Renal carcinogenesis

Renal cell carcinoma: Review of etiology, pathophysiology and risk factors

BACKGROUND AND AIMS

The global incidence of renal cell cancer is increasing annually and the causes are multifactorial. Early diagnosis and successful urological procedures with partial or total nephrectomy can be life-saving. However, only up to 10% of RCC patients present with characteristic clinical symptoms. Over 60% are detected incidentally in routine ultrasound examination. The question of screening and preventive measures greatly depends on the cause of the tumor development. For the latter reason, this review focuses on etiology, pathophysiology and risk factors for renal neoplasm.

METHODS

A literature search using the databases Medscape, Pubmed, UpToDate and EBSCO from 1945 to 2015.

RESULTS AND CONCLUSIONS

Genetic predisposition/hereditary disorders, obesity, smoking, various nephrotoxic industrial chemicals, drugs and natural/manmade radioactivity all contribute and enviromental risks are a serious concern in terms of prevention and the need to screen populations at risk. Apropos treatment, current oncological research is directed to blocking cancer cell division and inhibiting angiogenesis based on a knowledge of molecular pathways.

Molecular characterization of preneoplastic lesions provides insight on the development of renal tumors

Kidneys are the second most frequent site for chemically induced cancers in rats. However, there is still limited information on direct effects of carcinogens on pathways involved in the development of kidney tumors. Since transformed tumor cells have different characteristics than their cell of origin, it was hypothesized that healthy tissue and progressing stages of preneoplastic lesions are differentially influenced by chemical carcinogens. To elucidate this question, TSC2(-/-) Eker rats were gavaged with genotoxic aristolochic acid or nongenotoxic ochratoxin A for 3 and 6 months, respectively. Histopathology and cell proliferation analysis demonstrated a compound- and sex-specific onset of preneoplastic lesions. In contrast, comparable gene expression profiles of laser-microdissected preneoplastic lesions from carcinogen-treated and control rats, including reduced expression of genes involved in carcinogen uptake and metabolism, point to a compound-independent lesion progression. Gene expression profiles and additional immunostaining suggested that clonal expansion of renal lesions appears primarily driven by disturbed mammalian target of rapamycin complex 1 and mammalian target of rapamycin complex 2 pathway regulation. Finally, prolonged carcinogen exposure resulted in only marginal gene expression changes in tubules with normal morphology, indicating that some tubules may have adapted to the treatment. Taken together, these findings indicate that the final outcome of in vivo carcinogenicity studies is primarily determined by time-restricted initial events, while lesion progression may be a compound-independent process, involving deregulated mTOR signaling in the Eker rat model.

Quantitative assessment of red meat or processed meat consumption and kidney cancer

OBJECTIVE

To conduct a quantitative assessment of red meat or processed meat consumption and kidney cancer.

METHODS

We extracted data from 12 case-control studies, three cohort studies, and the Pooling Project of Diet and Cancer publication for which 13 international cohorts were evaluated. Random effects meta-analysis models were used to calculate summary relative risk estimates (SRRE) based on high vs. low intake values. Sensitivity and influence analyses were conducted, including assessments of heterogeneity.

RESULTS

The SRRE for all studies that reported results for red meat (included variables labeled 'red meat' or single red meat items, such as beef, pork, or liver) was 1.12 (95% CI: 0.98-1.29; p-value for heterogeneity=0.015), and the SRRE using only data from prospective cohorts was 1.02 (95% CI: 0.91-1.15) with minimal heterogeneity (p=0.741). Similarly, in a meta-analysis of the five studies that simultaneously adjusted for smoking, BMI, and total energy intake, the SRRE for red meat was 1.02 (95% CI: 0.91-1.15). No significant association was observed in the meta-analysis of processed meat consumption (SRRE=1.07; 95% CI: 0.94-1.23), although a significant association was observed when only data from cohort studies were analyzed (SRRE=1.19; 95% CI: 1.03-1.37).

CONCLUSIONS

Although many of the summary results were positive, all were weak in magnitude, most were not statistically significant, and associations were attenuated among studies that adjusted for key potential confounding factors. In summary, the findings of this meta-analysis are not supportive of an independent relation between red or processed meat intake and kidney cancer.

Preneoplastic lesions in rodent kidney induced spontaneously or by non-genotoxic agents: predictive nature and comparison to lesions induced by genotoxic carcinogens

The current literature on non-genotoxic renal carcinogens and the associated neoplastic and preneoplastic lesions has been reviewed in order to determine their occurrence and predictive nature with regard to tumor formation. In addition the mechanisms involved in the genesis of renal tumors are discussed. A more generalized classification of preneoplastic and neoplastic renal lesions was introduced, based on studies conducted with genotoxic and non-genotoxic renal carcinogens. Reports on preneoplastic lesions were found in the literature for control animals as well as animals treated with non-genotoxic carcinogens. Due to the paucity of data regarding preneoplastic lesions in control animals and animals treated with non-genotoxic carcinogens, new data were also generated by rereading kidney slides of control animals of a randomly selected NTP study and kidney slides of male rats treated with the highest dose of ochratoxin A, one of the most potent non-genotoxic renal carcinogens known. The control slides and the slides from the ochratoxin A study indicated that the cytologic and morphologic types of preneoplastic lesions characteristically observed in bioassays using genotoxic carcinogens are also present in control animals and animals treated with non-genotoxic carcinogens. The incidence of preneoplastic lesions was low in control animals and higher in animals treated with non-genotoxic carcinogens. The diverse classifications used in the literature did not allow a direct comparison of lesions and corresponding incidences with those of the newly generated data. However, three major tendencies were observed: (a) whenever a high incidence of preneoplastic lesions was reported, renal neoplasms were also found, (b) the larger the size and the further a lesion had progressed, the higher was the probability of tumor formation, and (c) not all preneoplastic lesions are irreversible, but reversibility seemed to decrease with increasing lesion size and progression. It must be emphasized that the data available for these conclusions are limited. This is not due to the lack of adequate numbers of bioassays with non-genotoxic carcinogens, but rather to the lack of consistent reporting of data. A generalized and more widely used classification which incorporates early lesions would certainly improve the current data base on renal lesions and provide future improvements in the predictive nature of these lesions.

