Visualizing Activated Myofibroblasts Resulting from Differentiation of Mesenchymal Stem Cells.

Mesenchymal stem cells (MSCs) are multipotent cells that exhibit two main characteristics which define stem cells: self-renewal and differentiation. MSCs can migrate to sites of injury, inflammation, and tumor. Moreover, MSCs undergo myofibroblast-like differentiation, including increased production of α-SMA in response to transforming growth factor-ß (TGF-ß), a growth factor commonly secreted by tumor cells to evade immune surveillance. Based on our previous findings, hMSCs become activated and resemble carcinoma-associated myofibroblasts upon prolonged exposure to a conditioned medium from MDAMB231 human breast cancer cells. In this section, we show using immunofluorescence that keratinocyte-conditioned medium (KCM) induces differentiation of MSCs to resemble dermal myofibroblast-like cells with punctate vinculin staining and F-actin filaments.

Melanoblast transcriptome analysis reveals pathways promoting melanoma metastasis.

Cutaneous malignant melanoma is an aggressive cancer of melanocytes with a strong propensity to metastasize. We posit that melanoma cells acquire metastatic capability by adopting an embryonic-like phenotype, and that a lineage approach would uncover metastatic melanoma biology. Using a genetically engineered mouse model to generate a rich melanoblast transcriptome dataset, we identify melanoblast-specific genes whose expression contribute to metastatic competence and derive a 43-gene signature that predicts patient survival. We identify a melanoblast gene, KDELR3, whose loss impairs experimental metastasis. In contrast, KDELR1 deficiency enhances metastasis, providing the first example of different disease etiologies within the KDELR-family of retrograde transporters. We show that KDELR3 regulates the metastasis suppressor, KAI1, and report an interaction with the E3 ubiquitin-protein ligase gp78, a regulator of KAI1 degradation. Our work demonstrates that the melanoblast transcriptome can be mined to uncover targetable pathways for melanoma therapy.

Activation and Differentiation of Mesenchymal Stem Cells.

Mesenchymal stem cells (MSCs) are multipotent cells and exhibit two main characteristics that define stem cells: self-renewal and differentiation. MSCs can migrate to sites of injury, inflammation, and tumor. Moreover, MSCs undergo myofibroblast like differentiation, including increased production of α-SMA in response to transforming growth factor-ß (TGF-ß), a growth factor commonly secreted by tumor cells to evade immune surveillance. Based on our previous finding hMSCs become activated and resemble carcinoma-associated myofibroblasts upon prolonged exposure to conditioned medium from MDAMB231 human breast cancer cells. Here, we show that keratinocyte conditioned medium (KCM) induces differentiation of MSCs to resemble dermal myofibroblast like cells using immunofluorescence techniques demonstrating punctate vinculin staining, and F-actin filaments.

A Retrospective Analysis of Precision Medicine Outcomes in Patients With Advanced Cancer Reveals Improved Progression-Free Survival Without Increased Health Care Costs.

PURPOSE: The advent of genomic diagnostic technologies such as next-generation sequencing has recently enabled the use of genomic information to guide targeted treatment in patients with cancer, an approach known as precision medicine. However, clinical outcomes, including survival and the cost of health care associated with precision cancer medicine, have been challenging to measure and remain largely unreported. PATIENTS AND METHODS: We conducted a matched cohort study of 72 patients with metastatic cancer of diverse subtypes in the setting of a large, integrated health care delivery system. We analyzed the outcomes of 36 patients who received genomic testing and targeted therapy (precision cancer medicine) between July 1, 2013, and January 31, 2015, compared with 36 historical control patients who received standard chemotherapy (n = 29) or best supportive care (n = 7). RESULTS: The average progression-free survival was 22.9 weeks for the precision medicine group and 12.0 weeks for the control group ( P = .002) with a hazard ratio of 0.47 (95% CI, 0.29 to 0.75) when matching on age, sex, histologic diagnosis, and previous lines of treatment. In a subset analysis of patients who received all care within the Intermountain Healthcare system (n = 44), per patient charges per week were $4,665 in the precision treatment group and $5,000 in the control group ( P = .126). CONCLUSION: These findings suggest that precision cancer medicine may improve survival for patients with refractory cancer without increasing health care costs. Although the results of this study warrant further validation, this precision medicine approach may be a viable option for patients with advanced cancer.

