Apoptosis induced by inhibition of intercellular contact

Activation of ductal progenitor-like cells from adult human pancreas requires extracellular matrix protein signaling

Ductal progenitor-like cells are a sub-population of ductal cells in the adult human pancreas that have the potential to contribute to regenerative medicine. However, the microenvironmental cues that regulate their activation are poorly understood. Here, we establish a 3-dimensional suspension culture system containing six defined soluble factors in which primary human ductal progenitor-like and ductal non-progenitor cells survive but do not proliferate. Expansion and polarization occur when suspension cells are provided with a low concentration (5% v/v) of Matrigel, a sarcoma cell product enriched in many extracellular matrix (ECM) proteins. Screening of ECM proteins identified that collagen IV can partially recapitulate the effects of Matrigel. Inhibition of integrin α1β1, a major collagen IV receptor, negates collagen IV- and Matrigel-stimulated effects. These results demonstrate that collagen IV is a key ECM protein that stimulates the expansion and polarization of human ductal progenitor-like and ductal non-progenitor cells via integrin α1β1 receptor signaling.

Cell Death, by Any Other Name…

Studies trying to understand cell death, this ultimate biological process, can be traced back to a century ago. Yet, unlike many other fashionable research interests, research on cell death is more alive than ever. New modes of cell death are discovered in specific contexts, as are new molecular pathways. But what is "cell death", really? This question has not found a definitive answer yet. Nevertheless, part of the answer is irreversibility, whereby cells can no longer recover from stress or injury. Here, we identify the most distinctive features of different modes of cell death, focusing on the executive final stages. In addition to the final stages, these modes can differ in their triggering stimulus, thus referring to the initial stages. Within this framework, we use a few illustrative examples to examine how intercellular communication factors in the demise of cells. First, we discuss the interplay between cell-cell communication and cell death during a few steps in the early development of multicellular organisms. Next, we will discuss this interplay in a fully developed and functional tissue, the gut, which is among the most rapidly renewing tissues in the body and, therefore, makes extensive use of cell death. Furthermore, we will discuss how the balance between cell death and communication is modified during a pathological condition, i.e., colon tumorigenesis, and how it could shed light on resistance to cancer therapy. Finally, we briefly review data on the role of cell-cell communication modes in the propagation of cell death signals and how this has been considered as a potential therapeutic approach. Far from vainly trying to provide a comprehensive review, we launch an invitation to ponder over the significance of cell death diversity and how it provides multiple opportunities for the contribution of various modes of intercellular communication.

Alternative Culture Systems for Bovine Oocyte In Vitro Maturation: Liquid Marbles and Differentially Shaped 96-Well Plates

In vivo-matured oocytes exhibit higher developmental competence than those matured in vitro but mimicking the in vivo environment by in vitro conditions has been challenging. Until now, conventional two-dimensional (2D) systems have been used for in vitro maturation of bovine cumulus-oocytes-complexes (COCs). However, using such systems present certain limitations. Therefore, alternative low-cost methodologies may help to optimize oocyte in vitro maturation. Here, we used two different systems to culture COCs and evaluate their potential influence on embryo development and quality. In the first system, we used treated fumed silica particles to create a 3D microenvironment (liquid marbles; LM) to mature COCs. In the second system, we cultured COCs in 96-well plates with different dimensions (flat, ultra-low attachment round-bottom, and v-shaped 96-well plates). In both systems, the nuclear maturation rate remained similar to the control in 2D, showing that most oocytes reached metaphase II. However, the subsequent blastocyst rate remained lower in the liquid marble system compared with the 96-well plates and control 2D systems. Interestingly, a lower total cell number was found in the resulting embryos from both systems (LM and 96-well plates) compared with the control. In conclusion, oocytes matured in liquid marbles or 96-well plates showed no remarkable change in terms of meiotic resumption. None of the surface geometries influenced embryo development while oocyte maturation in liquid marbles led to reduced embryo development. These findings show that different geometry during maturation did not have a large impact on oocyte and embryo development. Lower embryo production after in vitro maturation in liquid marbles was probably detected because in vitro maturation was performed in serum-free medium, which makes oocytes more sensitive to possible toxic effects from the environment.

Neutrophils play a major role in the destruction of the olfactory epithelium during SARS-CoV-2 infection in hamsters

The loss of smell (anosmia) related to SARS-CoV-2 infection is one of the most common symptoms of COVID-19. Olfaction starts in the olfactory epithelium mainly composed of olfactory sensory neurons surrounded by supporting cells called sustentacular cells. It is now clear that the loss of smell is related to the massive infection by SARS-CoV-2 of the sustentacular cells in the olfactory epithelium leading to its desquamation. However, the molecular mechanism behind the destabilization of the olfactory epithelium is less clear. Using golden Syrian hamsters infected with an early circulating SARS-CoV-2 strain harboring the D614G mutation in the spike protein; we show here that rather than being related to a first wave of apoptosis as proposed in previous studies, the innate immune cells play a major role in the destruction of the olfactory epithelium. We observed that while apoptosis remains at a low level in the damaged area of the infected epithelium, the latter is invaded by Iba1+ cells, neutrophils and macrophages. By depleting the neutrophil population or blocking the activity of neutrophil elastase-like proteinases, we could reduce the damage induced by the SARS-CoV-2 infection. Surprisingly, the impairment of neutrophil activity led to a decrease in SARS-CoV-2 infection levels in the olfactory epithelium. Our results indicate a counterproductive role of neutrophils leading to the release of infected cells in the lumen of the nasal cavity and thereby enhanced spreading of the virus in the early phase of the SARS-CoV-2 infection.

Human adipose-derived mesenchymal stem cell spheroids improve recovery in a mouse model of elastase-induced emphysema

Emphysema, a pathologic component of the chronic obstructive pulmonary disease, causes irreversible destruction of lung. Many researchers have reported that mesenchymal stem cells can regenerate lung tissue after emphysema. We evaluated if spheroid human adipose-derived mesenchymal stem cells (ASCs) showed greater regenerative effects than dissociated ASCs in mice with elastase-induced emphysema. ASCs were administered via an intrapleural route. Mice injected with spheroid ASCs showed improved regeneration of lung tissues, increased expression of growth factors such as fibroblast growth factor-2 (FGF2) and hepatocyte growth factor (HGF), and a reduction in proteases with an induction of protease inhibitors when compared with mice injected with dissociated ASCs. Our findings indicate that spheroid ASCs show better regeneration of lung tissues than dissociated ACSs in mice with elastase-induced emphysema.

