KRAS and metastatic colorectal cancer: Conclusively, the SP SPK1 is shown to be superior to SPKM19 for the secretion of KRAS peptides in L. lactis. The ability of the L. lactis in mediating successful secretion and elevated humoral immunity through KRAS-specific sIgA production represents a possibility for this vaccine host to be used as the delivery vehicle for future mucosal vaccine developments especially targeting metastatic colorectal cancer.