Proteins from the Wnt pathway are involved in the pathogenesis and progression of mammary phyllodes tumours

Epithelial to mesenchymal transition (EMT) in metaplastic breast cancer and phyllodes breast tumors

Epithelial-mesenchymal transition (EMT), a transdifferentiation program whereby epithelial cells acquire mesenchymal phenotype, is essential during embryonic development. EMT has also been implicated in cancer progression by conferring migratory and metastatic potential, as well as cell plasticity and stem cell like traits, to cancer cells. Metaplastic breast carcinoma (MBC) is a rare aggressive type of breast cancer characterized by the presence of heterologous elements, typically by the existence of epithelial and mesenchymal components. Phyllodes tumors (PTs) are uncommon fibroepithelial neoplasms consisting of epithelial and mesenchymal elements. Although various hypotheses have been proposed on the pathogenesis of these biphasic tumors, there is growing evidence supporting the theory that PTs and MBC could both correlate with cancer related EMT. This review summarizes the existing literature on the emerging role of EMT in the pathogenesis of MBC and PTs. Both malignant PTs and MBC are characterized by poor prognosis. Therefore, several anti-EMT targeting strategies such as blocking upstream signaling pathways, targeting the molecular drivers of EMT and targeting mesenchymal cells and the extracellular matrix, could potentially represent a promising therapeutic approach for patients suffering from these aggressive neoplasms.

Morphological features of 52 cases of breast phyllodes tumours with local recurrence

Typical phyllodes tumours (PTs) of the breast are fibroepithelial neoplasms characterised histologically by stromal hypercellularity and leaf-like structures. However, morphological changes may be atypical in some cases, increasing the difficulty of diagnosis and the likelihood of misdiagnosis. To provide more morphological clues for pathological diagnosis of PTs, we retrospectively analysed 52 PT cases with typical morphological features after recurrence, and summarized the clinicopathological characteristics of the paired primary tumours. We found five special histological features in the primary tumours distinct from classic PTs, namely (1) PTs with epithelioid feature (three cases); (2) PTs with gland-rich feature (eight cases); (3) PTs with fibroadenoma-like feature (20 cases); (4) PTs with myxoid fibroadenoma-like feature (five cases); and (5) PTs with pseudohemangiomatoid stromal hyperplasia–like feature (four cases). All the features can exist independently, and a few cases displayed more than two distinctive features at the same time. In this cohort of recurrent PTs, all the primary tumours were absent of recognisable stromal hypercellularity and leaf-like structures that are the critical diagnostic criteria of PTs; however, they showed some other non-classic characteristics which may provide significant clues for the diagnosis of PTs. Particularly, tumours with epithelioid feature displayed high grade at earlier stages, tumours with fibroadenoma-like feature were most likely to be confused with classical fibroadenomas, and tumours with myxoid feature were prone to be neglected because of their hypocellularity.

SFRP4 drives invasion in gastric cancer and is an early predictor of recurrence

OBJECTIVE

Gastric cancer patients generally have a poor outcome, particularly those with advanced-stage disease which is defined by the increased invasion of cancer locally and is associated with higher metastatic potential. This study aimed to identify genes that were functional in the most fundamental hallmark of cancer, namely invasion. We then wanted to assess their value as biomarkers of gastric cancer progression and recurrence.

DESIGN

Data from a cohort of patients profiled on cDNA expression arrays was interrogated using K-means analysis. This genomic approach classified the data based on patterns of gene expression allowing the identification of the genes most correlated with the invasion of GC. We evaluated the functional role of a key protein from this analysis in invasion and as a biomarker of recurrence after curative resection.

RESULTS

Expression of secreted frizzled-related protein 4 (SFRP4) was identified as directly proportional to gastric cancer invasion. This finding was validated in multiple, independent datasets and its functional role in invasion was also confirmed using invasion assays. A change in serum levels of SFRP4 after curative resection, when coupled with AJCC stage, can accurately predict the risk of disease recurrence after curative therapy in an assay we termed PredictR.

CONCLUSIONS

This simple ELISA-based assay can help predict recurrence of disease after curative gastric cancer surgery irrespective of adjuvant therapy. The results require further evaluation in a prospective trial but would help in the rational prescription of cancer therapies and surveillance to prevent under or over treatment of patients after curative resection.

