Epithelial lesions antedating oesophageal carcinoma. I. Histologic study in mice

Oesophageal Stem Cells and Cancer

Oesophageal cancer remains one of the least explored malignancies. However, in recent years its increasing incidence and poor prognosis have stimulated interest from the cancer community to understand the pathways to the initiation and progression of the disease.

Critical understanding of the molecular processes controlling changes in stem cell fate and the cross-talk with their adjacent stromal neighbours will provide essential knowledge on the mechanisms that go awry in oesophageal carcinogenesis. Advances in lineage tracing techniques have represented a powerful tool to start understanding changes in oesophageal cell behaviour in response to mutations and mutagens that favour tumour development.

Environmental cues constitute an important factor in the aetiology of oesophageal cancer. The oesophageal epithelium is a tissue exposed to harsh conditions that not only damage the DNA of epithelial cells but also result in an active stromal reaction, promoting tumour progression. Ultimately, cancer represents a complex interplay between malignant cells and their microenvironment. Indeed, increasing evidence suggests that the accumulation of somatic mutations is not the sole cause of cancer. Instead, non-cell autonomous components, coming from the stroma, can significantly contribute from the earliest stages of tumour formation.

The realisation that stromal cells play an important role in cancer has transformed this cellular compartment into an attractive and emerging field of research. It is becoming increasingly clear that the tumour microenvironment provides unique opportunities to identify early diagnostic and prognostic markers, as well as potential therapeutic strategies that may synergise with those targeting tumour cells.

This chapter compiles recent observations on oesophageal epithelial stem cell biology, and how environmental and micro-environmental changes may lead to oesophageal disease and cancer.

Role of the vitamin C in diethylnitrosamine-induced esophageal cancer in Wistar rats

PURPOSE: To evaluate the inhibitory effect of vitamin C on the experimental esophageal carcinogenesis induced by diethylnitrosamine (NDEA). METHODS: Sixty Wistar male rats aged three months, with mean weight of 210 g were employed in the study and were divided into four different groups according to the drinking drugs: group I - controls: only water, seven days a week; group II - only vitamin C, seven days a week; group III - NDEA, three days a week and water during the other four days; group IV - NDEA, three days a week and vitamin C during the other four days; group V - NDEA together with vitamin C three days a week, and only water during the other four days and group VI - NDEA together with vitamin C three days a week and vitamin C during the other four days. The dosages of NDEA were: - 10 mg. / Kg / day and vitamin C - 200 mg / animal / day, dissolved in drinking water. The animals were observed during 180 days and after that each one was sacrificed and its esophagus and the stomach were removed together and macro and microscopically analyzed to identify any tumors. RESULTS: The largest number of tumors was observed in the group III: 48 macroscopic lesions (4.8 lesions per animal) and 23 microscopic lesions (2.3 lesions per animal). The groups that received vitamin C (groups IV, V and VI) showed smaller number of tumors: group V - 0.5 macroscopic lesions and 0.3 microscopic lesions per animal and group VI - 0.1 macroscopic lesions and 0.1 microscopic lesions per animal. The incidence of tumors in the groups V and VI showed statistical significance (p<0.05), when compared to the other groups. CONCLUSION: The vitamin C administered together with diethylnitrosamine showed an inhibitory effect on the experimental esophageal carcinogenesis in Wistar rats.

Morphine does no promote esophageal carcinogenesis in rats exposed to diethylnitrosamine

BACKGROUND

The high incidence of esophageal cancer in the north of Iran has been associated to the consumption of opium and exposure to nitrosamines. Diethylnitrosamine has an established potential of producing experimental cancer in the esophagus and liver.

AIM

To evaluate by histopathology the effect of oral administration of morphine and diethylnitrosamine during 23 weeks on the hepatic and esophageal carcinogenesis on 176 rats.

METHODS

We divided the rats into the following groups: Morph: morphine; Den: diethylnitrosamine; Den+morph: Den and morphine in the same solution; Den/morph: Den and morphine in different solutions and days.

