Transcript Tumorigeneze – onkogeneze -karcinogeneze

Základy
molekulární onkologie
Doc. MUDr. L. Boudová, Ph. D.
Tumorigeneze = onkogeneze
= karcinogeneze = vznik a růst nádorů
Nádor = abnormální populace se změněnou
genetickou informací
neletální poškození
normální genetické informace
získané
Chemické
Fyzikální
Viry
vrozené (germline)
Základní hypotéza
Tumour
monoclonal proliferation
Clonal expansion
Clonality testing
1. women heterozyg. for X-linked markers
2. specific translocations
3. gene rearrangements – B, T- cells
Carcinogenesis: multistep process
Gene expression
regulation in somatic body cells
• Specific
• Universal
• Regulation of gene expression
Základní třídy regulačních genů
dělení, růst, diferenciace, smrt buňky
I. Protoonkogeny
„podporují růst“, mutantní alely dominantní
II. Nádorové supresorové geny (antionkogeny)
normálně brzdí proliferaci, tzv. recesivní onkogeny
III. Geny regulující apoptózu
dominantní nebo recesívní vliv mutantní alely
IV. Geny regulující opravu DNA
mismatch repair genes, recesívní vliv mutantní al.
I. Protoonkogeny → onkogeny
• alelické formy téhož strukturního genu
• Protoonkogeny - v normálních buňkách
strukturní geny → translační produkty
protoonkoproteiny:
• Normální role v regulaci:
vedou k růstu, dělení a diferenciaci
• VERSUS onkoproteiny – v nádorových buňkách
vedou k neregulovanému dělení
abnormálně dlouhému přežívání
→ vznik nádoru
Fyziologická proliferace
1. Vazba: růstový faktor - specifický receptor na
buněčné membráně
2. Přechodná aktivace receptoru růstového faktoru,
aktivuje další proteiny na vnitřní straně
membrány
3. Přenos signálu cytosolem do jádra - second
messengers
4. Indukce a aktivace jaderných regulačních
faktorů, které iniciují transkripci DNA
5. Zahájení a postup buňky buněčným cyklem
(dělení)
I. Protoonkogeny kódují:
• A. Růstové faktory
• B. Receptory růstových faktorů
• C. Proteiny transdukující signály,
nereceptorové proteinkinázy
• D. Transkripční proteiny v jádře
• E. Cykliny a cyklin-dependentní kinázy
I. A. Growth factors
Normal: Stimulation of proliferation
when increased = overexpression
Carcinogenesis
Autostimulation of tumour cells
PDGF – protooncogene c-sis;
Epidermal growth factor;
Granulocyte macrophage stimulating factor
I. B. Growth factor receptors
Transmembrane proteins
Tyrosine kinase cytoplasmic domain
Activation: transient (normal)
versus persistent (tumour)
Mechanisms
 Hyperexpression of normal forms
 Mutations
 Gene rearrangements
EGFR family: cerb B1, c-erbB2-Her2/neu
RET
I. C. Signal transducing proteins
biochemically heterogeneous
Ras proteins = G proteins, bind GTP
• ras – GTP (act.) x GDP (inact.)
• ras: GTPase activity
GTPase activating proteins (GAP)
• Mutated ras binds GAP but persistent activation (GTP),
pathologic mitogenic influence
• ras mutation: the most frequent abnormality of dominant
oncogenes in human tumors (20%)
I. C. Other signal transducing proteins
Non-receptor protein kinases
• Tyrosine kinase activity
protooncogene abl
• t(9;22)(q34;q11) - bcr-abl
• chronic myelogenous leukemia;
• a subset of acute lymphoblastic
leukemia
Burkitt lymphoma
t(8; 14)(q24;q32)
c-myc, expression dysregulation
nuclear transcription factor
Chronic myelogenous leukemia
Reciprocal balanced
t(9; 22)(q34;q11)
Bcr-abl
210 kDa fusion protein
Tyrosine kinase activity
I. D. Nuclear transcription factors
• Myc, myb, jun, fos
• C-myc
gene of immediate early phase of growth
• Regulation of cell growth and apoptosis
Dysregulated expression: Burkitt lymphoma
Amplification: carcinoma of the breast, colon,
lung
Mechanisms of oncogene activation
Change of the gene

