SMAD2 and small cell lung carcinoma: Then, we perform the PPI network analysis in four distinct groups: SCLC vs. LCNEC (GSK3B, ITGB1, MAP1B, TCF3, VPSA13, and SMAD2), AC vs. TC (MMP3 and SNAI2), LCNEC vs. AC (MMP3, ITGAV, KRT14, PLEK2, and SNAI2), and SCLC vs. AC (PLEK2, MAP1B, MMP2, SNAI2, SPARC, WNT5A, and ITGA5).