Potential osteogenic differentiation of cisplatin-resistant rat malignant fibrous histiocytoma-derived cell lines

Stem cell pathology: histogenesis of malignant fibrous histiocytoma and characterization of myofibroblasts appearing in fibrotic lesions

The concept of "stem cell pathology" is to establish the role of the stem cells by exploring their contribution to lesion development. The somatic stem cells are present in the body. Malignant fibrous histiocytoma (MFH; recently named "undifferentiated pleomorphic sarcoma") includes pluripotential undifferentiated mesenchymal stem cells as a cell element. An antibody (A3) generated by using rat MFH cells as the antigen labels somatic stem cells such as bone marrow stem cells and immature endothelial cells and pericytes, as well as immature epithelial cells in epithelialization. By using A3 and other antibodies recognizing somatic stem cells, it is considered that myofibroblasts appearing in rat fibrotic lesions are developed partly from immature hepatic stellate cells in hepatic fibrosis, immature pancreatic stellate cells in pancreatic fibrosis, pericytes/endothelial cells in neovascularization in injured tissues, as well as via the epithelial-mesenchymal transition. These progenitors may be in the stem cell lineage. In this review, the author introduces the histogenesis of MFH and the characteristics of myofibroblasts appearing in fibrosis, based mainly on the author's studies.

BMP-2 inhibits tumor-initiating ability in human renal cancer stem cells and induces bone formation

PURPOSE

We have previously shown that BMP-2 induces bone formation and inhibits tumorigenicity of cancer stem cells (CSCs) in a human osteosarcoma OS99-1 cell line. In this study, we sought to determine whether BMP-2 can similarly induce bone formation and inhibit the tumorigenicity of renal CSCs identified based on aldehyde dehydrogenase (ALDH) activity in renal cell carcinoma (RCC) cell lines and primary tumors.

METHODS

Using a xenograft model in which cells from human RCC cell lines ACHN, Caki-2, and primary tumors were grown in NOD/SCID mice, renal CSCs were identified as a subset of ALDH(br) cells. The ALDH(br) cells possessed a greater colony-forming efficiency, higher proliferative output, increased expression of stem cell marker genes Oct3/4A, Nanog, renal embryonic marker Pax-2, and greater tumorigenicity compared to cells with low ALDH activity (ALDH(lo) cells), generating new tumors with as few as 25 cells in mice.

RESULTS

In vitro, BMP-2 was found to inhibit the ALDH(br) cell growth, down-regulate the expression of embryonic stem cell markers, and up-regulate the transcription of osteogenic markers. In vivo, all animals receiving a low number of ALDH(br) cells (5 × 10(3)) from ACHN, Caki-2, and primary tumor xenografts treated with 30 µg BMP-2 per animal showed limited tumor growth with significant bone formation, while untreated cells developed large tumor masses without bone formation.

CONCLUSIONS

These results suggest that BMP-2 inhibits the tumor-initiating ability of renal CSCs and induces osseous bone formation. BMP-2 may therefore provide a beneficial strategy for human RCC treatment by targeting the CSC-enriched population.

An artificial fusion protein between bone morphogenetic protein 2 and titanium-binding peptide is functional in vivo

The purpose of this study was to investigate osteogenesis using an artificial fusion protein (AFP) composed of modified bone morphogenetic protein 2 (BMP-2) with a titanium (Ti)-binding peptide (TBP) motif on a Ti surface in vivo. In the in vivostudy, 5-μm thick Ti was coated with electron cyclotron resonance sputtering on a porous carbon scaffold which was then dipped in one of three different mixtures of collagen gel: (1) collagen gel only, (2) collagen gel with TBP, and (3) collagen gel with the AFP between BMP-2 and the TBP motif (AFP-TBP-BMP-2). These scaffolds were then implanted into rat abdominal muscles and were studied histologically at various times and the expression of several bone-related protein messenger RNAs (mRNAs) was also analyzed. The Ti-coated scaffold of the collagen gel with AFP-TBP-BMP-2 produced cartilage in the muscle and the expression of alkaline phosphatase, bone sialoprotein, and runt-related gene 2 mRNAs was significantly increased. These results suggest that the scaffold of the collagen gel with AFP-TBP-BMP-2 accelerates osteogenesis in vivo.

