Less-differentiated Cells Research Articles

Antigen-Stimulated CD4 T Cell Expansion Can Be Limited by Their Grazing of Peptide–MHC Complexes

It was recently shown that the expansion of CD4(+) T cells during a primary immune reaction to a peptide from cytochrome c decreases ~0.5 log for every log increase in the number of cognate precursor cells, and that this remains valid over more than four orders of magnitude (Quiel et al. 2011. Proc. Natl. Acad. Sci. USA. 108: 3312-3317). This observed "power law" was explained by a mechanism where nondividing mature T cells inhibit the proliferation of less-differentiated cells of the same specificity. In this article, we interpret the same data by a mechanism where CD4(+) T cells acquire cognate peptide-MHC (pMHC) complexes from the surface of APCs, thereby increasing the loss rate of pMHC. We show that a mathematical model implementing this "T cell grazing" mechanism, and having a T cell proliferation rate that is determined by the concentration of pMHC, explains the data equally well. As a consequence, the data no longer unequivocally support the previous explanation, and the increased loss of pMHC complexes on APCs at high T cell densities is an equally valid interpretation of this striking data.

Characterization of Adipose-Derived Mesenchymal Stem Cell Combinations for Vascularized Bone Engineering

Since bone repair and regeneration depend on vasculogenesis and osteogenesis, both of these processes are essential for successful vascularized bone engineering. Using adipose-derived stem cells (ASCs), we investigated temporal gene expression profiles, as well as bone nodule and endothelial tubule formation capacities, during osteogenic and vasculogenic ASC lineage commitment. Osteoprogenitor-enriched cell populations were found to express RUNX2, MSX2, SP7 (osterix), BGLAP (osteocalcin), SPARC (osteonectin), and SPP1 (osteopontin) in a temporally specific sequence. Irreversible commitment of ASCs to the osteogenic lineage occurred between days 6 and 9 of differentiation. Endothelioprogenitor-enriched cell populations expressed CD34, PECAM1 (CD31), ENG (CD105), FLT1 (Vascular endothelial growth factor [VEGFR1]), and KDR (VEGFR2). Capacity for microtubule formation was evident in as early as 3 days. Functional capacity was assessed in eight coculture combinations for both bone nodule and endothelial tubule formation, and the greatest expression of these end-differentiation phenotypes was observed in the combination of well-differentiated endothelial cells with less-differentiated osteoblastic cells. Taken together, our results demonstrate vascularized bone engineering utilizing ASCs is a promising enterprise, and that coculture strategies should focus on developing a more mature vascular network in combination with a less mature osteoblastic stromal cell.

Teratoid Hepatoblastoma With Abundant Neuroendocrine and Squamous Differentiation With Extensive Parenchymal Metastasis

Teratoid hepatoblastoma is a rare histologic subtype accounting for 4% to 10% of all hepatoblastomas and is characterized by the presence of divergent differentiation, including squamous, mucinous, melanocytic, cartilaginous, osseous, skeletal muscle, and neural elements. It is postulated that the teratoid elements might derive from multipotential less-differentiated stem cells. Teratoid hepatoblastoma responds poorly to chemotherapy and therefore recognition of this variant has prognostic implications. We describe a 1½-year-old child with teratoid hepatoblastoma characterized by unusual clinical and morphologic patterns including prominent neuroendocrine and squamous differentiation.

Cutting Edge: Asymmetric Memory T Cell Division in Response to Rechallenge

Clonal selection of a T cell for use in the immune response appears to necessitate proliferative expansion and terminal effector differentiation of some cellular progeny, while reserving other progeny as less-differentiated memory cells. It has been suggested that asymmetric cell division may promote initial cell diversification. Stem cell-like models of adaptive immunity might predict that subsequent encounters with a pathogen would evoke reiterative, self-renewing, asymmetric division by memory T cells. In this study, we show that murine memory CD8(+) T cells can divide asymmetrically in response to secondary encounter with pathogen. Critical regulators of signaling and transcription are partitioned to one side of the mitotic spindle in rechallenged memory T cells, and two phenotypically distinct populations of daughter cells are evident from the earliest divisions. Memory T cells may thus use asymmetric cell division to generate cellular heterogeneity when faced with pathogen rechallenge.

