Hepatocellul�re Glykogenose und Hepatombildung beim Menschen

Clear cell hepatocellular carcinoma: origin, metabolic traits and fate of glycogenotic clear and ground glass cells

Clear cell hepatocellular carcinoma (CCHCC) has hitherto been considered an uncommon, highly differentiated variant of hepatocellular carcinoma (HCC) with a relatively favorable prognosis. CCHCC is composed of mixtures of clear and/or acidophilic ground glass hepatocytes with excessive glycogen and/or fat and shares histology, clinical features and etiology with common HCCs. Studies in animal models of chemical, hormonal and viral hepatocarcinogenesis and observations in patients with chronic liver diseases prone to develop HCC have shown that the majority of HCCs are preceded by, or associated with, focal or diffuse excessive storage of glycogen (glycogenosis) which later may be replaced by fat (lipidosis/steatosis). In ground glass cells, the glycogenosis is accompanied by proliferation of the smooth endoplasmic reticulum, which is closely related to glycogen particles and frequently harbors the hepatitis B surface antigen (HBsAg). From the findings in animal models a sequence of changes has been established, commencing with preneoplastic glycogenotic liver lesions, often containing ground glass cells, and progressing to glycogen-poor neoplasms via various intermediate stages, including glycogenotic/lipidotic clear cell foci, clear cell hepatocellular adenomas (CCHCA) rich in glycogen and/or fat, and CCHCC. A similar process seems to take place in humans, with clear cells frequently persisting in CCHCC and steatohepatitic HCC, which presumably represent intermediate stages in the development rather than particular variants of HCC. During the progression of the preneoplastic lesions, the clear and ground glass cells transform into cells characteristic of common HCC. The sequential cellular changes are associated with metabolic aberrations, which start with an activation of the insulin signaling cascade resulting in pre-neoplastic hepatic glycogenosis. The molecular and metabolic changes underlying the glycogenosis/lipidosis are apparently responsible for the dramatic metabolic shift from gluconeogenesis to the pentose phosphate pathway and Warburg-type glycolysis, which provide precursors and energy for an ever increasing cell proliferation during progression.

Biological markers of preneoplastic foci and neoplastic nodules in rodent liver

Foci of altered hepatocytes are regularly observed early during hepatocarcinogenesis in rodents. The abnormal hepatocytes may show a number of different phenotypes as characterized by various cytomorphological and cytochemical markers. The first appearance and the further development of the abnormal cell populations depend on the dose of the carcinogen given and on the duration of the carcinogenic treatment. According to cytochemical, morphometric and autoradiographic findings in rats receiving low doses (2–10% of the LD 50/kg bw/day) of hepatocarcinogens for limited periods (“stop” experiments), glycogenotic (clear or acidophilic) hepatocytes indicate the first step of the neoplastic cell transformation which can be detected by these methods at present. The glycogenotic cells undergo a characteristic metamorphosis and give rise to basophilic tumor cells poor in glycogen, but rich in ribosomes. Under extreme experimental conditions, such as a single or repeated application of higher doses of one or several chemical carcinogens a puzzling picture emerges which is “reversible” to a large extent after withdrawal of the respective compounds. This observation points to a phenotypic instability of the cellular changes induced in certain experimental systems. Foci of altered hepatocytes persisting after withdrawal of the carcinogenic compounds are considered preneoplastic lesions. They may transform into neoplastic nodules which are also persistent and share a number of cytomorphological and cytochemical markers with the focal lesions. The persistent nodules progress to hepatocarcinomas after lag periods of weeks or months. However, the foci may also progress to hepatocarcinomas without passing a nodular intermediate stage. The development of both neoplastic nodules and carcinomas from the preneoplastic glycogen storage foci can proceed independent of further administration of carcinogen. The sequence of cellular changes during hepatocarcinogenesis derived from the experimental results in rodents is strongly supported by observations in humans, especially by the increasing reports on the appearance of hepatic tumors in patients who suffer from inborn hepatic glycogenosis.

Decrease in glucokinase and glucose-6-phosphatase and increase in hexokinase in putative preneoplastic lesions of rat liver

Preneoplastic liver lesions were produced in female Wistar rats by oral administration of 2-acetylaminofluorene for 165 days succeeded by a carcinogen-free standard diet up to 420 days. During the treatment numerous altered hepatic foci (AHF) and hyperplastic nodules (HN) were detected histochemically by a focal decrease or lack of adenosine-5-triphosphatase and glucose-6-phosphatase (G-6-Pase) activities. In addition, the immunohistochemically demonstrable amount of L-type pyruvate kinase was clearly reduced. The histochemically demonstrated decrease of G-6-Pase was substantiated by microbiochemical determination of the enzyme activity in microdissected material. Moreover, during the experimental period a continuous decrease in glucokinase and an increase in hexokinase was detected microbiochemically within AHF and HN. These alterations indicate a shift in the carbohydrate metabolism from gluconeogenesis to glucose utilization and pentose-phosphate-pathway for biosynthesis of nucleic acids. Beside other oncofetal markers, HK may be used as indicator of the early stages of liver carcinogenesis.

