Noninvasive intravital high-resolution imaging of pancreatic neuroendocrine tumours

Abstract

Preclinical trials of cancer drugs in animal models are important for drug development. The Rip1Tag2 (RT2) transgenic mouse, a model of pancreatic neuroendocrine tumours (PNET), has provided immense knowledge about PNET biology, although tumour progression occurs in a location inaccessible for real-time monitoring. To overcome this hurdle we have developed a novel platform for intravital 3D imaging of RT2 tumours to facilitate real-time studies of cancer progression. Pre-oncogenic islets retrieved from RT2 mice were implanted into the anterior chamber of the eye (ACE) of host mice, where they engrafted on the iris, recruited blood vessels and showed continuous growth. Noninvasive confocal and two-photon laser-scanning microscopy through the transparent cornea facilitated high-resolution imaging of tumour growth and angiogenesis. RT2 tumours in the ACE expanded up to 8-fold in size and shared hallmarks with tumours developing in situ in the pancreas. Genetically encoded fluorescent reporters enabled high-resolution imaging of stromal cells and tumour cell migration. Sunitinib treatment impaired RT2 tumour angiogenesis and growth, while overexpression of the vascular endothelial growth factor (VEGF)-B increased tumour angiogenesis though tumour growth was impaired. In conclusion, we present a novel platform for intravital high-resolution and 3D imaging of PNET biology and cancer drug assessment.

SWIP—a stabilized window for intravital imaging of the murine pancreas

“…This is particularly challenging to accomplish for the pancreas, given its delicate composition, deep anatomical location and proximity to the diaphragm. To circumvent this challenge, a number of laboratories have investigated pancreatic processes ex vivo [37], with the pancreas being exteriorized from the body cavity [38], or using ectopic transplantation of tissues into sites more conveniently imaged, such as the eye [39], kidney [8] or subcutaneous tissue [40,41]. While recent advances have enabled intravital imaging of the pancreas, existing designs are still limited in either stability for long-term time-lapse imaging on the minutes time scale, or their ability to accommodate pancreata of a variety of sizes (e.g.…”

Volume imaging to interrogate cancer cell-tumor microenvironment interactions in space and time

“…This approach presents a robust platform to visualize cell-cell interactions in the living organism and may be seen as a straight forward alternative to test hypotheses in vivo that were gained in in vitro experiments, albeit restricted to questions where the role of the cancer-surrounding normal organ is neglected. Alternative xenograft-based approaches have visualized tumor cell behavior through cancer cell injection in the tongue ( 87 ), and engraftment in the eye ( 88 ) which allow noninvasive longitudinal IVM without the need of imaging windows.…”

Fluorescence Microscopy—An Outline of Hardware, Biological Handling, and Fluorophore Considerations

“…With the use of intravital microscopy, it has also become possible to visualise the inter-individual variability at a microscopic level in response to drug treatment. An advantage of intravital imaging is the continual monitoring of physiological changes over days and weeks, which is especially important in developmental cells [ 97 ], stem cell [ 115 , 116 ], and tumour biology [ 117 ]. Moreover, longitudinal intravital imaging can be performed with fluorescently labelled antibodies and dyes that can be intravenously injected for the simultaneous visualisation of, for example, individual lipid droplets and microvasculature in the liver [ 118 ], or even vessels in the femoral and calvarial marrow [ 119 ].…”