Promoter Hypermethylation Mediated Downregulation of FBP1 in Human Hepatocellular Carcinoma and Colon Cancer

Abstract

FBP1, fructose-1,6-bisphosphatase-1, a gluconeogenesis regulatory enzyme, catalyzes the hydrolysis of fructose 1,6-bisphosphate to fructose 6-phosphate and inorganic phosphate. The mechanism that it functions to antagonize glycolysis and was epigenetically inactivated through NF-kappaB pathway in gastric cancer has been reported. However, its role in the liver carcinogenesis still remains unknown. Here, we investigated the expression and DNA methylation of FBP1 in primary HCC and colon tumor. FBP1 was lowly expressed in 80% (8/10) human hepatocellular carcinoma, 66.7% (6/9) liver cancer cell lines and 100% (6/6) colon cancer cell lines, but was higher in paired adjacent non-tumor tissues and immortalized normal cell lines, which was well correlated with its promoter methylation status. Methylation was further detected in primary HCCs, gastric and colon tumor tissues, but none or occasionally in paired adjacent non-tumor tissues. Detailed methylation analysis of 29 CpG sites at a 327-bp promoter region by bisulfite genomic sequencing confirmed its methylation. FBP1 silencing could be reversed by chemical demethylation treatment with 5-aza-2′-deoxycytidine (Aza), indicating direct epigenetic silencing. Restoring FBP1 expression in low expressed cells significantly inhibited cell growth and colony formation ability through the induction of G2-M phase cell cycle arrest. Moreover, the observed effects coincided with an increase in reactive oxygen species (ROS) generation. In summary, epigenetic inactivation of FBP1 is also common in human liver and colon cancer. FBP1 appears to be a functional tumor suppressor involved in the liver and colon carcinogenesis.

Association between FBP1 and hypoxia-related gene expression in clear cell renal cell carcinoma

“…Low expression of FBP1 has previously been observed in human hepatocellular carcinoma (HC), colon cancer (CC), breast cancer (BC), gastric cancer (GC) and ccRCC tissues (6,(9)(10)(11). The current data is consistent with the latter study.…”

“…The current data is consistent with the latter study. The reason for low FBP1 expression in HC, CC, BC and GC has been identified as hypermethylation of the promoter region of the FBP1 gene (9)(10)(11). However, the mechanism of FBP1 inhibition in ccRCC tissues has not been clearly identified and requires further investigation (12,13).…”

Decreased Expression of Fructose-1,6-bisphosphatase Associates with Glucose Metabolism and Tumor Progression in Hepatocellular Carcinoma

“…Moreover, FBP1 promoter methylation status was determined using the results of methylation-specific PCR, as described in a previous report (8), or methylation array data from GEO database accession numbers GSE60753 (12) and GSE67485 (13). Data on promoter methylation profiles were available for 7 liver cancer cell lines (Supplementary Table S2).…”

“…6) and breast cancer (7). With regard to HCC, in vitro experiments have shown that FBP1 expression is silenced by promoter methylation and that ectopic FBP1 expression inhibits anchorage-dependent growth of a cell line through cell-cycle arrest (8). However, the role of FBP1 in altered glucose metabolism has not been assessed in HCC.…”

Switch of glycolysis to gluconeogenesis by dexamethasone for treatment of hepatocarcinoma

“…However, whether reversing this glycolytic phenotype via gluconeogenesis is beneficial to tumour suppression remains elusive. Furthermore, although normal liver cells continually produce glucose via gluconeogenesis, whether and how those transformed hepatocytes escape the inhibitory effect of gluconeogenesis on glycolysis [19][20][21] remains unclear.…”