Molecular tumor biology 2.Proto-oncogenes and tumor suppressor genes

Viral factors of the oncogenesis

Dr. Gábor MátisUniversity of Veterinary Medicine

Division of Biochemistry

8 March 2018

Topics

• Overview of regulatory pathways involved inoncogenesis:– Cell cycle– Apoptosis– Signalling pathways – growth, proliferation

• (Proto-)oncogenes and tumor suppressorgenes

• Viral factors of the oncogenesis

The cell cycle

G0 = cells with no more proliferationpotential

G0

G1 = an active cell with normalbiological functions

S = synthesis phase, DNA-replication= duplication of the whole genome.

G2 = production of enzymes,membrane components and cellorganelles

M = mitosis, cell division

Regulation of the cell cycle – cyclins andcyclin-dependent kinases (CDK)

Wikipedia.com;slideplayer.com

The apoptosisApoptosis = programmed cell death• Regulated process• Only the given cell is involved• Requires energy• Catalyzed by the caspase enzymes• Cell organelles are getting fragmented

apoptotic bodies• Physiological, essential process• No inflammation• Apoptosis vs. necrosis!

en.wikipedia.org

The steps and signalling pathways of apoptosis

quora.com

Regulation of growth, replication and transcription:tyrosine kinase dependent pathways

Ras / MAP kinase cascade• 1. Receptor Sos Ras RafMEK

(MAPKK) Erk (MAP kinase) transcription!• 2. MAPK-cascadeRasPI-3-kinasePKB/Akt

http://biokemia.elte.hu/oktatas/bsc/biokemia_jel1.pdf

The Ras / MAP kinase cascade

The role of the Ras / MAP kinase cascade in theoncogenesis

Roberts and Der (2009): Targeting the Raf-MEK-ERK mitogen-activated protein kinase cascade for the treatment of cancer.Oncogene, 26, 3291-3310.

(Proto-)oncogenes and tumorsuppressor genes – definitions

• Proto-oncogenes:– Involved in the signalling pathways of cell division, cell

growth: stimulatory action– Mutation or increased expression transformed to

oncogenes oncogenesis (tumorigenic transformation)

• Tumor suppressor genes:– Main functions:

• Cell division, DNA replication: inhibitory action• Stimulating cell differentiation• Inducing apoptosis

– Mutation or decreased expression inactivation lackof protective action against cancer

(Proto-)oncogenes

• Growth factors: e.g. PDGF, EGF,IGF-1, VEGF…

• Growth factor receptors:tyrosin kinase type receptors!– e.g. EGF receptor

• Protein kinases• Regulators of cell cycle: cyclins• Anti-apoptotic proteins: e.g. Bcl

family• Transcription factors:

e.g. NF kappa B

Growth factors: the action of PDGF

(Proto-)oncogenes

• Growth factors: e.g. PDGF, EGF, IGF-1,VEGF…

• Growth factor receptors:tyrosin kinase type receptors!– e.g. EGF receptor = EGFR (HER2!)

• Protein kinases• Regulators of cell cycle: cyclins• Anti-apoptotic proteins: e.g. Bcl

family• Transcription factors:

e.g. NF kappa B

Growth factor receptors: the action ofEGFR

mindsofmalady.com

Role of HER2 in the treatment ofmammary gland tumors

Trastuzumab HER2 inhibition

Tyrosine kinase inhibition in thetreatment of canine mastocytoma (2015)

• Imatinib tyrosine kinase (KIT, Bcr-Abl) inhibition

(Proto-)oncogenes

• Growth factors: e.g. PDGF, EGF, IGF-1,VEGF…

• Growth factor receptors:tyrosin kinase type receptors!– e.g. EGF receptor

• Protein kinases: e.g. MAP kinasecascade – Ras, Raf

• Regulators of cell cycle: cyclins• Anti-apoptotic proteins: e.g. Bcl

family• Transcription factors:

e.g. NF kappa B

Protein kinases as proto-oncogenes:Ras, Raf

(Proto-)oncogenes

• Growth factors: e.g. PDGF, EGF,IGF-1, VEGF…

• Growth factor receptors:tyrosin kinase type receptors!– e.g. EGF receptor

• Protein kinases• Regulators of cell cycle: cyclins• Anti-apoptotic proteins: e.g. Bcl

family• Transcription factors:

e.g. NF kappa B

Inhibition of anti-apoptotic proteins

Clinical Cancer Research

The role of Bcl-2 inhibition in thetreatment of tumors

• Taxol/paclitaxel: Bcl-2 inhibition• Mammary gland, ovary-, cervix, GI tumors

(Proto-)oncogenes

• Growth factors: e.g. PDGF, EGF,IGF-1, VEGF…

• Growth factor receptors:tyrosin kinase type receptors!– e.g. EGF receptor

• Protein kinases• Regulators of cell cycle: cyclins• Anti-apoptotic proteins: e.g. Bcl

family• Transcription factors:

e.g. NF kappa B

Effects of NF-kappaB

• Inactive in normal cells, but active in tumorcells!