PEG-peptide hydrogels reveal differential effects of matrix microenvironmental cues on melanoma drug sensitivity

Metastatic melanoma is highly drug resistant, though the exact mechanisms of this resistance are not completely understood. One method to study melanoma drug responsiveness in vitro is through the use of multicellular spheroids, which have been found to exhibit decreased drug sensitivity compared to traditional 2D culture on various substrates. Because it is unclear whether dimensionality, cell-matrix interactions, and/or cell-cell contacts may influence melanoma drug responsiveness, we utilized a synthetic PEG-based hydrogel to compare the responses of cells cultured on top of or encapsulated within matrices with the same adhesive ligand density, polymer density, and material properties. We found that depending on the stage of progression at which the melanoma cells were derived, the cells responded differently to PLX4032 treatment, a commercially available melanoma drug. In particular, early stage WM35 cells were insensitive to dimensionality (i.e., 2D versus 3D culture), while metastatic A375 cells exhibited decreased responsiveness in 3D compared to 2D. To further understand the role of the microenvironment in early stage melanoma cells, we tested single WM35 cells and multicellular WM35 spheroids in 3D. The results revealed that the spheroids were similarly sensitive to PLX4032 treatment compared to single cell encapsulations. Collectively, this study implicates the role that 3D microenvironments (i.e., dimensionality) may play in observed melanoma drug responsiveness, and the potential lack of influence of cell-matrix interactions over cell-cell contacts in early stages of melanoma resistance to PLX4032-induced apoptosis.

Targeting prion-like protein doppel selectively suppresses tumor angiogenesis

Controlled and site-specific regulation of growth factor signaling remains a major challenge for current antiangiogenic therapies, as these antiangiogenic agents target normal vasculature as well tumor vasculature. In this article, we identified the prion-like protein doppel as a potential therapeutic target for tumor angiogenesis. We investigated the interactions between doppel and VEGFR2 and evaluated whether blocking the doppel/VEGFR2 axis suppresses the process of angiogenesis. We discovered that tumor endothelial cells (TECs), but not normal ECs, express doppel; tumors from patients and mouse xenografts expressed doppel in their vasculatures. Induced doppel overexpression in ECs enhanced vascularization, whereas doppel constitutively colocalized and complexed with VEGFR2 in TECs. Doppel inhibition depleted VEGFR2 from the cell membrane, subsequently inducing the internalization and degradation of VEGFR2 and thereby attenuating VEGFR2 signaling. We also synthesized an orally active glycosaminoglycan (LHbisD4) that specifically binds with doppel. We determined that LHbisD4 concentrates over the tumor site and that genetic loss of doppel in TECs decreases LHbisD4 binding and targeting both in vitro and in vivo. Moreover, LHbisD4 eliminated VEGFR2 from the cell membrane, prevented VEGF binding in TECs, and suppressed tumor growth. Together, our results demonstrate that blocking doppel can control VEGF signaling in TECs and selectively inhibit tumor angiogenesis.

Effect of Storage Temperature on Structure and Function of Cultured Human Oral Keratinocytes

Purpose/Aims

To assess the effect of storage temperature on the viability, phenotype, metabolism, and morphology of cultured human oral keratinocytes (HOK).

Materials and Methods

Cultured HOK cells were stored in HEPES- and sodium bicarbonate-buffered Minimum Essential Medium (MEM) at nine temperatures in approximately 4°C increments from 4°C to 37°C for seven days. Cells were characterized for viability by calcein fluorescence, phenotype retention by immunocytochemistry, metabolic parameters (pH, glucose, lactate, and O₂) within the storage medium by blood gas analysis, and morphology by scanning electron microscopy and light microscopy.

Results

Relative to the cultured, but non-stored control cells, a high percentage of viable cells were retained only in the 12°C and 16°C storage groups (85%±13% and 68%±10%, respectively). Expression of ABCG2, Bmi1, C/EBPδ, PCNA, cytokeratin 18, and caspase-3 were preserved after storage in the 5 groups between 4°C and 20°C, compared to the non-stored control. Glucose, pH and pO₂ in the storage medium declined, whereas lactate increased with increasing storage temperature. Morphology was best preserved following storage of the three groups between 12°C, 16°C, and 20°C.

Conclusion

We conclude that storage temperatures of 12°C and 16°C were optimal for maintenance of cell viability, phenotype, and morphology of cultured HOK. The storage method described in the present study may be applicable for other cell types and tissues; thus its significance may extend beyond HOK and the field of ophthalmology.

Novel role for NFAT3 in ERK-mediated regulation of CXCR4

The G-protein coupled chemokine (C-X-C motif) receptor CXCR4 is linked to cancer, HIV, and WHIM (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis) syndrome. While CXCR4 is reported to be overexpressed in multiple human cancer types and many hematological cancer cell lines, we have observed poor in vitro cell surface expression of CXCR4 in many solid tumor cell lines. We explore further the possible factors and pathways involved in regulating CXCR4 expression. Here, we showed that MEK-ERK signaling pathway and NFAT3 transcriptional factor plays a novel role in regulating CXCR4 expression. When cultured as 3D spheroids, HeyA8 ovarian tumor cells showed a dramatic increase in surface CXCR4 protein levels as well as mRNA transcripts. Furthermore, HeyA8 3D spheroids showed a decrease in phospho-ERK levels when compared to adherent cells. The treatment of adherent HeyA8 cells with an inhibitor of the MEK-ERK pathway, U0126, resulted in a significant increase in surface CXCR4 expression. Additional investigation using the PCR array assay comparing adherent to 3D spheroid showed a wide range of transcription factors being up-regulated, most notably a > 20 fold increase in NFAT3 transcription factor mRNA. Finally, chromatin immunoprecipitation (ChIP) analysis showed that direct binding of NFAT3 on the CXCR4 promoter corresponds to increased CXCR4 expression in HeyA8 ovarian cell line. Taken together, our results suggest that high phospho-ERK levels and NFAT3 expression plays a novel role in regulating CXCR4 expression.

3D tumor models: history, advances and future perspectives

ABSTRACT: 

Evaluation of cancer therapeutics by utilizing 3D tumor models, before clinical studies, could be more advantageous than conventional 2D tumor models (monolayer cultures). The 3D systems mimic the tumor microenvironment more closely than 2D systems. The following review discusses the various 3D tumor models present today with the advantages and limitations of each. 3D tumor models replicate the elements of a tumor microenvironment such as hypoxia, necrosis, angiogenesis and cell adhesion. The review introduces application of techniques such as microfluidics, imaging and tissue engineering to improve the 3D tumor models. Despite their tremendous potential to better screen chemotherapeutics, 3D tumor models still have a long way to go before they are used commonly as in vitro tumor models in pharmaceutical industrial research.

The impact of storage temperature on the morphology, viability, cell number and metabolism of cultured human conjunctival epithelium

PURPOSE

To evaluate the effect of storage temperature on the morphology, viability, cell number and metabolism of cultured human conjunctival epithelial cells (HCjEs).

MATERIALS AND METHODS

Three-day cultured HCjEs were stored at nine different temperatures between 4 °C and 37 °C for four and seven days. Phenotype was assessed by immunofluorescence microscopy, morphology by scanning electron microscopy, viability and cell number by a microplate fluorometer and glucose metabolism by a blood gas analyzer.

