An unexpected alliance between stress responses to drive oncogenesis

XBP1 is a well-characterized regulator of the unfolding protein response that is activated in response to unfolded or misfolded proteins or nutrient deprivation. The conventional wisdom is that XBP1 is activated to coordinate the unfolded protein response and promote cellular survival under stresses. A recent study provides intriguing evidence that, in triple-negative breast cancer, XBP1 plays a major role in promoting oncogenesis and cancer stem cell properties. Unexpectedly, XBP1 accomplishes this by recruiting hypoxia-inducible factor 1α and activating oncogenic transcriptional programs. This study reveals a surprising hierarchy and alliance between two stress regulators with distinct transcriptional outputs to promote an aggressive oncogenic state.