Expression of nitric oxide synthase type 3 in reflux-induced esophageal lesions

A549 cells adapted to high nitric oxide show reduced surface CEACAM expression and altered adhesion and migration properties

The migration and adhesion properties of tumors affect their metastatic rate. In the present study, we investigated carcinoembryonic antigen-related cell adhesion molecule (CEACAM) 1, 5, and 6 expression in high nitric oxide (HNO)-adapted lung cancer cells compared to parent cells. We observed high transcript levels of CEACAM 1 (4S, 4L), CEACAM 5, and CEACAM 6 in HNO cells compared to parent cells. However, the surface expression was low in HNO cells. Interestingly, the intracellular protein levels were high for these three CEACAMs. We confirmed these results with immunohistochemical experiments. Further, the adhesion and migration assays showed reduced clumping in HNO-adapted A549 (A549-HNO) cells and faster migration rates, respectively. These results document the altered adhesion and migration properties of cells adapted to HNO. Further, our studies also indicate a dynamic regulation of CEACAM protein expression and surface transport in HNO cells.

Part I. Molecular and cellular characterization of high nitric oxide-adapted human breast adenocarcinoma cell lines

There is a lack of understanding of the casual mechanisms behind the observation that some breast adenocarcinomas have identical morphology and comparatively different cellular growth behavior. This is exemplified by a differential response to radiation, chemotherapy, and other biological intervention therapies. Elevated concentrations of the free radical nitric oxide (NO), coupled with the up-regulated enzyme nitric oxide synthase (NOS) which produces NO, are activities which impact tumor growth. Previously, we adapted four human breast cancer cell lines: BT-20, Hs578T, T-47D, and MCF-7 to elevated concentrations of nitric oxide (or high NO [HNO]). This was accomplished by exposing the cell lines to increasing levels of an NO donor over time. Significantly, the HNO cell lines grew faster than did each respective ("PARENT") cell line even in the absence of NO donor-supplemented media. This was evident despite each "parent" being morphologically equivalent to the HNO adapted cell line. Herein, we characterize the HNO cells and their biological attributes against those of the parent cells. Pairs of HNO/parent cell lines were then analyzed using a number of key cellular activity criteria including: cell cycle distribution, DNA ploidy, response to DNA damage, UV radiation response, X-ray radiation response, and the expression of significant cellular enzymes. Other key enzyme activities studied were NOS, p53, and glutathione S-transferase-pi (GST-pi) expression. HNO cells were typified by a far more aggressive pattern of growth and resistance to various treatments than the corresponding parent cells. This was evidenced by a higher S-phase percentage, variable radioresistance, and up-regulated GST-pi and p53. Taken collectively, this data provides evidence that cancer cells subjected to HNO concentrations become resistant to free radicals such as NO via up-regulated cellular defense mechanisms, including p53 and GST-pi. The adaptation to NO may explain how tumor cells acquire a more aggressive tumor phenotype.

Association between polymorphisms in cancer-related genes and early onset of esophageal adenocarcinoma

There is an increasing incidence of esophageal adenocarcinoma (EA) among younger people in the western populations. However, the association between genetic polymorphisms and the age of EA onset is unclear. In this study, 1330 functional/tagging single-nucleotide polymorphisms (SNPs) from 354 cancer-related genes were genotyped in 335 white EA patients. Twenty important SNPs that have the highest importance scores and lowest classification error rate were identified by the random forest algorithm to be associated with early onset of EA (age ≤ 55 years). Subsequent logistic regression analysis indicated that 10 SNPs (rs2070744 of NOS3, rs720321 of BCL2, rs17757541 of BCL2, rs11775256 of TNFRSF10A, rs1035142 of CASP8, rs2236302 of MMP14, rs4740363 of ABL1, rs696217 of GHRL, rs2445762 of CYP19A1, and rs11941492 of VEGFR2/KDR) were significantly associated with early onset of EA (≤55 vs >55 years, all P < .05 after adjusting for co-variates and false discovery rate). Among them, five SNPs in the NOS3, BCL2, TNFRSF10A, and CASP8 genes were known to be involved in apoptosis processes. In Kaplan-Meier analyses, rs2070744 of NOS3, rs720321 of BCL2, and rs1035142 of CASP8 were also significantly associated with early onset of EA. Moreover, there was a higher risk of developing EA at a younger age when one had more risk genotypes. In conclusion, polymorphisms in cancer-related genes, especially those in the apoptotic pathway, play an important role in the development of younger-aged EA in a dose-response manner.

