Histology-guided proteomic analysis to investigate the molecular profiles of clear cell Renal Cell Carcinoma grades

Renal Cell Carcinoma (RCC) is the most frequent form of kidney cancer and approximately 80% of cases are defined as clear cell RCC (ccRCC). Among the histopathological factors, tumour grade represents one of the most important parameters to evaluate ccRCC progression. Nonetheless, the molecular processes associated with the grading classification haven't been deeply investigated thus far. Therefore, the aim of this study was to uncover protein alterations associated with different ccRCC grade lesions. Formalin-fixed paraffin-embedded samples from ccRCC patients were analysed by histology-guided MALDI-MSI and shotgun proteomics in order to study the biological processes implicated in ccRCC. MALDI-MSI data highlighted signals able to discriminate among different grades (AUC > 0.8). The ion at m/z 1428.92 was identified as Vimentin and was overexpressed in grade 4 lesions, whereas ions at m/z 944.71, m/z 1032.78 and m/z 1325,99 were identified as histones H2A, H3, and H4, respectively. nLC-ESI-MS/MS analysis provided a further list of proteins and their abundances, showing a difference in protein content among the four grades. Moreover, the obtained molecular profiles showed a correspondence with the different Cancer-Specific Survival rate at 10 years post-surgery, as reported in literature. Significance: Despite the generally accepted role of tumour grade in ccRCC diagnosis, the proteomic processes associated with the different tumour grades has not been extensively studied and doing so may provide insights into the development of the disease. In the current study, data obtained using MALDI-MSI was integrated with that obtained using nLC-ESI-MS/MS to highlight the proteomic alterations underlying the different ccRCC grades. The combined approach identified vimentin and three histones (H2A, H3 and H4) that were able to discriminate among the four grades whilst the nLC-ESI-MS/MS analysis alone provided a further list of proteins with an altered abundance. Furthermore, there was a good correlation between the molecular profiles generated for each grade and the different Cancer-Specific Survival rate at 10 years post-surgery. Such findings could be a valuable starting point for further studies aimed at clarifying the molecular events that occur during the development of ccRCC.