Identification of Germline FOXE1 and Somatic MAPK Pathway Gene Alterations in Patients with Malignant Struma Ovarii, Cleft Palate and Thyroid Cancer

Germline variants in the FOXE1 transcription factor have been associated with thyroid ectopy, cleft palate (CP) and thyroid cancer (TC). Here, we aimed to clarify the role of FOXE1 in Portuguese families (F1 and F2) with members diagnosed with malignant struma ovarii (MSO), an ovarian teratoma with ectopic malignant thyroid tissue, papillary TC (PTC) and CP. Two rare germline heterozygous variants in the FOXE1 promoter were identified: F1) c.-522G>C, in the proband (MSO) and her mother (asymptomatic); F2) c.9C>T, in the proband (PTC), her sister and her mother (CP). Functional studies using rat normal thyroid (PCCL3) and human PTC (TPC-1) cells revealed that c.9C>T decreased FOXE1 promoter transcriptional activity in both cell models, while c.-522G>C led to opposing activities in the two models, when compared to the wild type. Immunohistochemistry and RT-qPCR analyses of patients' thyroid tumours revealed lower FOXE1 expression compared to adjacent normal and hyperplastic thyroid tissues. The patient with MSO also harboured a novel germline AXIN1 variant, presenting a loss of heterozygosity in its benign and malignant teratoma tissues and observable β-catenin cytoplasmic accumulation. The sequencing of the F1 (MSO) and F2 (PTC) probands' tumours unveiled somatic BRAF and HRAS variants, respectively. Germline FOXE1 and AXIN1 variants might have a role in thyroid ectopy and cleft palate, which, together with MAPK pathway activation, may contribute to tumours' malignant transformation.

Vorinostat synergizes with antioxidant therapy to target myeloproliferative neoplasms

BCR-ABL-negative myeloproliferative neoplasms (MPNs) are driven by JAK-STAT pathway activation, but epigenetic alterations also play an important pathophysiological role. These can be pharmacologically manipulated with histone deacetylase inhibitors (HDACIs), which have proven to be clinically effective in the treatment of MPNs but exhibit dose-limiting toxicity. The treatment of primary MPN cells with vorinostat modulates the expression of genes associated with apoptosis, cell cycle, inflammation, and signaling. The induction of this transcriptional program results in decreased cellular viability, paralleled by a decrease in levels of reactive oxygen species (ROS). In vitro manipulation of ROS levels revealed that the reduction of ROS levels promoted apoptosis. When vorinostat was combined with antioxidant agents, the apoptosis of MPN cells increased in a synergistic manner. The results described here suggest a novel and promising therapeutic strategy combining HDACIs with ROS-reducing agents to treat MPNs.

The Bone Marrow-Mediated Protection of Myeloproliferative Neoplastic Cells to Vorinostat and Ruxolitinib Relies on the Activation of JNK and PI3K Signalling Pathways

The classical BCR-ABL-negative Myeloproliferative Neoplasms (MPN) are a group of heterogeneous haematological diseases characterized by constitutive JAK-STAT pathway activation. Targeted therapy with Ruxolitinib, a JAK1/2-specific inhibitor, achieves symptomatic improvement but does not eliminate the neoplastic clone. Similar effects are seen with histone deacetylase inhibitors (HDACi), albeit with poorer tolerance. Here, we show that bone marrow (BM) stromal cells (HS-5) protected MPN-derived cell lines (SET-2; HEL and UKE-1) and MPN patient-derived BM cells from the cytotoxic effects of Ruxolitinib and the HDACi Vorinostat. This protective effect was mediated, at least in part, by the secretion of soluble factors from the BM stroma. In addition, it correlated with the activation of signalling pathways important for cellular homeostasis, such as JAK-STAT, PI3K, JNK, MEK-ERK and NF-κB. Importantly, the pharmacological inhibition of JNK and PI3K pathways completely abrogated the BM protective effect on MPN cell lines and MPN patient samples. Our findings shed light on mechanisms of tumour survival and may indicate novel therapeutic approaches for the treatment of MPN.

Epigenetic Alterations in Fanconi Anaemia: Role in Pathophysiology and Therapeutic Potential

Fanconi anaemia (FA) is an inherited disorder characterized by chromosomal instability. The phenotype is variable, which raises the possibility that it may be affected by other factors, such as epigenetic modifications. These play an important role in oncogenesis and may be pharmacologically manipulated. Our aim was to explore whether the epigenetic profiles in FA differ from non-FA individuals and whether these could be manipulated to alter the disease phenotype. We compared expression of epigenetic genes and DNA methylation profile of tumour suppressor genes between FA and normal samples. FA samples exhibited decreased expression levels of genes involved in epigenetic regulation and hypomethylation in the promoter regions of tumour suppressor genes. Treatment of FA cells with histone deacetylase inhibitor Vorinostat increased the expression of DNM3Tβ and reduced the levels of CIITA and HDAC9, PAK1, USP16, all involved in different aspects of epigenetic and immune regulation. Given the ability of Vorinostat to modulate epigenetic genes in FA patients, we investigated its functional effects on the FA phenotype. This was assessed by incubating FA cells with Vorinostat and quantifying chromosomal breaks induced by DNA cross-linking agents. Treatment of FA cells with Vorinostat resulted in a significant reduction of aberrant cells (81% on average). Our results suggest that epigenetic mechanisms may play a role in oncogenesis in FA. Epigenetic agents may be helpful in improving the phenotype of FA patients, potentially reducing tumour incidence in this population.

Vorinostat induces apoptosis and differentiation in myeloid malignancies: genetic and molecular mechanisms

Background

Aberrant epigenetic patterns are central in the pathogenesis of haematopoietic diseases such as myelodysplastic syndromes (MDS) and acute myeloid leukaemia (AML). Vorinostat is a HDACi which has produced responses in these disorders. The purpose of this study was to address the functional effects of vorinostat in leukemic cell lines and primary AML and MDS myeloid cells and to dissect the genetic and molecular mechanisms by which it exerts its action.

Methodology/Principal Findings

Functional assays showed vorinostat promoted cell cycle arrest, inhibited growth, and induced apoptosis and differentiation of K562, HL60 and THP-1 and of CD33⁺ cells from AML and MDS patients. To explore the genetic mechanism for these effects, we quantified gene expression modulation by vorinostat in these cells. Vorinostat increased expression of genes down-regulated in MDS and/or AML (cFOS, COX2, IER3, p15, RAI3) and suppressed expression of genes over-expressed in these malignancies (AXL, c-MYC, Cyclin D1) and modulated cell cycle and apoptosis genes in a manner which would favor cell cycle arrest, differentiation, and apoptosis of neoplastic cells, consistent with the functional assays. Reporter assays showed transcriptional effect of vorinostat on some of these genes was mediated by proximal promoter elements in GC-rich regions. Vorinostat-modulated expression of some genes was potentiated by mithramycin A, a compound that interferes with SP1 binding to GC-rich DNA sequences, and siRNA-mediated SP1 reduction. ChIP assays revealed vorinostat inhibited DNA binding of SP1 to the proximal promoter regions of these genes. These results suggest vorinostat transcriptional action in some genes is regulated by proximal promoter GC-rich DNA sequences and by SP1.

Conclusion

This study sheds light on the effects of vorinostat in AML and MDS and supports the implementation of clinical trials to explore the use of vorinostat in the treatment of these diseases.