Abstract 70: Loss of cellular senescence checkpoint functions reveals the oncogene characteristics of Notch1 in squamous cell carcinomas

Abstract Introduction: Notch signaling regulates cell fates that are dependent upon the CSL transcription factor. Both tumor suppressor and oncogenic roles of Notch have been implicated in the pathogenesis of squamous cell carcinomas (SCCs). We investigated the functional consequences of Notch activation in head and neck as well as esophageal SCCs (HNSCC and ESCC). Methods: Primary tumor tissues annotated with known clinical outcomes were analyzed. Human esophageal cells immortalized with telomerase or human papilloma virus E6/E7 genes, their derivatives expressing mutant p53 and ESCC cell lines were stably transduced with ICN1, an active form of Notch1 in a regulatable manner (Tet-On system). Notch was inhibited by dominant negative mastermind-like1 (DNMAML1), a genetic pan-Notch inhibitor or γ-secretase inhibitors (GSI). 8xCSL-luciferase reporter was used to assess Notch-mediated transcriptional activity. RNA interference was done targeting either CSL or p16INK4A. Senescence was determined by cell growth inhibition and senescence-associated β-galactosidase assays. Cell growth was tested in soft agar and immunodeficient mice. Gene expression was determined by quantitative RT-PCR, Western blotting and immunohistochemistry (IHC). Results: In primary tumors, the active form of Notch1 (ICN1Val1744) was detected as intense nuclear staining of tumor cells in the invasive fronts in 29% of HNSCC (n=17) and 56% of ESCC (n=171). Nuclear ICN1Val1744 was significantly associated with a poor 5-year survival in postsurgical ESCC patients (n=115). In culture, ICN1 induced cellular senescence through CSL-dependent p16INK4A induction, which was antagonized by DNMAML1 or knockdown of either CSL or p16INK4A. Moreover, ICN1 failed to induce senescence in immortalized cells expressing E6/E7 or ESCC cells with a deleted INK4 locus. However, p53 mutation did not prevent ICN1-induced senescence. In soft agar and xenograft transplantation, ICN1 stimulated colony formation and tumor growth of ESCC cells that negated senescence. Histology revealed an increased number of less-differentiated tumor cells upon ICN1 induction. Moreover, GSI treatment of mice with xenografted ESCC cells resulted in tumor necrosis. Conclusions: These data indicate that Notch activation contributes to disease progression in ESCC. While ICN1 induces senescence, loss of p16INK4A-mediated senescence checkpoint point functions may be required in ICN1-mediated malignant transformation, thus providing a novel mechanistic insight into how Notch signaling may contribute to the pathogenesis of SCCs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 70. doi:1538-7445.AM2012-70

Expression of FACT in mammalian tissues suggests its role in maintaining of undifferentiated state of cells

The Facilitates Chromatin Transcription (FACT) chromatin remodeling complex, comprised of two subunits, SSRP1 and SPT16, is involved in transcription, replication and DNA repair. We recently showed that curaxins, small molecules with anti-cancer activity, target FACT and kill tumor cells in a FACT-dependent manner. We also found that FACT is overexpressed in human and mouse tumors and that tumor cells are sensitive to FACT downregulation. To clarify the clinical potential of FACT inhibition, we were interested in physiological role(s) of FACT in multicellular organisms. We analyzed SSRP1 and SPT16 expression in different cells, tissues and conditions using Immunohistochemical (IHC) staining of mouse and human tissues and analysis of publically available high-content gene expression datasets. Both approaches demonstrated coordinated expression of the two FACT subunits, which was primarily associated with the stage of cellular differentiation. Most cells of adult tissues do not have detectable protein level of FACT. High FACT expression was associated with stem or less-differentiated cells, while low FACT levels were seen in more differentiated cells. Experimental manipulation of cell differentiation and proliferation in vitro, as well as tissue staining for the Ki67 proliferation marker, showed that FACT expression is related more to differentiation than to proliferation. Thus, FACT may be part of a stem cell-like gene expression signature and play a role in maintaining cells in an undifferentiated state, which is consistent with its potential role as an anti-cancer target.

