Some Aspects of the Epidemiology and Etiology of Esophageal Cancer With Particular Emphasis on the Transkei, South Africa

Esophageal Cancer: Associated Factors with Special Reference to the Kashmir Valley

Esophageal cancer is one of the most common cancers worldwide. It is a multifactorial disease, and no single agent has been identified so far as the sole cause of the cancer. Many factors like smoking, the consumption of alcohol, fungal-contaminated, spicy and various nitrosamine-containing food stuffs and hot beverages, nutritional deficiency of some vitamins like β-carotene, vitamin A, C and E and minerals like zinc, selenium and molybdenum, the use of opium, HPV infection and various genetic factors have been found associated with the occurrence of the disease worldwide. Wide geographic differences and substantial changes in the incidence of esophageal cancer occurring over time have been suggested. Among the risk factors in India, betel quid chewing carries a relatively high risk. High incidences in Kashmir have been associated with the consumption of hot salted tea, sun-dried, smoked foods, tobacco in the form of hukka and various genetic factors. The exact cause of esophageal squamous cell carcinoma is unknown. Much work has been carried out on the role of various environmental factors, gene mutations, and polymorphisms worldwide, including Kashmir. Although the Kashmir valley is present on the border of the ‘high risk esophageal cancer belt’ and esophageal squamous cell carcinoma represents the most commonly occurring malignancy in Kashmir, the amount of information available on various associated factors is still very little as there is a paucity of various epidemiological and molecular studies being carried out in this field.

Burden of cancers in the valley of Kashmir: 5 year epidemiological study reveals a different scenario

Cancer is a major burden worldwide but there are marked geographical variations in frequency and incidence overall. The aim of this study was to find the frequency and distribution of commonly occurring cancers in Kashmir, with particular emphasis on urinary bladder cancer. A total of 4,407 cases of histologically confirmed new cancer cases were registered at the Medical Records Department (MRD) of SKIMS from a period between January, 2005 and April 2010. Among 4407 cancers, 2,457 (55.7 %) were men and 1,950 (44.3 %) were women. Stomach cancer is the leading one with an average frequency of 19.2 % followed by esophagus and lung as 16.5 % and 14.6 %, respectively. Stomach (23 %) and lung (21 %) are the leading cancers in men while as esophageal cancer tops (18.3 %) in women followed by breast cancer (16.6 %). This distribution of cancer types is strikingly different from that in the rest of India where oropharyngeal cancer is most common form. Among urinogenital cancers, bladder cancer was observed to primarily affect Kashmiri population (5.9 %) followed by prostate cancer (2.1 %) and renal carcinoma (1.1 %). We conclude that Kashmir is a very high risk area of most commonly occurring cancers particularly cancers of gastrointestinal tract which comprise more than half the frequency of all the cancers.

Maize meal predisposes to endemic squamous cancer of the oesophagus in Africa: breakdown of esterified linoleic acid to the free form in stored meal leads to increased intragastric PGE2 production and a low-acid reflux

Endemic cancer of the oesophagus in Africa is associated with the use of maize as the staple. In one African community endemic cancer of the oesophagus has been shown to have a strong statistical association with the consumption of foods based on maize in the meal form. A strong association with consumption of maize meal has also been shown in a region of Italy. It has been argued in the past that the association with maize consumption is due to a fortuitous association; or due to the nutritional deficiencies of maize meal; or due to fungal contamination. We argue that maize meal is a distinctly different food from whole maize, and that nutritional content as much as deficiency is responsible for predisposition of the oesophagus to carcinogenesis. An important factor is the breakdown of esterified linoleic acid to the free form in stored maize meal. This leads to excess production of prostaglandin E2 in the stomach. The excess Prostaglandin E2 causes a low-acid duodenogastro-oesophageal reflux, which predisposes to carcinogenesis. Supporting evidence is available that the steps of this mechanism occur in endemic areas, and that they are associated with the carcinogenic process. Health measures including poverty alleviation, health education, and monitoring and control of maize meal storage and content may be required to reduce the incidence of this disease in Africa.

The effects of L-748706, a selective cyclooxygenase-2 inhibitor, on N-nitrosomethylbenzylamine-induced rat esophageal tumorigenesis

Epidemiological studies suggest that the frequent intake of non-steroidal anti-inflammatory drugs (NSAIDs) is associated with a decreased risk of developing esophageal squamous cell carcinoma (SCC). This decrease is thought to correlate with the inhibition of cyclooxygenase (COX) activity. The production of prostaglandin E2 (PGE2), a major metabolite of COX, is increased in numerous human cancers including esophageal SCC, therefore, inhibition of COX activity and subsequent suppression of the formation of PGE2 may be chemopreventive in the esophagus. The objective of the present study was to determine whether L-748706 (L-706), a novel selective COX-2 inhibitor, would prevent N-nitrosomethylbenzylamine (NMBA)-induced esophageal tumor progression in the Fischer 344 (F344) rat. In rats pretreated with a low-dose of NMBA (0.25 mg/kg body weight), L-706 at 100 p.p.m. in the diet significantly reduced tumor multiplicity but not tumor incidence. At 150 p.p.m. in the diet, L-706 alone and in combination with 200 p.p.m. piroxicam produced significant reductions in both tumor incidence and multiplicity. Inhibition of tumor development in low-dose NMBA-treated rats was associated with reductions in esophageal cell proliferation rates and PGE2 levels in preneoplastic tissues. In contrast, in rats treated with a higher dose of NMBA (0.5 mg/kg body weight), neither L-706 alone nor in combination with piroxicam reduced esophageal tumor incidence or multiplicity in spite of the fact that they reduced esophageal PGE2 levels in preneoplastic tissues and in papillomas. Cell proliferation rates were reduced only in animals treated with L-706 + piroxicam. Our data suggest that the chemopreventive treatments were effective in inhibiting tumor development in NMBA-treated animals only when they reduced PGE2 levels in preneoplastic esophageal tissues approximately to those levels found in normal esophagus.

