fig1

Figure 1. Therapeutic resistance - Developing tumors begin with a single immortalized cell that may have a single therapeutic target that can act to stop those cells from replication. For example, Tamoxifen (TAM) is the most common therapy used for the treatment of estrogen receptor-positive (ER+) breast cancer and it is used successfully in many cases. However, there are advanced-stage breast cancers that are plagued with mutated subpopulations of immortalized cells and cancer stem cells that play a key role in breast cancer progression, and metastasis. In these cancers, a single targeted therapy may produce a remission by successfully arresting some of the immortalized cells that have been targeted. However, if the remaining subpopulations of cells are driven by different mechanisms and prove to be chemoresistant, they will persist during remission and ultimately produce a relapsed cancer that is fully refractory to the initial treatment or combination of treatments.