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Objective: interlukin 12 (IL-12) is a cytokine that may enhance the proliferation and cytotoxic activity of T lymphocytes and natural killer (NK) cells. A relationship between extensive intratumoral infiltration of NK cells and longer survival rates in colorectal cancer (CRC) patients was previously noted. Preliminary evidence suggests that the combined administration of IL-12 and IL-2 may produce additive immunomodulatory activity. The purpose of this study was to determine whether the systemic administration of IL-12 (+/- IL-2) may induce an immune response against CRC as induced by 1,2-dimethylhydrazine (DMH). Methods: sixty-five 6-week-old Wistar rats were treated with weekly subcutaneous injections of DMH for 26 weeks at a dose of 20 mg/kg of body weight. Once tumoral induction was over, the animals were randomly allocated to one of three groups: I, control; II, intraperitoneal injections of IL-12; III, intraperitoneal injections of IL-12 combined with IL-2. At 30 weeks, all surviving animals were sacrificed. We studied the following parameters in each rat - number of tumors, size of tumors, and total tumoral volume.Tumor samples were studied using the monoclonal antibody CD 57 for the detection of NK cells. The extent of NK infiltration was classified as small, less than 50 NK cells/50 high-power field (HPF); moderate, 50 to 150 NK cells/50 HPF, and extensive, more than 150 NK cells/50 HPF. Results: thirty-five rats died before completion of the carcinogen exposure, and 30 rats were randomized (10 each group). In group II, 2 animals died during treatment. All rats in groups I and III developed tumors, while in group II two rats (25%) were tumor-free. Moreover, only one rat in group II developed multiple neoplasms, in contrast with group I and group III, where six rats (60%) and seven rats (70%), respectively, had more than one tumor. We found statistically significant differences in the mean number of tumors found in group II when compared to group I (p=0.028) and group III (p = 0.019). Other parameters measured, such as biggest tumor size and total tumoral volume were found to be lower in group II, although no statistical differences were found between groups. Only 10% of rats in group I showed moderated/extensive NK cell infiltration, vs. 60% of rats in group II (p = 0.077) and 70% in group III (p = 0.02). Conclusion: The administration of DMH to rodents provides a reliable and consistent means of inducing CRC that may be suitable for the evaluation of anti-cancer therapies. Our findings suggest that IL-12 is effective against the development of experimental CRC. Its antineoplastic effect could be attributed to the stimulus of this cytokine on the intratumoral infiltration of NK cells. Objetivo: la interleucina (IL-12) es una citocina que estimula la proliferación y la actividad citotóxica de los linfocito T y las células natural killer (NK). En trabajos previos se ha observado una relación entre la infiltración intratumoral de células NK y una mayor supervivencia en carcinomas colorrectales (CCR). Existen evidencias de un efecto aditivo en la actividad inmunomoduladora de la asociación de IL-12 con IL-2. Así, nos hemos propuesto el estudio de la capacidad de respuesta inmune antitumoral, tras la administración sistémica de IL-12 sola o combinada con IL-2, en un modelo experimental de CCR inducidos mediante la administración de 1,2-dimetilhidracina (DMH). Método: sesenta y cinco ratas Wistar de 6 semanas a las que se administró en inyección subcutánea una dosis semanal de DMH a razón de 20 mg/kg de peso durante 26 semanas. Finalizado el periodo de inducción, los animales se distribuyeron aleatoriamente en tres grupos. I: grupo control. Grupo II, se administró IL-12 recombinante murina. Grupo III: se administró IL-12, combinada con IL-2. Las ratas se sacrificaron en la semana 30, estudiándose los siguientes parámetros: número y localización de tumores, tamaño y carga tumoral. Se realizó inmunotinción para células NK con anticuerpo monoclonal CD 57. Se establecieron tres grupos según la cuantía del infiltrado: leve, menos 50 células/50 campos de gran aumento (CGA), moderado, entre 50 y 150/células/50 CGA y elevado, más de 150 células/50 CGA. Resultados: durante la inducción tumoral fallecieron 35 ratas. Las 30 restantes fueron distribuidas aleatoriamente en 3 grupos de 10. Durante las 2 semanas de tratamiento fallecieron 2 ratas, del grupo II. Todas las ratas de los grupos I y III desarrollaron CCR. En el grupo II, dos animales (25%) no desarrollaron tumor. Sólo una rata del grupo II desarrolló neoplasias múltiples en contraste con el grupo I en el que esto ocurrió en 6 ratas (60%) y siete (70%) en el grupo III. Se hallaron diferencias estadísticamente significativas en el número de tumores desarrollados entre el grupo II respecto al I (p = 0,028) y al grupo III (p = 0,019). El mayor tamaño tumoral o el volumen tumoral total fueron menores en el grupo II pero no se obtuvieron diferencias estadísticamente significativas con los restantes grupos. Un 10% de las ratas del grupo I presentó moderada o extensa infiltración, frente al 60% del grupo II (p = 0,077) y al 70% del grupo III (p = 0,02). Entre los grupos II y III no se encontró ninguna diferencia estadística (p = 1). Conclusión: El modelo usado de inducción tumoral es un modelo útil para el estudio de la eficacia de distintos tratamientos antitumorales. Pensamos que la IL-12 tiene un efecto antineoplásico frente al desarrollo de tumores experimentales, lo que puede ser atribuido, al menos en parte, al estímulo ejercido por esta citocina sobre los infiltrados intratumorales de células NK.

