Figure 5.

Lineage tracing in cancer. (A) Specific cells (depicted in violet) in a tissue have higher tumorigenic potential. (A′) These cell(s)-of-origin of tumors are identified using Cre-lox lineage-tracing strategies. Through Cre-lox-mediated excision, oncogenes can be expressed by cell-specific transcriptional drivers (gain-of-function of oncogenes), whereas tumor-suppressor genes can be excised out in specific cells (loss-of-function of tumor-suppressor genes). The ability of different cell populations to produce cancerous growth is documented on such manipulations. (B) The basic concept of cancer stem cells that are the prime drivers of tumor growth. Only a few cells in a tumor are responsible for most of the tumor expansion. During destruction of tumor cells, only a few escaping CSCs are enough to cause regrowth of the tumor, and this is understood to be the underlying reason for relapse of cancer after treatments such as chemotherapy.