Endoscopic screening and determination of p53 and proliferating cell nuclear antigen in esophageal multistage carcinogenesis: a comparative study between high- and low-risk populations in Henan, northern China

The objective of this study was to characterize the histologic changes from endoscopic screening for early esophageal cancer (EC) on subjects at high-incidence area (HIA) and low-incidence area (LIA) in Henan, China, and to further compare the changes in p53 and proliferating cell nuclear antigen (PCNA) in the multistage of human esophageal carcinogenesis from these two populations. The detection rate of basal cell hyperplasia (BCH) and dysplasia (DYS) was higher in the subjects from HIA than in those from LIA. Out of the 1568 symptom-free subjects examined at HIA, 10 (0.6%) cases with early squamous cell carcinoma (SCC) were identified. Immunoreactivity of p53 and PCNA was observed in cell nuclei of esophageal biopsies and surgically resected esophageal cancer specimens both in HIA and LIA. With the lesions progressed from normal epithelium to BCH to DYS to SCC, the positive-immunostaining cells expanded from basal layer to superficial layer, and the number of positive cells/mm2 for p53 and PCNA increased, and was significantly higher in HIA than in LIA among the similar morphological lesions (P < 0.01). The number of p53 positive cells/mm2 in SCC from HIA was almost fivefold higher than SCC from LIA (P < 0.01). The remarkable difference was also observed between HIA and LIA in DYS and BCH. The present results indicate that p53 protein accumulation is an important early biomarker for identifying high-risk subjects for EC.

Changes of TGFbeta1 and TGFbetaRII expression in esophageal precancerous and cancerous lesions: a study of a high-risk population in Henan, northern China

The level of transforming growth factor beta1 (TGFbeta1) and transforming growth factor betaII receptor (TGFbetaRII) was determined immunohistochemically in normal tissues and tissues with different severities of lesions (basal cell hyperplasia, BCH; dysplasia, DYS; carcinoma in situ, CIS; and squamous cell carcinoma, SCC) from surgically resected human esophagi and esophageal biopsies of symptom-free subjects. The samples were from an area with high esophageal cancer incidence in northern China (Linzhou, formerly Linxian, and nearby county Huixian in Henan Province). Peroxidase immunostain (ABC) and conventional hematoxylin and eosin stain were used. The tissue sections were incubated with antibodies of TGFbeta1 and TGFbetaRII overnight. The immunoreactivity was observed in cytoplasm of the esophageal specimen. From normal to BCH to DYS to CIS and to SCC, the positive immunostaining rates for TGFbeta1 increased significantly (P < 0.05). A linear correlation between the positive immunostaining rates of TGFbeta1 and the different lesions was observed (P < 0.05). From well- to moderately- and poorly differentiated SCC, the positive immunostaining rates for TGFbeta1 decreased gradually, but the difference was not significant (P > 0.05). In contrast, with the lesions progressing from normal to BCH to DYS to CIS and to SCC, the positive immunostaining rates for TGFbetaRII decreased significantly (P < 0.05). From well- to moderately- and poorly differentiated SCC, the positive immunostaining rates for TGFbetaRII decreased significantly (P < 0.05). There was a linear correlation between the positive rates of TGFbetaRII and different lesions and SCC differentiation (P < 0.05). The present results indicated that the alterations of TGFbeta1 and TGFbetaRII is a frequent event in esophageal multistage carcinogenesis, the absent or lower expression of TGFbetaRII may lead to the loss of cell proliferation control by TGFbeta1 and the overexpression of TGFbeta1 may be a negative feedback response caused by the lower expression of TGFbetaRII protein.

Effects of N-acetylcysteine in an esophageal carcinogenesis model in rats treated with diethylnitrosamine and diethyldithiocarbamate

Due to the increasing role of esophageal tumors in human cancer pathology, there is need for animal models evaluating the mechanisms of esophageal carcinogenesis and investigating protective factors toward this disease. Several N-nitrosamines have been shown to induce esophageal tumors in rats. We designed a study in BD(6) rats treated with N-diethylnitrosamine (DEN) according to a simple protocol involving weekly i.p. injections of this carcinogen for 8 consecutive weeks. This treatment resulted in a high incidence and multiplicity of liver tumors and in occurrence of preneoplastic lesions and papillomas in the esophagus. Intraperitoneal injections of diethyldithiocarbamate (DEDTC), 4 hr after each DEN injection, i.e., during the period of DEN metabolization, improved survival of rats and did not affect the liver tumor yield but doubled the incidence of esophageal tumors and enhanced 4.9x their multiplicity. Moreover, 15% of rats developed esophageal squamocellular carcinomas. The oral administration of the thiol N-acetyl-L-cysteine (NAC), a precursor and analogue of reduced glutathione, to rats treated with the DEN/DEDTC combination did not change the liver tumor yield but attenuated esophageal carcinogenesis by producing a significant shift of preneoplastic lesions to milder forms as well as a significant decrease of tumor multiplicity. Therefore, the DEN/DEDTC protocol appears to provide an interesting 2-organ model of N-nitrosamine-induced carcinogenesis in rats, in which NAC is moderately effective as an inhibitor. The mechanisms underlying enhancement of DEN-induced esophageal carcinogenesis by DEDTC and the protective effects of NAC are discussed.

