Polyamines in gastrointestinal cancer

Pattern and concentration of free and acetylated polyamines in urine of cirrhotic patients

The pattern and concentration of urinary, free, monoacetylated and total polyamines were determined in 31 cirrhotic patients, divided into three classes according to Child's classification, and in 28 healthy subjects.

Cirrhotic patients had increased levels of free, monoacetylated and total polyamines. They also showed a significant increase in N1-acetylspermidine to N8-acetylspermidine molar ratio. Urinary polyamine excretion was not related to the severity of liver disease nor to the values of laboratory liver function tests. Furthermore, polyamine excretion was not significantly different in cirrhotics with or without diabetes or IGT, while plasma insulin and glucagon levels were increased in all cirrhotic patients.

The results suggest that enhanced polyamine biosynthesis and catabolism, particularly N1-acetylation, occur in cirrhotic patients, probably due to hepatic regeneration and/or increased levels of insulin and glucagon.

Review article: chemoprevention of colorectal cancer

Colorectal cancer is a disease with a high mortality at present, due to the late stage at which many cases present. Attention is therefore focusing on preventative strategies for colorectal cancer given that polyps appear to be identifiable and treatable precursor lesions of this disease. Endoscopic polypectomy has been shown to reduce the incidence of colorectal cancer and there is a good case for endoscopic screening of the general population. However, this will require a large amount of manpower and resources and its success will also depend on the overall compliance of the population. Epidemiological studies have shown that individuals reporting a regular intake of aspirin and other non-steroidal anti-inflammatory drugs have a reduced risk of developing colorectal polyps and cancer. Similarly, a number of natural substances, such as calcium and folate, when supplemented regularly in the diet, have also been linked to a possible decreased incidence of colorectal cancer. This has led to the concept of using such agents to reduce the number of cases of colorectal cancer. In this article, we review the current evidence for the use of these and other agents for the chemoprevention of colorectal cancer, together with theories as to their possible mechanisms of action.

A novel cytotoxic agent for human carcinoid tumors

BACKGROUND

Conventional adjuvant therapy for advanced carcinoid tumors remains disappointing; novel therapeutic agents are needed. We have shown previously that inhibiting polyamine biosynthesis with alpha-difluoromethylornithine (DFMO) slows the growth of carcinoid tumors. However, the clinical utility of DFMO has been limited by its cytostatic property. Synthetic polyamine analogs such as 1,19-bis(ethylamino)-5,10,15-triazanonadecane (BE-4-4-4-4) appear to be cytotoxic against several human tumors. The purpose of our study was to determine whether BE-4-4-4-4 is a more effective antiproliferative and cytotoxic agent than DFMO on human carcinoid (BON) cells in vitro.

METHODS

BON cells were treated with either 5 mmol/L DFMO, 0.5 to 10 mumol/L BE-4-4-4-4, or vehicle (control). Ornithine decarboxylase activity was determined by the rate of 14CO2 production, and intracellular polyamine levels were determined by chromatography. Cell number and viability were determined by Coulter counter and trypan blue exclusion, respectively.

RESULTS

BE-4-4-4-4 inhibited ornithine decarboxylase activity and depleted all 3 polyamines. BE-4-4-4-4 decreased cell numbers by 81% compared with control and 27% compared with DFMO. BE-4-4-4-4 also induced a 2-fold increase in cell death compared with control or DFMO.

CONCLUSIONS

BE-4-4-4-4 is cytotoxic and more effective than DFMO in inhibiting growth of BON cells. Polyamine analogs such as BE-4-4-4-4 may be effective adjuvant therapeutic agents for advanced carcinoid tumors.

Biochemical tests in diseases of the intestinal tract: their contributions to diagnosis, management, and understanding the pathophysiology of specific disease states

Biochemical testing plays a major role in the complete evaluation of patients with suspected or established intestinal disease. We have classified these tests according to the medium in which they are performed: breath tests, including isotopic and nonisotopic tests, fecal tests, urine tests, serum tests, tissue tests, and other tests. The principles of various tests are outlined, and the role of each test in the evaluation of particular gastrointestinal disorders is discussed.

Polyamine levels and ODC activity in intestinal-type and diffuse-type gastric carcinoma

Gastric carcinomas are divided into two types according to Lauren's classification: intestinal and diffuse types. Polyamines (putrescine, spermidine, and spermine) are polycations involved in neoplastic growth of gastrointestinal mucosa. A key role is also played by ornithine decarboxylase, the rate limiting enzyme in polyamine metabolism. Our aim was to investigate whether there were differences between the two types of tumor in polyamine metabolism. Twenty-seven patients with gastric carcinoma entered the study. Seventeen carcinomas were classified as diffuse type and 10 as intestinal type. Polyamine levels were evaluated by high-performance liquid chromatography. Ornithine decarboxylase activity was measured by a radiometric technique. Polyamine levels and ornithine decarboxylase activity were significantly higher in intestinal type samples than diffuse type samples. A similarity of polyamine levels in intestinal type samples with levels previously observed in patients with colorectal adenocarcinoma was also found. These findings show a different proliferative behavior of these two types of tumor, and therefore different therapeutic strategies can be hypothesized.

