What is the tumor microenvironment?
Cancers are not just masses of malignant cells but with many other non-malignant cells and non-cellular components. Interactions between malignant and non-malignant cells create the tumor microenvironment (TME). The non-malignant cells of the TME have a dynamic and often tumor-promoting function at all stages of carcinogenesis. These can be widely classified into three main groups: cells of haematopoietic origin, cells of mesenchymal origin and non-cellular components. Tumors of different origins and different stages of progression will inevitably contain components in various proportions. Nonetheless, these three classes of stromal components represent the most abundant elements present in the microenvironment of solid tumors.
Cells of haematopoietic origin. This compartment consists of cells that arise in the bone marrow .
Cells of mesenchymal origin. These comprise cells derived from the mesenchyme and include fibroblasts, myofibroblasts, mesenchymal stem cells (MSCs), adipocytes and endothelial cells.
Non-cellular components. The major non-cellular component of the tumor microenvironment is the extracellular matrix (ECM), which consists of many distinct components — including proteins, glycoproteins and proteoglycans — that enable its functions both structurally and functionally
These three groups cannot to be the clinical target of cancer treatment at present. Cancer chemotherapy does not only target malignant cells and non-malignant cells, but that many soluble factors in the TME contribute to success of the treatment.
We recommend therefore the use of molecular target drugs (thalidomide, celecoxib, valproic acid et al) and low dose cytotoxic drug(s).