Effects of dietary N-(4-hydroxyphenyl)retinamide on N-nitrosomethylbenzylamine metabolism and esophageal tumorigenesis in the Fischer 344 rat

BACKGROUND

9-cis-Retinoic acid (9-cis-RA) and N-(4-hydroxyphenyl)retinamide (4-HPR) are effective chemopreventive agents against epithelial tumors in the oral cavity, breast, and prostate. We tested the inhibitory activity of these retinoids against N-nitrosomethylbenzylamine (NMBA)-induced tumorigenesis in the rat esophagus.

METHODS

Male Fischer 344 rats were randomly assigned to receive diets either lacking or containing 9-cis-RA or 4-HPR for 1 week before tumor initiation with NMBA and then for the duration of the study. NMBA metabolism, O(6)-methylguanine adduct formation, and cytochrome P450 messenger RNA (mRNA) expression in the esophagi of the rats were studied to investigate the mechanisms by which dietary 4-HPR affects tumorigenesis. All statistical tests were two-sided.

RESULTS

Dietary 4-HPR resulted in a dose-dependent and statistically significant enhancement (P<.05) of tumorigenesis in response to NMBA. In two different tumor bioassays, the mean tumor multiplicity for rats fed the highest concentration of dietary 4-HPR (0.8 g/kg diet) was increased by 5.9 tumors (95% confidence interval [CI] = 1.7 to 10.1 tumors) and 6.7 tumors (95% CI = 5.6 to 7.8 tumors) compared with the mean tumor multiplicity for rats that received the control diet lacking 4-HPR. Animals fed diets containing 9-cis-RA displayed no statistically significant increase in tumorigenesis. Compared with animals fed a diet lacking 4-HPR, animals fed 4-HPR had increased NMBA metabolism in esophageal explant cultures and had higher levels of O(6)-methylguanine DNA adducts and CYP2A3 mRNA in their esophagi.

CONCLUSIONS

Dietary 4-HPR enhances tumorigenesis in response to NMBA in the rat esophagus by increasing tumor initiation events. Dietary 4-HPR may exert paradoxical effects at some sites, such as the aerodigestive tract, by modulating the bioactivation of carcinogens in target tissues.

Investigation of the enhancement of N-nitrosomethylbenzylamine-induced esophageal tumorigenesis by 6-phenylhexyl isothiocyanate

Previous studies in our laboratory have shown that 6-phenylhexyl isothiocyanate (PHITC), enhances N-nitrosomethylbenzylamine (NMBA)-induced esophageal tumorigenesis in F344 rats while the shorter chain analogs, phenylethyl isothiocyanate (PEITC), and 3-phenylpropyl isothiocyanate (PPITC), inhibit NMBA-induced esophageal tumorigenesis. To test the hypothesis that PHITC influences the promotional stage of esophageal tumorigenesis, groups of 22-27 rats were dosed with vehicle or NMBA three times a week for 5 week, and fed a modified AIN-76A diet containing PHITC at concentrations of 0.0, 1.0, and 2.5 micromol/g. At the 25th week, the rats were killed, esophagi harvested and tumors counted. In the groups that received NMBA+PHITC, apparent but statistically insignificant increases in tumor multiplicity of 32 and 42% were found in comparison to rats treated with NMBA alone. A higher frequency of dysplastic lesions was found in rats treated with NMBA+2.5 micromol/g PHITC (71%) when compared to rats treated with NMBA only (12%). To test whether PHITC increased cellular proliferation, we evaluated proliferating cell nuclear antigen (PCNA) expression by immunohistochemistry. While there were no significant increases in PCNA staining in rats treated with NMBA+PHITC compared to rats treated with NMBA only, rats treated with PHITC only had a significantly higher PCNA index compared to untreated controls. Expression of cyclin D1, another biomarker of proliferation, was analyzed by semi-quantitative reverse transcription-polymerase chain reaction. There were no significant increases in cyclin D1 expression in groups treated with NMBA+PHITC compared to the group treated with NMBA only. Thus, while the data suggest a promotional effect by PHITC as manifested by a significant increase in dysplastic leukoplakia by the high dose of PHITC and an increase in the PCNA index by PHITC alone, PHITC does not appear to have a significant effect on esophageal cell proliferation.

