Models and concepts derived from human teratogenesis and oncogenesis in early life.

Several basic empirical facts are emphasized about human developmental oncology. The first is that teratogenesis and oncogenesis are intimately related and that indeed teratogenesis may be the more primitive reaction to the types of mutagenic injury giving rise to neoplasm. The second is that neoplasms of early life, particularly those initiated "in utero" are rare, and tend to spontaneously regress or cytodifferentiate. The theoretical models of carcinogenesis forwarded by Knudson and Matsunaga are enlisted in attempts to explain these phenomena and how the oncogene is expressed and modulated by the fetal or embryonal milieu.

Genetic models of carcinogenesis.

The major genetic models of carcinogenesis are critically reviewed to determine their validity and relevance for clinical and experimental oncologists. Of major concern are the "two-hit" theory of Knudson and the host resistance system of Matsunaga. These models may be used to explain the pathobiologic peculiarities of human neoplasms, particularly those occurring in early life. It is proposed that certain benign and regressive tumors encountered in early life are expressions of the activity of the host resistance system.

Thymic involution mimicking thymic dysplasia: a consequence of transfusion-induced graft versus host disease in a premature infant.

A premature infant with ostensibly normal immunologic function received two exchange blood transfusions for hyperbilirubinemia and several blood and platelet transfusions for pancytopenia. A fatal graft vs host reaction (GvHR) ensued that was diagnosed by skin biopsy one day prior to death at age 40 days. Autopsy revealed characteristic alterations of GvHR in the spleen, lymph nodes, gut, and liver. In addition the thymus was small (3.5 g), lymphoid-depleted, lacked corticomedullary demarcation and Hassall's corpuscles, and demonstrated lymphocyte invasion and injury of epithelial cells. The thymic cytomorphology acquired added meaning when it was discovered that a chest roentgenogram obtained at one day of age demonstrated a normal thymic shadow. It is concluded that the GvHR induced a direct injury to the thymic epithelium, resulting in an acquired form of thymic dysplasia. The theoretical implications of this observation are considered.

Neoplasia of early life and its relationships to teratogenesis.

The biologic peculiarities of tumors of early life are elucidated. The oncogenic grace period is emphasized, wherein infantile tumors tend to behave in a relatively benign fashion up until 3-6 months of age. A review of the types of congenital malformations associated with the development of neoplasms is presented. These associations appear to be of fundamental importance in developmental pathobiology. They are illustrated by the tendency for neoplasms to develop in anomalous or dysplastic tissues, such as developmental vestiges, undescended testes, dysgenic gonads and certain hamartoses. There is an increased incidence of tumor occurrence in: (1) specific teratologic disorders: aniridia, hemihypertrophy, Beckwith's syndrome, basal cell nevus syndromes and others; (2) cytogenetic abnormalities: Down's syndrome, 13q- syndrome (D-deletion), trisomy 18; (3) chromosomal instability syndromes: Fanconi's anemia, ataxia-telangiectasia, Bloom's syndrome. Finally, many agents, known to be carcinogenic when administered postnatally to animals, are teratogenic in the fetus. A few agents--urethan, alkylnitrosoureas, estrogens--are both teratogenic and carcinogenic when administered to the fetus transplacentally. It is suggested that the timing of intrauterine insult is important in determining whether the effect on the offspring is teratogenic, oncogenic or both. Teratogenesis appears to be the more primitive response. Other theories explaining the concurrence of tumors and anomalies are offered.

Spontaneous regression of neuroblastoma: an experimental approach.

The cytolytic activity of normal pregnancy serum was first studied on murine cancer cells and shown to be the result of a natural IgM antibody that binds to cell surfaces and activates complement. Both the classical and alternative pathways of complement are involved. It was then shown that certain human neuroblastoma cell lines, to the exclusion of other human cancers, react to the same system. It is proposed that this system may play a role in the cytolytic form of spontaneous regression of neuroblastoma.

Neurocristopathy: its growth and development in 20 years.

The neurocristopathies, originally defined in 1974 as a category of diseases arising in neural crest development are reviewed as to their current status. Accompanying the great advances in neural crest ontogeny, there has been an increase in the number and variety of neurocristopathies, particularly in the definition of craniofacial syndromes derived from the cranial crest mesectoderm. Molecular biology and genetics have added new dimensions in defining interrelationships between a number of entities. Environmental teratogens that cause neurocristopathies are also discussed. Neurocristopathy as a pathogenetic concept should continue to be useful as a structural framework for future investigations.

Ultrastructural and histochemical studies of murine megacolon.

The myenteric plexus of the colon was studied ultrastructurally in a colony of an Ls Ls strain of mice manifesting a piebald coat color mutation associated with a high incidence of genetically determined aganglionic megacolon. Ultrastructural studies were histochemically supplemented by the Maillet technic and stains for acetylcholinesterase and catecholamines. The development of megacolon did not appear to require total aganglionosis, since ostensibly aganglionic areas contained rare ganglion cells. In the distal narrowed segment, both cholinergic and adrenergic fibers in the muscularis, submucosa and mucosa were somewhat reduced. In the mouse, the dilated portion showed an abrupt increase in adrenergic fibers. These findings are related to the pathophysiology of the disorder. The increasing degenerative changes seen in myenteric plexus structures from the fetus to adult suggest that aganglionic megacolon may be an abiotrophy, wherein the congenitally deficient myenteric plexus may be unusually predisposed to postnatal injury and degeneration.

The cytolysis of human neuroblastoma cells by a natural IgM 'antibody'-complement system in pregnancy serum.

