[Role of the stroma in the initiation and progression of tumors].

In the last decade, growing attention was paid to the observation that tumors did not only consist of cancer cells, they are rather a complex tissue-like mixture of tumor and stromal cells, which are playing an important role in the course of the malignant disease. Their contribution is so essential that without them, tumors are not even able to grow. This short review summarizes how stromal cells can promote the cancerous transformation and early development of tumors, how chronic inflammation contributes to the progression of cancer and how the stroma takes part in the induction of angiogenesis. The main mechanisms by which tumors can escape the immune surveillance will be demonstrated as well as the complex contributions of stroma to the invasion, intravasation and metastasis of cancer cells. Finally, possible and promising therapies will be presented that aim at the stroma and its main effects on the progression of tumors.