Study of the specificity and therapeutic properties of compound C19 in pre-clinical models of colorectal cancer

Colorectal cancer is the third most common cancer worldwide; in Mexico, there has been an upward trend in mortality rates from colorectal cancer over the past three decades. In 40% of all cases, KRAS4b-activating mutations occur. The PDEδ or phosphodiesterase 6δ is a cytoplasmic chaperone for KRAS4b, thus increasing its plasma membrane localization and activation. PDEδ downregulation prevents redistribution and activation of KRAS4b. Thus, targeting the KRAS4b-PDEδ complex is a treatment strategy for colorectal cancer. The molecule C19 and its iodinated analog called I-C19 bind and stabilize the KRAS4b-PDEδ complex. Using docking and molecular dynamics simulations coupled to molecular mechanics, the generalized born model and solvent accessibility approach to explore protein-ligand stability, we found that both the compound ((2S)N-(2,5-diclorofenil)-2-[(3,4-dimetoxifenil)metilamino]-propanamida), termed C19, and its iodinated analog ((2S)-N-(2,5-diiodofenil)-2-[(3,4-dimetoxifenil)metilamino]propanamida), termed I-C19, bound and stabilized the KRAS4b-PDEδ complex. Subsequently, we investigated whether both compounds decrease KRAS4b activation and its effectors. Moreover, we propose the I-C19 as a novel molecule with two functionalities in a single probe: the inhibition of KRAS4b signaling and radiotherapeutic activity against colorectal tumors. C19 and I-C19 showed high cytotoxicity in the colorectal cancer cell lines HCT, LoVo and SW620, with a stronger effect in KRAS-dependent cells (LoVo and SW620). The in vivo therapeutic potential of C19 and I-C19 in mouse (C57BL/6 and Nu/Nu mice for AOM/DSS and xenograft model respectively) colorectal cancer model was demonstrated. Furthermore, the radiation-absorbed dose produced by radiolabeled ¹³¹I-C19 to the colon cancer cell nucleus and the damage to DNA. The in vivo biokinetic profile was obtained. The radiation absorbed dose to the tumor was estimated. Collectively, the data presented in this research supports future clinical evaluation of C19 and I-C19 as potential molecules for treatment of KRAS4b-mutant colorectal cancer. (author)