Chemopreventive effect of curcumin on N-nitrosomethylbenzylamine-induced esophageal carcinogenesis in rats

Modifying effects of curcumin (derived from the rhizome of Curcuma longa L.) during the initiation or post-initiation phase of N-nitrosomethylbenzylamine (NMBA)-induced esophageal carcinogenesis were investigated in male F344 rats. Five-week-old rats were divided into 5 groups, and groups 1, 2 and 3 were given intraperitoneal injections of NMBA (0.5 mg / kg body weight / injection 15 times) for 5 weeks from 7 weeks old to induce esophageal neoplasms. Groups 2 and 3 were fed the diet containing 500 ppm curcumin during the initiation and post-initiation phases, respectively. Group 4 was given the diet containing curcumin throughout the experiment, and group 5 was kept on the basal diet alone and served as an untreated control. Incidence and multiplicity of esophageal neoplasms of group 1 (NMBA alone) were 66.7% and 0.83 +/- 0.70, respectively. Those of groups 2 and 3 were significantly less than those of group 1 (39.3%, 0.46 +/- 0.64, P < 0.05; 33.3%, 0.36 +/- 0.56, P < 0.05, respectively). Furthermore, the incidence and multiplicity of esophageal preneoplastic lesions (moderate or severe epithelial dysplasia) of group 2 (57.1%, 0.61 +/- 0.57; 40%, 0.29 +/- 0.46) or 3 (56.7%, 0.67 +/- 0.66; 23.3%, 0.23 +/- 0.43) were less than those of group 1 (100%, 1.67 +/- 0.70; 70.8%, 0.92 +/- 0.72) (P < 0.05). In this experiment, feeding of curcumin significantly decreased the expression of cell proliferation biomarkers (5-bromo-2'-deoxyuridine labeling index) in the non-lesional esophageal epithelium (P < 0.01). These findings indicate that curcumin inhibits NMBA-induced esophageal carcinogenesis when given during the post initiation as well as initiation phase. This inhibition may be related to suppression of the increased cell proliferation induced by NMBA in the esophageal epithelium.

Molecular alterations of p73 in human esophageal squamous cell carcinomas: loss of heterozygosity occurs frequently; loss of imprinting and elevation of p73 expression may be related to defective p53

p73 is structurally and functionally related to p53 and is possibly a tumor suppressor gene. Using 15 surgically resected frozen esophageal specimens containing both squamous cell carcinomas (ESCC) and neighboring normal epithelia, we studied p73 gene alterations and mRNA expression. Loss of heterozygosity of the p73 loci was found in nine of 14 informative cases (64%). A polymorphism at codon 173 (Thr) of p73 was identified (eight samples had ACC and seven had ACT), but mutation was not detected in tumor samples. Nine of the 15 ESCC samples (60%) displayed significantly elevated expression of p73 over the neighboring normal epithelium; of these nine samples, four displayed loss of imprinting (LOI) and one switched the expressed allele. Hypermethylation of exon 1 of the p73 gene was not detected, using the bisulfite modification method, in normal or tumor samples. Twelve of the 15 (80%) ESCC samples contained p53 defects, including missense mutation, non-frameshift small deletion or insertion, non-detectable transcripts and protein accumulation. The ESCC samples with p53 defects were significantly correlated with those which had elevated expression of p73 (Fisher's exact test, P < 0.05). The results suggest that increased expression of p73, including that by LOI, could be a partial compensatory mechanism for defective p53.

Suppression of N-nitrosomethylbenzylamine-induced rat esophageal tumorigenesis by dietary feeding of 1'-acetoxychavicol acetate

The modifying effects of 1'-acetoxychavicol acetate (ACA) on N-nitrosomethylbenzylamine (NMBA)-induced esophageal tumorigenesis were investigated in male F344 rats. At 5 weeks of age, all test animals, except those given the test chemical alone, and the control rats received s.c. injections of NMBA (0.5 mg/kg body weight/injection, three times per week) for 5 weeks. At the termination of the study (20 weeks), 75% of rats treated with NMBA alone had esophageal neoplasms (papillomas). However, the groups given a dose of 500 ppm ACA during the initiation phase developed a significantly reduced incidence of tumors (29%; P<0.01). Exposure to ACA (500 ppm) during the post-initiation phase also decreased the frequency of the tumors (38%; P<0.05). A reduction of the incidence of preneoplastic lesions (hyperplasia or dysplasia) was obtained when ACA was administered in the initiation phase (P<0.01). Cell proliferation in the esophageal epithelium, determined by assay of proliferating cell nuclear antigen (PCNA), was lowered by ACA (P<0.05). Blood polyamine contents in rats given NMBA and the test compound were also smaller than those of rats given the carcinogen (P<0.05). These findings suggest that dietary ACA is effective in inhibiting the development of esophageal tumors by NMBA when given during the initiation or post-initiation phase, and such inhibition is related to suppression of cell proliferation in the esophageal epithelium.

Diet, reflux and the development of squamous cell carcinoma of the oesophagus in Africa

BACKGROUND

Squamous cancer of the oesophagus has reached epidemic proportions in Africa in the past few decades. There are many known associations but as yet no well established theory of causation.

METHODS

Relevant literature was found by manual review of appropriate journals and literature, Medline searches and cross-referencing. Published theories of causation of endemic cancer of the oesophagus were assessed in the light of available evidence. A hypothesis based on that evidence was formulated.

RESULTS AND CONCLUSION

A predominantly maize-based diet is high in linoleic acid, a precursor for gastric prostaglandin synthesis. In combination with low intake of other fatty acids and riboflavin, high levels of prostaglandin E2 are produced in gastric mucosa, leading to reduced gastric acid secretion, relaxation of the pylorus and a reduction in lower oesophageal sphincter pressure. These events result in combined reflux of duodenal and gastric juices low in acidity into the oesophagus. Resulting dysplasia strongly predisposes to local squamous carcinogenesis. This is now a fertile area for research, which may open the way for preventive action.

