Indian Journal of Biochemistry & Biophysics Vol. 47, April 2010, pp 121-123 Indicators of oxidative stress in thyroid cancer Bhargav Koduru a* , Tejaswini a , Ajit Thakur a , Shobha U Kamath a , Kallya Rajgopal Shenoy b , Ullas Kamath c and K Reshma d a Department of Biochemistry, b Department of Surgery, Kasturba Medical College, Manipal University, Manipal 576104, India c Department of Biochemistry, Melaka Manipal Medical College (Manipal Campus), Manipal 576104, India d Department of Biochemistry, Kasturba Medical College, Manipal University, Mangalore 575002, India Received 16 November 2009; revised 16 February 2010 Ferric reducing antioxidant power (FRAP), myeloperoxidase (MPO) activity and the levels of protein thiols and carbonyls were estimated in the blood samples of thyroid cancer patients (n = 20) before and after thyroidectomy, as well as in healthy controls (n = 10) to study the extent of damage caused by tumor tissue proliferation-induced oxidative stress and to ascertain that oxidative stress levels drop, when there was no proliferation. A significant decrease (p<0.001) in the levels of serum protein thiols and FRAP as well as a significant increase (p<0.001) in the levels of protein carbonyls and MPO activity in the blood of thyroid cancer patients before surgery was observed as compared to healthy controls. All the parameters studied also showed a significant difference (p<0.001) in their respective levels in thyroid cancer patients, pre- and post-thyroidectomy. These findings present the role of oxidative stress as a pathological implication of thyroid cancer. Keywords: Thyroid cancer, Carbonyl, Thiols, Myeloperoxidase, FRAP, Free radical, Oxidative damage. The higher eukaryotic aerobic organisms cannot exist without oxygen, yet oxygen is inherently dangerous to their existence. Reactive oxygen species (ROS) in the form of superoxide anion radical, hydrogen peroxide (H 2 O 2 ) and the extremely reactive hydroxyl radical are common products in an aerobic environment and appear to be responsible for oxygen toxicity 1-3 . Living organisms have evolved to generate or mobilise from their surroundings a variety of water and lipid-soluble antioxidant compounds. Additionally, a series of antioxidant enzymes are synthesized to intercept and inactivate reactive oxygen intermediates; but, oxidative damage is an inescapable outcome of aerobic life. Imbalance between free radicals and antioxidants in favour of free radicals has been considered to have carcinogenic potential 4 and to promote invasiveness 5 . Oxidative stress is common in the thyroid tissue during utilization of H 2 O 2 for thyroxine synthesis and when a tumour is proliferating actively 6 , but H 2 O 2 through its mutagenic effect has been implicated in carcinogenesis in other tissues 7 . Thus, the hallmark of thyroid physiology-H 2 O 2 production during hormone synthesis is very likely to be the cause of frequent mutagenesis in the thyroid gland 8 . There is evidence implicating oxidant/antioxidant imbalance in thyroid cancer 9,10 and hyperthyroidism 11 . In the present study, the role of oxidative stress in thyroid cancer has been investigated by evaluating protein thiols and carbonyls, myeloperoxidase (MPO) activity and antioxidant power (FRAP) in the blood samples of thyroid cancer patients before and after the thyroidectomy operation, and compared with the levels in healthy controls. Materials and Methods Chemicals 2, 4, 6-Tris-(2-pyridyl)-s-triazine (TPTZ), 5, 5'- dithio-bis-(2-nitrobenzoic acid) (DTNB), 2, 4-dinitro- phenylhydrazine (DNPH) and 4-aminoantipyrine were obtained from Sigma Chemicals Co., St. Louis, MO, USA. All other reagents and chemicals used were of analytical grade. Subjects Twenty subjects diagnosed with thyroid cancer and consequently scheduled to undergo thyroidectomy in the Department of Surgery, Kasturba Medical College, Manipal, India were selected for the study. Ten healthy subjects, age- and sex-matched were taken as controls and informed consent was obtained from all the subjects involved in the study. Blood samples were drawn under aseptic conditions into 2 ml plain and 4 ml K 2 EDTA vacutainers from the antecubital vein of each subject, before and on the 20 th day after surgery and processed for serum and plasma, respectively. ________________ *Corresponding author Tel: 91-9964015811 E-mail: bhargavkoduru@gmail.com Abbreviations: DNPH, 2, 4-dinitrophenylhydrazine; DTNB, 5,5'- dithio-bis-(2-nitrobenzoic acid); FRAP, ferric reducing antioxidant power; H 2 O 2, hydrogen peroxide; MPO, myeloperoxidase; ROS, reactive oxygen species; TPTZ, 2, 4, 6 –tris (2-pyridyl)-s-triazine