Circulating Mesenchymal Stromal Cells As a New Prospective Cancer Marker,

Abstract 3404

Mobilization of progenitor cells is implicated in pathology and can be indicative of disease progression. Recently, we reported the influence of body mass index (BMI) on level of circulating progenitor cells (Bellows et al., Obesity 2011). Comparative analysis of peripheral blood mononuclear cells (PBMC) from 12 non-obese (BMI < 30) and 14 obese (BMI > 30) disease-free donors by flow cytometry revealed that obesity is associated with a 10-fold increased frequency of circulating mesenchymal stromal progenitor cells (MSC), which circulate at a very low level in healthy lean individuals. We showed that obesity is also associated with a 5-fold increased frequency of circulating progenitor cells (CPC), a population consisting of hematopoietic and endothelial precursors, while the frequencies of mature endothelial cells (EC) and CD34-bright leukocytes (CD34b LC) are unaffected by BMI. Here, we followed up on the assessment of circulating MSC as a potential surrogate pathology marker by analyzing the frequency of circulating CD34-positive progenitor and endothelial cells in a cohort of colorectal cancer patients. PBMC were collected from 45 obese and lean cancer patients and compared to control cancer-free donors. Flow cytometric enumeration of cells was performed based on established immunophenotypes: CD34brightCD31dimCD45dim (CPC), CD34dimCD31brightCD45- (EC), CD34brightCD31-CD45- (MSC) and CD34brightCD45bright CD34b (LC). Groups were compared using multivariate regression analysis. After adjusting for co-founders such as age and BMI, the mean frequencies of MSC and CD34bLC, but not of CPC and EC, were found to be significantly higher in the circulation of CRC patients compared to cancer-free donors. Interestingly, the frequency of circulating MSC, but not of the other cell populations, was also found to be significantly higher in the circulation of obese CRC patients compared to lean CRC patients and obese cancer-free controls. We conclude that markedly increased frequency of MSC in the peripheral blood may represent a new diagnostic CRC marker. BMI-dependent changes in circulating MSC, potentially mobilized from adipose tissue may reveal their trafficking to tumors, which could be one of the mechanistic links between obesity and cancer progression. Validation of MSC as a new surrogate marker of cancer could provide a tool for determining prognosis, predicting response to therapy, and detecting relapse following treatment.