Antiplacental ferritin antiserum for cancer diagnosis

Quantitative and qualitative studies of red cell ferritin in refractory anemia of myelodysplastic syndrome

The red cell ferritin (rFt) level in 10 patients with refractory anemia (RA) was measured and analyzed by column isoelectric focusing (IEF). The levels in 9 of the 10 patients (90.0%) were higher than the upper limit in healthy controls (MV +/- SD: male 14.3 +/- 10.3 ag/cell, female 7.5 +/- 3.6 ag/cell). The isoelectric point (pI) of rFt determined by IEF in healthy subjects ranged from 5.1 to 5.7. However, the pI ranges for RA patients varied widely; the pI value was thought to correlate with the severity of the morphological abnormalities of bone marrow (BM) erythroblasts. That is, the greater the proportion of morphologically abnormal erythroblasts with respect to all erythroid precursors, the lower the pI range for rFt. The rFt content was not related to serum iron, transferrin saturation, serum ferritin, reticulocyte count, red cell iron content, or BM erythroblast count. These data suggest that rFt synthesis in RA patients is influenced by factor(s) other than iron; this is considered an essential feature of erythropoiesis in myelodysplastic syndrome (MDS).

Immunoreactivities of human isoferritins

We have examined the immunoreactivities of antisera prepared against ferritins from human liver and HeLa cells to tissue ferritins and to individual isoferritins. In a radioimmune assay for HeLa ferritin the cross-reactivity of liver ferritin was about 2.5%. However, the apparent recovery of liver ferritin in the presence of different levels of HeLa ferritin was very much greater than that predicted from the measured cross-reactivity. This anomalous behaviour was eliminated by absorption of the HeLa antiserum with L-rich ferritins, suggesting that it represented interaction with common determinants in H and L subunits. The relative levels of H and L determinants measured by radioimmunoassay in individual isoferritins correlated with their relative contents of H and L subunits. However, in some parts of the isoferritin spectrum, the radioimmunoassay underestimated the H subunit content of L-rich isoferritins and overestimated the H subunit content of L-rich isoferritins and overestimated the H subunit content of H-rich isoferritins. This finding suggests differential expression of determinants in the various heteropolymers. These could arise from conformational changes leading to exposure or internalization of different determinants, or to recognition of determinants from certain subunit interactions.

Possibly unique subunit(s) of human ferritins responsible for tissue specificity

The biochemical characteristics of human placental and hepatic ferritins were compared. By DEAE cellulose column chromatography, placental ferritin was found to contain more acidic isoferritins, while hepatic ferritin was richer in basic isoferritins. The electrofocusing patterns of subunits revealed that placental ferritin contained at least one unique subunit on the acidic side and might lack one subunit on the basic side as compared with hepatic ferritin. It is hypothesized that microheterogeneities, immunological as well as biochemical, existing between placental and hepatic ferritins cannot be explained merely in terms of different proportions of known acidic and basic subunits, but appear to have resulted from the existence of the unique acidic subunit of placental ferritin and possibly also a unique basic subunit of hepatic ferritin.

Serum ferritin in hepatocellular carcinoma. A comparison with alphafetoprotein

The serum ferritin level was raised in 34 of 35 (97%) patients with hepatocellular carcinoma and in 20 of 23 (87%) with uncomplicated cirrhosis. Levels rose following therapeutic embolisation in 14 of 15 patients and continued to rise in 85% of all tumor patients who showed no clinical response to chemotherapy (intravenous Adriamycin) whereas in those who did respond the serum ferritin level fell. By contrast, there was a fall in serum alphafetoprotein immediately after embolisation but like serum ferritin, alphafetoprotein levels rose with disease progression and only fell in those achieving clinical remission. Serum ferritin has no role in the differential diagnosis of hepatocellular carcinoma but may be a useful marker in monitoring response to chemotherapy particularly in the alphafetoprotein-negative patient.

Characterization of ferritin from human placenta. Implications for analysis of tissue specificity and microheterogeneity of ferritins

Mammalian ferritins can be resolved into multiple components by isoelectric focusing, and each tissue contains a characteristic subset of isoferritins. Ferritin isolated from human liver was compared to acidic ferritin isolated from mid-gestational human placenta to define a structural basis for ferritin heterogeneity. Placenta ferritin contained several major bands with isoelectric points in the range of pI = 4.7-5.0 which were more acidic than the predominant isoferritins of human liver. Ferritin from each tissue was resistant to denaturation by 10 M urea and appeared to be identical by electron microscopy. Circular dichroism measurements revealed that placenta ferritin had substantially less ordered secondary structure than liver ferritin. Both types of ferritin contained only two subunits when analyzed by electrophoresis in sodium dodecyl sulfate gels, but isoelectric focusing of dissociated subunits in urea revealed 6-7 different components. In this system, placenta ferritin was enriched in the more acidic subunits and it completely lacked the most basic subunits noted in liver ferritin; placental ferritin had no unique components. Differences in isoelectric points among assembled ferritins from these two tissues appear to result from different proportions of these acidic and basic subunits.