Expression of lymphoid enhancer-binding factor 1 in breast fibroepithelial lesions

Phyllodes tumors (PTs) are rare epithelial-mesenchymal tumors of the breast with malignant potential. Here, we evaluate the nuclear expression of lymphoid enhancer-binding factor 1 (LEF-1), a transcription factor downstream of Wnt/β-catenin signaling, in fibroepithelial lesions of the breast. Excised fibroepithelial lesions of the breast were retrospectively reviewed, blinded to the original diagnosis, and classified according to World Health Organization (WHO) criteria. A tissue microarray (TMA) was composed with two representative cores from each case, including 24 benign lesions, 11 borderline phyllodes, and 8 malignant PTs. β-Catenin, LEF-1, p120, and E-cadherin immunohistochemistry was performed on the TMA, and staining was quantified. The malignant/borderline PTs showed higher stromal LEF-1 expression than benign tumors (P < 0.001). Stromal cells expressed LEF-1 in 100% (16/16 of core TMA) of malignant phyllodes, compared with 73% (16/22) borderline and 27% (13/48) benign tumors. The average LEF-1 H-score was 24.9, 6.1, and 1.5 for malignant, borderline, and benign tumors, respectively. Nuclear expression of β-catenin in the stromal component was more often seen in malignant than in borderline and benign tumors (44% versus 32% and 23%, respectively). Nine TMA cores of malignant tumors without nuclear β-catenin staining demonstrated LEF-1 expression. Both LEF-1 and nuclear β-catenin showed expression in the majority of borderline/malignant PTs suggesting a biological progression of Wnt/β-catenin pathway activation in the stromal component from benign to malignant tumors. Inhibitors for the Wnt/β-catenin pathway may provide alternative treatment options in the future for malignant or metastatic PTs.

Genotype-phenotype associations in breast pathology: Achievements of the past quarter century

The first genotype-phenotype relationship in breast pathology developed in 1994 with the discovery of the CDH1 gene. This finding eventually provided biological insight into the characteristic morphology of invasive lobular carcinoma. Subsequent investigative efforts have uncovered additional molecular alterations largely responsible for the histology of several breast neoplasms including secretory carcinoma, adenoid cystic carcinoma, tall cell carcinoma with reversed polarity, fibroepithelial lesions, and most recently, adenomyoepithelioma. Evaluation of the genomic landscape of other special types of breast cancer with distinctive growth patterns, such as invasive mucinous carcinoma, have yet to uncover recurring cytogenetic and/or molecular alterations. Despite the lack of a hallmark alteration in mucinous carcinoma, it is important to note the relative decrease in PIK3CA mutations compared with invasive carcinoma of no special type. In this review, we describe the clinical and pathologic features of breast tumors with recognized genotype-phenotype correlations and summarize the molecular alterations of mucinous carcinoma.

Expression of biomarkers in the AKT pathway correlates with malignancy and recurrence in phyllodes tumours of the breast

AIMS

Phyllodes tumours (PTs) of the breast are uncommon fibroepithelial neoplasms with the potential to recur and metastasise. Apart from histological grading, the expression of biological markers and its relationship with tumour behaviour have been topics of interest. The phosphatidylinositol 3-kinase (PI3K)-AKT pathway regulates diverse biological functions, and is one of the most frequently deregulated pathways in cancers. Little is known of PI3K-AKT pathway alteration in PT. We aim to investigate the alterations in different component of AKT pathway in PTs.

METHODS AND RESULTS

This study investigated the expression of four biological markers involved in this pathway (PTEN, INPP4B, PI3KCA and pAKT) in 134 PTs by the use of immunohistochemistry. According to an immunoscore incorporating staining intensity and proportion, low epithelial INPP4B expression (P = 0.045) was associated with recurrence. A trend of association was found for low epithelial PTEN expression with recurrence (P = 0.090). Interestingly, low epithelial INPP4B expression was also associated recurred tumours (P = 0.043). Stromal PI3KCA expression (P = 0.016) and pAKT expression (P = 0.006) were found to be correlated with increased histological grade, but an opposite trend was seen for stromal INPP4B expression (P = 0.018). In addition, epithelial and stromal PTEN expression, PI3KCA expression and pAKT expression showed strong correlations with each other (P ≤ 0.001).

CONCLUSIONS

These findings indicate that alterations in AKT pathway activation may correlate with malignant transformation and recurrence in PT. Low epithelial INPP4B/PTEN expression is associated with shorter recurrence-free survival. These observations suggest that the pathway may play a crucial role in the biological behaviour and progression of PT, and assessing the expression of this pathway may be of value in diagnosis, grading, prognostication, and management.