Introduction of SV40ER and hTERT into mammospheres generates breast cancer cells with stem cell properties

Emerging evidence suggests that cancers arise in stem/progenitor cells. Yet, the requirements for transformation of these primitive cells remains poorly understood. In this study, we have exploited the 'mammosphere' system that selects for primitive mammary stem/progenitor cells to explore their potential and requirements for transformation. Introduction of Simian Virus 40 Early Region and hTERT into mammosphere-derived cells led to the generation of NBLE, an immortalized mammary epithelial cell line. The NBLEs largely comprised of bi-potent progenitors with long-term self-renewal and multi-lineage differentiation potential. Clonal and karyotype analyses revealed the existence of heterogeneous population within NBLEs with varied proliferation, differentiation and sphere-forming potential. Significantly, injection of NBLEs into immunocompromised mice resulted in the generation of invasive ductal adenocarcinomas. Further, these cells harbored a sub-population of CD44(+)/CD24(-) fraction that alone had sphere- and tumor-initiating potential and resembled the breast cancer stem cell gene signature. Interestingly, prolonged in vitro culturing led to their further enrichment. The NBLE cells also showed increased expression of stemness and epithelial to mesenchymal transition markers, deregulated self-renewal pathways, activated DNA-damage response and cancer-associated chromosomal aberrations-all of which are likely to have contributed to their tumorigenic transformation. Thus, unlike previous in vitro transformation studies that used adherent, more differentiated human mammary epithelial cells our study demonstrates that the mammosphere-derived, less-differentiated cells undergo tumorigenic conversion with only two genetic elements, without requiring oncogenic Ras. Moreover, the striking phenotypic and molecular resemblance of the NBLE-generated tumors with naturally arising breast adenocarcinomas supports the notion of a primitive breast cell as the origin for this subtype of breast cancer. Finally, the NBLEs represent a heterogeneous population of cells with striking plasticity, capable of differentiation, self-renewal and tumorigenicity, thus offering a unique model system to study the molecular mechanisms involved with these processes.

Immunohistochemical localization of notch signaling molecules in ameloblastomas

We examined Notch signaling molecules, Notch1 and Jagged1, in serial large cases of typical solid/multicystic ameloblastoma. In general, Notch positive staining products were frequently detected in the cytoplasms of the cells. In the same cells, Jagged positive staining were also frequently observed, while only occasionally positive in peripheral cells, especially in cuboidal cells. The results showed that these morphogenesis regulation factors are closely related to cytological differentiation in neoplastic cells of ameloblastoma. The Notch and Jagged positive-cell ratios were frequently positive, and the ratios were nearly the same between the varied histopathological, cytological patterns. However, the less-differentiated cells were fewer in number than that of well-differentiated cells.

Isolation and characterization of a population of stem-like progenitor cells from an atypical meningioma

The majority of meningiomas are benign tumors associated with favorable outcomes; however, the less common aggressive variants with unfavorable outcomes often recur and may be due to subpopulations of less-differentiated cells residing within the tumor. These subpopulations of tumor cells have tumor-initiating properties and may be isolated from heterogeneous tumors when sorted or cultured in defined medium. We report the isolation and characterization of a population of tumor-initiating cells derived from an atypical meningioma. We identify a tumor-initiating population from an atypical meningioma, termed meningioma-initiating cells (MICs). These MICs self-renew, differentiate, and can recapitulate the histological characteristics of the parental tumor when transplanted at 1000 cells into the flank regions of athymic nude mice. Immunohistochemistry reveals stem-like protein expression patterns similar to neural stem and progenitor cells (NSPCs) while genomic profiling verified the isolation of cancer cells (with defined meningioma chromosomal aberrations) from the bulk tumor. Microarray and pathway analysis identifies biochemical processes and gene networks related to aberrant cell cycle progression, particularly the loss of heterozygosity of tumor suppressor genes CDKN2A (p16INK4A), p14ARF, and CDKN2B (p15INK4B). Flow cytometric analysis revealed the expression of CD44 and activated leukocyte adhesion molecule (ALCAM/CD166); these may prove to be markers able to identify this cell type. The isolation and identification of a tumor-initiating cell population capable of forming meningiomas demonstrates a useful model for understanding meningioma development. This meningioma model may be used to study the cell hierarchy of meningioma tumorogenesis and provide increased understanding of malignant progression.