RESULTS

Cultured cells not subjected to storage expressed the conjunctival cytokeratins 7 and 19 and the proliferation marker proliferating cell nuclear antigen. Cell morphology was best maintained following four-day storage between 12 °C and 28 °C and following 12 °C storage after seven days. Assessed by propidium iodide uptake, the percentage of viable cells after four-day storage was maintained only between 12 °C and 28 °C, whereas it had decreased in all other groups (p < 0.05; n = 4). After seven days this percentage was maintained in the 12 °C group, but it had decreased in all other groups, compared to the control (p < 0.05; n = 4). The total number of cells remaining in the cultures after four-day storage, compared to the control, had declined in all groups (p < 0.05; n = 4), except 12 °C and 20 °C groups. Following seven days this number had decreased in all groups (p < 0.01; n = 4), except 12 °C storage. Four-day storage at 12 °C demonstrated superior preservation of the number of calcein-stained viable cells (p < 0.05) and the least accumulation of ethidium homodimer 1-stained dead cells (p < 0.001), compared to storage at 4 °C and 24 °C (n = 6). The total metabolism of glucose to lactate after four-day storage was higher in the 24 °C group compared to 4 °C and 12 °C groups, as well as the control (p < 0.001; n = 3).

CONCLUSIONS

Storage at 12 °C appears optimal for preserving the morphology, viability and total cell number in stored HCjE cultures. The superior cell preservation at 12 °C may be related to temperature-associated effects on cell metabolism.

Early responses of the STAT3 pathway to platinum drugs are associated with cisplatin resistance in epithelial ovarian cancer

Cisplatin resistance remains one of the major obstacles when treating epithelial ovarian cancer. Because oxaliplatin and nedaplatin are effective against cisplatin-resistant ovarian cancer in clinical trials and signal transducer and activator of transcription 3 (STAT3) is associated with cisplatin resistance, we investigated whether overcoming cisplatin resistance by oxaliplatin and nedaplatin was associated with the STAT3 pathway in ovarian cancer. Alamar blue, clonogenic, and wound healing assays, and Western blot analysis were used to compare the effects of platinum drugs in SKOV-3 cells. At an equitoxic dose, oxaliplatin and nedaplatin exhibited similar inhibitory effects on colony-forming ability and greater inhibition on cell motility than cisplatin in ovarian cancer. Early in the time course of drug administration, cisplatin increased the expression of pSTAT3 (Tyr705), STAT3α, VEGF, survivin, and Bcl-X_L, while oxaliplatin and nedaplatin exhibited the opposite effects, and upregulated pSTAT3 (Ser727) and STAT3β. The STAT3 pathway responded early to platinum drugs associated with cisplatin resistance in epithelial ovarian cancer and provided a rationale for new therapeutic strategies to reverse cisplatin resistance.

Immunolocalization of tenascin-C in vitiligo

The disappearance of melanocytes because of defective adhesion is one of the accepted theories to explain vitiligo. Tenascin-C is a large, extracellular matrix glycoprotein that is thought to inhibit adhesion of melanocytes to fibronectin. The current study aimed to evaluate the pattern of tenascin-C expression in vitiligenous skin compared with normal pigmented skin by means of immunohistochemistry. The study was carried out on skin biopsies from lesional and perilesional skin of 30 patients with vitiligo and on normal skin of 10 healthy volunteers. Several histopathologic changes were observed in vitiliginous skin such as keratinocyte vacuolization, a thickened basement membrane, and dermal inflammatory changes. Tenascin-C was expressed in keratinocytes of the basal epidermal layer of normal skin biopsies at a mild intensity but it did not stain the dermis, whereas vitiligenous skin showed tenascin-C expression in most cases (93.3% ), in the papillary dermis, epidermis, and in both. Diffuse epidermal expression of tenascin-C correlated with more loss of pigment and continuous staining of tenascin-C in the papillary dermis correlated with progressive forms of vitiligo. Intense tenascin-C expression was associated with a more progressive course of the disease assessed by the vitiligo disease activity score. From this study, tenascin-C is highly expressed in the dermis, epidermis, and both of vitiligo as a secondary event for the disease. Keratinocyte is a source of tenascin-C in vitiligo, and diffuse epidermal expression of tenascin-C may induce more loss of melanocytes and melanin pigment. Dermal expression of tenascin-C in the vitiligenous lesion may be linked to the disease more than epidermal expression, because this pattern is only seen in a vitiligenous lesion and it is completely absent in normal and perilesional skin.

Integrins, adhesion and apoptosis

Integrin-mediated adhesion to extracellular matrix proteins is required for survival of many cell types. This phenomenon appears to be a mechanism of tumour suppression and to participate in embryogenesis. Here, our current understanding of how integrin-dependent signals prevent apoptosis and implications of anchorage-dependent survival for development, physiology and pathology are discussed.

New insights into the kinetic resistance to anticancer agents

Kinetic resistance plays a major role in the failure of chemotherapy towards many solid tumors. Kinetic resistance to cytotoxic drugs can be reproduced in vitro by growing the cells as multicellular spheroids (Multicellular Resistance) or as hyperconfluent cultures (Confluence-Dependent Resistance). Recent findings on the cell cycle regulation have permitted a better understanding why cancer cells which arrest in long quiescent phases are poorly sensitive to cell-cycle specific anticancer drugs. Two cyclin-dependent kinase inhibitors (CDKI) seem particularly involved in the cell cycle arrest at the G1 to S transition checkpoint: the p53-dependent p21(cip1) protein which is activated by DNA damage and the p27(kip1) which is a mediator of the contact inhibition signal. Cell quiescence could alter drug-induced apoptosis which is partly dependent on an active progression in the cell cycle and which is facilitated by overexpression of oncogenes such as c-Myc or cyclins. Investigations are yet necessary to determine the influence of the cell cycle on the balance between antagonizing (bcl-2, bcl-X(L)...) or stimulating (Bax, Bcl-X(S), Fas...) factors in chemotherapy-induced apoptosis. Quiescent cells could also be protected from toxic agents by an enhanced expression of stress proteins, such as HSP27 which is induced by confluence. New strategies are required to circumvent kinetic resistance of solid tumors: adequate choice of anticancer agents whose activity is not altered by quiescence (radiation, cisplatin), recruitment from G1 to S/G2 phases by cell pretreatment with alkylating drugs or attenuation of CDKI activity by specific inhibitors.

