Changes in plasma 5-S-cysteinyldopa concentration in B16 melanoma-bearing mice treated with interferon-beta or...

We have previously shown that the urinary excretion of 5-S-cysteinyldopa (5-S-CD) reflects well the progression of B16 mouse melanoma. We examined the usefulness of plasma concentration of 5-S-CD in following the progression of melanoma and evaluating the efficacy of immuno- and chemotherapeutic agents in the B16 mouse model. Murine interferon-beta (MuINF-beta; 3 x 10(5) U) or dacarbazine (DTIC; 50 mg/kg) was administered once a day for 10 or 5 consecutive days starting 8 days after subcutaneous inoculation of B16 melanoma cells in C57BL/6 mice. Blood samples were collected from the tail vein and tumour volumes were measured every other day until day 24. Levels of 5-S-CD in plasma were determined by high-performance liquid chromatography. Tumours became palpable on day 6-8 and grew exponentially thereafter in the control mice. Tumours in INF-beta-treated mice also grew exponentially, although at a reduced rate. However, the growth of tumours in the DTIC-treated mice was almost suppressed between days 12 and 18. Mean values of tumour volume on day 16 were 1.45, 1.05, and 0.83 cm3 in the control, INF-beta-treated, and DTIC-treated groups, respectively. The plasma concentration of 5-S-CD began to increase on day 8, at much slower rates in the experimental groups than those in the control group. Mean values of plasma 5-S-CD on day 16 were 14.3, 5.9, and 5.6 nmol/l in the control, INF-beta-treated, and DTIC-treated groups; 5-S-CD level on day -2 was 1.8 nmol/l.(ABSTRACT TRUNCATED AT 250 WORDS)