Integrated Genomics Identifies miR-32/MCL-1 Pathway as a Critical Driver of Melanomagenesis: Implications for miR-Replacement and Combination Therapy.

AIMS: Cutaneous malignant melanoma is among the deadliest human cancers, broadly resistant to most clinical therapies. A majority of patients with BRAFV600E melanomas respond well to inhibitors such as vemurafenib, but all ultimately relapse. Moreover, there are no viable treatment options available for other non-BRAF melanoma subtypes in the clinic. A key to improving treatment options lies in a better understanding of mechanisms underlying melanoma progression, which are complex and heterogeneous. METHODS: In this study we integrated gene and microRNA (miRNA) expression data from genetically engineered mouse models of highly and poorly malignant melanocytic tumors, as well as available human melanoma databases, and discovered an important role for a pathway centered on a tumor suppressor miRNA, miR-32. RESULTS: Malignant tumors frequently exhibited poor expression of miR-32, whose targets include NRAS, PI3K and notably, MCL-1. Accordingly, MCL-1 was often highly expressed in melanomas, and when knocked down diminished oncogenic potential. Forced MCL-1 overexpression transformed immortalized primary mouse melanocytes, but only when also expressing activating mutations in BRAF, CRAF or PI3K. Importantly, both miR-32 replacement therapy and the MCL-1-specific antagonist sabutoclax demonstrated single-agent efficacy, and acted synergistically in combination with vemurafenib in preclinical melanoma models. CONCLUSIONS: We here identify miR-32/MCL-1 pathway members as key early genetic events driving melanoma progression, and suggest that their inhibition may be an effective anti-melanoma strategy irrespective of NRAS, BRAF, and PTEN status.

Keratinocyte Induced Differentiation of Mesenchymal Stem Cells into Dermal Myofibroblasts: A Role in Effective Wound Healing.

We have previously demonstrated that human mesenchymal stem cells (hMSCs) migrate toward human keratinocytes as well as toward conditioned medium from cultured human keratinocytes (KCM) indicating that the hMSCs respond to signals from keratinocytes [1]. Using fluorescently labeled cells we now show that in vitro hMSCs appear to surround keratinocytes, and this organization is recapitulated in vivo. Incubation of hMSCs with KCM induced dermal myofibroblast like differentiation characterized by expression of cytoskeletal markers and increased expression of cytokines including SDF-1, IL-8, IL-6 and CXCL5. Interaction of keratinocytes with hMSCs appears to be important in the wound healing process. Therapeutic efficacy of hMSCs in wound healing was examined in two animal models representing normal and chronic wound healing. Accelerated wound healing was observed when hMSCs and KCM exposed hMSCs (KCMSCs) were injected near wound site in nude and NOD/SCID mice. Long term follow up of wound healing revealed that in the hMSC treated wounds there was little evidence of residual scarring. These dermal myofibroblast like hMSCs add to the wound healing process. Together, the keratinocyte and hMSCs morphed dermal myofibroblast like cells as well as the factors secreted by these cells support wound healing with minimal scarring. The ability of hMSCs to support wound healing process represents another striking example of the importance of keratinocyte and hMSCs interplay in the wound microenvironment resulting in effective wound healing with minimal scarring.

Antagonistic cross-regulation between Sox9 and Sox10 controls an anti-tumorigenic program in melanoma.

