Early Neoplastic Proliferations Research Articles

Galectin-3 in preneoplastic lesions of glioma

Gliomas are the most common primary brain tumors in adults and have a poor prognosis. Galectin-3 is a β-galactosidase-binding lectin which is important in pre-mRNA splicing, regulation of cell proliferation, cell adhesion and apoptosis. Although galectin-3 has been shown as a glioma related marker and expression of galectin-3 has been reported to correlate with WHO grade in human gliomas, expression of galectin-3 in early neoplastic lesions such as early neoplastic proliferation (ENP) and microtumor is still far from fully understood. In the present study, expression of galectin-3 in ethylnitrosourea-induced rat gliomas including preneoplastic and neoplastic lesions was examined by immunohistochemistry for galectin-3, Iba-1 (a specific microglial cell marker), GFAP (a specific astrocyte cell marker), and conventional hematoxylin and eosin staining (for morphological observation). The results showed that exact location of ENP was detected clearly by galectin-3 immunohistochemistry whereas normal brain tissues were negative. In ENP and microtumor, galectin-3 was expressed in neoplastic astrocytic cells but rarely in microglia. In malignant glioma, however, galectin-3 was expressed in both neoplastic astrocytic cells and microglia. This suggests that galectin-3 is activated in microglia and macrophages according to the progression of glioma. Galectin-3 was not expressed in oligodendrocytic cells. Our results indicate that galectin-3 is a good specific marker indicating the early stage of glioma tumorigenesis.

A sequential ultrastructural and histoautoradiographic study of early neoplastic lesions in ethylnitrosourea-induced rat glioma.

A sequential study of the early stage of development of ethylnitrosourea (ENU)-induced glioma in the rat was performed by electron microscopy and [3H]thymidine histoautoradiography. Hyperplasia, the earliest neoplastic change that was detectable morphologically, consisted of a few or several immature oligodendroglia-like cells which were connected with one another or with preexisting neural tissue by junctional apparatus, and showed no reactive changes in the astrocytes or microglia. The labelling index of hyperplastic cells was 2.6%. Foci of early neoplastic proliferation (ENP) showed mild destructive changes in the neighboring neural tissue, and their major constituent cells had characteristics of immature oligodendroglias. The labelling index of cells showing ENP was 3.3%. The intercellular spaces exhibited slight enlargement with accumulation of extracellular matrix and a decrease in the number of junctional apparatus on the neoplastic cells. Microtumors showed apparent destruction of the preexisting neural tissue to form a tumor mass with an increase in the extracellular matrix. Constituent cells of the microtumors were similar to those of the ENP, although reactive astrocytes and microglias occurred more frequently. The labelling index was 9.6% in the central area of microtumors and 5.3% in the peripheral area. These findings suggest that in the initial or very early stages of glial cell neoplastic proliferation, it is necessary for the neoplastic cells to maintain contact with the neurons for metabolic purposes, and that after losing contact, these cells can proliferate autonomously with the accumulation of extracellular matrix.

Nerve growth factor modification of the ethylnitrosourea model for multiple schwannomas.

The administration of ethylnitrosourea (ENU) to pregnant rats late in gestation or to neonatal rats results in the induction of Schwann cell tumors in a high percentage of perinatally exposed animals. Exogenous administration of nerve growth factor (NGF) significantly reduces the number of Schwann cell tumors and other neurogenic tumors developing in ENU-treated rats. Administration of antibodies directed against NGF prior to neonatal ENU exposure results in a substantial increase in the incidence of Schwann cell tumors, particularly in the trigeminal nerves of both rats and mice. Transplacental ENU treatment causes early neoplastic proliferation (ENP) at 90 days of age in the Schwann cell population of trigeminal nerves in nearly all exposed rats. A variety of NGF treatment protocols (single or multiple inoculations or microinfusion prior to or following ENU exposure) resulted in a significant reduction in ENU-induced ENP in trigeminal nerves. These results indicate that NGF may convey protection either directly or indirectly, by an unknown mechanism, to Schwann cells and other supportive neural cells by reducing their sensitivity to ENU-induced neoplastic transformation.

The effect of nerve growth factor and antibodies to nerve growth factor on ethylnitrosourea-induced neoplastic proliferation in rat trigeminal nerves.

Sprague-Dawley (CD) rats were injected intravenously with ethylnitrosourea at a dose of 20 mg/kg on day 20 of gestation. This exposure resulted in early neoplastic proliferation or development of a neurinoma of the trigeminal nerve in 58% of the offspring at 90 days of age. Implantation of osmotic microinfusion pumps containing 2.5S nerve growth factor prior to ethylnitrosourea administration significantly reduced the incidence of early neoplastic proliferation. Postnatal implantation of microinfusion pumps containing 2.5S nerve growth factor also resulted in a significant but less pronounced reduction of early neoplastic proliferation. Immunoglobulin G directed against nerve growth factor (anti-nerve growth factor) did not influence the incidence of early neoplastic proliferation when administered via microinfusion pumps implanted on day 15 postnatally. These findings suggest that nerve growth factor has a protective effect on the developing nervous system against ethylnitrosourea-induced carcinogenesis.