Part I. Development of a model system for studying nitric oxide in tumors: high nitric oxide-adapted head and neck squamous cell carcinoma cell lines

The free radical nitric oxide (NO) is over-expressed in many tumors, including head and neck squamous cell carcinomas (HNSCC); however, the role NO plays in tumor pathophysiology is still not well understood. We, herein, report the development of an in vitro model system which can be used to probe the role of NO in the carcinogenesis of HNSCC. Five HNSCC cell lines were adapted to a high NO (HNO) environment by gradually introducing increasing concentrations of DETA-NONOate, a nitrogen-based NO donor, to cell media. The adaptation process was carried out until a sufficiently high enough donor concentration was reached which enabled the HNO cells to survive and grow, but which was lethal to the original, unadapted ("parent") cells. The adapted HNO cells exhibited analogous morphology to the parent cells, but grew better than their corresponding parent cells in normal media, on soft agar, and in the presence of hydrogen peroxide, an oxygen-based free radical donor. These results indicate that the HNO cell lines are unique and possess biologically different properties than the parent cell lines from which they originated. The HNO/parent cell lines developed herein may be used as a model system to better understand the role NO plays in HNSCC carcinogenesis.

Part II. Initial molecular and cellular characterization of high nitric oxide-adapted human tongue squamous cell carcinoma cell lines

It is not understood why some head and neck squamous cell carcinomas, despite having identical morphology, demonstrate different tumor aggressiveness, including radioresistance. High levels of the free radical nitric oxide (NO) and increased expression of the NO-producing enzyme nitric oxide synthase (NOS) have been implicated in tumor progression. We previously adapted three human tongue cancer cell lines to high NO (HNO) levels by gradually exposing them to increasing concentrations of an NO donor; the HNO cells grew faster than their corresponding untreated ("parent") cells, despite being morphologically identical. Herein we initially characterize the HNO cells and compare the biological properties of the HNO and parent cells. HNO/parent cell line pairs were analyzed for cell cycle distribution, DNA damage, X-ray and ultraviolet radiation response, and expression of key cellular enzymes, including NOS, p53, glutathione S-transferase-pi (GST-pi), apurinic/apyrimidinic endonuclease-1 (APE1), and checkpoint kinases (Chk1, Chk2). While some of these properties were cell line-specific, the HNO cells typically exhibited properties associated with a more aggressive behavior profile than the parent cells (greater S-phase percentage, radioresistance, and elevated expression of GST-pi/APE1/Chk1/Chk2). To correlate these findings with conditions in primary tumors, we examined the NOS, GST-pi, and APE1 expression in human tongue squamous cell carcinomas. A majority of the clinical samples exhibited elevated expression levels of these enzymes. Together, the results herein suggest cancer cells exposed to HNO levels can develop resistance to free radicals by upregulating protective mechanisms, such as GST-pi and APE1. These upregulated defense mechanisms may contribute to their aggressive expression profile.

Decreased expression of GST pi is correlated with a poor prognosis in human esophageal squamous carcinoma

Background

Glutathione S-transferase pi (GST pi) is a subgroup of GST family, which provides cellular protection against free radical and carcinogenic compounds due to its detoxifying function. Expression patterns of GST pi have been studied in several carcinomas and its down-regulation was implicated to be involved in malignant transformation in patients with Barrett's esophagus. However, neither the exact role of GST pi in the pathogenesis nor its prognostic impact in squamous esophageal carcinoma is fully characterized.

