Researchers have discovered that heat-shock proteins, which help cells respond to stresses such as nutrient and oxygen shortages, form large “epichaperome” protein complexes in some cancer cells. Monica L. Guzman of Weill Cornell Medical College, Gabriela Chiosis of Memorial Sloan Kettering Cancer Center, and coworkers, who carried out the study, propose that the known drug sensitivity of one of the proteins and the prevalence of epichaperomes in cancer cells may make the complexes selective targets for cancer treatments (Nature 2016, DOI: 10.1038/nature19807). The heat-shock protein HSP90 joins with dozens of chaperones and other proteins to form epichaperomes in what the researchers call type 1 cells originating from leukemia and breast, pancreatic, lung, and other cancers. However, in what they call type 2 cancer cells and in noncancerous cells, they find that most HSP90s and other heat-shock proteins exist in isolated form or only assemble into small complexes. A known HSP90 inhibitor binds more tightly to HSP90 in epichaperomes than it does to solo HSP90 and kills more type 1 cancer cells than type 2 or noncancerous cells, indicating that epichaperomes may be promising targets for selective cancer therapies.