oru.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Biological signature of HER2-positive breast cancer
Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Human epidermal growth factor receptor 2 (HER2) overexpressing breast cancers (HER2+ breast cancer) are associated with an aggressive disease course. This thesis is focused on improving the understanding of the biological signature of HER2+ breast cancer.

In Paper I, we identified a common deletion spanning the SLC25A43 gene which codes for a mitochondrial transport protein. Loss of heterozygosity in this gene was confirmed in an extended cohort of HER2+ breast cancer and in other types of cancers. Protein expression analysis of SLC25A43using immunohistochemistry (IHC) in HER2+ breast cancers showed that tumours with negative or low expression of SLC25A43 had lower S-phase fraction compared to tumours with medium or high expression, indicating its possible role in cell proliferation. Absence of mutations in this gene in HER2+ breast cancers led to Paper II where DNA methylation in the SLC25A43 gene was interrogated using Pyrosequencing. HER2+ breast cancer with no deletion in the SLC25A43 gene showed higher methylation in the CpG island (CGI), suggesting methylation in the CGI as an alternate mechanism for SLC25A43 gene inactivation. Methylation in the CGI and in the adjacent shores of the SLC25A43 gene was associated with negative oestrogen receptor status and positive lymph node status. In Paper III, genome-wide DNA methylation analysis of HER2+ breast cancer and normal breast tissue revealed hypermethylation in HER2+ breast cancer affecting particularly the homeobox gene family when compared to normal. We identified a total of 73 candidate genes showing differential methylation in HER2+ breast cancer and external validation of gene expression in a selected group of these genes revealed lowered mean expression in HER2+ breast cancer, warranting future clinical studies of these candidate genes. In Paper IV, we investigated expression and localisation of phosphorylated (p) Akt and FOXO3a and FOXG1 in HER2+ breast cancer using IHC. Cytoplasmic expression of pFOXO3a was associated with sentinel node metastasis while cytoplasmic expression of FOXG1 was correlated to negative progesterone receptor status. This indicates the biological and prognostic value of these proteins in HER2+ breast cancer.

Thus, this thesis identified changes at the genetic, epigenetic and protein levels which add new information and improve our understanding of HER2+ breast cancer.

Place, publisher, year, edition, pages
Örebro: Örebro universitet , 2013. , p. 61
Series
Örebro Studies in Medicine, ISSN 1652-4063 ; 90
Keywords [en]
HER2+ breast cancer, SLC25A43, CpG island, DNA methylation, Homeobox genes, FOXO3a, FOXG1
National Category
Medical and Health Sciences
Research subject
Biomedicine
Identifiers
URN: urn:nbn:se:oru:diva-28978ISBN: 978-91-7668-941-7 (print)OAI: oai:DiVA.org:oru-28978DiVA, id: diva2:619815
Public defence
2013-06-14, Wilandersalen, F-huset, Örebro universitetssjukhus, Södra Grev Rosengatan, Örebro, 11:00 (Swedish)
Opponent
Supervisors
Available from: 2013-05-06 Created: 2013-05-06 Last updated: 2018-03-09Bibliographically approved
List of papers
1. The mitochondrial transporter SLC25A43 is frequently deleted and may influence cell proliferation in HER2-positive breast tumors
Open this publication in new window or tab >>The mitochondrial transporter SLC25A43 is frequently deleted and may influence cell proliferation in HER2-positive breast tumors
Show others...
2012 (English)In: BMC Cancer, ISSN 1471-2407, E-ISSN 1471-2407, Vol. 12, no 1, article id 350Article in journal (Refereed) Published
Abstract [en]

Background: Overexpression of the human epidermal growth factor receptor (HER) 2 is associated with poor prognosis and shortened survival in breast cancer patients. HER2 is a potent activator of several signaling pathways that support cell survival, proliferation and metabolism. In HER2-positive breast cancer there are most likely unexplored proteins that act directly or indirectly downstream of well established pathways and take part in tumor development and treatment response.

Methods: In order to identify novel copy number variations (CNVs) in HER2-positive breast cancer whole-genome single nucleotide polymorphism (SNP) arrays were used. A PCR-based loss of heterozygosis (LOH) assay was conducted to verify presence of deletion in HER2-positive breast cancer cases but also in HER2 negative breast cancers, cervical cancers and lung cancers. Screening for mutations was performed using single-strand conformation polymorphism (SSCP) followed by PCR sequencing. Protein expression was evaluated with immunohistochemistry (IHC).

Results: A common deletion at chromosome Xq24 was found in 80% of the cases. This locus harbors the gene solute carrier (SLC) family 25A member 43 (SLC25A43) encoding for a mitochondrial transport protein. The LOH assay revealed presence of SLC25A43 deletion in HER2-positive (48%), HER2-negative (9%), cervical (42%) and lung (67%) cancers. HER2-positive tumors with negative or low SLC25A43 protein expression had significantly lower S-phase fraction compared to tumors with medium or high expression (P = 0.024).

