Figure 2.

Tumoral cell types that contribute to the heterogeneity of tumours. In addition to the most abundant tumoral cells, the genetic instability of tumours is responsible for the establishment of genetically distinct tumoral cell subpopulations, which may escape genomic detection as they may be diluted within the tumoral mass by the most abundant tumoral cells. Another important cellular component that usually bears genomic and transcriptomic differences with respect to the majority of tumoral cells are the cancer initiating/stem cells. The stromal cells that surround or are included into the tumoral mass may provide/receive proliferation/survival signals by crosstalking with tumoral cells. In certain neoplastic diseases, the stromal cells critically contribute to the survival or dissemination of the tumoral cells, and may bear genomic alterations that favour their tumor-supporting properties. These cancerized stromal cells and the rest of the cellular components of tumours must be targetted to achieve an efficient antitumoral response.