KRAS is a GTPase (similar to the \alpha subunit of G proteins) that activates signaling pathways that promote cell division. The KRAS gene is the most frequently mutated oncogene across human cancers. Gain of function mutations in KRAS typically occur at codons 12 and 13, which encode glycine amino acids in wild type KRAS. Some common KRAS mutants are:
KRASG12D: glycine (G) at codon 12 mutated to aspartate (D)
KRASG12V: glycine (G) at codon 12 mutated to valine (V)
KRASG13D: glycine (G) at codon 13 mutated to aspartate (D)
Cancer cells display peptides from mutant KRAS through their MHC molecules. T cells can recognize peptides with mutations (called neoantigens) as abnormal, which allows them to respond and act against other cancer cells displaying the same neoantigen.
PD-L1 is a cell surface protein expressed by several cell types that normally suppresses the adaptive immune response to prevent autoimmunity. It functions by binding to PD-1, a cell surface protein on T cells, to suppress T cell activity. Antibodies that block the PD-L1/PD-1 interaction (Anti-PD-L1 or Anti-PD-1) are currently in development or recently approved for use as therapies for several types of cancers.

The ratio of GDP- to GTP-bound mutant KRAS in cancer cells is lower than GDP- to GTP-bound wild type KRAS in normal cells.
A. True
B. False