Efeito das células do cumulus e cisteamina durante o cultivo de maturação in vitro de oócitos bovinos sobre a maturação nuclear e aquisição da competência para desenvolvimento embrionário

Complexos cumulus-oócito (COC), oócitos desnudos (DO) e DO cocultivados com células do cumulus em suspensão (DO+CC) foram maturados in vitro (MIV) na presença ou ausência de cisteamina (50mM). Observou-se efeito benéfico da cisteamina durante o cultivo de MIV, pois a maturação nuclear no grupo COC cisteamina foi maior do que a do COC controle (P<0,05). No grupo sem a adição de cisteamina, foi observado que a ausência de CC durante o cultivo de MIV prejudicou a maturação nuclear em DO, em relação ao COC (P<0,05), todavia a cisteamina restaurou a capacidade de progressão da meiose em DO, tornando-os semelhantes aos COC (P>0,05). O acoplamento entre oócitos e CC durante MIV demonstrou ser essencial para aquisição da competência do oócito para suportar o desenvolvimento embrionário inicial, pois COC apresentaram maior porcentagem de blastocistos e eclosão quando comparados a DO e DO+CC (P<0,05). A inclusão de cisteamina no cultivo de MIV não restaurou a aquisição da competência em DO e DO+CC, que permaneceram semelhantes aos do grupo-controle (P>0,05). Conclui-se que a cisteamina no meio de MIV melhora as taxas de maturação nuclear em COC e restaura a capacidade de progressão da meiose em DO. Todavia, na concentração utilizada neste estudo, não promove efeito benéfico no desenvolvimento embrionário.

Epigenetic regulation of cellular adhesion in cancer

Epigenetics describes the development and maintenance of stable heritable gene expression patterns, which allow cells to show different phenotypes despite of a commonly shared genetic code. The increasing knowledge in this field during the last decades reveals its importance for many physiological processes like differentiation, embryogenesis and parental imprinting, but also for some diseases such as cancer. Recent data have shown that the complexity of carcinogenesis can no longer be explained solely on the basis of genetic changes, but epigenomic alterations such as changes of the DNA methylation pattern and/or post-translational histone modifications and changes of microRNA expression need to be equally considered. Such epigenetic alterations may cause permanent changes in gene expression patterns and may therefore essentially contribute to some of the known phenotypic characteristics of cancer cells like the loss of growth control, altered intercellular communication and enhanced motility. The two latter may essentially be associated with the downregulation of cellular adhesion molecules, which may therefore be relevant in the context of cancer invasiveness and prognosis. The targeted modification of the epigenome may therefore open new horizons within the increasingly important field of epigenetic therapeutics-particularly in view of the regulation of cellular adhesion with particular attention to tumor cell invasion and metastasis.

Fuchs endothelial corneal dystrophy

Fuchs endothelial corneal dystrophy (FECD) is characterized by progressive loss of corneal endothelial cells, thickening of Descement's membrane and deposition of extracellular matrix in the form of guttae. When the number of endothelial cells becomes critically low, the cornea swells and causes loss of vision. The clinical course of FECD usually spans 10-20 years. Corneal transplantation is currently the only modality used to restore vision. Over the last several decades genetic studies have detected several genes, as well as areas of chromosomal loci associated with the disease. Proteomic studies have given rise to several hypotheses regarding the pathogenesis of FECD. This review expands upon the recent findings from proteomic and genetic studies and builds upon recent advances in understanding the causes of this common corneal disorder.

3-Dimensional cell culture for on-chip differentiation of stem cells in embryoid body

This paper proposes a microfluidic device for the on-chip differentiation of an embryoid body (EB) formed in a microwell via 3-dimensional cultures of mouse embryonic carcinoma (EC) cells. The device adjusted the size of the EB by fluid volume, differentiated the EB by chemical treatment, and evaluated its effects in EC cells by on-chip immunostaining. A microfluidic resistance network was designed to control the size of the embryoid body. The duration time and flow rate into each microwell regulated the initial number of trapped cells in order to adjust the size of the EB. The docked cells were aggregated and formed a spherical EB on the non-adherent surface of the culture chip for 3 days. The EC cells in the EB were then differentiated into diverse cell lineages without attachment for an additional 4 days; meanwhile, retinoic acid (RA) was applied without serum to direct the cells into early neuronal lineage. On-chip immunostaining of the EB in the microwell with a neuronal marker was conducted to assess the differentiation-inducing ability of RA. The effect of RA on neuronal differentiation was analyzed with confocal microscopic images of the TuJ1 marker. The RA-treated cells expressed more neuronal markers and appeared as mature neuronal cells with long neurites. The fluorescence intensity of the TuJ1 in the RA-treated EB was twice that observed in the non-treated EB on day 5. It was demonstrated that the pre-screening of inducing chemicals on the early neuronal differentiation of EC cells in a single microfluidic chip was indeed feasible. This chip is expected to constitute a useful tool for assessing the early differentiation of ES cells without attachment, and is also expected to prove useful as an anti-cancer drug test platform for the cytotoxicity assay with cellular spheroids.

Jaagsiekte sheep retrovirus transformation in Madin-Darby canine kidney epithelial cell three-dimensional culture

Jaagsiekte sheep retrovirus (JSRV) is the causative agent of a contagious lung cancer in sheep that shares similarities with human bronchioloalveolar carcinoma (BAC). JSRV is unique because the envelope gene (env) is the oncogene, as it can transform cells in culture and induce tumors in animals. The phosphatidylinositol 3-kinase (PI3K)-Akt-mTOR and H/N-Ras-MEK-mitogen-activated protein kinase (MAPK) pathways have been shown to be critical for Env transformation. However, the question still remains of how disruption of these pathways relates to tumor formation. To address this, JSRV Env transformation was studied in the context of epithelial structure, using the polarized Madin-Darby canine kidney (MDCK) epithelial cell three-dimensional (3-D) culture system. The results indicated that JSRV Env-transformed MDCK cells were larger and had full or multiple lumens, in contrast to the single lumens observed in controls. The altered phenotype was largely mediated by an increase in proliferation, in addition to overcoming the proliferative suppression signal. JSRV Env was not found to disrupt polarity or tight junctions or to inhibit lumen apoptosis. The PI3K-Akt-mTOR pathway was important for Env transformation in MDCK cells, although the mechanisms of action differed in 3-D and monolayer cultures. PI3K-dependent signaling to mTOR occurred in monolayers, while PI3K-independent signaling to mTOR occurred in 3-D culture. In contrast, the H/N-Ras-MEK-MAPK pathway was found to be inhibitory to transformation in both normal and transformed MDCK cells in 3-D culture. However, in monolayer culture, inhibition of MEK reverted the transformed phenotype, suggesting a different mechanism(s) of action in monolayer versus 3-D culture.

RGD-labeled USPIO inhibits adhesion and endocytotic activity of alpha v beta3-integrin-expressing glioma cells and only accumulates in the vascular tumor compartment

PURPOSE

To investigate the biologic effect of arginine-glycine-aspartic acid (RGD)-labeled ultrasmall superparamagnetic iron oxide (USPIO) (referred to as RGD-USPIO) on human umbilical vein endothelial cells (HUVECs), ovarian carcinoma (MLS) cells, and glioblastoma (U87MG) cells and on U87MG xenografts in vivo.