RESULTS

Morphine did not promote neoplasias. The highest neoplastic incidents were found: a) in the esophagus, Den in relation to Den/morph and Den+morph (71.1%, 55.8%, and 50.0%); b) in the liver, Den and Den/morph in relation to Den+morph (73.8%, 81.4%, and 40.9%); c) higher incident of hepatic neoplasia than esophageal in Den/morph (81.4% and 55.8%). Different doses of diethylnitrosamine were ingested among the groups Den, Den/morph, and Den+morph, respectively 2.9, 2.8, and 2.3 mg/kg/day.

CONCLUSIONS

These results show that the morphine did not promote esophageal carcinogenesis and may have stimulated the hepatic metabolism of the first pass of the carcinogen.

Experimental esophageal carcinogenesis: technical standardization and results

The aim of this research was to determine the occurrence of epidermoid carcinoma of the esophagus induced by diethylnitrosamine (DEN) in Wistar rats. DEN was administered (250-300 g) in drinking water (10 mg/kg body weight) to four groups of rats for 72 h/week, for a duration of 90, 120, 150, or 200 days (groups T90, T120, T150, and T200). Ten animals whose drinking water did not contain DEN constituted the control group. All rats were sacrificed and their esophaguses studied macro- and microscopically. The control group did not exhibit either carcinomas or preneoplasic lesions. The T120 and T200 groups presented, respectively, 47 and 58 in situ carcinomas; 1 and 20 submucosal carcinomas (P < 0.05); 4 and 17 microinvasive carcinomas (P < 0.05); 4 and 11 advanced carcinomas (P < 0.05); and 1 and 1 cases of benign hyperplasia. Pulmonary and liver carcinomas were also found in the T200 group. The majority of advanced macroscopic lesions in the T200 group were polypoid, exophytic, and not microscopically invasive in the esophageal wall. This research confirms the effectiveness of the DEN in bringing about carcinogenesis in the Wistar rat esophagus and also shows that the lesions are dosage dependent.

Induction of esophageal carcinogenesis by diethylnitrosamine and assessment of the promoting effect of ethanol and N-nitrosonornicotine: experimental model in mice

It is known that some nitrosamines preferably affect particular organs because of their organospecificity. Diethylnitrosamine (DEN) is one of the most powerful nitrosamines for experimentally inducing esophagus cancer. The present study aimed to evaluate the rate and type of epithelial lesions induced by DEN in mice. We also assessed the role of alcohol and N-nitrosonornicotine (NNN) as promoters of this carcinogenesis. A total of 208 female mice (Mus musculus) were allocated to five experimental groups: group 1, water only (controls); group 2, DEN + water; group 3, DEN + NNN; group 4, DEN + 6% alcohol solution; group 5, DEN + NNN + 6% alcohol solution. Animals in groups 2, 3, 4 and 5 received DEN (0.04 ml/l) three times per week, and during the following 4 days they received the other solutions. NNN was provided at a final concentration of 30 mg/l. The overall experimental period was 180 days. At the end of this time, the animals were killed and their esophagus was dissected for macro- and microscopic analysis. There was no significant difference in relation to the size of the esophagus and to the average DEN intake by the animals (p > 0.05). A statistically significant difference (p < 0.0001) was observed between controls and all other experimental groups. There was no significant difference among experimental groups treated with carcinogens (p > 0.05). The average incidence of cancer was 85.4%. The experimental model used in the present study is a very potent indicator of esophagus cancer. Owing to the high incidence for cancer observed in the present study, it was not possible to assess the effect of alcohol and NNN as inducers for the development of esophageal cancer.

