Abstract
Melanoma is malignant tumor that occurs in the skin and frequently metastasis via lymph node and blood into lung, brain, gastrointestinal tract and other organs that leads to high mortality rate. Melanoma is mainly treated by surgical resection combined with chemotherapy or radiation therapy for tumor in situ. If metastasis occurs, palliative chemotherapy is frequently used. Many immunotherapy protocols for melanoma are currently under trials. Melanoma is hard to be cured because of the high resistance to irradiation and chemo-drugs and high frequency of metastasis to risked organs. A protocol that can forecast the treatment response and state of metastasis will be valuable for developing strategy against melanoma. This study aimed to examine if MDSCs in blood could be an index to predict metastasis and the response to chemotherapy. Using B16-F0 as metastasis model, the variability of MDSCs in the blood during the progression of metastasis and following chemotherapy was examined by flow cytometry. Following i.v. injection of B16 tumor cells, the number of inflammatory monocytes has reached its highest level at day 8 and the neutrophils had reached its highest level at day 15, one day prior to detectable lung metastatic foci. The administration of ciplatin did not alter the pattern of neutrophils,but reduced the number of inflammatory monocytes. Although B16 tumor cells is sensitive to the cytotoxicity of cisplatin in vitro, the administration of cisplatin did not significantly improve the survival. Histology shows that mice receiving cisplatin treatment mainly died from liver metastasis, instead of lung metastasis in control mice. In summary, this study demonstrates that cisplatin treatment could alter the path of metastasis of melanoma and could be associated with the alternation of sub-population of MDSCs. The MDSCs in the blood is a potential index to predict the status of melanoma metastasis for designing new combination treatment protocol.