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Wnt/β-catenin Signaling and Epigenetic Deregulation in Breast Cancer and Parathyroid Tumours
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Endocrine Surgery.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. , 56 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 778
Keyword [en]
Wnt signaling, parathyroid, epigenetic
National Category
Medical Genetics
Research subject
Medicine; Biology with specialization in Molecular Biology
Identifiers
URN: urn:nbn:se:uu:diva-173417ISBN: 978-91-554-8378-4 (print)OAI: oai:DiVA.org:uu-173417DiVA: diva2:517447
Public defence
2012-06-11, Enghoffsalen, Akademiska Sjukhuset, Ingång 50, Uppsala, 09:15 (Swedish)
Opponent
Supervisors
Available from: 2012-05-21 Created: 2012-04-23 Last updated: 2012-08-01Bibliographically approved
List of papers
1. The internally truncated LRP5 receptor presents a therapeutic target in breast cancer
Open this publication in new window or tab >>The internally truncated LRP5 receptor presents a therapeutic target in breast cancer
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2009 (English)In: PloS one, ISSN 1932-6203, Vol. 4, no 1, e4243- p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Breast cancer is a common malignant disease, which may be caused by a number of genes deregulated by genomic or epigenomic events. Deregulated WNT/beta-catenin signaling with accumulation of beta-catenin is common in breast tumors, but mutations in WNT signaling pathway components have been rare. An aberrantly spliced internally truncated LRP5 receptor (LRP5Delta666-809, LRP5Delta) was shown recently to be resistant to DKK1 inhibition, and was required for beta-catenin accumulation in hyperparathyroid tumors and parathyroid tumor growth. METHODOLOGY/PRINCIPAL FINDINGS: Here we show, by reverse transcription PCR and Western blot analysis, that LRP5Delta is frequently expressed in breast tumors of different cancer stage (58-100%), including carcinoma in situ and metastatic carcinoma. LRP5Delta was required in MCF7 breast cancer cells for the non-phosphorylated active beta-catenin level, transcription activity of beta-catenin, cell growth in vitro, and breast tumor growth in a xenograft SCID mouse model. WNT3 ligand, but not WNT1 and WNT3A augmented the endogenous beta-catenin activity of MCF7 cells in a DKK1-insensitive manner. Furthermore, an anti-LRP5 antibody attenuated beta-catenin activity, inhibited cell growth, and induced apoptosis in LRP5Delta-positive MCF7 and T-47D breast cancer cells, but not in control cells. CONCLUSIONS/SIGNIFICANCE: Our results suggest that the LRP5Delta receptor is strongly implicated in mammary gland tumorigenesis and that its aberrant expression present an early event during disease progression. LRP5 antibody therapy may have a significant role in the treatment of breast cancer.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-88392 (URN)10.1371/journal.pone.0004243 (DOI)000265482200001 ()19158955 (PubMedID)
Available from: 2009-01-30 Created: 2009-01-30 Last updated: 2016-04-28
2. Aberrant WNT/beta-catenin signaling in parathyroid carcinoma
Open this publication in new window or tab >>Aberrant WNT/beta-catenin signaling in parathyroid carcinoma
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2010 (English)In: Molecular Cancer, ISSN 1476-4598, E-ISSN 1476-4598, Vol. 9, 294- p.Article in journal (Refereed) Published
Abstract [en]