Methods

Immunohistochemistry was used to investigate GST pi expression on 153 archival squamous esophageal carcinoma specimens with a GST pi monoclonal antibody. Statistic analyses were performed to explore its association with clinicopathological factors and clinical outcome.

Results

The GST pi expression was greatly reduced in tissues of esophageal carcinomas compared to adjacent normal tissues and residual benign tissues. Absent of GST pi protein expression in cytoplasm, nuclear and cytoplasm/nucleus was found in 51%, 64.7% and 48% of all the carcinoma cases, respectively. GST pi deficiency in cytoplasm, nucleus and cytoplasm/nucleus was significantly correlated to poor differentiation (p < 0.001, p < 0.001 and p < 0.001, respectively). UICC stage and T stage were found significantly correlated to negative expression of GST pi in cytoplasm (p < 0.001 and p = 0.004, respectively) and cytoplasm/nucleus (p = 0.017 and p = 0.031, respectively). In univariate analysis, absent of GST pi protein expression in cytoplasm, nucleus and cytoplasm/nucleus was significantly associated with a shorter overall survival (p < 0.001, p < 0.001 and p < 0.001, respectively), whereas only GST pi cytoplasmic staining retained an independent prognostic significance (p < 0.001) in multivariate analysis.

Conclusions

Our results show that GST pi expression is down regulated in the squamous esophageal carcinoma, and that the lack of GST pi expression is associated with poor prognosis. Therefore, deficiency of GST pi protein expression may be an important mechanism involved in the carcinogenesis and progression of the squamous esophageal carcinoma, and the underlying mechanisms leading to decreased GST pi expression deserve further investigation.

Long-term adaptation of breast tumor cell lines to high concentrations of nitric oxide

Nitric oxide (NO), a free radical, has been implicated in the biology of human cancers, including breast cancer, yet it is still unclear how NO affects tumor development and propagation. We herein gradually adapted four human breast adenocarcinoma cell lines (BT-20, Hs578T, T-47D, and MCF-7) to increasing concentrations of the NO donor DETA-NONOate up to 600 muM. The resulting model system consisted of a set of fully adapted high nitric oxide ("HNO") cell lines that are biologically different from the "parent" cell lines from which they originated. Although each of the four parent and HNO cell lines had identical morphologic appearance, the HNO cells grew faster than their corresponding parent cells and were resistant to both nitrogen- and oxygen-based free radicals. These cell lines serve as a novel tool to study the role of NO in breast cancer progression and potentially can be used to predict the therapeutic response leading to more efficient therapeutic regimens.

HIF-1α and VEGF are associated with disease progression in esophageal carcinoma

BACKGROUND

Hypoxia inducible factor-1alpha (HIF-1α) is a transcription factor that regulates the transcription of genes associated with cell proliferation and angiogenesis. The purpose of this study is to clarify the correlation of HIF-1α protein expression with vascular endothelial growth factor (VEGF) and inducible (iNOS), endothelial (eNOS), and neuronal nitric oxide synthase (nNOS) expression in esophageal tumors. Additionally, vascular density in tumor tissue was assessed.

MATERIALS AND METHODS

Eighty-eight esophageal carcinomas were analyzed by immunohistochemistry in paraffin embedded sections.

RESULTS

HIF-1α immunoreactivity was seen in 71.2 % of the tumors. Squamous cell carcinomas expressed more often HIF-1α than adenocarcinomas (P = 0.009). HIF-1α immunoreactivity was associated with iNOS (P = 0.049), and iNOS positivity was also more commonly seen in squamous cell carcinomas than adenocarcinomas (P = 0.016). VEGF immunoreaction tended to associate with HIF-1α (P = 0.073) and iNOS (P = 0.08). ENOS did not associate with HIF-1α, but tended to associate with VEGF (P = 0.072). T1-T2 tumors were more often VEGF negative than T3-T4 tumors (P = 0.063). In the subgroup of 78 operatively treated ECs patients with HIF-1α positivity (> +) had more often distant metastases (P = 0.036). There was no association between iNOS, eNOS, nNOS, or VEGF, and microvessel density in tumor tissue, tumor marginal zone, or in peripheral tissue.

