New algorithm of bioinformatic search for potential serum tumor markers has been worked out, including: (1) identification of microRNAs with the level of synthesis most evidently and often decreasing in tumors; (2) search for target mRNAs regulated by microRNAs; (3) selection of targets encoding secretory proteins; (4) comparative analysis of transcription level of the targets in normal and tumor tissues. Practical use of the algorithm has allowed us to detect seven potential serum markers of large intestine tumors: ADAMTS14, ANGPT2, CCL7, DEFA5, MMP11, MMP14, and PLAU. It has been experimentally indicated that the level of synthesis of two of seven proteins (MMP14 and DEFA5) is significantly increased in large intestine tumors compared to normal tissue.