Background: Parathyroid carcinoma (PC) is a very rare malignancy with a high tendency to recur locally, and recurrent disease is difficult to eradicate. In most western European countries and United States, these malignant neoplasms cause less than 1% of the cases with primary hyperparathyroidism, whereas incidence as high as 5% have been reported from Italy, Japan, and India. The molecular etiology of PC is poorly understood. Results: The APC (adenomatous polyposis coli) tumor suppressor gene was inactivated by DNA methylation in five analyzed PCs, as determined by RT-PCR, Western blotting, and quantitative bisulfite pyrosequencing analyses. This was accompanied by accumulation of stabilized active nonphosphorylated beta-catenin, strongly suggesting aberrant activation of the WNT/beta-catenin signaling pathway in these tumors. Treatment of a primary PC cell culture with the DNA hypomethylating agent 5-aza-2'-deoxycytidine (decitabine, Dacogen(r)) induced APC expression, reduced active nonphosphorylated beta-catenin, inhibited cell growth, and caused apoptosis. Conclusion: Aberrant WNT/beta-catenin signaling by lost expression and DNA methylation of APC, and accumulation of active nonphosphorylated beta-catenin was observed in the analyzed PCs. We suggest that adjuvant epigenetic therapy should be considered as an additional option in the treatment of patients with recurrent or metastatic parathyroid carcinoma.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-139389 (URN)10.1186/1476-4598-9-294 (DOI)000284703700001 ()21078161 (PubMedID)
Available from: 2010-12-27 Created: 2010-12-23 Last updated: 2017-12-11Bibliographically approved
3. Hypermethylated in cancer 1 (HIC1), a tumor suppressor gene epigenetically deregulated in hyperparathyroid tumors by histone H3 lysine modification
Open this publication in new window or tab >>Hypermethylated in cancer 1 (HIC1), a tumor suppressor gene epigenetically deregulated in hyperparathyroid tumors by histone H3 lysine modification
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2012 (English)In: Journal of Clinical Endocrinology and Metabolism, ISSN 0021-972X, E-ISSN 1945-7197, Vol. 97, no 7, E1307-E1315 p.Article in journal (Refereed) Published
Abstract [en]

CONTEXT:

Primary hyperparathyroidism (pHPT) resulting from parathyroid tumors is a common endocrine disorder with incompletely understood etiology. In renal failure, secondary hyperparathyroidism (sHPT) occurs with multiple tumor development as a result of calcium and vitamin D regulatory disturbance.

OBJECTIVE:

The aim of the study was to investigate whether HIC1 may act as a tumor suppressor in the parathyroid glands and whether deregulated expression involves epigenetic mechanisms.

PATIENTS AND METHODS:

Parathyroid tumors from patients with pHPT included single adenomas, multiple tumors from the same patient, and cancer. Hyperplastic parathyroid glands from patients with sHPT and hypercalcemia and normal parathyroid tissue specimens were included in the study. Quantitative RT-PCR, bisulfite pyrosequencing, colony formation assay, chromatin immunoprecipitation, and RNA interference was used.

RESULTS:

HIC1 was generally underexpressed regardless of the hyperparathyroid disease state including multiple parathyroid tumors from the same patient, and overexpression of HIC1 led to a decrease in clonogenic survival of parathyroid tumor cells. Only the carcinomas showed a high methylation level and reduced HIC1 expression. Cell culture experiments, including use of primary parathyroid tumor cells prepared directly after operation, the general histone methyltransferase inhibitor 3-deazaneplanocin A, chromatin immunoprecipitation, and RNA interference of DNA methyltransferases and EZH2 (enhancer of zeste homolog 2), supported a role of repressive histone H3 modifications (H3K27me2/3) rather than DNA methylation in repression of HIC1.

CONCLUSIONS:

The results strongly support a growth-regulatory role of HIC1 in the parathyroid glands and suggest that perturbed expression of HIC1 may represent an early event during tumor development. Repressive histone modification H3K27me2/3 is involved in repression of HIC1 expression in hyperparathyroid tumors.

National Category
Cancer and Oncology Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-173411 (URN)10.1210/jc.2011-3136 (DOI)000306286100031 ()22544915 (PubMedID)
Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2017-12-07
4. EZH2 is highly expressed in hyperparathyroid tumours and sustains parathyroid tumour cell proliferation
Open this publication in new window or tab >>EZH2 is highly expressed in hyperparathyroid tumours and sustains parathyroid tumour cell proliferation
(English)Manuscript (preprint) (Other academic)
National Category
Cancer and Oncology
Identifiers
urn:nbn:se:uu:diva-173413 (URN)
Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2012-08-01

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