Study reveals how cancer cells survive chemotherapy in a zombie-like state
· News-MedicalScientists at Trinity College Dublin have made an important breakthrough in understanding how cancer cells can evade the cell-killing effects of chemotherapy and enter a "zombie-like state", called premature senescence, that can attract the wound healing properties of the immune system.
Although our immune system protects us from infection it also plays a critical role in coordinating repair and replacement of damaged tissue, which is a process called wound healing. The wound healing capabilities of the immune system stimulates cell division within damaged tissue to replace cells that have been lost through injury and brings extra nutrients and oxygen into the injured tissue by triggering the growth of new blood vessels. This is a complex and highly coordinated process, which ensures that new cells are only produced where and when they are needed.
However, cancers can exploit these wound healing capabilities for their own ends by masquerading as damaged tissue and tricking the immune system into helping malignant cells to divide and acquire extra oxygen and nutrients rather than killing them. For these reasons, cancers have been described as "wounds that do not heal", but how they switch on the wound healing capabilities of the immune system is still poorly understood.
The Trinity team, led by Prof. Seamus Martin, Smurfit Professor of Medical Genetics, and Dr Gokhan Gunay, Post-doctoral Research Fellow, found that IAPs functioned in this setting by neutralizing the cell-killing effects of molecules called 'Death Receptors' that were switched on in response to DNA damage provoked by chemotherapy.
Senescent cells are non-dividing zombie-like cells that undergo dramatic changes within a few days of exposure to chemotherapy, including becoming almost ten times bigger than a normal cell and ramping up genes associated with wound healing. These changes endow them with a greatly increased ability to secrete inflammatory mediators, which attracts cells of the immune system. The accumulation of senescent cells in tissues as we age is also thought to contribute to the inflammatory processes associated with aging, as well as a decline in the normal function of many tissues.
The Trinity scientists also found that senescent cells formed in response to chemotherapy are highly dependent on IAPs for their continued survival. Accordingly, compounds which neutralized IAPs (called IAP antagonists) selectively eliminated senescent cells by reactivating the Death Receptor self-destruct program within these cells.
What is the potential impact of this research?
Tumors that evade chemotherapy remain a major challenge for clinicians attempting to treat patients living with cancer. Improved treatment options that neutralize more of these tumors promise to improve quality of life and survival rates, but to deliver these scientists need to understand how tumors function and where their weaknesses may lie. This research isolates a new mechanism that explains how some tumors evade death and use the body's immune system to aid their recovery, as well as pinpointing promising new drug treatments (IAP antagonists) that killed them.
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