|Year : 2019 | Volume
| Issue : 1 | Page : 41-44
Oxidative stress in relation to obesity in breast cancer
R Sateesh1, Aparna Rajeshwar Rao Bitla1, Sandya Rani Budugu1, Y Mutheeswariah2, H Narendra3, BV Phaneedra4, AY Lakshmi5
1 Department of Biochemistry, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
2 Department of Surgery, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
3 Department of Surgical Oncology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
4 Department of Pathology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
5 Department of Radiology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
|Date of Web Publication||4-Apr-2019|
Aparna Rajeshwar Rao Bitla
Department of Biochemistry, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
PURPOSE: Breast carcinoma is one of the most common neoplasms in women and is a leading cause of cancer-related deaths worldwide. Obesity-induced chronic inflammation promoted by adipose tissue dysfunction is a key feature, which is thought to be an important link between obesity and cancer. Oxidative stress (OS) has been suggested to play an important role in carcinogenesis. Obese women have been shown to have higher levels of OS markers. The study was performed to know the influence of obesity on OS to be replaced with OS markers in patients with breast cancer.
MATERIALS AND METHODS: Thirty women attending the outpatient Department of Surgical Oncology and Surgery at Sri Venkateswara Institute of Medical Science, Tirupati, who were clinically diagnosed and histologically confirmed with breast cancer were considered as the patients and 30 healthy women were included as controls. Malondialdehyde (MDA), protein carbonyls (PCC), and advanced oxidation protein products (AOPP) as oxidative markers along with protein thiols and ferric-reducing ability of plasma (FRAP) were studied as markers of antioxidant status.
RESULTS: Patients with breast cancer had significantly higher levels of MDA (P = 0.005), PCC, and AOPP compared to controls (P = 0.001) and significantly lower levels of thiols and FRAP compared to controls (P = 0.001). No significant correlation was found between OS markers and indices of obesity. A significant association was found between OS markers (P = 0.005), PCC (P = 0.002), AOPP (P = 0.002), and breast cancer.
CONCLUSIONS: Patients with breast cancer have increased OS as evidenced by an increase in oxidant markers and a decrease in antioxidant markers. OS is not related to their adiposity but is related to the presence of breast cancer.
Keywords: Advanced oxidation protein products, breast cancer, malondialdehyde, obesity, oxidative stress
|How to cite this article:|
Sateesh R, Rao Bitla AR, Budugu SR, Mutheeswariah Y, Narendra H, Phaneedra B V, Lakshmi A Y. Oxidative stress in relation to obesity in breast cancer. Indian J Cancer 2019;56:41-4
|How to cite this URL:|
Sateesh R, Rao Bitla AR, Budugu SR, Mutheeswariah Y, Narendra H, Phaneedra B V, Lakshmi A Y. Oxidative stress in relation to obesity in breast cancer. Indian J Cancer [serial online] 2019 [cited 2019 Jun 18];56:41-4. Available from: http://www.indianjcancer.com/text.asp?2019/56/1/41/255476
| » Introduction|| |
Breast carcinoma is one of the most common neoplasms in women and is a leading cause of cancer-related deaths worldwide including India. The strongest risk factors are sex, age, obesity, age at menarche and menopause, use of hormone replacement therapy, use of oral contraceptive pills, and alcohol consumption. Excess body weight has been linked to an increased risk of postmenopausal breast cancer and evidence also suggest that obesity is associated with poor prognosis in women diagnosed with early-stage breast cancer. Weight gain and obesity are among the most important factors that predict risk for estrogen-dependent breast cancer (EDBC) in postmenopausal women.
Levels of circulating estrogens derived from peripheral aromatization of androgens are higher in overweight women. Adiposity results in higher circulating levels of insulin and insulin-like growth factor (IGF), which stimulate the growth of epithelial breast cells and induce neoplastic transformation. Obesity is associated with lower levels of sex-hormone binding globulin, which correlates with increased bioavailability of circulating estrogens. Obesity-induced chronic inflammation promoted by adipose tissue dysfunction is a key feature, which is thought to be an important link between obesity and cancer. Chronic inflammation induces an increase in free radical generation and subsequently promotes oxidative stress, thus creating a microenvironment favorable to the tumor development in obese individuals.
Oxidative stress has been suggested to play an important role in carcinogenesis. Oxidative stress damages lipids, proteins, and nucleic acids and induces activation of Akt/PI3K/mTOR signaling, promoting oncogenesis, and tumor progression, in EDBC. Reactive oxygen species (ROS) are involved in estrogen-genotoxic effects, which lead to breast cancer initiation and/or progression. Experimental evidence reveals that ROS are involved in initiation, promotion, and progression of carcinogenesis, where inactivation or loss of certain tumor-suppressor genes has occurred, including breast cancer. The magnitude of damage induced by ROS depends upon the balance between the amount of ROS produced and the body's defense capacity to counteract this oxidative damage.
