Therapy Induced Senescent Tumor Cells Increase Cancer Stemness.
Cellular senescence is defined as permanent cell cycle arrest (Alessio et al., 2019). Under the stressful condition such as physical and chemical insult, cell eventually turns into senescence (Kong et al., 2019). Therapy induced senescence is a type of cellular senescence induced by irradiation or chemotherapy (Joyner et al., 2006). Several previous studies showed increased expression of stem cell related properties with cellular senescence (Tsolou et al., 2019). Here, we proceeded research to prove cellular senescence induced by doxorubicin increases cancer cell stemness in human breast cancer. Senescence associated β-galactosidase assay and quantitative polymerase chain reaction analysis revealed BT474, a breast cancer cell line, showed senescence phenotype after treatment of doxorubicin expressing p16INK4A (Loh et al.). Following qPCR and western blot analysis also revealed a stem cell marker CD133 was increased with the senescence marker p16INK4A after treatment of doxorubicin (Dai et al., 2018) Flow cytometry showed the proportion of CD133 and p16INK4A doublepositive cells was increased after doxorubicin treatment. In this regard, senescent tumor cells caused by chemotherapy increase cancer cell stemness which is closely related to cancer relapse (Dou and Berger, 2018). It is anticipated that targeting senescent tumor cells is a new target to prevent cancer relapse.