Primary Motility  Disorders of the  Esophagus
 The Esophageal
 Mucosa
 The
 Esophagogastric  Junction
 Barrett's
 Esophagus

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OESO©2015
 
Volume: Barrett's Esophagus
Chapter: Markers
 

Can decrease or loss of expression of intestinal markers (Villin) be correlated with development of dysplasia or adenocarcinoma?

R. Lascar, R.C. Fitzgerald, G. Triadafilopoulos (Detroit, London, Palo Alto, Stanford)

Villin is a cytoskeletal actin-binding protein (Mr 95 kDa) that is universally expressed in small intestinal microvilli and serves as an early marker of intestinal differentiation. Combined electron microscopic and immunoblotting studies have shown that Villin expression correlates well with appearance of microvilli in intestinal cells. Therefore, Villin could serve as a useful marker of intestinal differentiation in the premalignant Barrett's mucosa, characterized by specialized intestinal metaplasia (IM).

Villin as a marker of differentiation in Barrett's esophagus

In a study of 23 Barrett's esophagus patients, Villin expression was noted in the Barrett's biopsies in all but 7 patients. Densitometric analysis of the Villin bands from these patients showed variable Villin expression when compared with expression in the duodenum of the same patients. Villin expression ranged from 0% to 67% of duodenal expression. Ultrastructural studies revealed that Villin expression correlates very well with formation of microvilli on the surface of the metaplastic epithelium. Detailed mapping studies evaluating Villin expression in different areas of the Barrett's epithelial surface have revealed focal molecular heterogeneity [1]. There is dissociation between Villin expression by immunoblotting and the presence of IM, including mild dysplasia. This emphasizes the focal and random micro-heterogeneity of Villin expression at the molecular level, which certainly cannot be appreciated at the light microscopy level.

Villin expression with continuous acid exposure in ex vivo organ culture

Acid exposure has a dynamic effect on Villin expression and, in turn, cell differentiation. This was demonstrated when we performed organ culture experiments in media that was titrated to a pH range of 1-12, and then assessed Villin expression as a marker of intestinal cell differentiation [2]. After 24-hours of explant culture, induction of Villin expression was noted in Barrett's esophagus samples incubated at a pH range of 3-5, and found to be maximal at pH 3.5. In contrast, Villin expression in the duodenum was reduced at pH extremes. Overall, after continuous exposure to acid (pH 3.5), Villin expression increased to 50% and 82% of Barrett's esophagus samples after 6 and 24 culture hours, respectively. Such increased Villin expression correlated with ultrastructural maturation of the brush border on Barrett's esophagus cells.

Figure 1. Cell differentiation as determined by Villin immunoblotting in 2 groups of Barrett's esophagus patients at baseline and after 6 months of proton pump inhibitor therapy. On the y-axis, Villin score represents densitometry units over duodenum used as internal standard for each patient. A. Data on group A (normal intraesophageal pH profile). B. Data on group B (pathological intraesophageal pH profile). At 6 months, there is a significant increase in Villin expression in group A and no change in group B (from [3]).

Relationship of Villin expression to dysplasia

In a recent study, endoscopic biopsy specimens from 42 Barrett's esophagus patients, including 14 patients with dysplasia, were analyzed before and after 6 months of treatment with lansoprazole at daily doses of 15 to 60 mg [3]. When completely asymptomatic on proton pump inhibitor (PPI) therapy, the patients underwent 24-hour ambulatory pH monitoring. Patients were grouped according to whether they had normalization of intraesophageal pH or abnormal esophageal acid exposure. The groups were comparable with regard to patients demographics, magnitude of reflux symptoms before therapy, Barrett's esophagus segment length, presence and size of hiatal hernia, and manometric characteristics. Endoscopy specimens were analyzed for the cell proliferation marker proliferating cell nuclear antigen (PCN) and the differentiation marker Villin. In the group of patients with normalized intraesophageal pH, PCNA expression declined significantly from a median of 22% of cells to 4.8% of cells and Villin expression increased significantly by 4-fold. In contrast, PCNA and Villin expression were essentially unchanged in the group with persisting abnormal esophageal acid exposure. There was a strong negative correlation between Villin and PCNA expression in these biopsy specimens (r = - 0.79). In the subset of patients with dysplasia, PCNA expression was strongly correlated with the degree of dysplasia (r = 0.76), but Villin expression was unrelated. These findings indicate that dysplasia is unrelated to cell differentiation but strongly correlates with cell proliferation.

Despite a favorable effect on Villin expression, this study did not find a significant reduction in dysplasia with normalization of intraesophageal acid exposure during the 6month study period. Low-grade dysplasia (LGD) was present at baseline in four patients of the group with normalized acid exposure; it resolved in three patients and persisted in the other patient after 6 months of PPI therapy. However, indefinite dysplasia and LGD each developed in one patient. In the group with abnormal acid exposure, 1 patient had highgrade dysplasia (HGD) and 3 patients had LGD; at 6 months, dysplasia resolved in the patient with HGD and progressed to HGD in 1 patient, became indefinite in 1 patient, and regressed in 1 patient with LGD at baseline. In addition, LGD developed in 1 patient from this group. It may have been that the study duration was too short and the patients too few to yield meaningful data on the effects of reduced cell proliferation and increased differentiation on dysplasia.

Villin expression in esophageal adenocarcinoma

To evaluate the association of Villin as a marker of cell differentiation with adenocarcinoma of the esophagus we studied 4 patients with adenocarcinoma [1]. Compared with Villin expression in the duodenum, Villin expression in the cancers was absent in 3 and very low in 1. In contrast, immunoblot analysis for another glandular epithelial marker Ep-CAM, which serves as a homophilic, cell-cell adhesion molecule was easily detectable in all samples. Hence, Villin expression may inversely correlate with the progression to esophageal adenocarcinoma.

Conclusion

Although Villin is a reliable marker for cell differentiation in Barrett's esophagus, the precise role of Villin expression in dysplasia or cancer formation are still unclear and more studies are needed.

References

1. Kumble S, Fajardo L, Omary MB,Triadafilopoulos G. Multifocal heterogeneity in Villin and Ep-CAM expression in Barrett's esophagus. Int J Cancer 1996;66:48-54.

2. Fitzgerald RC, Omary MB, Triadafilopoulos G. Dynamic effects of acid on Barrett's esophagus: an ex vivo proliferation and differentiation model. J Clin Invest 1996;98:2120-2128.

3. Ouatu-Lascar R, Fitzgerald RC, Triadafilopoulos G. Differentiation and proliferation in Barrett's esophagus and the effects of acid suppression. Gastroenterology 1999;117:327-335.


Publication date: August 2003 OESO©2015