In vivo imaging of the tumor and its associated microenvironment using combined CARS / 2-photon microscopy.

The use of confocal and multi-photon microscopy for intra-vital cancer imaging has impacted on our understanding of cancer cell behavior and interaction with the surrounding tumor microenvironment in vivo. However, many studies to-date rely on the use fluorescent dyes or genetically encoded probes that enable visualization of a structure or cell population of interest, but do not illuminate the complexity of the surrounding tumor microenvironment. Here, we show that multi-modal microscopy combining 2-photon fluorescence with CARS can begin to address this deficit, enabling detailed imaging of the tumor niche without the need for additional labeling. This can be performed on live tumor-bearing animals through optical observation windows, permitting real-time and longitudinal imaging of dynamic processes within the tumor niche.