Oncogenes and Tumor. supressors

Transcription

1 Oncogenes and Tumor supressors From history to therapeutics Serge ROCHE

2 Neoplastic transformation

3 TUMOR SURESSOR ONCOGENE

4 ONCOGENES

5 History Transforming retrovirus RSV v-src is an oncogene c-src is the homolog of v-src v-src is a protein TK The first TKI in the clinic

6 Oncology meets RNA tumor virology Discovery of essential oncogenes Discovery of the mechanism of oncogene activation

7 Oncology meets RNA tumor virology I3K Src Ras Raf MEK MAK Myc Jun Fos transcription growth RNA tumour virus have captured essentiel regulators of cell growth

8 ONCOGENES roto-oncogenes (normal cellular gene) are important regulators of cellular growth roto-oncogene alteration (dominant) leads to malignant cell transformation Oncogene activation stems from genome instability or germline mutation Underlying mechanisms include: -retroviral insertion mutagenesis -point mutation -gene amplification -gene translocation

9 Tyrosine Kinases

10 rotein phosphorylation on Tyr A central mechanism to control cell communication in a multicellular organism writer reader erasor

11 Tyrosine kinome 90 TKs RTK SH3 SH2 cytoplasmic TK Oncogenic function

12 RTK activation Growth factor Inactive Active ptyr Recruitment of SH2-containing proteins

13 ptyr-dependent activation of RAS signaling Grb2 Ras SOS Grb2 SOS Ras No signal signal SOS: GEF for Ras

14 The connection of TK and RAS signaling I3K Src Ras Raf MEK MAK Myc Jun Fos transcription growth

15 Oncogenic TK activity in cancer TK

16 Mechanisms of RTK oncogenic activation Autocrine loop RTK gene amplification RTK somatic mutation HGF in CRC HER2 in CRC EGFR in lung cancer

17 Src oncogenic activation c-src linker U SH3 SH2 KINASE Y 527 v-src linker U SH3 SH2 KINASE Y Oncogenic Src leads to aberrant ptyr-dependent signal transduction

18 Src oncogenic activation by DNA tumor virus Middle T antigen (MT) olyoma virus MT stabilizes Src in oncogenic form

19 Src oncogenic signaling growth factor-independent signaling consistutive signaling SOS Src* Ras Raf MEK MAK Grb2 Shc I3K Jun Fos Stat3 Stat3 Stat3 Akt Myc cell transformation Src mimics RTK signaling by aberrant phosphorylation of key effectors

20 Src oncogenic activity in human cancer SRC somatic mutation is a rare event SRC si amplified is a subset of cancer (15% CRC) Src regulation has become inefficient in tumors through epigenetic mechanisms SRC oncogenicity is under the control of the SLA tumor supressor in CRC Src Src SLA UBE4A Y Akt signaling Y Substrate Substrate Ub Ub Ub Ub roteasomal degradation metastasis metastasis

21 The Src metastatic function in human cancer SRC EMT invasion survival SRC growth angiogenesis

22 Bcr-Abl oncogene in Chronic Myeloid Leukemia Chromosomic rearrangement generates Bcr-Abl fusion oncoprotein in 90% of CML Bcr-Abl SH3 SH2 Kinase Bcr-Abl SH3 SH2 Kinase active SH3 SH2 Kinase Coil-coil Coil-coil Bcr SH3 SH2 Kinase Abl

23 Bcr-Abl signalling Raf Ras SOS Grb2 MEK Y 177 SH3 SH2 Kinase SH3 SH2 Kinase MAK A1 Gene expression leukimogenesis

24 Additional fusion TK in human cancer The exemple of the RTK ALK in leukemia and lung cancer 3% 90% Like BCR-ABL in CML, EML4-ALK is an important driver in human cancer

25 RAS ATHWAY

26 RAS activator effectors Inhibitors (tumor supressor NF1)

27 RAS signaling RAS signaling 3 RAS members

28 K-RAS KRAS oncogenic mutations in cancer ** * GT binding G12 G13 L61 GF-independent signaling Ras Grb2 SOS aberrant signaling cell transformation

29 KRAS oncogenic activity in cancer Tumor Frequency ancreas 90% (K) Lung 35% (K) Colorectal 45% (K) Thyroid 60% (H, K, N) Sarcoma 45% (K, N) Melanoma 15% (N) Liver 30% (N) AML 30% (N) Ras oncogenic activation is frequent in cancer, but oncogenic RAS protein are not druggable so far!

30 Ras Raf MEK MAK Jun Fos A-C Raf v-raf RAF A Ser/Thr kinase that promotes cell growth An important druggable component of the RAS pathway Originally identified as a viral oncogene 3 members of the family RBD KINASE KINASE

31 Regulation of RAF signaling rotein dimerization is an important mechanism of kinase activation

32 B-RAF oncogenic mutations in cancer B-RAF mutations deregulate its kinase activity B-RAF oncoproteins induce aberrant MAK signaling B-RAF is an important driver of many cancers including melanoma