Melanoma is the most fatal skin cancer, but the etiology of this devastating disease is still poorly understood. Recently, the transcription factor Sox10 has been shown to promote both melanoma initiation and progression. Reducing SOX10 expression levels in human melanoma cells and in a genetic melanoma mouse model, efficiently abolishes tumorigenesis by inducing cell cycle exit and apoptosis. Here, we show that this anti-tumorigenic effect functionally involves SOX9, a factor related to SOX10 and upregulated in melanoma cells upon loss of SOX10. Unlike SOX10, SOX9 is not required for normal melanocyte stem cell function, the formation of hyperplastic lesions, and melanoma initiation. To the contrary, SOX9 overexpression results in cell cycle arrest, apoptosis, and a gene expression profile shared by melanoma cells with reduced SOX10 expression. Moreover, SOX9 binds to the SOX10 promoter and induces downregulation of SOX10 expression, revealing a feedback loop reinforcing the SOX10 low/SOX9 high ant,m/ii-tumorigenic program. Finally, SOX9 is required in vitro and in vivo for the anti-tumorigenic effect achieved by reducing SOX10 expression. Thus, SOX10 and SOX9 are functionally antagonistic regulators of melanoma development.

p53 loss increases the osteogenic differentiation of bone marrow stromal cells.

The tumor suppressor, p53, plays a critical role in suppressing osteosarcoma. Bone marrow stromal cells (BMSCs, also known as bone marrow-derived mesenchymal stem cells) have been suggested to give rise to osteosarcomas. However, the role of p53 in BMSCs has not been extensively explored. Here, we report that p53 regulates the lineage choice of mouse BMSCs (mBMSCs). Compared to mBMSCs with wild-type p53, mBMSCs deficient in p53 have enhanced osteogenic differentiation, but with similar adipogenic and chondrogenic differentiation. The role of p53 in inhibiting osteogenic lineage differentiation is mainly through the action of Runx2, a master transcription factor required for the osteogenic differentiation of mBMSCs. We find that p53 indirectly represses the expression of Runx2 by activating the microRNA-34 family, which suppresses the translation of Runx2. Since osteosarcoma may derive from BMSCs, we examined whether p53 has a role in the osteogenic differentiation of osteosarcoma cells and found that osteosarcoma cells with p53 deletion have higher levels of Runx2 and faster osteogenic differentiation than those with wild-type p53. A systems biology approach reveals that p53-deficient mBMSCs are more closely related to human osteosarcoma while mBMSCs with wild-type p53 are similar to normal human BMSCs. In summary, our results indicate that p53 activity can influence cell fate specification of mBMSCs, and provide molecular and cellular insights into the observation that p53 loss is associated with increased osteosarcoma incidence.

A polymorphism in IRF4 affects human pigmentation through a tyrosinase-dependent MITF/TFAP2A pathway.

Sequence polymorphisms linked to human diseases and phenotypes in genome-wide association studies often affect noncoding regions. A SNP within an intron of the gene encoding Interferon Regulatory Factor 4 (IRF4), a transcription factor with no known role in melanocyte biology, is strongly associated with sensitivity of skin to sun exposure, freckles, blue eyes, and brown hair color. Here, we demonstrate that this SNP lies within an enhancer of IRF4 transcription in melanocytes. The allele associated with this pigmentation phenotype impairs binding of the TFAP2A transcription factor that, together with the melanocyte master regulator MITF, regulates activity of the enhancer. Assays in zebrafish and mice reveal that IRF4 cooperates with MITF to activate expression of Tyrosinase (TYR), an essential enzyme in melanin synthesis. Our findings provide a clear example of a noncoding polymorphism that affects a phenotype by modulating a developmental gene regulatory network.

Cell-free derivatives from mesenchymal stem cells are effective in wound therapy.

AIM: To compare the efficacy of cell-free derivatives from Bone marrow derived human mesenchymal stem cells (hMSCs) in wound therapy. METHODS: hMSCs have been shown to play an important role in wound therapy. The present study sought to compare efficacy of hMSCs and cell-free derivatives of hMSCs, which may be clinically more relevant as they are easier to prepare, formulate and transport. hMSCs were isolated from human bone marrow and cultured. Multi lineage differentiation of hMSCs was performed to confirm their identity. The ability of hMSCs to migrate was evaluated using in vitro and in vivo migration assays. Cell lysates and conditioned medium concentrate was prepared from hMSCs (see Methods for details). Wounds were induced in mice and wound areas were measure before and after cell and cell-free derivative treatment. RNA and proteins were extracted from the skin and cytokine levels were measured. RESULTS: Co-culture of hMSCs with keratinocytes resulted in increased expression of CXCL-12 (SDF1) and ENA78 (CXCL-5) in the conditioned media indicating that the hMSCs can respond to signals from keratinocytes. Accelerated wound closure was observed when hMSCs were injected near the site of excisional wounds in athymic as well as NOD/SCID mice. Interestingly, cell-free lysates prepared from hMSCs were also effective in inducing accelerated wound closure and increased expression of SDF1 and CXCL-5 at the wound bed. Additionally, concentrated media from hMSCs as well as an emulsion containing lysates prepared from hMSCs was also found to be more effective in rapid re-epithelialization than fibroblasts or vehicle-alone control. Use of cell-free derivatives may help replace expensive wound care approaches including use of growth factors, epidermal/dermal substitutes, synthetic membranes, cytokines, and matrix components, and most importantly avoid transmission of pathogens from human and animal products. CONCLUSION: These results encourage development of derivatives of hMSCs for wound care and re-epithelialization applications.

