Abstract
BackgroundAfrican Americans (AA) are at high risk for Colorectal Cancer (CRC). Studies report a 30–60% increase in CRC risk with physical inactivity, obesity and metabolic syndrome. Activation of the WNT/β-catenin (CTNNB1) signaling pathway plays a critical role in colorectal carcinogenesis. Accumulating evidence also indicates a role of WNT-CTNNB1 signaling in obesity and metabolic diseases.AimTo examine the association between obesity, β-Catenin expression and colonic lesions in African Americans.MethodsWe reviewed the pathology records of 152 colorectal specimens from 2010 to 2012 (46 CRCs, 74 advanced adenomas and 32 normal colon tissues). Tissue Microarrays (TMA) were constructed from these samples. Immunohistochemistry (IHC) for CTNNB1 (β-Catenin; clone β-Catenin-1) was performed on the constructed TMAs. The IHC results were evaluated by 2 pathologists and the nuclear intensity staining was scored from 0 to 4. BMI, sex, age, location of the lesion and other demographic data were obtained.ResultsPositive nuclear staining in normal, advanced adenoma and CRC was 0, 24 and 41%, respectively (P < 0.001). CRC was asso ciated with positive status for nuclear CTNNB1 intensity (adjusted OR: 3.40, 95%CI = 1.42–8.15, P = 0.006 for positive nuclear staining) compared to non-CRC samples (Normal or advanced adenoma). Nuclear staining percentage has a fair diagnostic ability for CRC with an AUC of 0.63 (95%CI = 0.55–0.71).Overweight/obese patients (BMI > 25) did not show a significant difference in (p = 0.3) nuclear CTNNB1 staining (17% positive in normal weight vs. 27% positive in overweight/obese). The association between nuclear intensity and CRC was not different between normal and overweight patients (P for interaction = 0.6). The positive nuclear CTNNB1status in CRC stage III and IV (35% of all CRC) was not different from stage I and II (50% vs. 36%, respectively, P = 0.4).ConclusionIn our study, advanced adenoma and CRC were associated with activation of β-catenin in physically fit, overweight and obese patients. Thus, obesity and WNT/β-Catenin pathway seem to be independent in African American patients. WNT/β-Catenin signaling pathway has a potential to be used as an effector in colon carcinogenic transformation. Whether or not BMI is a modifier of this pathway needs to be investigated further.
Highlights
African Americans (AA) are at high risk for Colorectal Cancer (CRC)
CRC was asso ciated with positive status for nuclear CTNNB1 intensity compared to non-CRC samples (Normal or advanced adenoma)
In our study, advanced adenoma and CRC were associated with activation of β-catenin in physically fit, overweight and obese patients
Summary
Studies report a 30–60% increase in CRC risk with physical inactivity, obesity and metabolic syndrome. Accumulating evidence indicates a role of WNT-CTNNB1 signaling in obesity and metabolic diseases. Lifestyle and epidemiological factors associated with an increased risk of CRC include physical inactivity, obesity and metabolic syndrome [2]. In the United States, approximately twothirds of the adult population are overweight or obese, which represents a putative risk factor for multiple target organ malignancies, including CRC [3]. There is evidence to suggest that excess adiposity is associated with up to 60% greater risk of CRC compared with normal weight individuals [4], and that physical activity may decrease colorectal cancer risk [5]. The underlying mechanisms that might explain the association and the magnitude of the connection between excess body weight and CRC remain unclear
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