Absence of human papillomavirus genomic sequences detected by the polymerase chain reaction in oesophageal and gastric carcinomas in Japan

AIMS

To estimate the occurrence of human papillomavirus (HPV) infection in oesophageal or gastric carcinomas in patients in Japan.

METHODS

103 oesophageal and 99 gastric carcinomas were investigated by polymerase chain reaction (PCR) assays using two consensus (targeting either the L1 or the E6-E7 regions) and two type specific (type 16 and 18) primer sets. A beta globin gene specific primer set was also applied to examine the quality of the extracted DNA.

RESULTS

Amplification of beta globin gene was clearly visible in 92 (89.3%) of the 103 oesophageal, and 89 (89.8%) of the 99 gastric carcinoma specimens. However, the entire series of tumour DNA was negative for HPV sequences by PCR assay using all four primer sets.

CONCLUSION

HPV is not likely to be involved in oesophageal or gastric tumorigenesis in Japanese patients.

Alterations in transforming growth factor-alpha and epidermal growth factor receptor expression during rat esophageal tumorigenesis

Transforming growth factor-alpha (TGF-alpha) stimulates cell proliferation through interaction with its receptor, the epidermal growth factor receptor (EGFR), by activating its tyrosine kinase activities. The simultaneous overexpression of TGF-alpha and EGFR by tumor cells is thought to trigger the autocrine growth pathway, leading to uncontrolled proliferation. To examine their roles in rat esophageal tumorigenesis induced by the chemical carcinogen N-nitrosomethylbenzylamine (NMBA), TGF-alpha, and EGFR expression was evaluated in normal rat esophageal epithelium, in NMBA-induced preneoplastic lesions, and in papillomas by quantitative reverse transcription-polymerase chain reaction (RT-PCR), in situ hybridization, and immunohistochemical analyses. Compared with the levels in normal epithelium, the TGF-alpha and EGFR mRNA levels in esophageal papillomas were 3.6 and 1.9 times higher, respectively. In the preneoplastic epithelium, although a trend of increased TGF-alpha and EGFR mRNA levels was observed, collectively there were no significant differences between preneoplastic and normal samples by RT-PCR analysis. In situ hybridization and immunohistochemical staining showed increased levels of TGF-alpha and EGFR mRNA and protein products in papillomas and in pronounced hyperplastic and dysplastic lesions. TGF-alpha and EGFR expression correlated with each other and with the expression of proliferating cell nuclear antigen, a marker for cell proliferation. These results suggest that disregulation of TGF-alpha and EGFR expression may contribute to autonomous cell growth and may play an important role in rat esophageal tumorigenesis induced by NMBA.

Absence of human papillomavirus DNA from esophageal carcinoma as determined by multiple broad spectrum polymerase chain reactions

Strong evidence has implicated human papillomaviruses (HPV) in the pathogenesis of anogenital cancers and a number of other mucosal and cutaneous lesions. Data concerning the involvement of HPV in esophageal cancers are controversial. Different investigators have detected HPV types (mainly types 16 and 18) in biopsy specimens of esophageal cancers. A study was undertaken to determine whether responses to chemotherapy of advanced squamous cell carcinomas could be correlated with the HPV status. Polymerase chain reaction (PCR) amplification was used for the detection of HPV DNA in biopsies of esophageal squamous cell carcinomas treated with either surgical resection alone (n = 42) or chemotherapy followed by surgical resection (n = 21). Different general and consensus PCR primer sets, which allow the detection of most of the known as well as a number of not yet characterized HPV types, were used. HPV DNA was not detected in any of the 61 esophageal squamous cell carcinomas, suggesting that HPV infections are not likely to play a major role in the etiology of this neoplasm.

Carcinogenesis and histogenesis of esophageal carcinoma

Dysplasia is one of the most important subjects regarding carcinogenesis of the esophagus, because there is continuing controversy as to whether esophageal dysplasia is a cancerous lesion or a noncancerous lesion. In this study, it is histopathologically shown that dysplasia has a close correlation with cancer itself and that there is no substantial difference in the cell proliferative activity of dysplasia and intraepithelial carcinoma. These findings thus show that dysplasia has as high a potential for malignancy, thus it should be treated as an extremely early cancerous lesion of the esophagus to substantially improve the long term results of this disease. Conversely, esophageal carcinoma with glandular and/or mucus-secreting components is commonly found in addition to the ordinary component of squamous cell carcinoma, which indicates that this type of esophageal tumor originates not only from the squamous epithelium but also from the esophageal mucus gland or the ductal epithelium. These findings support the concept of field carcinogenesis in esophageal carcinoma.

Changes in p53 and cyclin D1 protein levels and cell proliferation in different stages of human esophageal and gastric-cardia carcinogenesis

