510 research outputs found
Glycobiological Regulation of Breast Cancer Invasion
No full textInvasiveness of cancer is the predominant reason behind mortality associated with the disease. Although long under active investigation, fundamental aspects of the early steps of cancer invasion and metastasis are still poorly understood. One such aspect, the aberrant expression of glycans and their binding proteins (lectins), is among the earliest-demonstrated and pervasive hallmarks of malignant transformation, the consequences of which remain elusive. In this thesis, two glycopathological questions relating to breast cancer progression are investigated.
In the first problem, evidence is presented for heterogeneity of a specific glycan linkage: α2,6-linked sialic acids within breast cancer epithelia. Upon sorting out two populations with moderate- and relatively higher- cell surface expression of α2,6-linked sialic acids, from the triple negative breast cancer cell line MDA-MB-231, both populations (denoted as medium- and high- 2,6-Sial cells respectively) are shown to stably retain their levels in early passages. The medium 2,6-Sial cells shows greater plasticity (recapitulating eventually the heterogeneity of the unsorted population), and higher adhesion to, and invasion through, ECM, than the high 2,6-Sial cells. The expression of 2,6-Sial and the associated phenotypes is shown to be dependent on the expression of a specific glycosyltransferase, ST6GAL1. The differential adhesion between the two populations is proposed to have consequences for the ‘unjamming’ transition and localization of medium 2,6-Sial cells to the edge of growing tumoroid-like cultures. Notwithstanding the dynamics of cell-surface α2,6-linked sialic acids, an intriguing localization of α2,3-linked sialic acids is observed in the ECM proximal to breast cancer cells.
In the second problem, the role of Galectin-9 (GAL-9) in breast cancer invasion is investigated. A member of the tandem-repeat (having two distinct carbohydrate recognition domains (bi-CRD)) class of galectins, mRNA levels of GAL-9 are shown to be elevated in invasive breast cancer cell lines and the protein is elevated in tumor epithelia from sections of patients with breast cancer. Perturbing GAL-9 levels is shown to correlate with the adhesion and invasion of
cancer epithelia to, and through, ECM, respectively. Intriguingly, the consequences of GAL-9 on invasion is observed to be dependent on its cleavage to monoCRD galectins with the N-CRD fragment (but not C-CRD fragment) able to phenocopy the effects of the full-length counterpart.
Taken together, the above observations add an unexplored (glycobiological) dimension to the interactions between cancer cells and their surrounding ECM, enriching our understanding of how the tumor microenvironment contributes to cancer progression
A study of extracellular matrix dynamics in epithelial cancer progression with a special focus on ovarian cancer spheroidogenesis
No full textEpithelial ovarian cancer (EOC) is one of the most debilitating gynecological cancers in women worldwide due to its insidious symptoms. The predominant subtype of ovarian cancer: high-grade serous ovarian carcinoma (HGSOC), is responsible for 75% of all fatalities associated with EOC. 90% of EOC patients have already reached an advanced stage of metastasis when they are diagnosed with the disease. Metastasis is frequently associated with ascites: an abnormal accumulation of fluid in the peritoneal cavity due to the occurrence of spheroids, clusters of disseminated malignant EOC cells. Spheroids contribute significantly to the morbidity and mortality associated with EOC. Despite this, the mechanisms associated with the formation of EOC spheroids are ill-understood.
