Characterization of the actin binding properties of the vasodilator-stimulated phosphoprotein VASP.

The vasodilator-stimulated phosphoprotein (VASP) colocalizes with the ends of stress fibers in cell-matrix and cell-cell contacts. We report here that bacterially expressed murine VASP directly interacts with skeletal muscle actin in several test systems including cosedimentation, viscometry and polymerization assays. It nucleates actin polymerization and tightly bundles actin filaments. The interaction with actin is salt-sensitive, indicating that the complex formation is primarily based on electrostatic interactions. Actin binding is confined to the C-terminal domain of VASP (EVH2). This domain, when expressed as a fusion protein with EGFP, associates with stress fibers in transiently transfected cells.

[Serum ferritin--a tumor marker in malignant lymphomas?]. / Ferritin im Serum--Ein "Tumormarker" bei malignen Lymphomen?

Serum ferritin concentration as a tumor associated marker was investigated in 535 patients with malignant lymphomas. The study included 207 patients with Hodgkin lymphomas, 196 patients with low grade malignant Non Hodgkin lymphomas and 132 patients with high grade malignant Non Hodgkin lymphomas of different tumor stages. Increased serum ferritin concentrations were found in 54% of the unselected patients. In particular, serum ferritin concentration was elevated in 12.3% of patients with stage I, in 33.8% of patients with stage II, in 72.2% of patients with stage III and in 94% of patients with stage IV. The serum ferritin levels correlated with the tumor mass. There was no difference between Hodgkin lymphomas and Non Hodgkin lymphomas. In patients with concomittant hepatocellular disease or during chemotherapy inadequate high serum ferritin concentrations were found, which did not correlate with tumor mass. In patients with primary bone marrow infiltration by some low grade malignant Non Hodgkin lymphomas serum ferritin levels correlated better with the tumor stages according to Rai than with the Ann-Arbor-classification. The serum ferritin concentration followed closely the activity of the disease: Increased pretreatment serum ferritin levels normalized completely, when patients achieved complete remission. In contrast, in patients with tumor relapse or tumor progression serum ferritin levels increased again. The data suggest that the serum ferritin concentration can be used for follow-up of patients with malignant lymphomas. Because of its limited specifity and low sensitivity it cannot be used as a screening test. Nevertheless, it is a helpful additional parameter for the control of the activity of the disease.

[Beta 2 microglobulin in serum--a "tumor marker" in malignant lymphomas?]. / Beta 2-Mikroglobulin im Serum--ein "Tumormarker" bei malignen Lymphomen?

Serum beta 2-microglobulin concentration was investigated in 221 patients with malignant lymphoma (Hodgkin type and non-Hodgkin type). In 55% of the unselected group of patients increased serum concentrations of beta 2-microglobulin were found. There was a close correlation between tumor extension and beta 2-microglobulin levels. In the tumor stage I the beta 2-microglobulin concentration was 1.65 +/- 0.45 mg/l, in the stage II 2.41 +/- 0.65 mg/l. The levels in the stage III (3.48 +/- 1.15 mg/l) and in the stage IV (5.49 +/- 1.99 mg/l) were significant higher than normal. Using longitudinal studies, measurement of beta 2-microglobulin was followed up during the course of the disease. During tumor regression by an effective antineoplastic therapy initially elevated beta 2-microglobulin concentrations decreased. In patients who achieved a complete remission a normalization of beta 2-microglobulin concentration was seen. We conclude from our findings that beta 2-microglobulin has the characteristics of a tumor associated marker in patients with malignant lymphomas. The low specificity and sensitivity limits the clinical use of this parameter.