Influence of surgically induced gastric and gastroduodenal content reflux on esophageal carcinogenesis--experimental model in Wistar female rats

Studies in human beings and animals have shown that esophageal exposure to duodenal and gastric contents may be important for the development of Barrett's esophagus and its complications, including adenocarcinoma and epidermoid carcinoma. Diethylnitrosamine (DEN) is a carcinogen that stimulates the development of epidermoid carcinoma in the esophagus of mice. The aim of this study was to evaluate the effect of gastroduodenal and gastric content reflux on induction of esophageal carcinogenesis. Gastroesophageal reflux (GER) and gastroduodenoesophageal reflux (GDER) were produced by cardioplasty and esophagoduodenostomy. The chosen carcinogen was DEN, diluted in drinking water, given 3 days a week for 20 consecutive weeks. One hundred Wistar female rats were divided into six groups, as follows: group 1 (18 rats), cardioplasty without DEN; group 2 (18 rats), cardioplasty with DEN; group 3 (10 rats), only water; group 4 (17 rats), cardioplasty with DEN; group 5 (17 rats), esophagoduodenostomy with DEN; group 6 (20 rats), only DEN. GER in isolation induced papillomatosis or ulceration in 22.2% of rats and, when associated with DEN, induced papillomatosis in 61.1% of rats. GDER in isolation induced marked esophagitis in 61.1% of rats, Barrett's esophagus in 16.7% and esophageal adenocarcinoma in 16.7%; when associated with DEN, 23.5% of rats presented marked esophagitis, papillomatosis or ulceration, whereas 76.5% had esophageal carcinoma, with 70.6% epidermoid carcinoma and 5.9% adenocarcinoma. Rats treated with water alone did not show histologic abnormalities of the esophageal mucosa. Rats treated with DEN alone developed papillomas in 50.0% of the cases and remained histologically unchanged in 50.0%. There was no development of low- or high-grade dysplasia in any group. The conclusions are that (1) GDER is significantly more deleterious to esophageal mucosa than GER; (2) in this study, GER did not present carcinogenic potential in relation to the esophagus; (3) GDER in isolation is an esophageal carcinogen, producing Barrett's esophagus and esophageal adenocarcinoma; (4) esophageal oncogenesis caused by GDER is potentiated by DEN, inducing esophageal epidermoid carcinoma; (5) in this study, DEN in isolation did not generate tumors in the esophagus of rats.

Infrequent Ha-ras mutations and absence of Ki-ras, N-ras, and p53 mutations in 4-nitroquinoline 1-oxide-induced rat oral lesions

The alkylating agent 4-nitroquinoline 1-oxide (4-NQO) is a powerful carcinogen and induces squamous cell hyperplasia, squamous cell dysplasia, papilloma, and squamous cell carcinoma (SCC) in rat oral epithelia. Oral cancers induced by a single application of 4-NQO develop through a multistage process in a way similar to the development of this cancer in humans. In this study, mutations in exons 1 and 2 of Ki-ras, N-ras, and Ha-ras and exons 4-7 of p53 were examined by polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) analysis, followed by PCR-direct sequencing for the confirmation of mutations. Samples for the mutation analysis were obtained from dysplasias, papillomas, and SCCs on the tongue epithelia induced in F344 rats by adding 4-NQO (20 ppm) to their drinking water for 8 wk. The Ha-ras mutations (61A-->T transversions in the second position) were found in five of 29 (17%) samples (one dysplasia and four SCCs). However, no mutations were detected in either Ki-ras, N-ras, or p53 under two different conditions of PCR-SSCP analysis. We suggest that some neoplasms in oral carcinogenesis induced by 4-NQO may involve Ha-ras mutations but not mutations in Ki-ras, N-ras, or p53. The 4-NQO-induced rat oral carcinogenesis model may provide a system for evaluation of the mechanisms of multistage oral carcinogenesis associated with Ha-ras mutation without Ki-ras, N-ras, or p53 mutation.

