Increased numbers of S100A4 + cells are associated with poor prognosis in patients who have cancer. Although the metastatic capabilities of S100A4 + cancer cells have been examined, the functional role of S100A4 + stromal cells in metastasis is largely unknown. To study the contribution of S100A4 + stromal cells in metastasis, we used transgenic mice that express viral thymidine kinase under control of the S100A4 promoter to specifically ablate S100A4 + stromal cells. Depletion of S100A4 + stromal cells significantly reduced metastatic colonization without affecting primary tumor growth. Multiple bone marrow transplantation studies demonstrated that these effects of S100A4 + stromal cells are attributable to local non-bone marrow-derived S100A4 + cells, which are likely fibroblasts in this setting. Reduction in metastasis due to the loss of S100A4 + fibroblasts correlated with a concomitant decrease in the expression of several ECM molecules and growth factors, particularly Tenascin-C and VEGF-A. The functional importance of stromal Tenascin-C and S100A4+ fibroblast-derived VEGF-A in metastasis was established by examining Tenascin-C null mice and transgenic mice expressing Cre recombinase under control of the S100A4 promoter crossed with mice carrying VEGF-A alleles flanked by loxP sites, which exhibited a significant decrease in metastatic colonization without effects on primary tumor growth. In particular, S100A4+ fibroblast-derived VEGF-A plays an important role in the establishment of an angiogenic microenvironment at the metastatic site to facilitate colonization, whereas stromal Tenascin-C may provide protection from apoptosis. Our study demonstrates a crucial role for local S100A4 + fibroblasts in providing the permissive "soil" for metastatic colonization, a challenging step in the metastatic cascade.stromal fibroblasts | metastasis-associated fibroblasts | tumor microenvironment | metastatic microenvironment A bout 90% of cancer deaths are attributable to systemic disease associated with metastasis (1). Among the steps involved in metastasis, the colonization step is considered the most challenging for an invading cancer cell (2). With metastatic disease as the leading cause of death among patients who have cancer (3), a greater need is emphasized for a better understanding of the metastatic process so as to identify efficacious cancer therapies. S100A4 (also known as CAPL, p9Ka, 42A, pEL98, mts1, metastasin, calvasculin, 18A2, or FSP1) is a member of the S100 calcium-binding family, which has a high prognostic significance for metastasis in patients with cancer (4). Several studies have demonstrated a correlation between increased numbers of S100A4 + cells and poor prognosis of patients for a variety of cancer types, including colorectal adenocarcinoma, non-small cell lung cancer, breast adenocarcinoma, gastric cancer, esophageal squamous carcinoma, bladder cancer, prostate adenocarcinoma, melanoma, and ovarian carcinoma. Although S100A4 + cells encompass a variety of cell types, including malignant c...
Tumor microenvironment has a major role in cancer progression and resistance to treatment. The bone marrow (BM) is a dynamic network of growth factors, cytokines and stromal cells, providing a permissive environment for leukemogenesis and progression. Both BM stroma and leukemic blasts promote angiogenesis, which is increased in acute lymphoblastic leukemia and acute myeloid leukemia. Growth factors like vascular endothelial growth factor (VEGF), basic fibroblast growth factor and angiopoietins are the main proangiogenic mediators in acute leukemia. Autocrine proleukemic loops have been described for VEGF and angiopoietin in hematopoietic cells. Interactions of stromal cells and extracellular matrix with leukemic blasts can also generate antiapoptotic signals that contribute to neoplastic progression and persistence of treatment-resistant minimal residual disease. High expression of CXC chemokine ligand 4 (CXCR4) by leukemic blasts and activation of the CXCR4–CXCL12 axis is involved in leukemia progression and disruption of normal hematopoiesis. Leukemia-associated bone microenvironment markers could be used as prognostic or predictive indicators of disease progression and/or treatment outcome. Studies related to bone microenvironment would likely provide a better understanding of the treatment resistance associated with leukemia therapy and design of new treatments.
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