Honokiol enhances the sensitivity of cetuximab in KRASG13D mutant colorectal cancer through destroying SNX3-retromer complex

Rationale: the proto-oncogene KRAS is frequently mutated in colorectal cancer (CRC), leading to inherent resistance against monoclonal antibodies targeting the epidermal growth factor receptor (EGFR), such as cetuximab. Therefore, addressing the primary resistance and expanding the indications for target therapy have become critical challenges./nMethods: the screening of a natural product library against KRAS mutant CRC cells was conducted, leading to the discovery of a small molecule compound that sensitive to the KRAS^G13D mutation site. The anti-tumor activity of this small molecule compound in combination with cetuximab was evaluated using the KRAS^G13D mutant CRC models both in vivo and in vitro. This evaluation includes an examination of its effects on cell proliferation, viability, apoptosis, cell cycle progression, and tumor growth. Furthermore, RNA sequencing, western blot analysis, immunofluorescence, real-time quantitative PCR, and pull-down assays were employed to explore the molecular mechanisms underlying the synergistic anti-tumor effect of this small molecule compound in combination with cetuximab./nResults: our study screened 882 compounds in KRAS mutant CRC cells and identified honokiol, a small molecule compound that exhibits specific sensitivity to KRAS^G13D mutant CRC cells. Furthermore, we revealed that the synergistic augmentation of cetuximab's sensitivity in vivo and in vitro models of KRAS^G13D mutant CRC in combination with honokiol. Mechanistically, honokiol suppresses SNX3-retromer mediated trafficking, thereby impeding lysosomal proteolytic capacity and inhibiting autophagy and macropinocytosis fluxes. Moreover, honokiol inhibits the conversion of RAS GDP to RAS GTP, heightening the susceptibility of KRAS^G13D CRC mutant cells to cetuximab./nConclusions: honokiol enhances the sensitivity of cetuximab by destroying SNX3 retromer in KRAS^G13D mutant CRC preclinical model. These findings present a promising strategy for expanding the indications of target therapy in KRAS mutant colorectal cancer patients.