Genetic analysis of uterine adenosarcomas and phyllodes tumors of the breast

Uterine adenosarcomas and breast phyllodes tumors (PTs) are morphologically similar, being composed of stromal projections in a leaf-like fashion lined by epithelial cells. Here, we investigated whether their histologic similarities would be mirrored at the genetic level. The previously reported repertoires of somatic genetic alterations found in 19 adenosarcomas and 22 PTs (six benign, six borderline, and 10 malignant) were compared. PTs significantly more frequently displayed mutations affecting MED12, the TERT gene promoter and bona fide cancer genes, whereas adenosarcomas harbored a higher rate of MDM2/CDK4 and TERT gene amplifications. Pathway analyses based on the genes affected by somatic genetic alterations in these tumors indicated that Wnt signaling likely plays a role in the biology of adenosarcomas and benign/borderline PTs. In conclusion, despite the differences at the gene level, PTs and adenosarcomas share remarkable morphologic similarities and enrichment for somatic genetic alterations affecting Wnt pathway-related genes.

Breast cancer carcinoma-associated fibroblasts differ from breast fibroblasts in immunological and extracellular matrix regulating pathways

Tumor stroma has been recently shown to play a crucial role in the development of breast cancer. Since the origin of the stromal cells in the tumor is unknown, we have examined differences and similarities between three stromal cell types of mesenchymal origin, namely carcinoma associated fibroblasts from breast tumor (CAFs), fibroblasts from normal breast area (NFs) and bone marrow derived mesenchymal stromal cells (MSCs). In a microarray analysis, immunological, developmental and extracellular matrix -related pathways were over-represented in CAFs when compared to NFs (p<0.001). Under hypoxic conditions, the expression levels of pyruvate dehydrogenase kinase-1 (PDK1) and pyruvate dehydrogenase kinase-4 (PDK4) were lower in CAFs when compared to NFs (fold changes 0.6 and 0.4, respectively). In normoxia, when compared to NFs, CAFs displayed increased expression of glucose transporter 1 (GLUT-1) and PDK1 (fold changes 1.5 and 1.3, respectively). With respect to the assessed surface markers, only CD105 was expressed differently in MSCs when compared to fibroblasts, being more often expressed on MSCs. Cells with myofibroblast features were present in both NF and CAF samples. We conclude, that CAFs differ distinctly from NFs at the gene expression level, this hypothesis was also tested in silico for other available gene expression data.

Phyllodes tumours of the breast: a consensus review

Phyllodes tumours constitute an uncommon but complex group of mammary fibroepithelial lesions. Accurate and reproducible grading of these tumours has long been challenging, owing to the need to assess multiple stratified histological parameters, which may be weighted differently by individual pathologists. Distinction of benign phyllodes tumours from cellular fibroadenomas is fraught with difficulty, due to overlapping microscopic features. Similarly, separation of the malignant phyllodes tumour from spindle cell metaplastic carcinoma and primary breast sarcoma can be problematic. Phyllodes tumours are treated by surgical excision. However, there is no consensus on the definition of an appropriate surgical margin to ensure completeness of excision and reduction of recurrence risk. Interpretive subjectivity, overlapping histological diagnostic criteria, suboptimal correlation between histological classification and clinical behaviour and the lack of robust molecular predictors of outcome make further investigation of the pathogenesis of these fascinating tumours a matter of active research. This review consolidates the current understanding of their pathobiology and clinical behaviour, and includes proposals for a rational approach to the classification and management of phyllodes tumours.

Expression profiling of prostate cancer tissue delineates genes associated with recurrence after prostatectomy

Prostate cancer is a leading cause of cancer death amongst males. The main clinical dilemma in treating prostate cancer is the high number of indolent cases that confer a significant risk of overtreatment. In this study, we have performed gene expression profiling of tumor tissue specimens from 36 patients with prostate cancer to identify transcripts that delineate aggressive and indolent cancer. Key genes were validated using previously published data and by tissue microarray analysis. Two molecular subgroups were identified with a significant overrepresentation of tumors from patients with biochemical recurrence in one of the groups. We successfully validated key transcripts association with recurrence using two publically available datasets totaling 669 patients. Twelve genes were found to be independent predictors of recurrence in multivariate logistical regression analysis. SFRP4 gene expression was consistently up regulated in patients with recurrence in all three datasets. Using an independent cohort of 536 prostate cancer patients we showed SFRP4 expression to be an independent predictor of recurrence after prostatectomy (HR = 1.35; p = 0.009). We identified SFRP4 to be associated with disease recurrence. Prospective studies are needed in order to assess the clinical usefulness of the identified key markers in this study.