MATERIALS AND METHODS

All experiments were approved by the governmental review committee on animal care.USPIOs were coated with integrin-specific (RGD) or unspecific (arginine-alanine-aspartic acid [RAD]) peptides. USPIO uptake in HUVECs, MLS cells, and U87MG cells and in U87MG tumor xenografts was determined with T2 magnetic resonance (MR) relaxometry in 16 nude mice. Cells and tumors were characterized by using immunofluorescence microscopy. Trypan blue staining and lactate dehydrogenase assay were used to assess cytotoxicity. Statistical evaluation was performed by using a Mann-Whitney test or a linear mixed model with random intercept for the comparison of data from different experiments. Post hoc pairwise comparisons were adjusted according to a Tukey test.

RESULTS

HUVECs and MLS cells internalized RGD-USPIOs significantly more than unspecific probes. Controversially, U87MG cells accumulated RGD-USPIOs to a lesser extent than USPIO. Furthermore, only in U87MG cells, free RGD and alpha(v)beta(3) integrin-blocking antibodies strongly reduced endocytosis of nonspecific USPIOs. This was accompanied by a loss of cadherin-dependent intercellular contacts, which could not be attributed to cell damage. In U87MG tumors, RGD-USPIO accumulated exclusively at the neovasculature but not within tumor cells. The vascular accumulation of RGD-USPIO caused significantly higher changes of the R2 relaxation rate of tumors than observed for USPIO.

CONCLUSION

In glioma cells with unstable intercellular contacts, inhibition of alpha(v)beta(3) integrins by antibodies and RGD and RGD-USPIO disintegrated intercellular contacts and reduced endocytotic activity, illustrating the risk of inducing biologic effects by using molecular MR probes.

Down-regulation of alphav integrin by retroviral delivery of small interfering RNA reduces multicellular resistance of HT29

Since multicellular resistance (MCR) has been shown to be as adhesion-dependent, the role of alphav integrin in MCR of HT29 was investigated in this paper. Down-regulation of alphav integrin reduced MCR to oxaliplatin, but did not detectably change the drug sensitivity of monolayers. Down-regulation of alphav integrin decreased phosphorylated NF-kappaB p65 and increased phosphorylated JNK2 in multicellular spheroids. Cell-cell adhesion and cell-cell junctions in multicellular spheroids resembled the in vivo situation. Since force, including adhesion, can activate alphav integrin, cell-cell contact may contribute to activation of alphav integrin, through which increasing phosphorylated p65 and decreasing phosphorylated JNK2 takes part in MCR.

The behavior of rat tooth germ cells on poly(vinyl alcohol)

The purpose of this study was to evaluate the behaviors of rat tooth germ (TG) cells cultured on poly(vinyl alcohol) (PVA). It was found that TG cells suspended and aggregated to form three-dimensional spheroids on PVA. Compared with traditional monolayered cells on tissue culture polystyrene, TG cell spheroids on PVA obviously increased the alkaline phosphatase activity, the degree of mineralization, and upregulated both osteopontin and dentin matrix protein 1 genes, regardless of the seeding density. Surprisingly, PVA appears to activate the alkaline phosphatase activity and mineralization effects on TG cell spheroids in the absence of a differentiation medium. Furthermore, the present study indicates that integrins may play an important role in the mineralization on TG cell spheroids by adding Arg-Gly-Asp (RGD) peptides. Therefore, the information presented here should help to clarify the role of PVA in the regulation of the mineralization, differentiation and integrin-mediation of TG cells.

In vitro spheroid model of placental vasculogenesis: does it work?

Placental vascular development begins very early in pregnancy and is characterized by construction of a primitive vascular network in a low-oxygen environment. In vitro three-component assays of this process are scarce. In this study, a complex three-dimensional spheroid model for in vitro studies of placental vasculogenesis with regard to cell-cell interactions between cytotrophoblasts (CTs), villous stromal cells and endothelial precursor cells was established. Microscopic and immunohistochemical analyses of the spheroids showed structural and differentiation patterns resembling the structure and differentiation of early placental chorionic villous tissue (in regard to the expression of multiple markers cytokeratin-7, vimentin, CD34, CD31). The authenticity of this model to in vivo events allowed investigation of placental vascular development and trophoblast invasion under physiological and pathological conditions. Particularly enhanced spheroidal expression of SDF-1alpha and its receptor CXCR4, the major chemokine system in embryonic vasculogenesis, in a low-oxygen environment was detected. In addition, our model confirmed previously described invasive phenotype of trophoblasts through collagen under low- (physiologic), but not high- (pathologic) oxygen concentrations. Therefore, the three-dimensional spheroid model consisting of major placental cell types proved to be an appropriate system to investigate early placental vessel development under both physiological and pathological conditions.

Autocrine VEGF-A/KDR loop protects epithelial ovarian carcinoma cells from anoikis

Epithelial ovarian carcinoma (EOC) patients are usually diagnosed at an advanced stage, characterized by interperitoneal carcinomatosis and production of large volumes of ascites. Vascular endothelial growth factor-A (VEGF-A) and its main signaling receptor VEGFR2 (KDR) are coexpressed in primary ovarian tumors, ascitic cells and metastases, suggesting the existence of an autocrine VEGF-A/KDR loop in EOC cells. In the present study, we examined this possibility and explored the role of this autocrine loop in protecting EOC cells from apoptosis under anchorage free growth conditions (anoikis). We found that 3 different EOC cell lines (Caov3, OVCAR3, SKOV3) express both VEGF-A and its receptors, including KDR. In these cells, KDR is constitutively phosphorylated and is detected both in the cell plasma membrane and in the nucleus. Treating EOC cells with specific internal inhibitors of KDR kinase activity or a VEGF-A neutralizing antibody abolished KDR autophosphorylation and resulted in significant increase in apoptosis when cells were grown in single-cell, anchorage-free conditions. By contrast, these blocking reagents had no effect on cell viability when EOC cells were grown in adhesive monolayers. In summary, our results indicate that an autocrine VEGF-A/KDR loop exists in EOC cells and that it plays a role in protecting the cells from anoikis. Our results imply that treating EOC patients with VEGF blocking agents may potentially reduce peritoneal dissemination by decreasing vascular permeability as well as inducing apoptosis of shed ovarian cancer cells in ascites.

A study of death by anoikis in cultured epithelial cells

BACKGROUND

Epithelial cells are critically dependent upon cell-matrix and cell-cell adhesion for growth and survival. Anoikis is programmed cell death caused by disruption of cell-substrate adhesion in normal epithelial cells.

METHODS

We studied the induction of anoikis in vitro in two cell lines; HaCaT and SW742. PI3K, JAK2 and PKC are key elements in signalling pathways regulating cell survival, and using specific inhibitors we also examined their potential role in the induction of anoikis.

