Abstract A043: Building a mammary-specific microenvironment for investigating sex hormones in microvessels and tumors
Authors: Moccia Carmen , Cherubini Marta , Frigieri Guido , Haase Kristina 
Published: February 2024

Abstract
The mammary gland is highly vascularized and is exposed to alterations in sex hormones, including estrogen (E2) and progesterone (P4), which also play a role in breast cancer development and progression. Yet, our understanding of hormonal changes on the microvasculature in mammary tissue is limited to studies in rodents and simple 2D cultures. Advances in organ-on-chip technology now allow for models of 3D human microvessels to be generated. However, most microvascular models lack tissue-specific cell types, limiting their physiologic relevance. Thus, we first aimed to generate a tissue-specific breast microvasculature, and next used this model to study the impact of sex hormones. Our final goal is to generate a combined vascularized model of luminal A tumor on-chip. In our recently archived work (doi: 10.1101/2023.04.21.537664), we achieved the first in vitro perfusable breast-specific microvessels. Optimal conditions were achieved to co-culture human mammary vascular endothelial cells HMVEC and mammary fibroblasts on-chip. Through image-based quantification, microvessel morphology, not barrier function, was shown to be strongly influenced by the abundance of fibroblasts, which were critical to achieve lumenized (patent) vessels. Attaining perfusable microvessels allowed the study of discreet phases of the menstrual cycle (period, follicular, ovular, and luteal). The most striking results were observed with high concentrations of E2 (mimic of ovulation phase), which presented with increased vascular growth, and in contrast with high concentrations of P4 (mimic of luteal phase) that resulted in vascular rarefaction (pruning). Effects from combined E2 and P4 were dose-dependent, as demonstrated by significant branching and remodeling in the follicular phase. Hormonal effects were also tissue-specific, as shown by HUVEC-derived microvessels with significantly different morphologic phenotypes in comparison to HMVEC. Interestingly, fibroblasts expressed significantly high levels of receptors for both hormones and likely are major contributors to the hormone-responsiveness of microvessels. With mammary vessels now established, model tumors, spheroids, were generated from luminal-like breast cancer cells. Namely, MCF-7 and T47D, were treated by the same E2 and P4 conditions as in the microvessels. For both tumor spheroids, phase-dependent responses were observed, with high E2 resulting in the most significant growth. Ongoing work has shown the capacity to incorporate these tumor spheroids into our microvascular model, which results in varied local changes in vascular density. Future work involves investigating the role of hormones in the combined tumor-microvascular model. This complex humanized model will be useful in highlighting potential cancer treatment timelines (relevant to female menstrual cycle) and may be used to uncover novel therapeutic targets for luminal A breast cancers.
Citation Format: Carmen Moccia, Marta Cherubini, Guido Frigieri, Kristina Haase. Building a mammary-specific microenvironment for investigating sex hormones in microvessels and tumors [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr A043.