Interleukin-2 and interleukin-4 display potent antitumour activity on rat medullary thyroid carcinoma cells.

Currently, surgical resection is the only treatment used for human medullary thyroid carcinoma (MTC). However, as metastases are commonly observed, we investigated the potential of adjuvant therapy with interleukin-2 (IL-2) and interleukin-4 (IL-4) in a rat model. The interleukins were delivered by means of xenogeneic tumour cells engineered to secrete IL-2 and IL-4. We found that when a mixture of MTC cells and IL-2 or IL-4 secreting cells were implanted in rats, the growth of the resulting tumours was inhibited as a function of the number of interleukin-secreting cells in the inoculum. Moreover, association of the two interleukins exerted a synergistic antitumour effect. These experimental results, showing thyroid C cell tumour rejection, are of major interest, as they show the potential therapeutic application for these two interleukins, which could be used, in particular, as postsurgical adjuvants.