In vitro Biomimicry for Vascularized Bone Engineering

Introduction: Bioengineering osseous tissue requires recapitulating the cellular, matrix, and lacunocanalicular components of bone. A construct must have a microvascular network which requires simultaneous co-culture of endothelial and osteogenic cells. Recreation of the matrix requires optimization of composition and microarchitecture. Engineering of constructs large enough to solve actual clinical problems requires novel strategies that address chemotransportative requirements by replicating lacunocanalicular flow. Methods: Cells: Adipose-derived mesenchymal stem cells (MSCs) were isolated and expanded from human lipoaspirate and differentiated into osteoprogenitor-rich (OPC) and endothelioprogenitor-rich (EPC), confirmed by RT-PCR. Normal human osteoblasts (NHOst) and human umbilical vein endothelial cells (HUVEC) served as terminally differentiated cell lines. The effects of co-culture (e.g OPC+HUVEC, OPC+EPC etc) on capacity for bone formation was evaluated by von Kossa assay. Matrix: Murine alveolar defects were created. Scaffolds composed of either absorbable collagen sponge (ACS) or biphasic hydroxyapatite/tri-calcium phosphate (HA-TCP) in a 15/85 ratio were constructed and implanted. HA-TCP scaffolds were further investigated, comparing 15/85 and 60/40 HA/TCP in a rabbit calvarial model. Scaffold pore size (380/180 microns) and strut size (250/180 microns) were also investigated. New bone formation was analyzed histomorphometrically using micro-CT. Lacunocanalicular flow: We have developed a novel flow perfusion bioreactor designed to mimic lacunocanalicular flow. To validate, murine femurs were explanted to the bioreactor for 14 days. Viability and function were evaluated using thiazolyl blue tetrazolium bromide (MTT), DNA quantification, alkaline phosphatase (ALP) assay, and tetracycline labelling. Furthermore, optimal culture conditions were tested with MSC-seeded custom thick 3D HA-TCP scaffolds cultured in static conditions or in flow perfusion. Cellularity was assessed by SEM, DNA quantification and ALP assay. Results: Cells: Proliferation and function were greatest when more-differentiated vasculogenic cells (i.e. HUVECs) were co-cultured with less-differentiated osteogenic cells (i.e. OPCs). For example, co-cultured HUVEC/OPC formed more bone nodules (263,945μm2) than HUVEC/NHOst (179,840μm2) or NHOst alone (89,608μm2). Matrix: HA-TCP showed more bone growth (86±5.8%) than ACS (69±12.4%). With larger pore size, new bone formation pattern resembled cancellous bone whereas smaller pore sizes generated cortical appearing bone. Similarly, larger strut sizes remodeled more slowly than smaller struts. Lacunocanalicular flow: MTT staining confirmed osteocyte viability in flow perfused femur explants, DNA quantification demonstrated up to 100% preservation, ALP activity was upregulated, and fluorochrome labelled mineralizing surfaces were seen throughout. In cell-seeded scaffolds, cellular function was enhanced in flow perfusion eg ALP activity was greater (3.86±0.320 mM/g) than static culture (0.909±0.460 mM/g, p=0.002). SEM demonstrated MSCs were only viable on the periphery static scaffolds but were viable throughout in flow perfusion. Conclusions: Recapitulation of native bone cells, matrix and lacunocanalicular flow can recreate bone constructs for replacement and repair avoiding the limitations associated with traditional autografts or allogeneic transplantation.