• Proto-oncogene effect• Stimulation of cell division• Inhibition of apoptosis• Stimulation of angiogenesis (VEGF, IL-8)• Stimulation of metastases

• Other diseases: emergence of asthma, diabetesmellitus, arteriosclerosis!

Dr. Buday László: Orvosi biokémia előadások

Inflammatory processes!

ACTIVATION of NF-kappaB

growth factorreceptor

IKK complex

PI-3-kinase

Ser-32 and Ser-36go throughphosphorylation

Tumor suppressor genes• Cell surface molecules

– TGFβ: stimulating CDK inhibitors• CDK inhibitors: cyclin/cyclin-dependent kinase inhibitors

cell cycle arrest– p16 gene: inactivationmelanoma, pancreas, kidney, lung

tumors– p21 gene

• Citoplasmic signalling molecules: inhibiting the activationof proto-oncogenes– GAP: GTPase-activating proteins activating the GTPase

function of Ras• Transcription factors

– p53 gene: regulation of cell cycle (CDK inhibition!) and apoptosis– Rb (Retinoblastoma) gene: dephosphorylated protein binding

and inactivation of E2F transcription factors• DNS repair genes

The function of TGFβ

Tumor suppressor genes• Cell surface molecules

– TGFβ: stimulating CDK inhibitors• CDK inhibitors: cyclin/cyclin-dependent kinase inhibitors

cell cycle arrest– p16 gene: inactivationmelanoma, pancreas, kidney, lung

tumors– p21 gene

• Citoplasmic signalling molecules: inhibiting the activationof proto-oncogenes– GAP: GTPase-activating proteins activating the GTPase

function of Ras• Transcription factors

– p53 gene: regulation of cell cycle (CDK inhibition!) and apoptosis– Rb (Retinoblastoma) gene: dephosphorylated protein binding

and inactivation of E2F transcription factors• DNS repair genes

The function of p16 and RB proteins

Tumor suppressor genes

• Cell surface molecules– TGFβ: stimulating CDK inhibitors

• CDK inhibitors: cyclin/cyclin-dependent kinase inhibitors cellcycle arrest– p16 gene: inactivationmelanoma, pancreas, kidney, lung tumors– p21 gene

• Citoplasmic signalling molecules: inhibiting the activation of proto-oncogenes– GAP: GTPase-activating proteins activating the GTPase function of

Ras• Transcription factors

– p53 gene: regulation of cell cycle (CDK inhibition!) and apoptosis– Rb (Retinoblastoma) gene: dephosphorylated protein binding and

inactivation of E2F transcription factors• DNS repair genes

The function of p53 protein

• The most important tumor suppressor!! (humantumors: >50% with p53 mutation)

• DNA damage p53 protein detached fromMDM-2 and getting phosphorylated bindingto p21 gene promoter p21 protein production inhibition of cyclin/cyclin-dependent kinasecomplex cell cycle arrest, no proliferation +apoptosis induction

• p53 mutation no protective actiononcogenesis

The function of p53 protein

Seanholton.wordpress.com

Role of p53 in cancer therapy• „Traditional” chemo-/radiotherapy: DNA damage activation of p53

• Removal of mutant p53: Adenoviruses (E1B-deleted) replicating only in p53-mutant tumorcells

• Insertion of wild-type p53:– Gene therapy with Retrovirus vector (lung tumors)– Gene therapy with Adenovirus vector (Ad-p53)

(ovarian tumors) – Gendicine (Advexin)• Activating p53 signalling

Tumor suppressor genes• Cell surface molecules

– TGFβ: stimulating CDK inhibitors• CDK inhibitors: cyclin/cyclin-dependent kinase inhibitors

cell cycle arrest– p16 gene: inactivationmelanoma, pancreas, kidney, lung

tumors– p21 gene

• Citoplasmic signalling molecules: inhibiting the activationof proto-oncogenes– GAP: GTPase-activating proteins activating the GTPase

function of Ras• Transcription factors

– p53 gene: regulation of cell cycle (CDK inhibition!) and apoptosis– Rb (Retinoblastoma) gene: dephosphorylated protein binding

and inactivation of E2F transcription factors• DNS repair genes

The function of GAP

Proto-oncogenes and tumor suppressor genes