Figure 1: Cancer stem cells are resistant to conventional therapies. Tumors are heterogeneous and composed of both cancer cells (light purple) and a sub-population of highly resistant cell population that carry stemness markers or cancer stem cells (CSCs) (shown here in dark purple). Conventional chemotherapeutics, radiation and targeted therapies can eliminate the bulk of the tumors. However, the resistant sub-population of CSCs does not respond to most forms of therapies and potentially give rise to secondary tumors.