33P - DNA methylation signature to identify trastuzumab response in HER2 breast cancer models

Date 04 May 2017
Event IMPAKT 2017
Session Welcome reception and Poster Walk
Topics Biomarkers
Breast Cancer
Translational Research
Presenter Sonia Palomeras
Authors S. Palomeras1, Á. Díaz Lagares2, A. Blancafort1, A. Sarrats1, A.B. Crujeiras Martinez2, J. Sandoval2, M. Rabionet1, A.L. Welm3, M. Esteller2, T. Puig1
  • 1Department Of Medical Science, University of Girona, 17003 - Girona/ES
  • 2Epigenetics And Cancer Biology Program (pebc), Idibell, Hospital Duran i Reynals, 08908 - L'Hospitalet de Llobregat, Barcelona/ES
  • 3Oncological Sciences, Huntsman Cancer Institute, UT 84112 - Salt Lake City/US



The major clinical problem of HER2 breast cancer target therapies is the resistance acquisition. Despite initial good response to trastuzumab (Herceptin), up to 62% patients develop resistance within a year. The DNA methylation status of promoter genes regions has been described as a common epigenetic alteration for silencing or activation of transcriptional repression in human malignancies as Breast cancer. The aim of our study was to determine a DNA methylation profile with potential to predict trastuzumab response in HER2 breast cancer patients.

To understand the epigenetic changes that may be associated with trastuzumab resistance a DNA methylation status by Infinitum Human Methylation 450K array was performed in trastuzumab-sensitive (SK) and resistant cells (SKTR), previously developed in our laboratory. We considered differences between methylation groups of ≥60%. Expression array data (RNAseq) of the same cell lines were also included to determine the maximum number of biomarkers. Venn diagram was performed between RNAseq and DNA methylation array. The function associated to genes were analysed by Gene Ontology. The DNA methylation and expression status were validated by expression techniques (qPCR) and demethylation agent (5-aza-DC) treatment. DNA methylation promoter of candidate genes were determined by and methylation-specific PCR (MSP).

The DNA methylation microarray and expression array data showed different gene status between SK and SKTR cells. We selected five genes: TGFβ1, KILLIN, CXCL2, SLC38A1 and NR2F2. The expression and DNA methylation status of candidate genes in SKTR were in agreement with their expression observed by qPCR before and after 5-aza-DC treatment. Bisulfite pyrosequencing and MSP confirmed the CpG methylation profile of our candidate genes.

These results provide a basis for further studies to validate the hypermethylation status of these candidate genes as predictive or monitoring biomarkers of trastuzumab resistance in HER2 breast cancer patients.

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