Histone modification enhances the effectiveness of IL-13 receptor targeted immunotoxin in murine models of human pancreatic cancer

Abstract

BackgroundInterleukin-13 Receptor α2 (IL-13Rα2) is a tumor-associated antigen and target for cancer therapy. Since IL-13Rα2 is heterogeneously overexpressed in a variety of human cancers, it would be highly desirable to uniformly upregulate IL-13Rα2 expression in tumors for optimal targeting.MethodsWe examined epigenetic regulation of IL-13Rα2 in a murine model of human pancreatic cancer by Bisulfite-PCR, sequencing for DNA methylation and chromatin immunoprecipitation for histone modification. Reverse transcription-PCR was performed for examining changes in IL-13Rα2 mRNA expression after treatment with histone deacetylase (HDAC) and c-jun inhibitors. In vitro cytotoxicity assays and in vivo testing in animal tumor models were performed to determine whether HDAC inhibitors could enhance anti-tumor effects of IL-13-PE in pancreatic cancer. Mice harboring subcutaneous tumors were treated with HDAC inhibitors systemically and IL-13-PE intratumorally.ResultsWe found that CpG sites in IL-13Rα2 promoter region were not methylated in all pancreatic cancer cell lines studied including IL-13Rα2-positive and IL-13Rα2-negative cell lines and normal cells. On the other hand, histones at IL-13Rα2 promoter region were highly-acetylated in IL-13Rα2-positive but much less in receptor-negative pancreatic cancer cell lines. When cells were treated with HDAC inhibitors, not only histone acetylation but also IL-13Rα2 expression was dramatically enhanced in receptor-negative pancreatic cancer cells. In contrast, HDAC inhibition did not increase IL-13Rα2 in normal cell lines. In addition, c-jun in IL-13Rα2-positive cells was expressed at higher level than in negative cells. Two types of c-jun inhibitors prevented increase of IL-13Rα2 by HDAC inhibitors. HDAC inhibitors dramatically sensitized cancer cells to immunotoxin in the cytotoxicity assay in vitro and increased IL-13Rα2 in the tumors subcutaneously implanted in the immunodeficient animals but not in normal mice tissues. Combination therapy with HDAC inhibitors and immunotoxin synergistically inhibited growth of not only IL-13Rα2-positive but also IL-13Rα2-negative tumors.ConclusionsWe have identified a novel function of histone modification in the regulation of IL-13Rα2 in pancreatic cancer cell lines in vitro and in vivo. HDAC inhibition provides a novel opportunity in designing combinatorial therapeutic approaches not only in combination with IL-13-PE but with other immunotoxins for therapy of pancreatic cancer and other cancers.

TOP2A is overexpressed and is a therapeutic target for adrenocortical carcinoma

“…Our study also found that TOP2A was up-regulated twofold after decitabine treatment in adrenocortical cell lines (NCI-H295R and SW13). Thus, epigenetically increasing TOP2A expression with the use of demethylating agents may be an effective strategy for increasing TOP2A expression when using agents which target TOP2A 37 . However, we are not able to experimentally prove this as both of the widely used and authenticated ACC cell lines have high levels of basal TOP2A expression and demethylating agents such as decitabine have an antiproliferative effect in ACC cell lines 38 .…”

Characterization of the Molecular Genetic Mechanisms that Contribute to Pancreatic Cancer Carcinogenesis

“…Histone acetylases/deacetylases, the polycomb group proteins, and HP1 are the key histone protein complexes that influence chromatin accessibility and gene activity. Histone modifications have been linked to the altered expression of several critical genes in pancreatic cancer, including the IL-13 receptor, MUC17, MUC4, MUC1 and MUC2 (Esteller, 2007;Fujisawa et al, 2011;Kitamoto et al, 2011;Vincent et al, 2008;Yamada et al, 2008).…”

The Contribution of Next Generation Sequencing Technologies to Epigenome Research of Stem Cell and Tumorigenesis

“…By ChIP, Ballestar et al [79] have found that the gene-specific profiles of Methyl-CpG binding proteins (MBDs) exist for hypermethylated promoters of breast cancer cells with a common pattern of histone modifications shared. It's interesting that Fujisawa et al [81] found CpG sites in IL-13Rα2 promoter region were not methylated in all pancreatic cancer cell lines studied including IL-13Rα2-positive and IL-13Rα2-negative cell lines and normal cells. On the other hand, histones at IL-13Rα2 promoter region were highly acetylated in IL-13Rα2-positive but much less in receptor-negative pancreatic cancer cell lines.…”