Glioma stem cells remodel immunotolerant microenvironment in GBM and are associated with therapeutic advancements.

Glioma is the most common primary tumor of the central nervous system (CNS). Glioblastoma (GBM) is incurable with current treatment strategies. Additionally, the treatment of recurrent GBM (rGBM) is often referred to as terminal treatment, necessitating hospice-level care and management. The presence of the blood-brain barrier (BBB) gives GBM a more challenging or "cold" tumor microenvironment (TME) than that of other cancers and gloma stem cells (GSCs) play an important role in the TME remodeling, occurrence, development and recurrence of giloma. In this review, our primary focus will be on discussing the following topics: niche-associated GSCs and macrophages, new theories regarding GSC and TME involving pyroptosis and ferroptosis in GBM, metabolic adaptations of GSCs, the influence of the cold environment in GBM on immunotherapy, potential strategies to transform the cold GBM TME into a hot one, and the advancement of GBM immunotherapy and GBM models.

Research Progress on the Mechanism of Histone Deacetylases in Ferroptosis of Glioma.

Glioma is the most prevalent primary malignant tumor of the central nervous system. While traditional treatment modalities such as surgical resection, radiotherapy, and chemotherapy have made significant advancements in glioma treatment, the prognosis for glioma patients remains often unsatisfactory. Ferroptosis, a novel form of programmed cell death, plays a crucial role in glioma and is considered to be the most functionally rich programmed cell death process. Histone deacetylases have emerged as a key focus in regulating ferroptosis in glioma. By inhibiting the activity of histone deacetylases, histone deacetylase inhibitors elevate acetylation levels of both histones and non-histone proteins, thereby influencing various cellular processes. Numerous studies have demonstrated that histone deacetylases are implicated in the development of glioma and hold promise for its treatment. This article provides an overview of research progress on the mechanism by which histone deacetylases contribute to ferroptosis in glioma.

Inhibition of TGF-ß1-induced epithelial-mesenchymal transition in gliomas by DMC-HA.

DMC-HA, a novel HDAC inhibitor, has previously demonstrated antiproliferative activity against various cancers, including gliomas. However, the role of DMC-HA in the regulation of EMT and its underlying mechanisms remain unknown. This study aimed to explore the effects of DMC-HA on TGF-ß1-induced EMT in human gliomas and the underlying mechanisms involved. Our results showed that TGF-ß1 induced EMT of U87 and U251 cells, leading to a decrease in epithelial marker ZO-1 and an increase in mesenchymal markers N-cadherin and Vimentin. Moreover, TGF-ß1 treatment resulted in a significant increase in the migratory and invasive abilities of the cells. However, treatment with DMC-HA effectively inhibited the augmented migration and invasion of glioma cells induced by TGF-ß1. Additionally, DMC-HA inhibits TGF-ß1-induced EMT by suppressing canonical Smad pathway and non-canonical TGF-ß/Akt and Erk signalling pathways. These findings suggest that DMC-HA has potential therapeutic implications for gliomas by inhibiting EMT progression.

Hypoxia-Responsive T2-to-T1 Dynamically Switchable Extremely Small Iron Oxide Nanoparticles for Sensitive Tumor Imaging In Vivo.

To realize the accurate diagnosis of tumors by magnetic resonance imaging (MRI), switchable magnetic resonance contrast agents (CAs) between T1 and T2 contrast enhancement that are constructed based on extremely small iron oxide nanoparticles (ESIONPs) have been developed in recent years. We herein report, for the first time, a novel ESIONP-based nanocluster (named EAmP), which exhibited hypoxia responsiveness to the tumor microenvironment and offered a T2-to-T1-switchable contrast enhancement function, effectively distinguishing between the normal tissue and tumor tissue. In detail, active perfluorophenyl ester-modified ESIONPs with a diameter of approximately 3.6 nm were initially synthesized, and then 4,4'-azodianiline was used as a cross-linker to facilitate the formation of nanoclusters from ESIONPs through the reaction between the active ester and amine. Finally, poly(ethylene glycol) was further modified onto nanoclusters by utilizing the remaining active ester residues. The resulting EAmP demonstrated satisfactory colloidal stability and favorable biosafety and exhibited a desired T2-to-T1-switchable function, as evidenced by conversion from nanocluster to the dispersed state and a significant decrease in the r2/r1 ratio from 14.86 to 1.61 when exposed to a mimical hypoxic environment in the solution. Moreover, EAmP could decompose into dispersed ESIONPs at the tumor region, resulting in a switch from T2 to T1 contrast enhancement. This T2-to-T1-switchable contrast agent offers high sensitivity and signal-to-noise ratio to realize the accurate diagnosis of tumors. In conclusion, hypoxia-responsive EAmP is a potential MRI nanoprobe for improving the diagnostic accuracy of solid tumors.