Duodenogastric reflux and foregut carcinogenesis

Epidemiologic cohort studies have established that after distal gastric resection, there is a higher risk of gastric carcinoma. It is likely that a main factor of this higher risk is the excessive duodenogastric reflux induced by surgery, because the incidence of stump carcinomas is higher in Billroth II than in Billroth I, and most of the stump carcinomas are located near the stoma. In addition, several groups of investigators have suggested that duodenogastric reflux per se induces stump carcinomas in rats. There is another human duodenogastric reflux, the primary duodenogastric reflux, through the pylorus. Experiments in animals have demonstrated that this type of duodenal reflux also induces gastric carcinomas in the antrum of the stomach that has not undergone surgery. Recent clinical attention has focused on the role of duodenogastric reflux in the pathogenesis of Barrett's esophagus and subsequent esophageal adenocarcinomas. Experimentally, reflux of duodenal contents into the esophagus can cause not only Barrett's esophagus and subsequent adenocarcinomas, but also squamous cell carcinomas. These findings suggest that duodenogastric reflux may be implicated in gastric and esophageal, that is, foregut carcinogenesis.

Ornithine decarboxylase (ODC) levels in children with reflux esophagitis

Reflux esophagitis is a common disease in infants and can be diagnosed largely by esophageal biopsy. In adults, chronic esophagitis may lead to Barrett's esophagus, a premalignant condition for esophageal cancer development. Ornithine decarboxylase (ODC) is used as an early marker for colon cancer development. No data are available on the role of ODC in reflux esophagitis in the pediatric population. In this study we retrospectively analyzed ODC activity in esophageal biopsies of children who underwent upper endoscopy. According to the esophageal histology, patients were divided into three groups: normal mucosa, mild, and moderate/severe esophagitis. None of our patients had esophageal metaplasia or cancer. ODC level was significantly higher in the moderate/severe esophagitis group compared to mild and normal mucosa group. We conclude that ODC activity is directly proportional to the severity of the esophageal inflammation/regenerative process in children with reflux esophagitis.

Polyamines, diamine oxidase, and ornithine decarboxylase activity in colorectal cancer and in normal surrounding mucosa

We investigated the polyamine levels [putrescine (Put), spermidine (Spd), and spermine (Spm)] and their metabolism by simultaneously considering the ornithine decarboxylase (ODC) and diamine oxidase (DAO) activities in human colorectal cancer and in normal surrounding tissue. Single and total polyamine levels were significantly higher in the neoplastic tissue than in the surrounding mucosa from the same patients. Furthermore, the ODC activity was significantly higher and the DAO activity significantly lower in the neoplastic tissue than in the surrounding mucosa. Polyamine levels and enzymatic activities did not correlate with the clinical and histologic characteristics of patients. In normal tissue samples, no correlation was found between single and total polyamine levels and enzymatic activities (both DAO and ODC). On the contrary, in colorectal neoplastic samples, significant and positive correlations were found between the levels of total polyamines, Spd, and Spm and the ODC activity. In the same specimens, DAO activity was related to Spd levels and the Spd/Spm ratio, but, in those cases, the correlation was negative. Thus, our findings suggest that, during the neoplastic growth of the colorectal mucosa, the balance between polyamine degradation and biosynthesis is disengaged from the control exerted by the two enzymes.

Mucosal polyamine metabolism in the columnar lined oesophagus

Mucosal ornithine decarboxylase activity and polyamine content has been proposed as a possible marker for malignant potential in gastrointestinal mucosa. Polyamine content and histological findings were examined in 107 pairs of endoscopic biopsy specimens taken from gastric fundus, fundic and specialised Barrett's oesophagus and Barrett's adenocarcinoma. The content of putrescine (median nmol/mg protein, range) the primary product of ornithine decarboxylase showed a progressive increase from gastric fundus (0.41, 0.15-1.5); fundic (0.45, 0.01-4.08); specialised Barrett's oesophagus (0.54, 0.01-2.0); dysplastic columnar lined oesophagus (0.56, 0.31-3.1) to adenocarcinoma (1.23, 0.29-8.98). Adenocarcinoma putrescine content was significantly greater than gastric fundus (p < 0.018) and fundic (p < 0.03). Mucosal spermine, spermidine, and total polyamine values were greater in gastric fundus than fundic, specialised Barrett's oesophagus, and dysplastic columnar lined oesophagus (all p < 0.001) suggesting failure to further metabolise putrescine to its higher polyamines in the metaplastic epithelium. Although metaplastic columnar lined oesophagus shows significant differences in polyamine metabolic activity from the stomach the important distinction between specialised and dysplastic columnar lined oesophagus cannot be made by measuring the polyamine content.

