A classification of tumor development based on an analysis of enzymes in tissue sections of hypernephroid carcinoma in man

von Hippel-Lindau gene mutations in N-nitrosodimethylamine-induced rat renal epithelial tumors

BACKGROUND

Mutations in the von Hippel-Lindau (VHL) gene are common in human clear cell kidney cancers. Carcinogens in cigarette smoke, especially nitrosamines, are known to induce kidney tumors of a variety of histologic types in rodents--but with no evidence of VHL mutations; however, none of these tumors resembled human clear cell carcinomas. We examined N-nitrosodimethylamine-induced kidney tumors of the clear or mixed clear/granular cell type in Wistar rats to assess the presence of VHL mutations.

METHODS

Sections of eight clear or mixed clear/granular cell kidney tumors that had been formalin fixed and paraffin embedded were microdissected. DNA was extracted from the microdissected tissue, and exons 1-3 of the rat VHL gene were examined by use of polymerase chain reaction and cycle sequencing techniques.

RESULTS

Four VHL gene mutations (three G:C to A:T and one A:T to G:C) were detected in three of the tumors in contrast to no mutations in 40 previously reported rat kidney tumors of other histologic types (three of eight tumors versus none of 40; two-sided Fisher's exact test; P=.003). Only tumors showing prominent swollen clear cell cytology with a signet-ring appearance had VHL mutations.

CONCLUSIONS

To our knowledge, this is the first report of VHL mutations in kidney tumors after direct chemical exposure and provides a possible molecular pathway linking tobacco smoking to kidney cancer.

Elevated concentrations of gamma-enolase in renal cell tumors in rats: similarity to renal cell carcinoma in man

Concentrations of enolase isozymes in normal kidney and renal cell tumors in rats were determined using a highly sensitive enzyme immunoassay, and the isozymes were immunohistochemically localized in tissue sections. Levels of alpha-enolase in renal cell tumors were significantly lower than in normal kidney, whereas those of gamma-enolase were significantly elevated (mean +/- SD: 211 +/- 129 ng/mg protein, n = 15, as compared to 27.1 +/- 2.9 ng/mg protein, n = 7). The proportion of gamma-enolase in the total enolases in the tumor tissues (1.6 +/- 0.5%) was significantly higher than in normal kidney (0.15 +/- 0.05%). Immunohistochemistry revealed epithelial cells of all nephron segments to be positive for the alpha-isozyme, whereas gamma-enolase staining was strongly positive only in the loops of Henle, being faint in the distal tubules and absent in the proximal tubules. Both alpha- and gamma-enolases demonstrated positive immunostaining in all of the seven renal cell tumors studied. These findings indicate that an isozyme switch from alpha- to gamma-enolase occurs during rat kidney carcinogenesis, taking into account the derivation from proximal tubules, consistent with the findings for renal cell carcinomas in man.

Elevated levels of serum aldolase A in patients with renal cell carcinoma

To clarify whether serum aldolase A is a useful biomarker for renal cell carcinoma (RCC), we determined serum levels of the aldolase A isozyme by an enzyme immunoassay in patients suffering from RCC, other urological tumors, and benign urological diseases. Forty-six of 126 patients with RCC (37%) had elevated serum aldolase A. The positive rates were 23% in stage I, 40% in stage II, 63% in stage III, and 46% in stage IV. In 10 (83%) of 12 patients whose serum levels had been elevated preoperatively, these were reduced to within the normal range after nephrectomy. Four of 7 patients (57%) with progressive disease had elevated levels of aldolase A. In contrast, the positive rates were only 9.9% in 71 patients with other urological tumors and 5.8% in 52 cases of benign urological diseases. High concentrations of aldolase A isozyme in RCC tissues might be reflected in elevated serum levels. The present findings indicate that serum aldolase A is a useful biomarker for monitoring the clinical course of patients with RCC.

An immunochemical and immunohistochemical study of aldolase isozymes in renal cell carcinoma

To assess changes in aldolase isozyme patterns (A, B, and C) in renal cell carcinoma (RCC) tissues and to evaluate whether serum aldolase A might be a useful marker for RCC, quantitative analysis by enzyme immunoassay and immunohistochemical localization were performed. Concentrations of aldolase A in RCC (7300 +/- 6300 ng./mg. protein n = 26) were significantly higher than those of normal cortex (720 +/- 410 ng./mg. protein, n = 14, p less than 0.01); concentrations of aldolase C in RCC (48.0 +/- 8.0 ng./mg. protein) were also significantly higher than those of normal cortex (8.7 +/- 4.7 ng./mg. protein, p less than 0.01). On the other hand, concentrations of aldolase B in normal cortex were 18,100 +/- 10,100 ng./mg. protein (n = 14), whereas the values in RCC were only 130 +/- 270 ng./mg. protein, a significant lowering (p less than 0.01). Immunohistochemically, aldolases A and C were found localized in all RCC tissues (n = 10); aldolase B was faintly stained in only a few tumor cells of two cases (20%). Levels of serum aldolase A were elevated (greater than 300 ng./ml.) in 30 (75%) of 40 patients with RCC as compared to three (6.3%) of 48 individuals with urogenital benign diseases and in seven (21%) of 34 cases with non-RCC urogenital malignancies. Since it is generally accepted that RCC are derived from renal proximal tubules, these findings indicate that aldolase B, the predominant isozyme in the normal case, changes into aldolases A and C during carcinogenesis and that serum aldolase A could be a new useful biomarker for RCC.

