Glutathione-linked enzymes in benign and malignant oesophageal tissue

Molecular mechanisms associated with chemoresistance in esophageal cancer

Esophageal cancer (EC) is one of the most incident and lethal tumors worldwide. Although surgical resection is an important approach in EC treatment, late diagnosis, metastasis and recurrence after surgery have led to the management of adjuvant and neoadjuvant therapies over the past few decades. In this scenario, 5-fluorouracil (5-FU) and cisplatin (CISP), and more recently paclitaxel (PTX) and carboplatin (CBP), have been traditionally used in EC treatment. However, chemoresistance to these agents along EC therapeutic management represents the main obstacle to successfully treat this malignancy. In this sense, despite the fact that most of chemotherapy drugs were discovered several decades ago, in many cases, including EC, they still represent the most affordable and widely employed treatment approach for these tumors. Therefore, this review summarizes the main mechanisms through which the response to the most widely chemotherapeutic agents used in EC treatment is impaired, such as drug metabolism, apoptosis resistance, cancer stem cells (CSCs), cell cycle, autophagy, energetic metabolism deregulation, tumor microenvironment and epigenetic modifications.

Determining oxidant and antioxidant status in patients with genital warts

OBJECTIVES

Warts are abnormal skin growths caused by human papilloma virus (HPV) infections within the skin of patients. Genital warts usually appear in the perianal and perigenital regions. Asymptomatic warts may be activated after years and may damage natural immunity. The inflammation that occurs during this process may lead to an imbalance between the prooxidant and the antioxidant systems. The aim of this study was to investigate erythrocyte glutathione peroxidase (GSH-Px) activity, serum paraoxonase enzyme levels, and oxidative stress levels in patients with genital warts.

PATIENTS AND METHODS

In total, 32 patients with genital warts and 35 healthy subjects were included in this study. Erythrocyte GSH-Px activity, serum catalase activity, and paraoxonase enzyme, and malondialdehyde (MDA) levels were determined.

RESULTS

Erythrocyte GSH-Px activity, serum MDA levels, and catalase activity were significantly higher in patients with genital warts than in controls (P < 0.01, P < 0.05, and P < 0.05, respectively). However, serum paraoxonase enzyme levels were not significantly different between groups (P > 0.05). Serum triglyceride levels were significantly lower in patients with genital warts than in controls (P < 0.01). However, there were no statistically significant differences between groups with respect to total cholesterol, high-density lipoprotein cholesterol, or low-density lipoprotein cholesterol levels (all P > 0.05).

CONCLUSIONS

Our data suggest that oxidative stress is increased in genital warts. Increased oxidative stress levels may contribute to the pathogenesis of genital warts, and prolonged HPV infection due to chronic inflammation could also affect oxidative stress.

Serum paraoxonase-1 enzyme activities and oxidative stress levels in patients with esophageal squamous cell carcinoma

OBJECTIVES

Oxidative stress is well recognized to play a role in the pathogenesis of many diseases, including cancers. Paraoxonase-1 (PON1) is implicated in the elimination of carcinogenic lipid-soluble radicals produced by lipid peroxidation. Reports on PON1 activities in patients with cancer are conflicting. The aim of this study was to investigate serum antioxidant enzyme activities and oxidative stress levels in patients with esophageal squamous cell carcinoma (ESCC).

PATIENTS AND METHODS

Thirty-two patients with ESCC and 33 healthy controls were enrolled. Serum malondialdehyde (MDA) levels and superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), glutathione reductase (GR), paraoxonase, and arylesterase activities were measured spectrophotometrically.

RESULTS

Serum paraoxonase, arylesterase, SOD, activities, GSH-Px, and GR activities were significantly lower in patients with ESCC than in controls (all, P < 0.05), whereas serum MDA levels were significantly higher (P < 0.05). Serum MDA levels were significantly correlated with paraoxonase (r = -0.572, P < 0.001) and arylesterase activities (r = -0.597, P < 0.001) in patients with ESCC.

CONCLUSIONS

This study indicated that ESCC is associated with increased oxidative stress and decreased antioxidant enzyme activities. Decreased serum PON1 enzyme activities may play a role in the progression and/or development of ESCC. Further studies are required to clarify these results.

Glutathione levels in human tumors

This review summarizes clinical studies in which glutathione was measured in tumor tissue from patients with brain, breast, gastrointestinal, gynecological, head and neck and lung cancer. Glutathione tends to be elevated in breast, ovarian, head and neck, and lung cancer and lower in brain and liver tumors compared to disease-free tissue. Cervical, colorectal, gastric, and esophageal cancers show both higher and lower levels of tumor glutathione. Some studies show an inverse relationship between patient survival and tumor glutathione. Based on this survey, we recommend approaches that may improve the clinical value of glutathione as a biomarker.

Electrophoretic fingerprint metallothionein analysis as a potential prostate cancer biomarker

Prostate-specific antigen (PSA) is a routinely used marker of prostate cancer; however, the cut-off values for unambiguous positive/negative prostate cancer diagnoses are not defined. Therefore, despite the best effort, certain percentage of misdiagnosed cases is being recorded every year. For this reason, search for more specific diagnostic markers is of great interest. In this study, systematic comparison of PSA and metallothionein (MT) levels in blood serum of 46 prostate cancer-diagnosed patients is presented. It is clearly demonstrated that PSA levels vary significantly and despite normal total PSA values in the range of 0 - 4 ng/mL were obtained in over 36.9% of cases, positive prostate cancer was diagnosed by biopsy. In contrary, MT levels were considerably elevated in all tested samples and no significant variations were observed. These results are indicating the potential of MT as an additional prostate cancer marker reducing, in combination with PSA, the probability of false positive/negative diagnosis. To increase the throughput of the screening, chip-based capillary electrophoresis was suggested as a rapid and effective method for the fingerprinting analysis of prostate cancer from diseased blood sera.

Urinary thioether excretion and erythrocyte glutathione S-transferase activities in smokers and patients with squamous-cell laryngeal cancer

Various biomarkers exist for assessment of exposure to cigarette smoke. The aim of this study is to evaluate whether the urinary thioethers (UT) and erythrocyte glutathione S-transferase (GST) enzyme activities can be used as a biomarker or indicator of a higher risk of laryngeal cancer among smokers. In the present study, the concentration of UT and erythrocyte CST activities were measured in a sample of 84 subjects: controls, smokers, and smokers with squamous-cell carcinoma of the larynx (SLC). For this study, cases were restricted to men, since the number of women was not sufficient for statistical comparisons. Smoking significantly increased UT levels without a marked change in GST activity. However, in SLC smoking patients both UT levels and GST activity were significantly elevated. The use of nonspecific UT levels with GST activity determination seems to be a reliable indicator for the presence of laryngeal cancer in smokers.