Activation and differentiation of mesenchymal stem cells.

Mesenchymal stem cells (MSCs) are multipotent cells and exhibit two main characteristics that define stem cells: self-renewal and differentiation. MSCs can migrate to sites of injury, inflammation, and tumor. Moreover, MSCs undergo myofibroblast-like differentiation, including increased production of alpha smooth muscle actin (α-SMA) in response to transforming growth factor-ß (TGF-ß), a growth factor commonly secreted by tumor cells to evade immune surveillance. Based on our previous finding, hMSCs become activated and resemble carcinoma-associated myofibroblasts upon prolonged exposure to conditioned medium from MDAMB231 human breast cancer cells. Here, we show that keratinocyte-conditioned medium (KCM) induces differentiation of MSCs to resemble dermal myofibroblast-like cells using immunofluorescence techniques demonstrating punctate vinculin staining, and F-actin filaments.

Interleukin 6 mediated recruitment of mesenchymal stem cells to the hypoxic tumor milieu.

Mesenchymal stem cells (MSCs) are a heterogeneous population of non-hematopoietic precursor cells predominantly found in the bone marrow. They have been recently reported to home towards the hypoxic tumor microenvironment in vivo. Interleukin-6 is a multifunctional cytokine normally involved in the regulation of the immune and inflammatory response. In addition to its normal function, IL-6 signaling has been implicated in tumorigenesis. Solid tumors develop hypoxia as a result of inadequate O(2) supply. Interestingly, tumor types with increased levels of hypoxia are known to have increased resistance to chemotherapy as well as increased metastatic potential. Here, we present evidence that under hypoxic conditions (1.5% O(2)) breast cancer cells secrete high levels of IL-6, which serve to activate and attract MSCs. We now report that secreted IL-6 acts in a paracrine fashion on MSCs stimulating the activation of both Stat3 and MAPK signaling pathways to enhance migratory potential and cell survival. Inhibition of IL-6 signaling utilizing neutralizing antibodies leads to attenuation of MSC migration. Specifically, increased migration is dependent on IL-6 signaling through the IL-6 receptor. Collectively, our data demonstrate that hypoxic tumor cells specifically recruit MSCs, which through activation of signaling and survival pathways facilitate tumor progression.

MiR-24 tumor suppressor activity is regulated independent of p53 and through a target site polymorphism.

MicroRNAs (miRNAs) are predicted to regulate approximately 30% of all human genes; however, only a few miRNAs have been assigned their targets and specific functions. Here we demonstrate that miR-24, a ubiquitously expressed miRNA, has an anti-proliferative effect independent of p53 function. Cell lines with differential p53 status were used as a model to study the effects of miR-24 on cell proliferation, cell cycle control, gene regulation and cellular transformation. Overexpression of miR-24 in six different cell lines, independent of p53 function, inhibited cell proliferation and resulted in G2/S cell cycle arrest. MiR-24 over expression in cells with wt-p53 upregulated TP53 and p21 protein; however, in p53-null cells miR-24 still induced cell cycle arrest without the involvement of p21. We show that miR-24 regulates p53-independent cellular proliferation by regulating an S-phase enzyme, dihydrofolate reductase (DHFR) a target of the chemotherapeutic drug methotrexate (MTX). Of interest, we found that a miR-24 target site polymorphism in DHFR 3' UTR that results in loss of miR-24-function and high DHFR levels in the cell imparts a growth advantage to immortalized cells and induces neoplastic transformation. Of clinical significance, we found that miR-24 is deregulated in human colorectal cancer tumors and a subset of tumors has reduced levels of miR-24. A novel function for miR-24 as a p53-independent cell cycle inhibitory miRNA is proposed.

