Synergistic effects of valproic acid and mitomycin C in adenocarcinoma cell lines and fresh tumor cells of patients with colon cancer.

Valproic acid has been demonstrated to mediate cytotoxic effects against tumor cells by acting as a histone-deacetylase inhibitor. However, to date, there are only limited data on the effects of valproic acid in colon cancer. Moreover, information regarding combinations of the drug with chemotherapeutic agents is very limited. The latter is of interest as there is increasing evidence for synergism between so-called "molecular targeting drugs" and chemotherapy. We first demonstrated that valproic acid dose-dependently reduced the viability of adenocarcimona cell lines. After co-incubation with a variety of chemotherapeutic agents, only valproic acid in combination with mitomycin C consistently induced synergistic growth inhibition in all cell lines. To confirm these results in an ex vivo situation, five samples of fresh colon cancer cells were studied. Again, the effect of valproic acid on the viability of the fresh tumor cells was dose dependent. In four of five samples of freshly isolated colon cancer cells, the synergistic effect of valproic acid and mitomycin C on the inhibition of cell growth was confirmed by calculation of the combination index by multiple drug effect analysis. In conclusion, this is the first demonstration that valproic acid as a model substance for histone-deacetylase inhibitors is effective in tumor cells freshly isolated from patients with colon cancer and that the combination of mitomycin C and valproic acid synergistically decreases viability of colon cancer cells.

T cell-mediated neuroprotection involves antithrombin activity.

Functional loss after injury to the mammalian central nervous system (CNS) has been attributed not only to the immediate loss of neurons but also to secondary neuronal degeneration caused by the toxicity of physiological compounds present in abnormally high amounts as a result of the injury. One such compound appears to be the protease thrombin. Here we show that the beneficial effect of T cells directed against myelin self-antigens can be attributed, at least in part, to the ability of these 'autoimmune' T cells to produce antithrombin III. Using transgenic mice lacking the thrombin receptor PAR-1, we also present molecular evidence indicating that down-regulation of PAR-1 by genetic manipulation leads to increased post-traumatic survival of CNS neurons. We further show that the ability of autoimmune T cells to produce thrombin inhibitors and to exert post-traumatic neuroprotection are both independent of their PAR-1 expression. These findings suggest that thrombin plays a key role in post-injury neuronal survival, and that its post-traumatic toxicity can be down-regulated by appropriate alteration of the amounts of PAR-1 receptors or of antithrombin III, the latter achieved by T cell-mediated autoimmunity.

Calcium oxalate granuloma of the nose of a chronically dialysed nephritic patient.

The patient was a 54-year-old woman who had been suffering from chronic tubulo-interstitial nephritis for about seven years, requiring haemodialysis. More recently, she developed a polypoid mass in the left nasal cavity causing discomfort on breathing and slight epistaxis. The tumour was of gritty consistency and measured 28 x 8 x 5 mm. Microscopy showed a lobulated almost cystic structure composed of granulation tissue with comparatively few plasma cells and many multinucleated giant cells lining the spaces filled with crystalline deposits of calcium oxalate.

Self-Protective mechanism awakened by glutamate in retinal ganglion cells.

The progression of degeneration in chronic optic neuropathies or in animal models of optic nerve injury is thought to be caused, at least in part, by an increase in glutamate to abnormally high concentrations. We show here that glutamate, when injected in subtoxic amounts into the vitreal body of the rat eye, transduces a self-protecting signal that renders the retinal ganglion cells resistant to further toxicity, whether glutamate-derived or not. This neuroprotective effect is attained within 24 h and lasts at least 4 days. Western blot analysis of rat retinas revealed increased amounts of bcl-2 four days after injection of glutamate in either subtoxic or toxic (120 nmol) amounts, but not after saline injection. The effects of intravitreal glutamate or saline injection on the secretion of neurotrophins by retinal ganglion cells was evaluated in rat aqueous humor 6 h, 1 day, and 4 days after injection. Nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 showed similar kinetic patterns in all of the eyes; that is, they increased to a peak 1 day after the injection and returned to normal by day 4. However, increased amounts the neurotrophin receptor TrkA within the retinal ganglion cell layer and nerve fiber layer were detected 1 day after injection of glutamate in either toxic or subtoxic amounts, but not after saline injection. This finding points to the possible involvement of neurotrophin receptors in regulation of the cellular responses to glutamate challenge. Identification of the intracellular signals that trigger the glutamate-induced self-protective mechanism would shed light on the genetic balance needed for survival, and guide the development of drugs for the up-regulation of desired genes and their products.

Extraskeletal Ewing's sarcoma of the nose.

