Drug resistance in cancer therapy: the Pandora's Box of cancer stem cells

Drug resistance is the main culprit of failure in cancer therapy that may lead to cancer relapse. This resistance mostly originates from rare, but impactful presence of cancer stem cells (CSCs). Ability to self-renewal and differentiation into heterogeneous cancer cells, and harboring morphologically and phenotypically distinct cells are prominent features of CSCs. Also, CSCs substantially contribute to metastatic dissemination. They possess several mechanisms that help them to survive even after exposure to chemotherapy drugs. Although chemotherapy is able to destroy the bulk of tumor cells, CSCs are left almost intact, and make tumor entity resistant to treatment. Eradication of a tumor mass needs complete removal of tumor cells as well as CSCs. Therefore, it is important to elucidate key features underlying drug resistance raised by CSCs in order to apply effective treatment strategies. However, the challenging point that threatens safety and specificity of chemotherapy is the common characteristics between CSCs and normal peers such as signaling pathways and markers. In the present study, we tried to present a comprehensive appraisal on CSCs, mechanisms of their drug resistance, and recent therapeutic methods targeting this type of noxious cells.

Automated summary

Drug resistance caused by cancer stem cells (CSCs) is the main reason for the failure and relapse of cancer therapy. CSCs possess the ability to self-renew and differentiate into heterogeneous cancer cells, and play a significant role in metastatic dissemination. Although chemotherapy can destroy most tumor cells, CSCs are left mostly intact, leading to resistance to treatment. It is crucial to understand the key features of drug resistance caused by CSCs in order to develop effective treatment strategies, but there are challenges in differentiating CSCs from normal cells.