Fusion between tumor cells enhances melanoma metastatic potential

Malignant melanoma, characterized by early distant metastasis to the lungs and brain, is a leading cause of mortality related to skin cancer. Cell fusion and the subsequent aneuploidy, commonly observed in melanoma, are associated with poor prognosis. However, the pathological consequences of cell fusion in melanoma remain unknown. Therefore, the present study aims to investigate the pathological consequences of cell fusion in melanoma and the mechanism of melanoma metastasis. Phytohemagglutinin-polyethylene glycol (PHA-PEG) fusion method was developed for the fusion of tumor cells. Melanoma cells were fused through the improved PHA-PEG fusion method and obtained by fluorescence-activated cell sorting. DNA content was analyzed through flow cytometry. Cell proliferation rate was detected by cell culture in vitro, and the cell number was counted daily. To detect the tumor growth rate in vivo, cells were injected subcutaneously and the tumor volumes were measured using a vernier caliper. To analyze the tumor metastatic potential, cells were injected intravenously, and the collected lung-metastasis samples were weighed by an electronic balance and the surface nodules were counted. We established an improved phytohemagglutinin-polyethylene glycol fusion method and successfully obtained stable melanoma tumor-tumor cell fusion hybrids. Cell size, DNA content, and chromosome numbers of the fusion hybrids were approximately twice those of the parents. The metastatic potential of the fusion hybrids was dramatically enhanced, in contrast to their proliferation rate. Their metastasis was specific to the lungs. We developed a highly efficient cell fusion method that can be applied in many fields, particularly cancer research. Our study has proven that tumor-tumor cell fusion hybrids in melanoma can acquire enhanced and specific metastatic potential. Thus, blockage of cell fusion may be a new strategy for melanoma metastasis therapy.