Poster S8 - Investigating Key Features of Multifocal and Multicentric Breast Cancer via Bioinformatics and a Model-on-a-Chip

Introduction: Breast cancer has been considered as the second contributor to cancer-related fatalities among women worldwide. Among different categories of breast tumors, multifocal and multicentric breast cancers (MMBC) tend to be more aggressive than unifocal tumors and are highly associated with lower survival rates, higher recurrence rates, and increased lymph node metastasis. The underlying mechanisms governing MMBC invasion and proliferation have remained unclear.

Materials and

Methods: In this study, we utilized the advances of bioinformatics to discover key gene expression clusters and functions governing MMBC. We accessed and analyzed published gene expression datasets related to MMBC. For example, dataset GSE79058 including gene expressions in 2 or more foci from 11 multifocal invasive lobular breast tumor patients was used to discover differential gene expression clusters and related functional pathways. Then, we employed spheroid technique and microfabrication technology to develop an MMBC model on-a-chip to broaden our understanding of MMBC migration and invasive behaviors. The optimal spheroid formation was achieved from MDA-MB-231 cells mimicking primary breast tumors; and a uniform chessboard-like pattern was designed and generated by UV photolithography of SU-8 2025 photoresist, on a glass slide to facilitate positioning and quantification of the spheroids’ responses. Single spheroid and double spheroids setups were introduced on the chip and embedded in a collagen gel that mimics the extracellular environment of the breast tissue. Migration and invasive responses of these spheroids were monitored and observed by imaging for up to 7 days.

Results, Conclusions, and Discussions: As the result of analyzing the dataset GSE79058, two distinct clusters of differentially expressed genes were identified, shedding light on key biological pathways which are intricately linked to MMBC. More significant genes were found in higher grade of MMBC. Functional pathway analysis revealed several closely related pathways that could be highly impacted by MMBC. Specifically, the PI3K-AKT signaling pathway exhibits differential expression across both grades, manifesting in both up-regulated and down-regulated gene clusters. This suggests a complex interplay of genes associated with this pathway, both upstream and downstream orientation.
For the MMBC on-chip model, spheroids were cultured and allowed to mature for 72hr prior to their introduction into the chip. The sprouting cells from the spheroid was observed after 24hr and more sprouting effect was observed on double spheroids setup than single one. Furthermore, observation from double spheroids setup showed that spheroids exhibited directional sprouting towards one another. Additionally, we found that two spheroids could move toward each other, with some eventually merging into a single and larger spheroid.
With the output of this study, we expect to broaden our knowledge of MMBC particularly the interactions across multiple tumors via analysis of published datasets and the on-chip model of MMBC. Via evaluating various cancerous features such as cell invasion, tumor movement, and necrotic formation, we can suggest key events of tumor development, malignant transformation, and spatial heterogeneity.

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