HIV Infection Is Associated with a Preferential Decline in Less-Differentiated CD56dimCD16+NK Cells

HIV-1 infection is characterized by loss of CD56(dim) CD16(+) NK cells and increased terminal differentiation on various lymphocyte subsets. We identified a decrease of CD57(-) and CD57(dim) cells but not of CD57(bright) cells on CD56(dim) CD16(+) NK cells in chronic HIV infection. Increasing CD57 expression was strongly associated with increasing frequencies of killer immunoglobulin-like receptors (KIRs) and granzyme B-expressing cells but decreasing percentages of cells expressing CD27(+), HLA-DR(+), Ki-67(+), and CD107a. Our data indicate that HIV leads to a decline of less-differentiated cells and suggest that CD57 is a useful marker for terminal differentiation on NK cells.

More life for a “terminal” cell

More life for a “terminal” cell

Clinical-scale lentiviral vector transduction of PBL for TCR gene therapy and potential for expression in less-differentiated cells.

In human gene therapy applications, lentiviral vectors may have advantages over gamma-retroviral vectors because of their ability to transduce nondividing cells, their resistance to gene silencing, and a lack of integration site preference. In this study, we used VSV-G pseudotype third generation lentiviral vectors harboring specific antitumor T-cell receptor (TCR) to establish clinical-scale lentiviral transduction of peripheral blood lymphocyte (PBL). Spinoculation (1000g, 32 degrees C for 2 h) in the presence of protamine sulfate represents the most efficient and economical approach to transduce a large number of PBLs compared with RetroNectin-based methods. Up to 20 million cells per well of a 6-well plate were efficiently transduced and underwent an average 50-fold expansion in 2 weeks. TCR transduced PBL-mediated specific antitumor activities including interferon-gamma release and cell lysis. Compared with gamma-retroviral vectors, the TCR transgene could be preferentially expressed on a less-differentiated cell population.

Expression analysis of facilitative glucose transporters (GLUTs) in human thyroid carcinoma cell lines and primary tumors

Fluorine-18-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) is based on cell capability to take-up glucose. While a significantly higher expression of the glucose transporter GLUT1 has been reported in thyroid tumors only few data are available on the expression of other GLUT isoforms. We studied several GLUT isoforms expression in thyroid tumor cell lines deriving from anaplastic (ARO, FRO), papillary (NPA), follicular (WRO) and medullary (TT) human thyroid carcinoma. GLUT1 and GLUT3 were also studied in 157 human thyroid malignant and benign tissues. Quantitative Real-time RT-PCR analysis revealed that GLUT1 mRNA levels were higher in less-differentiated cells (ARO, FRO) while GLUT3 mRNA levels were prevalent in well-differentiated cells (NPA, WRO). Accordingly, Western blot showed high expression and correct membrane targeting of GLUT1 protein in ARO and FRO and of GLUT3 protein in NPA and WRO. All cell lines were able to take-up different rates of (3)H-deoxy-glucose. The analysis of GLUT1 and GLUT3 mRNA expression in human thyroid tissues showed the prevalence of GLUT1, but not of GLUT3, in malignant with respect to normal tissues. Finally, both GLUT1 and GLUT3 showed a slightly higher expression in anaplastic than in well-differentiated tumors. In conclusion, we showed that GLUT1 and GLUT3 were the most important glucose transporters in the thyroid tumoral cells. In particular GLUT1 was the most prevalent in less-differentiated cells (ARO and FRO) while GLUT3 was the most prevalent in well-differentiated cells (NPA and WRO). A similar pattern of expression was found for GLUT1 but not for GLUT3 in human thyroid tumors.

An Investigation of the Expression of G1-Phase Cell Cycle Proteins in Focal Cortical Dysplasia Type IIB