Sensitive enzyme immunoassay for human aldolase A

A sensitive sandwich-type enzyme immunoassay for the aldolase isozyme, A4, was developed using purified antibodies specific to the A subunit of aldolase. The antibodies were raised in sheep being immunized with purified aldolase A4 and then purified by immunoaffinity chromatography on a column of aldolase A4-coupled Sepharose. The assay system consisted of polystyrene balls with immobilized antibody F(ab')2 fragments and the same antibody F(ab')2 fragments labeled with beta-D-galactosidase from Escherichia coli. The assay was sensitive enough to detect 10 pg/tube of aldolase A4. The assay was specific to the A subunit of aldolase (aldolase A). It cross-reacted about 40% to aldolase A3C, 7% to A2C2 and 0.3% to AC3, but not cross-reacted with C4 nor B4. Coefficients of variation in intra- and inter-assay were less than 16%. Serum aldolase A levels were determined in healthy adults, which were about 200 ng/ml. The distribution and concentrations of immunoreactive aldolase A in various human tissues were also determined. High concentrations of aldolase A were found in skeletal muscle, heart muscle, cerebrum and lymphatic tissue.

Activity of glycogen synthase and phosphorylase and glucose 6-phosphate content in renal clear cell carcinomas

Eleven renal clear cell carcinomas were investigated with regard to their glycogen and glucose 6-phosphate (G6P) content and the activities of glycogen synthase and phosphorylase. Compared to normal cortex from the same kidneys, all tumours revealed increased glycogen and G6P content. The activities of phosphorylase a and b as well as of synthase R and D were also increased. Synthase I activity, however, was reduced. It was concluded that in these tumours glycogen synthesis may preferentially be catalyzed by synthase R which is activated by G6P. These findings agree with those in some other glycogenotic tissues and support the concept that an accumulation of G6P is associated with excessive storage of glycogen in preneoplastic and neoplastic lesions.

Correlative histochemical studies on preneoplastic and neoplastic lesions in the kidney of rats treated with nitrosamines

Renal tubular lesions induced in male rats by two different carcinogens, N-nitrosomorpholine (NNM) and N-ethyl-N-hydroxyethylnitrosamine (EHEN), using a limited exposure "stop" protocol were investigated histochemically to demonstrate phenotypic cellular changes. The parameters measured included basophilia, glycogen content and the activity of the enzymes glucose-6-phosphatase (G6PASE), glycogen synthetase (SYN), glycogen phosphorylase (PHO), glucose-6-phosphate dehydrogenase (G6PDH), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), succinate dehydrogenase (SDH), alkaline phosphatase (ALP), acid phosphatase (ACP) and gamma-glutamyl transpeptidase (gamma-GT). The lesions observed were predominantly of either basophilic or oncocytic types. In each case, tubular lesions (altered tubules) appeared to give rise to epithelial tumors (epitheliomas) with the same cellular phenotype. Basophilic tubules and epitheliomas proved to be strongly positive for GAPDH and G6PDH while demonstrating a reduction or loss of G6PASE, ALP, ACP, gamma-GT, and SDH compared with controls and the surrounding proximal or distal tubules. In addition, large basophilic epitheliomas demonstrated an increase in both SYN and PHO activities. In contrast, most oncocytic tubules and oncocytomas characterized by abundant densely granular cytoplasm showed a reduction in the activity of G6PDH, but were intensely positive for SDH. However, a few oncocytic lesions demonstrated a decrease in both SDH and G6PDH activity. Rarely, decreased SDH and elevated G6PDH activities were observed in altered tubules resembling oncocytic tubules. It remains to be clarified whether these tubules represent a variation of the oncocytic lesions or, perhaps, another type of tubular lesion. The results indicate that basophilic and oncocytic epithelial tumors differ in their cytochemical pattern and histogenesis. In line with earlier suggestions, the basophilic tumors apparently originate from the proximal renal tubules, while the oncocytomas develop from the distal parts of the nephron. The basophilic tumors are characterized by an increased pentose phosphate pathway and glycolysis, with a corresponding reduction in mitochondrial respiration. However, the majority of the oncocytomas show an increased activity of the mitochondrial enzyme SDH, and a marked decrease in the activity of the key enzyme of the pentose phosphate pathway.

Aberrant regulation of carbohydrate metabolism and metamorphosis during renal carcinogenesis

Systematic studies of the sequence of cellular changes during renal carcinogenesis induced in rats by stop experiments with N-nitrosomorpholine or streptozotocin and of human renal cell carcinomas led to the following main results and conclusions: All types of epithelial kidney tumors known from human pathology, namely clear-cell, acidophilic (granular), basophilic, chromophobic and oncocytic tumors, can be induced by the chemicals. Phenotypically altered epithelia resembling those in the tumors appear in single or multiple tubules long before unequivocal tumors develop. The progression from the preneoplastic tubular lesions to the tumors is an autogenous process which is independent of the further action of the carcinogen. At least three different types of tubular lesions can be distinguished: (a) Clear cell tubules storing glycogen in excess, (b) chromophobic or basophilic tubules frequently accumulating acid mucopolysaccharides (glycosaminoglycans, proteoglycans), and (c) oncocytic tubules accumulating atypical mitochondria. Whereas the precise site of origin of the clear cell tubules within the nephron remains unclear, the fine structural and cytochemical findings suggest that the chromophobic and basophilic tubules originate from the proximal and the oncocytic tubules from the distal nephron. Each type of tubular lesion is apparently the precursor of a cytologically specific tumor type. The well-known aberration in carbohydrate metabolism in renal tumors might occur in response to a carcinogen-induced metabolic derangement which is frequently associated with excessive storage of polysaccharides or lipids persisting for weeks and months until fast-growing tumors appear. Whereas the primary biochemical lesion leading to the persisting storage phenomena is most probably fixed at the genetic level, epigenetic changes, namely an adaptation of cellular enzymes gradually activating alternative metabolic pathways, might be responsible for the ultimate neoplastic transformation of the cell.