p53 proteins. Analysis of gene expression using commercially available human cell cycle array revealed transcriptional alterations in 22 out of a total of 96 genes. Among them, nine genes involved in the regulation of cell cycle were altered. These included cyclins (A1, A2, C, G1, G2, and H), cyclin-dependent kinases (CDKs), and minichromosome maintenance deficient (MCM). Results suggest that parathion has the potency to cause malignant transformation of breast epithelial cells through modulation of expression of cell cycle regulated genes.