Cancer Letters

Cancer Letters

Volume 280, Issue 1, 18 July 2009, Pages 31-37
Cancer Letters

Naïve human umbilical cord matrix derived stem cells significantly attenuate growth of human breast cancer cells in vitro and in vivo

https://doi.org/10.1016/j.canlet.2009.02.011Get rights and content

Abstract

The effect of un-engineered (naïve) human umbilical cord matrix stem cells (hUCMSC) on the metastatic growth of MDA 231 xenografts in SCID mouse lung was examined. Three weekly IV injections of 5 × 105 hUCMSC significantly attenuated MDA 231 tumor growth as compared to the saline-injected control. IV injected hUCMSC were detected only within tumors or in close proximity to the tumors. This in vivo result was corroborated by multiple in vitro studies such as colony assay in soft agar and [3H]-thymidine uptake. These results suggest that naïve hUCMSC may be a useful tool for cancer cytotherapy.

Introduction

Stem cells can be derived from a variety of sources, such as embryos (embryonic stem cells), bone marrow (MSCs), fetal tissues, cord blood, etc. Among these stem cell sources, embryos and fetal tissues have significant problems associated with moral/ethical issues surrounding their derivation, which impede their adoption into clinical use [1], [2], [3], [4], [5], [6], [7]. With regard to moral/ethical issues, postnatal stem cells offer fewer concerns. Recently, it was found that umbilical cord matrix contains an inexhaustible, non-controversial source of stem cells [8], [9], [10]. In the United States, umbilical cords are routinely discarded after birth. The multipotent UCMSC are isolated from Wharton’s jelly, the mesenchyme-like cushioning material found between the vessels of the umbilical cord [11]. UCMSC have several properties that make them of interest as a source of cells for therapeutic use. For example, they (1) can be isolated in large quantity; (2) are negative for CD34 and CD45; (3) grow robustly and can be frozen/thawed; (4) can be clonally expanded; and (5) can easily be engineered to express exogenous proteins [8], [9], [10].

Tumors are composed of tumor cells and nonmalignant benign cells. The “benign” tumor-associated tissue includes blood vessels, stromal fibroblasts, and infiltrating inflammatory cells [12]. Stromal fibroblasts offer structural support for malignant cells and influence the behavior and aggressiveness of cancers [12]. Malignant cells induce de novo formation of connective tissue in order to provide enough stroma to support cancer growth [13], [14]. Our previous studies indicate that human UCMSC were attracted towards SDF-1 and VEGF under in vitro conditions [15]. We also found that hUCMSC engineered to secrete the cytokine IFN-β (UCMS-IFN-β) are capable of reducing growth of MDA 231 human breast carcinoma cells by inducing apoptosis [16]. It has also been shown that some un-engineered stem cells attenuate multiple tumor cells [17], [18], [19]. If un-engineered naïve UCMSC can also attenuate tumor growth, UCMSC are more clinically valuable since they are easy to prepare in relatively large quantities and are poorly immunogenic in allogeneic transplantation [20]. Furthermore, un-engineered cells are likely to be safer than genetically altered cells. In the present study, we investigated the growth attenuation potential of naïve hUCMSC on MDA 231 human breast carcinoma cells using in vitro cell culture studies and an in vivo mouse xenograft study. We have also studied the expression level of mitogen-activated protein kinases (MAPK, ERK1/2), phosphatidylinositol 3-kinase (PI3K/Akt) and apoptosis-related signaling components in MDA 231 cells alone and MDA 231 cells co-cultured with hUCMSC. Here we report that un-engineered naïve hUCMSC are capable of attenuating human breast cancer cells through attenuating primarily the Akt and MAPK pathways and stimulating the intrinsic apoptosis pathway.

Section snippets

Antibodies

Antibodies against ERK1/2, phospho ERK-1/2, p38, phosphor p38, Akt, phosphor Akt, and PARP were purchased from Cell Signaling Technology (Beverly, MA). An antibody against GAPDH was purchased from Santa Cruz Biotechnology (Santa Cruz, CA). Horseradish peroxidase-conjugated anti-rabbit IgG antibody was from Amersham Biosciences and ECL (Rockford, IL). Western Blotting substrate was from Pierce (Rockford, IL). Anti-human mitochondrial antibody was from Chemicon (Temecula, CA) and Alexa Fluor 488

Human UCMS cells inhibit growth of MDA 231 tumors in SCID mice

To evaluate hUCMSC-dependent growth inhibition of human mammary tumor, MDA 231 cell xenograft study was carried out using female CB17 SCID mice. This study showed that intravenous injection of MDA 231 cells leads to the development of lung tumors and a subsequent increase in lung weight (Fig. 1). However, three weekly intravenous injections of hUCMSC started 8 days after tumor transplantation significantly reduced the tumor burden as observed by measuring the lung weight (Fig. 1).

Discussion

Increasing evidence suggests that adult stem cells can be effective therapeutic tools for various diseases including cancer [22], [23], [24]. Indeed, multiple adult stem cells engineered to express therapeutic genes are reported to be very effective in attenuating various tumors [15], [21], [25]. A drawback of cancer cytotherapy using engineered stem cells is an unexpected gene expression of the transfected gene, or, if viral vectors are used, mutation of the vector into a virulent form or

Conflict of interest

None of the authors has any financial or other interest with regards to the submitted manuscript that might be construed as a conflict of interest.

Acknowledgments

The authors thank Ms. Lara Pickel (Department of Anatomy and Physiology, Kansas State University) for critical reading and constructive comments during the preparation of the manuscript. This work was supported in part by Kansas State University (KSU) Terry C. Johnson Center for Basic Cancer Research, KSU College of Veterinary Medicine Dean’s Fund, NIH P20 RR017686, KSU Targeted Excellence Research grant and the Kansas State Legislature.

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