Cell lines from 26 human cancers were studied for cytotoxicity when treated with normal pregnancy serum. Cytotoxicity manifested by cell death and cytolysis, occurred in 4 of 8 neuroblastomas studied: SK-N-SH, NGP, LAN-5, and IMR-32. In NGP and SK-N-SH, evidence is presented showing that the cytotoxicity resulted from the cell-surface binding of a natural IgM 'antibody', which sensitized the neuroblastoma cells to the lytic action of complement (C). This system may be involved in a cytolytic form of spontaneous regression of neuroblastoma.

Isolation of a natural cytotoxic IgM "antibody" in human serum sensitizing L cells to complement.

An IgM fraction of human serum was isolated and purified. A portion of this fraction firmly attaches to L cells' surfaces, which sensitizes these cells to the lytic action of low concentrations of serum C. It contains the natural cytotoxic "antibody" to L cells.

Experimental studies on the hemolytic-uremic syndrome.

Ultrastructural studies of blood cells during the acute stage of the hemolytic-uremic syndrome (HUS) revealed striking, but transient, changes in erythrocyte structure. These included membrane disruption, vacuolar degeneration, and Heinz body formation. There was also evidence of platelet injury, and there were peculiar tactile interactions between histiocytes and impaired red cells. These changes disappeared as the patients recovered. These changes were considered to be important in the pathogenesis of the hemolytic and thrombolytic features of HUS, and studies were directed at reproducing them in vitro and in vivo. Treatment of red cells with purified clostridial phospholipase C induced changes in red cells and platelets that were comparable to those encountered in HUS. Rats infused with phospholipase C developed hemolysis, thrombocytopenia, and hemoglobinuria. Their kidneys did not, however, reveal glomerular alterations similar to those seen in patients with HUS. It is proposed that HUS in some cases might be initiated by a nonspecific infectious injury to the intestinal mucosa thereby allowing increased absorption of toxins derived from indigenous gut flora and that these toxins could be responsible for the hemolysis, thrombolysis, and even the renal injury.

Natural cytotoxicity of human serum. A natural IgM 'antibody' sensitizes transformed murine cells to the lytic action of complement.

The natural cytotoxicity of human serum on murine L cells, EA and Sa 180 cells is expressed as a rapid cytolysis at 37 degrees C. This cytotoxic system is analyzed as to its active constituents and their functional relationships. Ultrastructural studies indicate that cell injury and death are initiated within 10 min by membrane disruption. A trypan blue assay for cell death was used to study serum toxicity in individual normal healthy adults, pregnant females and newborn infants. Pregnancy sera, particularly in the 2nd and 3rd trimesters, were consistently more toxic than male serum or nonpregnant females. Cord serum was typically nontoxic. Pools of normal fresh pregnancy serum were used for immunochemical analysis of the cytotoxic activity. By a variety of immunologic and immunochemical techniques it was shown that the cytotoxicity was, in part, due to the combined action of alternative and classical pathways of complement, the former being more prominent. The lytic action of complement was shown to be greatly amplified by the prior adsorption of IgM on the target cells' surface. This IgM is a critical determinant of the cytotoxic reaction. It probably contains a natural 'antibody' to cell surface antigen(s), whose combination activates both pathways of C.

Thymic epithelial injury in graft-versus-host reactions following adrenalectomy.

In four separate experiments 140 adults A(H-2a) x C57BL/6(H-2b) F1hybrid mice were surgically adrenalectomized and divided into three experimental groups. Seventy-one additional adult F1hybrids (AXC57BL/6) which had not been adrenalectomized were divided into three similar groups. In Group 1 (GvH group), GvH reactions were induced by the injection of 50 x 106 pooled parental lymphoid cells intravenously. The second group (syngeneic group) received 50 x 106 pooled F1 hybrid lymphoid cells intravenously. The third group (uninoculated group) received no lymphoid inoculum. At regular intervals the animals were killed, autopsied, and histologically studied. Visceral alterations of GvH reaction were recorded in the thymus, lymph nodes, spleen, and liver in the GvH groups; none was present in the other groups. The thymuses in the nonadrenalectomized GvH group underwent prompt involution characterized by size reduction and cortical lymphoid cell depletion. These changes were not apparent in the GvH adrenalectomized group. Both GvH groups, however, demonstrated an effacement of the medulla, lymphocyte incursion into the medulla, lymphocyte emperipolesis of medullary epithelial cells, gradual disappearance of Hassall's corpuscles, epithelial cell injury, and an ingress of macrophages laden with nuclear and cellular debris. This study suggests that the stress and corticosteroid response which accompany a GvH reaction account for the reduction in the thymic size and cortical lymphoid cell mass. The medullary alterations, therefore, would appear to be initiated by the GvH reaction per se.

Thymic involution in murine graft-versus-host reaction. Epithelial injury mimicking human thymic dysplasia.

Mild, moderate, and severe graft-versus-host (GVH) reactions were induced in four series of experiments in 71 CBA X A and C57BL/6 X A F1 hybrid mice. At regular intervals post-GVH reaction induction (Days 4-42), the animals were sacrificed, autopsied, and histologically studied. Visceral alterations of GVH reaction were recorded in the spleen, lymph nodes, liver, kidney, gut, and thymus. A spectrum of thymic changes was documented, ranging from obliteration of a definable cortex and medulla with loss of Hassall's corpuscles to marked involution with complete disappearance of the gland. Ultrastructural studies revealed damage to both lymphocytes and epithelial cells along with lymphocyte emperipolesis of epithelial cells, lymphocytolysis within epithelial cells, and accumulation of numerous autophagic vacuoles containing fragments of cellular debris within epithelial cells and histiocytes. The resemblance of these alterations to human thymic dysplasia as observed in primary immunodeficient conditions was striking. The theoretical implications of these studies for the pathogenesis of human congenital immunodeficiency states are considered.