Balloon cells (BCs) are the pathologic hallmark of focal cortical dysplasia type IIB, a common cause of pharmacoresistent epilepsy. Expression of markers of cell immaturity and of the proliferation marker minichromosome maintenance protein 2 (mcm2) have been previously shown in BCs, suggesting that these cells might represent a pool of less-differentiated cells licensed for replication. An alternative explanation is that these cells are the remnants of early cortical plate cells that have failed to differentiate or to be eliminated during development and are arrested in the cell cycle, a hypothesis that this study aims to explore. Using immunohistochemical methods and semiquantitative analysis in 19 cases of focal cortical dysplasia (ages 1-81 years), we studied the expression of cell cycle proteins important either in regulating progression through the G1 phase or inducing cell arrest and promoting premature senescence. Only a small fraction of BCs expressed geminin, suggesting that few BCs enter the S phase or complete the cell cycle. Variable expression of nonphosphorylated retinoblastoma protein (Rb), cdk4, and p53 was noted in BCs. Cyclin E, D1, cdk2, phosphorylated Rb (795 and 807/811), and checkpoint 2 expression levels were low in BCs. These findings suggest early rather than late G1 arrest. Cell senescence could be induced by an undefined cerebral insult during development or alternatively represent a physiologic replicative senescence. These findings also suggest that dysregulation of cell cycle pathways may occur in focal cortical dysplasia, which opens further areas for exploration as potential new treatment avenues.

Adenosquamous Carcinoma with Cilium Formation, Mucin Production and Keratinization in the Nasal Cavity of a Red Fox (Vulpes vulpes schrencki)

A diagnosis of adenosquamous carcinoma was made in an 11-year-old red fox. The animal showed emaciation and purulent nasal discharge. Necropsy revealed diffuse thickening of the nasal mucosa and tumours on the soft palate, and there was an oronasal fistula contiguous with the tumours. The nasal and oral lesions were composed of adenocarcinomatous cells and squamous cells, the latter predominating in the oral lesions. The marrow of the palatine bone also contained neoplastic tissue, which consisted of cysts and keratin masses surrounded by well-differentiated squamous cells. Although inconspicuous in the oral cavity and marrow, ciliated cells with or without mucin were observed in the adenocarcinomatous and cystic elements. Neoplastic basal cells and less-differentiated adenocarcinoma cells, which were identifiable by immunolabelling for cytokeratin 5 (CK5) and CK18, were considered to be pluripotential. These cells, which lined tubular structures, were distinct from intermediate cells in mucoepidermoid carcinoma, which can differentiate into squamous and mucin-producing cells but have a nondescript appearance.

P73 expression for human buccal epithelial dysplasia and squamous cell carcinoma: does it correlate with nodal status of carcinoma and is there a relationship with malignant change of epithelial dysplasia?

TP73, a p53 homologue gene, shares similar structural sequences with p53. The aim of this study was to investigate the p73 expression for human buccal epithelial dysplasia (ED) and squamous cell carcinoma (SCC). Seventy-five samples of human buccal ED, including mild, moderate, and severe ED (25 samples in each category), were analyzed for p73 protein expression by means of immunohistochemistry. Twenty-five samples of human buccal SCCs were analyzed for p73 mRNA expression with reverse transcription-polymerase chain reaction (RT-PCR) and were also analyzed for protein expression with immunohistochemical analysis. By use of immunohistochemical analysis, nuclear staining of p73 protein was detected in a subset of normal mucosa, buccal ED, and SCC specimens. p73 nuclear staining was noted for the basal cells of normal buccal mucosa. For buccal lesions deriving from mild, moderate, and severe ED, p73 protein was observed in basal and parabasal layers and in more superficial cell layers corresponding to the spinous layer. For well-differentiated carcinomas, p73 immunoreactivity was chiefly observed among the less-differentiated cells in the periphery of carcinomatous clusters, whereas moderately differentiated carcinomas revealed homogeneous staining, involving nearly all of the tumor cells. On RT-PCR, the expression of p73 mRNA from buccal SCC was noted to be compatible with the findings of immunohistochemical analysis. An electrophoretic band with a 180-bp PCR product corresponding to p73 mRNA has been observed. The expression of p73 seemed to be significantly elevated for specimens of buccal ED (protein level) and SCC (protein and mRNA levels) compared with the analogous expression for normal control tissue (Fisher's exact test, p <.001). Also, p73 expression (protein and mRNA levels) correlated significantly with cervical lymph node metastasis for cases of buccal SCC (Fisher's exact test, p <.001). Eight cases of ED (protein level) showing p73 positivity have undergone malignant transformation to develop SCCs in 2 years follow-up, but no statistical significance was established (Fisher's exact test, p >.05). The data suggest that p73 expression may be (1) associated with the differentiation of oral stratified squamous epithelium, (2) an early event in human oral carcinogenesis, and (3) associated with the nodal status of patients with oral carcinoma and a possible indicator for malignant change of oral ED.