Monoclonal antibody against rat renal cell tumor-associated antigen as a new tool for the analysis of renal tumorigenesis

A monoclonal antibody, NR-2 MAb, against one of the rat renal cell tumor-associated antigens was developed. NR-2 MAb belonged to IgM class and recognized a polypeptide of 81,000 daltons designated as NR-2 antigen, which is of non-glycoprotein nature with a pI of 4.6. NR-2 MAb was employed to probe the histogenesis of renal cell tumors in rats treated with N-ethyl-N-hydroxyethylnitrosamine followed by trisodium nitrilotriacetate monohydrate. Immunohistochemical analysis indicated that NR-2 antigen was expressed in simple hyperplasia, adenomatous hyperplasia and renal cell tumors. Both clear cells and basophilic cells of the simple hyperplasia showed equally strong positive reactions with NR-2 MAb, whereas the vacuolated epithelium was negative. Furthermore, the proximal tubules in nontumorous areas also expressed NR-2 antigen, suggesting that the hyperplastic lesions which eventually lead to renal cell tumors may derive from epithelia of proximal tubules and not directly from vacuolated epithelium. Such NR-2 antigen-positive epithelia of proximal tubules seem to be initiated cells. NR-2 MAb also cross-reacted with preneoplastic liver lesions.

Rat renal mesenchymal tumor as an experimental model for human congenital mesoblastic nephroma: II. Comparative pathology

The morphological features of kidney neoplasms induced by ethylnitrosourea (ENU) with or without prior irradiation were examined with a view to comparing them with human renal tumors of childhood. The rat renal tumors consisted of poorly differentiated, highly mitotic mesenchymal cells frequently attempting to differentiate along fibroblastic and myofibroblastic lineages. Though the host renal tubules were frequently entrapped in these tumors, immature tubules and islands of epithelial cells occasionally were seen to form an integral part of the neoplasms. Rarely, adenomatous areas surrounded by mesenchymal proliferation were observed. None of the tumors had the blastemal component that is the hallmark of nephroblastoma. The rat mesenchymal tumors resembled the human congenital mesoblastic nephroma.

Rat renal mesenchymal tumor as an experimental model for human congenital mesoblastic nephroma: I. Induction

The effect of low-dose (2 Gy) radiation on ethylnitrosourea (ENU)-induced neoplasms was studied in Sprague-Dawley and Holtzman strains of rats. With a 60 mg/kg dose of ENU administered on day 1 in Sprague-Dawley rats, 18.4% of the neoplasms induced were found in the kidney. When the same dose of ENU was given on day 10, the incidence of kidney tumors fell to 2.8%. Prior (2 Gy) radiation on day 9 enhanced kidney tumor induction to 16.1%, a trend also observed in the case of ENU-induced neural tumors. In Holtzman rats, 40 mg/kg ENU induced more kidney tumors (12.5%) when given on day 4 than on day 0, and prior irradiation enhanced the ENU-induced kidney tumors even though the interval between irradiation and carcinogen administration was fairly long--4 days.

Experimental induction of renal tumors

Renal tumors have been reported to be induced by natural products, chemical carcinogens, viruses, or radiation. Species or strain specificity and sex also appear to play significant roles in their development. In man, it is also likely that the heredity existence of other diseases, smoking, food habits, and irradiation may be etiological factors. It also appears that hormonal, chemical, and other environmental factors can play a role. Nephrotoxin modifies two-stage chemical carcinogenesis in rat kidney. Some nephrotoxins without carcinogenicity promote the development of renal tumors in rats pretreated with subcarcinogenic doses of chemical carcinogens. The importance of nephrotoxin in development of renal adenocarcinomas needs elucidation. Preneoplastic lesions in the kidneys can be recognized by histochemical methods with specific antibodies. It is hoped that further research will be continued, so that data obtained from experimental work will provide a better understanding of the etiology and induction of renal cancer in man.

Saccharide alterations in rat kidney associated with malignant transformation by injection of dimethylnitrosamine

Renal tumours were induced in dietary-primed rats by injection of dimethylnitrosamine. Control and tumour tissue was excised at varying periods and maintained in short-term organ culture in the presence of 3H- or 14C-fucose. The plasma membranes were then isolated, and the isotopic profiles of normal kidney and renal tumour membrane proteins were established, using polyacrylamide-gel electrophoresis in dodecyl sulphate. Several fucose-containing glycoproteins of the plasma membranes were found to alter upon neoplastic transformation: 4 increased and 3 decreased. The probable identity of 2 of these proteins is indicated: alpha-foetoprotein is one of the glycoproteins which increased, whereas neutral endopeptidase decreased in the tumour membranes. Fluorescein-labelled lectin binding by the kidney tissue was also found to alter upon transformation. The most marked changes were an increase in sialic acid (neuraminidase-sensitive) and galactosamine (Ricinus communis agglutinin Type I) in the nuclei of some neoplastic cells and some hyperplastic-tubule cells.