**2.1 Complex cellular components in solid tumors**

Tumor is an aberrantly proliferating tissue that contains cancerous cells and host stromal cells such as vascular cells, inflammatory cells, and fibroblasts. These cells are crucial for cancer initiation, progression and metastasis and have been exploited as targets for cancer therapy and prevention (Ferrara and Kerbel, 2005; Fukumura and Jain, 2007; Hanahan and Weinberg, 2011).