RESULTS

When prevented from adhesion by culture on polyHEMA, HaCaT cells underwent apoptosis selectively from the proliferating population; surviving cells underwent cell cycle arrest. In SW742 cells anoikis also occurred, but was balanced by increased cycling. The effects of specific kinase inhibitors indicated that both Janus kinase 2 and protein kinase C partially protect HaCaT cells from anoikis through inducing cell cycle arrest of surviving nonadherent cells; inhibition of Phosphatidylinositol 3-kinase did not induce cycling in HaCaTs prevented from adhesion but did stimulate anoikis. SW742 cells showed markedly different responses: Janus kinase 2 inhibition activated apoptosis directly, Phosphatidylinositol 3-kinase inhibition stimulated both cell cycling and apoptosis, while protein kinase C inhibition stimulated cycling but inhibited apoptosis.

CONCLUSIONS

Susceptibility to cell death in adhesion-prevented epithelial cells may thus be regulated by signalling pathways involving Phosphatidylinositol 3-kinase, Janus kinase 2 and protein kinase C. The ability of epithelial tumour cells to invade and metastasize may therefore result from disruption of these pathways.

Increased clusterin expression in Fuchs' endothelial dystrophy

PURPOSE

To investigate the differential expression of the glycoprotein clusterin/apoJ (CLU) in normal and Fuchs' endothelial dystrophy (FED) corneal endothelium and to compare the expression of various forms of CLU in normal and FED tissue.

METHODS

FED and pseudophakic bullous keratopathy (PBK) corneal buttons were removed during transplantation, and normal corneas were obtained from tissue banks. Human corneal endothelial cells and Descemet's membrane (HCEC-DM) complex was dissected from the stroma. Proteins were separated on 2-D gels and subjected to comparative proteomic analysis. Relative expression of presecretory CLU (pre-sCLU), secretory (s)CLU, and nuclear (n)CLU were compared between normal and FED HCEC-DM by Western blot analysis. Expression of CLU mRNA was compared by using RT-PCR. Subcellular localization of CLU was compared in corneal wholemounts from normal eyes and eyes with FED by immunocytochemistry followed by confocal microscopy.

RESULTS

Proteomic analysis revealed an apparent increase in CLU expression in FED HCEC-DM compared with the normal control. Western blot analysis demonstrated that pre-sCLU protein expression was 5.2 times higher in FED than in normal samples (P = 3.52E-05), whereas the mature form modified for secretion (sCLU) was not significantly elevated (P = 0.092). Expression of nCLU protein was significantly elevated in FED (P = 0.013). RT-PCR analysis revealed that CLU mRNA was significantly increased (P = 0.002) in FED samples, but not in PBK samples. CLU also had a distinctive localization in FED samples with enhanced intracellular staining around the guttae and in the nuclei of endothelial cells.

CONCLUSIONS

CLU expression is markedly elevated in FED-affected tissue, pointing to a yet undiscovered form of dysregulation of endothelial cell function involved in FED pathogenesis.

Prostaglandins and activation of AC/cAMP prevents anoikis in IEC-18

Recent data indicates that chronic inflammation of the intestine such as Crohn's or ulcerative colitis puts those individuals at heightened risk for colorectal adenocarcinoma. In this study, we examine the effect of the inflammatory mediator PGE(2) and associated signalling on detachment-induced cell death (anoikis) in intestinal epithelial cells. Treatment of detached IEC-18 with 0.01-0.05 microM PGE(2) increased cell viability as well as induced aggregation. As EP4 prostaglandin receptors on IEC are coupled to adenylate cyclase, we next treated cells with agents that promote cAMP signalling (Forskolin, dbcAMP, and etazolate), all of which promoted IEC aggregation as well as survival. We next treated detached IECs with specific inhibitors of adenylate cyclase or PKA, which accelerated anoikis. To explore the mechanism of cell-cell adhesion, we next treated detached IECs with an anti-E-cadherin blocking antibody which dispersed aggregates induced by dbcAMP, and an adenovirus expressing a dominant negative E-cadherin (EcadDeltaEC) prevented aggregate formation. Interestingly EcadDeltaEC prevented aggregation of IEC induced by dbcAMP but did not significantly reduce viability. This suggests that cAMP signalling is important in both aggregate formation and promoting viability but these are distinct events. Taken together, these data support a mechanism whereby elevated PGE(2) levels characteristic of colitis prevent anoikis by activating an AC-, cAMP-, and PKA-dependent signalling pathway. The delay of apoptosis by PGE(2) may be one mechanism by which inflammation may contribute to carcinogenesis.

Global gene expression analysis of early response to chemotherapy treatment in ovarian cancer spheroids

BACKGROUND

Chemotherapy (CT) resistance in ovarian cancer (OC) is broad and encompasses diverse unrelated drugs, suggesting more than one mechanism of resistance. To better understand the molecular mechanisms controlling the immediate response of OC cells to CT exposure, we have performed gene expression profiling in spheroid cultures derived from six OC cell lines (OVCAR3, SKOV3, TOV-112, TOV-21, OV-90 and TOV-155), following treatment with 10,0 microM cisplatin, 2,5 microM paclitaxel or 5,0 microM topotecan for 72 hours.

RESULTS

Exposure of OC spheroids to these CT drugs resulted in differential expression of genes associated with cell growth and proliferation, cellular assembly and organization, cell death, cell cycle control and cell signaling. Genes, functionally involved in DNA repair, DNA replication and cell cycle arrest were mostly overexpressed, while genes implicated in metabolism (especially lipid metabolism), signal transduction, immune and inflammatory response, transport, transcription regulation and protein biosynthesis, were commonly suppressed following all treatments. Cisplatin and topotecan treatments triggered similar alterations in gene and pathway expression patterns, while paclitaxel action was mainly associated with induction of genes and pathways linked to cellular assembly and organization (including numerous tubulin genes), cell death and protein synthesis. The microarray data were further confirmed by pathway and network analyses.

CONCLUSION

Most alterations in gene expression were directly related to mechanisms of the cytotoxics actions in OC spheroids. However, the induction of genes linked to mechanisms of DNA replication and repair in cisplatin- and topotecan-treated OC spheroids could be associated with immediate adaptive response to treatment. Similarly, overexpression of different tubulin genes upon exposure to paclitaxel could represent an early compensatory effect to this drug action. Finally, multicellular growth conditions that are known to alter gene expression (including cell adhesion and cytoskeleton organization), could substantially contribute in reducing the initial effectiveness of CT drugs in OC spheroids. Results described in this study underscore the potential of the microarray technology for unraveling the complex mechanisms of CT drugs actions in OC spheroids and early cellular response to treatment.

alpha6beta4 integrin activates Rac-dependent p21-activated kinase 1 to drive NF-kappaB-dependent resistance to apoptosis in 3D mammary acini

Malignant transformation and multidrug resistance are linked to resistance to apoptosis, yet the molecular mechanisms that mediate tumor survival remain poorly understood. Because the stroma can influence tumor behavior by regulating the tissue phenotype, we explored the role of extracellular matrix signaling and tissue organization in epithelial survival. We report that elevated (alpha6)beta4 integrin-dependent Rac-Pak1 signaling supports resistance to apoptosis in mammary acini by permitting stress-dependent activation of the p65 subunit of NF-kappaB through Pak1. We found that inhibiting Pak1 through expression of N17Rac or PID compromises NF-kappaB activation and renders mammary acini sensitive to death, but that resistance to apoptosis could be restored to these structures by overexpressing wild-type NF-kappaB p65. We also observed that acini expressing elevated levels of Pak1 can activate p65 and survive death treatments, even in the absence of activated Rac, yet will die if activation of NF-kappaB is simultaneously inhibited through expression of IkappaBalphaM. Thus, mammary tissues can resist apoptotic stimuli by activating NF-kappaB through alpha6beta4 integrin-dependent Rac-Pak1 signaling. Our data emphasize the importance of the extracellular matrix stroma in tissue survival and suggest that alpha6beta4 integrin-dependent Rac stimulation of Pak1 could be an important mechanism mediating apoptosis-resistance in some breast tumors.

