Quantitative In Vivo Monitoring of Hypoxia and Vascularization of Patient-Derived Murine Xenografts of Mantle Cell Lymphoma Using Photoacoustic and Ultrasound Imaging

Tumor oxygenation and vascularization are important parameters that determine the aggressiveness of the tumor and its resistance to cancer therapies. We introduce dual-modality ultrasound and photoacoustic imaging (US-PAI) for the direct, non-invasive real-time in vivo evaluation of oxygenation and vascularization of patient-derived xenografts (PDXs) of B-cell mantle cell lymphomas. The different optical properties of oxyhemo- globin and deoxyhemoglobin make it possible to determine oxygen saturation (sO2) in tissues using PAI. High- frequency color Doppler imaging enables the visualization of blood flow with high resolution. Tumor oxygenation and vascularization were studied in vivo during the growth of three different subcutaneously implanted patient- derived xenograft (PDX) lymphomas (VFN-M1, VFN-M2 and VFN-M5 R1). Similar values of sO2 (sO2 Vital), determined from US-PAI volumetric analysis, were obtained in small and large VFN-M1 tumors ranging from 37.9 § 2.2 to 40.5 § 6.0 sO2 Vital (%) and 37.5 § 4.0 to 35.7 § 4.6 sO2 Vital (%) for small and large VFN-M2 of VFN-M5 R1 tumors corresponds with the higher aggressiveness of that PDX model. The different tumor per- PDXs. In contrast, the higher sO2 Vital values ranging from 57.1 § 4.8 to 40.8 § 5.7 sO2 Vital (%) (small to large) centage vascularization (assessed as micro-vessel areas) of VFN-M1, VFN-M2 and VFN-M5 R1 obtained by color growth and aggressiveness. The data obtained by color Doppler were validated by histology. In conclusion, US- Doppler (2.8 § 0.1%, 3.8 § 0.8% and 10.3 § 2.7%) in large-stage tumors clearly corresponds with their diverse PAI rapidly and accurately provided relevant and reproducible information on tissue oxygenation in PDX tumors in real time without the need for a contrast agent.