Development of precise cancer therapy requires detection of tumor-specific biomarkers. Peptides derived from various oncogene-associated proteins can be presented on cell surfaces as peptide-Major Histocompatibility Complexes (pepMHCs), which are potentially the largest cancer biomarker repertoire. However, there is a large gap between discovery studies of these peptide biomarkers and their clinical translation due to a lack of targeting system. I will develop a platform to recognize and track tumor pepMHCs with computationally designed small stable proteins, mimicking the function of T-cell receptors (TCR). The novel targeting system opens up opportunities for tracking intracellular oncogenic biomarkers for immunotherapy treatment.