Characterizing breast cancer mouse xenografts with T₁ρ -MRI: a preliminary study

Previously three imaging methods, dynamic contrast enhanced magnetic resonance imaging (DCE-MRI), T(1ρ )-MRI, and low temperature NADH/Fp (reduced nicotinamide adenine dinucleotide/oxidized flavoprotein) fluorescence imaging (redox scanning)were reported to differentiate the mouse xenografts of a less metastatic human melanoma cell line A375P and a more metastatic line C8161. The more metastatic melanoma is characterized by less blood perfusion/permeability and more oxidized mitochondrial redox state in the tumor core and lower T(1ρ ) relaxation time averaged across the tumor section. These features may be useful for identifying imaging biomarkers for cancer metastatic potential. Here, we have employed T(1ρ )- and T2-weighted MRI to image mouse xenografts of two human breast cancer lines (more metastatic MDA-MB-231 and less metastatic MDA-MB-468) on a vertical bore 9.4- T Varian MR system. The preliminary results indicated that the more metastatic MDA-MB-231 tumors had shorter T(xρ ) relaxation constants on average than the less metastatic MDA-MB-468 tumors, and T(xρ ) relaxation might be a potential biomarker of breast tumor metastatic potential. Distinct ring-like structures were observed on T(xρ )-weighted MR images of the breast tumors, indicating tumor core and rim difference. This observation appears to be consistent with the tumor core-rim difference previously observed by DCE-MRI and redox scanning on aggressive melanoma xenografts.