MAP4 and small cell lung carcinoma: Furthermore, several proteins related to splicing (splicing factors, and heterogeneous nuclear ribonucleoproteins) were significantly overexpressed only in SCLC tissue, while proteins related to microtubule organization (e.g., TBB4B, TBB5, MAP4, and MAP1S) were also found to be highly overexpressed only in SCLC tissue.