‘Oxidation stress index’ as a possible clinical marker for the evaluation of non‐Hodgkin lymphoma

Oxidative stress caused by the increased production of reactive oxygen species and/or decreased efficacy of the antioxidant system is implicated in the pathogenesis of various disease entities, such as arteriosclerosis, malignant tumours, and autoimmune diseases (Kamezaki et al, 2008; Katsabeki-Katsafli et al, 2008; Sakane et al, 2008; Kotani et al, 2010). An excellent review on possible implication of oxidative stress in the pathogenesis of malignant disorders has recently been published (Barry, 2007). Prompted by the perspective, we became interested in examining the level of oxidative stress in serum in relation to the clinical stages and grades of non-Hodgkin lymphoma (NHL) in our case series accumulated over the past 15 years. We measured both oxidation and anti-oxidation activities simultaneously in sera from 62 NHL patients [30 females, 32 males with a mean age (range) of 58·2 (20–78) years] and 312 healthy volunteers [164 females, 148 males; mean age (range), 36·7 (20–59) years]. Oxidation activity was assessed by the Reactive Oxygen Metabolites-derived compounds (d-ROMs) test (Diacron International, Grosseto, Italy) and anti-oxidation activity was measured with the Biological Antioxidant Potential (BAP) test (Diacron International) using a JCA-BM1650 automated analyser (JEOL, Tokyo, Japan). In the d-ROMs test (Cesarone et al, 1999; Trotti et al, 2002), ROMs (primarily hydroperoxides) of a serum sample, are able to generate alkoxyl and peroxyl radicals in the presence of iron released from serum proteins by an acidic buffer, according to the Fenton reaction. In turn, these radicals oxidize an alkyl-substituted aromatic amine (N,N-diethylparaphenylendiamine), thus producing a pink-coloured derivative, which is photometrically quantified at 505 nm. The ROMs concentration is directly parallel with colour intensity and is expressed in Carratelli Units (1 CARR U = 0·08 mg hydrogen peroxide/dl) (Trotti et al, 2002). In the BAP test (Kakita et al, 2006), the addition of a serum sample to a coloured solution, obtained by mixing a ferric chloride solution with a thiocyanate derivative solution, causes a decolouration, the intensity of which is measured photometrically at 505 nm and is proportional to the antioxidant capacity of a serum sample. The normal reference interval of the d-ROMs and BAP tests, which were determined as the mean ± 2 standard deviations (SD) of values obtained from the 312 healthy volunteers, were 286·9 ± 100·2 CARR U and 2541 ± 122 μmol/l, respectively. To obtain a parameter representing an overall shift toward the oxidative stress, the oxidation stress index (OSI) was devised by the following formula: OSI = C × (d-ROMs/BMP), where C denotes a coefficient for standardization to set the mean of OSI in healthy individuals at 1·0 (C = 8·85 in this study). The present study confirmed that the levels of OSI in the 312 healthy volunteers were significantly higher in sera from the female volunteers (mean ± SD, 1·02 ± 0·17, P < 0·005) than in sera from the male volunteers (0·97 ± 0·17) and that the OSI levels increased significantly with a rise in age (P < 0·001; Fig 1). Comparison of oxidation stress index (OSI) in 312 healthy volunteers according to age group (in years). @1The OSI levels in 312 healthy volunteers increased significantly with the increase in age (Kruskal–Wallis test). *P < 0·001. Moreover, the OSI level was significantly higher in sera of the NHL patients (1·78 ± 0·87, P < 0·0001) than in those of the healthy volunteers (1·00 ± 0·17). When the 62 NHL patients were divided into four diagnostic categories, mucosa-associated lymphoid tissue lymphoma (MALT, n = 7), follicular lymphoma (FL, n = 9), diffuse large B-cell lymphoma (DLBCL, n = 38), and mantle cell lymphoma (MCL, n = 8) (Sabattini et al, 2010), the OSI levels were significantly higher in the patients with DLBCL (1·70 ± 0·57, n = 38) and MCL (3·31 ± 0·99, n = 8), which are regarded as aggressive forms of lymphoma, than in those with MALT (1·17 ± 0·42, n = 7) and FL (1·18 ± 0·47, n = 9), which are considered to be indolent (P < 0·001; Fig 2). Furthermore, when the 38 DLBCL patients were subclassified into clinical stage II (involvement of two or more lymph node groups on one side of the diaphragm), III (involvement of lymph node groups on both sides of the diaphragm), and IV (involvement of non-lymph node organs such as the liver or bone marrow) (Sabattini et al, 2010), the OSI levels were significantly higher in DLBCL patients with stage III or IV disease than in those with stage II disease (P < 0·001; Fig 2). These results suggest that the OSI might be a useful clinical marker for the evaluation of malignant grades and clinical stages of NHL. However, further study is required to examine an aetiological mechanism leading to the alteration in oxidative stress. Comparison of oxidation stress index (OSI) between the diagnostic categories of non-Hodgkin lymphoma. @1The OSI levels were significantly higher in patients with DLBCL and MCL, which are regarded as aggressive forms of lymphoma, than in those with MALT and FL, which are considered to be indolent (Mann–Whitney test). @2The OSI levels were significantly higher in DLBCL patients with stage III or IV disease than in those with stage II disease (Kruskal–Wallis test). *P < 0·001. DLBCL: diffuse large B-cell lymphoma; FL: follicular lymphoma; MALT: mucosa-associated lymphoid tissue lymphoma; MCL: mantle cell lymphoma. The authors declare that they have no conflicts of interest.