Peripheral blood CD8highCD57+ lymphocyte levels may predict outcome in melanoma patients treated with adjuvant interferon-alpha.

BACKGROUND: The objective of this study was to evaluate the significance of CD8highCD57+ lymphocytes for the survival of high risk melanoma patients treated with adjuvant interferon-alpha (IFN-alpha). PATIENTS AND METHODS: The prognostic significance of peripheral blood CD8highCD57+ lymphocyte levels for survival was analysed retrospectively in 16 IFN-alpha-treated melanoma patients with resected regional lymph node metastases. The survival of the patients was analyzed using the Kaplan-Meier method. The difference between survival curves was determined using the log-rank test. RESULTS: The median survival time of patients with >23% CD8highCD57+ lymphocytes prior to treatment with IFN-alpha was 14.2 months, whereas the median survival time of patients with < 23% CD8highCD57+ lymphocytes was not reached at the time of analysis (median follow-up 24.6 months). CONCLUSION: Larger prospective studies are justified to investigate the precise value of CD8highCD57+ lymphocytes in the selection of melanoma patients for adjuvant treatment with IFN-alpha.

In vitro and in vivo protein delivery from in situ forming poly(ethylene glycol)-poly(lactide) hydrogels.

Previous studies have shown that stereocomplexed hydrogels are rapidly formed in situ by mixing aqueous solutions of eight-arm poly(ethylene glycol)-poly(L-lactide) and poly(ethylene glycol)-poly(D-lactide) star block copolymers (denoted as PEG-(PLLA)(8) and PEG-(PDLA)(8), respectively). In this study, in vitro and in vivo protein release from stereocomplexed hydrogels was investigated. These hydrogels were fully degradable under physiological conditions. Proteins could be easily loaded into the stereocomplexed hydrogels by mixing protein containing aqueous solutions of PEG-(PLLA)(8) and PEG-(PDLA)(8) copolymers. The release of the relatively small protein lysozyme (d(h)=4.1 nm) followed first order kinetics and approximately 90% was released in 10 days. Bacteria lysis experiments showed that the released lysozyme had retained its activity. The relatively large protein IgG (d(h)=10.7 nm) could be released from stereocomplexed hydrogels with nearly zero order kinetics, wherein up to 50% was released in 16 days. The in vitro release of the therapeutic protein rhIL-2 from stereocomplexed hydrogels also showed nearly zero order kinetics, wherein up to 45% was released in 7 days. The therapeutic efficacy of stereocomplexed hydrogels loaded with 1x10(6) IU of rhIL-2 was studied using SL2-lymphoma bearing DBA/2 mice. The PEG-(PLLA)(8)/PEG-(PDLA)(8)/rhIL-2 mixture could be easily injected intratumorally. The released rhIL-2 was therapeutically effective as the tumor size was reduced and the cure rate was 30%, whereas no therapeutic effect was achieved when no rhIL-2 was given. However, the cure rate of rhIL-2 loaded stereocomplexed hydrogels was lower, though not statistically significant, compared to that of a single injection with 1x10(6) IU of free rhIL-2 at the start of the therapy (cure rate=70%). The therapeutic effect of rhIL-2 loaded stereocomplexed hydrogels was retarded for approximately 1-2 weeks compared to free rhIL-2, most likely due to a slow, constant release of rhIL-2 from the hydrogels.

Treatment with IL-2 and IL-12 inhibits tumour cell division in SL2 lymphoma.

We examined which mechanism plays a dominant role in the rejection of solid SL2 lymphoma treated with locally applied IL-2 and/or IL-12. This treatment resulted in about 80% cures. There was a moderate influx of leukocytes in the tissue surrounding tumours; yet these cells failed to invade the solid tumours. Potentially cytotoxic cells were not observed in close proximity to areas of tumour cell death, indicating that cell-mediated cytotoxicity is not an important mechanism of tumour rejection in this model. Similarly, inhibition of blood vessel growth and/or blood vessel injury could be ruled out as mechanisms, since tumour rejection was not accompanied by decreased angiogenesis or blood vessel injury. We did observe that many tumour cells die via apoptosis or necrosis and that tumour cell division in cytokine-treated mice is inhibited. In conclusion, IL-2/IL-12-mediated tumour rejection in solid SL2 lymphoma is mainly due to a shifted balance between tumour cell death and tumour growth caused by inhibition of proliferation, rather than to direct cell cytotoxicity or destruction of blood vessels.

Presence of cytotoxic B220+CD3+CD4-CD8- cells correlates with the therapeutic efficacy of lymphoma treatment with IL-2 and/or IL-12.

Cancer treatment with IL-2 and IL-12 is thought to work via enhancement of proliferation and activity of T cells and NK cells. Incubation of cytotoxic T lymphocytes (CTLs) and NK cells with IL-2 and/or IL-12 results in propagation of a distinct cell type called lymphokine-activated killers (LAK) characterized by increased lytic activity against many tumor types. Here we address the question whether cytokine therapy may be efficient in treatment of a LAK-insensitive tumor and, if so, which cell type, other than classic LAK cells, is responsible for tumor cell killing. We used DBA/2 mice bearing metastasized SL2 lymphoma and treated them with locally applied IL-2 and /or IL-12 injections. We showed that IL-12 treatment is efficient, though there is a rather narrow range of effective doses because of toxicity. This toxicity may be alleviated by a single injection of IL-12 before treatment. Next, we showed that IL-12 synergistically enhances the efficacy of local IL-2 treatment. Moreover, our results indicate that the IL-2/IL-12-mediated therapeutic effect is greatest when it is given after establishment of an immune response to a tumor. Finally, we showed the existence of a unique population of lymphoid cells, namely B220+CD3+CD4-CD8-, at the site of tumor growth. These cells become highly cytotoxic to SL2 cells in mice treated with cytokines late (day 10-14) in the course of the immune response, but not in mice treated early (day 3-7), and cytotoxicity of this unique cell population correlates with the success of therapy.