Polyploidization of mesenchymal cells is associated with suppression of the non-coding RNA H19 and with reduced tumorigenicity

Mesenchymal stromal cells (MSCs) are used extensively in clinical trials; however, the potential for malignant transformation of MSCs has been raised. We examined the genomic stability versus the tumor forming capacity of multiple mouse MSCs. Murine MSCs have been shown to be less stable and more prone to malignant transformation than their human counterparts. A large series of independently isolated MSC populations exhibited low tumorigenic potential under syngeneic conditions, which increased in immune-compromised animals. Unexpectedly, higher ploidy correlated with reduced tumor forming capacity. Furthermore, in both cultured MSCs and primary hepatocytes, polyploidization was associated with a dramatic decrease in the expression of the long non-coding RNA H19. Direct knockdown of H19 expression in diploid cells resulted in acquisition of polyploid cell traits. Moreover, artificial tetraploidization of diploid cancer cells led to a reduction of H19 levels, as well as to an attenuation of the tumorigenic potential. Polyploidy might therefore serve as a protective mechanism aimed at reducing malignant transformation through the involvement of the H19 regulatory long non-coding RNA.

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Shoshani O, Massalha H, Shani N, Kagan S, Ravid O, Madar S, Trakhtenbrot L, Leshkowitz D, Rechavi G, Zipori D