A bioprinted breast cancer model using bioinks of decellularized breast tissue for studying cancer stemness, invasion, and drug efficacy.

Breast cancer 3D in vitro systems that replicate key tumor characteristics could assist drug discovery by providing more clinically translational models. Breast tumors are formed by hierarchically organized cancer and stromal cells and the extracellular matrix, all of which contribute to the disease progression and treatment response. 3D-bioprinting has enabled the creation of anatomically relevant constructs that better recapitulate the tumor architecture. The extracellular matrix's role in the tumor outcome has motivated the development of biomimetic bioinks. Among them, bioinks based on decellularized mammary glands can mimic many native biological cues. This work aims to develop a bioprinted 3D in vitro model of breast cancer using a biomimetic bioink based on decellularized mammary glands, and to investigate the effect of this bioink on the malignancy and drug resistance of breast cancer cells. The biomimetic bioink supported cell stemness, invasion, and an immunosuppressive environment but did not promote drug resistance. We also tested the effect of supplementing the bioink with collagen I, which is highly expressed in breast cancer, on breast cancer cells. We observed a higher expression of malignancy markers (COL1A1) and invasion markers (CDH2, MMP2). Next, we bioprinted a cancer model using human adipose mesenchymal stem cells and breast cancer cells to replicate tumor anatomy. These bioprinted models exhibited enhanced resistance to doxorubicin, particularly in the case of the bioink supplemented with collagen I. Therefore, supplementing the bioink with collagen I can promote the creation of more relevant cancer models for drug screening. STATEMENT OF SIGNIFICANCE: Bioprinted 3D in vitro tumor models are emerging as key tools for drug discovery, as they effectively replicate key tumor characteristics. We developed a bioprinted breast cancer model replicating the tumor structure and extracellular matrix, using a biomimetic bioink based on decellularized mammary glands (TDM) and collagen I. The model consisted of a core of cancer cells surrounded by a layer of mesenchymal stem cells (MSCs). Our findings indicate that TDM-based bioinks enhanced the malignant behavior of the breast cancer cells and promoted the differentiation of MSCs towards cancer-associated fibroblasts. Moreover, cancer cells exhibited increased resistance to chemotherapy in this model, highlighting the importance of mimicking the tumor structure and extracellular matrix in creating more physiologically relevant tumor models.