I've been reading the site and found it interesting that caffeine is strongly correlated with the success of DCA treatment. It may be relevant that hypoxia induces the release of adenosine, which has a variety of tumor-promoting effects, and caffeine is a well-known antagonist of the adenosine A2a receptor (A2aAR).
For example, adenosine promotes tumor progression by inducing the accumulation of HIF-1alpha, vascular endothelial growth factor (VEGF), and interleukin-8 (IL-
expression in hypoxic cancer cells, and caffeine blocks this effect. (http://www.ncbi.nlm.nih.gov/pubmed/17488804)
Also, adenosine prevents T cells from successfully attacking tumor cells, and caffeine can block this as well. (http://cancerres.aacrjournals.org/content/70/6/2245.short)
Hypoxia seems to be a concern with DCA therapy, and it's possible that caffeine's effectiveness is due to directly mitigating the effects of hypoxia.