257 Role of Epidermal Growth Factor Receptor (EGFR) in Inflammation Induced Colorectal Cancers

cells (HBMPC) to the lung and formation of pre-metastatic niches. These niches would be suitable environments for seeding of CTC and for the development of metastasis. Thus, we hypothesized that the patients with greater risk of developing metastasis are those not only with CTC but also with circulating HBMPC. Before evaluating the presence of these populations in cancer patients, we sought to evaluate the detection viability of these rare populations in peripheral blood (PB). Therefore, the goal of this study was to determine the lower limit of detection of these rare cells populations in PB by flow cytometry. Material and Methods: We tested the detection of rare populations in PB using a model composed by PB of healthy donors and the cell lines MCF-7 and HL-60, representing CTC and HBMPC, respectively. Each cell line was fluorescently labeled and mixed with whole PB in to achieve concentrations from 5% to 0.01% per 10 leukocytes. After lysis of red blood cells, the mixture was analyzed by flow cytometry, and at least 100,000 events per tube were acquired. Results: Rare events such as 0.01% and 0.05% were successfully detected in our model. Using linear regression, we found that the determination coefficient between the expected number of target cells and the number of detected cells was R = 0.99 to CTC and R = 0.98 to HBMPC. Conclusion: Detection of rare populations of cells in PB is feasible and may allow the investigation of CTC and HBMPC in cancer patients. The association of CTC and HBMPC and cancer progression would suggest that cancer is a systemic disease, even if it is not considered disseminated according to current understanding, once it interacts with the whole organism. This concept would provide the establishment of new approaches for the prevention of metastasis.