Antitumor effect of tuftsin

Summary Tuftsin, a physiological tetrapeptide derived from the Fc region of leukophilic IgG possesses a variety of immunopotentiating properties including the ability to act as an immunotherapeutic agent against the experimental tumors, L 1210 leukemia and Cloudman S-91 melanoma. Although the mechanism of action of tuftsin in vivo is not known, several types of leukocytes have been shown to become cytotoxic effector cells following activation with tuftsin. These cells presently include macrophages, natural killer cells, and granulocytes. The possibility that tuftsin can also activate other types of effector cells have not been ruled out. We feel this small peptide has a high potential (largely unrecognized) as an antitumor immunopotentiating agent. It is naturally occurring in man and appears to be relatively non-toxic. Its exact sequence (Thr-lys-Pro-Arg) is known and it can be chemically synthesized. Methods are also available to monitor the levels of tuftsin in body fluids. These properties along with its ability to control infectious disease make this agent one of the more promising immunopotentiators.     

Synthesis and biological activity of [L-3,4-dehydroproline3]-tuftsin

A 3,4-dehydroproline analogue of tuftsin (L-Thr-L-Lys-L-Pro-L-Arg) was prepared by the solid phase synthetic method. Following reversed-phase high performance liquid chromatography (HPLC) purification, the analogue was compared to tuftsin for its ability to enhance the chemotactic, bactericidal and phagocytic activities of polymorphonuclear leukocytes (PMN). Both tuftsin and [Δ³-pro³]-tuftsin elicited a similar significant chemotactic effect at a concentration of 10 μg/ml. A slight suppression of the chemotactic activity was observed with tuftsin at 10^?3 μg/ml and with [Δ³-pro³]-tuftsin at concentrations of 10^?3, 10^?2 (significant) and 10^?1 μg/ml. Although similar bactericidal activities were observed for both peptides, PMN exposed to [Δ³-pro³]-tuftsin exhibited increased phagocytic indicies 2–4 times that of tuftsin-treated PMN at concentrations of 0.4, 0.6 and 1.0 μg/ml.     

Immunohistochemical study of granular cell tumors of the neurohypophysis.

Six granular cell tumors (GCT) of the neurohypophysis were studied by immunohistochemical techniques. They were all labeled by peanut lectin (Arachis hypogaea) and three showed reactivity for S-100 protein. Unlike extracranial GCT, neuron specific enolase (NSE), myelin basic protein (MBP) and vimentin were not detected in the tumor cells. Glial fibrillary acidic protein (GFAP), keratin and desmin were also not observed. On the other hand, some showed reactivity for alpha-1-antitrypsin (AAT), alpha-1-antichymotrypsin (AAC) and cathepsin B. These results suggest that neurohypophysial GCT have some features different from extracranial GCT and that they may not be derived from Schwann cells.     

The O6-methylguanine-DNA methyltransferase from the hyperthermophilic archaeon Pyrococcus sp. KOD1: a thermostable repair enzyme

The enzyme O⁶-methylguanine-DNA methyltransferase (MGMT) is the most common form of cellular defense against the biological effects of O⁶-methylguanine (O⁶-MeG) in DNA. Based on PCR amplification using primers derived from conserved amino acid sequences of MGMTs from 11 species, we isolated the DNA region coding for MGMT from the hyperthermophilic archaeon Pyrococcus sp. KOD1. The MGMT gene from KOD1 (mgtk) comprises 522 nucleotides, encoding 174 amino acid residues; its product shows considerable similarity to the corresponding mammalian, yeast and bacterial enzymes, especially around putative methyl acceptor sites. Phylogenetic analysis of MGMTs showed that archaeal MGMTs were grouped with their bacterial counterparts. The location of the MGMT gene on the KOD1 chromosome was also determined. The cloned KOD1 MGMT gene was overexpressed using the T7 RNA polymerase expression system, and the recombinant protein was purified by ammonium sulfate fractionation, heat treatment, ion-exchange chromatography and gel filtration chromatography. The purified recombinant protein was assayed for its enzyme activity by monitoring transfer of [³H]methyl groups from the substrate DNA to the MGMT protein; the activity was found to be stable at 90°?C for at least 30?min. When the mgtk gene was placed under the control of the lac promoter and expressed in the methyltransferase-deficient Escherichia coli strain KT233 (Δada, Δogt) cells, a MGMT was produced. The enzyme was functional in vivo and complemented the mutant phenotype, making the cells resistant to the cytotoxic properties of the alkylating agent N-methyl-N′-nitro-N-nitrosoguanidine.