Imaging Guided Proteomics Unveils Heterogeneity in Colorectal Carcinoma Liver Metastases – Implications for Targeted Therapies

Patients suffering from liver metastases are diagnosed late and have a poor outcome. Targeted therapies are promising treatment options, however the malignant lesions are heterogeneous in nature offering niches for cancer cells to survive and regrow. A rational strategy is needed to select targetable antigens that would overcome this intra-tumoral heterogeneity. MALDI-MS imaging is an emerging tool to study the distribution of biomolecules in tissue samples and is a good base for defining the regions of interest (ROI) that deserve further in-depth analysis.

We employed MALDI-MS imaging of colorectal liver metastasis to identify ROI and guide the proteomic analysis for a more in-depth picture of modulated proteins. The focus was laid on cell membrane and extracellular proteins as these have enhanced potential to be used for targeted therapy and clinical imaging applications. Four defined ROI were further analyzed employing 2D-Nano-UPLC-MSe methodology. Over 1500 unique proteins were statistically divided into different patterns of expression, generating a quantitative picture of the proteome heterogeneity in liver metastases.

The results offered insight into novel targets but also antigens against which the antibodies are already involved in cancer clinical trials. Following immunohistochemistry based validation experiments, certain proteins demonstrated the potential to homogeneously cover the metastatic lesion and become better targets. Two such antigens, LTBP2 and TGFBI were selected for in vivo functional/ tumor targeting studies in colorectal carcinoma animal model. Importantly, we were able to demonstrate the “targetable” nature of these antigens for homing antibodies injected i.v. Functionally, TGFBI showed an additional potential to target the tumor via it’s ability to affect migration and growth of cancer cells, hence taking the influence on the process of tumorigenesis.

In conclusion, liver metastases display a significant heterogeneity in terms of targetable biomarkers and these findings should flow in the future development of targeted therapies aiming to cure the patient.