ALDH3A1 and lung carcinoma: A second set of upregulated genes includes three genes that function in ATII cells and have also been associated with lung cancers: ALDH3A1, VDR and CHKA. Aldehyde dehydrogenases function in the lung to break down aldehydes which may occur naturally in the environment as a breakdown product of xenobiotics or as part of endogenous metabolism.