Novel second-generation di-2-pyridylketone thiosemicarbazones show synergism with standard chemotherapeutics and demonstrate potent activity against lung cancer xenografts after oral and intravenous administration in vivo.

We developed a series of second-generation di-2-pyridyl ketone thiosemicarbazone (DpT) and 2-benzoylpyridine thiosemicarbazone (BpT) ligands to improve the efficacy and safety profile of these potential antitumor agents. Two novel DpT analogues, Dp4e4mT and DpC, exhibited pronounced and selective activity against human lung cancer xenografts in vivo via the intravenous and oral routes. Importantly, these analogues did not induce the cardiotoxicity observed at high nonoptimal doses of the first-generation DpT analogue, Dp44mT. The Cu(II) complexes of these ligands exhibited potent antiproliferative activity having redox potentials in a range accessible to biological reductants. The activity of the copper complexes of Dp4e4mT and DpC against lung cancer cells was synergistic in combination with gemcitabine or cisplatin. It was demonstrated by EPR spectroscopy that dimeric copper compounds of the type [CuLCl](2), identified crystallographically, dissociate in solution to give monomeric 1:1 Cu:ligand complexes. These monomers represent the biologically active form of the complex.

Evidence that the fourth component of complement (C4) is carried on a high proportion of normal guinea-pig B lymphocytes.

The fourth component of complement (C4) has been demonstrated on the cell membrane of guinea-pig B lymphocytes isolated from blood, lymph nodes and spleen. In lymph nodes, at least, the C4-positive cells also carry receptors for C3 and most bind IgG-Fc. Few, if any, T lymphocytes have detectable C4. Resynthesis of cell-surface C4 could not be shown following in vitro culture of lymphocytes stripped of C4 by proteolytic enzymes, and it is likely that the C4 is passively acquired in vitro from tissue fluids, possibly by a mechanism similar to that involved in the binding of C4 (Chido and Rodgers determinants) to human erythrocytes.

Receptors on guinea-pig erythrocytes specific for cell-bound fourth component of human complement (C4).

Guinea-pig erythrocytes have receptors for heterologous (human and rabbit) complement activated by the classical pathway on cell surfaces. This was shown in the present study by rosette-forming reactions of guinea-pig erythrocytes and human lymphocytes or sheep erythrocytes pre-treated with antibody and human R3 complement. The binding is temperature-dependent and is enhanced by treating the guinea-pig erythrocytes with neuraminidase. The receptors were shown to be specific for C4 by inhibition tests employing a range of anti-human complement antibodies (including anti-Clq, -Cl inhibitor, -C4, -C2, -C3 and -C3b inactivator). Of these reagents, only anti-C4 inhibited the receptor activity, indicating that the guinea-pig erythrocyte C4-receptors differ from those on lymphocytes, monocytes, polymorphonuclear leucocytes and human erythrocytes which are reported to react with both C3b and C4b. In contrast to the strong affinity observed for heterologous C4, guinea-pig erythrocytes appear to react very weakly, if at all, with homologous C4.

Receptors for activated C3 on thymus-dependent (T) lymphocytes of normal guinea-pigs.

In a survey of lymphocyte subpopulations in normal guinea-pig blood, lymph node, spleen, thymus and peritoneal cavity, a considerable overlap was observed between the percentages of C3-receptor bearing lymphocytes (CRL) and of thymus-dependent (T) cells in lymph nodes. Simultaneous rosette-formation reactions with sheep erythrocytes carrying rabbit complement (EAC) and papain-treated rabbit erythrocytes (a T-cell marker) revealed that 20--50% of the lymph node CRL were T lymphocytes. These experiments and others on cell suspensions depleted of Ig-bearing (B) lymphocytes showed that between 8 and 36% of lymph node T cells have complement receptors. The frequency of T-CRL in other lymphoid tissues was lower, representing between 0 and 8% of the T-cell population. The reaction of T-CRL and EAC was not inhibited by EDTA which is known to inhibit the C3 receptor activity on macrophages.