Amniotic membrane-derived cells inhibit proliferation of cancer cell lines by inducing cell cycle arrest

Abstract

Cells derived from the amniotic foetal membrane of human term placenta have drawn particular attention mainly for their plasticity and immunological properties, which render them interesting for stem-cell research and cell-based therapeutic applications. In particular, we have previously demonstrated that amniotic mesenchymal tissue cells (AMTC) inhibit lymphocyte proliferation in vitro and suppress the generation and maturation of monocyte-derived dendritic cells. Here, we show that AMTC also significantly reduce the proliferation of cancer cell lines of haematopoietic and non-haematopoietic origin, in both cell-cell contact and transwell co-cultures, therefore suggesting the involvement of yet-unknown inhibitory soluble factor(s) in this 'cell growth restraint'. Importantly, we provide evidence that the anti-proliferative effect of AMTC is associated with induction of cell cycle arrest in G0/G1 phase. Gene expression analyses demonstrate that AMTC can down-regulate cancer cells' mRNA expression of genes associated with cell cycle progression, such as cyclins (cyclin D2, cyclin E1, cyclin H) and cyclin-dependent kinase (CDK4, CDK6 and CDK2), whilst they up-regulate cell cycle negative regulator such as p15 and p21, consistent with a block in G0/G1 phase with no progression to S phase. Taken together, these findings warrant further studies to investigate the applicability of these cells for controlling cancer cell proliferation in vivo.

© 2012 The Authors Journal of Cellular and Molecular Medicine © 2012 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd.

Figures

Fig 1

AMTC reduce the proliferation of cancer cells of both haematopoietic and non-haematopoietic origin. Haematopoietic and non-haematopoietic cancer cell lines were cultured alone (control), or with AMTC either in direct contact (upper panel) or with physical separation (transwell setting, lower panel). Different cancer cell: AMTC ratios were used. After 3 days of culture, cancer cell proliferation was assessed by [3H]-thymidine incorporation and reported as a percentage of cell proliferation in comparison with control cancer cell proliferation. Data are expressed as mean ± S.D. of at least four independent experiments. *P < 0.05, **P < 0.01, ***P < 0.001 versus corresponding control sample.

Fig 2

Alteration in cancer cell proliferation by AMTC and other cell lines. Jurkat and U937 cells were cultured alone or in the presence of different γ-irradiated cell types (AMTC or BM-MSC, dermal fibroblast cells, KG1a, U937 and Jurkat). Co-cultures were performed in both contact and transwell settings, at cancer cell: different cell types ratios of 1:2. After 1, 2 and 3 days of culture, Jurkat and U937 cell proliferation was assessed by [3H]-thymidine incorporation. Data are expressed as mean of more than four independent experiments. *P < 0.05, **P < 0.01, ***P < 0.001 versus corresponding control sample.

Fig 3

AMTC arrest the cell cycle of cancer cells. Jurkat (upper panel) and U937 (lower panel) cells were cultured alone or in the presence of AMTC, in either contact or transwell settings, at a cancer cell: AMTC ratio of 1:2. At 16, 24 and 48 hrs, cultures were pulsed with BrdU for 1h, and cancer cells were then collected and stained with anti-BrdU APC and 7-AAD. The percentage of cells in the G0/G1, S or G2/M phase of the cell cycle is indicated. The FACS profiles shown are representative of three independent experiments.