Defining the temporal requirements for Myc in the progression and maintenance of skin neoplasia.

The homeostatic integrity of skin epidermis is maintained by a balance between keratinocyte proliferation, on one hand, and terminal differentiation combined with outward migration and shedding, on the other. Perturbation of this balance in favor of proliferation can result in hyperplasia and, potentially, tumorigenesis. We have previously described a reversible transgenic mouse model of epidermal neoplasia in which expression of an acutely regulatable form of Myc, MycERTAM, is targeted to epidermis via the involucrin promoter. In this model, sustained activation of MycERTAM induces a complex neoplastic lesion involving marked hyperplasia of less-differentiated suprabasal cells, angiogenesis and overt papillomatosis. Subsequent deactivation of MycERTAM triggers complete papilloma regression. Here, we provide evidence that Myc-induced papillomas are self-limiting because of the eventual differentiation of MycERTAM-expressing keratinocytes. Thus, keratinocyte differentiation eventually prevails over Myc-induced proliferation. We also show that regression of Myc-induced papillomas following MycERTAM deactivation occurs through a combination of growth arrest and irreversible differentiation. Finally, we demonstrate that transient deactivation of Myc is sufficient to expel keratinocytes irreversibly from the proliferative compartment and render them refractory to the mitogenic influence of subsequent Myc reactivation. Such observations illustrate the potential utility of even short-term inhibition of oncogenic lesions in the treatment of cancer.

Bone morphogenetic proteins in bone tumors

AbstractBone morphogenetic proteins (BMPs), inducers of ectopic bone formation in vivo, are present in a number of osteosarcomas. BMPs are responsible for reactive bone formation, including periosteal reactions by normal osteoblasts, rather than production of tumorous osteoid by tumor cells. Osteosarcomas producing BMPs contain less-differentiated mesenchymal cells, resulting in a poorer prognosis for those patients. BMPs are also expressed in malignant fibrous histiocytomas (MFHs) of bone and dedifferentiated chondrosarcomas exhibiting undifferentiated features. However, BMPs in MFH do not show any osteoinductive activity in vivo, suggesting that those BMPs may be inactive forms and have additional functions unrelated to bone formation. Among benign bone tumors, BMPs are expressed in osteoid osteomas or osteoblastomas and effect reactive bone formation such as a surrounding sclerosis. BMPs and a BMP receptor (BMPRIB) are also detected in the cartilage cap in osteochondroma, suggesting that BMP signaling via BMPRIB might be involved in the pathogenesis of osteochondroma. Clinically, BMPs have utility as diagnostic and prognostic markers for characterizing the stage of differentiation of mesenchymal cells and mesenchymal tumors, and they may be of value in predicting the prognosis of sarcoma patients. This article reviews the accumulated information on BMPs in bone tumors, including the most recent findings, and discusses the biological and clinical significance of BMPs in bone tumors.

Vascular Endothelial Growth Factor in Human Milk

After completing this article, readers should be able to: 1. Delineate the fundamental advantages conferred by dietary regulation of genes expressed in the intestinal epithelium. 2. Describe the relationship between vascular endothelial growth factor in human milk and gestational age and duration of lactation. As discussed in the article on the physicochemical environment of the neonatal intestine in this issue, the intestine interacts with the external environment to the benefit of the host. The intestine changes the environment (albeit minimally), and the removal of nutrients provides the energy and building materials for life. Thus, the interaction of the intestine and the environment is a basic function. Dietary regulation of genes expressed in the epithelium confers three fundamental advantages for mammals. First, it enables the epithelium to adapt to the luminal environment to digest absorbed food better. Second, it provides the means for human milk to influence the development of the gastrointestinal tract. Third, epithelial expression of proteins that act on the immune system constitutes a signaling mechanism from the intestinal lumen to host defenses. This third mechanism is described in the article on dietary regulation of immune genes …