Malignant Transformation Potentials of Human Umbilical Cord Mesenchymal Stem Cells Both Spontaneously and via 3-Methycholanthrene Induction

Qiuling Tang,Xiulan Lai,Zhiwei Cai,Yezeng Chen,Shan Qin,Sizheng Liu,Zexin Zheng,Qingdong Xie,Qiurong Chen,Lian Ma,Martin Maldonado,Guyu Ho,Gabriele Saretzki

doi:10.1371/journal.pone.0081844

Abstract

Human umbilical cord mesenchymal stem cells (HUMSCs) are highly proliferative and can be induced to differentiate into advanced derivatives of all three germ layers. Thus, HUMSCs are considered to be a promising source for cell-targeted therapies and tissue engineering. However there are reports on spontaneous transformation of mesenchymal stem cells (MSCs) derived from human bone marrows. The capacity for HUMSCs to undergo malignant transform spontaneously or via induction by chemical carcinogens is presently unknown. Therefore, we isolated HUMSCs from 10 donors and assessed their transformation potential either spontaneously or by treating them with 3-methycholanthrene (3-MCA), a DNA-damaging carcinogen. The malignant transformation of HUMSCs in vitro was evaluated by morphological changes, proliferation rates, ability to enter cell senescence, the telomerase activity, chromosomal abnormality, and the ability to form tumors in vivo. Our studies showed that HUMSCs from all 10 donors ultimately entered senescence and did not undergo spontaneous malignant transformation. However, HUMSCs from two of the 10 donors treated with 3-MCA displayed an increased proliferation rate, failed to enter senescence, and exhibited an altered cell morphology. When these cells (tHUMSCs) were injected into immunodeficient mice, they gave rise to sarcoma-like or poorly differentiated tumors. Moreover, in contrast to HUMSCs, tHUMSCs showed a positive expression of human telomerase reverse transcriptase (hTERT) and did not exhibit a shortening of the relative telomere length during the long-term culture in vitro. Our studies demonstrate that HUMSCs are not susceptible to spontaneous malignant transformation. However, the malignant transformation could be induced by chemical carcinogen 3-MCA.

Highlights

Human umbilical cord mesenchymal stem cells (HUMSCs) possess multipotent characteristics, have a relatively high proliferation rate, and can be induced to differentiate into advanced derivatives of all three germ layers, including osteoblasts, adipocytes, chondrocytes, myoblasts, islet cells, and neurons [1,2,3,4,5,6,7]
Using the criteria of positive b-gal activity, increased cell population doubling time (PDT), lack of apparent morphological changes, and eventual cell death, we concluded that HUMSCs did not undergo spontaneous transformation
HUMSCs are primitive stromal cells that have been shown to differentiate into cell types of all three germ layers [32]

Summary

Introduction

HUMSCs possess multipotent characteristics, have a relatively high proliferation rate, and can be induced to differentiate into advanced derivatives of all three germ layers, including osteoblasts, adipocytes, chondrocytes, myoblasts, islet cells, and neurons [1,2,3,4,5,6,7]. Roland et al reported that spontaneous malignant transformation of bone marrow-derived hMSCs occurs in 45.8% (11 of 24) of cultures and concluded that spontaneous malignant transformation may represent a biohazard in long-term ex vivo expansion of hMSCs [17]. Similar phenomena of bone marrow-derived MSCs from both human and murine origins have been reported in other studies [18,19,20]. There is no knowledge far as to whether HUMSCs could undergo malignant transformation during long-term in vitro culture or could be induced to transform by carcinogens. We set out to investigate the risk of spontaneous malignant transformation of HUMSCs as well as the ability of 3-MCA, a DNA-damaging carcinogen [21,22], to induce the HUMSC transformation

Methods

Results

Conclusion