"In this illustrated model, T cells afflicted by harsh conditions inside the tumor experience endoplasmic reticulum (ER) stress, symbolized here by the ""burning"" ER (orange) surrounding the nucleus (purple and turquoise). Severe ER stress responses driven by IRE1a-XBP1 pathway signaling alter the function of mitochondria (blue-gray) and consequently limit optimal T cell responses to cancer cells (red)."