The objective of this study was to quantify the changes in p53 and cyclin D1 protein levels in different stages of human esophageal and gastric cardia carcinogenesis in a high-risk population in Henan, China. Immunoreactivity of p53, cyclin D1 and proliferating-cell nuclear antigen (PCNA) was observed in the cell nuclei of esophageal and gastric cardia biopsies. The number of p53-immunostaining-positive cells was low in normal epithelia, slightly increased in basal-cell hyperplasia (BCH), markedly increased in dysplasia (DYS) (10-fold), and further increased in squamous-cell carcinoma (SCC) (40-fold). This pattern of change was similar to that of cell proliferation as indicated by PCNA immunostaining. On the other hand, the number of cyclin D1-immunostaining-positive cells did not increase from BCH to DYS, although a slight increase from DYS to SCC was noted. In the gastric cardia, again, the pattern of change of p53-positive cells in different stages of lesions paralleled the pattern of cell proliferation. The number of p53-positive cells was very low, much lower than that of PCNA-positive cells, in normal, chronic superficial gastritis (CSG) and chronic atrophic gastritis (CAG); therefore, the increase of p53-positive cells from CAG to DYS was more dramatic (100-fold). From DYS to adenocarcinoma (AC), the p53-positive and the PCNA-positive cells increased 4-fold. On the other hand, the number of cyclin D1-positive cells did not increase in pre-cancerous lesions, but increased slightly in AC. This study demonstrates that p53 protein accumulation increased with the progression of pre-cancerous lesions, especially in the genesis of dysplasia, both in the esophagus and in the gastric cardia. Our approach of quantitative immunohistochemistry sheds light on the mechanisms of genesis of esophageal and gastric-cardia cancers, which frequently occur together in many high-incidence areas.

Expression of multiple oncogenes in human esophageal carcinomas

To study the oncogenesis of human esophageal carcinoma, the expression of a variety of oncogenes was studied in 10 esophageal carcinoma cell lines and 16 pairs of tumor and nontumor tissues removed from patients with esophageal carcinoma. Northern blot analyses using 11 different oncogene probes revealed that 5 oncogenes, i.e. c-myc, c-H-ras, c-sis, c-raf, and c-fos, were expressed. Among them, a variant c-sis mRNA transcript of 2.7 kilobase (kb) was expressed in 7 of 10 cell lines and in 9 of 16 tumor tissues. Furthermore, an overexpression and an amplification of c-myc gene was observed in some cell lines. These results suggest that multiple oncogene expression may be required for the induction, maintenance, and progression of esophageal carcinoma. The expression of a 2.7-kb transcript, of c-sis and overexpression of c-myc gene may play some role in the carcinogenesis of esophageal carcinoma.

A biomarker for the assessment of niacin nutriture as a potential preventive factor in carcinogenesis

The study of protective cellular responses to DNA damage has led to the working hypothesis that optimal niacin nutriture is a preventive factor in cancer. Described here is the development of a biomarker for determining niacin status termed Niacin Number. The combination of this biomarker with diet and cancer epidemiology will allow evaluation of the possible role of this nutrient in cancer risk.

Infectious agents in the etiology of esophageal cancer

Extensive epidemiological and experimental studies have suggested that some chemical agents, nutritional deficiencies, and physical factors are associated with the development of esophageal cancer (EC). Recent evidence also suggests an etiologic role of certain microorganisms in esophageal carcinogenesis either by producing carcinogens or promotors or by acting directly on the host cells. The mutagenic and carcinogenic effects of several fungi and bacteria isolated from the grains and foodstuffs in high-risk areas have been shown by in vitro and in vivo studies. Certain viruses, e.g., human papillomavirus, herpes simplex virus, cytomegalovirus, and Epstein-Barr virus, have been implicated in the pathogenesis of a variety of human cancers, and all of them are known to produce tumors in animals and cell transformation in vitro. These viruses also have been shown to infect the esophageal epithelium. Therefore, although many of the key issues of their mechanisms of action are unclear as yet, they should be considered potential etiologic agents of EC. The present review summarizes the data available on the etiology of EC, emphasizing the current evidence implicating an etiologic role of microorganisms in the pathogenesis of this malignancy.

High incidence of oesophageal and gastric cancer in Kashmir in a population with special personal and dietary habits

Over a three year period (1 July 1986 to 30 June 1989) all newly diagnosed and histologically proved cases of oesophageal and gastric cancer were recorded prospectively. Some 1515 cases of oesophageal cancer (1050 men and 465 women) and 966 cases of gastric cancer (789 men and 177 women) were registered. Seven patients had simultaneous oesophageal and gastric cancer. Age standardised incidence rates for oesophageal cancer were: men 43.6/100,000 per year; women 27.9/100,000 per year. The rates for gastric cancer were: men 36.7/100,000 per year, women 9.9/100,000 per annum. These figures were three to six times higher than those recorded by cancer registries in Banglore, Madras, and Bombay. The incidence rates for oesophageal and gastric cancer in Islamabad (southern district of Kashmir) were 4.1 to 5.4 times higher in men and 1.5 to 2.0 times higher in women than those for Kupwara (northern district of Kashmir). The incidence rates for oesophageal and gastric cancer in Muslims, Hindus, and Sikhs were different. The epidemiology of oesophageal cancer in Kashmir was similar to that found in the 'Asian oesophageal cancer belt'. At the same time Kashmir also had an unprecedented high incidence of gastric cancer. Kashmiries have special personal and dietary habits. Further studies are needed to define the relation between these habits and the occurrence of oesophageal and gastric cancer.

