Effect of dipyridamole on fluorodeoxyuridine cytotoxicity in vitro and in cancer patients

Summary Dipyridamole (DP) has previously been studied both in vitro and in vivo in combination with various antimetabolites, including methotrexate and 5-fluorouracil (5FU). We evaluated in vitro and clinically the effects of adding DP to fluorodeoxyuridine (FUDR) in colorectal cancer. Using a human colony-forming assay, we observed that 0.05 M DP increased the cytotoxicity of FUDR by a median of 33.5-fold vs 1.5-fold for 5FU against human colon-cancer cell lines. The mechanism of the DP-enhanced antitumor activity of FUDR is not completely understood but appears to be related to a profound inhibition by DP of thymidine accumulation in and FUDR efflux from colon-cancer cell lines. On the basis of these in vitro results, 28 patients with metastatic colon cancer were entered in a clinical trial of monthly courses of 0.1 mg/kg FUDR daily for 14 days and 75 mg oral DP 5 times daily for 14 days starting on the 3rd day of continuous i.v. FUDR infusion. The pharmacokinetics of DP was studied in three patients; the results showed that 98% of total serum DP was protein-bound and that free DP levels were significantly lower than the concentrations necessary for the expected in vitro DP/FUDR modulation. Treatment was well tolerated, with only 12 patients developing mild to moderate toxicity. Of 27 evaluable patients, 4 achieved a partial response that lasted 2, 3, 5, and 6+ months. This relatively low response rate (15%), which is similar to that achieved with FUDR alone, may be explained by the low steady-state plasma concentrations of free DP achieved in our patients. Other means of DP administration, such as i.v., i.a., and i.p. injection, may be required to achieve free DP concentrations necessary for successful biochemical modulation of FUDR in patients.Supported in part by grants CA17094, CA23074, and CA39629 from the National Institutes of Health, Bethesda, Md 20205, and a grant from the Arizona Chronic Disease Commission. HSG is a recipient of an American Cancer Society Career Development Award     

Splenectomy in a case of splenic vein thrombosis unmasks essential thrombocythemia

We report a patient with splenic vein thrombosis (SVT) in whom splenectomy resulted in the unmasking of essential thrombocythemia (ET). He had portal hypertension with haematemesis, resulting in anaemia requiring repeated blood transfusions. Investigations revealed SVT. Following splenectomy, he suffered a transient ischaemic attack episode, associated with persistent thrombocytosis (> 2000 x 10(9)/l). Other myeloproliferative disorders were excluded and a diagnosis of ET was established. He responded to hydroxyurea but, due to financial constraints, he discontinued treatment and subsequently relapsed. The association of ET with SVT is rare and the diagnosis of ET was missed initially as the platelet count was normal prior to splenectomy.     

Ornithine decarboxylase activity in Barrett's esophagus: a potential marker for dysplasia

Ornithine decarboxylase activity is known to be increased in certain premalignant conditions. We determined the activity of this enzyme in mucosal biopsy specimens from 15 patients with Barrett's esophagus. Ornithine decarboxylase was greater in Barrett's mucosa than in squamous esophageal or gastric mucosa. In Barrett's mucosa from 4 patients with dysplasia, the enzyme activity was greater than in 11 patients without dysplasia (1.6 +/- 0.35 vs. 0.19 +/- 0.08 U/mg protein; p less than 0.005). Increased ornithine decarboxylase activity in biopsy specimens of Barrett's mucosa may represent a marker for dysplasia.     

Correlation of gastroesophageal reflux disease symptoms characteristics with long-segment Barrett''s esophagus

Thus far, there has been a paucity of studies that have assessed the value of the different gastroesophageal reflux disease (GERD) symptom characteristics in identifying patients with long-segment Barrett's esophagus versus those with short-segment Barrett's esophagus. To determine if any of the symptom characteristics of GERD correlates with long-segment Barrett's esophagus versus short-segment Barrett's esophagus. Patients seen in our Barrett's clinic were prospectively approached and recruited into the study. All patients underwent an endoscopy, validated GERD symptoms questionnaire and a personal interview. Of the 88 Barrett's esophagus patients enrolled into the study, 47 had short-segment Barrett's esophagus and 41 long-segment Barrett's esophagus. Patients with short-segment Barrett's esophagus reported significantly more daily heartburn symptoms (84.1%) than patients with long-segment Barrett's esophagus (63.2%, P = 0.02). There was a significant difference in reports of severe to very severe dysphagia in patients with long-segment Barrett's esophagus versus those with short-segment Barrett's esophagus (76.9%vs. 38.1%, P = 0.02). Longer duration in years of chest pain was the only symptom characteristic of gastroesophageal reflux disease associated with longer lengths of Barrett's mucosa. Reports of severe or very severe dysphagia were more common in long-segment Barrett's esophagus patients. Only longer duration of chest pain was correlated with longer lengths of Barrett's esophagus.     

Crypt-restricted loss and decreased protein expression of cytochrome C oxidase subunit I as potential hypothesis-driven biomarkers of colon cancer risk.

There is an increasing demand for the development of intermediate biomarkers to assess colon cancer risk. We previously determined that a live cell bioassay, which assesses apoptosis resistance in the nonneoplastic colonic mucosa, detects approximately 50% of patients with colon cancer. A hypothesis-driven biomarker that reflects apoptosis resistance in routine formalin-fixed, paraffin-embedded tissue would be easier to use. Cytochrome c oxidase is a critical enzyme that controls mitochondrial respiration and is central to apoptosis. We did an immunohistochemical study of cytochrome c oxidase subunit I expression in 46 colonic mucosal samples from 16 patients who had undergone a colonic resection. These included five patients without evidence of colonic neoplasia (three normal and two diverticulitis), three patients with tubulovillous adenomas, and eight patients with colonic adenocarcinomas. Analysis of aberrancies in expression of cytochrome c oxidase subunit I showed that, compared with nonneoplasia, the patients with neoplasia had a higher mean incidence of crypts having decreased expression (1.7 versus 22.8, P = 0.03) and a higher mean incidence having crypt-restricted loss (0.6 versus 3.2, P = 0.06). The percentage with segmented loss was low and was similar in the two groups. Combining these results, the mean % normal (i.e., with none of the three types of abnormality) was 96.7 in nonneoplasia versus only 73.2 in patients with neoplasia (P = 0.02). It should be noted that a defect in cytochrome c oxidase subunit I immunostaining was not detected in all biopsy samples from each patient for whom some abnormality was found, indicating a "patchiness" in the cytochrome c oxidase subunit I field defect. As a result of this "patchiness," the increased variability in the incidence of crypt-restricted loss of cytochrome c oxidase subunit I expression was a statistically significant feature of the neoplasia group. Crypt-restricted loss of cytochrome c oxidase subunit I has not been previously reported in colonic mucosa and is presumably the result of a crypt-restricted stem cell mutation. Decreased cytochrome c oxidase subunit I expression also significantly correlated with apoptosis resistance, a factor known to contribute to carcinogenesis. The results suggest, however, that aberrant cytochrome c oxidase subunit I expression may be a better biomarker than loss of apoptosis competence for increased colon cancer risk.