Quantitative proteomic dataset of whole protein in three melanoma samples of 92.1, 92.1-A and 92.1-B.

Distant metastasis is common in ocular uveal melanoma (uveal melanoma, UM) [1], with possible identification of relevant protein markers in peripheral blood [2], [3]. Proteomics analyses serve as a basis for the screening of new target proteins. However, it is difficult to determine whether the relevant proteins in peripheral blood are the same kinesins as those in primary lesions and metastases. Specially in this study, human UM cells (92.1) [4] were inoculated into the back of the eyeball and the brain of inbred line nude mice transplanted with enhanced green fluorescent protein (EGFP) [5], respectively, to simulate the growth of UM in situ and in brain metastases. A database was established as follows: Firstly, the xenograft was taken for monoclonal re-culture and amplification. Then, the cells after amplification (92.1-A in the back of the eyeball and 92.1-B in the brain) and their parent cells (92.1) were subjected to Tandem Mass Tag (TMT)-labeling proteomic analysis and liquid chromatography-mass spectrometry (LC-MS). Covering differential proteomes of three cell lines in a pairwise model, the data could be used to further screen the kinesins that play a vital role in regulating the growth of UM.

Proteomics analysis: inhibiting the expression of P62 protein by chloroquine combined with dacarbazine can reduce the malignant progression of uveal melanoma.

BACKGROUND: Although uveal melanoma (UM) at the early stage is controllable to some extent, it inevitably ultimately leads to death due to its metastasis. At present, the difficulty is that there is no way to effectively tackle the metastasis. It is hypothesized that these will be treated by target molecules, but the recognized target molecule has not yet been found. In this study, the target molecule was explored through proteomics. METHODS: Transgenic enhanced green fluorescent protein (EGFP) inbred nude mice, which spontaneously display a tumor microenvironment (TME), were used as model animal carriers. The UM cell line 92.1 was inoculated into the brain ventricle stimulating metastatic growth of UM, and a graft re-cultured Next, the UM cell line 92.1-A was obtained through monoclonal amplification, and a differential proteomics database, between 92.1 and ectopic 92.1-A, was established. Finally, bioinformatics methodologies were adopted to optimize key regulatory proteins, and in vivo and in vitro functional verification and targeted drug screening were performed. RESULTS: Cells and tissues displaying green fluorescence in animal models were determined as TME characteristics provided by hosts. The data of various biological phenotypes detected proved that 92.1-A were more malignant than 92.1. Besides this malignancy, the key protein p62 (SQSTM1), selected from 5267 quantifiable differential proteomics databases, was a multifunctional autophagy linker protein, and its expression could be suppressed by chloroquine and dacarbazine. Inhibition of p62 could reduce the malignancy degree of 92.1-A. CONCLUSIONS: As the carriers of human UM orthotopic and ectopic xenotransplantation, transgenic EGFP inbred nude mice clearly display the characteristics of TME. In addition, the p62 protein optimized by the proteomics is the key protein that increases the malignancy of 92.1 cells, which therefore provides a basis for further exploration of target molecule therapy for refractory metastatic UM.

Novel enhanced GFP-positive congenic inbred strain establishment and application of tumor-bearing nude mouse model.