Epithelial-Mesenchymal Transition and Colorectal Cancer: Gaining Insights into Tumor Progression Using LIM 1863 Cells

In addition to allowing epithelial cells to escape the structural constraints imposed by tissue architecture and adopt a phenotype more amenable to cell movement, it is now recognized that the epithelial-mesenchymal transition (EMT) may also represent a critical component permitting the progression of carcinomas towards invasive and metastatic disease. However, data supporting the actual occurrence of EMT in specific solid tumors and its relevance to the process of progression of these cancers has been scant. Despite an extensive knowledge of the genetic basis for colorectal cancer, the translation of this information into effective treatments has been limited. Clearly, there is a desperate need for new and improved therapies and since the switch to a metastatic phenotype is critical for outcome, it is of paramount importance to elucidate the biology that underlies the progression of this disease. Thus, the unique LIM 1863 model for studying the EMT of colorectal carcinoma has been used to both substantiate the importance of the transition for this cancer type and to identify molecular events that contribute to disease progression. Importantly, it has emerged that not only does EMT enhance migratory capacity, but also elicits additional selective advantages to colonic tumor cells. Specifically, the acquisition of autocrine growth factor signaling loops, mechanisms to evade apoptosis, and expression of specific integrins allowing invasive cells to interact with interstitial matrices and sustain activation of TGF-beta combine to provide a compelling new biochemical framework for understanding how EMT contributes to tumor evolution.

Proteomic Analysis of Alternative Protein Tyrosine Phosphorylation in 1,2-Dichlorovinyl-Cysteine-Induced Cytotoxicity in Primary Cultured Rat Renal Proximal Tubular Cells

Toxicant exposure affects the activity of various protein tyrosine kinases. Using phosphotyrosine proteomics, we identified proteins that were differentially phosphorylated before renal cell detachment and apoptosis. Treatment of primary cultured rat proximal tubular epithelial cells with the model nephrotoxicant S-(1,2-dichlorovinyl)-L-cysteine (DCVC) resulted in early reorganization of F-actin stress fibers and formation of lamellipodia, which was followed by cell detachment from the matrix and apoptosis. This was prevented by genistein-mediated inhibition of protein tyrosine kinases and enhanced by inhibition of protein tyrosine phosphatases using vanadate. Phosphotyrosine proteomics revealed that DCVC-induced renal cell apoptosis was preceded by changes in the tyrosine phosphorylation status of a subset of proteins, as identified by matrix-assisted laser desorption ionization/time of flight-mass spectrometry (MS)/MS including actin-related protein 2 (Arp2), cytokeratin 8, t-complex protein 1 (TCP-1), chaperone containing TCP-1, and gelsolin precursor. The major differentially tyrosine-phosphorylated protein was Arp2, whereas phosphorylation of Arp3 was not affected. Arp2 was located in the lamellipodia that were formed before the onset of apoptosis. Because DCVC-induced cell detachment and apoptosis is regulated by tyrosine kinases, we propose that alterations in tyrosine phosphorylation of a subset of proteins, including Arp2, play a role in the regulation of the F-actin reorganization and lamellipodia formation that precede renal cell apoptosis caused by nephrotoxicants.

Induction of apoptosis and transient increase of phosphorylated MAPKs by diallyl disulfide treatment in human nasopharyngeal carcinoma CNE2 cells

This study was undertaken to elucidate the effect of diallyl disulfide (DADS), an oil-soluble organosulfur compound found in garlic, in suppressing human nasopharyngeal carcinoma cells. A potent increase (of at least 9-fold) in apoptotic cells has accompanied 1) a decrease in cell viability, 2) a increase of the fraction of S-phase cells by up to 63.8%, and 3) a transient increase of the phospho-p38 and phospho-p42/44 (phosphorylated p38 MAPK and phosphorylated p42/44 MAPK) in a time- and concentration-dependent manner. These results indicate that DADS can induce apoptosis in human nasopharyngeal carcinoma cells via, at least partly, S-phase block of the cell cycle, related to a rise in MAPK phosphorylation.

Cytoskeleton reorganization and ultrastructural damage induced by gliadin in a three-dimensional in vitro model

AIM

To evaluate the interplay between gliadin and LoVo cells and the direct effect of gliadin on cytoskeletal patterns.

METHODS

We treated LoVo multicellular spheroids with digested bread wheat gliadin in order to investigate their morphology and ultrastructure (by means of light microscopy and scanning electron microscopy), and the effect of gliadin on actin (phalloidin fluorescence) and the tight-junction protein occludin and zonula occluden-1.

RESULTS

The treated spheroids had deep holes and surface blebs, whereas the controls were smoothly surfaced ovoids. The incubation of LoVo spheroids with gliadin decreased the number of intracellular actin filaments, impaired and disassembled the integrity of the tight-junction system.

CONCLUSION

Our data obtained from an "in vivo-like" polarized culture system confirm the direct noxious effect of gliadin on the cytoskeleton and tight junctions of epithelial cells. Unlike two-dimensional cell culture systems, the use of multicellular spheroids seems to provide a suitable model for studying cell-cell interactions.

Long term metabolic arrest and recovery of HEK293 spheroids involves NF-kappaB signaling and sustained JNK activation

Understanding how cells withstand a depletion of intracellular water is relevant to the study of longevity, aging, and quiescence because one consequence of air-drying is metabolic arrest. After removal of medium, HEK293 spheroids with intracellular water content of approximately 65% survived partial vacuum, with antistatic control, for weeks in the dark at 25 degrees C. In contrast, only a limited exposure of monolayers to air was lethal; the mitochondrion being a target of this stress. The pathways activated during the long-term arrest and recovery of spheroids depended on both NF-kappaB signaling and sustained JNK activation. A cyclical cascade, presumably originating from an intercellular stress signal, led to endogenous cytokine production (TNF-alpha, IL-1b, and IL-8) and propagation of the cellular stress signal through the co-activation of NF-kappaB and JNK. Increased levels of downstream pathway signaling members, specifically Gadd45beta, c-jun, and ATF3 were observed, as was activation of c-jun (phosphorylation). Activation of these pathways permit cells to survive long-term storage and recovery because chemical inhibition of both NF-kappaB nuclear translocation and JNK phosphorylation led to cell death. The capacity of an immortalized cell to enter, and then exit, a state of long-term quiescence, without genetic or chemical intervention, has implications for the study of cell transformation. In addition, the ability to monitor the relevant signaling pathways at endogenous levels, from effector to transcriptional regulator, emphasizes the utility of multicellular aggregate models in delineating stress response pathways.