Bone formation induced by BMP-2 in human osteosarcoma cells

Our previous studies demonstrated that BMP-2 inhibits the tumorigenicity of cancer stem cells identified as cells with high aldehyde dehydrogenase activity (ALDH ^br cells) from the human osteosarcoma cell line OS99-1. We further investigated whether BMP-2 is capable of inducing bone formation in OS99-1 cells. Flow cytometry sorting was used to isolate tumorigenic ALDH ^br and non-tumorigenic ALDH ^lo cells. qRT-PCR was used to quantify the gene expression. A xenograft model was used to verify the bone formation in vivo . There was significantly higher mRNA expression of BMPR1B and BMPR2 in ALDH ^lo cells compared with that in ALDH ^br cells and the BMPR1B expression in ALDH ^lo cells was ∼8-fold higher compared to that in ALDH ^br cells. BMP-2 was also found to induce higher transcription of osteogenic markers Runx-2, Osterix (Osx), alkaline phosphatase (ALP) and collagen type I in ALDH ^lo cells compared to ALDH ^br cells, which were mediated by the canonical Smad signaling pathway. In vivo , BMP-2 was identified to induce bone formation in both ALDH ^br and ALDH ^lo cells. All animals receiving 1×10 ⁴ ALDH ^lo cells treated with 30 μ g of BMP-2 per animal showed bone formation within 1–2 weeks after injection in mice. Bone formation induced by BMP-2 in ALDH ^lo cells showed significantly more bone mineral content compared to that in ALDH ^br cells. BMP-2 induces bone formation in heterogeneous osteosarcoma cells and BMP-2 may have a promising therapeutic role for treating human osteosarcoma by inducing differentiation along an osteogenic pathway.

BMP-2 inhibits tumor growth of human renal cell carcinoma and induces bone formation

Bone morphogenetic protein-2 (BMP-2), a member of the transforming growth factor superfamily, has been shown to have inhibitory effect on many tumor types. However, the effect of BMP-2 on human renal cell carcinoma (RCC) is still unknown. We previously showed that BMP-2 inhibits tumorigenicity of cancer stem cells in human osteosarcoma OS99-1 cells. Our study investigates the effect of BMP-2 on human RCC using ACHN and Caki-2 cell lines. Three types of BMP receptors were found to be expressed in ACHN and Caki-2 cells. In vitro, BMP-2 was found to inhibit the growth of ACHN and Caki-2 cells. The antiproliferative effect seems to be due to cell cycle arrest in the G1 phase, which was revealed by flow cytometry analysis. Using reverse transcriptase polymerase chain reaction analysis, we demonstrated BMP-2 upregulated osteogenic markers Runx-2 and Collagen Type I gene expression in ACHN and Caki-2 cells. Treatment of ACHN and Caki-2 cells with BMP-2 induced a rapid phosphorylation of Smad1/5/8. In vivo, all animals receiving low number of ACHN (1 × 10(4)) and Caki-2 (5 × 10(4)) cells treated with 30 μg of BMP-2 per animal showed limited tumor growth with significant bone formation, whereas untreated cells developed large tumor masses without bone formation in immunodeficient non-obese diabetic (NOD)/severe combined immunodeficient (SCID) mice. These results suggest that BMP-2 inhibits growth of RCC as well as causes induction of osseous bone formation. Further research is needed to determine the relationship between inhibition of cell proliferation and bone induction.

BMP-2 inhibits the tumorigenicity of cancer stem cells in human osteosarcoma OS99-1 cell line

Previously, based on high ALDH activity, we showed that cancer stem cells (CSCs) could be identified as ALDH(br) cells from an aggressive human osteosarcoma OS99-1 cell line. In this study, we evaluate the impact of BMP-2 on CSCs.Three types of BMP receptors were expressed in freshly sorted ALDH(br) cells. In vitro, growth of the sorted ALDH(br) cells was inhibited by BMP-2. Using RT-PCR analysis, BMP-2 was found to down-regulate the expression of embryonic stem cell markers Oct3/4, Nanog, and Sox-2, and up-regulate the transcription of osteogenic markers Runx-2 and Collagen Type I. In vivo, all animals receiving ALDH(br) cells treated with BMP-2 did not form significant tumors, while untreated ALDH(br) cells developed large tumor masses in NOD/SCID mice. Immunostaining confirmed few Ki-67 positive cells were present in the sections of tumor containing ALDH(br) cells treated with BMP-2. These results suggest that BMP-2 suppresses tumor growth by reducing the gene expression of tumorigenic factors and inducing the differentiation of CSCs in osteosarcoma. BMP-2 or BMP-2-mimetic drugs, if properly delivered to tumor and combined with traditional therapies, may therefore provide a new therapeutic option for treatment of osteosarcoma.