| Summary: |
Cancer chemotherapy has proven to be highly effective in certain tumour types, however its success in certain malignancies is often hampered by intrinsic or acquired chemoresistance (e.g. lung and pancreatic cancer), making this one of the major problems in tackling cancer effectively.
The cancer stem cell (CSC) hypothesis states that there is a small sub-population of tumour cells with self-renewing capacity that sustains tumour growth. These CSCs are also believed to be, in part, responsible for the chemoresistant phenotype due to overexpression of drug efflux pumps, alterations in apoptosis proteins, telomerase expression and increased antioxidant capacity [1-3]. One of the most frequently used CSC markers is the surface glycoprotein CD133, which is expressed in CSCs from a variety of different tumour types [3]. CD133+ cells, although representing only a small percentage of the cells that constitute a tumour, are highly tumorigenic and more resistant to a variety of chemotherapeutic agents when compared to CD133- cells (that constitute the bulk of the tumour) [4-9]. In fact, it is believed that chemotherapeutic regimens are not able to effectively eradicate CD133+ cells (but only the cells that constitute the bulk of the tumour) and that this will ultimately be responsible for recurrence, which could explain the higher percentage of CD133+ cells observed upon tumour recurrence [4].
It would therefore be extremely important to specifically target these chemoresistant CSCs and render them hemosensitive to the agents already used in the clinic, which is the ultimate objective of our project. We propose to accomplish this goal by using specifically designed siRNA-loaded nanoparticles conjugated to CD133 antibodies for targets involved in chemoresistance. As chemoresistance is often due to a combination of several mechanisms, we propose to simultaneously inhibit at least two of these mechanisms, in order to increase the success rate of the approach and broaden it  |
Summary
Cancer chemotherapy has proven to be highly effective in certain tumour types, however its success in certain malignancies is often hampered by intrinsic or acquired chemoresistance (e.g. lung and pancreatic cancer), making this one of the major problems in tackling cancer effectively.
The cancer stem cell (CSC) hypothesis states that there is a small sub-population of tumour cells with self-renewing capacity that sustains tumour growth. These CSCs are also believed to be, in part, responsible for the chemoresistant phenotype due to overexpression of drug efflux pumps, alterations in apoptosis proteins, telomerase expression and increased antioxidant capacity [1-3]. One of the most frequently used CSC markers is the surface glycoprotein CD133, which is expressed in CSCs from a variety of different tumour types [3]. CD133+ cells, although representing only a small percentage of the cells that constitute a tumour, are highly tumorigenic and more resistant to a variety of chemotherapeutic agents when compared to CD133- cells (that constitute the bulk of the tumour) [4-9]. In fact, it is believed that chemotherapeutic regimens are not able to effectively eradicate CD133+ cells (but only the cells that constitute the bulk of the tumour) and that this will ultimately be responsible for recurrence, which could explain the higher percentage of CD133+ cells observed upon tumour recurrence [4].
It would therefore be extremely important to specifically target these chemoresistant CSCs and render them hemosensitive to the agents already used in the clinic, which is the ultimate objective of our project. We propose to accomplish this goal by using specifically designed siRNA-loaded nanoparticles conjugated to CD133 antibodies for targets involved in chemoresistance. As chemoresistance is often due to a combination of several mechanisms, we propose to simultaneously inhibit at least two of these mechanisms, in order to increase the success rate of the approach and broaden its future applicability.
The specific targeting of molecules involved in CSC survival and chemoresistance has recently started to be successfully addressed [8,10,11]. However, as far as we know, our approach (to target different resistance mechanisms with siRNAs encapsulated into nanoparticles specifically designed to reach CSC) has never been attempted and would therefore be highly innovative and with potential future applications in the management of cancer patients.
In the first Task we will isolate the CD133+ and CD133- cell populations from established lung and pancreatic cancer cell lines and characterise them in terms of resistance/sensitivity to chemotherapeutic agents currently used in the management of these malignancies (e.g. cisplatin, carboplatin, etoposide and gemcitabine). In addition, we will characterise these cell populations regarding mechanisms that are known to be responsible for chemoresistance in CSCs such as: i) drug efflux pumps; ii) expression of apoptosis-related proteins; iii) telomerase expression and iv) resistance to oxidative stress. In Task 2 we will choose the proteins previously found to be overexpressed in the CD133+ cells as targets and use specific siRNAs to inhibit their expression and disrupt the corresponding chemoresistance mechanisms. The various resistance mechanisms will be targeted separately and simultaneously, allowing us to determine the most effective approach to render CD133+ cells chemosensitive. The third Task of the project will run alongside the first two and will consist of the development and characterisation of biodegradab |