Transgenic GFP gene mice are widely used. Given the unique advantages of immunodeficient animals in the field of oncology research, we aim to establish a nude mouse inbred strain that stably expresses enhanced GFP (EGFP) for use in transplanted tumor microenvironment (TME) research. Female C57BL/6-Tg(CAG-EGFP) mice were backcrossed with male BALB/c nude mice for 11 generations. The genotype and phenotype of novel inbred strain Foxn1nu .B6-Tg(CAG-EGFP) were identified by biochemical loci detection, skin transplantation and flow cytometry. PCR and fluorescence spectrophotometry were performed to evaluate the relative expression of EGFP in different parts of the brain. Red fluorescence protein (RFP) gene was stably transfected into human glioma stem cells (GSC), SU3, which were then transplanted intracerebrally or ectopically into Foxn1nu .B6-Tg(CAG-EGFP) mice. Cell co-expression of EGFP and RFP in transplanted tissues was further analyzed with the Live Cell Imaging System (Cell'R, Olympus) and FISH. The inbred strain Foxn1nu .B6-Tg(CAG-EGFP) shows different levels of EGFP expression in brain tissue. The hematological and immune cells of the inbred strain mice were close to those of nude mice. EGFP was stably expressed in multiple sites of Foxn1nu .B6-Tg(CAG-EGFP) mice, including brain tissue. With the dual-fluorescence tracing transplanted tumor model, we found that SU3 induced host cell malignant transformation in TME, and tumor/host cell fusion. In conclusion, EGFP is differentially and widely expressed in brain tissue of Foxn1nu .B6-Tg(CAG-EGFP), which is an ideal model for TME investigation. With Foxn1nu .B6-Tg(CAG-EGFP) mice, our research demonstrated that host cell malignant transformation and tumor/host cell fusion play an important role in tumor progression.

Reshaping acetylated peptide selectivity between human BET Brd2 bromodomains BD-I and BD-II in glioblastoma by rationally grafting secondary anchor residues.

Selective inhibition of BET Brd2 BD-I and BD-II bromodomains is expected to elicit subtle pharmacological difference in anti-glioblastoma therapy. Here, structural basis and energetic property underlying the selective interaction of acetylated peptide ligands with Brd2 BD-I and BD-II were investigated in detail using molecular simulation and computational analysis. It is revealed that the acetyl-lysine is, as expected, a primary anchor residue that confers affinity and stability to bromodomain-peptide binding, while few secondary anchor residues flanking the acetyl-lysine determine specificity and selectivity of peptide interaction with different bromodomains. We also demonstrated that peptide selectivity can be totally reversed by only grafting the secondary anchor residues from one to another. As an instance, fluorescence-based assays showed that the Stat3-derived acetylated peptide Stat3_K87 possesses a high affinity to BD-II (KdBD-II = 9.7 µM) and a strong selectivity for BD-II over BD-I (S = 0.21-fold). Grafting the three secondary anchor residues Lys8, Gly11 and Gly13 of a BD-I-over-BD-II selective H4 N-terminal peptide to the corresponding residue positions of Stat3_K87, which results in a grafted counterpart Stat3(KGG)_K87, can completely change the peptide selectivity from the BD-II-over-BD-I (S = 0.21-fold) of Stat3_K87 to the BD-I-over-BD-II (S = 2.5-fold) of Stat3(KGG)_K87.

Establishment of malignantly transformed dendritic cell line SU3-ihDCTC induced by Glioma stem cells and study on its sensitivity to resveratrol.

BACKGROUND: As a factor contributing to the tumor cell drug resistance, tumor microenvironment (TME) is being paid increasingly attention. However, the drug resistance of malignantly transformed cells in TME has rarely been revealed. This paper is designed to investigate the sensitivity of malignantly transformed cell line (ihDCTC) induced by glioma stem cells (GSCs) in TME to chemotherapeutic drugs. METHODS: (1) Establishment of ihDCTC cell line,The bone marrow cells from enhanced green fluorescent protein (EGFP) transgenic nude mice were employed to culture the dendritic cells (DCs) in vitro, which were then co-cultured with red fluorescence protein (RFP) transgenic GSCs (SU3) to obtain ihDCTC (2) Res and Cis were used to intervene in the growth of abovemetioned cell lines in vitro and Res treated in bearing ihDCTC tumor mice, followed by evaluating their drug sensitivity and changes in key signaling proteins via half maximal inhibitory concentration (IC50), tumor mass and immunostaining method. RESULTS: (1) ihDCTC could express CD11c and CD80 as well as possessed immortalized potential, heteroploid chromosomes and high tumorigenicity in nude mice in vivo. (2) At 24 h, 48 h and 72 h, the IC50 value of ihDCTC treated with Cis was 3.62, 3.25 and 2.10 times higher than that of SU3, while the IC50 value of ihDCTC treated with Res was 0.03, 0.47 and 1.19 times as much as that of SU3; (3) The xenograft mass (g) in vivo in the control, Res, Cis and Res + Cis groups were 1.44 ± 0.19, 0.45 ± 0.12, 0.94 ± 0.80 and 0.68 ± 0.35(x ± s) respectively. The expression levels of IL-6, p-STAT3 and NF-κB proteins in the xenograft tissue were significantly reduced only in the Res treatment group. CONCLUSION: In vitro co-culture with GSC can induce the malignant transformation of bone marrow derived dendritic cells, on the one hand, ihDCTC shows higher drug resistance to the traditional chemotherapeutic drug Cis than GSCs, but, on the other hand, appears to be more sensitive to Res than GSCs. Therefore, our findings provide a broader vision not only for the further study on the correlation between TME and tumor drug resistance but also for the exploration of Res anti-cancer value.

