Global gene profiling and anti-tumour activity of human mesenchymal stem cells on BV173 B leukaemia cell line

In 2013, there were 8.2 million cancer deaths worldwide and cancers were the second leading cause of death after cardiovascular diseases. Thus, it represents one of the major health issues all over the world. Current therapies such as the conventional methods of targeting the tumour cells by non-specific chemotherapy and radiotherapy have not yielded satisfactory outcomes as seen in many cancer remission cases, and an efficient treatment for cancer cells has yet to be identified. The recent development in mesenchymal stem cell research promises an efficient anti-cancer therapy via a possible mode of cell cycle arrest, apoptosis and immunosuppressive activity. Umbilical cord mesenchymal stem cells (UC-MSCs) are considered as post- natal stem cells present in the Wharton’s jelly of the umbilical cord tissue and are considered as an appealing source of adult stem cells for the cell therapy and tissue engineering as they are easily obtained and expanded while maintaining their multi-lineage differentiation potential. The past research studies have shown that UC-MSCs profoundly inhibited the growth of various tumour cells, however, the molecular mechanisms that execute this inhibition have yet to be identified. Although MSCs contribute to the haematopoiesis and support the growth of blood cells but also able to inhibit highly proliferating cells. Therefore, this study aims to investigate the inhibitory effect of UC-MSCs on haematopoietic tumour cells proliferation at in vitro by elucidating the molecular mechanisms and the relevant gene expression profiles. Wharton’s jelly from human umbilical cord was subjected to the collagenase digestion and the single cells were cultured to generate UC-MSCs. The adherent cells were characterized based on a universally accepted immunophenotyping and mesodermal differentiation. Haematopoietic origin tumour cell lines HL-60, K562, Jurkat and BV173 cell lines were purchased from ATCC and maintained in 10% foetal bovine serum supplemented RPMI media. Umbilical cord MSCs and tumour cells were co-cultured and the effect of UC-MSCs on tumour cell proliferation, apoptosis, cell cycle arrest, gene expression, biological process and signalling pathways were evaluated. Finally, the six selected genes were validated using SYBER GREEN qPCR. The results demonstrated that in the presence of UC-MSCs, tumour cell proliferation were profoundly inhibited in dose dependent manner as measured by 3H-thymidine uptake and MTS Assay. Transwell assays indicated that UC-MSCs mediated inhibition was mainly attributed to the cell- to-cell contact mode. Umbilical cord MSCs did not induce apoptosis as their mode of anti-proliferative activity. Further investigation on the tumour cell cycle revealed that UC-MSCs induced an arrest in Go/G1 and S phase of cell cycle. A subsequent microarray analysis showed that out of 3019 differentially expressed genes, 2000 and 1019 genes were up and down- regulated respectively in BV173 tumour cell line that were co-cultured with UC-MSCs. Besides, the microarray results also highlighted 380 altered genes with unknown function or unrelated association in BV173 cell line. When these dysregulated genes were analysed based on biological processes, the physiological functions such as cell adhesion, vasculature development, regulation of cell proliferation and regulation of cell migration processes were over-represented. In addition, the microarray analysis showed the most significant signalling pathways such as focal adhesion, ECM-receptor interaction, cytokine-cytokine receptor interaction, MAPK, p53 and TGF-§ signalling pathway were dysregulated by UC-MSCs in BV173. The qPCR result confirmed the mRNA level some of the selected genes. The present study indicated that UC-MSCs inhibit tumour cells proliferation by arresting in Go/G1 phase of cell cycle and this effect is mediated by cell-to- cell contact. Further gene profiling and signalling pathways revealed that anti- proliferative activity of UC-MSCs on tumour cell proliferation is associated with genes which are involved in cell cycle (CDK6, CCNE2 and CDKN1A), cell adhesion (TGF§I, MYO7A and CD82), metastasis (CCL2, TFPI2 and CXCR3), angiogenesis (PDGF, CXCL1 and PTX3) and regulation of cell proliferation (HECW1, SCIMP and ANXA1). The generalized tumour cells inhibition by UC-MSCs could be potentially exploited to treat various tumours. However, this anti-proliferative activity needs to be tested in in-vivo model and at protein level for their better understandings and validation.

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