Full Schedule

Claudia AM Wheeler-Kingshott, Ph.D.
University Reader in Magnetic Resonance Physics, Department of Neuroinflammation, UCL Institute of Neurology, London, UK

Abstract

Detecting neuronal activity in vivo non-invasively is possible with a number of techniques. Amongst these, in 1990 functional magnetic resonance imaging (fMRI) was proposed as a technique that has a great ability to spatially map brain activity by exploiting the blood oxygenation level dependent (BOLD) contrast mechanism [1, 2]. In fact, neuronal activation triggers a demand for oxygen and induces a localised increase in blood flow and blood volume, which actually exceeds the metabolic needs. This in turns causes an increase of oxyhaemoglobin in the venous compartment, which is a transient phenomenon and is accompanied by a transient change (decrease) in the concentration of deoxyhaemoglobin. Due to its paramagnetic properties, the amount of deoxyhaemoglobin present in the venous blood affects the local magnetic field seen by the spins (protons) and determines the local properties of the MR signal. A decrease in deoxyhaemoglobin during neuronal activity, therefore, induces local variations of this magnetic field that increases the average transverse relaxation time of tissue, measured via the T2* parameter [3]. This means that there is an increase of the MR signal (of the order of a few %, typically <5%) linked to metabolic changes happening during brain function. Activation can be inferred at different brain locations by performing tasks while acquiring the MR signal and comparing periods of rest to periods of activity.

The macroscopic changes of the BOLD signal are well characterised, while the reason for the increased blood supply, exceeding demands, needs further thoughts. Here we will discuss two approaches for explaining the BOLD phenomenon, one that links it to adenosine triphosphate production [4] and enzyme saturation, the other that relates it to the very slow diffusion of oxygen through the blood-brain-barrier with a consequent compensatory high demand of oxygen [5]. Some evidence of restricted oxygen diffusion has been shown by means of hypercapnia [6], although it is not excluded that both mechanisms may be present.

Overall, the BOLD signal changes theory and its physiological basis will be presented and discussed.

References

1. Ogawa, S., et al., Brain magnetic resonance imaging with contrast dependent on blood oxygenation. Proc Natl Acad Sci U S A, 1990. 87(24): p. 9868-72.
2. Kwong, K.K., et al., Dynamic magnetic resonance imaging of human brain activity during primary sensory stimulation. Proc Natl Acad Sci U S A, 1992. 89(12): p. 5675-9.
3. Bandettini PA, et al. Spin-echo and gradient-echo EPI of human brain activation using BOLD contrast: a comparative study at 1.5 T. NMR Biomed. 1994 Mar;7(1-2):12-20
4.  Fox, P.T., et al., Nonoxidative glucose consumption during focal physiologic neural activity. Science, 1988. 241(4864): p. 462-4.
5. Gjedde, A., et al. Reduction of functional capillary density in human brain after stroke. J Cereb Blood Flow Metab, 1990. 10(3): p. 317-26.
6. Hoge, R.D., et al., Linear coupling between cerebral blood flow and oxygen consumption in activated human cortex. Proc Natl Acad Sci U S A, 1999. 96(16): p. 9403-8.

Manzoor K, Ph.D.
Professor, Centre for Nanoscience & Molecular Medicine, Amrita University

Targeting aberrant cancer kinome using rationally designed nano-polypharmaceutics

Manzoor Koyakutty, Archana Ratnakumary, Parwathy Chandran, Anusha Ashokan, and Shanti Nair

`War on Cancer’ was declared nearly 40 years ago. Since then, we made significant progress on fundamental understanding of cancer and developed novel therapeutics to deal with the most complex disease human race ever faced with. However, even today, cancer remains to be the unconquered `emperor of all maladies’. It is well accepted that meaningful progress in the fight against cancer is possible only with in-depth understanding on the molecular mechanisms that drives its swift and dynamic progression. During the last decade, emerging new technologies such as nanomedicine could offer refreshing life to the `war on cancer’ by way of providing novel methods for molecular diagnosis and therapy.

