Exploiting science for engineering: BRCA2 targeted therapies

Transcription

1 MOD1 DNA ENGINEERING Fall 2010 Exploiting science for engineering: BRCA2 targeted therapies Orsi Kiraly Engelward lab

2 Homologous recombination is important No HR chromosomal aberrations cell death Sonoda 1998 Faulty HR normal Rad51-/- no HR premature aging cancer

3 Homologous recombination is critical for repair of broken replication forks

4 Homologous recombination is critical for repair of broken replication forks Grigorova 2004 NHEJ BRCA2-/-

5 Understanding biology leads to new technologies h2p://wyss.harvard.edu h2p://

6 Recombinant DNA toolbox is from nature Plasmids Radloff 1967 PNAS Heat stable DNA polymerases Photo: Agriculture and Agri-Food, Canada Restriction endonucleases Lydia Dorner and Ira Schildkraut, New England Biolabs

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8 Understanding science leads to new technologies: BRCA2 targeted therapy PARP Inhibitors Represent New Direction in Cancer Treatment Roitt 1956

9 Metabolism is suppressed by alkylating agent In tumor cells no treatment CO 2 from catabolism alkylating agent Roitt 1956 Time (min)

10 NAD levels are lowered by alkylating agent In tumor cells no treatment CO 2 from catabolism Alkylating agent + NAD alkylating agent Roitt 1956 Time (min)

11 NAD levels are lowered by alkylating agent In slime mold NAD Less NAD is made? Why? No Time (hours) More NAD is degraded? No Used up to build something?? Yes! PARP activity up 200% Poly(ADP-ribose) polymerase (PARP) Time (hours) Whish 1975

12 NAD is a precursor for poly(adp-ribose) chromatin

13 What is the role of poly(adp-ribosylation)? Inhibit it, see what happens: % Surviving cells control PARP inhibition Alkylating agent Inhibition of PARP affects survival after treatment with DNA damaging agent PARP has a role in DNA repair Durkacz 1980 Mouse leukemia cells

14 What is the role of poly(adp-ribosylation)? Inhibit it, see what happens: More HR More single strand breaks Waldman 1991 Boulton 1999 In the absence of PARP, HR is needed to fix broken fork HR What about cancer cells that can t do HR?

15 What about cancer cells that can t do HR? Potentially TOXIC no PARP NHEJ BRCA2-/-

16 BRCA2 null cells are extremely sensitive to PARP inhibitors In cells PARP inhibitor Surviving fraction BRCA2 null wt wild type BRCA2 null Bryant 2005 PARP inhibitor (µm)

17 BRCA2 null cells are extremely sensitive to PARP inhibitors In mice wt Frequency of tumor formation BRCA2 null wt PARP inhibitor BRCA2 null Farmer 2005 Time (days) TARGETED to tumor by virtue of the tumor s own mutation!

18 advanced ovarian cancer

19 Synthetic lethality and an assay to find it Each decrease expression of a single gene

20 Lecture 1: Lecture 2: Intro to importance of HR How HR works Lecture 3: Why understanding mamers: BRCA2 and HR Lecture 4: Lecture 5: Lecture 6: Lecture 7: Lecture 8: ExploiRng scienrfic understanding for engineering: BRCA2 targeted therapies Measuring HR in genotoxicity tesrng, using HR in genome engineering of mice Journal arrcle discussion StaRsRcs Flow Cytometry: How it works and how to do it

21 Mod 1: DNA Engineering Engineering in vitro recombinaron assay Day 4

22 A Plasmid-Based Assay for Homologous Recombination in Mammalian Cells Δ5 + lipofect 48 hours Δ3

23 1 PCR X E 2 Purif. X E Digest 2 X E Gel 3 Purif. X E X E Gel 3 Anal. X E X E Plan Lig. 3 X E Ligate 4 4 Transform E. coli E. coli E. coli E. coli

24 Ligase from T4 bacteriophage is used in recombinant DNA technology textbooko?acteriology.net

25 Your ligation reaction Ligase ATP Buffer Water, salts, buffer system DTT Ligase has NO activity w/o DTT DTT is unstable Make single use aliquots Vortex to suspend SMELL Vector Insert How much? In what ratio?

26 Your ligation reaction Vector Insert How much? In what ratio? Reaction conditions Optimal temperature for T4 ligase is 25 C

27 Your ligation reaction: possible outcomes nothing Population of different products Need to separate and amplify individual products to analyze and select correct one

28 Transforming bacteria with ligation reaction MIX SHOCK PLASMID TAKEN UP electric (10-20 kv/cm) temperature (42 C ice) RECOVER grow in rich media SEPARATE SELECT AMPLIFY separate by spreading

29 Proceed to grow up individual colonies and analyze ligation products SEPARATE SELECT AMPLIFY GROW UP INDIVIDUAL COLONIES ISOLATE PLASMID DNA ANALYZE