CONCLUSIONS

These results show that there is a link in expression between HIF-1α, iNOS, (eNOS), and VEGF in esophageal cancer. This is in line with the fact of HIF-1α's function as a transcriptional factor for these angiogenic factors. Results also show that squamous cell and adenocarcinomas differ in their expression of HIF-1α and iNOS. VEGF appear to have association with depth of invasion in esophageal carcinomas. In our material HIF-1α positivity was associated with distant metastases, but not with patient survival.

Nitrosative stress induces DNA strand breaks but not caspase mediated apoptosis in a lung cancer cell line

Background

Key steps crucial to the process of tumor progression are genomic instability and escape from apoptosis. Nitric oxide and its interrelated reactive intermediates (collectively denoted as NO_X) have been implicated in DNA damage and mutational events leading to cancer development, while also being implicated in the inhibition of apoptosis through S-nitrosation of key apoptotic enzymes. The purpose of this study was to explore the interrelationship between NO_X-mediated DNA strand breaks (DSBs) and apoptosis in cultured tumor cell lines.

Methods

Two well-characterized cell lines were exposed to increasing concentrations of exogenous NO_X via donor compounds. Production of NO_X was quantified by the Greiss reaction and spectrophotometery, and confirmed by nitrotyrosine immunostaining. DSBs were measured by the alkaline single-cell gel electrophoresis assay (the COMET assay), and correlated with cell viability by the MTT assay. Apoptosis was analyzed both by TUNEL staining and Annexin V/propidium iodine FACS. Finally, caspase enzymatic activity was measured using an in-vitro fluorogenic caspase assay.

Results

Increases in DNA strand breaks in our tumor cells, but not in control fibroblasts, correlated with the concentration as well as rate of release of exogenously administered NO_X. This increase in DSBs did not correlate with an increase in cell death or apoptosis in our tumor cell line. Finally, this lack of apoptosis was found to correlate with inhibition of caspase activity upon exposure to thiol- but not NONOate-based NO_X donor compounds.

Conclusions

Genotoxicity appears to be highly interrelated with both the concentration and kinetic delivery of NO_X. Moreover, alterations in cell apoptosis can be seen as a consequence of the explicit mechanisms of NO_X delivery. These findings lend credence to the hypothesis that NO_X may play an important role in tumor progression, and underscores potential pitfalls which should be considered when developing NO_X-based chemotherapeutic agents.

Expression of glutathione s-transferase pi in benign mucosa, Barrett's metaplasia, and adenocarcinoma of the esophagus

BACKGROUND

Glutathione s-transferase pi (GSTpi) is an enzyme that provides cellular protection against redox-mediated damage by free radicals, which have been implicated in carcinogenesis.

METHODS

Forty-three consecutive specimens from 19 patients were reviewed to identify samples of squamous mucosa, Barrett's metaplasia, adenocarcinoma, and peritumoral inflammation. Serial sections were stained with an anti-GSTpi polyclonal antibody, and GSTpi expression was quantified for each histologic group.

RESULTS

GSTpi expression was diminished in peritumoral mononuclear inflammatory cells (p <.001) compared with squamous epithelium, Barrett's metaplasia, or adenocarcinoma. Barrett's metaplasia exhibited decreased GSTpi expression compared with squamous mucosa (p =.045). GSTpi expression by >50% of adenocarcinoma cells was associated with an increased risk (2.25x) of disease at last follow-up.

CONCLUSIONS

GSTpi is prominently expressed in esophageal squamous mucosa and adenocarcinoma. Mononuclear cells may be susceptible to oxidative damage secondary to weak GSTpi production. GSTpi may protect the tumor cells themselves from the cytotoxic effects of free radicals. The biochemical role of GSTpi expression in malignant transformation deserves further investigation.