In chemotherapy-treated breast cancer, wild-type p53 preferentially induces senescence over apoptosis, resulting in a persisting cell population constituting residual disease that drives relapse and poor patient survival via the senescence-associated secretory phenotype. Understanding the properties of tumor cells that allow survival after chemotherapy treatment is paramount. Using time-lapse and confocal microscopy to observe interactions of cells in treated tumors, we show here that chemotherapy-induced senescent cells frequently engulf both neighboring senescent or nonsenescent tumor cells at a remarkable frequency. Engulfed cells are processed through the lysosome and broken down, and cells that have engulfed others obtain a survival advantage. Gene expression analysis showed a marked up-regulation of conserved macrophage-like program of engulfment in chemotherapy-induced senescent cell lines and tumors. Our data suggest compelling explanations for how senescent cells persist in dormancy, how they manage the metabolically expensive process of cytokine production that drives relapse in those tumors that respond the worst, and a function for their expanded lysosomal compartment.

Epithelial-adipose interaction is an integral step in breast cancer cell invasion and progression towards lethal metastatic disease. Understanding the physiological contribution of obesity, a major contributor to breast cancer risk and negative prognosis in post-menopausal patients, on cancer cell invasion requires detailed co-culture constructs that reflect mammary microarchitecture. Using laser direct-write, a laser-based CAD/CAM bioprinting technique, we have demonstrated the ability to construct breast cancer cell-laden hydrogel microbeads into spatially defined patterns in hydrogel matrices containing differentiated adipocytes. Z-stack imaging confirmed the three-dimensional nature of the constructs, as well as incorporation of cancer cell-laden microbeads into the adipose matrix. Preliminary data was gathered to support the construct as a potential model for breast cancer cell invasion into adipose tissue. MCF-7 and MDA-MB-231 breast cancer cell invasion was tracked over 2 weeks in an optically transparent hydrogel scaffold in the presence of differentiated adipocytes obtained from normal weight or obese patient tissue. Our model successfully integrates adipocytes and gives us the potential to study cellular and tissue-level interactions towards the early detection of cancer cell invasion into adipose tissue.

Laser-based three-dimensional (3D) printing methods, including laser direct-write cell printing and two-photon polymerization, have seen significant advances because of their unique photonic characteristics. Several mechanisms have been developed to increase the overall throughput of two-photon polymerization. Recent efforts to develop complex medically relevant structures using laser direct-write cell printing have also been demonstrated; for example, an ex vivo experimental platform for time-lapse imaging of cancer cell dynamics during angiogenesis within a microvascular network, which combines laser direct-write cell printing into the rat mesentery culture model; a model that simulates a 3D in vivo culture. Laser 3D printing methods hold significant promise for 3D printing of tissue engineering scaffolds, microstructured medical devices, and other medically relevant structures.

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Laser direct-write (LDW) bioprinting methods offer a diverse set of tools to design experiments, fabricate tissue constructs and cellular microenvironments all in a CAD/CAM matter. To date, we have just scratched the surface of the system’s potential. For LDW to be utilized to its maximum there are many distinct hardware and software components that must integrate and communicate seamlessly. In this perspective articles, we detail the development of novel graphical user interface (GUI) software to improve laser direct-write capability and functionality. The main modules in the control software correspond to cell transfer, microbead fabrication, and micromachining. Modules make the control of each of these features and the management of printing programs that utilize one or more features facile. The software also addresses problems related to construct scale-up, print speed, experimental conditions, and management of sensor data. The control software and possibilities for integrated sensor data are presented.

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