Mutational analysis of MED12 exon 2 in a spectrum of fibroepithelial tumours of the breast: implications for pathogenesis and histogenesis

AIMS

Fibroadenomas (FAs) and phyllodes tumours (PTs) are fibroepithelial tumours. Mutations in MED12 exon 2 have been reported in FAs. This study investigated the MED12 mutations in a spectrum of fibroepithelial tumours.

METHODS AND RESULTS

Using direct sequencing, we analysed MED12 exon 2 mutations on 121 samples, including PTs and FAs and variants. We found MED12 mutations in 71.4% of PTs. No significant difference in the mutation frequency was observed between benign, borderline and malignant PTs, and a general lack of correlation existed between mutations and pathological factors associated with PT grading. The mutation patterns were similar between PTs and FAs, with codon 44 being involved most frequently. MED12 mutations were identified in 47.1, 52.6 and 50.0% of complex FAs, juvenile FAs and tubular adenomas (TAs), respectively, and the frequency and mutation patterns were similar between these FA variants and usual FAs.

CONCLUSIONS

The high frequency and similar patterns of MED12 mutations in FAs and various grades of PTs implies that the MED12 mutation is a common and early pathological event in these fibroepithelial tumours. The similar frequency and patterns of the MED12 mutation between FAs and variants suggests that FA variants are bona fide FAs, with identical pathogenesis involving MED12 mutations.

MicroRNAs are differentially deregulated in mammary malignant phyllodes tumour

AIMS

MicroRNAs (miRs) have been shown to play important roles in tumour progression. Their expression pattern can be useful for cancer classification. However, little is known about miRs in mammary phyllodes tumours (PT).

METHODS AND RESULTS

In this study, polymerase chain reaction (PCR)-based miR profiling was performed in a small PT cohort to identify deregulated miRs in malignant PT. The purported roles and targets of these miRs were further validated. Unsupervised clustering of miR expression profiling segregated PT into different grades, implicating the miR profile in PT classification. Among the deregulated miRs, miR-21, miR-335 and miR-155 were validated to be higher in malignant than in lower-grade PT in the independent cohort by quantitative PCR (qPCR) (P ≤ 0.032). Their expression correlated with some of the malignant histological features, including high stromal cellularity, nuclear pleomorphism and mitosis. Subsequent analysis of their downstream proteins, namely PTEN for miR-21/miR-155 and Rb for miR-335, also showed an independent significant negative association between miR and protein expression.

CONCLUSIONS

Differential expression of miRs in PT could be useful in diagnosis and grading of PT. Their deregulated expression, together with the altered downstream targets, implicated their active involvement in PT malignant transformation.

Fibroepithelial tumors of the breast: pathologic and immunohistochemical features and molecular mechanisms

CONTEXT

The 2 main prototypes of fibroepithelial tumors of the breast include fibroadenoma and phyllodes tumor (PT). Although both tumors share some overlapping histologic features, there are significant differences in their clinical behavior and management. Phyllodes tumors have been further divided into clinically relevant subtypes, and there is more than one classification scheme for PT currently in use, suggesting a lack of consistency within different practices. Accurate differentiation between fibroadenoma and PT, as well as the grading of PT, may sometimes be challenging on preoperative core needle biopsy. Some immunohistochemical markers have been suggested to aid in the pathologic classification of these lesions.

OBJECTIVE

To discuss the salient histopathologic features of fibroepithelial tumors and review the molecular pathways proposed for the initiation, progression, and metastasis of PTs. Also, to provide an update on immunohistochemical markers that may be useful in their differential diagnosis and outline the practice and experience at our institution from a pathologic perspective.

DATA SOURCES

Sources included published articles from peer-reviewed journals in PubMed (US National Library of Medicine).

