GAPDH and lung carcinoma: NEDD9 knockdown significantly impaired glycolysis in multiple lung cancer cell lines This was accompanied by post-transcriptional downregulation of steady-state levels of hexokinases (HK1 and HK2), which catalyze early steps in the glycolytic cascade, key rate limiting enzyme phosphofructokinase (PFK1), and downstream glyceraldehyde phosphate dehydrogenase (GAPDH).