Finite proliferative lifespan in vitro of a human breast cancer cell strain isolated from a metastatic lymph node

We recently described culture conditions that allow proliferation of metastatic human breast cancer cells from biopsy specimens of certain patient samples. These conditions resulted in the development of an immortalized cell strain designated SUM-44PE. These same culture conditions were used to isolate a human breast cancer cell strain from a metastatic lymph node of a separate breast cancer patient. The SUM-16LN human breast cancer cells isolated from this specimen were cultured either in serum-free medium or serum-containing medium supplemented with insulin and hydrocortisone. Unlike the SUM-44PE cells that have proliferated in culture continuously for over two years, SUM-16LN cells proliferated in culture for approximately 200 days and underwent 15 to 20 population doublings before undergoing cell senescence. No cells of this strain proliferated beyond passage 8. SUM-16LN cells were keratin-19 positive and had an aneuploid karyotype. These cells overexpressed p53 protein and had an amplified epidermal growth factor (EGF) receptor gene that resulted in high level expression of tyrosine phosphorylated EGF receptor protein. Despite the presence of high levels of tyrosine phosphorylated EGF receptor in these cells, they proliferated in serum-free, EGF-free medium and did not secrete detectable levels of EGF-like mitogenic growth factor. In addition, these cells were potently growth inhibited by all concentrations of exogenous EGF tested and by the neutralizing EGF receptor antibody Mab 425. These results suggest that the high level of tyrosine phosphorylated EGF receptor present in these cells is the direct result of receptor overexpression and not the result of the presence of a simulatory ligand. Thus, SUM-16LN represents a human breast cancer cell strain that exhibited genetic and cellular characteristics of advanced human breast cancer cells. Nevertheless, these cells exhibited a finite proliferative lifespan in culture, suggesting that cellular immortalization is not a phenotype expressed by all human breast cancer cells.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44199/1/10549_2004_Article_BF00666588.pd

Analytic Metaphysics versus Naturalized Metaphysics: The Relevance of Applied Ontology

The relevance of analytic metaphysics has come under criticism: Ladyman & Ross, for instance, have suggested do discontinue the field. French & McKenzie have argued in defense of analytic metaphysics that it develops tools that could turn out to be useful for philosophy of physics. In this article, we show first that this heuristic defense of metaphysics can be extended to the scientific field of applied ontology, which uses constructs from analytic metaphysics. Second, we elaborate on a parallel by French & McKenzie between mathematics and metaphysics to show that the whole field of analytic metaphysics, being useful not only for philosophy but also for science, should continue to exist as a largely autonomous field

The influence of growth factors on the proliferative potential of normal and primary breast cancer-derived human breast epithelial cells

In previous studies, we developed serum-free, bovine pituitary extract (BPE)-free culture conditions for the growth of normal and neoplastic rat mammary epithelial cells. The present studies were aimed at determining if these culture methods could be used to study the influence of specific growth factors on the proliferative potential of normal human mammary epithelial (HME) cells and cells derived from human breast cancer (HBC) specimens. Our results indicate that normal HME cells in primary culture express stringent requirements for insulin (IN), epidermal growth factor (EGF), and cholera toxin (CT). Of these factors, EGF is most important, with essentially no proliferation taking place in the absence of this factor. By contrast, when cells are grown in serum-free primary culture in the presence of a full complement of growth factors and then subcultured, growth in secondary culture is not influenced by the removal of individual growth factors. Growth in secondary culture in the absence of EGF is mediated by autocrine factors secreted by the cells. However, there is no evidence for autocrine activity that mediates growth in the absence of IN in secondary cultures. Primary culture of HBC cells in serum-free, BPE-free medium revealed two patterns of growth factor requirements. One set of HBC cells expressed identical requirements for IN and EGF in primary culture as normal cells. Likewise, these cells grew in secondary culture in the absence of either factor. The second set of tumors expressed independence of IN for growth in primary culture. These cells grew to confluence in primary culture in the absence of IN and could be subcultured in this medium. All tumor cells examined expressed a requirement for EGF for primary culture growth, whereas none of the HBC cells examined expressed a significant CT requirement. In many cases, growth in the absence of CT exceeded that observed in its presence. Thus, our culture system allows analysis of the growth factor requirements of HME and HBC cells in primary culture. Our results indicate significant differences between HME and HBC cells in this regard. However, the results of secondary culture experiments indicate that the growth factor milieu from which cells are taken can have a profound effect on the requirements for growth factors in culture.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44196/1/10549_2005_Article_BF01806371.pd

