Oncology 3- Tumourigenesis

Question 1

Protooncogenes

Answer 1

-normal genes that enhance cell growth, proliferation, function and inhibit apoptosis
>includes growth factors, growth factor receptors, signal transducers, apoptosis regulators

Question 2

Oncogenes

Answer 2

-mutated form of gene
-a dominant change (so only one gene needs to be affected) resulting in increased cell replication and inhibition of apoptosis

Question 3

Oncogene mutation

Answer 3

-RAS-A is permanently turned on
>dephosphorylation does not occur and there is an continuous increase in cell replication

Question 4

DNA damage

Answer 4

-many potential causes and very frequent
>there are multiple proofreading and repair enzymes
>BUT as there are progression through the cell cycle and DNA division with damaged DNA, this damage becomes “fixed”= permanent

Question 5

Tumour suppressor genes

Answer 5

-normal cellular genes that inhibit cell proliferation and growth (FIX it or DIE)
>includes cell adhesion molecules, ell cycle regulatory molecules, signal transducers, growth inhibitory factors
Ex. p53, and Retinoblastoma genes

Question 6

P53

Answer 6

-located in 2 locations within the cell replication cycle that check for DNA damage =guardian of genome
-stimulated by many signals (cell in harmful damage, stressors)

Question 7

P53 biologic effects

Answer 7

1.prevents cells from progressing through cell cycle
2.activates genes that help with cell repair
3.activates cells that induce apoptosis

Question 8

Retinoblastoma gene (RB)

Answer 8

-acts like a boot on a car. Will prevent DNA from uncoiling and therefore cannot replicate

Question 9

Tumour suppressor genes affected by mutation

Answer 9

-One hit: germ cell mutation
>predisposed to damage because already partially damaged by only having one good allele
-Two hits: somatic cell mutation
>have to be unlucky and have both alleles damaged
**Both alleles need to be affected because it is recessive

Question 10

Epigenetic change

Answer 10

-heritable change in gene expression without DNA sequence alteration

Question 11

DNA methylation

Answer 11

-addition of methyl groups to DNA in specialized islands which physically prevents transcription of the gene
>decrease methylation=increase transcription of gene
>increase methylation= gene slicing

Question 12

Imprinting

Answer 12

-normal suppression of maternal or paternal allele of gene in a somatic cell

Question 13

Loss of imprinting

Answer 13

-results from a DNA methylation
-results in both the maternal and paternal allele being expressed, resulting in increased levels of growth factors being produced

Question 14

MicroRNA

Answer 14

-genes that encode short strands that bind to complementary mRNA and prevent protein translation
>another form of gene expression regulation and can act as an oncogene or a tumour suppressor gene depending on target mRNA

Question 15

Malignant transformation criteria

Answer 15

**will most likely have all of these
1.Mutated DNA repair genes
2. Mutated oncogenes
3.Mutated or no tumour suppressor genes