structure

expression regulation
abnormal protein
abundant protein
1. Point mutations (ras)
2. Chromosomal lesions (transloc., inversion;
hematology)
3. Gene amplification
- double minutes
- homogeneous staining regions
II. Tumour suppressor genes
= brakes of cell proliferation, antioncogenes
Gene Rb
Gene P53, P73
BRCA, APC, NF-1, DCC, VHL, WT1
II. Tumour suppressor genes
Cell cycle progression
 Cyclins
 Cyclin-dependent kinases (CDK) – phosphorylation
of critical target proteins -- progression
 CDK inhibitors
Key regulators of the cell cycle:
p16INK4a, cyclin D, CDK4, RB
Retinoblastoma
• 60% sporadic
• 40% familial – AD
• Knudson two-hit hypothesis
• 13q14
• LOH
II. Tumour suppressor genes
• P53, 17p13.1
mutated in many human cancers (50%)
mostly somatic mutations
Molecular policeman – prevents propagation
of genetically damaged cells, does not police
the normal cell cycle
Surveillance
Triggering checkpoint controls (G1/S, G2/M):
damaged cells
stop cell-cycle or slow down (p21)
Apoptosis (bax)
II. Tumour suppressor genes
• p53
Li-Fraumeni syndrome
• 1 p53 mutation inherited
• 25x ↑ risk of developing malignancy:
young, multiple, various
• Sarcomas, breast cancer, leukemia,
brain, adrenal tumours
II. Tumour suppressor genes
APC – 5q21 - adenomatous polyposis coli
down-regulation of growth-promoting signals
APC down-regulates β- catenin
(1. transcription, 2. cell adhesion)
Familial adenomatous polyposis
Gardner syndrome – AD
Colon adenoma, osteomas, epidermal cysts,
fibromatosis, dental abnormalities,
Malignancies of the duodenum and thyroid
II. Tumour suppressor genes
• VHL – 3p• Germline: inherited RCC, renal cysts
pheochromocytoma, haemangioblastoma
of cerebellum, retinal angioma
• Somatic mutations: sporadic
conventional RCC
• Influence on HIF-1;
• lack of VHL: increased angiogenesis
III. Apoptosis regulating genes
• Bcl-2, bax, bad; p53, MYC
• BCL-2 – follicular lymphoma t(14;18)(q32;q21)
• ↑transcription and overexpression of BCL-2
protein
IV. Mismatch repair genes
• Spell checkers, replication errors
• defective DNA repair - genome instability,
microsatellite instability
HNPCC = Lynch syndrome – familial, AD
I. Colon (proximal)
II. colon, ovary, endometrium, upper urinary
tract
IV. Mismatch repair genes
AR syndromes
Xeroderma pigmentosum
skin malignancies (UV – sun)
defective nucleotide excision repair
Ataxia – teleangiectasia
↑ IR sensitivity, developmental anomalies
Single gene mutation
1% of population: heterozygous carriers
Fanconi anemia
Bloom syndrome
↑IR sensitivity, developmental anomalies
DNA repair defects
• BRCA1 – 17q, BRCA2 – 13q
• Nucleus, transcription regulation, DNA repair
Familial
BRCA1: breast, ovary, prostate, colon
BRCA2: breast, also male, ovary, pancreas,
melanoma
• Breast carcinoma
Only 3% of all breast cancers carry BRCA
mutation
5-10% of breast cancers are familial
(of these: 80% BRCA mutations)
Carcinogenic agents
• Chemical
• Radiation – ionizing, UV
• Oncogenic microbes
Microbial carcinogenesis
Viruses
Bacteria
HPV, EBV, HHV8, HBV, HTLV-1
Helicobacter pylori, Borrelia burgdorferi
Dysplasia of uterine cervix
• Cervical intraepithelial neoplasia – CIN
Morphology of dysplasia:
Changes:
abnormal cytology - atypia
abnormal architecture
• Mild – moderate – severe
• HPV associated - risk –
low (6, 11)
high (16, 18)
Squamous cell carcinoma of the cervix
• Most common malignancy of the female
genital tract in developing countries
• (x developed countries: adenocarc. of
uterine body)
• Association: age at first intercourse,
promiscuity – HPV, low economic level,
smoking
• Grossly: polypoid or deeply infiltrative
• Microscopy: squamous cell carcinoma
EBV
• Infectious mononucleosis
• Burkitt lymphoma
• Hodgkin lymphoma
• B-cell lymphomas in immunosuppressed
patients (HIV, transplantation)
• Nasopharyngeal carcinoma
Diseases associated with
Helicobacter pylori infection
•
•
•
•
Chronic gastritis
Peptic ulcer
Gastric carcinoma
Gastric MALT lymphoma
MALT lymphoma

stomach, intestine (IPSID)
chronic antigenic stimulation
- Helicobacter pylori
Regulation: specific activated T-cells
Slow progression- 90%: stage IE, IIE
(bone marrow involvement: rare, 10%)
MALT lymphoma of the stomach