5-Aza-2′-Deoxycytidine Has Minor Effects on Differentiation in Human Thyroid Cancer Cell Lines, But Modulates Genes That Are Involved in Adaptation In Vitro

Abstract

Background: In thyroid cancer, the lack of response to specific treatment, for example, radioactive iodine, can be caused by a loss of differentiation characteristics of tumor cells. It is hypothesized that this loss is due to epigenetic modifications. Therefore, drugs releasing epigenetic repression have been proposed to reverse this silencing. Methods: We investigated which genes were reinduced in dedifferentiated human thyroid cancer cell lines when treated with the demethylating agent 5-aza-2¢-deoxycytidine (5-AzadC) and the histone deacetylase inhibitors trichostatin A (TSA) and suberoylanilide hydroxamic acid, by using reverse transcriptase-polymerase chain reaction and microarrays. These results were compared to the expression patterns in in vitro human differentiated thyrocytes and in in vivo dedifferentiated thyroid cancers. In addition, the effects of 5-AzadC on DNA quantities and cell viability were investigated. Results: Among the canonical thyroid differentiation markers, most were not, or only to a minor extent, reexpressed by 5-AzadC, whether or not combined with TSA or forskolin, an inducer of differentiation in normal thyrocytes. Furthermore, 5-AzadC-modulated overall mRNA expression profiles showed only few commonly regulated genes compared to differentiated cultured primary thyrocytes. In addition, most of the commonly strongly 5-AzadC-induced genes in cell lines were either not regulated or upregulated in anaplastic thyroid carcinomas. Further analysis of which genes were induced by 5-AzadC showed that they were involved in pathways such as apoptosis, antigen presentation, defense response, and cell migration. A number of these genes had similar expression responses in 5-AzadC-treated nonthyroid cell lines. Conclusions: Our results suggest that 5-AzadC is not a strong inducer of differentiation in thyroid cancer cell lines. Under the studied conditions and with the model used, 5-AzadC treatment does not appear to be a potential redifferentiation treatment for dedifferentiated thyroid cancer. However, this may reflect primarily the inadequacy of the model rather than that of the treatment. Moreover, the observation that 5-AzadC negatively affected cell viability in cell lines could still suggest a therapeutic opportunity. Some of the genes that were modulated by 5-AzadC were also induced in nonthyroid cancer cell lines, which might be explained by an epigenetic modification resulting in the adaptation of the cell lines to their culture conditions.

Wide Spectrum of DUOX2 Deficiency: From Life-Threatening Compressive Goiter in Infancy to Lifelong Euthyroidism

“…A transient phenotype could result from the compensation of peroxide generation by the DUOX1/DUOXA1 complex when thyroid hormone requirements fall with age. Such compensation may be epigenetically regulated: the locus on chromosome 15 that contains DUOX1 and 2 and their respective maturation factors is a site of DNA methylation (6), and demethylating agents increase DUOX1 and 2 expression in thyroid cells (7). Perinatal iodine overload reportedly masked congenital hypothyroidism at newborn screening in one of two siblings with biallelic DUOX2 mutations (8), but there was no such history in the discordant siblings reported here.…”

Genetics and epigenetics of sporadic thyroid cancer

“…G. Kim et al, 2013; Zuo et al, 2010). However, the efficacy of 5 azacytidine or similar drugs as tools for redifferentiation is not well established (Dom et al, 2013; Vivaldi et al, 2009), and these agents would likely seem to be too non-specific in their effects.…”

High BLM Expression Predicts Poor Clinical Outcome and Contributes to Malignant Progression in Human Cholangiocarcinoma

“…A total of 5,378 filtered DEGs were utilized to build a co-expression network, and 29 modules were screened. Loss of differentiation is a common event in tumor progression, and a high histological grade largely has an intimate correlation with an unfavorable prognosis ( 38 ). Here, it was found that the blue module had the highest correlation with tumor grade, which means that blue module genes are closely related to clinical traits.…”