A MSC-ing link in metastasis?

Interleukin-6 receptor in spindle-shaped stromal cells, a prognostic determinant of early breast cancer

Spindle-shaped stromal cells, like carcinoma-associated fibroblasts and mesenchymal stem cells, influence tumor behavior and can serve as parameters in the clinical diagnosis, therapy, and prognosis of early breast cancer. Therefore, the aim of this study is to explore the clinicopathological significance of tumor necrosis factor-related apoptosis-induced ligand (TRAIL) receptors (Rs) 2 and 4 (TRAIL-R2 and R4), and interleukin-6 R (IL-6R) in spindle-shaped stromal cells, not associated with the vasculature, as prognostic determinants of early breast cancer patients. Receptors are able to trigger the migratory activity, among other functions, of these stromal cells. We conducted immunohistochemical analysis for the expression of these receptors in spindle-shaped stromal cells, not associated with the vasculature, of primary tumors from early invasive breast cancer patients, and analyzed their association with clinicopathological characteristics. Here, we demonstrate that the elevated levels of TRAIL-R2, TRAIL-R4, and IL-6R in these stromal cells were significantly associated with a higher risk of metastatic occurrence (p = 0.034, 0.026, and 0.006; respectively). Moreover, high expression of TRAIL-R4 was associated with shorter disease-free survival and metastasis-free survival (p = 0.013 and 0.019; respectively). Also, high expression of IL-6R was associated with shorter disease-free survival, metastasis-free survival, and overall survival (p = 0.003, 0.001, and 0.003; respectively). Multivariate analysis showed that IL-6R expression was an independent prognostic factor for disease-free survival and metastasis-free survival (p = 0.035). This study is the first to demonstrate that high levels of IL-6R expression in spindle-shaped stromal cells, not associated with the vasculature, could be used to identify early breast cancer patients with poor outcomes.

Drug-releasing mesenchymal cells strongly suppress B16 lung metastasis in a syngeneic murine model

BACKGROUND

Mesenchymal stromal cells (MSCs) are considered an important therapeutic tool in cancer therapy. They possess intrinsic therapeutic potential and can also be in vitro manipulated and engineered to produce therapeutic molecules that can be delivered to the site of diseases, through their capacity to home pathological tissues. We have recently demonstrated that MSCs, upon in vitro priming with anti-cancer drug, become drug-releasing mesenchymal cells (Dr-MCs) able to strongly inhibit cancer cells growth.

METHODS

Murine mesenchymal stromal cells were loaded with Paclitaxel (Dr-MCsPTX) according to a standardized procedure and their ability to inhibit the growth of a murine B16 melanoma was verified by in vitro assays. The anti-metastatic activity of Dr-MCsPTX was then studied in mice injected i.v. with B16 melanoma cells that produced lung metastatic nodules. Lung nodules were counted under a dissecting stereomicroscope and metastasis investigated by histological analysis.

RESULTS

We found that three i.v. injections of Dr-MCsPTX on day 5, 10 and 15 after tumor injection almost completely abolished B16 lung metastasis. Dr-MCsPTX arrested into lung by interacting with endothelium and migrate toward cancer nodule through a complex mechanism involving primarily mouse lung stromal cells (mL-StCs) and SDF-1/CXCR4/CXCR7 axis.

CONCLUSIONS

Our results show for the first time that Dr-MCsPTX are very effective to inhibit lung metastasis formation. Actually, a cure for lung metastasis in humans is mostly unlikely and we do not know whether a therapy combining engineered MSCs and Dr-MCs may work synergistically. However, we think that our approach using Dr-MCs loaded with PTX may represent a new valid and additive therapeutic tool to fight lung metastases and, perhaps, primary lung cancers in human.

Human mesenchymal stem cells are resistant to Paclitaxel by adopting a non-proliferative fibroblastic state

Human mesenchymal stem cell (hMSC) resistance to the apoptotic effects of chemotherapeutic drugs has been of major interest, as these cells can confer this resistance to tumor microenvironments. However, the effects of internalized chemotherapeutics upon hMSCs remain largely unexplored. In this study, cellular viability and proliferation assays, combined with different biochemical approaches, were used to investigate the effects of Paclitaxel exposure upon hMSCs. Our results indicate that hMSCs are highly resistant to the cytotoxic effects of Paclitaxel treatment, even though there was no detectable expression of the efflux pump P-glycoprotein, the usual means by which a cell resists Paclitaxel treatment. Moreover, Paclitaxel treatment induces hMSCs to adopt a non-proliferative fibroblastic state, as evidenced by changes to morphology, cellular markers, and a reduction in differentiation potential that is not directly coupled to the cytoskeletal effects of Paclitaxel. Taken together, our results show that Paclitaxel treatment does not induce apoptosis in hMSCs, but does induce quiescence and phenotypic changes.

Tumor microenvironment: bone marrow-mesenchymal stem cells as key players

Tumor progression is a multistep phenomenon in which tumor-associated stromal cells perform an intricate cross-talk with tumor cells, supplying appropriate signals that may promote tumor aggressiveness. Among several cell types that constitute the tumor stroma, the discovery that bone marrow-derived mesenchymal stem cells (BM-MSC) have a strong tropism for tumors has achieved notoriety in recent years. Not only are the BM-MSC recruited, but they can also engraft at tumor sites and transdifferentiate into cells such as activated fibroblasts, perivascular cells and macrophages, which will perform a key role in tumor progression. Whether the BM-MSC and their derived cells promote or suppress the tumor progression is a controversial issue. Recently, it has been proposed that proinflammatory stimuli can be decisive in driving BM-MSC polarization into cells with either tumor-supportive or tumor-repressive phenotypes (MSC1/MSC2). These considerations are extremely important both to an understanding of tumor biology and to the putative use of BM-MSC as "magic bullets" against tumors. In this review, we discuss the role of BM-MSC in many steps in tumor progression, focusing on the factors that attract BM-MSC to tumors, BM-MSC differentiation ability, the role of BM-MSC in tumor support or inhibition, the immunomodulation promoted by BM-MSC and metastatic niche formation by these cells.