Investigations indicate intricate connections between these signaling modules with elements of reciprocal and hierarchical connections that underlie spheroidal morphogenesis and may provide insights into the identification of targets for future therapeutic strategies for EOC
Food for nought
No full textThe short story, "Food for nought", is written by the listed author above, Shashi Bhat. Now in its 48th year, Best Canadian Stories has long championed the short story form and highlighted the work of many of the writers, throughout their respective careers, who have gone on to shape the Canadian literary canon. Caroline Adderson, Margaret Atwood, Clark Blaise, Lynn Coady, Mavis Gallant, Zsuzsi Gartner, Douglas Glover, Steven Heighton, Isabel Huggan, Mark Anthony Jarman, Norman Levine, Rohinton Mistry, Alice Munro, Leon Rooke, Diane Schoemperlen, Russell Smith, Linda Svendsen, Kathleen Winter, and many others have appeared in its pages over the years and decades, making Best Canadian Stories the go-to source for what’s new in Canadian fiction writing for close to five decades. A continuation of not only a series, but a legacy in Canadian letters. --From publisher description.Published
Investigating the role of AMPK in mammary gland alveologenesis and lactation
No full textAMP-activated kinase (AMPK) is an energy sensor that regulates cell growth and metabolism. Reports from our laboratory and others have shown the context-specific role of AMPK signaling in breast cancer. However, its role in normal mammary gland growth and function is unclear. Here, we showed that AMPK expression and activity within murine mammary epithelia increased from puberty to pregnancy, reaching its highest levels during lactation, and then declined post-lactation. Further, induction of prolactin (PRL) signaling increased AMPK expression and activity in ex vivo organotypic cultures of mammary epithelial cells (MECs), whereas PRL failed to do so in 2D monolayer culture of MECs. To understand the role of AMPK in mammary gland morphogenesis in vivo, we generated mice with conditional knockout of the catalytic AMPK isoforms 1 and 2 (AMPK⍺1,⍺2 homo cDKO) in mammary gland. Whole mount analysis of AMPK⍺1,⍺2 homo cDKO mammary glands demonstrated precocious alveolar development with increased epithelial content due to enhanced proliferation and altered differentiation. This was corroborated by ex vivo organotypic cultures wherein pharmacological inhibition of AMPK in primary MECs led to the formation of bigger acini with a significantly increased number of cells AMPK⍺1,⍺2 homo cDKO mice also showed increased beta-casein expression with significantly increased pups’ weight when compared with wild-type control mice. Interestingly, AMPK⍺1,⍺2 homo cDKO epithelia showed increased phosphorylated STAT5 which is known to drive alveologenesis downstream of PRL signaling, suggesting a negative correlation between the two pathways. Interestingly, Akt inhibition led to reversal of phenotype in AMPK⍺1,⍺2 homo cDKO MECs cultured in 3D LrECM, demonstrating a negative cross talk between AMPK and Akt in maintaining cellular homeostasis during alveolar morphogenesis. Our study thus identifies a novel interplay between AMPK and Akt that determines mammary alveologenesis and differentiation through PRL-JAK2-STAT5 signaling
Deploying an Orthogonal Turn for Isolation of Rare Cell Populations from Vascular Environments
No full textCancer cells are shed from metastatic primary tumors, bearing the potential for blood-borne metastasis to distant vital organs. Metastasis is predominantly responsible for cancer-related deaths. These circulating tumor cells (also known as CTCs) are highly invasive and can be present in the vasculature as single cells or as clusters. CTCs have been proposed as an important biomarker to assess the aggressiveness of cancer, the effectiveness of the treatment, and disease progression. Although most of the cells have epithelial receptors on their surface, such as Epithelial Cell Adhesion Molecules (EpCAMs), the molecular diversity on the surfaces of such cells is still not completely characterized. The circulating tumor cells (or CTCs) tend to be larger in size and higher in density with respect to the rest of the blood cells and in their density. CTCs are extraordinarily rare, i.e., one among a billion blood cells which make their isolation difficult.
Existing technologies carry out CTC separation by either inducing external forces (active separation) or using intrinsic hydrodynamic forces (passive separation). In active separation, the external forces have to be larger than the flow-induced forces, which results in a limited throughput. Moreover, these techniques often involve biomarkers and labelling agents (usually EpCAM antibodies), which not only puts a question on the viability of the captured cells but also might fail to work for CTCs that do not express such markers. The passive separation method is carried out by simply controlling the hydrodynamic properties of the flow. Of these, inertial microfluidics separation has high throughput, whereby large sample volumes can be processed in a short time. High throughput vortex trapping and CTC separation has been described by Di Carlo et al. in their vortex-chip technology. However, the operation of their device requires drastically high flow velocities (particle velocity ̴ 4 m/s), which are prone to damage the cells and affect their viability.
