Effect And Mechanism Of Aspirin On Biological Characteristics Of Colon Cancer Under Hypoxic Condition

PurposeThe aim of clinical study was to evaluate the relationship between long term aspirin use with pretreatment 18 Fluorodeoxyglucose (FDG) uptake of primary lesions of Colorectal cancer (CRC) and evaluate their clinical significance. In vitro study,With colon cancer cell line HCT116 as experimental object, through this in vitro experiment, explore the effect of aspirin under hypoxia condition on cell proliferation, cell cycle and apoptosis rate, migration and invasion of biological behavior, and further explore the effect aspirin on Glut-1 and ALDH-1 expression and its possible mechanism.Materials and MethodsWe enrolled 84 patients with CRC who underwent 18F-FDG PET/CT scanning before surgery between 1st July 2008 and 1st March 2013 and followed up until 1st March 2014. Maximum standardized uptake value (SUVmax) of the primary tumor was measured by 18F-FDG PET/CT. The history of aspirin taken and other clinicopathogical factors were also obtained and their relationships were examined by Mann-Whitney or χ2 tests. Progression-free survival (PFS) was determined by standard Kaplan-Meier survival analysis. Cox proportional hazards regression was performed to determine whether history of aspirin taken, pretreatment SUVmax, age, gender, TNM stage, tumor sizes and differentiation influenced outcomes. In vitro study of aspirin on biological characteristics of colon cancer under hypoxic condition, HCT116 cells was applied. Hypoxia culture model was established. CCK8 assay was used to detect effect s of aspirin on cell proliferation. Flow cytometry was applied to observe cell apoptosis and cell cycle. Transwell method was used to detect cell migration and invasion. ALDH1 expression was detected by flow cytometry. Western Blot and real-time fluorescent quantitative PCR technique were used to detect HIF-1-. Glut-1 and COX-2 expression.ResultsCRC Patients with long term history of aspirin use had lower SUVmax of primary lesions than control group (9.74±2.62 vs.13.91±6.18) and showed a trend towards improved PFS after curative surgery. However, pretreatment of SUVmax showed no prognostic value in patients with CRC. Under hypoxia condition, biology behaviors of HCT116 were explored. The result of CCK 8 indicated that HCT116 cluttered under hypoxia condition did not grow slower than cells cultured in normoxic condition. While aspirin given under hypoxia condition can obviously inhibit the growth of cells. The cell early apoptosis rate was 6.44+0.42% of normoxic group, 1.65 ±0.67% of hypoxia group and 2.65±0.45% of aspirin group respectively. Hypoxia induced an increase in the percentage of G0/G1 phase in HCT116 cells at the G0/G1 phase when compared with normoxic group (45.92±0.67%vs.35.29±0.42% vs.39.81±0.45%.). while aspirin can decrease the percentage of G0/G1 phase in HCT116 (39.81±0.45%). Expression of stem cell markers ALDH-1 were detected by flow cytometry in each group. The result suggested that aspirin can decrease ALDH-1 expression under hypoxia condition which can increase ALDH-1 expression. Transwell assay was used to evaluate the invasive abilities under normoxic and hypoxic conditions. Compared with normoxic group and aspirin group, the number of cells that passed through membranes increased. We also use Western Blot and real-time fluorescent quantitative PCR detection of aspirin for the influence of the Glut-1 expression induced by hypoxia, the results showed that aspirin can decrease expression of Glut-1 and COX-2 under hypoxic condition. While with the extension of hypoxia time, it upregulated the expression of COX-2.ConclusionsLong term aspirin use is associated with lower pretreatment SUVmax of CRC and is a promising prognostic factor for predicting PFS of CRC. Hypoxia can induce the arrest cell cycle in G0/G1 phase; reduce the early apoptosis of tumor cells, increased migration and invasion ability of colon cancer. ALDH-1, Glut-1 and COX-2 expression were also upregulated by hypoxia. Aspirin can be partially reversed the HCT116 biological behavior changes induced by hypoxia, its targets may be associated with COX-2.