Application of YL-1 Needle in Chronic Subdural Hematoma Treatment for Super-Aged Patients.

OBJECTIVE: The proportion of the super-aged population (at the age of 80 or above) in patients with chronic subdural hematoma (CSDH) and the incidence of CSDH of the population have been increasing. Since it is widely accepted that YL-1 needle is effective in CSDH treatment, this paper aimed to probe into the efficacy of YL-1 needle in minimally invasive surgery for super-aged (at the age of 80-90) CSDH patients. METHODS: A retrospective analysis on the clinical information of 17 super-aged CSDH patients having received the YL-1 needle puncture treatment provided by the hospital from May 2012 to December 2016 was performed. At the same time, another 19 CSDH patients (ages 60-79) who were hospitalized during the same period were randomly selected to form a control group. The same surgical treatment was provided for both groups to observe and compare the treatment efficacy. RESULTS: The patients of both groups were cured and discharged. Among the super-aged patients, there was 1 patient with postoperative hematoma recurrence, 1 patient with pneumocephalus, and 1 patient with wound infection; among the aged patients, 1 reported postoperative recurrence and 2 had pneumocephalus; The average length of stay of the super-aged group was 9.235 ±â€Š2.948 days while that of the aged group was 7.316 ±â€Š3.660 days, which showed no statistical difference. CONCLUSION: The YL-1 needle puncture treatment is safe and efficacious for both the super-aged and the aged CSDH patients.

Research on human glioma stem cells in China.

Research on human glioma stem cells began early in the 21st century and since then has become a rapidly growing research field with the number of publications increasing year by year. The research conducted by our diverse group of investigators focused primarily on cell culture techniques, molecular regulation, signaling pathways, cancer treatment, the stem cell microenvironment and the cellular origin and function of glioma stem cells. In particular, we put forward our view that there are inverse or forward transformations among neural stem cells, glial cells and glioma stem cells in glioma tissues under certain conditions. Based on the background of the progress of international research on human glioma stem cells, we aim to share our progress and current findings of human glioma stem cell research in China with colleagues around the world.

Clinical Observation of Treatment of Chronic Subdural Hematoma With Novel Double Needle Minimally Invasive Aspiration Technology.

OBJECTIVE: The aim of the present study was to explore the clinical effects, including the prevention of complications, of the treatment of chronic subdural hematoma with double needle aspiration. METHODS: The clinical data of 31 patients with chronic subdural hematoma treated by double YL-1 needle double skull drilling and 31 controls treated by traditional drilling and drainage were analyzed retrospectively. RESULTS: In the YL-1 needle group, only 1 patient was with hematoma recurrence, 1 patient was with intracranial pneumocephalus, and the remaining patients who were followed up for 3 months achieved a clinical cure. In the traditional drilling and drainage group, 13 patients were with hematoma recurrence within 3 months after the operation and 7 patients were with postoperative intracranial pneumocephalus. CONCLUSIONS: The method of double YL-1 needle is better than the traditional drilling and drainage method for the treatment of chronic subdural hematoma because it reduces the postoperative recurrence rate and complications.

miR-423-5p knockdown enhances the sensitivity of glioma stem cells to apigenin through the mitochondrial pathway.

This study aimed to investigate the effect of miR-423-5p on the sensitivity of glioma stem cells to apigenin and to explore the potential mechanism. Previous research indicated that apigenin can effectively inhibit the proliferation of many cancer cells, including glioma cells, though our data unexpectedly showed that apigenin had no effect on glioma stem cell apoptosis. As many studies have reported that malignant transformation and progression of glioma are due to glioma stem cells, an anti-glioma stem cell approach has become an important direction for glioma treatment. In this study, we found miR-423-5p to be overexpressed in glioma tissues and corresponding glioma stem cells. Downregulation of miR-423-5p repressed glioma stem cell growth but did not cause apoptosis. Based on the concept of "Pharmaco-miR," this study further demonstrated that the combination of miR-423-5p knockdown and apigenin had a notable additive effect on inhibiting proliferation and promoting apoptosis in glioma stem cells. Hoechst staining showed higher apoptosis rates and typical apoptotic morphological changes of the cell nucleus, and JC-1 (5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimi-dazolylcarbocya-nine iodide) staining revealed reduced mitochondrial membrane potential. Further research demonstrated that the mechanism is associated with a shift in the Bax/Bcl-2 ratio, an increased cytochrome c level, Apaf-1 induction, and caspase-3 activation. In conclusion, this study indicates that downregulation of miR-423-5p enhances the sensitivity of glioma stem cells to apigenin through the mitochondrial pathway.