In this dissertation, an inertial microfluidic vortex chip incorporating an orthogonal turn is investigated for the isolation and separation of CTCs. These chips function at significantly lower (38% of previously reported) flow velocities. Fluid flowing through the chip is constrained to exit the trapping chamber at right angles to that of its entry. Such a flow configuration leads to the formation of a vortex in the chamber and above a critical flow velocity, larger particles are trapped in the vortex, whereas smaller particles get ejected with the flow: we call this phenomenon the turn-effect.
I explain how different forces contribute to the turn-effect in the orthogonal design by acting on cells, and pushing them into specific vortices in a size- and velocity-dependent fashion. Furthermore, we have characterized the critical velocities for trapping particles of different sizes on chips with distinct entry-exit configurations. Optimal architectures for stable vortex trapping at low flow velocities are identified using polystyrene beads and blood cells.
Subsequently, I demonstrated selective trapping of human breast cancer cells mixed with whole blood at low concentrations. An isolation protocol to separate the trapped particles was developed and optimized on a scaled-up device that uses serialization and parallelization. After isolating spiked circulating cancer cells from diluted blood, we were also able to culture them.
In summary, a label-free inertial microfluidic vortex trapping setup incorporating an orthogonal turn was developed and optimized for the size-based gentle separation of CTCs which are larger and rarer than other blood cells. Some further design modifications were also suggested in the latter part of the work to increase the efficiency of enrichment
TWO NEW SPECIES OF POACEAE FROM INDIA
No full textTwo new species of Poaceae namely, Erayrostis santapaui K. G. Bhat & C. R. Nagendran and Chrysopogon pseitdozeylanicus K. G. Bhat & C. R. Nagendran have been described from materials collected by the senior author from Coorg- and South Kanara Districts of Karnataka State, India
UNDERSTANDING COMPLEXITY THROUGH PATTERN LANGUAGES IN BIOLOGICAL AND MAN-MADE ARCHITECTURES
No full textIn 1944, the celebrated physicist, Erwin Schrodinger, famously asked “What is Life?” Neither Schrodinger nor generations of illustrious scientists after him have been able to satisfactorily answer this question. What is generally agreed upon, however, is that being alive is about being complex: forming, transforming, and maintaining a structural organization that consists of multiple constituents arranged in specific orders and patterns. The advances in the theory of complexity have come not just from biologists, but also from architects and urban theorists. In this essay, I discuss how theorists from both life and architectonic sciences have come to a similar conclusion: that patterned and organized form ensures proper function and, ultimately, life. I show how deviation from this principle in biology leads to cancer and death; in architecture, the deviation allows the takeover of mechanical and imagery-based building ideologies leading to dysfunctional and ‘lifeless’ building and public spaces. </jats:p
Complexity: the organizing principle at the interface of biological (dis)order
No full textThe term complexity means several things to biologists. When qualifying morphological phenotype, on the one hand, it is used to signify the sheer complicatedness of living systems, especially as a result of the multicomponent aspect of biological form. On the other hand, it has been used to represent the intricate nature of the connections between constituents that make up form: a more process-based explanation. In the context of evolutionary arguments, complexity has been defined, in a quantifiable fashion, as the amount of information, an informatic template such as a sequence of nucleotides or amino acids stores about its environment. In this perspective, we begin with a brief review of the history of complexity theory. We then introduce a developmental and an evolutionary understanding of what it means for biological systems to be complex. We propose that the complexity of living systems can be understood through two interdependent structural properties: multiscalarity of interconstituent mechanisms and excitability of the biological materials. The answer to whether a system becomes more or less complex over time depends on the potential for its constituents to interact in novel ways and combinations to give rise to new structures and functions, as well as on the evolution of excitable properties that would facilitate the exploration of interconstituent organization in the context of their microenvironments and macroenvironments
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