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Utilizza questo identificativo per citare o creare un link a questo documento:
http://hdl.handle.net/10761/95
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Data: | 2-mag-2011 |
Autori: | Fabrizi, Eros |
Titolo: | Identification of novel therapeutic targets for colon adenocarcinoma |
Abstract: | Colorectal cancer (CRC) is the third most common form of cancer in the Western world.
Despite the emergence of new targeted agents and the use of various therapeutic
combinations, none of the treatment options available is curative in patients with advanced
cancer. A growing body of evidence is increasingly supporting the idea that malignancies
originate from a small fraction of cancer cells, called Cancer Stem Cells (CSC), that show
self-renewal and pluripotency and are capable of initiating and sustaining tumor growth.
Several studies have shown that, with respect to the bulk of tumor cells, CSC posses a
higher degree of resistance to chemotherapy and radiotherapy that could explain the
inefficacy of current therapies. The ability to isolate and study these tumor cells provided a
powerful tool for the investigation of drug-and radio-resistance mechanisms thus paving
the way for the development of novel targeted therapies aimed at the tumor complete
eradication.
The aim of this PhD thesis was to use CSC lines, derived from CRC specimens, to
individuate new potential molecular targets for the development of novel therapies. To this
end four colon-CSC lines were subjected to phosphoproteomic analysis by RPPA (Reverse
Phase Protein Array) technology. Through this analysis phosphorylation levels of various
protein kinases and their substrates were evaluated in order to create an activation map of
the main colon-CSC proliferation and cell survival pathways. In parallel colon-CSC lines
have been screened in vitro to the action of 80 commercially available protein-kinase
inhibitors. This screening has revealed a partial correlation between in vitro sensitivity and
phosphoproteomic analysis, but in this study, was not possible to identify predictive factors
to infer colon-CSC sensitivity to specific kinase inhibitors. Colon-CSC was sensitive to the
inhibition of protein kinase C (PKC), known regulator of cell proliferation and survival.
Among PKC inhibitors, the most interesting was the UCN-01, a staurosporine derivative
that can also inhibit PDK1 and Chk1. This compound has been already used in clinical
trials as antineoplastic agent in combination with conventional chemotherapy. The in vitro
treatment of colon-CSC with UCN-01 has demonstrated its ability to enhance the
irinotecan cytotoxicity by increasing the apoptotic response. The combined action of
UCN-01 and irinotecan caused a marked reduction in the levels of antiapoptotic proteins
such as Bcl-XL and Mcl-1 and the activation of caspase 3.
The in vivo administration of UCN-01/irinotecan combination, in a mouse model of
subcutaneous xenograft, confirmed the observations obtained in vitro, leading to a
significant reduction in tumor growth compared to the single treatments. UCN-01 has also shown efficacy in the inhibition of Chk1, as demonstrated by the reduction of the
phosphorylation of its target protein cdc25. Inhibition of Chk1, an important regulator of
cell cycle, in combination with chemotherapy, could help in reducing the viability of
colon-CSC, thus preventing cell cycle arrest and repair DNA damage induced by
irinotecan. Although UCN-01 exerts its effect by inhibiting the activity of various protein
kinases, this reduced selectivity could be the basis of its effectiveness. The present study
demonstrated that it is possible to identify, among the commercially available compounds,
those that interfere with processes that regulate colon-CSC survival or proliferation and
therefore are potentially able to interfere with tumor growth. The use of newly developed
inhibitors, combined with the analysis of genetic alterations or phosphoproteomic, will
identify factors predictive of response to therapy and lead to the possibility of developing
individualized therapeutic strategies, increasing the likelihood of success of targeted therapy. |
In | Area 05 - Scienze biologiche
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