[In vitro and in vivo effect of thyroid hormones on the growth of neuroblastoma cells. II. The effect of thyroxine in vivo].

We studied the effect of thyroxine (T4 0.050 mg/kg/d, i.p.), TSH (0.08 U/kg/d, i.p.) and hypothalamic peptide (HF; 1 mg protein/kg/d, i.p.) given alone or in combination, on the growth of murine (NB C-1300) and human (NB Park) neuroblastoma transplanted onto the nude mouse (nu/nu). Both T4 and TSH caused a significant increase (perchlorate a decrease) of the serum T3. Histologically, the T4 treatment was followed by partial tumor necrosis and a marked growth of connective tissue within the tumors; there was no significant change in tumor weight as compared to the control group. Treatment with HF alone or in combination with T4 inhibited in 30% the invasive growth of the neuroblastoma transplants and a fatty degeneration was found in 25% of the human NB-TX after 28 days of treatment. The measurement of the intratumoral content of the cyclic nucleotides showed a significant increase of the cAMP and a decrease of the cGMP. The morphological and biochemical alteration observed under treatment with thyroid hormone or analogues could possibly be applied for therapeutic purposes.