Cathepsin L is involved in X-ray-induced invasion and migration of human glioma U251 cells.

An important therapeutic method of glioblastoma, the most common primary brain tumor, is radiotherapy. However, several studies reported recently that radiation could also promote the invasion and migration of malignant tumor. Herein, we have identified that a significant increase of migration and invasiveness of human glioma U251 cells undergoing X-ray was observed compared to controls, accompanied by the increase of cathepsin L (CTSL), which is a lysosomal cysteine protease overexpressed and secreted by tumor cells. To verify if there was a relationship between CTSL and the X-ray-induced glioma invasion, a CTSL specific inhibitor Z-FY-CHO or a short hairpin RNA interference was used to pretreat U251 cells. As a result, the cell invasion and migration was impaired via down-regulation of CTSL. Additionally, a marked reduction of the cell-signaling molecules Rho kinase was also detected compared with controls. We also found that CTSL is involved in EMT progress: both in vitro and in clinical specimens. Overall, our findings show that CTSL is an important protein which mediates cell invasion and migration of human glioma U251 cells induced by X-ray, and the inhibition of CTSL expression might diminish the invasion of U251 cells by reducing the activity of RhoA and CDC42 as well as EMT positive markers.

Methods of intra-operative treatment of cranioplasty in patients with abnormal bone window flap pressure after decompressive craniectomy.

OBJECTIVE: This study was performed to investigate the method of cranioplasty in patients with abnormal bone window pressure after decompressive craniectomy. METHODS: We performed a retrospective analysis for 25 cases after decompressive craniectomy in patients with abnormal flap pressure of clinical data. RESULTS: Flap pressure increased in 15 cases, including 6 cases of hydrocephalus, 5 cases of contralateral subdural effusion, 2 cases of subdural effusion bone window, 2 cases of bone window cystic encephalomalacia communicating with the ventricle; Flap pressure decreased in 10 cases, including 6 cases of hydrocephalus after ventriculoperitoneal shunt, and 4 cases of low intracranial pressure. ALL of patients were treated by appropriate measures to make the operation smoothly. CONCLUSION: Our data suggest that after analysis of the factors for abnormal bone window flap pressure by decompressive craniectomy and symptomatic treatment, the difficulty of operation and operative complications can be reduced.

miR-22 inhibits the proliferation, motility, and invasion of human glioblastoma cells by directly targeting SIRT1.

Recently, microRNAs (miRNAs), a kind of small and non-coding RNA, can target the downstream molecules. Increasing evidence demonstrates that miRNAs meditate the onset and progression of a variety of tumors. In the present study, we carried out gene transfection, western blot, and reverse transcription PCR (RT-PCR) to explore the role of miR-22 in glioblastoma tissues and cell lines. Here, we verified that the expression of miR-22 was downregulated in glioblastoma tissues and cells rather than matched non-tumor tissues and normal human astrocyte (NHA) cells (p < 0.001). By contrast, SIRT1 messenger RNA (mRNA) and protein were upregulated in glioblastoma tissues and cells (p < 0.001). In vitro miR-22 mimics interfered with cell proliferation, migration, and invasion of U87 and U251 cells. Mechanically, the 3'-untranslated regions (3'-UTRs) of SIRT1 were a direct target of miR-22, leading to the decreased expression of SIRT1 protein in U87 and U251 cells. Meanwhile, miR-22 mimics also inhibited the expression of epidermal growth factor receptor (EGFR) and matrix metallopeptidase 9 (MMP9). In conclusion, miR-22 inhibited cell proliferation, migration, and invasion via targeting the 3'-UTR of SIRT1 in the progression of glioblastoma and miR-22-SIRT1 pathway can be recommended as a potential target for treatment of glioblastoma.