Abnormal sister-chromatid exchange induction by 3-aminobenzamide in an SV40-transformed Indian muntjac cell line: relationships with DNA maturation and DNA-strand breakage

In SVM cells, an SV40-transformed line of Indian muntjac fibroblasts, levels of sister-chromatid exchanges are known to be abnormally high after UV-irradiation or alkylation. The SVM line is also known to have a defect in the processing of DNA-strand breaks. Sister-chromatid exchange in other cells is known to be stimulated by the poly(ADP-ribose) transferase inhibitor, 3-aminobenzamide, which also retards DNA-break sealing. Sister-chromatid exchanges in SVM cells are found to be hypersensitive to 3-aminobenzamide, or to nicotinamide deprivation which similarly inhibits poly(ADP-ribosyl)ation; DNA-strand breaks are likewise induced by 3-aminobenzamide. Bromodeoxyuridine, needed to detect sister-chromatid exchanges, is more toxic to SVM cells and itself induces sister-chromatid exchanges to a greater extent than it does in normal muntjac cells. However, in contrast to the situation reported for other cell types prone to sister-chromatid exchange (the Chinese hamster ovary mutant EM9 and human Bloom's Syndrome cells), SVM cells do not show an abnormal delay in DNA maturation when, under the influence of bromodeoxyuridine and 3-aminobenzamide, they show a high level of sister-chromatid exchange. The mechanism by which BrdU exerts its effects can largely be explained in terms of familiar effects on deoxyribonucleotide pools and DNA integrity. 3-Aminobenzamide, however, induces sister-chromatid exchanges in SVM cells by another mechanism.

Esophageal cancer and microelements

Epidemiological studies have identified dietary zinc deficiency, methylbenzylnitrosamine, and ethanol as factors strongly associated with an increased incidence of esophageal carcinoma in man. In addition, these studies have identified other trace elements which may also affect the incidence of esophageal carcinoma. Animal models have confirmed that dietary zinc deficiency increases the incidence of methylbenzylnitrosamine-induced esophageal carcinoma and that dietary zinc deficiency also increases the incidence of other dialkylnitrosamine-induced carcinomas. The dialkylnitrosamine carcinogens are activated by NADPH-dependent cytochrome P-450 enzymes in their target tissues. The activated methylbenzylnitrosamine methylates DNA, forming O6-methylguanine adducts. These O6-methylguanine adducts can lead to point mutations in DNA, and such mutations are known to be responsible for the induction of certain carcinogen-induced tumors. We have demonstrated that dietary zinc deficiency increased the cytochrome P-450-dependent microsomal metabolism of methylbenzylnitrosamine and dimethylnitrosamine, two members of this class of dialkylnitrosamine carcinogens, while the addition of zinc in vitro noncompetitively inhibits the microsomal metabolism of these carcinogens. We have also demonstrated that dietary zinc deficiency is associated with an increased formation of O6-methylguanine in the esophageal DNA of zinc-deficient animals treated with methylbenzylnitrosamine. This increased formation of the mutagenic DNA adduct O6-methylguanine may explain the increased incidence of dialkylnitrosamine-induced carcinomas observed with dietary zinc deficiency. Other trace elements, including molybdenum, selenium, and magnesium, may also alter the incidence of esophageal carcinoma, but studies of these elements are not as conclusive as the epidemiological and experimental studies linking dietary zinc deficiency with an increased incidence of human esophageal carcinoma.

The role of micronutrient deficiency in carcinogenesis

Nutritional deficiencies are suspected to be contributing factors to several types of human cancers. Studies with laboratory animals have demonstrated that deficiencies in certain nutrients can enhance chemically induced carcinogenesis. In this review, we discuss several possible mechanisms for the involvement of nutritional deficiencies in carcinogenic processes, and note that different severities of deficiency may have varied effects on these processes. The relationship between results from studies with animals and the genesis of human cancer is discussed, and the application of the concept of nutrient density in relating experimental animal diets to human dietary conditions is emphasized. We also discuss in detail several recent studies that potentially may have a great impact on the prevention of human cancer. These include (1) the possible involvement of micronutrient deficiencies in carcinogenesis of the esophagus; (2) the effects of choline/methionine deprivation and calcium supplementation on liver carcinogenesis; and (3) the roles of low-calcium and high-fat intake on development of colon cancer. The possible mechanistic link between teratogenesis and carcinogenic processes is noted.

Chromosome analysis on a cell line (CE48T/VGH) derived from a human esophageal carcinoma

The cell line CE48T/VGH was established from an epidermoid carcinoma of the middle third of the esophagus of a 58-year-old male patient. Cytogenetic analysis at passages 90-99 showed that the line was hypotetraploid, with a mean chromosome number of 73. None of the 50 karyotyped cells had a normal chromosome #1 or Y. Cells with multiple copies of some of the autosomes were observed frequently. Structural rearrangements were numerous, especially of chromosomes #1, #9, #14, X, and Y.

Role of zinc deficiency in carcinogenesis

Zinc is a trace element required for the growth of normal and neoplastic tissues in a variety of species. Zinc deficiency is associated with alterations in the activity of zinc-dependent enzymes essential for cell replication. Dietary zinc deficiency also increases the incidence of certain tumors while decreasing the incidence of others. The mechanism by which zinc deficiency alters carcinogenesis is not fully understood. Among those tumors whose incidence is increased by dietary zinc deficiency are carcinomas induced by dialkylnitrosamines. This class of carcinogens requires microsomal cytochrome P-450 activation to be mutagenic. Zinc deficiency is known to increase the cytochrome P-450-dependent metabolism of methylbenzylnitrosamine (MBN), an esophageal carcinogen of this class. Examination of the kinetics of this reaction reveals zinc to be a direct noncompetitive inhibitor of the microsomal metabolism of MBN. Thus the lower rate of MBN metabolism by zinc-adequate versus zinc-deficient microsomes may be due to normal tissue zinc acting as a noncompetitive inhibitor of cytochrome P-450 activity in vivo. This effect of zinc on carcinogen metabolism may explain the increased incidence of nitrosamine-induced carcinomas observed with dietary zinc deficiency.

