Aberrant methylation of the human hedgehog interacting protein (HHIP) gene in pancreatic neoplasms

Abstract

Hedgehog pathway overactivity has been implicated in the development of a variety of human cancers. The Human Hedgehog interacting protein (HHIP), a negative regulator of hedgehog signaling, has been shown to be underexpressed in pancreatic cancers. In this study we determined if the HHIP gene is a target for genetic and epigenetic alterations. While no mutations of HHIP were identified, we found complete methylation of the HHIP promoter CpG island in three pancreatic cancer cell lines, and partial hypermethylation in 13/17 (80%) pancreatic cancer cell lines, 35/75 (46%) primary pancreatic cancers and 14/18 (78%) pancreatic cancer xenografts, but no methylation in 13 normal pancreata. In pancreatic cancer cell lines, complete methylation was associated with absent or reduced HHIP expression by real-time RT-PCR. HHIP expression could be restored in methylated cell lines using epigenetic modifier drugs. Restoring the expression of HHIP in pancreatic cancer cells by 5-aza-2'-deoxycytidine led to a decrease in Gli reporter activity, consistent with downregulation of Hedgehog signaling. These results indicate in some pancreatic adenocarcinomas that HHIP is epigenetically inactivated by promoter methylation, and its silencing could contribute to the increased Hedgehog signaling observed in pancreatic neoplasms.

Blocking the hedgehog pathway inhibits hepatoblastoma growth #

“…Because CpG islands have been located around the transcription start site of the negative regulators of Hh signaling PTCH1 and HHIP, they represent valid candidates for hypermethylation-associated transcriptionally silencing in human cancers. [21][22][23][24] Using bisulfite sequencing, we found no methylation of the promoter-associated CpG island of the PTCH1 gene in normal and malignant liver cells (data not shown), which is consistent with the high PTCH1 expression found (Fig. 1A).…”

“…13 An alternative mechanism causing activation of Hh signaling in pediatric liver tumors comes from our data on the methylation status of the HHIP gene, which clearly showed that HHIP expression is strongly reduced through CpG island hypermethylation in a subset of cases. Several lines of evidence have already indicated that HHIP expression could be transcriptionally silenced by CpG island hypermethylation, as shown for pancreatic, 21 gastrointestinal cancers, 34 and just recently HCC. 35 The absence or significant decrease of HHIP mRNA levels found in lung and liver cancers 15,36 additionally suggest a broader role of this epigenetic alteration in tumor development.…”

Hedgehog signaling maintains a tumor stem cell compartment in multiple myeloma

“…NCI-H929 cells coexpressed INDIAN HEDGEHOG (IHH), PTCH1, SMO, and GLI1. In addition, all of the MM cell lines lacked expression of HHIP, a secreted Hh ligand antagonist that is epigenetically silenced in pancreatic cancer (26). This expression pattern resembles that of other cancers in which Hh signaling may play an important role (14,17).…”

Hedgehog signaling pathway and gastrointestinal stem cell signaling network (Review)

“…IHH is significantly upregulated in primary pancreatic cancer (56). CpG hyper-methylation of HHIP1 promoter was detected in 13 out of 17 pancreatic cancer cell lines, and in 35 out of 75 primary pancreatic cancer (50).…”

“…On the other hand, HHIP1 is downregulated in a variety of tumors, such as gastric cancer, pancreatic cancer, colorectal cancer, and lung cancer (49). HHIP1 down-regulation in pancreatic cancer is due to epigenetic CpG hypermethylation (50).…”