A 3D bioprinter platform for mechanistic analysis of tumoroids and chimeric mammary organoids.

The normal mammary microenvironment can suppress tumorigenesis and redirect cancer cells to adopt a normal mammary epithelial cell fate in vivo. Understanding of this phenomenon offers great promise for novel treatment and detection strategies in cancer, but current model systems make mechanistic insights into the process difficult. We have recently described a low-cost bioprinting platform designed to be accessible for basic cell biology laboratories. Here we report the use of this system for the study of tumorigenesis and microenvironmental redirection of breast cancer cells. We show our bioprinter significantly increases tumoroid formation in 3D collagen gels and allows for precise generation of tumoroid arrays. We also demonstrate that we can mimic published in vivo findings by co-printing cancer cells along with normal mammary epithelial cells to generate chimeric organoids. These chimeric organoids contain cancer cells that take part in normal luminal formation. Furthermore, we show for the first time that cancer cells within chimeric structures have a significant increase in 5-hydroxymethylcytosine levels as compared to bioprinted tumoroids. These results demonstrate the capacity of our 3D bioprinting platform to study tumorigenesis and microenvironmental control of breast cancer and highlight a novel mechanistic insight into the process of microenvironmental control of cancer.