Coley's Lessons Remembered: Augmenting Mistletoe Therapy.

The following four observations point in the same direction, namely that there is an unleveraged potential for stimulating the innate immune system against cancer: (1) experimental treatments with bacterial extracts more than 100 years ago by Coley and contemporaries, (2) a positive correlation between spontaneous regressions and febrile infection, (3) epidemiological data suggesting an inverse correlation between a history of infection and the likelihood of developing cancer, and (4) our recent finding that a cocktail of pattern recognition receptor ligands (PRRLs) can eradicate solid tumors in cancer mice if applied metronomically. Because the main immunostimulating component of mistletoe extract (ME), mistletoe lectin, has been shown to be a PRRL as well, we suggest to apply ME in combination with additional PRRLs. Additional PRRLs can be found in approved drugs already on the market. Therefore, augmentation of ME might be feasible, with the aim of reattaining the old successes using approved drugs rather than bacterial extracts.