TY - JOUR T1 - Association of <em>GSTP1</em> Methylation with Aggressive Phenotype in ER-positive Breast Cancer JF - Anticancer Research JO - Anticancer Res SP - 5617 LP - 5623 VL - 33 IS - 12 AU - TOMOHIRO MIYAKE AU - TAKAHIRO NAKAYAMA AU - NAOFUMI KAGARA AU - NORIAKI YAMAMOTO AU - YUKIKO NAKAMURA AU - YOKO OTANI AU - KUMIKO UJI AU - YASUTO NAOI AU - MASAFUMI SHIMODA AU - NAOMI MARUYAMA AU - ATSUSHI SHIMOMURA AU - KENZO SHIMAZU AU - SEUNG JIN KIM AU - SHINZABURO NOGUCHI Y1 - 2013/12/01 UR - http://ar.iiarjournals.org/content/33/12/5617.abstract N2 - Aim: We investigated the association of glutathione S-transferase P1 (GSTP1) expression and methylation status with clinicopathological characteristics of estrogen receptor (ER)-positive breast cancers. Materials and Methods: Primary ER-positive breast cancer patients (n=177, stage I-III) were retrospectively analyzed. A quantitative GSTP1 methylation assay was performed using DNA micro-dissected from formalin-fixed and paraffin-embedded (FFPE) breast surgical specimens and GSTP1 expression was examined immunohistochemically. Results: GSTP1 methylation index (MI) was higher for the following patient subsets: Large-size (p=0.029), high-grade (p=0.010), human epidermal growth factor receptor-2 (HER2)-positive (p=0.024) and Ki67-positive (p=0.001) patients. In addition, GSTP1 hyper-methylation was more frequently observed in the luminal-B than the luminal-A subtype (p&lt;0.001) and there was no significant difference in GSTP1 positivity between the two subtypes (p=0.150). Conclusion: GSTP1 methylation may well be associated with the pathogenesis of the biologically-aggressive phenotype in ER-positive breast cancer. ER -