Conclusions: We have found deletion in the SLC25A43 gene to be a common event in HER2-positive breast cancer as well as in other cancers. In addition, the SLC25A43 protein expression was shown to be related to S-phase fraction in HER2-positive breast cancer. Our results indicate a possible role of SLC25A43 in HER2-positive breast cancer and support the hypothesis of altered mitochondrial function in cancer.

Keywords
Breast cancer, HER2, SLC25A43, S-phase
National Category
Medical and Health Sciences Cancer and Oncology
Research subject
Medicine
Identifiers
urn:nbn:se:oru:diva-27546 (URN)10.1186/1471-2407-12-350 (DOI)000309407100001 ()22883974 (PubMedID)2-s2.0-84864803696 (Scopus ID)
Available from: 2013-02-13 Created: 2013-02-13 Last updated: 2017-12-06Bibliographically approved
2. DNA methylation pattern of the SLC25A43 gene in breast cancer
Open this publication in new window or tab >>DNA methylation pattern of the SLC25A43 gene in breast cancer
2012 (English)In: Epigenetics, ISSN 1559-2294, E-ISSN 1559-2308, Vol. 7, no 3, p. 300-306Article in journal (Refereed) Published
Abstract [en]

Solute carrier family 25A member 43 (SLC25A43) gene is a putative tumor suppressor gene that undergoes loss of heterozygosity (LOH) in human epidermal growth factor receptor 2 (HER2) positive breast cancer. Also, knockdown of SLC25A43 in cell lines influences cell turnover and metabolism. Absence of mutations in this gene in breast cancers prompted us to study methylation as an alternate mechanism for gene inactivation of this X encoded gene. Quantification of CpG site methylation using pyrosequencing was performed upstream of the SLC25A43 gene and at its 5' end in a cohort of breast tumor tissues (n = 80, HER2 positive or negative) with different SLC25A43 gene deletion status. Compared with control tissue, cancer tissues had lower levels of methylation at the 5' and 3' shores of the gene. Cancer tissues with no deletion in the SLC25A43 gene (Del(-)) had higher methylation in the CpG island (CGI) of the gene than cancers carrying the deletion (Del(+)). Methylation in the CGI of the SLC25A43 gene was negatively correlated with age at diagnosis. In HER2 positive breast cancer, ER negativity and lymph node positivity was associated with higher methylation in the CGI and in the adjacent shores of this gene. Our results suggest that methylation in the CGI of the SLC25A43 gene could be an alternate mechanism of gene silencing in the absence of LOH. Also, associations between site-specific methylation and clinicopathological parameters suggest that epigenetic changes in SLC25A43 gene could be of importance in breast carcinogenesis.

Place, publisher, year, edition, pages
Austin, USA: Landes Bioscience, 2012
Keywords
Breast cancer, CpG island, CpG shore, gene inactivation, HER2 receptor, methylation, SLC25A43 gene
National Category
Medical and Health Sciences Cancer and Oncology
Research subject
Medicine
Identifiers
urn:nbn:se:oru:diva-22553 (URN)10.4161/epi.7.3.19064 (DOI)000301428800011 ()22430806 (PubMedID)2-s2.0-84858205498 (Scopus ID)
Funder
Swedish Cancer Society
Note

Funding Agencies:

Nyckelfonden Örebro, Sweden 

Lions Cancer Foundation, Sweden 

Available from: 2012-04-16 Created: 2012-04-16 Last updated: 2017-12-07Bibliographically approved
3. Whole genome DNA methylation signature of HER2-positive breast cancer
Open this publication in new window or tab >>Whole genome DNA methylation signature of HER2-positive breast cancer
(English)Manuscript (preprint) (Other academic)
Abstract [en]

With the aim of obtaining a more comprehensive epigenetic signature in HER2-positive breast cancer (HER2+ breast cancer), we performed a genome-wide methylation analysis on 17 HER2+ breast cancer and compared to 10 normal breast tissue samples using the Illumina Infinium HumanMethylation450 BeadChip that interrogates >485,000 CpG loci per sample. Our findings show that altered DNA methylation, more specifically hypermethylation occur at CpG islands in HER2+ breast cancer affecting genes involved in multicellular development, differentiation and transcription, and was overrepresented by the homeobox family of genes, including those which have not been previously reported in relation to cancer (DBX1, NKX2- 6, SIX6). Alteration in methylation was also found to affect genes of the PI3K and the Wnt signalling pathways in HER2+ breast cancer. Notably among them are HER2, AKT3, HK1 and PFKP, in which altered methylation has not been previously reported. We have identified 73 candidate biomarker genes in HER2+ breast cancer and external validation of gene expression in a selected group of these genes (n=13) revealed lowered mean gene expression in HER2+ breast cancer. Future clinical studies focusing on these candidate biomarker genes as well as homeobox-containing genes and HER2, AKT3, HK1 and PFKP are warranted which could provide further insights to the biology of HER2+ breast cancer.

