Circulating Melanoma Cells Persist in CR Patients After IL-2

PARIS—At the University of Heidelberg, Dr. Ulrich Keilholz and his colleagues are exploring the molecular determinants of prognosis in melanoma patients. A crucial question is whether patients with no evidence of disease after treatment are actually disease free.

Using a polymerase chain reaction (PCR) method for detecting circulating melanoma cells by means of tyrosinase amplification, the Heidelberg group has found that most patients who remain in long-term complete remission after cytokine treatment still have circulating tumor cells with the potential to form metastases again.

Mechanism of Tumor Dormancy

The mechanism of tumor dormancy during remission may be related to the induction of a specific T-cell-mediated immune response by interleukin-2 (Proleukin, IL-2), Dr. Keilholz suggested in a presentation at the Seventh International Congress on Anti-Cancer Treatment (ICACT). He and his co-workers have observed a skewing of the T-cell repertoire in patients who achieve remission after cytokine treatment.

Patients who respond successfully to treatment, he explained, tend to over-express a few T-cell families capable of mounting a strong response against the melanoma proteins gp 100, MART-1, and tyrosinase. What’s more, the gp 100 antigen is lost in melanoma biopsies from patients who respond to interferon-alfa and IL-2, but is maintained in individuals with progressive disease.