Metastasis suppressor genes at the interface between the environment and tumor cell growth

The molecular mechanisms and genetic programs required for cancer metastasis are sometimes overlapping, but components are clearly distinct from those promoting growth of a primary tumor. Every sequential, rate-limiting step in the sequence of events leading to metastasis requires coordinated expression of multiple genes, necessary signaling events, and favorable environmental conditions or the ability to escape negative selection pressures. Metastasis suppressors are molecules that inhibit the process of metastasis without preventing growth of the primary tumor. The cellular processes regulated by metastasis suppressors are diverse and function at every step in the metastatic cascade. As we gain knowledge into the molecular mechanisms of metastasis suppressors and cofactors with which they interact, we learn more about the process, including appreciation that some are potential targets for therapy of metastasis, the most lethal aspect of cancer. Until now, metastasis suppressors have been described largely by their function. With greater appreciation of their biochemical mechanisms of action, the importance of context is increasingly recognized especially since tumor cells exist in myriad microenvironments. In this chapter, we assemble the evidence that selected molecules are indeed suppressors of metastasis, collate the data defining the biochemical mechanisms of action, and glean insights regarding how metastasis suppressors regulate tumor cell communication to-from microenvironments.

Mesenchymal stem cells enhance growth and metastasis of colon cancer

Recently, mesenchymal stem cells (MSCs) were reported to migrate to tumor stroma as well as injured tissue. We examined the role of human MSCs in tumor stroma using an orthotopic nude mice model of KM12SM colon cancer. In in vivo experiments, systemically injected MSCs migrated to the stroma of orthotopic colon tumors and metastatic liver tumors. Orthotopic transplantation of KM12SM cells mixed with MSCs resulted in greater tumor weight than did transplantation of KM12SM cells alone. The survival rate was significantly lower in the mixed-cell group, and liver metastasis was seen only in this group. Moreover, tumors resulting from transplantation of mixed cells had a significantly higher proliferating cell nuclear antigen labeling index, significantly greater microvessel area and significantly lower apoptotic index. Splenic injection of KM12SM cells mixed with MSCs, in comparison to splenic injection of KM12SM cells alone, resulted in a significantly greater number of liver metastases. MSCs incorporated into the stroma of primary and metastatic tumors expressed α-smooth muscle actin and platelet-derived growth factor receptor-β as carcinoma-associated fibroblast (CAF) markers. In in vitro experiments, KM12SM cells recruited MSCs, and MSCs stimulated migration and invasion of tumor cells through the release of soluble factors. Collectively, MSCs migrate and differentiate into CAFs in tumor stroma, and they promote growth and metastasis of colon cancer by enhancing angiogenesis, migration and invasion and by inhibiting apoptosis of tumor cells.

Therapeutic potential of mesenchymal stromal cells in a mouse breast cancer metastasis model

BACKGROUND AIMS

Mesenchymal stromal cells (MSC) have been studied intensively in regenerative medicine. However, their therapeutic potential against tumor formation and cancer metastasis is still unclear. The effects of transplantation of MSCs in early-stage of carcinogenesis, should be evaluated.

METHODS

MSC isolated from human umbilical cord blood (UCB) and adipose tissue (AD) were transplanted in a mouse cancer metastasis model. The effects of MSC on tumor growth and metastasis were analyzed. The effects of transplantation of MSC into the mouse model at very early stage carcinogenesis were also evaluated.

RESULTS

Human MSC reduced lung metastasis and inhibited the growth of human breast cancer cells by inducing apoptosis. In addition, transplantation of both UCB and AD MSC into a cancer model with no detectable clinical symptoms did not appear to promote tumor growth or metastasis.

CONCLUSIONS

We evaluated the effect of MSC derived from human UCB and AD tissue in a tumor model. Our findings may help to elucidate the interaction between cancer cells and MSC, as well as the application of MSC to clinical trials.

Mesenchymal stem cells: immunobiology and role in immunomodulation and tissue regeneration

Mesenchymal stem cells (MSC) are multipotent cells that differentiate into osteoblasts, myocytes, chondrocytes and adipocytes as well as insulin-producing cells. The mechanism underlying their in vivo differentiation is not clear and is thought to be caused by spontaneous cell fusion or factors present in the microenvironment. However, their ease of isolation, high 'ex-vivo' expansion potential and ability to differentiate into multiple lineages make them attractive tools for potential use in cell therapy. MSC have been isolated from several tissues, including bone/bone marrow, fat, Wharton's jelly, umbilical cord blood, placenta and pancreas. The 'immunosuppressive' property of human MSC makes them an important candidate for cellular therapy in allogeneic settings. Use of allogeneic MSC for repair of large defects may be an alternative to autologous and allogeneic tissue-grafting procedures. An allogeneic approach would enable MSC to be isolated from any donor, expanded and cryopreserved, providing a readily available source of progenitors for cell replacement therapy. Their immunomodulatory properties have raised the possibility of establishing allogeneic MSC banks for tissue regeneration. These facts are strongly reflected in the current exponential growth in stem cell research in the pharmaceutical and biotechnology communities. Current knowledge regarding the immunobiology and clinical application of MSC needs to be strengthened further to establish MSC as a safe and effective therapeutic tool in regenerative medicine. This paper discusses human MSC with particular reference to the expression of their surface markers, their role as immunomodulators and their multilineage differentiation potential and possible use in tissue regeneration and repair.