Altered localization of p120 catenin during epithelial to mesenchymal transition of colon carcinoma is prognostic for aggressive disease

We examined the expression and localization of p120 catenin (p120ctn) as a consequence of the epithelial to mesenchymal transition (EMT) of highly differentiated colon carcinoma cells (LIM1863 cells). This unique line grows in suspension as spheroids and undergoes an EMT within 24 hours following stimulation with transforming growth factor-beta and tumor necrosis factor-alpha. Although p120ctn expression remains stable during the EMT, its localization shifts from cell-cell junctions to the cytoplasm. Interestingly, a marked decrease in RhoA activation coincident with E-cadherin loss occurs during the EMT and correlates with the formation of a p120ctn/RhoA complex. Use of RNA interference showed that p120ctn reduction results in increased RhoA activity and a significant decrease in the motility of post-EMT cells. To determine the relevance of these findings to colorectal cancer progression, we assessed p120ctn expression by immunohistochemistry in 557 primary tumors. Of note, we observed that 53% of tumors presented cytoplasmic staining for p120ctn, and statistical analysis revealed that this localization is predictive of poor patient outcome. Cytoplasmic p120ctn correlated with later-stage tumors, significantly reduced 5- and 10-year survival times and a greater propensity for metastasis to lymph nodes compared with junctional p120ctn. We also confirmed that altered localization of p120ctn corresponded with loss or cytoplasmic localization of E-cadherin. These alterations in E-cadherin are also associated with a significant reduction in patient survival time and an increase in tumor stage and lymph node metastasis. These data provide a compelling argument for the importance of both p120ctn and the EMT itself in the progression of colorectal carcinoma.

Non-angiogenic functions of VEGF in breast cancer

This review advances the hypothesis that the function of vascular endothelial growth factor (VEGF) in breast cancer is not limited to angiogenesis, and that VEGF signaling in breast carcinoma cells is important for the ability of these cells to evade apoptosis and progress towards invasive and metastatic disease. In other terms, VEGF signaling provides a selective advantage for the survival and dissemination of breast carcinoma cells that may be independent of angiogenesis. The key component of this hypothesis is that breast carcinoma cells express specific VEGF receptors and that these receptors respond to autocrine VEGF, resulting in the activation of signaling pathways that impede apoptosis and promote cell migration. A related hypothesis, which is developed in this review, is that the alpha6beta4 integrin, which has been implicated in the survival and motility of breast cancer cells, can stimulate the translation of VEGF mRNA and, consequently, autocrine VEGF signaling. These findings imply that VEGF and VEGF receptor-based therapeutics, in addition to targeting angiogenesis, may also target tumor cells directly.

A Causative Role of Stromelysin-3 in Extracellular Matrix Remodeling and Epithelial Apoptosis during Intestinal Metamorphosis in Xenopus laevis

The matrix metalloproteinases are a family of proteases capable of degrading various components of the extracellular matrix. Expression studies have implicated the involvement of the matrix metalloproteinase stromelysin-3 (ST3) in tissue remodeling and pathogenesis. However, the in vivo role of ST3 has been difficult to study because of a lack of good animal models. Here we used intestinal remodeling during thyroid hormone-dependent metamorphosis of Xenopus laevis as a model to investigate in vivo the role of ST3 during postembryonic organ development in vertebrates. We generated transgenic tadpoles expressing ST3 under control of a heat shock-inducible promoter. We showed for the first time in vivo that wild type ST3 but not a catalytically inactive mutant was sufficient to induce larval epithelial cell death and fibroblast activation, events that normally occur only in the presence of thyroid hormone. We further demonstrated that these changes in cell fate are associated with altered gene expression in the intestine and remodeling of the intestinal basal lamina. These results thus suggest that ST3 regulates cell fate and tissue morphogenesis through direct or indirect ECM remodeling.

Hypoxia stimulates carcinoma invasion by stabilizing microtubules and promoting the Rab11 trafficking of the alpha6beta4 integrin

Hypoxia plays a key role in tumor cell survival, invasion, and metastasis. Here we show that hypoxia increases tumor cell invasion by the modulation of Rab11, an important molecule for vesicular trafficking, especially membrane protein recycling and translocation of proteins from trans-Golgi network to plasma membrane. Dominant-negative Rab11 dramatically decreased hypoxia-induced invasion of MDA-MB-231 breast carcinoma cells without affecting cell apoptosis. Hypoxia-induced Rab11 trafficking is regulated by microtubule stability, as evidenced by the findings that hypoxia increases Glu tubulin and that colchicine blocks Rab11 trafficking and invasion. Inhibition of GSK-3beta activity by hypoxia seems to be central to microtubule stabilization and invasion. In fact, expression of a dominant-negative GSK-3beta was sufficient to stimulate invasion in normoxia. One target of Rab11-mediated trafficking that contributes to invasion is the integrin alpha6beta4. Hypoxia induced a significant increase in alpha6beta4 surface expression but it had no effect on the surface expression of alpha3beta1. This increase is dependent on Rab11 and stable microtubules. In summary, we identify vesicle trafficking as a novel target of hypoxic stimulation that is important for tumor invasion.

Transcriptional activation of integrin beta6 during the epithelial-mesenchymal transition defines a novel prognostic indicator of aggressive colon carcinoma

We used a spheroid model of colon carcinoma to analyze integrin dynamics as a function of the epithelial-mesenchymal transition (EMT), a process that provides a paradigm for understanding how carcinoma cells acquire a more aggressive phenotype. This EMT involves transcriptional activation of the beta6 integrin subunit and a consequent induction of alphavbeta6 expression. This integrin enhances the tumorigenic properties of colon carcinoma, including activation of autocrine TGF-beta and migration on interstitial fibronectin. Importantly, this study validates the clinical relevance of the EMT. Kaplan-Meier analysis of beta6 expression in 488 colorectal carcinomas revealed a striking reduction in median survival time of patients with high beta6 expression. Elevated receptor expression did not simply reflect increasing tumor stage, since log-rank analysis showed a more significant impact on the survival of patients with early-stage, as opposed to late-stage, disease. Cox regression analysis confirmed that this integrin is an independent variable for these tumors. These findings define the alphavbeta6 integrin as an important risk factor for early-stage disease and a novel therapeutic candidate for colorectal cancer.