Multiple growth factor independence in rat mammary carcinoma cells

In previous studies we demonstrated that rat mammary tumor (RMT) cells that are serially transplantable consist of cells that are independent of growth factors strictly required by normal rat mammary epithelial (RME) cells for growth in serum-free culture. The present studies were designed to determine the extent of the growth factor independence of several cell lines derived from these tumors and to determine if the cells that expressed growth factor independence in vitro are also tumorigenic in vivo . Cells from a transplantable mammary carcinoma (8–12 RMT) were seeded into culture in serum-free medium in the absence of either insulin (IN), epidermal growth factor (EGF), or cholera toxin (CT), and cell populations independent of the individual factors were developed. Next, the three growth factor independent populations were tested for their ability to grow in the absence of multiple growth factors. 8–12 RMT cells did not lose proliferative potential when multiple growth factors were deleted from the medium. Indeed, 8–12 RMT cells could be serially propagated in serum-free medium supplemented solely with bovine serum albumin (BSA) and ethanolamine. Cell lines independent of single growth factors were also developed from two other transplantable tumors (1–9 RMT and 7–15 RMT). In contrast to the 8–12 RMT-derived cell lines, deletion of additional growth factors from the media of the 1–9 RMT and 7–15 RMT-derived cells resulted in dramatic losses in growth potential. These results suggest that independence of individual growth factors is mediated by different mechanisms, since cells from different tumors can stably express independence of one, two, or three or more factors. Examination of conditioned media of four different RMT cell lines indicates that independence of EGF is mediated by autocrine factors. By contrast, there is no evidence for an autocrine factor that mediates independence of insulin-like growth factors. Thus, cell lines derived from serially transplantable RMTs are independent of either single or multiple growth factors, and independence of individual growth factors appears to be mediated by separate mechanisms.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44197/1/10549_2005_Article_BF01980969.pd

Links between maternal postpartum depressive symptoms, maternal distress, infant gender and sensitivity in a high-risk population

<p>Abstract</p> <p>Background</p> <p>Maternal postpartum depression has an impact on mother-infant interaction. Mothers with depression display less positive affect and sensitivity in interaction with their infants compared to non-depressed mothers. Depressed women also show more signs of distress and difficulties adjusting to their role as mothers than non-depressed women. In addition, depressive mothers are reported to be affectively more negative with their sons than with daughters.</p> <p>Methods</p> <p>A non-clinical sample of 106 mother-infant dyads at psychosocial risk (poverty, alcohol or drug abuse, lack of social support, teenage mothers and maternal psychic disorder) was investigated with EPDS (maternal postpartum depressive symptoms), the CARE-Index (maternal sensitivity in a dyadic context) and PSI-SF (maternal distress). The baseline data were collected when the babies had reached 19 weeks of age.</p> <p>Results</p> <p>A hierarchical regression analysis yielded a highly significant relation between the PSI-SF subscale "parental distress" and the EPDS total score, accounting for 55% of the variance in the EPDS. The other variables did not significantly predict the severity of depressive symptoms. A two-way ANOVA with "infant gender" and "maternal postpartum depressive symptoms" showed no interaction effect on maternal sensitivity.</p> <p>Conclusions</p> <p>Depressive symptoms and maternal sensitivity were not linked. It is likely that we could not find any relation between both variables due to different measuring methods (self-reporting and observation). Maternal distress was strongly related to maternal depressive symptoms, probably due to the generally increased burden in the sample, and contributed to 55% of the variance of postpartum depressive symptoms.</p

