Table 1: Important miRNAs significantly dysregulated by cigarette smoke and implicated in carcinogenesis [8, 14, 32, 36].

miRNATargetsBiological effects of dysregulationComments on dysregulation

Downregulated

let-7a, b, c, fRas, CDK6, cyclin A2Ras oncogene activation, cell proliferation, angiogenesisNormally, let-7 is a master regulator of cell proliferation
mir-26aTGFTGF overexpression, angiogenesisGreater downregulation in postweanling female mice
mir-30aEFG pathway, NF-κB inhibitors, CDC40 Cell cycle progression, cell adhesion, protein repair, EFG activation, stress response (NF-κB activation)Downregulated in both humans and rats
mir-30cEFG pathway, NF-κB inhibitors, CDC41 Chemoresistance, cell cycle progression, cell adhesion, protein repair, EFG activation, stress response (NF-κB activation)Downregulation leads to chemoresistance mediated through MDR-1
mir-34 a–cCDK4, CDK6, cyclin E2, and E2F3Cell cycle arrest inhibitedMutations in p53 can lead to its downregulation
mir-122aheme-oxygenase 1Increased antioxidant activity in liver and lungsInvolved in stress response
mir-125aERBB7 (gene for EGFR)ERBB7 oncogene activationMaps to fragile site with G/U polymorphism
mir-140p53 pathwayCell cycle arrest inhibitedGreater downregulated in postweanling female mice
mir-345Ras pathwayRas oncogene activation, cell proliferationDownregulation is persistent for at least one week after cessation

Upregulated

mir-294Zinc finger protein 697, AT-rich interactive domain 4AIncrease in transcriptionUpregulated 10.4-fold in Izzotti et al. [8].