Translational modulation of proteins expressed from bicistronic vectors.

Bicistronic vectors are useful tools for exogenous expression of two gene products from a single promoter element; however, reduced expression of protein from the second cistron compared with the first cistron is a common limitation to this approach. To overcome this limitation, we explored use of dihydrofolate reductase (DHFR) complementary DNA encoded in bicistronic vectors to induce a second protein of interest by methotrexate (MTX) treatment. Previous studies have demonstrated that levels of DHFR protein and DHFR fusion protein can be induced translationally following MTX treatment of cells. We demonstrated that in response to MTX treatment, DHFR partner protein in a bicistronic construct is induced for longer periods of time when compared with endogenous DHFR and DHFR fusion protein, in vitro and in vivo. Using rapamycin pretreatment followed by MTX treatment, we also devised a strategy to modulate levels of two proteins expressed from a bicistronic construct in a cap-independent manner. To our knowledge, this is the first report demonstrating that levels of proteins in DHFR-based bicistronic constructs can be induced and modulated using MTX and rapamycin treatment.

Mesenchymal stem cells: flip side of the coin.

Tumor-associated fibroblasts or carcinoma-associated fibroblasts (CAF) play an important role in the growth of epithelial solid tumors. Although the cell type of origin of CAFs has not been conclusively established, it has been shown that they may be bone marrow derived. One side of the mesenchymal stem cell (MSC) coin is the well-accepted therapeutic potential of these cells for regenerative and immunomodulatory purposes. The ominous dark side is revealed by the recent work demonstrating that hMSCs may be a source of CAFs. In this review, we discuss the role of stromal cells in the tumor microenvironment and suggest that by exploring the in vitro/in vivo interplay between different cell types within the tumor milieu, strategies for improved tumor therapy can be developed.

The isolation of novel mesenchymal stromal cell chemotactic factors from the conditioned medium of tumor cells.

Bone marrow-derived mesenchymal stromal cells (MSCs) localize to solid tumors. Defining the signaling mechanisms that regulate this process is important in understanding the role of MSCs in tumor growth. Using a combination of chromatography and electrospray tandem mass spectrometry we have identified novel soluble signaling molecules that induce MSC chemotaxis present in conditioned medium of the breast carcinoma cell line MDA-MB231. Previous work has employed survey strategies using ELISA assay to identify known chemokines that promote MSC chemotaxis. While these studies provide valuable insights into the intercellular signals that impact MSC behavior, many less well-described, but potentially important soluble signaling molecules could be overlooked using these methods. Through the less directed method of column chromatography we have identified novel candidate MSC chemotactic peptides. Two proteins, cyclophilin B and hepatoma-derived growth factor were then further characterized and shown to promote MSC chemotaxis.

Carcinoma-associated fibroblast-like differentiation of human mesenchymal stem cells.

Carcinoma-associated fibroblasts (CAF) have recently been implicated in important aspects of epithelial solid tumor biology, such as neoplastic progression, tumor growth, angiogenesis, and metastasis. However, neither the source of CAFs nor the differences between CAFs and fibroblasts from nonneoplastic tissue have been well defined. In this study, we show that human bone marrow-derived mesenchymal stem cells (hMSCs) exposed to tumor-conditioned medium (TCM) over a prolonged period of time assume a CAF-like myofibroblastic phenotype. More importantly, these cells exhibit functional properties of CAFs, including sustained expression of stromal-derived factor-1 (SDF-1) and the ability to promote tumor cell growth both in vitro and in an in vivo coimplantation model, and expression of myofibroblast markers, including alpha-smooth muscle actin and fibroblast surface protein. hMSCs induced to differentiate to a myofibroblast-like phenotype using 5-azacytidine do not promote tumor cell growth as efficiently as hMSCs cultured in TCM nor do they show increased SDF-1 expression. Furthermore, gene expression profiling revealed similarities between TCM-exposed hMSCs and CAFs. Taken together, these data suggest that hMSCs are a source of CAFs and can be used in the modeling of tumor-stroma interactions. To our knowledge, this is the first report showing that hMSCs become activated and resemble carcinoma-associated myofibroblasts on prolonged exposure to conditioned medium from MDAMB231 human breast cancer cells.

