Since earlier reports had revealed a compromised solution structure of prolactin at lower pH [41] with reduced ability to bind to prolactin receptors in surface plasmon resonance assays [32], we examined whether the suppressive effect of acidic pH is selective for prolactin receptor signaling or reflects a general effect on cell surface receptor signaling in cancer cells stressed by exposure to low pHe. The gene discussed is PRLR; the disease is cancer.