As one of the crucial steps in metastatic progression requires tumor to successfully interact with its local microenvironment, it follows that targeting this cross-talk may be an attractive adjuvant to standard treatment approaches. We are currently focused on developing therapies that target the associated tumor recruited host stromal cells. We now have an IRB approved biological repository study to obtain blood, bone marrow and tumor and adjacent normal tissue when available from patients with malignancy and healthy donors. We continue our on-going studies of measuring and characterizing the circulating bone marrow-derived cells that may be altered in the setting of cancer and other chronic diseases. Utilizing both quantification and functional assays, including flow cytometry and colony forming unit assays, we are assessing the circulating bone marrow-derived progenitor cell populations in pediatric and adult patients with malignancies. We have identified that at the time of surgical resection of the primary tumor there is a surge in circulating bone marrow-derived cell populations that can enhance metastatic spread. We continue to collect blood samples from patients immediately before and within the week post-operatively to better understand the nature of the surge and how best to target it. We have an established collaboration with Dr. Sharon Savage to examine circulating bone marrow-derived cell populations in patients with Li Fraumeni syndrome, which is a high-risk cancer predisposition syndrome related to loss of tumor suppressor p53. We are enrolling patients in order to determine if changes in these bone marrow-derived cell populations predict tumor development in these patients. We are monitoring circulating levels of bone marrow-derived cells at the time of the yearly evaluation for cancer surveillance. We have also developed assays to examine biological correlates that can be measured in stored RNA samples in order to correlate outcome data with these biomarkers for metastatic risk. We have found a validated gene set in hematopoietic progenitor cells from patients with cancer from our microarray data from isolated CD34 cells from breast and colorectal carcinoma patients compared to healthy controls. The specific changes in these cells may help to serve as prognostic markers of disease progression as well as response to therapies. We have established a pre-clinical model system for testing microenvironment-targeting therapy in pediatric sarcomas. Utilizing a Ewings sarcoma xenograft tumor cell line we have performed flow cytometry and immunofluorescence to demonstrate the influx of myeloid cells into the tumor and pre-metastatic tissues. We also established this year monitoring metastatic progression in a syngeneic model using luciferase imaging. In this fashion, pre-metastatic, metastatic colonization and progression to visible metastasis can be followed and compared in treated and untreated groups without requiring multiple terminal end points. We are conducting pre-clinical investigations utilizing inhibitors targeting stromal cells specifically to assess impact on metastatic progression. We also now have a marker of tumor associated fibroblast activation and stromal cell lineage tracing mice in order to monitor activation of these cells in this process. We will perform these studies at the time of surgical resection of the primary tumor when overall tumor burden is low but metastatic risk is high. These pre-clinical studies will answer whether this approach to treatment may likely be a good window for targeting the recruitment of these bone marrow-derived tumor-associated cells that support tumor progression. Ultimately, I plan, in collaboration with Brigitte Widemann, to establish a phase I trial of tumor microenvironment targeting drugs in pediatric patients with relapsed solid tumors.
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