A 20-year-old woman presented with nasal obstruction and slight epistaxis. The obstructing lesion was excised and microscopy showed a neoplasm composed of comparatively uniform undifferentiated cells forming solid nests. The cytoplasm of the cells was clear but poorly demarcated, partly vacuolated and contained much glycogen. Although widespread in the nasal mucosa, the cells did not penetrate into the underlying bone. The cells expressed the MIC2 gene (using the CD99 marker). Electron microscopy showed simple cells with a small number of mitochondria, many glycogen particles; there were no neurosecretory granules present. Early surgical treatment followed by chemo- and radiotherapy have greatly improved the prognosis of EWS: extraskeletal Ewing's sarcoma (EWS/PNET).

Thrombin attenuation is neuroprotective in the injured rat optic nerve.

The functional loss that often follows injury of the mammalian CNS has been attributed not only to the immediate neural loss, but also to secondary neuronal degeneration caused by toxic biochemical mediators in the environment of the injured nerve. We report here that a high thrombin content, produced as a result of injury-induced activation of prothrombin, appears to be an important mediator of secondary damage. Measurement of post-traumatic neuronal survival in vivo revealed that post-traumatic local application of the thrombin inhibitor N-alpha-(2-naphthylsulphonylglycyl)-4-(D,L)-amidinophenylalanine piperidide acetate in the rat optic nerve subjected to mild partial crush injury left twice as many retinal ganglion cells with functioning axons as in controls. Thus, by readjusting thrombin activity, thereby possibly obtaining a moderate post-traumatic increase and thus gaining the benefit of thrombin without its toxic effects, it may be possible to create an environment that is more favourable for post-traumatic survival.

Injury-induced gelatinase and thrombin-like activities in regenerating and nonregenerating nervous systems.

It is now widely accepted that injured nerves, like any other injured tissue, need assistance from their extracellular milieu in order to heal. We compared the postinjury activities of thrombin and gelatinases, two types of proteolytic activities known to be critically involved in tissue healing, in nonregenerative (rat optic nerve) and regenerative (fish optic nerve and rat sciatic nerve) neural tissue. Unlike gelatinases, whose induction pattern was comparable in all three nerves, thrombin-like activity differed clearly between regenerating and nonregenerating nervous systems. Postinjury levels of this latter activity seem to dictate whether it will display beneficial or detrimental effects on the capacity of the tissue for repair. The results of this study further highlight the fact that tissue repair and nerve regeneration are closely linked and that substances that are not unique to the nervous system, but participate in wound healing in general, are also crucial for regeneration or its failure in the nervous system.

Actinomycosis of the middle ear.

Another case of actinomycosis of the ear is described in a nine-year-old boy, drawing attention to the increasing incidence of diseases of the ear considered to be rare. The patient presented with the clinical signs of chronic purulent otitis media, not responding to conservative treatment. After the diagnosis of actinomycosis was established the patient was treated by surgery and long-term antibiotic medication, responding favourably.

Pregnancy and malignant neoplasms of the head and neck.

This paper, based on a literature review, deals with the occasional development of a head and neck neoplasm in the pregnant woman. This rare event makes for some challenging problems in patient management, insofar as the otolaryngologist is actually responsible for taking care of 2 patients -- the mother and her unborn child. In particular, 4 tumor types have figured prominently among those head and neck tumors arising in pregnant women: cancer of the larynx, cancer of the thyroid, malignant melanomas, and malignant lymphomas of the head and neck. Of these, the most common appear to be melanomas, followed by lymphomas, thyroid carcinomas, and, finally, laryngeal carcinomas. The thyroid tumors, lymphomas, and laryngeal carcinomas do not appear to behave more aggressively in pregnant than in nonpregnant patients; there is, however, some anecdotal evidence to suggest that melanomas in pregnant women may be more aggressive neoplasms than similar-stage tumors in nonpregnant women. One difficulty in treating any of these tumor types in this clinical setting is the limitation that may be imposed on the use of adjuvant therapy by the presence of the unborn child, which may put the attending physicians in the difficult position of balancing less aggressive therapy for the mother against the potential for harming the baby through use of toxic systemic therapy.

GTP-dependent conformational changes associated with the functional switch between Galpha and cross-linking activities in brain-derived tissue transglutaminase.

GTP and Ca2+, two well-known modulators of intracellular signaling pathways, control a structural/functional switch between two vital and mutually exclusive activities, cross-linking and Galpha activity, in the same enzyme. The enzyme, a brain-derived tissue-type transglutaminase (TGase), was recently cloned by us in two forms, one of which (s-TGN) lacks a C-terminal region that is present in the other (l-TGN). Immunoreaction with antibodies directed against a peptide present in the C-terminus of l-TGN but missing in s-TGN suggested that this site, which is located in the C-terminal fourth domain, undergoes conformational changes as a result of interaction between l-TGN and GTP. Site-directed mutagenesis suggested that the third domain is involved in mediating the inhibition of the cross-linking activity. These results were supported by molecular modeling, which further suggested that domains III and IV both participate in conformational changes leading to the functional switch between the Ca2+-dependent cross-linking activity and the Galpha activity.