CONCLUSIONS

Fibroepithelial tumor of the breast is a heterogenous group of lesions ranging from fibroadenoma at the benign end of the spectrum to malignant PT. There are overlapping histologic features among various subtypes, and transformation and progression to a more malignant phenotype may also occur. Given the significant clinical differences within various subtypes, accurate pathologic classification is important for appropriate management. Although some immunohistochemical markers may be useful in this differential diagnosis, histomorphology still remains the gold standard.

Molecules involved in epithelial-mesenchymal transition and epithelial-stromal interaction in phyllodes tumors: implications for histologic grade and prognosis

The aim of this study was to investigate the expression of molecules associated with epithelial-mesenchymal transition (EMT) and epithelial-stromal interactions (ESI) and to evaluate their roles in phyllodes tumors (PTs). Tissue microarrays (TMAs) were constructed from 207 PT specimens (157 benign, 34 borderline and 16 malignant). The presence of EMT-related markers including N-cadherin, Twist, TGF-beta, HMGA2, S100A4 and Ezrin as well as ESI-related molecules such as SDF1 and CXCR4 among the TMAs was assessed immunohistochemically. Immunohistochemical results were analyzed in terms of clinicopathologic parameters. For higher grade PTs, expressions of Twist (p < 0.001), HMGA2 (p = 0.005), S100A4 (p < 0.001), CXCR4 (p < 0.001) and TGF-beta (p < 0.001) were higher. As PTs showed higher stromal cellularity, higher stromal mitosis, stromal overgrowth and infiltrative tumor margin, the expressions of Twist, HMGA2 and CXCR4 in the stromal component thereof were increased (p < 0.05). High Twist expression in the stromal component was associated with shorter disease-free survival (DFS) and overall survival (OS) (p < 0.001) as well as shorter OS in multivariate COX analysis (p = 0.031, odds ratio: 24.6). In conclusion, the expressions of Twist, HMGA2, TGF-beta and S100A4, which are EMT-associated molecules, and CXCR4, an ESI-associated molecule, were increased in the stromal component of advanced grade PTs. Further, high expression of Twist in the stromal component was correlated with poorer prognoses.

Genetic ablation of sfrp4 in mice does not affect serum phosphate homeostasis

Serum phosphate levels are regulated by PTH and the fibroblast growth factor 23 (Fgf23)/Klotho endocrine system, which both affect expression of Npt2a and thus the apical reabsorption of phosphate in the proximal renal tubules. In addition to Fgf23, secreted frizzled-related protein 4 (Sfrp4) has recently been implicated as an additional phosphate regulator in vivo and in vitro. Here we demonstrate that ablation of the Sfrp4 gene in mice does not lead to altered serum or urine phosphate levels. Furthermore, Sfrp4 is unable to compensate for the absence of Fgf23 or Klotho because double knockouts have a similar biochemical profile and phenotype as animals with ablation of Fgf23 or Klotho alone. Taken together, our data suggest that Sfrp4 does not contribute to the long-term regulation of serum phosphate levels in mice.

The expression of ADAM23 and its correlation with promoter methylation in non-small-cell lung carcinoma

ADAM23, a member of a disintegrin and metalloprotease (ADAM) family, has been reported to be expressed in several types of tumours. The exact role of ADAM23 and the possible mechanisms in which it is involved in non-small-cell lung carcinoma (NSCLC) remains unclear. Therefore, this study was designed to explore the expression of ADAM23 and its correlation with promoter methylation in NSCLC. Immunohistochemistry and RT-PCR together with Western blotting methods were used to analyse the expression of ADAM23 in 52 cancer tissue samples and eight benign pulmonary lesions as well as four cell lines. The methylated status of ADAM23 gene was determined with methylation-specific PCR (MSP). The results of immunohistochemistry showed that the expression of ADAM23 protein was lower in NSCLC than that in corresponding normal tissues and benign pulmonary lesions (38.5%vs. 86.5% and 87.5%, P < 0.05), and decreased as NSCLC progressed. Meanwhile, methylation of ADAM23 gene was observed in 21 of 52 NSCLC tissues (40.4%), much higher than that of adjacent normal tissues (7.6%) and benign pulmonary lesions (0/8). In the cancer tissues of ADAM23-negative samples, the rate of ADAM23 gene methylation was 50.3% (17/32). ADAM23 expression and its promoter methylation were negatively associated (r = -0.328, P = 0.017). Moreover, weak expression of ADAM23 in methylated cancer cells increased after treatment with 5-aza-2'-deoxycytidine (5-Aza-2'-dC), confirming that methylation was responsible for the gene downregulation. Our results demonstrate that the expression level of ADAM23 is likely to be involved in the progression of NSCLC and its downregulation is probably correlated with promoter methylation. These findings may provide potential diagnostic and prognostic information about NSCLC.

