5. Rationale: Increased understanding of the molecules associated with drug resistance would undoubtedly be useful for the discovery of new targets for the detection, delay or reversal of resistance. Objective: Identify proteins associated with Paclitaxel ® resistance and to examine their potential use as targets for modulating the resistant phenotype
6.
7. Prohibitin expression is elevated in Paclitaxel resistant cell lines Paclitaxel Resistance Paclitaxel Resistance - + - + - + - + Cell line 1 Cell line 2 Cell line 1 Cell line 2
8. Prohibitin1 localizes to the mitochondria in both drug-sensitive and resistant cell lines Paclitaxel-sensitive Paclitaxel-resistant
9. Prohibitin1 is localized to the cell surface in drug resistant cell lines Phb1 Antibody Rhodamine-PHB1-binding peptide Paclitaxel-sensitive Paclitaxel-resistant Paclitaxel-sensitive Paclitaxel-resistant
10. Prohibitin1-binding peptide preferentially localizes to Paclitaxel-resistant xenografts after intravenous injection Rhodamine-PHB1-binding peptide Rhodamine-PHB1-binding peptide DAPI DAPI Paclitaxel-sensitive Paclitaxel-resistant
11. Effect of Prohibitin1 siRNA on Taxol Sensitivity of Paclitaxel-resistant Cells
12. The generation of Paclitaxel-resistant cell lines with stable knockdown of Prohibitin (PHB1) or GST
19. EMERGING HYPOTHESIS: The selective spatial localization of Prohibitin1 may be necessary for the onset and/or maintenance for paclitaxel-resistance in human cancers.
20. SIGNIFICANCE: Prohibitin1 on the surface of tumor cells may represent a novel marker for the detection of taxane resistance in cancer patients either before or during the course of chemotherapy. It may also act as a novel target for therapeutic strategies for the treatment of drug-resistant tumors.
21. Ph. D. Candidate Research University of Toronto Jan. 2001 – Mar. 2006
37. EMERGING HYPOTHESIS: The selective spatial localization of insulin signalling molecules within the actin mesh may ultimately lead to GLUT4 arrival at the plasma membrane.
38. SIGNIFICANCE: A defect in insulin signalling leading to actin remodelling may contribute to insulin resistance in the skeletal muscle and to the onset of type 2 diabetes.
Hinweis der Redaktion
~ 40% of human tumors develop resistance to chemotherapeutic drugs While it is thought that the majority of cancers arise from a single precursor cell, it would be an error to view a tumor as consisting of a collection of genetically identical cells. One of the hallmarks of cancer is an increase in genetic instability and mutation rates. These changes mean that dividing cancer cells acquire genetic changes at a high rate. Practically, this means that the cells in a tumor, while similar, are NOT identical. When exposed to a cancer drug, those cells that are sensitive to the effects of the drug are killed. Those that are resistant will survive and multiply. The result is the re-growth of a tumor that is not sensitive to the original drug. Surprisingly, cells simultaneously acquire resistance to many chemically unrelated compounds to which the cell has never been exposed to. This phenomenon is referred to as multi drug resistance.
In order to validate the mass-spec data, cytoplasmic and microsomal fractions were isolated and probed for Prohibitin and GSTpi by western blot analysis.
A key regulator of actin dynamics we decided to focus on is cofilin. Cofilin is a highly expressed in various cell types and it functions as an actin depolymerizer. Upon binding to actin, cofilin induces a twist in the filament, and this conformational change weakens contacts between actin subunits, enhancing the depolymerization of actin. In the inactive state, cofilin is phosphorylated at Ser-3 (as shown here) and this prevents the depolymerization of F-actin. In contrast, active cofilin lacks phosphorylation at Ser-3, thus allowing for actin depolyermization.
