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Journal of Cancer Research and Therapeutics, Vol. 7, No. 2, April-June, 2011, pp. 180-182 Original Article Serum phosphodiesterase levels in oral cancer K Prabhu1, D Naik1, S Ray2, BM Vadiraja3, A Kamath4 1 Department of Biochemistry, Kasturba Medical College, Manipal University, Manipal, India Code Number: cr11041 PMID: 21768707 Abstract Background: Oral squamous cell carcinoma (OSCC) is one of the most common malignancies recognized nowadays. Its early detection is the better alternative to provide a good quality of life for the patients. During the last years, several studies have identified potential biomarkers of OSCC progression and prognosis. The phosphodiesterases (PDEs) are responsible for the hydrolysis of the second messengers with a fundamental role in the transduction of the intracellular signals. Variations in PDE activity have been correlated to different pathological mechanisms, such as cellular differentiation, apoptosis, and tumor invasivity. PDEs are also known to play a role in tumor growth by influencing angiogenesis.
Keywords: Oral cancer, pathophysiology, phosphodiesterase Introduction Cancer affects all communities worldwide and approximately 10 million people are diagnosed with cancer. Cancer is a class of disease in which a group of cells display uncontrolled growth, invasion, and angiogenesis. Tumor angiogenesis or neovascularization is the proliferation of a network of blood vessels that penetrate into cancerous growths, supplying nutrients and oxygen and removing waste products. [1] Oral cancer is the eighth most common cancer worldwide, [2] prevalence being high among men. In India, the age-standardized incidence rate of oral cancer is 12.6 per 1 00 000 population. [3] "Oral" cancer per se includes cancers of the lip, tongue, gingiva, oral mucosa, oropharynx, and hypopharynx. [4] The clinical and histological features alone cannot always accurately predict whether potentially malignant disorders of the oral mucosa remain stable, regress, or progress to malignancy. [5] Identification of molecular markers (or biomarkers) which can predict disease progression is necessary for better management of these disorders. [5] Commonly, nonfunctional plasma enzymes are used as an aid for diagnosis and prognosis, e.g., aminotransferases, amylase, [6] etc. Markers like glutathione S-transferases, N-acetyltransferases, and serum dipeptidyl peptidase have been associated with various epithelial malignancies and have been shown to influence the susceptibility for cancer and outcome of treatment. [7],[8],[9],[10],[11] Alteration in PDE activity has been associated with cellular differentiation, apoptosis, tumor invasion, [Figure - 1]. [12],[13] angiogenesis, etc. [14] Aim To estimate and compare serum phosphodiesterase (PDE) levels in healthy controls and biopsy-proven oral cancer patients before definitive therapy. Materials and Methods The study was carried out after obtaining approval from the Institutional Ethics Committee. In this study, 59 subjects, aged between 25 and 75 years of either sex, were used. Of them, 39 were biopsy-proven oral cancer patients (stage 2, 3, and 4) and 20 were healthy controls. The oral cancer patients were admitted under Radiotherapy and Oncology department between June 2009 and June 2010. Cancer cases with associated serious diseases like liver disease, diabetes, renal disease, and those who were on any long-term medications were excluded. Cases were selected at our convenience. They received radiotherapy as definitive treatment. The control group comprised of age- and gender-matched healthy subjects. Among oral cancer patients, 31 were males and 8 were females. Blood (2 ml) was collected from controls after obtaining consent. The blood samples (2 ml) were also collected with prior consent from cancer patients before radiotherapy. The blood samples were collected in a vacutainer with no anticoagulant. The sample was allowed to clot for 30 minutes. After centrifugation at 3 000 rpm for five minute, the clear supernatant serum was used for the determination of PDE levels. PDE levels of samples were measured by using Genesis 10 UV (Thermo Electron Corporation). For maintaining the reaction temperature at 37°C, automated water bath obtained from Rotek was used. Cyber scan 510 pH meter (Elico Ltd) was used. Sartorius balance was used for weighing chemicals. PDE assay Principle Paranitrophenyl phosphate (4-nitrophenyl phosphate) is hydrolyzed by PDE to 4-nitrophenol (4-hydroxynitrobenzene) and inorganic phosphate. The yellow color formed due to liberation of 4-nitrophenolate at pH 9 was measured spectrophotometrically at 400 nm. [15] Procedure In a clean dry test tube, 1 ml of assay mixture containing 500 μl of Tris HCl, 100 μl of MgCl 2, 100 μl of paranitrophenyl phosphate, and 300 μl of distilled water was taken. The mixture was incubated at 37°C for 5 minutes. Then, to this mixture, 10 μl of serum (10 μl of double distilled water in case of blank) was added. The mixture was again incubated at 37°C for 10 minutes. 2 ml of NaOH with EDTA was added to each test tube to stop the reaction. Activity was calculated using molar absorption coefficient of the product of chemical reaction, 4-nitrophenol (17, 600). [15] Results The patients (n = 39) of oral cancer presented with either stage 2 or 3 or 4 of cancer. In the group comprising of oral cancer patients, pretreatment PDE levels were significantly elevated (P≤0.0001) as compared with the controls [Table - 1]. Pretreatment serum PDE levels showed an increase with advancing stages of oral cancer [Table - 2]. On stage-wise comparison of pretreatment serum PDE levels using Kruskal Wallis test, a significant (P<0.001) difference was observed. So, a pair-wise comparison between stages was made--there was a significant (P<0.001) difference in PDE levels of stage 4 as compared with that of stage 2 and stage 3 [Table - 2]. Discussion Oral squamous cell carcinoma (OSCC) is one of the most common malignancies recognized nowadays, and represents a public health problem. Its early detection helps to provide a good quality of life for the patients. During the past years, several studies have identified potential biomarkers of OSCC progression and prognosis. [16] cAMP is an important "second messenger" transferring information into cells and exists ubiquitously in the tissues and cells of mammals. The cAMP signal pathway is involved in many metabolic pathways in cells, and regulates many physiological processes, such as cell metabolism, proliferation, and cell death. The PDEs are responsible for the hydrolysis of the second messengers, with a fundamental role in the transduction of the intracellular signals. Variations in PDE activity have been found in different pathologies, and they have also been correlated to different pathophysiological mechanisms, such as cellular differentiation, apoptosis, and tumor invasivity. [13],[17] PDEs are also known to play a role in tumor growth by influencing angiogenesis. [18],[19] Inhibition of selective PDE isoforms, which raises the levels of intracellular cAMP and cGMP, has been shown to induce apoptosis and cell cycle arrest in a broad spectrum of tumor cells. [20],[21],[22] Our results showed a significant increase in pretreatment PDE levels in cancer patients as compared with controls. In our study, pretreatment serum PDE levels correlated well with advancing stage of cancer and also showed higher levels in cancer patients than controls. This implies that they might have been induced and released from cancer cells. This may imply a possible role for inhibitors of specific PDE isoenzymes which may selectively restore normal intracellular signaling, providing antitumor therapy with reduced adverse effects. [19] A limitation of the present study is lesser number of controls as compared with cases. The disparity in the number was due to lack of healthy volunteers consenting for the study. References
Copyright 2011 - Journal of Cancer Research and Therapeutics The following images related to this document are available:Photo images[cr11041f1.jpg] [cr11041t2.jpg] [cr11041t1.jpg] |
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