The training data used in official submissions includes all examples of previous BioCreative PPI article tasks. However, the BioCreative III development set was selectively added for training in different runs. Unigrams (UNI), bigrams (BI), and trigrams (TRI) were used as multi-word features. MeSH feature is unigrams and bigrams from MeSH terms. For grammar relations (GRs), stemming was performed on Run 3 through Run 5. Feature cut was performed based on the frequency threshold four.