Cuprous Oxide Nanoparticles (CONPs) Inhibit The Growth Of Melanoma Via Reducing Stemness Of Human Melanoma Stem Cells

Malignant melanoma is a very serious skin malignant tumor.The patient mortality rate is very high because it is very easy to transfer to the lung,brain and other important organs.With the development of social economy,malignant melanoma has become one of the fastest growing tumors in all the malignant tumors in China.Because the traditional therapy,such as surgical resection,radiotherapy and chemotherapy,is not effective in improving the prognosis and increasing long-term survival rate,the establishment of new drugs and therapies is particularly important.Nowdays,the development of nano-medicine and its branches,nano-oncology,provides the feasible methods and ideas for tumor therapy and anti-tumor drug development.Cancer stem cell theory holds that the formation and development of tumor is closely related to the population of stem cells known as cancer stem cells.This group of cells with a high degree of proliferation,self-renewal capacity and multi-differentiation potential can escape immune surveillance.They play an important role in the occurrence and development of tumor,and tumor invasion,metastasis,anti-drug resistant and recurrence,so killing cancer stem cell therapy is key to the treatment of tumors and prevent tumor recurrence.Traditional chemotherapeutic agents do not target cancer stem cells,that is why they can't completely eliminate cancer stem cells in patients.Therefore,we believe that it should be an important index to evaluate the effectiveness of drug therapy to effectively kill cancer stem cells and reduce the stemness of cancer stem cells.Our previous study validated the ability of Cuprous oxide nanoparticles?CONPs?in inhibiting growth and metastasis of mouse melanoma cells.The results showed that CONPs in vivo can significantly inhibit the growth of melanoma,significantly prolong the survival time of tumor bearing mice,improve the survival rate of tumor bearing mice,inhibit the metastasis of melanoma cells and reduce the number of pulmonary metastatic tumor and the size of single tumor with very low toxicity to mice.We also clarified anti-tumor mechanism of CONPs that CONPs started the mitochondria mediated apoptosis after entering the cells with the mitochondrial targeting.However,we did not evaluate the effectiveness of CONPs to kill human melanoma stem cell.Recently,the identification of melanoma stem cell markers made it possible to elucidate this problem.Our current research,as a part of research about evaluating and developing CONPs as potential clinic drugs to cure melanoma,we focus on testifying the ability of CONPs in low-dosage to inhibit the proliferation of human melanoma cell,kill melanoma stem cells and reduce the stemness of melanoma cells.Our current research revealed that low-dosage of CONPs could inhibit the proliferation of two kinds of human melanoma cell lines,A375 and Wm266-4 with high percentage of CD271^+/high cell in vitro.We tested the falling expression of cruail cell stem gene.Meanwhile,without inducing apoptosis directly,low-dosage CONPs could decrease the stemness,such as dramatic declining sphere-forming ratio,tumorigensis in NOD/SCID mice and the expression of stemness-relative genes,SOX10,CD271 in CD271^+/high cells,which is very essential in melanoma therapy.Finally,we also revealed that CD271^{+ /high} cells could intake much more CONPs than CD271^-/low cells,which might be one of the reasons on CONPs could decrease the stemness phenotype.As conclusion,low-dosage CONPs could inhibit the proliferation of melanoma via decreasing expression of stemness and proliferation-related gene,which gave more supportive evidences in developing CONPs to be a new-type drug to cure melanoma in clinic.