Moreover, caffeine downregulates the expression of several proteins, including retinoblastoma protein (Rb), extracellular signal-regulated kinases (ERK) 1/2, GSK3β, pyruvate dehydrogenase kinase 1 (PDK1), cyclin D1, cyclin E, c-Myc, Akt, and mTOR in various cancer cell lines [61,62,63]. This evidence concerns the gene PDK1 and cancer.