The influence of niacin and nicotinamide on in vivo carcinogenesis

Data concerning effects of the essential vitamin niacin and its active form nicotinamide were evaluated. Dietary deficiencies and excesses of these nutrients by themselves do not appear to exert any influence on in vivo carcinogenesis in animals. Varying results were produced when nicotinamide was administered at pharmacologic doses concurrently with or following carcinogen administration to mice or rats. Some investigators found significantly increased tumor formation, whereas others reported a decreased effect or no effect. Epidemiologic studies have not investigated the relationship between niacin deficiency or excess and carcinogenesis in humans.

Mutagen content of wines contaminated with common yeasts

Wines exhibiting a microbial haze were collected and their microbial contents identified. Contaminant yeast species were cultured in grape musts under controlled conditions and extracts of the resultant wines were assayed for mutagen content using four strains of Salmonella in the Ames Salmonella/microsome/faecalase system. The wine extracts exhibited some toxicity to Salmonella but no mutagen content. It would appear that mutagen content is more a function of the grape species and must preparation than of microbial metabolism during fermentation.

Diet and vitamin nutrition of the high esophageal cancer risk population in Linxian, China

In order to examine the nutritional status of the population of Linxian (in Henan, China) known to be at high risk for esophageal cancer (EC), we analyzed blood samples and conducted 3-day dietary surveys on 3 groups of normal adults, age 40-50, from Henan province. Two groups were from Linxian, where the EC mortality rate is about 138/100,000 (Group C, consisting of volunteers with a family history of EC, and Group NC, consisting of those who did not have a family history of EC). The third group, Group F, was from Fanxian, where the EC mortality rate is about 24/100,000. The average plasma retinol level was found to be about 0.27 micrograms/ml in all 3 groups; about 13%-20% of the individuals had a level less than 0.2 micrograms/ml. The average plasma carotene level of all 3 groups appeared to be adequate, ranging from 0.5-1.0 micrograms/ml. About 23% of the subjects in both Groups C and NC had low (less than 2 micrograms/ml) plasma ascorbate levels; in Group F, 16% had low ascorbate levels. Less than 12% of the individuals in each of the 3 groups had erythrocyte glutathione reductase activation coefficients less than 1.2, indicating a widely occurring riboflavin deficiency. Consumption of alcoholic beverages was not found to be a contributing factor to EC. The results of the present study reveal a deficiency of vitamins in the study populations, but do not indicate that the average nutritional status of the volunteers in Group C was worse than that of Groups NC and F with regard to vitamin A, ascorbate, and riboflavin.

Observations on the epidemiology of oesophageal carcinoma in the province of Trieste

After describing the enormous variation in incidence of oesophageal carcinoma in different populations, the authors report data on the incidence of carcinoma of the oesophagus in the province of Trieste, Italy. There is a high incidence in men, this being among the highest in the world, excluding areas with so-called 'endemic' disease. On the other hand, the incidence in women is low, even compared to other European regions. The epidemiological data reveal in particular that, in the province of Trieste, carcinoma of the oesophagus affects predominantly young and middle aged men. This may be related to high alcohol and tobacco consumption.

Oesophageal cancer in Greenland: selected epidemiological and clinical aspects

During 1955--1974, forty cases of oesophageal cancer were diagnosed among indigenous Greenlanders. The annual incidence rates per 100,000, age adjusted to the "world" population, were 16.3 for males and 11.8 for females in 1955--1964. The corresponding rates in 1965--1974 were 15.9 for males and 6.7 for females with a male:feamle ratio of 2.4:1. These rates rank among the moderately high rates found in India, Puerto Rico and France and in the black population in the US. Age distribution, anatomical location and prognosis followed the normal pattern for oesophageal cancer disease. No particular occupational trend was apparent and there was no difference between towns and settlements. However, a statistically significant geographical gradient of frequency was found with higher rates in the southernmost 3 districts. The traditional Greenland diet may contain concentrations of precursors sufficient to create carcinogenic levels of nitrosamines. Further studies are needed in particular of environmental factors such as foodstuffs, homebrewed beer, drinking water and cigarette smoking. Attention should be focused on the special ecological conditions in southern Greenland.

Environmental factors in cancer of the larynx: a second look

During a retrospective case-control study of recent laryngeal cancer patients, several associated factors were studied to determine possible changes in the epidemiology of laryngeal cancer between 1956 and 1974. The large sex difference noted in the early survey (male: female ratio of 14.9:1) diminished considerably in the present sample (4.6:1) because more women are cigarette smokers in the cancer age group today than was the case 20 years ago. Laryngeal cancer patients tended to be less educated than the controls and included a smaller proportion of Jews and more Catholics than the control group. The risk for developing laryngeal cnacer was considerably lower for exsmokers and long-term (10+ years) filter cigarette smokers as compared with non-filter smokers. At each level of alcohol consumption, the risk increased as exposure to tobacco increased. Occupations associated with wood exposure were found to affect the development of laryngeal cancer, independently of smoking status. Future studies should include an extensive study of nutritional deficiencies associated with alcoholism to determine if a correlation exists between such deficiencies, socioeconomic status, and an increased risk of laryngeal cnacer.