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- Svedlund, Jessica
(author)
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Wnt/β-catenin Signaling and Epigenetic Deregulation in Breast Cancer and Parathyroid Tumours
- 2012
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Doctoral thesis (other academic/artistic)abstract
- The Wnt/β-catenin signaling pathway is often deregulated in cancer. Here we investigate Wnt/β-catenin signaling, aberrant accumulation of β-catenin, and epigenetic deregulation in breast cancer and parathyroid tumours.An aberrantly spliced Wnt coreceptor LRP5 (LRP5Δ) is important for accumulation of nonphosphorylated active β-catenin and tumour growth in parathyroid tumours. Paper I demonstrated frequent expression of LRP5Δ in breast tumours and substantiated that breast tumour cell growth was dependent on continuous activation of the Wnt/β-catenin pathway by LRP5Δ. A LRP5 antibody reduced the levels of active β-catenin, inhibited tumour cell growth and caused apoptosis in breast cancer cells. Antibody therapy may have a significant role in the treatment of breast cancer.Paper II revealed lost expression of the tumour suppressor gene APC in parathyroid carcinomas, likely due to CpG methylation. Also accumulation of nonphosporylated active β-catenin was observed, indicating activation of Wnt/β-catenin signaling. Treatment of primary parathyroid carcinoma cells with the demethylating agent 5-aza-2’-deoxycytidine reduced the levels of active β-catenin, inhibited cell growth and caused apoptosis, suggesting that adjuvant epigenetic therapy could be considered in patients with metastatic or recurrent parathyroid carcinoma.In paper III we showed that the expression of the tumour suppressor gene HIC1 was generally reduced in parathyroid tumours of primary and secondary origin, and parathyroid carcinomas. Overexpressing HIC1 reduced cell viability and suppressed colony formation, supporting a tumour suppressor role in the parathyroid gland. Results suggested that the observed underexpression of HIC1 could be explained by epigenetic deregulation involving histone methylation rather than CpG methylation.Paper IV demonstrated increased expression of the histone methyltransferase EZH2 in parathyroid tumours of primary and secondary origin, and most apparent in parathyroid carcinomas. Decreasing EZH2 resulted in reduced cell viability and colony formation capacity suggesting that EZH2 may function as an oncogene in parathyroid tumours. Furthermore, depletion of EZH2 also reduced the amount of active β-catenin. EZH2 may represent a novel therapeutic target in parathyroid tumours.The fact that HIC1 was underexpressed and EZH2 overexpressed in parathyroid tumours regardless of the hyperparathyroid disease state may represent a possibility for a common pathway in parathyroid tumour development.
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- Åkerström, Tobias, et al.
(author)
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Intratumoural Aldosterone and Heterogeneity in Genetic Subtypes of Aldosterone Producing Adenomas
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Other publication (other academic/artistic)abstract
- AbstractContextPrimary Aldosteronism is the most common endocrine cause of hypertension. Unilateral disease in the form of Aldosterone producing adenomas (APAs) is found in 1.5-3% of hypertensive. Determining the source of aldosteronism is necessary for correct diagnosis and further molecular analysis.ObjectiveTo evaluate tissue aldosterone as a marker of aldosterone production and correlate it to patient phenotype and tumour mutation status, and to explore molecular heterogeneity in APAs.DesignForty-six frozen tumour samples from patients diagnosed with APAs were included. Tumours were derived from a single endocrine referral center, and had been stored from 1985 to 2015. Tissue aldosterone concentration was related to clinical characteristics, genotype and molecular phenotype. Genetic heterogeneity was investigated by biopsies and in situ sequencing. Immunohistochemical analysis of Nephronectin, CYP11B1 and CYP11B2 were performed. qRT-PCR and in situ mRNA expression were used to analyze CYP11B2 mRNA expression.ResultsTissue aldosterone content was specific for aldosterone producing tumours and proved stable after long-term storage at -70C. CYP11B2 expression and aldosterone concentrations were higher in tumours with ATP1A1, ATP2B3 and CACNA1D mutations compared to those with KCNJ5 mutations (p<0.0001 and p=0.0018 respectively). The tissue aldosterone content correlated with CYP11B2 protein expression (r2=0.48, p<0.0001), and both CYP11B2 expression and tissue aldosterone content were associated with the plasma level of aldosterone (r2=0.33, p=0.0002 and r2=0.75, p<0.0001 respectively). In four tumours with suspicion of genetic heterogeneity, sampling of DNA revealed a heterogeneous KCNJ5 mutation in one tumour. Using in situ sequencing we confirmed heterogeneous expression of mutated KCNJ5 cDNA in the others. In three tumours classified as APAs, no mutation nor any aldosterone or CYP11B2 were detected, suggesting non-functional tumours.ConclusionTissue aldosterone content is specific for aldosterone producing lesions, correlates with plasma levels, and displays variable levels depending on tumour genotype. Genetic heterogeneity is evident in a subgroup of KCNJ5 mutated tumours. The present results show that CYP11B2 expression and tissue aldosterone measurement may be used to clarify the source of aldosterone secretion.
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