Defining the molecular tumor margin regions of clear cell renal carcinoma tissues by MALDI-MS imaging of lipid and glycan species.

Abstract

421 Background: The frequent tumor recurrence associated with clear cell renal cell carcinoma (ccRCC) suggests that there are underlying molecular processes present in the remaining tissue following nephrectomy that are not identified through conventional histopathological techniques. At the molecular level, transcript, metabolomic, and protein expression patterns have indicated a striking Warburg Effect profile in ccRCC tissues, with major affects on sugar and lipid metabolism. Our group has been applying MALDI mass spectrometry imaging approaches to uniquely profile lipids and glycans associated with disease progression directly in frozen tissue slides. Methods: Frozen ccRCC tissues with tumor, non-tumor adjacent, and tumor margin regions were selected by a pathologist. Lipid profiles from fresh-frozen tissue slides coated in DHB matrix were obtained on a dual source Bruker Solarix 70 FTICR mass spectrometer. Glycans were imaged in a similar fashion in ethanol-washed tissues using on-tissue protein N glycanase F digestion to release surface N-glycans. Detected lipid and glycan ion intensities were converted to a color pixel scale for creating an image of individual peaks, linked directly to the histopathology of the tissue. Results: Five groups of lipid and N-glycan species were identified following MALDI tissue imaging, those present in the immediate margin area of non-tumor tissue adjacent to tumor; only in non-tumor regions; only in tumor regions; primarily in tumor regions but extended beyond the margin; and present throughout the tissue. Specific lipid and glycan species associated with margin and tumor regions are being correlated with disease progression and pathology data. Conclusions: Analysis of the periphery of the tumor tissue and the normal parenchyma or capsule regions at this biomolecule level may better define the metastatic potential of the tumor as compared to analysis of the central tumor region. This approach has the potential to not only improve prognostic assessment and treatment choices, but also to inform on the underlying biology of ccRCC metastasis and new rational targets for therapeutic intervention.