TUMOR-CELL CYTOLYSIS MEDIATED BY VALORPHIN, AN OPIOID-LIKE FRAGMENT OF HEMOGLOBIN BETA-CHAIN

Valorphin, an endogenous opioid-like hemoglobin fragment, is cytotoxic for L929 and K562 tumor cells in 10(-7)-10(-13) M concentration range . Because cytolytic effects induced by valorphin in K562 cells are inh ibited by naloxone, opioid receptors should be involved in induction o f valorphin-mediated tumor cell death. Three distinct cytolytic proces ses, differing in the onset time and the development time, take place with K562 cells within 10-18 h of incubation with valorphin. All three processes are not associated with apoptotic mechanism of cell death. (C) 1997 Elsevier Science Inc.