Keywords
Breast cancer, HER2 receptor, DNA methylation, Illumina Infinium HumanMethylation450 BeadChip, CpG island, Homeobox genes
National Category
Medical and Health Sciences
Research subject
Biomedicine
Identifiers
urn:nbn:se:oru:diva-29134 (URN)
Available from: 2013-05-22 Created: 2013-05-22 Last updated: 2017-10-17Bibliographically approved
4. Cytoplasmic pFOXO3a expression is associated with sentinel node metastasis in HER2-positive breast cancer
Open this publication in new window or tab >>Cytoplasmic pFOXO3a expression is associated with sentinel node metastasis in HER2-positive breast cancer
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Introduction: Breast cancers with human epidermal growth factor receptor (HER) 2 gene amplification or protein overexpression (HER2+ breast cancer) is associated with poor prognosis. Activated HER2 receptors dimerise and activate the oncokinase Akt; which phosphorylate the tumour suppressor protein Forkhead box O3a (FOXO3a), repressing its transcriptional activity. Oncogenic FOXG1 can act as a transcriptional repressor for genes which are transcriptionally activated by FOXOs and phosphorylation of FOXG1 via Akt causes its nuclear export in differentiated cells. To better understand the AKT/FOXO3a/FOXG1 connection and their clinical relevance, we investigated the expression and localisation of pAkt, pFOXO3a and FOXG1 in HER2+ breast cancer.

Methods: Immunohistochemical analysis was performed to determine the expression and localisation of pAkt, pFOXO3a and FOXG1 on tissue microarray constructs from HER2+ primary breast tumours (n=91) and their relation to clinic pathological parameters were analysed.

Results: Nuclear expression of pAkt was found to be correlated to nuclear (p<0.001) as well as cytoplasmic expression of pFOXO3a (p = 0.006), while cytoplasmic expression of pAkt was found to be correlated to cytoplasmic expression of pFOXO3a (p<0.001). Nuclear expression of pFOXO3a was inversely correlated to cytoplasmic expression of FOXG1 (p=0.003). Cytoplasmic expression of pFOXO3a was found to be associated with sentinel node metastasis (p=0.011), while cytoplasmic FOXG1 expression was correlated to negative progesterone receptor status (p=0.008).

Conclusion: Our results suggest that the expression and localisation of pAkt and pFOXO3a is interconnected, while the expression of FOXG1 is connected to pFOXO3a. Our findings indicate the biological value of expression as well as localisation of these proteins in HER2+ breast cancer.

Keywords
HER2+ breast cancer, pAkt, pFOXO3a, FOXG1, Immunohistochemistry
National Category
Medical and Health Sciences
Research subject
Biomedicine
Identifiers
urn:nbn:se:oru:diva-29135 (URN)
Available from: 2013-05-22 Created: 2013-05-22 Last updated: 2017-10-17Bibliographically approved

Open Access in DiVA

sammanfattning(1248 kB)791 downloads
File information
File name SUMMARY01.pdfFile size 1248 kBChecksum SHA-512
4ecb715db584b69708f628771c398abb7990f9246977fcf6a4efb63927e20ec0a40423ec883fd4cd6ad1801cc01e90a5a3f3bae44fb82c5e3f667df9b2c64ef7
Type summaryMimetype application/pdf
omslag(1592 kB)71 downloads
File information
File name COVER01.pdfFile size 1592 kBChecksum SHA-512
60b76104cc7508f359b81599277dc50517a3187b0940f919dfaeda6eec35cf59f59d0eecf040d4d033d2f0ca828cb79cb7dbe1d719df02d3f0ff0bc917192415
Type coverMimetype application/pdf
spikblad(174 kB)14 downloads
File information
File name SPIKBLAD01.pdfFile size 174 kBChecksum SHA-512
d00ddbf93ccfc5495d8bd3542c621a42e51a07450d4541cf1b338bfa72f22c3d9bd274c4e6307a7b69d75c7c48a5021118ae0c65d3c1a68c90e0bfdf2160d6e0
Type spikbladMimetype application/pdf

Authority records BETA

Lindqvist, Breezy Malakkaran

Search in DiVA

By author/editor
Lindqvist, Breezy Malakkaran
By organisation
School of Health and Medical Sciences, Örebro University, Sweden
Medical and Health Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 189 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf