A Nature study identified specific genetic elements that promote retention of extrachromosomal DNA (ecDNA) in cancer cells, clarifying a key mechanism behind oncogene amplification and rapid tumor evolution. In parallel, researchers mapped tumor‑reactive CD8+ T cell clusters and their preferential interactions with tumor and antigen‑presenting cell subpopulations, defining immune‑landscape niches in melanoma. Together these findings sharpen targets for therapies that either disrupt ecDNA‑driven oncogene dosage or selectively expand tumor‑reactive T cells.