TP53 and lung cancer: Exposure to CaTiO3NPs caused significant increases in apoptotic cell death only in human lung cancer A-549 cells as manifested by the concurrent marked upregulation in the expression level of apoptotic p53 and Bax genes and a significant decrease in the anti-apoptotic Bcl2 expression level noticed after 48 h of lung cancer A-549 cells treatment with CaTiO3NPs.