Human umbilical cord-derived mesenchymal stem cells (hUCMSCs) represent potential therapeutic tools for solid
tumors. However, there are numerous inconsistent results regarding the effects of hUCMSCs on
tumors, and the mechanisms underlying this remain poorly understood. The present study further examined this controversial issue by analyzing the molecular mechanisms of the inhibitory effects of hUCMSCs on the proliferation and migration of the human
lung cancer A549 cell line and the human
hepatocellular carcinoma (HCC) BEL7402 cell line in vitro. Flow cytometric analysis demonstrated that hUCMSCs arrested
tumor cells in specific phases of the cell cycle and induced the apoptosis of
tumor cells by using the hUCMSC-
conditioned medium (hUCMSC-CM). The hUCMSC-CM also attenuated the migratory abilities of the two
tumor cell types. Furthermore, the expression of
B-cell lymphoma 2 (Bcl-2), the pro-form of
caspase-7 (pro-caspase-7), β-
catenin and c-Myc was downregulated, while that of
ephrin receptor (EphA5), a
biomarker of
cancer cell dormancy, was slightly increased in these two tumor cell lines treated with hUCMSC-CM. Specifically, when co-cultured via direct cell-to-cell contact, hUCMSCs were able to spontaneously fuse with any of the two types of solid
tumor cells. These observations suggested that hUCMSCs may be a promising candidate for the
biological therapy of
lung cancer and HCC. Future studies should focus on detailed evidence for cell fusion, as well as other mechanisms proposed in the present study, by introducing additional experimental approaches and models.