Various independent studies have observed elevated levels of oxidant markers, and lower levels of antioxidants compared to breast cancer. Obese women have been shown to have higher levels of oxidative stress markers. Studies have shown that the association of several risk factors with breast cancer differed by body mass index (BMI) levels. There are scarce data, with regard to the influence of obesity on OS markers in patients with breast cancer. With this background, the present study was aimed to study malondialdehyde (MDA), protein carbonyls (PCC), and advanced oxidation protein products (AOPP) as oxidative markers along with protein thiols and ferric-reducing ability of plasma (FRAP) as markers of antioxidant status in breast cancer patients and to study the association of these markers with indices of obesity namely BMI, waist circumference (WC), hip circumference (HC), and waist–hip ratio (WHR).
| » Materials and Methods|| |
The present study included 30 newly diagnosed patients who were histologically and/or cytologically confirmed with diagnosis of primary breast tumors. Women attending the outpatient Department of Surgical Oncology and Department of Surgery at Sri Venkateswara Institute of Medical Sciences, Tirupati, were included after obtaining institutional ethics committee clearance and written informed consent. Thirty age-matched apparently healthy women from along the patient relatives and hospital staff were included as controls. Pregnant women, patients having past or present history of any other gynecological or other malignancies, those undergoing treatment for breast tumors, receiving oral contraceptive pills, hormone replacement therapy, steroid medications, and those not willing to participate were excluded from the present study.
Clinical characteristics including estrogen and progesterone receptor status and stage of the disease were collected from the case records of the patients. The demographic details of the subjects including height, weight, WC, and HC were noted and used to calculate BMI (kg/m2) and WHR.
Blood samples were collected from the cases before the start of treatment. A volume of 5 mL peripheral venous blood sample was collected from all the study subjects after overnight fasting and then transferred into a tube containing anticoagulant (heparin). Plasma was immediately separated by centrifugation at 2000 rpm for 10 min. The separated plasma was transferred into aliquots and stored at −50°C until further analysis.
Estimation of biochemical parameters
MDA was determined by thiobarbituric acid-reactive substances method; PCC, AOPP, thiols, and FRAP were determined by spectrophotometric methods on Lambda 25 UV/Vis Spectrophotometer (Perkin Elmer, Singapore).
Data obtained was expressed as mean ± standard deviation. Difference in all biochemical parameters studied among study groups was tested using independent samples t-test. Pearson's correlation analysis was performed to test the correlation between markers. Logistic regression analysis was performed to test the association between markers. Data analysis was performed using Microsoft Excel spreadsheets and SPSS for windows version 11.5 program. A P value of <0.05 was considered as statistically significant.
| » Results|| |
Demographic characteristics of the study population are shown in [Table 1]. Both the groups were matching in terms of age (P = 0.069) and BMI (P = 0.820). Breast cancer patients had significantly higher WC (P = 0.001), HC (P = 0.041), and WHR (P = 0.001) compared to the control group. [Table 2] shows the comparison of oxidative stress markers in the study group and control group. Patients with breast cancer had significantly higher levels of all the oxidant markers studied, that is, MDA (P = 0.001), AOPP (P = 0.001), and PCC (P = 0.001) compared to the control group. On the other hand, patients with breast cancer had significantly lower levels of the antioxidant markers studied, that is, protein thiols (P = 0.001) and FRAP (P = 0.001) compared to the control group. As shown in [Table 3], no significant correlations were observed between oxidative stress markers and indices of obesity. Logistic regression analysis however showed that oxidative stress markers, MDA [OR = 757.66, 95% confidence intervals (CI) (7.217–7954.0), P = 0.005], PCC [OR = 13.37, 95% CI (2.264–68.155), P = 0.002], and AOPP [OR = 1.08, 95% CI (1.133–1.30), P = 0.002] to be significantly associated with breast cancer.
|Table 2: Oxidant and antioxidant parameters among the study group and control group|
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|Table 3: Correlation analysis between oxidative stress markers and indices of obesity in the study group|
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| » Discussion|| |
In the present study, patients with breast cancer had significantly higher levels of plasma MDA compared to controls (P = 0.001). This is in agreement with previous studies which have shown increased plasma MDA levels in breast cancer patients compared to controls., The levels have been shown to be higher in advanced stages, that is, stage III to stage IV. In contrast to this, one study reported lower MDA levels in breast cancer patients compared to controls and higher levels both in tissue and serum of benign breast disease patients compared to breast cancer patients. The authors proposed it to be due to a better antioxidant status in breast cancer patients compared to the benign cases.
Posttranslational modifications (PTMs) of proteins, both enzymatic (phosphorylation, methylation, acetylation, glycosylation) as well as nonenzymatic (oxidation, advanced glycation end products) can significantly alter the function of a protein and the differences in gene expression between breast cancer patients and controls may be a result of these PTMs. Protein carbonyls, a marker of oxidative damage, were found to be significantly higher in breast cancer patients compared to controls (P = 0.001). This is in agreement with previous reports which have showed increased levels of MDA and PCC, in patients with breast cancer. The study conducted in New York (Breast Cancer Family Registry) found plasma PCC to be associated with an increase in breast cancer risk, though not in a dose-dependent manner.