33 NUCLEAR ONCOGENES

34 Nuclear oncogenes Transcription factors v-myc, v-fos, v-jun, v-myb Nuclear proteins that blocks cell differentiation - v-erba from chicken erythroblastosis virus encodes a unclear receptor for the thyroid hormones blocks cell differentiation v-erba in cooperation with v-erbb, which encodes a truncating form of EGFR, induces leukemic cell transformation - Nuclear fusion proteins that blocks cell differentiation ML-RARalpha induces Acute promyelocytic leukemia, the M3 subtype of AML

35 Myc oncogene Myc is induced by growth factors Src I3K Stat3 Akt Ras Raf MEK MAK transcription Stat3 Stat3 Myc stabilization Myc protein upregulation is sufficient to induce cell transformation

36 Myc in human cancer Tumor activation neuroblastoma gene amplification (N, C) retinoblastoma gene amplification (C) Burkitt s lumphoma translocation (C) Others upregulation

37 TUMOR SURESSORS

38 Tumor supressors meet DNA tumor virology DNA tumor viruses inactivates major cell-cycle regulators

39 Small DNA tumor viruses SV40 Tumors in non-human cells Rb p53 Large T antigen Adenovirus mesothelioma Rb p53 E1A E1B HV cervical and oral cancers Rb p53 E7 E6

40 Tumor supressor Tumor supressors control cellular growth under normal and stress conditions Their complete inactivation (2 alleles) leads to malignant cell transformation Their inactivation stems from genome instability or germline mutation (familiar disease) Underlying mechanisms include somatic mutation -LOH - gene translocation - epigenetics

41 prb prb is the first tumor supressor gene mutated in the familial cancer, retinoblastoma prb inactivation is involved in many cancers (bladder, lung ) Familial retinoblastoma display Loss of Heterozygosity (LOH) in the RB locus (chr 13). The normal Rb protein still prevents mitosis. Inactivation of the RB onso-supressive function requires inactivation of the second allele (recessive)

42 prb RB regulates cell-cycle progression by controling transcription (a) RB fonction si regulated by mitogens through phosphorylation (a) RB belongs to a family of pocket proteins with similar function (b)

43 p53

44 53 inactivation in human cancer 53 is inactivated in most cancer 53 inativation occurs in 50% of human cancer 53 pathway inactivated in 90% of cancer, including in advanced stages 53 inactivation by can induced by somatic mutation These mutants behave as dominant negative p53 (most frequent mutation R273H)

45 The p53 family The guardian of the genome The guardian of the germline 3 members that are subjected to many TM and generate multiple isoforms

46 53 regulation Transcription factor DNA binding Tetramerization p53 TAD1 TAD2 r DBD OD Normal cell ATM, CHK2 Stressed cell p53 MDM2 p53 p53 p53 p53 AcM p53 e p53 p53 p53 p53 target genes MDM2 p53re Low p53 level Stabilized p53 Active p53

47 53 regulates DNA damage response Replicative senescence (Telomere erosion) DNA breaks Genotoxic stress NBS1 RAD50 H2AX MRE11 ATM ATR 53B1 BRCA1 CHK2 CHK1 p53 Mdm2 p21waf1 Cell cycle arrest and Senescence

48 53 signaling in cancer

49 Additional tumor supressor genes CELL CYCLE WT-1 p46-49wt MTS-1/p16 inhibitor of cdk-4/cyclin D MTS-2/p15 inhibitor of cdk-4-6, WAF/p21 inhibitor of cdk-2/cyclin D/E SIGNAL TRANSDUCTION Receptor DCC NF-1 (Neurofibromin) rasga SOCS inhibitors of the Jak/Stat pathway TEN, I3 Tase TSC1/2 inhibitor of mtor AC promotor of beta-catenin degradation Smad4 inhibitor of TFGbeta signaling

50 CLINICAL IMLICATIONS

51 Targeted therapies Tumor supressor Function reactivation ONCOGENE TUMOR SURESSOR oncogenic Function inhibition

52 Strategies to target an oncogenic Kinase Small lobe interface TK domain Big lobe

53 Bcr-Abl in CML Chromosomic rearrangement generates Bcr-Abl fusion TyrK in 90% of Chronic Myeloid Leukemia CML Bcr-Abl SH3 SH2 Kinase Bcr-Abl SH3 SH2 Kinase active SH3 SH2 Kinase Coil-coil Coil-coil Bcr SH3 SH2 Kinase Abl

54 TKI in CML ABL Imatinib

55 EGFR in lung cancer Expressed in 80% of lung cancer Mutated in 10-20% of lung cancer

56 EGFR TKI Only active in tumors expressing oncogenic EGFR

57 Activity of EGFR inhibitors in lung cancer A minority of patients with refractory non-small-cell lung cancers show dramatic response to Iressa

58 Oncogenic addition others? EGFR others? EGFR L858R MAK I3K MAK I3K Sensitivity to Iressa -/+ + Tumor cells addicted to EGFR signals

59 Induced resistance to EGFR inhibitors Resistance: oint mutation that lowers the affinity to Iressa Relapse in non-small-cell-lung cancer

60 Verumafenib a specific inhibitor of B-RAF

61 Resistance to B-RAF inhibition in patients

62 Molecular causes of resistance to B-RAFi

63 Take-home message Targeted therapies based oncogenic kinase inhibition can be effective. Resistance occurs due to mutations and/or increase in kinase level that both reduce drug efficiency Alternatives include more potent inhibitors and/or combined therapy that target oncogenic resistance signaling