Effect of X-rays alone or combined with diethylnitrosamine on cancer induction in mouse liver

The possible combined effects of the initiator diethylnitrosamine (DEN) with X-rays on cancer induction in infant C57BL/Cnb mice were evaluated. Preliminary data show that a dose of X-rays administered 7 days before a single injection of DEN was more effective in inducing liver nodules than when administered 7 days after DEN administration.

Histochemical and immunohistochemical detection of putative preneoplastic liver foci in women after long-term use of oral contraceptives

Localized areas with altered enzyme patterns were observed in liver tissue surrounding focal nodular hyperplasia in women after long-term use of oral contraceptives. These localized lesions were of three different types. Type I lesions were characterized by glycogen storage, a reduction in ATPase and an increase in gamma-glutamyltranspeptidase (gamma-GT) and UDP-glucuronyltransferase (UDP-GT) detected immunohistochemically. Type II lesions, which were morphologically very similar to small hyperplastic nodules, showed only a decreased ATPase reaction. Type III lesions showed an increase in gamma-GT (detected histochemically) and a slight reduction in ATPase. The results indicated that in human liver from patients given oral contraceptives long-term, localized lesions with altered enzyme patterns may occur which are very similar to those observed in animal models during experimental hepatic carcinogenesis.

Hepatocellular glycogenosis and related pattern of enzymatic changes during hepatocarcinogenesis

Systematic studies of the sequence of cellular changes during hepatocarcinogenesis induced predominantly in rats by stop experiments with N-nitrosomorpholine (NNM) led to the following main results and conclusions: The development of hepatocellular tumors is preceded by a multifocal hepatic glycogen storage disease (glycogenosis). Cytomorphological and cytochemical findings suggest a sequence of focal changes leading from clear and acidophilic glycogen storage foci through mixed cell foci and neoplastic nodules to hepatocellular carcinomas. The clear and acidophilic glycogen storage cells persisting after withdrawal of the carcinogen apparently represent a preneoplastic cell population, the neoplastic transformation of which is accompanied by a gradual reduction of glycogen and a concomitant increase in ribosomes (basophilia). The first appearance and frequency of the different liver lesions investigated was shown to depend on the dose of carcinogen administered. With increasing dose of NNM, the number of focal lesions considerably increased, and this was accompanied by an earlier development of mixed and basophilic cell populations. There was no indication of any reversibility of pronounced focal lesions under the experimental conditions chosen. On the contrary, the foci became larger and acquired phenotypic markers closer to neoplasia independent of further action of the carcinogen. Enzyme histochemically, the majority of the pronounced glycogen storage foci showed a reduction in the activities of glycogen phosphorylase and glucose-6-phosphatase while the activity of glucose-6-phosphate dehydrogenase, a key enzyme for the pentose phosphate pathway, was increased. The mixed cell foci, neoplastic nodules and carcinomas which emerged at later stages were characterized by a progressive shift away from glycogen metabolism towards glycolysis and the pentose phosphate pathway. as indicated by an increase in glyceraldehyde-3-phosphate dehydrogenase and glucose-6-phosphate dehydrogenase activities. These changes in enzyme pattern are in keeping with a developmental sequence leading from glycogen storage foci through mixed cell foci and neoplastic nodules to hepatocellular carcinomas. Biochemical microanalysis of dissected glycogen storage foci and mixed cell foci revealed that the foci composed exclusively of storage cells contained on an average 100% more glycogen than the normal liver tissue. The overall glycogen content of the mixed cell foci, which were composed of both glycogenotic and glycogen-poor basophilic cells, was not distinguishable from that of normal tissue.(ABSTRACT TRUNCATED AT 400 WORDS)

Type 1 glycogenosis with contracted kidneys and liver cell adenoma

A 22-year-old man with type 1 glycogenosis died of renal and respiratory failure. Postmortem examination revealed deposition of glycogen in liver cells, a liver cell adenoma, bilateral contracted kidneys with scent glycogen deposition, and pulmonary edema. The development of liver cell adenoma was thought to be related to underlying metabolic disorder and contracted kidneys were considered to be the sequel of massive glycogen deposition in the renal tubular epithelium.

Electron microscopic study of benign hepatoma in a patient on oral contraceptives

Electron microscopic studies of a benign hepatoma in a 31-year-old women who was on contraceptive pills are presented. The electron microscopic picture showed highly differentiated liver cells with regularly developed bile canaliculi. The mitochondrial polymorphism, the formation of paracristalloids and the appearance of giant mitochondria were striking. The main change was the occurence of the numerous capillaries of varying caliber which were highly differentiated and formed an integral part of the tumor. On the basis of these finding the tumor is regarded as a benign mixed tumor. The well developed capillary system explaines the arteriographic characteristics and the frequent bleeding complications noted in the literature.