Four ethyl-nitrosourea (ENU)-induced oligodendroglioma-like tumors of the rat showing large rosettes on haematoxylin-eosin stain were studied by means of immunohistochemistry and electron microscopy, and their features compared with six human intraventricular neurocytomas. The similarities between the experimental and human tumors studied support the hypothesis that most of the so-called ENU-induced oligodendrogliomas in the rat are primitive neuroectodermal tumors with the tendency to differentiate toward a neuronal phenotype, and also suggest that the ENU-model of neurocarcinogenesis is useful for the induction of experimental neurocytomas.

The presence of IOT-10-positive lymphocytes among the tumor-infiltrating-lymphocyte (TIL) population was studied in a series of 185 brain tumors. In most of the tumors, IOT-10-positive lymphocytes were identified, but generally they were scarce and masked among the tumor cells, suggesting that NK-cells exercise a poor participation in the tissular response against brain tumors. Isolated tumor cells showing IOT- 10-positivity were found in low-grade astrocytomas, neurinomas and medulloblastomas. IOT- 10-positivity on both tumor neuropil and tumor cells was considered a characteristic finding in oligodendrogliomas. The number of IOT- 10-positive NK-cells in brain metastases and in cerebellar hemangioblastomas was comparatively greater than in other types of brain tumor. Since in brain metastases, the presence of IOT-10-positive NK-cells can be related to the tissular response to an extracerebral malignancy, their considerable presence in cerebellar hemangioblastomas is an enigmatic finding that desemes further attention.

We present the irnmunohistochernical study of 11 cases of intracranial cysts: two extraventricular ependymal cysts, three colloid cysts of the third ventricle, four extraventricular choroidal cysts and two Rathke's cleft cysts. Antibodies against glial fibrillary acidic protein (GFAP), cytokeratins (AE1, CKSD, AE3), S-100 protein, epithelial membrane antigen (EMA), vimentin, neuron specific enolase (NSE), neurofilaments protein (NF) and prealbumin, were used. The epithelium of choroidal cysts, showed strong immunoreactivity for Prealbumin and cytokeratins, similar to the normal choroid plexus epithelium. The ependymal cysts showed epithelial immunoreactivity for GFAP and S-100, both glial markers expressed by the normal ependymal epithelium. On the contrary, the epithelial wall of colloid cysts and Rathke's cleft cyst, expressed epithelial markers (cytokeratins and EMA) but no neuroepithelial markers, with a immuno-phenotype similar to that of other cysts of endodermal nature. This finding supports the neuroepithelial origin for choroid and ependymal cysts, and an endodermal nature for colloid and Rathke's cleft cysts. We conclude that these immunohistochernical markers are useful in the differential diagnosis of intracranial cysts

Synaptophysin expression was studied in seven "ependymomas" induced by transplacental administration of ethyl-nitrosourea in rats. In all the cases, strong positivity for synaptophysin was found on tumor cells. This finding supports previous studies suggesting that ENU-induced brain tumors considered to be ependymal neoplasms, are, in fact, primitive neuroectodermal tumors.

A series of 18 tumors with histological features of oligodendrogliomas, induced in the rat by means of transplacental ethyl-nitrosurea administration were studied for immunohistochemical demonstration of neuronal (synaptophysin and neurofilament protein) and glial (gliofibrillar acidic protein and vimentin) markers. Most of the tumors showed cells with strong positivity to synaptophysin and to a lesser degree, to neurofilament protein, suggesting the neuronal character of these neoplasms. In 10 tumors, cells with strong positivity to vimentin were found, and in three cases, tumoral cells expressed gliofibrillar acidic protein. The observation that ENU-induced oligodendroglial tumors express neuronal and, to a minor degree, glial markers, suggests their interpretation as prirnitive neuroectodermal tumors with clear neuronal differentiation.