MMP9 and neoplasm: LDHC is a candidate oncogene in the carcinogenesis of smoking-related LUAD.LDH-C4 was positive in 81.8% of LUAD samples (72/88), whereas no LDH-C4 was found in any adjacent tissues; LDHC induced the EMT and the expression of MMP-2 and MMP-9, so as to achieve xenograft tumor growth and metastatic potential by the activation of the PI3K/Akt pathway both in vitro and in vivo. LDHC is a prognostic biomarker in LUAD