Abstract P2-07-01: Hydroxytyrosol, a Component of Olive Oil for Breast Cancer Prevention in Women at High Risk
Authors: Puri Akshjot , Yin Zheng , Granados-Principal Sergio , Ensor Joe , Guzman Liliana , Rosato Roberto , Zhao Hong , Wong Stephen , Patel Tejal , Chang Jenny 
Published: March 2023

Abstract
Background Breast cancer is the most frequently diagnosed cancer in women in developed countries with increased incidence in women at high risk such as those with strong family history, BRCA mutations, atypical hyperplasia etc. Chemoprevention with drugs like tamoxifen and aromatase inhibitors come with challenges of intolerance and limited efficacy in estrogen receptor negative breast cancers. The purpose of our study was to evaluate the effects of hydroxytyrosol (HT), a component of olive oil on mammographic breast density reduction, which is a validated surrogate biomarker for breast cancer prevention as well as to explore on-target effects on Wingless-related integration site (Wnt) pathway, and alterations in key pathways of proliferation, DNA damage repair and stem cell function. Methods This study was conducted using 25mg/day oral dose of HT for 12 months in both pre- and post-menopausal women who are at increased risk of breast cancer with Gail 5-year risk score ≥ 1.67 and/or &gt; 10% probability of BRCA mutation and had declined standard chemoprevention. These women underwent annual mammograms as well as had the option to have a biopsy of normal breast tissue before and after HT. Maximum volumetric breast density (Max VBD%) was assessed quantitatively using Volpara software (VIS 3.2) and the annualized percent decrease in max VBD% between baseline (BL) and end of treatment (EOT) with HT was analyzed in the study. RNA was extracted from the breast biopsies and RNA sequencing (RNA-Seq) and multiplex analysis of 28 proteins using NanoString nCounter analysis was performed to compare the BL with EOT samples. Results A total of 61 women were screened for the trial, 51 were enrolled and 41 patients completed the study. Median age for the study population was 54 years (range 35-76 years). There were 26 patients with paired BL and EOT mammograms. There were 14 patients with paired BL and EOT breast biopsies and seven patients with only BL and seven with only EOT biopsies. Mammographic density as measured by max VBD% showed a non-significant change of -0.038%, p = 0.49. However, on subgroup analysis in women 60-years or older, the mean decrease in max VBD% was - 3.7% (p = 0.0391), especially in those with high baseline mammographic density (&gt; 10% baseline max VBD%). RNAseq data was generated from 15 BL and 17 EOT samples and pathways were confirmed by NanoString. Our bioinformatics pipeline identified 190 transcripts that were upregulated and 90 that were downregulated in EOT vs. BL by at least 1.5 fold. Reactome pathway R-HSA-195721 (Signaling by WNT) is identified as the top pathway enriched with EOT downregulated genes. On further review of the expression profiles, 82 of 261 member genes had p-value &lt; 0.05 for EOT vs. BL, among which only 4 were upregulated and 78 were downregulated in EOT samples. These 82 genes were highly interactive with each other, with 379 high confidence protein-protein interactions (PPIs) (confidence score &gt; 0.7 from STRING database) involving 81 out of 82 genes. In addition, mitotic telophase/cytokinesis (p = 0.004), ATM signaling (p = 0.007) were some pathways that were upregulated whereas, NOTCH signaling (p = 0.007), oxidative stress induced senescence (p = 0.0001) pathways were downregulated in EOT vs. BL. Conclusions Hydroxytyrosol, a component of olive oil did not show a decrease in breast density in the intention to treat population but showed some reduction in breast density in women 60-years of age and above, especially in those with high baseline breast density. HT showed on target effects by affecting Wnt signaling pathway, as well as decrease in proliferation. This study lays the foundation for future larger studies in exploring a natural compound such as HT for chemoprevention of breast cancer.
Citation Format: Akshjot Puri, Zheng Yin, Sergio Granados-Principal, Joe Ensor, Liliana Guzman, Roberto Rosato, Hong Zhao, Stephen Wong, Tejal Patel, Jenny Chang. Hydroxytyrosol, a Component of Olive Oil for Breast Cancer Prevention in Women at High Risk [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-07-01.