Glial fibrillary acidic protein (GFAP) in rat brain tumors transplacentally induced by ethylnitrosourea (ENU)

The immunohistochemical distribution of glial fibrillary acidic protein (GFAP) in neoplastic lesions induced in the rat by ENU is reported. GFAP was present in hypertrophic reactive astrocytes, which were numerous in early neoplastic proliferations, in microtumors of the white matter, and in those collected at the periphery of large tumors. They were absent in cortical oligodendroglial foci and microtumors. No GFAP-positive cells were observed in hyperplasias of the white matter: astrocyte-like cells of large tumors were GFAP-negative. The significance of reactive astrocytes and the problem of the astrocytic component in transplacental ENU tumors are discussed.

Early stage of development of transplacentally induced glioma with ethylnitrosourea in rats. Sequential historadioautographic and electron microscopic studies.

Proliferative activity of possible preneoplastic cells (subependymal cells and glioblasts), early neoplastic cells and glioma cells induced by transplacental ethylnitrosourea (ENU) treatment in the rat was analysed by historadioautography and electron microscopy. Labeling index of 3H-thymidine in subependymal cells was the highest in the cerebrum of postnatal age, but no difference was observed between the normal and ENU treated groups. Thus, preneoplastic cells could not be distinguished from normal cells by morphology and proliferative activity. Focus of early neoplastic proliferation was composed of rather heterogenous and less differentiated cells, such as oligodendroblast-, glioblast- and subependymal cell-like cells, and preferentially located around the periventricular areas. Labeling index of early neoplastic proliferation was very low although the value gradually increased with age. Proliferative activity of glioma cells was higher than that of the early neoplastic cells and lower than subependymal cells, and further differed according to the degree of differentiation and morphological type. Finally, it is suggested that glioma might develop mainly through the differentiation from the focus of early neoplastic proliferation.

Cyclic nucleotides in experimental and human brain tumors.

It is well known that the system of cyclic nucleotides plays an important role in cell differentiation and proliferation. Cyclic AMP is capable of stimulating cell growth, and cyclic GMP is thought to control cell division and growth. The authors measured adenylcyclase activity (AC) and cGMP content in the tumor latency period and in early neoplastic proliferations in rats with brain tumors induced by transplacental ethylnitrosourea (ENU). AC activity, which is high during the first days of life, decreases until it reaches, at the 60th day, levels lower than those in control animals. Cyclic GMP, on the contrary, increases during the first month in treated animals and remains consistently higher than controls up to the 45th day. In fully developed experimental brain tumors (mixed gliomas, isomorphic and polymorphic oligodendrogliomas) the percentage of reduction in AC activity is significantly higher. AC activity was measured also in human tumoral tissue. In malignant tumors it is markedly lower than in benign tumors. In the same patients cAMP in the cerebrospinal fluid was measured with results similar to those obtained in tissues. These findings confirm that the system of cyclic nucleotides is implicated in all the developmental phases of brain tumors and therefore may reveal how research can clarify the first transformations of tumoral cells.

Biochemical and histochemical evaluation of glycosaminoglycans in brain tumors induced in rats by nitrosourea derivatives.

The occurrence, distribution and concentration of GAGs in ENU and MNU experimental brain tumors induced in the rat are reported. GAGs have been histochemically studied by Alcian Blue methods; they have been quantified and qualitatively evaluated by electrophoresis of brain extracts. The pattern of GAGs in normal rats is consistent with the data of the literature. No GAG accumulation precedes the tumor development. Early neoplastic proliferations, oligodendroglial and mixed glial microtumors are strongly alcian-positive; the alcianophilia spares clusters of cells developing a cytoplasm. In large tumors, GAGs are histochemically demonstrable in the honey-comb areas of oligodendrogliomas and in peripheral infiltration areas of polymorphic gliomas. The role of the normal nervous tissue and oligodendroglial cells in the accumulation of the GAGs is discussed. The accumulated GAGs seem to rise from the nervous tissue included in the tumors, rather than from the metabolism of tumor cells.

Glycosaminoglycans of brain tumors transplacentally induced by ENU in the rat.

GAGs accumulate in the oligodendrogliomas and in the oligodendroglial component of mixed gliomas induced in rats by transplacental ENU. We studied the period between birth and the appearance of the earliest tumoral lesions and did not find any accumulation preceding the early neoplastic proliferations. These findings, together with the observation that GAGs are present only in the oligodendroglial component of tumors, are in agreement with our previous interpretation that the tumoral transformation of oligodendroglia takes place after it has acquired the ability to interfere with GAG metabolism during myelinogenesis.

Experimental brain tumors by transplacental ENU. Multifactorial study of the latency period.

Experimental cerebral tumors have been induced by transplacental ENU. The morphologic study of the brains of treated rats revealed that cellular hyperplasias appear at the 30th day of extrauterine life in the paraventricular white matter, i.e., before the already known "early neoplastic proliferations". Cytofluorimetric investigations failed to demonstrate differences between treated and control rats during the 1st month. On the contrary, adenylate cyclase activity is very high in that period. The duration of the latency period is discussed.

Cerebral tumours induced by ENU; changes of adenylate cyclase activity in the tumour latency time.

Tumours of the nervous system have been induced by transplacental ENU. Until the fourth month of life the tumoural lesions appear as mixed glial proliferations or oligodendroglial foci. From the fourth month on they develop as glial micro- and macrotumours or as isomorphic and polymorphic oligodendrogliomas. The adenylate cyclase activity studied during these two distinct phases of tumour development was markedly reduced in brain tumours, independent of their cellular origin, compared with the level in the normal brain. On the other hand, the activity of the enzyme responsible for the synthesis of cyclic AMP is significantly increased during the first period of tumour development when early neoplastic proliferations are present.