The Importance of Liver Fatty Acid-Binding Protein Downregulation in Hepatocellular Carcinoma

Aim: The purpose of this study was to see how important it was for the expression of liver fatty acid-binding protein (L-FABP) to be downregulated in hepatocellular carcinoma (HCC). Methods: Immunohistochemical labelling for L-FABP was performed on tissue microarrays from 146 instances of HCC. For each L-FABP-negative HCC, further immunohistochemical staining was performed using a representative whole-tissue section to confirm the downregulation of L-FABP expression and to assess the intratumoral heterogeneity of the staining pattern. Histological slides were examined and clinical data was gathered from the clinical files. On the tissue microarrays, immunohistochemical staining for cytokeratin (CK) 7, CK 19, -catenin-catenin, glutamine synthetase (GS), and serum amyloid A (SAA) were also done. L-FABP-negative and L-FABP-positive HCC patients were compared in terms of clinicopathological characteristics. Furthermore, L-FABP and GS gene expression in HCC and cholangiocarcinoma (CC) cell lines were analyzed using real-time reverse transcription polymerase chain reaction. Mutation analysis of HNF1A (encoding hepatocyte nuclear factor 1 (HNF1) ) was performed for L-FABP-negative HCC cases. Results: Sixteen (10.9%) of the 146 HCC patients tested negative for L-FABP. When we examined the correlation between the downregulation pattern of L-FABP and tumor size, most cases of smaller HCC ( 2 cm in diameter) exhibited focal downregulation, while most cases of larger HCC (> 2 cm in diameter) exhibited diffuse downregulation. The correlation was statistically significant (P = 0.036). When the HCC was smaller, the L-FABP-negative area often corresponded to a “nodule-in-nodule” appearance. Among the small HCC cases, tumor differentiation was significantly lower, and the frequency of intratumoral inflammation was significantly lower in L-FABP-negative cases than in L-FABP-positive cases (P = 0.032 and P = 0.009, respectively). The frequency of positivity for b-catenin and GS staining was significantly higher in L-FABP-negative cases of small HCC than in L-FABP-positive cases of small HCC (P = 0.009 and P = 0.000, respectively). Among six HCC cell lines examined, four showed higher expression of L-FABP, and the remaining two cell lines showed lower or no expression of L-FABP. Two of the 16 L-FABP-negative HCC cases possessed a mutation in exon 4 of HNF1A. Conclusion: In smaller HCC, L-FABP downregulation probably occurs because of phenotypic changes during tumor progression. Moreover, this downregulation correlated with tumor differentiation and intratumoral inflammation.