Human mesenchymal stem cells (hMSCs) are multipotent non-hematopoietic precursor cells with the ability to differentiate into several tissue types. The use of hMSCs has gained significant importance in cancer therapies as well as a large number of degenerative disease therapies due to their homing abilities. However, these cells may undergo spontaneous transformation leading to them bypassing naturally built-in cell controls that could lead to senescence and carcinogenesis. Therefore, although MSCs have great potential for cancer therapy, they also risk the development of cancer, which provides them with double-faced characteristics for both cancer development and therapy. The potential use of hMSCs in therapeutics from the aspect of in vitro expansion of hMSCs and telomere dynamic is discussed.