Knockdown of Cathepsin L promotes radiosensitivity of glioma stem cells both in vivo and in vitro.

The presence of glioma stem cells (GSCs) in tumor is relevant for glioma treatment resistance. This study assessed whether knockdown of Cathepsin L can influence GSC growth, tumor radiosensitivity, and clinical outcome. Protein levels of Cathepsin L and stem cell markers (CD133 and Nestin) were analyzed in samples from 90 gliomas of different WHO grades and 6 normal brain tissues by immunohistochemistry. Two glioma stem cell lines with overexpressed Cathepsin L were stably transfected with Cathepsin L short hairpin RNA expression vectors. The effects of Cathepsin L inhibition on radiosensitivity, self-renewal, stemness, DNA damage, and apoptosis were evaluated. In addition, an intracranial animal model and subcutaneous tumor xenografts in nude mice were used to assess tumor response to Cathepsin L inhibition in vivo. Our results proved that expressions of Cathepsin L and CD133, but not of Nestin, correlated with malignant grades of glioma tissues. GSCs with high Cathepsin L and CD133 co-expression were extraordinarily radioresistant. Cathepsin L inhibition with radiotherapy significantly reduced GSC growth, promoted apoptosis, and improved radiosensitivity. Knockdown of Cathepsin L resulted in a dramatic reduction of CD133 expression, as well as the decreased phosphorylation of DNA repair checkpoint proteins (ATM and DNA-PKcs). Furthermore, combination of Cathepsin L inhibition and radiotherapy potently blocked tumor growth and decreased blood vessel formation in vivo. Taken together, these findings suggest Cathepsin L as a promising therapeutic target for clinical therapy in GBM patients.

Advantages of a dual-color fluorescence-tracing glioma orthotopic implantation model: Detecting tumor location, angiogenesis, cellular fusion and the tumor microenvironment.

Various organs of the body have distinct microenvironments with diverse biological characteristics that can influence the growth of tumors within them. However, the mechanisms underlying the interactions between tumor and host cells are currently not well understood. In the present study, a dual-color fluorescence-tracing glioma orthotopic implantation model was developed, in which C6 rat glioma cells labeled with the red fluorescent dye CM-Dil, and SU3 human glioma cells stably expressing red fluorescence protein, were inoculated into the right caudate nucleus of transgenic female C57BL/6 nude mice expressing enhanced green fluorescent protein. The dual-color tracing with whole-body in vivo fluorescence imaging of xenografts was performed using a live imaging system. Frozen sections of the transplanted tumor were prepared for histological analyses, in order to detect the presence of invading tumor cells, blood vessels and cellular fusion. Dual-color images were able to distinguish between red tumor cells and green host cells. The results of the present study suggested that a dual-color fluorescence-tracing glioma orthotopic implantation model may be convenient for detecting tumor location, angiogenesis, cellular fusion, and the tumor microenvironment.

Malignant transformation of host stromal fibroblasts derived from the bone marrow traced in a dual-color fluorescence xenograft tumor model.

Solid tumors are abnormal tissues containing tumor and non-tumor cells, also known as tumor stromal cells. However, the malignant potential of tumor stromal cells remains largely unknown. The aim of the present study was to investigate the malignant potential of host bone marrow­derived stroma cells in transplanted subcutaneous tumors of the glioma stem/progenitor cells (GSPCs) labeled using the dual-color fluorescent tracer technique. The previously established human glioma stem/progenitor cell line SU3 was transfected with red fluorescence protein (SU3-RFP) and transplanted subcutaneously into green fluorescent protein (GFP) transgenic nude mice and chimeric mice in which GFP was only expressed by bone marrow-derived cells (BMDCs). The xenograft tumors were subcultured in vitro and two immortalized GFP-expressing stromal cell lines were cloned from the transplanted tumors. The two cloned cell lines showed an accelerated growth rate, loss of cell contact inhibition, high cloning efficiency, and high DNA content and telocentric (murine) chromosomes with heteroploid characteristics. The tumorigenesis rate (10/10, 1x10(6)) of these host stromal cells was further evidence of malignant transformation. Immunofluorescence assay of the two host cell lines showed that they expressed fibroblast markers such as FAP, S100A4 and α-SMA, as well as mesenchymal cell markers such as CD44 and CD105. In conclusion, bone marrow-derived stromal fibroblasts recruited to tumors have the potential for malignant transformation induced by the tumor microenvironment, which provides new evidence for the role of the stroma in malignant transformation.