Immunocytochemical identification and localization of the Mr 22,000 calcium-binding protein (sorcin) in an adriamycin-resistant myelogenous leukemia cell line.

Monoclonal antibody against the Mr 22,000 calcium-binding protein (sorcin) from an adriamycin-resistant myelogenous leukemia cell line K562 (K562/ADM) was prepared and used as a probe to study the localization of sorcin in K562/ADM cells and the parental cell line, K562. Analysis of extracts from K562/ADM cells by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorescence image analysis showed that K562/ADM cells possessed abundant sorcin in the cytoplasm which was almost entirely absent from the drug-sensitive parental cell line, K562. Furthermore, immuno-electron microscopic studies revealed that sorcin was closely associated with free ribosomes, rough endoplasmic reticulum, mitochondria, microfilament bundles and perinuclear membranes. These observations provide the first clue that the Ca-binding protein, sorcin, may play an important role in the development of the multidrug resistance phenomenon, although the relationship between sorcin and P-glycoprotein is still unknown.