The selective antiproliferative effects of alpha-tocopheryl hemisuccinate and cholesteryl hemisuccinate on murine leukemia cells result from the action of the intact compounds.

In the present study we have established that the antitumor activity of alpha-tocopheryl succinate (TS, vitamin E succinate) and cholesteryl succinate (CS) result from the action of the intact TS and CS compounds and not from the release of alpha-tocopherol, cholesterol, or succinate. We report that treatment of murine leukemia cell lines C1498 (myeloid) and L1210 (lymphocytic), with the tris salts of TS or CS, but not alpha-tocopherol and tris succinate or cholesterol and tris succinate, significantly inhibit the growth of these tumor cells and significantly enhance doxorubicin-induced tumor cell kill in a similar fashion. In contrast, the treatments mentioned above did not adversely affect the growth of murine normal bone marrow cells (colony-forming unit-granulocyte-macrophage). In fact, colony-forming unit granulocyte-macrophage cell growth was stimulated by exposure to CS and TS (as well as their ether analogues) at concentrations above 100 microM. Furthermore, pretreatment of colony-forming unit granulocyte-macrophage cells with TS or CS appears to protect these normal cells from the lethal effect of doxorubicin exposure. Selective inhibition of leukemia cell proliferation (identical to that noted for CS and TS) was also observed following the treatment of cells with the nonhydrolyzable ether forms of CS (cholesteryloxybutyric acid) and TS (alpha-tocopheryloxybutyric acid). These findings suggest that TS, alpha-tocopheryloxybutyric acid, CS, and cholesteryloxybutyric acid may prove clinically useful as selective antitumor agents when administered alone or in combination with doxorubicin by a route that ensures tissue accumulation of the intact compound.

Enhanced lung colonization and tumorigenicity of fused cells isolated from primary MCA tumors.

Cells derived from cell-cell fusion events were clonally isolated from primary methylcholanthrene (MCA)-induced tumors in allophenic mice. Compared with non-fused cells isolated from the same cultures, the fused cells had markedly greater experimental metastasizing (lung colonizing) activity, but only slightly greater tumorigenicity and the same cloning efficiency in soft agar. Cell-cell fusion may thus contribute to the generation of tumor heterogeneity that underlies the process of tumor progression.

Cell fusion in tumor development and progression: occurrence of cell fusion in primary methylcholanthrene-induced tumorigenesis.

Definitive evidence for the occurrence of cell fusion in tumorigenesis was sought in methylcholanthrene-induced sarcomas. This was approached by using allophenic mice generated from strains differing for electrophoretic variants of the ubiquitous, dimeric enzyme glucose phosphate isomerase, with fusion assessed by heterodimer formation. Eight-three carefully trimmed primary tumor samples (from 23 individual tumors in allophenic mice) were analyzed, as were 1,140 clones derived from them. In all primary tumor samples, zymograms exhibited one GPI homopolymeric band. Expression of a hybrid band (indicative of a fusion event) was not observed in these samples. However, 9 (0.8%) of the tumor clones demonstrated a distinct and reproducible hybrid band which was uniformly lost upon recloning. Our data suggest that cell fusion, although uncommon, occurs in the clonogenic cell fraction during primary MCA tumorigenesis and is followed rapidly by chromosome segregation.

Multiple molecular forms of human lactoferrin. Identification of a class of lactoferrins that possess ribonuclease activity and lack iron-binding capacity.

Lactoferrin (Lf), the major iron-binding component of milk, also a major constituent of the specific granules of neutrophils involved in antimicrobial activity and a glycoprotein thought to play a role in regulatory functions in the hematopoietic system as well as other physiologic activities, is shown to occur in three isoforms. One, Lf-alpha, binds iron; the other two, Lf-beta and Lf-gamma, express potent RNase activity, but do not bind iron. The three isoforms are very similar or identical in Mr, pI, partial proteolytic peptide patterns, NH2-terminal amino acid sequence, and reactivity with mAbs and polyclonal antisera against the RNase and Lf, respectively. The finding of structurally similar but enzymatically distinct forms of Lf may be related to the diverse functions of the molecule.

A rapid and efficient method for testing immunohistochemical reactivity of monoclonal antibodies against multiple tissue samples simultaneously.

A flexible, efficient and rapid method was developed whereby a small volume of monoclonal antibody could be used to immunohistochemically stain many different tissues, simultaneously, on one standard glass slide. This method is based on the preparation of 'cores' of paraffin-embedded tissue from standard histology blocks. The paraffin cores are straightened, inserted into a casing cut from an ordinary drinking straw, mounted in a paraffin block and sectioned. Over 120 individual tissue samples can be organized on a slide and stained for screening or characterization with 0.25 ml of diluted primary antibody. Advantages of this paraffin core method include: great economies in time, reagents, tissue specimens and antibodies; ease of producing multiple, regular, stable, easily handled tissue core samples; direct identification of intratissue regions of interest for inclusion; efficient use of rare tissue samples; versatility for rapid construction of multiple tissue slides containing any combination of relevant tissues from a 'library' of tissue cores; and, no need for deparaffinization and reembedding of tissues.