The paradox of senescent-marker positive cancer cells: challenges and opportunities.

Senescence is an anti-tumour mechanism and hallmark of cancer. Loss or mutation of key senescence effectors, such as p16INK4A, are frequently observed in cancer. Intriguingly, some human tumours are both proliferative and senescent-marker positive (Sen-Mark+). Here, we explore this paradox, focusing on the prognostic consequences and the current challenges in classifying these cells. We discuss future strategies for Sen-Mark+ cell detection together with emerging opportunities to exploit senescence for cancer.