Association of tyrosine hydroxylase expression in brain and tumor with increased tumor growth in sympathectomized mice

Objective: Lymphocytes express tyrosine hydroxylase (TH), the rate-limiting enzyme for the synthesis of dopamine, norepinephrine and epinephrine. This suggests a broader role for cathecholamines in lymphocyte function, as well as the potential secretion of catecholamines by tumors of lymphoid origin. Our aim was to evaluate the expression of Th by murine lymphoma cells in an in vivo mouse model. For this, L5178Y-R lymphoma cells were implanted in nerve-intact and sympathectomized male BALB/c mice. Relative Th gene expression in tumor and brain was determined by quantitative PCR. Body composition, tumor volume, and plasma TH1/TH2/TH17 cytokines were also evaluated as markers of tumor-host condition and anti-tumor immune response in absence of adrenergic innervation.

Results: We found a significant (p = 0.045) 3.3-fold decrease of Th gene expression in tumor and a non-significant (p = 0.60) 6.9-fold increase in brain after sympathectomy. Sympathectomized mice also showed a significant increase in tumor mass at days 18 (p = 0.032) and 28 (p = 0.022) and increased interscapular fat (p = 0.04). TH1/TH2 and TH17 cytokines levels in plasma from sympathectomized tumor-bearing mice were not different from control mice.

Conclusion: The L5178Y-R lymphoma does not express Th during in vivo progression.