P-109 Broaden the Therapeutic Opportunities for Colorectal Cancer: ALK Inhibition Benefits Consensus Molecular Subtype 1 Patients

Colorectal cancer (CRC) is characterized by specific molecular features that contribute to a significant degree of inter-individual heterogeneity. This heterogeneity underscores the need for personalized medicine to treat patients effectively. The Consensus Molecular Subtypes (CMSs) classification stratifies CRC into four well-defined molecular subgroups, providing support to the use of targeted therapies. Unfortunately, so far only a few targetable biomarkers are known in the CRC setting, leaving a big portion of patients not eligible for any individualized treatment regimen. Through a bioinformatic meta-analysis of a dataset of 1700 CMS-stratified CRC patients, we determined that high levels of anaplastic lymphoma kinase (ALK) expression were negatively correlated with relapse-free survival (RFS) exclusively in the CMS1 subtype1. Conversely, we did not observe such a correlation in the other 3 subgroups. Stemming from these observations, we generated the hypothesis that ALK pharmacological inhibition may elicit therapeutic potential in CMS1 patients. Thus, we tested both small ALK-TKIs and an ALK-directed antibody-drug conjugate (ADC) on many CRC models stratified according to the CMS classification, through several in vitro (2D-3D) and in vivo assays. To unveil the mechanism, we applied single-cell sequencing on CRC patients and tested for the abundance of ALK ligands. Notably, ADC-based inhibition of ALK had a remarkable effect in mice, by blunting tumor growth. This may be due in part to the activity of the two ALKAL1 and ALKAL2 ligands, which activate ALK signaling and may contribute to the initiation of cell migration and invasion, thus facilitating metastatic spread. Interestingly, by single-cell RNA sequencing, we found that the above-mentioned ligands are expressed both in the epithelial tumor tissue and in the cancer-associated fibroblasts, suggesting a paracrine secretion sustaining cancer cells, which may explain the stronger efficacy of the ADC compared to the TKIs. Mechanistically, we found that CMS1 cells display several mRNA copies of both ALK and ALKAL2 ligand, along with a higher ALK protein amount compared to the other subtypes, suggesting a role for ALK abundance in the differential response to its inhibition. Collectively, our data suggest that ALK inhibition by means of ALK-directed antibody-drug conjugate may represent an attractive target that may broaden the therapeutic opportunities for CMS1 colorectal cancer patients.