PHARMACOGENOMIC APPROACHES TO IDENTIFY AND CHARACTERIZE TARGETS OF ANTICANCER DRUGS

Encouraging clinical studies are recently showing how a number of anticancer compounds work through a synthetic lethal mechanism by targeting pathways that are specifically essential for the viability of cancer cells but not of normal cells. We applied the concept of synthetic lethality by performing yeast high-throughput screens to define the chemical-genetic profile of three chemotherapeutic drugs: cisplatin, ecteinascidin, 5-fluorouracil. By means of the DDR-library, a collection of mutants defective in the DNA damage response, we identified the DNA repair pathways required to survive to the under investigation compounds: DSBR through HR, NER and PRR for cisplatin, DSBR, NER for ET-743, DSBR through HR for 5-FU. Importantly, we also defined the pathways whose absence leads to resistance: MMR and NHEJ for cisplatin, NER, MMR and NHEJ for 5-FU. By exploiting the complete knockout collection YKO-library, we analyzed in detail the yeast proteins involved in cisplatin and ET-743 response. Ecteinascidin-screen revealed that the lack of factors belonging to Swi/Snf complex, Swr1 complex and Mms4-Mus81 endonuclease causes hypersensitivity, while the absence of Slx5-Slx8 dymer leads to resistance. Through the cisplatin-screen, besides confirming the results obtained through the DDR-library, we determined the involvement of these proteins in CDDP survival: Rts1, B-type regulatory subunit of protein phosphatase 2A, Wss1, SUMO-dependent isopeptidase and Irc21, whose function had never been defined. Given the lack of knowledge on Irc21, we undertook a series of different approaches to identify Irc21 cellular role, finding interesting connections with mitochondria-, recombination- and chromatin remodeling-functions.