Cleavage of cFLIP restrains cell death during viral infection and tissue injury and favors tissue repair

Cell death coordinates repair programs following pathogen attack and tissue injury. However, aberrant cell death can interfere with such programs and cause organ failure. Cellular FLICE-like inhibitory protein (cFLIP) is a crucial regulator of cell death and a substrate of Caspase-8. However, the physiological role of cFLIP cleavage by Caspase-8 remains elusive. Here, we found an essential role for cFLIP cleavage in restraining cell death in different pathophysiological scenarios. Mice expressing a cleavage-resistant cFLIP mutant, CflipD377A, exhibited increased sensitivity to severe acute respiratory syndrome coronavirus (SARS-CoV)-induced lethality, impaired skin wound healing, and increased tissue damage caused by Sharpin deficiency. In vitro, abrogation of cFLIP cleavage sensitizes cells to tumor necrosis factor(TNF)-induced necroptosis and apoptosis by favoring complex-II formation. Mechanistically, the cell death-sensitizing effect of the D377A mutation depends on glutamine-469. These results reveal a crucial role for cFLIP cleavage in controlling the amplitude of cell death responses occurring upon tissue stress to ensure the execution of repair programs.

Differences of the Immune Phenotype of Breast Cancer Cells after Ex Vivo Hyperthermia by Warm-Water or Microwave Radiation in a Closed-Loop System Alone or in Combination with Radiotherapy

The treatment of breast cancer by radiotherapy can be complemented by hyperthermia. Little is known about how the immune phenotype of tumor cells is changed thereby, also in terms of a dependence on the heating method. We developed a sterile closed-loop system, using either a warm-water bath or a microwave at 2.45 GHz to examine the impact of ex vivo hyperthermia on cell death, the release of HSP70, and the expression of immune checkpoint molecules (ICMs) on MCF-7 and MDA-MB-231 breast cancer cells by multicolor flow cytometry and ELISA. Heating was performed between 39 and 44 °C. Numerical process simulations identified temperature distributions. Additionally, irradiation with 2 × 5 Gy or 5 × 2 Gy was applied. We observed a release of HSP70 after hyperthermia at all examined temperatures and independently of the heating method, but microwave heating was more effective in cell killing, and microwave heating with and without radiotherapy increased subsequent HSP70 concentrations. Adding hyperthermia to radiotherapy, dynamically or individually, affected the expression of the ICM PD-L1, PD-L2, HVEM, ICOS-L, CD137-L, OX40-L, CD27-L, and EGFR on breast cancer cells. Well-characterized pre-clinical heating systems are mandatory to screen the immune phenotype of tumor cells in clinically relevant settings to define immune matrices for therapy adaption.