Immunohistochemical Mapping of Bcl9 Using Two Antibodies that Recognize Different Epitopes Is Useful to Characterize Juvenile Development of Hepatocellular Carcinoma in Myanmar

Abstract

B-cell lymphoma 9 (Bcl9) is the core component of Wnt/β-catenin signaling and overexpressed in nuclei of various tumors, including hepatocellular carcinoma (HCC). However, the extent of Bcl9 expression relative to HCC differentiation stage and its functional aspects are poorly understood. In this study, we examined the expression pattern of Bcl9 immunohistochemically, using two anti-Bcl9 antibodies; one was a conventional polyclonal-antibody (anti-Bcl9ABC) against amino acid no.800–900 of human-Bcl9, while the other (anti-Bcl9BIO) was against amino acid no.50–200, covering Pygopus-binding sites of Bcl9. Immunohistochemistry using anti-Bcl9BIO demonstrated distinctive staining in the cytoplasm, while the anti-Bcl9ABC signal was detected in both cytoplasm and nuclei of HCC cells, reflecting different states of Bcl9 function because Pygopus-binding to Bcl9 is essential to exert its function together with β-catenin in nucleus. Quantitative analysis revealed a significantly higher immunohistochemical-score by anti-Bcl9BIO in normal liver comparing various differentiation grades of HCC (P < 0.004), whereas no significant difference was noted with anti-Bcl9ABC. Interestingly, immunohistochemical-score of anti-Bcl9BIO in patients aged < 40 years was significantly lower than that of ≥ 40 years group (P < 0.01). The results indicated that anti-Bcl9BIO detected cytoplasmic Bcl9, which does not bind to Pygopus suggesting it could be a useful indicator for development of HCC in young Myanmar patients.

Nuclear Expression of Pygo2 Correlates with Poorly Differentiated State Involving c-Myc, PCNA and Bcl9 in Myanmar Hepatocellular Carcinoma

“…1 a). With this antibody, we previously revealed that the loss of cytoplasmic Bcl9 was associated with the progression of histopathological grade of HCC in Myanmar [ 41 ]. In agreement with that findings, cytoplasmic Bcl9 expression was noted in the normal liver tissue, but was decreased in well differentiated HCC and almost negative in moderately and poorly differentiated HCC.…”

“…Previous studies reported that aberrant expression or nuclear localization of Pygo2 or Bcl9 correlates with poor HCC prognosis [ 18 , 19 , 39 , 58 ]. Our group had also demonstrated the expression of Bcl9 in the cytoplasm even in the normal liver tissue, while the expression is significantly decreased during the progression of histopathological grade and also in juvenile HCC in Myanmar [ 41 ]. The gradual loss of cytoplasmic Bcl9 along with the progression of HCC suggests the association of Pygo2 not only in poorly differentiated HCC but also in most of Myanmar HCC by inducing nuclear translocation of Bcl9 followed by activation of Wnt/β-catenin signaling.…”