The Coordination of Leaf Photosynthesis Links C and N Fluxes in C3 Plant Species

Photosynthetic capacity is one of the most sensitive parameters in vegetation models and its relationship to leaf nitrogen content links the carbon and nitrogen cycles. Process understanding for reliably predicting photosynthetic capacity is still missing. To advance this understanding we have tested across C3 plant species the coordination hypothesis, which assumes nitrogen allocation to photosynthetic processes such that photosynthesis tends to be co-limited by ribulose-1,5-bisphosphate (RuBP) carboxylation and regeneration. The coordination hypothesis yields an analytical solution to predict photosynthetic capacity and calculate area-based leaf nitrogen content (Na). The resulting model linking leaf photosynthesis, stomata conductance and nitrogen investment provides testable hypotheses about the physiological regulation of these processes. Based on a dataset of 293 observations for 31 species grown under a range of environmental conditions, we confirm the coordination hypothesis: under mean environmental conditions experienced by leaves during the preceding month, RuBP carboxylation equals RuBP regeneration. We identify three key parameters for photosynthetic coordination: specific leaf area and two photosynthetic traits (k3, which modulates N investment and is the ratio of RuBP carboxylation/oxygenation capacity () to leaf photosynthetic N content (Npa); and Jfac, which modulates photosynthesis for a given k3 and is the ratio of RuBP regeneration capacity (Jmax) to). With species-specific parameter values of SLA, k3 and Jfac, our leaf photosynthesis coordination model accounts for 93% of the total variance in Na across species and environmental conditions. A calibration by plant functional type of k3 and Jfac still leads to accurate model prediction of Na, while SLA calibration is essentially required at species level. Observed variations in k3 and Jfac are partly explained by environmental and phylogenetic constraints, while SLA variation is partly explained by phylogeny. These results open a new avenue for predicting photosynthetic capacity and leaf nitrogen content in vegetation models

Choosing the right cell line for breast cancer research

Breast cancer is a complex and heterogeneous disease. Gene expression profiling has contributed significantly to our understanding of this heterogeneity at a molecular level, refining taxonomy based on simple measures such as histological type, tumour grade, lymph node status and the presence of predictive markers like oestrogen receptor and human epidermal growth factor receptor 2 (HER2) to a more sophisticated classification comprising luminal A, luminal B, basal-like, HER2-positive and normal subgroups. In the laboratory, breast cancer is often modelled using established cell lines. In the present review we discuss some of the issues surrounding the use of breast cancer cell lines as experimental models, in light of these revised clinical classifications, and put forward suggestions for improving their use in translational breast cancer research

Exploiting Fast-Variables to Understand Population Dynamics and Evolution

We describe a continuous-time modelling framework for biological population dynamics that accounts for demographic noise. In the spirit of the methodology used by statistical physicists, transitions between the states of the system are caused by individual events while the dynamics are described in terms of the time-evolution of a probability density function. In general, the application of the diffusion approximation still leaves a description that is quite complex. However, in many biological applications one or more of the processes happen slowly relative to the system's other processes, and the dynamics can be approximated as occurring within a slow low-dimensional subspace. We review these time-scale separation arguments and analyse the more simple stochastic dynamics that result in a number of cases. We stress that it is important to retain the demographic noise derived in this way, and emphasise this point by showing that it can alter the direction of selection compared to the prediction made from an analysis of the corresponding deterministic model.Comment: 33 pages, 9 figure

Bioinformatics and molecular modeling in glycobiology

The field of glycobiology is concerned with the study of the structure, properties, and biological functions of the family of biomolecules called carbohydrates. Bioinformatics for glycobiology is a particularly challenging field, because carbohydrates exhibit a high structural diversity and their chains are often branched. Significant improvements in experimental analytical methods over recent years have led to a tremendous increase in the amount of carbohydrate structure data generated. Consequently, the availability of databases and tools to store, retrieve and analyze these data in an efficient way is of fundamental importance to progress in glycobiology. In this review, the various graphical representations and sequence formats of carbohydrates are introduced, and an overview of newly developed databases, the latest developments in sequence alignment and data mining, and tools to support experimental glycan analysis are presented. Finally, the field of structural glycoinformatics and molecular modeling of carbohydrates, glycoproteins, and protein–carbohydrate interaction are reviewed