Antitumor Effects of a Combined 5-Aza-2′Deoxycytidine and Valproic Acid Treatment on Rhabdomyosarcoma and Medulloblastoma in Ptch Mutant Mice

Abstract

Patched (Ptch) heterozygous mice develop medulloblastoma (MB) and rhabdomyosarcoma (RMS) resembling the corresponding human tumors. We have previously shown that epigenetic silencing of the intact Ptch allele contributes to tumor formation in this model. Here, we investigated whether targeting of epigenetic silencing mechanisms could be useful in the treatment of Ptch-associated cancers. A reduction of endogenous DNA methyltransferase1 (Dnmt1) activity significantly reduced tumor incidence in heterozygous Ptch knockout mice. A combined treatment with the Dnmt inhibitor 5-aza-2 ¶deoxycytidine (5-aza-dC) and the histone deacetlyase (HDAC) inhibitor valproic acid (VPA) efficiently prevented MB and RMS formation, whereas monotherapies with either drug were less effective. Wild-type Ptch expression was efficiently reactivated in tumors by 5-aza-dC/VPA combination therapy. This was associated with reduced methylation of the Ptch promoter and induction of histone hyperacetylation suggesting inhibition of HDACs in vivo. However, the treatment was not effective in clinically overt, advanced stage tumors. This is a first in vivo demonstration that targeting of Dnmt and HDAC activities is highly effective in preventing formation of Ptch-associated tumors. The results suggest a novel clinical strategy for consolidation therapy of corresponding tumors in humans after completion of conventional treatment. Our data also suggest that epigenetic therapy may be less effective in treating advanced stages of tumors, at least in this tumor model. [Cancer Res 2009;69(3):887-95]

Cucurbitacin B Alters the Expression of Tumor-Related Genes by Epigenetic Modifications in NSCLC and Inhibits NNK-Induced Lung Tumorigenesis

“…5-aza-2 0 -deoxycytidine, a standard DNMT inhibitor, and 400 mg/kg b.w. valproic acid, a standard HDAC inhibitor, have been reported to cause a moderate reversible leukocytopenia in mice (43). In yet another study performed in rats, the combinations of 20 mg/kg b.w.…”

Histone deacetylase inhibitors in cancer therapy. A review

“…Inhibitors of DNA methyl transferases 5-azacytidine (azacitidine) and 5-aza-2'-deoxycytidine (decitabine) had increased antitumor effects when used with HDAC inhibitors [60][61][62][63][64] . Decitabine and VPA both induced apoptosis and the combination increased their effects both in vitro and in vivo 65,66 . Co-treatment of prostate, pancreatic tumor, acute myelogenous leukemia (AML) AML1/ETO-positive and non small cell lung cancer (NSCLC) cells with trichostatin A and decitabine synergistically induced apoptosis 63,64,67,68 .…”

High expression of DNA methyltransferases in primary human medulloblastoma

“…An in vitro experiment showed that the DNMT inhibitor 5-aza-2'-deoxycytidine (decitabine) reactivates the tumor suppressor PTCH1 gene in the MB cell line [4]. A combination of DNMT and histone deacetylase (HDAC) inhibitors was effective to prevent MB development in Ptch knockout mice, while in advanced stage tumors this therapy was less efficient [5]. Epigenetic modulators combined with multi-kinase inhibitor could enhance apoptosis in vitro in medulloblastoma cells [24].…”