MiRSNPs or MiR-polymorphisms, new players in microRNA mediated regulation of the cell: Introducing microRNA pharmacogenomics.

MicroRNAs are evolutionarily conserved small non-coding RNAs known to inhibit the translation of proteins by binding to the target transcript in the 3' untranslated region. Functional polymorphisms in 3' UTRs of several genes have been reported to be associated with diseases by affecting gene expression. The mechanism by which these polymorphisms affect gene expression and induce variability in a cell is not well understood. It has been suggested that these polymorphisms may interfere with regulatory elements that bind to untranslated region of a gene. Recently, a novel class of functional polymorphisms termed miRSNPs/polymorphisms was reported. defined as a polymorphism present at or near a microRNA binding sites of functional genes that can affect gene expression by interfering with a miRNA function. The work elucidated the mechanism of a functional miRSNP 829C-->T present in 3' UTR of dihydrofolate reductase, an important drug target. The SNP interferes with the miR24 microRNA function and leads to DHFR over expression and methotrexate resistance. In this article we highlight the importance of these miRSNPs or miR-polymorphisms in gene regulation and the mechanism by which these miRSNPs can induce variability in the SNP expressing mutant cell by using drug resistance as an example.

The therapeutic potential of mesenchymal stem cells. Cell- & tissue-based therapy.

Mesenchymal stem cells (MSCs) are multipotent cells with a number of potential therapeutic applications. At present, they are being used in a clinical trial for the treatment of myocardial infarction and are being studied as a therapy for other vascular disorders. Treatments of neurologic disorders and anticancer therapy with MSCs have progressed in light of the migratory properties of MSCs to brain injury and tumors. The osteogenic potential of MSCs is being exploited in work investigating their use in bone regeneration therapy, and the immunomodulatory function of MSCs is being evaluated as a possible therapy for graft-versus-host disease. Here, the authors review recent work contributing to the knowledge of MSC biology and the advances in gene therapy and tissue regeneration using MSCs.

A miR-24 microRNA binding-site polymorphism in dihydrofolate reductase gene leads to methotrexate resistance.

MicroRNAs are predicted to regulate approximately 30% of all human genes by targeting sequences in their 3' UTR. Polymorphisms in 3' UTR of several genes have been reported to affect gene expression, but the mechanism is not fully understood. Here, we demonstrate that 829C-->T, a naturally occurring SNP, near the miR-24 binding site in the 3' UTR of human dihydrofolate reductase (DHFR) affects DHFR expression by interfering with miR-24 function, resulting in DHFR overexpression and methotrexate resistance. miR-24 has a conserved binding site in DHFR 3' UTR. DHFR with WT and 3' UTR containing the 829C-->T mutation were expressed in DG44 cells that lack DHFR. Overexpression of miR-24 in cells with WT DHFR resulted in down-regulation of DHFR protein, whereas no effect on DHFR protein expression was observed in the mutant 3' UTR-expressing cells. Inhibition of endogenous miR-24 with a specific inhibitor led to up-regulation of DHFR in WT and not in mutant cells. Cells with the mutant 3' UTR had a 2-fold increase in DHFR mRNA half-life, expressed higher DHFR mRNA and DHFR protein, and were 4-fold more resistant to methotrexate as compared with WT cells. SNP-829C-->T, therefore, leads to a decrease in microRNA binding leading to overexpression of its target and results in resistance to methotrexate. We demonstrate that a naturally occurring miRSNP (a SNP located at or near a microRNA binding site in 3' UTR of the target gene or in a microRNA) is associated with enzyme overproduction and drug resistance.