Efficacy evaluation of α-MSH-IFN-α2b and IFN-α2b in malignant melanoma by 99mTc-SPECT/CT

1228 Objectives: Interferons-alpha2a (IFN-α2a) has shown to have potential therapeutic effect on malignant melanoma. However, the severe toxic side effects limit its application. Evidences showed malignant melanoma is accompanied by high expression of MC-1R (melanocortin receptor 1). α-MSH (α-melanocyte-stimulating hormone) peptide (SYSMEHFRWGKPV) is specific bind to MC-1R which over expressed on malignant melanoma cells. In this study, 99mTc-EC-α-MSH-IFN-α2b and 99mTc-EC-IFN-α2b were used as radiolabeling probes in malignant melanoma rats’ models. biochemical data, immunohistochemistry examinations and image analysis were used to evaluate if theα-MSH-IFN-α2b have the better potential treatment effect and less toxic side effect then IFN-α2b on malignant melanoma. M&M: Plasmid pET-22b(+)IFN-α2a-NGR was digested with BamH I and Sal I restriction enzymes,and then inserted α-MSH peptide sequences to construct prokaryotic expression vector pET-22b(+)IFN-α2a-α-MSH. The plasmid was transfected into Rosetta-gamiTM2(DE3) cell. IPTG was used to induce fusion protein IFN-α2a-α-MSH expression. The expression of IFN-α2a-α-MSH was detected by SDS-PAGE and Western blot. IFN-α2a-α-MSH protein was purified by hydrophobic interaction chromatography (HIC). The stability and radiochemical purity of 99mTc-EC-α-MSH-IFN-α2b and 99mTc-EC-IFN-α2b radiation molecular probe was verified by TLC and UPLC methods. At the same time, Interferon probes’ activity were verified by biochemical methods. A total of 40 C57BL male malignant melanoma rats (8 weeks) were randomly divided into the four groups (Group A&B: without treatment group, N=10 for each. Group C: IFN-α2b treatment group, N=10. Group D: α-MSH-IFN-α2b treatment group, N=10.). Static and dynamic 99mTc-EC-α-MSH-IFN-α2b and 99mTc-EC-IFN-α2b Whole-body SPECT/CT data were collected from Group A&B since the 8th day the tumor planted. After 15th day tumor planted, the biochemical indexes, immunohistochemistry examinations data collect from all the groups. Results: The radiolabeling results for 99mTc-EC-α-MSH-IFN-α2b and 99mTc-EC-IFN-α2b were verified be greater than 96.132% and 97.612%. The 4 hrs. decomposition ratio <5% Significant differences were found between 99mTc-EC-α-MSH-IFN-α2b (Group A) and 99mTc-EC-IFN-α2b (Group B) SPECT images. In comparison to the normal IFN-α2b group, SPECT scanning showed 99mTc-EC-α-MSH-IFN-α2b has better accumulation and faster metabolic rate in malignant melanoma rats. On the other hand, biochemical results, immunohistochemistry examinations data shown the Group D had significant better treatment effect(P<0.01) and less toxic side effect than Group C(P<0.05). Conclusions: Compare to the IFN-α2b, α-MSH-IFN-α2b may have the better potential treatment effect on malignant melanoma. On the other hand, 99mTc-EC-α-MSH-IFN-α2b SPECT scan may have the potential specific diagnostic value for malignant melanoma.