Interferon-alpha/beta can impede development of carcinogen-induced squamous-cell tumors in the esophagus of C57B1 mice

The effect of treatment with murine interferon-alpha/beta preparations on diethylnitrosamine-induced squamous-cell tumors in the esophagus of C57B1 mice was investigated. Diethylnitrosamine was administered in the drinking water for 18 weeks. Interferon was given intraperitoneally during the same 18 weeks or from the end of the period of carcinogen exposure until termination of the experiment. In mice given interferon and diethylnitrosamine synchronously, a significantly lower tumor index (number of tumors/cm of esophageal mucosa) was observed as compared to all control groups. Treatment with interferon after the administration of the carcinogen was terminated had no effect on the appearance of tumors. These data suggest that interferon therapy can exert certain effects on carcinogenesis.

Efficient and specific induction of esophageal tumors in rats by precursors of N-nitrososarcosine ethyl ester

Cancers and precancerous lesions of the esophagus were efficiently induced in rats by the simulation of a clinico-epidemiological setting; that is, the administration of precursors of nitrosamine. Six week old non-inbred male Wistar rats were given 2g/kg bodyweight of sarcosine ethyl ester hydrochloride (SEEH) and concurrently 0.3g/kg bodyweight of sodium nitrite (NaNO2), precursors of N-nitrososarcosine ethyl ester (NSEE), in 2% sucrose as drinking water. Group 1 received the precursors twice a week for 6 weeks followed by 8 weeks observation, and group 2, once every 3 days for 7 weeks followed by 26 weeks observation. At the end of treatment, no tumor had developed in the esophagus of rats in group 1, but the [3H]-thymidine labeling indices in both basal and superficial layer cells were higher than in the control group. On subsequent observation, papillomas appeared in group 1 (33.3%), and carcinomas in group 2 (33.3%), within 4 weeks. The tumors induced in group 1 were mostly papillomas and rarely carcinomas. When the observation was prolonged in group 2, 100% of the animals had cancer in week 20. The pathological changes of the lesions paralleled the sequential development of human squamous cell carcinoma of the esophagus. Our system has the advantages in that papillomas and cancers can be induced in rats in a short time and the agents used are less toxic than preformed nitrosamines administered previously by gastric intubation. It would serve as a useful experimental tool to study premalignant lesions and cancers of the esophagus.

Inhibitory effects of the natural products indole-3-carbinol and sinigrin during initiation and promotion phases of 4-nitroquinoline 1-oxide-induced rat tongue carcinogenesis

The modifying effects of indole-3-carbinol (I3C) and sinigrin (SIN) on the initiation and post-initiation phases of tongue carcinogenesis induced by 4-nitroquinoline 1-oxide (4-NQO) were investigated in male ACI/N rats. Rats were divided into eight groups: group 1 was given 4-NQO (10 ppm) in the drinking water for 12 weeks, starting at 7 weeks of age; groups 2 and 3 were given 4-NQO and fed the diets containing I3C (1,000 ppm) and SIN (1,200 ppm) for 14 weeks, respectively, starting at 6 weeks of age; groups 4 and 5 were given 4-NQO and then they were fed I3C and SIN containing diets for 23 weeks, respectively, starting one week after 4-NQO exposure; groups 6 and 7 were given I3C and SIN alone, respectively, during the experiment; group 8 served as an untreated control. At the termination of the experiment (week 37), the incidence of tongue neoplasms (squamous cell papilloma and carcinoma) in group 2 (1/15, 7%), group 3 (1/15, 7%), group 4 (3/15, 20%) or group 5 (2/15, 13%) was significantly smaller than that in group 1 (12/17, 71%) (P = 0.0003, P = 0.005 or P = 0.002). No tongue carcinomas developed in rats of groups 2, 3, and 5. Similarly, the incidence of preneoplastic lesions (hyperplasia and dysplasia) of the tongue in group 2 (11/15, 73%), group 3 (10/15, 67%), group 4 (11/15, 73%) or group 5 (10/15, 67%) was significantly lower than that in group 1 (17/17, 100%) (P = 0.04 or P = 0.02). There were no tongue neoplasms in rats of groups 6, 7, and 8. Administration of I3C and SIN also caused significant decreases in the number and area of silver-stained nucleolar organizer regions protein (AgNORs), a new cell proliferation index, of tongue squamous epithelium. Thus, I3C and SIN inhibited rat tongue carcinogenesis in both the initiation and post-initiation phases, when administered in these respective phases together with, or following treatment with, 4-NQO.

