Targeting Unique Features of Quiescent Cancer Stem Cells to Overcome Resistance and Recurrence in Cancer Therapy: A Review

Quiescent cancer stem cells (QCSC) are non-proliferating cells that survive in the G0 phase and have low ki-67 expression and high p27 expression. QCSCs have the ability to evade most chemotherapy, and some subsequent treatments may result in a higher proportion of quiescent cancer stem cells in the tumor. QCSCs are also associated with cancer recurrence rates because they can re-enter the cell cycle to proliferate when tumor environmental conditions are favorable. QCSCs cause high rates of drug resistance and tumor recurrence, therefore it is necessary to understand the properties of QCSCs. QCSCs have a mechanism that regulates the transition between the proliferative phase and the stationary phase in cancer cells, therefore it is necessary to find new treatments to eliminate QCSCs in tumors. In this review, the authors discuss the mechanisms of QCSCs in inducing drug resistance and tumor recurrence as well as therapies to target QCSCs so that the rate of drug resistance and tumor recurrence can be reduced, including in this review: (i) identifying reactive quiescent cancer cells and eliminating them through anticancer reagents. cell cycle dependent; (ii) modulating the transition from the quiescent to the proliferative phase; and (iii) eliminate QCSC by targeting its unique features. Targeting cancer cells that are in proliferating and stationary phase may ultimately be used as a more effective therapeutic strategy for cancer treatment.