Organized proteomic heterogeneity in colorectal cancer liver metastases and implications for therapies

Abstract

Tumor heterogeneity is a major obstacle for developing effective anticancer treatments. Recent studies have pointed to large stochastic genetic heterogeneity within cancer lesions, where no pattern seems to exist that would enable a more structured targeted therapy approach. Because to date no similar information is available at the protein (phenotype) level, we employed matrix assisted laser desorption ionization (MALDI) image-guided proteomics and explored the heterogeneity of extracellular and membrane subproteome in a unique collection of eight fresh human colorectal carcinoma (CRC) liver metastases. Monitoring the spatial distribution of over 1,000 proteins, we found unexpectedly that all liver metastasis lesions displayed a reproducible, zonally delineated pattern of functional and therapeutic biomarker heterogeneity. The peritumoral region featured elevated lipid metabolism and protein synthesis, the rim of the metastasis displayed increased cellular growth, movement, and drug metabolism, whereas the center of the lesion was characterized by elevated carbohydrate metabolism and DNA-repair activity. From the aspect of therapeutic targeting, zonal expression of known and novel biomarkers was evident, reinforcing the need to select several targets in order to achieve optimal coverage of the lesion. Finally, we highlight two novel antigens, LTBP2 and TGFBI, whose expression is a consistent feature of CRC liver metastasis. We demonstrate their in vivo antibody-based targeting and highlight their potential usefulness for clinical applications. Conclusion: The proteome heterogeneity of human CRC liver metastases has a distinct, organized pattern. This particular hallmark can now be used as part of the strategy for developing rational therapies based on multiple sets of targetable antigens. (HEPATOLOGY 2014;59:924-934) See Editorial on Page 757 D espite its great promise, clinically used targeted cancer therapy is unfortunately showing only limited success at a very high cost. 1 This failure is partly explained by the high level of genetic heterogeneity of malignant lesions and the fact that carcinogenesis is an evolutionally driven process that recapitulates Darwin's theory of selection of the fittest. 2 In such an unfavorable context, targeted therapy protocols are reaching only a subpopulation of tumor cells, leading to a punctual increase in the selective pressure, fueling resistance to therapy, and thus failing to cure the patient. 3 The notion of tumor heterogeneity and the apparent random distribution of tumor cells harboring different mutations are supported by recent genetic studies. [4][5][6] However, the lack of information at the protein level limits the understanding of how genetic Abbreviations: CRC, colorectal cancer; MALDI, matrix assisted laser desorption ionization; MS, mass spectrometry. From the

Multiplexed single cell protein expression analysis in solid tumours using a miniaturised microfluidic assay

“…The heterogeneity of the expression level of an oncogenic protein, as well as its post-translationally modified isoforms, may have implications for the progression of tumour development, affecting tumour promoting factors such as angiogenesis, the epithelial to mesenchymal transition, resistance to chemotherapy and likelihood of metastasis [11]. Furthermore, identifying heterogeneous expression of protein drug targets may be a useful method of stratifying patients by the likelihood of response to particular therapeutic interventions [12,13]. The significance of heterogeneous subpopulations can be realised by correlating the proteomic data to therapeutic and other clinically relevant outcomes.…”

Therapy Response of Chinese Herbal Medicine in Advanced Liver Cancer: A Retrospective Observational Clinical Trial

“…CTC (circulation tumor cells) may be associated with recurrence of liver cancer. Researchers believe that the liver cancer stem cells do exist, and may be the target of target therapy of liver cancer [5].…”

“…Tumor heterogeneity is a major obstacle for developing effective anti-cancer treatments. Recent studies suggested large stochastic genetic heterogeneity within cancer lesions, where no pattern seems to exist that would enable a more structured targeted therapy approach [5]. Efforts to develop more effective drugs for therapy on critical ill patients of advanced liver cancer have been intensified.…”

Intratumoral heterogeneity and consequences for targeted therapies

“…active glucose metabolism), in the ulcer floor (stress response) and in the invasive front (apoptosis). We have recently utilized MALDI-imaging to guide proteomics for analysis of defined regions of interest in human colorectal carcinoma liver metastases (CRC-LM) [48]. Namely, MALDIimaging allowed the identification of a certain pattern of peptide distribution in CRC-LM, subdividing the lesion in several zones.…”

“…This shift from targeting pure function towards inducing massive damage will certainly profit from new proteomic findings showing that tumor heterogeneity can be targeted in a meaningful fashion. We have in our study [48] named several clinically approved antibodies and quantified their distribution in CRC-LM. Based on this information, it should be conceivable to combine several targeted treatments and test this in reliable preclinical models.…”