Caspase 3–mediated stimulation of tumor cell repopulation  during cancer radiotherapy

 Qian Huang et al., Nat. Med. 2011, 17:860-66

Speaker: Ya-Ting Chu (朱雅婷)                                    Time: 13:10~14:00, Dec. 7, 2011

Commentator: Dr. Chiou-Feng Lin (林秋烽老師)       Place: Room 601

Abstract

Tumor is one of the greatest hazards to human health problems. Most patients are treated by surgery, radiotherapy, or chemotherapy. The induction of apoptosis in tumor cells has been a major goal in cancer radiotherapy. However, there is a probability of tumor recovery. Previous study indicated that tumors respond to radiotherapy by initiating a process called accelerated repopulation. In this process, the few surviving cells that escaped from death after exposure to radiotherapy or chemotherapy can rapidly repopulate. Apoptosis has been demonstrated to promote the growth of cells and tissues, for example, it promotes would healing and normal tissues regeneration by stimulating stem cell proliferation. In this paper, the authors showed that radiation-induced apoptotic cells can stimulate the surviving tumor cell proliferation through the growth-stimulating signals. This growth stimulation depended primarily on activated caspase 3, a key executioner in apoptosis. To characterize the downstream pathway of caspase 3, they found that caspase 3 activated calcium-independent phospholipase A2 (iPLA₂), which resulted in the extracellular release of arachidonic acid and its metabolite PGE₂, a key promoter of tumor growth. Therefore, this newly discovered caspase-mediated tumor repopulation mechanism has a key role in designing cytotoxic cancer therapy.

References

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