Zhao Q, Gregory CA, Lee RH, Reger RL, Qin L, Hai B, Park MS, Yoon N, Clough B, McNeill E,  Prockop DJ, Liu F. MSCs derived from iPSCs with a modified protocol are tumor-tropic but have much less potential to promote tumors than bone marrow MSCs. Proc Natl Acad Sci 2015; 112:530-535.

Prepared by: Avery Wilson, Advance Stem Cell Course, Fall 2015

LAYMAN ABSTRACT

Mesenchymal stem or stromal cells (MSCs) are multipotent cells that are capable of differentiating into a variety of cell types. MSCs can form connective tissues throughout the body and are capable of forming osteoblasts, fibroblasts, chondrocytes and adipocytes. MSCs have potential therapeutic applications in treating cancer and tissue regeneration due to cancer and radiation treatments. MSCs can serve as a vehicle for gene therapy for advance cancers, including treatment in bone, based on osteogenic properties. A contraindication for the use of bone marrow derived MSCs (BM-MSC) is based on the cells’s ability to promote tumor. This study asked if MSCs from transgene-free human induced pluripotent stem cells (iPSCs) can be a better alternative to BM-MSCs.

To derive MSCs efficiently from human iPSCs, the authors used media supplemented with the SMAD-2/3 inhibitor (SB-431542), which was believed to promote the differentiation of iPS into MSCs. The studies asked of the beneficial factors from iPSC-MSCs were comparable to BM-MSCs. These authors also examined pro-tumors factors expressed in BM-MSCs and compared to iPSC-MSCs. The results demonstrated an efficient and safe protocol to derive MSCs from iPSCs with reduced support for tumor growth, invasion, and pro-tumor effects than BM-MSCs. These features make iPSC-MSCs promising for future cancer treatments.

This study demonstrated the contraindications derived MSC use are diminished with iPSC-MSCs compared to BM-MSCs. However, ambiguous determination of MSCs derivation and differentiation, presumed expandability of CSC, and lack of more in depth data analysis present a number of limitations of this paper. With further research, MSC use in cancer treatments can be further examined with safer options and diminished tumor promoting potential.

SCIENTIFIC ABSTRACT

Mesenchymal stem or stromal cells (MSCs) offer great promise as potential therapies for cancers and other diseases. MSCs contain unique tumor-homing capacity that allows them to serve as a means of transport for gene therapy of advanced cancers. Contraindications to MSCs for cancer therapies include tumor growth, metastasis, and pro-tumor effects. This study proposes using chemically defined mTeSR1 medium supplemented with the SMAD-2/3 inhibitor (SB-431542) and an atmosphere of 7.5% CO₂ to culture colonies of MSCs from transgene-free human induced pluripotent stem cells (iPSCs). iPSC-MSCs are hypothesized to retain BM-MSCs desired beneficial factors with reduced pro-tumor potential.

The iPSC derived MSCs observed at 25 days and 45 days displayed morphological change to spindle shaped similar to mesenchyme and fibroblast. To determine the loss of pluripotency and transition to multipotent MSC, the expression of Nanog and Oct4 genes were observed and revealed decrease expression with iPSC-MSCs. Positive MSC markers CD44, CD73, CD90, CD 105, and CD166 showed high expression with iPSC-MSCs. Negative MSC markers CD11b, CD24, CD34, CD45, and HLA-DR presented marginal expression, similar to BM-MSCs.

To examine iPSC-MSCs homing abilities, home related genes, CXCR4, CXCR6, CD44, VEGFR1 and integrins ITGA6 and ITGB1, were studied and displayed comparable levels to BM-MSCs. An anomaly observed was with VEGFR1, which demonstrated a 65-fold increase expression in iPSC-MSCs compared to BM-MSCs. BM-MSCs or iPSC-MSCs transduced with CMV-copGFP lentiviruses were injected via tail vein in SCID mice, and tumors were harvested 16 h later for section and qRT-PCR assay used to quantify homing of MSCs to cancer cells. Results showed that iPSC-MSCs are capable of homing to cancer at comparable levels to BM-MSCs.

Interaction between cancer cells and MSCs promote metastasis and enhance epithelial mesenchymal transition (EMT). To examine factors responsible for metastasis, LoVo cancer cells were cocultured with either BM or iPSC MSCs. iPSC-MSCs expressed reduced expression of mesenchymal markers fibronectin1 (FN1), metalloproteinase 2 (MMP2), N-cadherin (NCAD), vimentin (VIM), and also the pro-EMT factors ZEB1, ZEB2, and TWIST1. For tumor initiating and growth assay, HCC1806 cancer cells were coinjected with BM-MSCs or iPSC-MSCs into the fourth mammary fat pad of NOD/SCID mice, and tumors were harvested 6 weeks after inoculation. The tumor weight of BM-MSCs with HCC1806 were larger than iPSC-MSCs. Data illustrations that iPSC-MSCs are less likely to support the growth and invasion of cancers than BM-MSCs.

Overall, this study attempts to illustrate that iPSC derived MSCs are a safer option than BM derived MSCs by possessing less potential to promote tumors. This study has a number of limitations that allows us to question whether this hypothesis is true. The morphology of the iPSC doesn’t entirely resemble that of expected MSC morphology. When studying homing properties, iPSC-MSCs had drastically elevated expression of VEGFR1. VEGF stimulates angiogenesis which is needed by tumors to promote growth and metastasis. With such elevated levels of expression, tumor growth and metastasis elevation would be expected also. With this study, a protein analysis may have been a better alternative or in conjunction with qRT-PCR with marker expressions. The variable choices of CSC and presumed expansion of CSC, left questions as how this expansion was ascertained. The hypothesis of the study may possibly lead to promising cancer treatment therapies, but with these limitations more profound research and analyses are needed.