Studies of growth regulation in a neuroendocrine cell line

Studies of growth-regulation of neuroendocrine cells have been hampered by a lack of suitable in vitro models. We established and have maintained a functioning human pancreatic carcinoid cell (BON) line. BON cells synthesize and secrete several growth factors. Among those, we have found that serotonin stimulates growth of BON cells through specific receptors linked to cyclic AMP pathway. In this study, effects of other growth factors on growth and serotonin release, and the effects of serotonin and TGF-beta 1 on the polyamine biosynthetic pathway, were examined. TGF-beta 1 inhibited both growth and serotonin release in a dose-dependent fashion. Basic FGF stimulated growth, but failed to affect serotonin release. Other peptide growth factors had no effect on either growth or serotonin release. Serotonin stimulated ODC enzyme activity, but TGF-beta 1 failed to affect ODC enzyme activity. These findings suggest that growth of neuroendocrine cells can be delicately regulated by their own products in an autocrine fashion.

Sodium butyrate stimulates polyamine biosynthesis in colon cancer cells

Differentiation inducers act through polyamine-dependent and independent pathways. Sodium butyrate (NaB) inhibits proliferation and induces terminal differentiation in human and murine cancer cell lines. An effect of this agent on polyamine biosynthesis has not been demonstrated previously. In the present study, we examined the effects of NaB on polyamine biosynthesis in mouse colon cancer (MC-26) cells. All studies were performed on exponentially growing cells, and ODC and polyamine transport measurements were performed as described previously. NaB inhibited the growth of MC-26 cells in a dose-dependent manner. Cell shape was significantly altered by treatment with NaB (development of dendritic-like processes and flattening and spreading out of cells on culture dishes). NaB stimulated ODC activity in a dose-dependent manner. The activity was elevated by 8 h after treatment, and at 48 h there was a ten-fold increase in activity (compared with control activity). The increase in ODC activity led to an increase in polyamine biosynthesis; putrescine, spermidine, and spermine levels in MC-26 cells were significantly elevated by 24 h after treatment with NaB. Polyamine uptake was similar in control cells and cells treated with NaB alone. Our finding of significant stimulation of polyamine uptake by NaB after inhibition of endogenous synthesis (by an ODC-dependent pathway) in DFMO-treated cells suggests that cellular requirements are increased for polyamines in NaB-treated cells. We conclude that polyamine-dependent processes are important in the mechanism of action of NaB in colon cancer cells.

Polyamine levels, ornithine decarboxylase (ODC) activity, and ODC-mRNA expression in normal and cancerous human colonocytes

Ornithine decarboxylase (ODC) and polyamines (putrescine, spermidine, and spermine) are crucial for cell proliferation. Recently, elevated ODC activity and polyamine levels have been suggested as biological markers for human colon cancer. In this study, we measured ODC activity and the levels of polyamines (putrescine, spermidine, spermine, and cadaverine) and acetyl-putrescine in human colonocytes isolated from cancerous areas compared to the adjacent normal colon tissue. In addition, ODC mRNA expression was compared between both groups. We found that colonocytes isolated from cancerous areas had significantly higher mean value of ODC activity, putrescine, spermidine, spermine, and cadaverine levels up to 1480%, 470%, 260%, 380%, and 510% respectively compared to colonocytes isolated from the adjacent normal colonic mucosa. No difference was found in acetyl-putrescine levels between cancerous and normal colonocytes. Steady-state levels of ODC mRNA were slightly elevated in cancerous colonocytes relative to normal colonocytes in two of three paired samples. However, the increase in ODC mRNA levels is not sufficient to account for the increase in ODC activity suggesting that colonocyte ODC activity is regulated post-transcriptionally.

Putrescine and spermidine uptake is regulated by proliferation and dexamethasone treatment in AR4-2J cells

Polyamines are essential for cell growth and differentiation. Their specific uptake contributes to the regulation of intracellular polyamine levels. In this study, we describe the modulation of this transport mechanism in a rat tumoral pancreatic acinar cell line (AR4-2J) and analyze the transport system characteristics of the normal rat pancreatic acini. Normal acini had a common carrier for spermidine and spermine, like AR4-2J cells, but not a specific putrescine carrier. Intracellular polyamine deprivation enhanced putrescine and spermidine uptake of AR4-2J cells with no modification of polyamine carrier affinity. Uptake was modulated during growth and decreased for both polymaines at confluence. AR4-2J cell differentiation with dexamethasone prevented cell proliferation and diminished uptake of both putrescine and spermidine without affecting their respective carrier affinities. Our data show, first, that the polyamine transport system could be modulated by polyamine metabolism with no change in its affinity characteristics. Second, in rat pancreatic acinar cells, neoplastic transformation was partly characterized by induction of a high-affinity putrescine carrier. This phenotype was not reversed by dexamethasone-induced cell differentiation.