Abstract 3595: Improved therapeutics for hepatocellular carcinoma

Autor: Christi A. Walter, Jessica A. Zavadil
Rok vydání: 2016
Předmět:
Zdroj: Cancer Research. 76:3595-3595
ISSN: 1538-7445
0008-5472
Popis: Eighty percent of hepatocellular carcinoma (HCC) within the USA is diagnosed late when chemotherapy provides only 2 months increased survival. We fortuitously found that treatment with an alkylating agent, methylnitrosurea (MNU), prior to tumorigenesis reduced tumor prevalence later in life by ∼50% in C3HeB/FeJ male mice, a model of spontaneous HCC. A similar effect was observed with temozolomide (TMZ), a glioblastoma therapy that induces the same DNA damage at similar proportions to MNU. O6-methylguanine-DNA methyltransferase (MGMT) repairs the highly mutagenic and cytotoxic O6-methylguanine lesions induced by TMZ, and MGMT abundance influences therapy response in glioblastoma. MGMT is reduced in 1/3 of human HCC, leading us to hypothesize that TMZ could be effective in treating HCC. We proposed to combine TMZ with suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, to maximize efficacy, reasoning that SAHA would allow TMZ greater access to DNA to induce greater levels of damage. We tested this drug combination in two human HCC cell lines, Huh7, with reduced MGMT expression, and SNU398, with higher expression. TMZ and SAHA synergistically reduced cell viability in both cell lines with multiple dose combinations. Based on this outcome, we tested the drugs in tumor-bearing C3HeB/FeJ mice. Surprisingly, DMSO treated solvent control mice showed reduced tumor burden. The DMSO treatment was repeated adding a sham control group and confirmed that DMSO significantly reduces tumor burden. The TMZ cohort also displayed a significantly lower tumor burden compared to the sham cohort, but no significant difference was found with SAHA alone or SAHA+TMZ. We previously showed that a hMGMT transgene protects from hepatocarcinogenesis in C3HeB/FeJ mice, but surprisingly, there is not additional protection when transgenic mice are treated with MNU. These results suggest that the more prevalent cytotoxic lesions induced by MNU and TMZ, e.g. N7-methylguanine, may be more important in HCC than O6-methylguanine. These lesions are recognized by methylpurine-DNA glycosylase (MPG) and repaired through base excision repair. Therefore, we directly tested the role of MPG in TMZ therapy through altered expression of MPG in Huh7 and SNU398 cell lines and showed that it does affect sensitivity to TMZ. Citation Format: Jessica A. Zavadil, Christi A. Walter. Improved therapeutics for hepatocellular carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3595.
Databáze: OpenAIRE
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