Identification of leukemia-associated inhibitory activity as acidic isoferritins. A regulatory role for acidic isoferritins in the production of granulocytes and macrophages.

Abstract

Acidic isoferritins have been identified as leukemia-associated inhibitory activity (LIA), which suppresses colony and cluster formation of colony-forming unit-granulocyte macrophages from normal donors but not from patients with leukemia. LIA was detected in all ferritin preparations tested, including ferritin isolated from normal heart, spleen, liver, and placental tissues, and from the spleens of patients with chronic myelogenous leukemia and Hodgkin's disease. Purified preparations of LIA were composed almost entirely of acidic isoferritins, as determined by immunoassay, radioimmunoassay, and isoelectric focusing. The inhibitory activity in the LIA and ferritin samples was inactivated by a battery of antisera specific for ferritin, including those prepared against acidic isoferritins from normal heart and spleen tissues from patients with Hodgkin's disease, and those previously absorbed with basic isoferritins. Antisera absorbed with acidic isoferritins did not inactivate the inhibitory activity. Separation of LIA and chronic myelogenous leukemia and normal spleen ferritin by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing confirmed that the regions of peak inhibitory activity corresponded in each to an apparent molecular weight of approximately 550,000 and to a pI value of 4.7. Similar physicochemical characteristics included inactivation by methods that dissociate ferritin molecules into subunits and by treatment with trypsin, chymotrypsin, pronase, and periodate. The purified preparations were extremely stable to heat treatment. The glycoprotein nature of the inhibitory activity was substantiated because it bound to concanavalin A-Sepharose and was eluted off by alpha-methyl mannose. Inhibitory activity of the activity of the acidic isoferritins was detected at concentrations as low as 10(-17)-10(-19) M and iron saturation did not appear to be necessary for its action. These results implicate acidic isoferritins in the regulation of normal myelopoiesis and suggest a role for them in the progression of leukemia.

Suppression of Normal Hematopoiesis in Acute Leukemia: Effect of Leukemic Cells on Bone Marrow Stromal Cells and Hematopoietic Progenitor Cells.

“…Of these inhibitors, TNF-a (33, 34) and H-ferritin (35) are reported to be released from LC, especially from AMLcells. However, the present data showed that the TNF-a levels in all the LC-CMstudied were minimal or below the detectable limit, agreeing with a report of Griffin and colleagues (36), but contrasting with other reports in which LCfrom the majority of AMLpatients were shown to release considerable amounts of TNF-a (33,34). Causes of such discrepancy are not clear, but may be due mainly to differences in the cell source and the method of preparation of LC-CM.…”

EVALUATION OF SERUM FERRITIN AND SERUM IRON IN FREE-RANGING BLACK RHINOCEROS (DICEROS BICORNIS) AS A TOOL TO UNDERSTAND FACTORS AFFECTING IRON-OVERLOAD DISORDER

“…Sala et al (31) were unable to confirm the original results of Broxmeyer et al (29) and since 1992 there has been little work on this inhibitory activity of ferritin.…”

“…A role for ferritin in the regulation of haemopoiesis, apparently unrelated to iron storage, was proposed by Broxmeyer et al (29) who showed that the protein responsible for a 'leukaemia-associated inhibitory activity' (LIA) was an acidic isoferritin. This protein fraction, and an acidic isoferritin preparation from the spleen of a patient with chronic myeloid leukaemia, suppressed colony formation in vitro of CFU-GM, BFU-E and CFU-GEMM progenitor cells from the marrows of normal donors, but was ineffective in marrow or blood from patients with acute leukaemia, myelodysplasia and some other haematological disorders.…”

Structure and expression of ferritin genes in a human promyelocytic cell line that differentiates in vitro.

“…For example, the H/L ratio is about 2/3 in liver isoferritins and about 4/1 or 5/1 in heart isoferritins (4). The H/L subunit ratio characteristic of a particular tissue may be altered during normal cellular differentiation or in pathological conditions such as iron overload or neoplasia (7,15,34). The functional significance of such changes in H/L subunit ratio is only beginning to be understood.…”

“…It is the H subunitrich isoferritins which show the heaviest iron loading in human liver (3), but iron challenge of human monocytes preferentially stimulates L subunit synthesis (14) just as was noted for the rat. In addition, it is a glycosylated serum isoferritin with a high H/L subunit ratio (acidic isoferritin) which has been found to be associated with an inhibitory activity on normal myelopoiesis (7,27).…”