Abstract P4-04-08: Histological and epigenetic analyses of placenta tissue from breast cancer patients and healthy participants
Authors: Fröhlich Karolin , Plösch Torsten , Seither Fenja , Müller Volkmar , Karn Thomas , Stickeler Elmar , Schem Christian , Solbach Christine , Lupp Amelie , Verkaik-Schakel Rikst N , Turowski Gitta , Mallmann Peter , van Mackelenbergh Marion , Sinn Bruno , Nekljudova Valentina , Denkert Carsten , Schittler Pamela , Markert Udo , Loibl Sibylle 
Published: March 2020

Abstract
Background: Breast cancer is one of the most common malignancies during pregnancy. Guidelines for breast cancer treatment during pregnancy demonstrating that breast cancer during pregnancy can be treated similarly to non-pregnancy-associated breast cancer, except for hormonal and anti-HER2 therapies. Nonetheless, a decreased birth weight is often observed in newborns. Therefore, this project aims to analyze the effects of chemotherapy and the impact of cancer progression on the placenta. Methods: Placentas from breast cancer patients (n=63) and non-cancer participants (n=20) enrolled in Breast Cancer in Pregnancy (BCP) study were collected after delivery and embedded in paraffin. Sections were stained with Hematoxylin-Eosin (HE) and IHC (Ki-67, cPARP, p27Kip1); trophoblast morphology was evaluated by an established scoring system and distribution of immunohistochemical markers was assessed. Additionally, epigenetic analyses (cytosine methylation) for the following genes were performed: LINE-1 (general methylation), IGF2-H19 (birth weight), EPO (hypoxia), BDNF (neurobiological development), glucocorticoid receptor, HSD11B2 (inactivation of glucocorticoids), estrogen receptor, P-glycoprotein, CYP-3A4 (drug metabolism). Results: HE staining revealed significant damage of trophoblast nuclei and membranes in placentas from breast cancer patients compared to controls (mean score of damage 1.9/1.8 vs 0.8/0.7, p&lt;0.001). Simultaneously, mean proliferation index (Ki-67 positive cells/ 1000 trophoblasts) was reduced (36.3 vs 58.0, p&lt;0.001). In contrast, nuclear and cytoplasmic expression of the negative cell cycle regulator p27Kip1 was reduced (mean IRS score 1.0/0.9 vs 4.3/4.8, p&lt;0.001). No evidence of enhanced apoptosis was found. Epigenetic analyses showed significant differences in mean percentage of cytosine methylation of EPO (68.4% vs 71.1%, p&lt;0.05) and hCyp-3A4 (87.8% vs 90.0%, p&lt;0.01) gene. Altered methylation of CpG positions of LINE-1, IGF2-H19, HSD11B2, estrogen receptor and P-glycoprotein gene were found. Conclusions: Placentas from breast cancer patients seem to be harmed in contrast to placentas from normal pregnancies, shown by morphologic abnormalities and a decreased proliferation index. Nevertheless, no increase of apoptotic cells could be demonstrated. Altered expression of efflux pumps or drug-metabolizing enzymes might be a reason for good fetal tolerability of chemotherapy during pregnancy as methylation patterns were changed in P-glycoprotein and CYP-3A4 gene.
Citation Format: Karolin Fröhlich, Torsten Plösch, Fenja Seither, Volkmar Müller, Thomas Karn, Elmar Stickeler, Christian Schem, Christine Solbach, Amelie Lupp, Rikst N Verkaik-Schakel, Gitta Turowski, Peter Mallmann, Marion van Mackelenbergh, Bruno Sinn, Valentina Nekljudova, Carsten Denkert, Pamela Schittler, Udo Markert, Sibylle Loibl. Histological and epigenetic analyses of placenta tissue from breast cancer patients and healthy participants [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-04-08.