β-catenin/Wnt signalling pathway in fibromatosis, metaplastic carcinomas and phyllodes tumours of the breast

Wnt signalling pathway is known to have a critical role in carcinogenesis and in epithelial-to-mesenchymal transition. Upon Wnt activation, β-catenin is translocated from the membrane to the cytoplasm and nucleus, where it interacts with transcriptional activators. It has been suggested that various spindle cell lesions of the breast may harbour Wnt pathway activation. Given that β-catenin nuclear localization constitutes a good surrogate marker of Wnt canonical pathway activation, we have investigated the distribution of β-catenin in spindle cell lesions of the breast and whether it could be employed in the differential diagnosis of these lesions. A total of 52 metaplastic breast carcinomas, eight fibromatoses and 23 phyllodes tumours were retrieved from our institutions' archives. We performed immunohistochemistry using two anti-β-catenin antibodies. In all, three fibromatoses and 21 metaplastic breast carcinomas were subjected to CTNNB1 (β-catenin encoding gene) mutation analysis by direct gene sequencing. A good correlation between the two antibodies was observed (Spearman's r>0.82, P<0.001). All fibromatoses and 23% of metaplastic breast carcinomas expressed nuclear β-catenin. In fibromatosis, β-catenin was more often diffusely expressed, whereas in metaplastic breast carcinomas, expression was more frequently focal. Membranous β-catenin expression was significantly lower in spindle cell carcinomas than in other subtypes of metaplastic breast carcinomas. In phyllodes tumours, stromal cells of benign and malignant subtypes displayed nuclear β-catenin expression in 94 and 57% of cases, respectively. No CTNNB1 mutation was identified in any of the 21 metaplastic carcinomas analysed, whereas the mutations 45S>S/P and 41T>T/A were found in samples of fibromatosis. In conclusion, β-catenin nuclear expression is a common feature in fibromatoses and in the stromal component of phyllodes tumours, but may also be observed in metaplastic breast carcinomas. β-catenin nuclear expression should not be used as a single marker to differentiate fibromatosis from other spindle cell tumours of the breast.

ARTEMIS stabilizes the genome and modulates proliferative responses in multipotent mesenchymal cells

Background

Unrepaired DNA double-stranded breaks (DSBs) cause chromosomal rearrangements, loss of genetic information, neoplastic transformation or cell death. The nonhomologous end joining (NHEJ) pathway, catalyzing sequence-independent direct rejoining of DSBs, is a crucial mechanism for repairing both stochastically occurring and developmentally programmed DSBs. In lymphocytes, NHEJ is critical for both development and genome stability. NHEJ defects lead to severe combined immunodeficiency (SCID) and lymphoid cancer predisposition in both mice and humans. While NHEJ has been thoroughly investigated in lymphocytes, the importance of NHEJ in other cell types, especially with regard to tumor suppression, is less well documented. We previously reported evidence that the NHEJ pathway functions to suppress a range of nonlymphoid tumor types, including various classes of sarcomas, by unknown mechanisms.

Results

Here we investigate roles for the NHEJ factor ARTEMIS in multipotent mesenchymal stem/progenitor cells (MSCs), as putative sarcomagenic cells of origin. We demonstrate a key role for ARTEMIS in sarcoma suppression in a sensitized mouse tumor model. In this context, we found that ARTEMIS deficiency led to chromosomal damage but, paradoxically, enhanced resistance and proliferative potential in primary MSCs subjected to various stresses. Gene expression analysis revealed abnormally regulated stress response, cell proliferation, and signal transduction pathways in ARTEMIS-defective MSCs. Finally, we identified candidate regulatory genes that may, in part, mediate a stress-resistant, hyperproliferative phenotype in preneoplastic ARTEMIS-deficient MSCs.

Conclusions

Our discoveries suggest that Art prevents genome damage and restrains proliferation in MSCs exposed to various stress stimuli. We propose that deficiency leads to a preneoplastic state in primary MSCs and is associated with aberrant proliferative control and cellular stress resistance. Thus, our data reveal surprising new roles for ARTEMIS and the NHEJ pathway in normal MSC function and fitness relevant to tumor suppression in mesenchymal tissues.