CS and hepatocellular carcinoma: In contrast to the extreme drop in citrate and cis-aconitate levels, we found that expression of enzymes in both oxidative phosphorylation and the TCA cycle was uniformly elevated in HCC relative to normal thyroid tissues, including a significant up-regulation of citrate synthase (log2 fold change = 1.74, q = 2.00 × 10−4) (fig.