Spontaneous squamous carcinoma of the esophagus in chickens

Histologic preparations from 149 gullets from chickens from the Linxian county (Henan province, northern China) having intraepithelial neoplasms or invasive carcinomas were reviewed. Invasive squamous cell carcinomas were found in 134 animals and invasive adenocarcinomas in seven. The remaining eight specimens had only intraepithelial neoplastic lesions: four with low-grade dysplasia and four with high-grade dysplasia (one with carcinoma in situ). The degree of differentiation in invading tumors was as follows: of the 134 invasive squamous carcinomas, two were highly differentiated, 125 moderately differentiated, and 22 poorly differentiated. All seven adenocarcinomas were moderately differentiated. In 97 of the 149 invasive carcinomas, intraepithelial neoplastic lesions were observed near the tumors: in 96 adjacent to invasive squamous carcinoma, and in one in the glandular epithelium adjacent to invasive adenocarcinoma. In the remaining 44, only invasive carcinoma was present. Epithelial buds bulging into the stroma were present in intraepithelial neoplastic lesions: in 71.8% in low-grade dysplasias adjacent to invasive carcinoma and in 94.4% in high-grade dysplasias adjacent to invasive carcinoma. Moreover, two of the four animals with low-grade dysplasia exclusively, and the four with high-grade dysplasia (one with carcinoma in situ) also had epithelial buds. In two specimens, invasive carcinoma was found to originate at the tip of the irregular buds with dysplasia. Similar histologic events have been found in chemically induced squamous esophageal carcinomas in rodents and in early squamous carcinoma in humans. It is therefore suggested that there is a close association between the degree of squamous cellular atypia, the formation of epithelial buds, and the progression toward invasive carcinoma in the esophagus.

Inhibitory effects of non-steroidal anti-inflammatory drugs, piroxicam and indomethacin on 4-nitroquinoline 1-oxide-induced tongue carcinogenesis in male ACI/N rats

The effects of the non-steroidal anti-inflammatory drugs (NSAIDs), piroxicam and indomethacin on 4-nitroquinoline 1-oxide-(4-NQO)-induced tongue carcinogenesis in male ACI/N rats were examined. Rats were given 4-NQO (10 ppm) in the drinking water for 12 weeks and followed by either diet containing 150 ppm piroxicam or the drinking water containing 10 ppm indomethacin for 24 weeks. The incidence of tongue neoplasms (squamous cell papilloma and carcinoma) in rats given 4-NQO plus piroxicam (4/13, 31%) and those given 4-NQO plus indomethacin (3/13, 23%) were significantly lower than that of animals given 4-NQO alone (12/17, 71%) (P less than 0.05 and P less than 0.005). Rats given piroxicam or indomethacin alone had no neoplasms in the tongue. Thus, piroxicam and indomethacin significantly inhibited the development of tongue neoplasms in male ACI/N rats.

Seventh-Day Adventist vegetarians have a quiescent proliferative activity in colonic mucosa

The proliferation of epithelial cells in colonic mucosa was studied in humans at varying degrees of risk for colon cancer. Seventh-Day Adventist vegetarians, known to have significantly lower mortality from colon cancer than the general U.S. population, had the most quiescent proliferative activity of mucosal epithelial cells. Increased replication and expansion of the proliferative compartment accompanied increased colon cancer risk. The analytical methods of this study may be useful in assessing the influence of dietary components involved in the initiation, promotion or inhibition of colon cancer, and in developing strategies for nutritional intervention.