In the present talk, we discuss our approaches to target critically aberrant cancer kinases using rationally designed polymer-protein and protein-protein core-shell nanomedicines. We have used both genomic and proteomic approaches to identify many intimately cross-linked and complex aberrant protein kinases behind the drug resistance and uncontrolled proliferation of refractory leukemic cells derived from patients. Small molecule inhibitors targeted against oncogenic pathways in these cells were found ineffective due to the involvement of alternative survival pathways. This demands simultaneous inhibition more than one oncogenic kinases using poly-pharmaceutics approach. For this, we have rationally designed core-shell nanomedicines that can deliver several small molecules together for targeting multiple cancer signalling. We have also used combination of small molecules and siRNA for combined gene silencing together with protein kinase inhibition in refractory cancer cells. Optimized nanomedicines were successfully tested in patient samples and found enhanced cytotoxicity and molecular specificity in drug resistant cases.

Nano-polypharmaceutics represents a new generation of nanomedicines that can tackle multiple cancer mechanisms simultaneously. Considering the complexity of the disease, such therapeutic approaches are not simply an advantage, but indispensable.

Acknowledgements:
We thank Dept. of Biotechnology and Dept. Of Science and Technology,Govt. of India for the financial support through `Thematic unit of Excellence in Medical NanoBiotechnology’ and `Nanomedicine- RNAi programs’.

Shrikant Anant, Ph.D.
The Department of Molecular & Integrative Physiology, Kansas University Medical Center, USA

Cancer Stem Cells: Target Colon Cancers

Shrikant Anant, Deep Kwatra and Dharmalingam Subramaniam

Colon cancer is a leading cause of cancer related deaths in the US, and its rate is increasing at an alarming rate in lndia. Recent studies have suggested the drug resistance role for a mall number of cells within a tumor called cancer stem cells. We identified the colon cancer stem cell marker DCLK1, a member of the protein kinase superfamily and the doublecortin family. The protein encodes a Cterminal serinethreonine protein kinase domain, which shows substantial homology to Ca2calmodulindependent protein kinase. Our current studies have been to identify compounds that can either affect DCLK1 expression or inhibits its activity as a way to inhibit cancer stem cells. Honokiol is a biphenolic compound that has been used in the traditional Chinese Medicine for treating various ailments. In vitro kinase assays with recombinant DCLK1 demonstrated that honokiol inhibits its kinase activity in a dose dependent manner. We therefore determined the effect of honokiol on stem cells. One method to look at effects on stem cells is perform a spheroid assay, where spheroids formation is suggested to maintain stemlike characteristic of cancer cells. Honokiol significantly suppressed colonosphere formation of two colon cancer cell lines HCT116 and SW480. Flow cytometry studies confirmed that honokiol reduced the number of DCLK1cells. A critical signaling pathway known to modulate intestinal stem cell proliferation is the Hippo signaling pathway, and deregulation of the pathway leads to tumor development. DCLK1cells had high levels of YAP1, the nuclear target of Hippo signaling. We determined the effect of honokiol on components of the hipposignaling pathway. Honokiol reduced the phosphorylation of Mst1/2, Lats1/2 and YAP1. Furthermore, honokiol treatment resulted in downregulation of YAPTEAD complex protein TEAD-1. Ectopic expression of the TEAD-1 partially rescued the cells from honokiol mediated growth suppression. To determine the effect of honokiol on tumor growth in vivo, nude mice harboring HCT116 tumor xenografts in their flanks were administered the compound intraperitoneally every day for 21 days. Honokiol treatment significantly inhibited tumor xenograft growth. Western blot and immunohistochemistry analyses demonstrated significant inhibition in the expression of stem marker and Hippo signaling proteins in the honokioltreated xenograft tissues. Taken together, these data suggest that honokiol is a potent inhibitor of colon cancer that targets DCLK1 stem cells by inhibiting Hippo signaling pathway.