Breast cancer’s 3D branching map

Breast tumors that spread do not grow as shapeless clumps. A Cell paper published in late March found that metastatic outgrowth follows an ordered three-dimensional branching program in which cancer cells build connected cords through tissue. (cell.com) The study, led by Stefano Piccolo and Maria Cordenonsi with colleagues at the University of Padua, Istituto Oncologico Veneto, and the AIRC Institute of Molecular Oncology, used single-cell ribonucleic acid sequencing, spatial transcriptomics, artificial-intelligence-assisted three-dimensional imaging, and mouse experiments. The authors reported that breast cancer macrometastases activate what they call a “metastatic trabecular morphogenesis” program. (cell.com) In plain terms, a metastasis is a new tumor that forms after cancer cells leave the breast and colonize another organ such as bone, lung, liver, or brain. The National Cancer Institute says metastatic breast tumors most commonly develop in those four sites. (cancer.gov) The Padua team said its three-dimensional reconstructions showed metastases expanding as “a delicate network of connected cellular cords” rather than as one dense round mass. The university said the work is part of an AIRC “5 per mille” program called “Metastasis as a mechanical disease.” (unipd.it) The paper ties that branching architecture to ETV family genes and fibroblast growth factor signaling, molecular switches that help cells turn developmental programs on and off. In the authors’ model, cancer cells reuse a branching routine more often associated with embryo and organ formation. (cell.com) That matters because most cancer deaths come after tumors spread, not while they remain confined to the original site. United States cancer surveillance data show about 6.0% of female breast cancers are diagnosed at a distant stage, and five-year relative survival is far lower once disease has spread. (cdc.gov) The National Cancer Institute says prognosis in breast cancer depends on factors including tumor size, lymph-node spread, grade, hormone receptors, human epidermal growth factor receptor 2 status, and treatment response. This study adds tissue shape and growth pattern to that picture by asking how cancer organizes itself in space, not only which mutations it carries. (cancer.gov) The authors also reported that this three-dimensional state was already present, selectively, in primary tumors that later metastasized. That raises the possibility that the branching pattern is not just a late feature of advanced disease but an early program that can be detected before distant growth is obvious. (cell.com) Piccolo said the shift from flat pathology slides to three-dimensional analysis changes what researchers can see and what interventions they can imagine. The paper closes on that same point: metastasis may be easier to understand when it is treated as built tissue with geometry, not just as a pile of abnormal cells. (unipd.it)