PDP1 and neoplasm: Furthermore, an ELISA assay showed a marked reduction of PDH activity in U2932 tumors after treatment (48% at 30 min and 58% at 4 h, Figure 5D), which was accompanied by an increase in the expression of phospho-PDH in this tumor model (p ≤ 0.005, Figure 5E), but not in MDA-MB-231 tumors (Figure 5D,E).