Transfection of tissue transglutaminase into a highly malignant hamster fibrosarcoma leads to a reduced incidence of primary tumour growth.

Reduced expression of the tissue transglutaminase in both murine and human tumours has been consistently associated with tumour growth and progression. To investigate the functional effects of transglutaminase expression we have transfected a constitutive human tissue transglutaminase expression construct into a highly malignant hamster fibrosarcoma cell line Met B. Met B clones expressing the exogenous tissue transglutaminase exhibited a reduced incidence of primary tumour formation and an increased adherence to tissue culture plastic and fibronectin coated surfaces when compared to transfected and non transfected control cells. Transglutaminase transfected clones exhibited no significant differences in their growth rates measured in vitro, cell morphology or levels of spontaneous apoptosis measured by the determination of detergent insoluble apoptotic envelopes. The data demonstrates a suppressive effect of tissue transglutaminase on tumour growth and confirms its importance in the phenotypic changes associated with the cancer process.

Interleukin-2-activated human effector lymphocytes mediate cytotoxicity by inducing apoptosis in human leukaemia and solid tumour target cells.

The mode of cytotoxic action employed by cytolytic lymphocytes remains unclear, with the possibility of several mechanisms being utilized dependent upon the activation state of the effector cell. In this work, the induction of apoptosis in target cells by 'killer' lymphocytes at differing states of activation has been studied. Although the cytotoxicity of natural killer (NK) cells and recombinant human interleukin-2 (rhIL-2) or interferon-alpha (IFN-alpha)-activated effector cells, against NK-sensitive target cells, was high, their cytotoxic action appeared to be mediated via differing pathways. Effector cells activated short term (4 hr) with rhIL-2 and those mediating rhIL-2 lymphokine-activated killer (LAK) activity after long-term (4 day) activation were found to induce the formation of sodium dodecyl sulphate (SDS)-insoluble apoptotic bodies in NK-sensitive target cells, as well as increasing the level of activity of the apoptosis related enzyme tissue transglutaminase, thus suggesting the induction of the apoptotic pathway as a means of effecting target cell death. Non-activated and short-term (4 hr) IFN-alpha-activated effector cells did not appear to utilize this pathway in the target cell as their means of cytotoxicity. Effector cells showing LAK activity were also cytotoxic towards NK-insensitive cells, and this cytotoxicity again appeared to be mediated via the apoptotic pathway.

Apoptosis: a potential role for cytosolic transglutaminase and its importance in tumour progression.

The relationship between transglutaminase activity, apoptosis and the propensity of a tumour to metastasise, was investigated in a series of metastatic variants of an HSV-2 induced hamster fibrosarcoma and two metastatic variants of the B16 mouse melanoma. The data suggest an inverse relationship between metastatic potential and cytosolic transglutaminase activity. A direct relationship was found between measured cytosolic activity and the levels of the endogenous product of transglutaminase, the protein crosslink epsilon(gamma-glutamyl)lysine. Increasing metastatic potential and decreasing cytosolic transglutaminase activity was accompanied by a corresponding decrease in the number of detergent-insoluble apoptotic envelopes isolated from variant cell lines. These apoptotic envelopes were found to be highly crosslinked structures, containing more than 85% of the cells content of epsilon(gamma-glutamyl)lysine. These data are in keeping with the idea that a major role for the cytosolic transglutaminase is in the formation of the highly crosslinked apoptotic envelope during programmed cell death and that perturbation of this function may be an important determinant in the development of the metastatic phenotype.

The existence of an inactive form of transglutaminase within metastasising tumours.

Separation by anion exchange chromatography of detergent extracts from a poorly metastatic HSV-2-induced hamster fibrosarcoma, its highly metastatic variant and a highly metastatic rat fibrosarcoma indicated the presence of an inactive form of transglutaminase antigen, when eluent fractions were assayed for transglutaminase activity and antigen. This inactive antigenic transglutaminase was clearly separable from the particulate and cytosolic forms of the transglutaminase enzyme. Unlike tumours, its presence could not be demonstrated in extracts from normal rat liver. Measurement of activity levels during tumour growth indicated that the progression of the two highly metastatic tumours was accompanied by a decrease in cytosolic transglutaminase activity, whilst the activity of this enzyme form remained constant in the poorly metastatic tumour. Measurement of antigen levels indicated an inverse relationship between the level of inactive transglutaminase and the level of cytosolic transglutaminase activity, suggesting that the two forms are inter-related. Gel filtration indicated the molecular weight of the inactive form to be greater than both the particulate and cytosolic forms, and it was estimated to be 120,000. Partial proteolysis of the semi-purified inactive form, by either trypsin or thrombin, led to its activation and to the appearance of a transglutaminase similar in molecular weight and ionic mobility, both by anion-exchange chromatography and electrophoresis, to the cytosolic transglutaminase.

Immunological similarities between cytosolic and particulate tissue transglutaminase.

At the present time it is uncertain whether or not the cytosolic and particulate forms of tissue transglutaminase are distinct and discrete enzymes. In this study a number of physical and immunological similarities between the two forms are demonstrated, indicating that they share some common epitopes, although their native confirmations may differ.

Anterior interosseous syndrome.

Four cases of anterior interosseous syndrome are presented. Two patients failed to respond to nonsurgical treatment and were surgically explored. Constricting bands found at surgery were divided, and function returned completely within a few weeks. The other 2 patients were treated nonsurgically, with slow improvement in symptoms.