Updated project metadata. KRAS is a well known tumor associated antigen. It???s a GTPase that functions as molecular switch in regulatory pathways responsible for proliferation and survival. It???s frequently mutated in a variety of cancers. One of the possible driver mutations is G12V substitution, which impairs KRAS GTPase activity and renders the mutants persistently in the GTP-bound active form, thereby promoting tumorigenesis and tumor malignancy. Its high frequency in cancers makes KRAS an attractive target for immunotherapy. We performed in vitro digestions of synthetic polypeptide corresponding to KRAS2-35 carrying the mutation with purified 20S proteasome. Samples were measured by LC-MS/MS.