MDR3 immunostaining on frozen liver biopsy samples is not a sensitive diagnostic tool for the detection of heterozygous MDR3/ABCB4 gene mutations

Abstract

Dear Editor, We read with great interest the recent article of Wendum et al. [1] describing histological lesions observed in the liver of 13 adult patients with heterozygous MDR3/ABCB4 gene mutations. They performed multidrug resistance Pglycoprotein 3 (MDR3) immunostaining on formalin-fixed paraffin-embedded sections of 11 patients and reported that the staining had a diffuse and strong canalicular pattern in patients and controls, except in one case who disclosed a faint staining. This finding suggested a lack of sensitivity of this technique for the diagnosis of MDR3/ABCB4 heterozygous mutations. Since we previously suggested that MDR3 immunostaining on frozen liver sections could be useful for the diagnosis of unexplained anicteric cholestasis in adult patients [2], we would like to contribute by providing our experience of MDR3 immunostaining realized on frozen liver biopsy sections of a new series of adult patients with MDR3/ABCB4 mutations. Between April 2007 and March 2011, 32 adult patients with unexplained anicteric cholestasis had ABCB4 gene sequencing, using polymerase chain reaction amplification and DNA sequencing of exons 2 to 28 and all splice junctions. Among these 32 patients, ten carried six different ABCB4 mutations. These ten patients (six females, 17– 72 years of age) displayed various clinical characteristics: three fulfilled the criteria for low phospholipid-associated cholelithiasis syndrome [3]; one had an anteriority of intrahepatic cholestasis of pregnancy; and six had an unexplained anicteric cholestasis—two of them with associated elevated aminotransferase level. Histopathological analysis using Picrosirius red and hematoxylin–eosin-stained liver biopsy sections showed that nine patients had portal fibrosis (three F1, four F2, one F3, and one F4 according to Ishak fibrosis score); six of them displaying a jigsaw pattern of biliary-type fibrosis. Bile duct lesions corresponding to mild cholangitis could be observed in four patients. Ductopenia, defined as a loss of more than 50 % of bile ducts, was seen in two patients. Lastly, six cases showed a mild to moderate ductular reaction. The clinicopathological features are detailed in Table 1. Frozen liver biopsies were available for 14 patients (five cases and nine controls). Immunohistochemistry was performed on 4-μm frozen sections by using MDR3 monoclonal antibody (clone P3II-26) and MRP2 antibody (clone M2III-6) as a control to check tissue immune reactivity. As shown in Fig. 1, we observed a diffuse and intense canalicular staining with MDR3 antibody, in the available frozen liver biopsies of the five patients with heterozygous ABCB4 mutations and in the nine controls. Positive canalicular staining was also observed with MRP2 antibody, confirming the immunoreactivity of our samples. These results are in contradiction with our previous report [2] in which no or faint MDR3 immunostaining was observed in frozen liver biopsies from four patients with A. Sannier (*) :M. Tepper :M. Ziol Service d’Anatomie Pathologique, GHU Paris-Seine-Saint-Denis, Hopital Jean Verdier, AP-HP, Avenue du 14 Juillet, 93143 Bondy Cedex, France e-mail: aureliesannier@free.fr