AOPP, another protein oxidation product, was found to be significantly higher in breast cancer patients compared to controls in the present study (P = 0.001). This is in agreement with a previous report. The levels have been shown to be higher in advanced stages, that is, stage III to stage IV, decreased serum concentrations of AOPP levels in breast cancer patients with the highest expression of C erb/Her neu compared to controls in their study.
Cellular nonenzymatic antioxidants such as glutathione, total thiols, melatonin, and vitamins (A, C, and E) known as free radicals scavengers protect cells against toxic-free radicals. Among the antioxidant markers studied, plasma levels of protein thiols and FRAP levels were found to be significantly lower in breast cancer patients compared to controls (P = 0.000). This is in agreement with previous studies., Among all the antioxidants, thiols constitute the major portion of the total body antioxidants and they play a major role in defense against ROS. Redox states of thiols play a critical role in the determination of protein structure and function, regulation of enzymatic activity of transcription factors, and antioxidant protection. FRAP assay requires a short time. FRAP values have been shown to be proportional to the reducing power of the main nonenzymatic antioxidants in the plasma. Thus, the FRAP assay was chosen to determine the total antioxidant capacity of plasma of patients with breast cancer patient and control groups.
Obesity has been implicated in causing breast cancer through three hormonal systems, that is, insulin and IGFs, especially IGF-binding protein-1 factor (IGF-1), sex hormones, and adipokines. In addition, in obese postmenopausal women, the release of proinflammatory cytokines, like interleukin-1, interleukin-6, and tumor necrosis factor-α (TNF-α), is increased and can be responsible for inflammation by stimulation of macrophages. Interleukins and the TNF-α factor can affect the growth and differentiation of lymphocytes, stimulation of immune cell proliferation, and differentiation. Thus, obesity may lead to ROS generation followed by a decrease of antioxidant potential of the tissue. Further, this process can lead to oxidative stress and alteration of immune response.
Chronic inflammation induces an increase in free radicals generation and subsequently promotes oxidative stress, which may create a microenvironment favorable to the tumor development in obese person. Also, obese women have been shown to have higher levels of oxidative stress markers. In the present study, measures of obesity mainly WC, HC, and WHR were significantly higher than controls. However, no association was found between oxidative stress markers and indices of obesity in patients with breast cancer [Table 3]. A study done in Shanghai found the levels of oxidant marker 15-F2t-isoprostane (15-F2t-IsoP) to be inversely associated with breast cancer risk in a dose–response manner among women with a BMI less than 23 kg/m2. Conversely, 15-F2t-IsoP and 2,3-dinor-5,6-dihydro-15-F2t-IsoP (15-F2t-IsoPM) which is a metabolite of 15-F2t-IsoP were positively associated with breast cancer risk among women with a BMI ≥25 kg/m2.
However, a significant association was found between oxidative stress markers and breast cancer. An elevation in MDA was associated with the highest odds of developing cancer (OR = 757.66). This is in agreement with previous studies which have shown a link between breast cancer and oxidative stress. The very high odds ratio observed can be unrealistic. However, other studies have also reported very high odds ratio in studies related to cancer wherein the differences observed between cases and controls is wide and thus giving statistically wide odds ratios. A recent meta-analysis tabulated the odds ratio calculated from the data for TFPI2 hypermethylation frequency and colorectal cancer risk in different studies. This study reported an odds ratios of 512.85 [95% CI (27.92–9420.72)] and 3435 [95% CI (135.56–87,041.07)] among two studies in colorectal cancer. MDA has been shown to be mutagenic in humans and could thus be involved in tumorigenesis.
In the present study, patients with breast cancer had significantly higher levels of oxidative stress markers, that is, MDA, PCC, and AOPP compared to controls. Also, these patients had significantly lower levels of antioxidant markers, that is, thiols and FRAP compared to controls. The findings of the present study suggest an imbalance in the redox homeostasis in patients with breast cancer. Disturbances in redox homeostasis can lead to an imbalance in pro- and antiapoptotic processes, altered gene expression, and mutations all of which are involved in the process of tumorigenesis. However, no significant correlation was found between oxidative stress markers and indices of obesity. Thus, the oxidative stress observed is independent of obesity as evidenced from the lack of association with indices of obesity and is related to the presence of breast cancer.
To conclude, the findings of the present study show that patients with breast cancer have increased oxidative stress as evidenced by an increase in oxidant markers and a decrease in antioxidant markers. This oxidative stress is not related to their adiposity but is related to the presence of breast cancer. This study reiterates the importance of preventing oxidative stress so as to prevent the development/progression of many chronic diseases in which oxidative stress plays an important role.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]