carcinogenesis

Question 1

It is a phenomenon of gene alteration, which may result from the interaction of ultimate carcinogens with DNA in the target cell.

Answer 1

Initiation

Question 2

It refers to a phenomenon of gene activation in which the latent altered phenotype of the initiated cell becomes expressed through selection and clonal expansion

Answer 2

promotion

Question 3

It refers to a phenomenon of gene activation in which the latent altered phenotype of the initiated cell becomes expressed through selection and clonal expansion

Answer 3

promotion

Question 4

It is the last irreversible stage of multistage carcinogenesis, which usually develops from the cells in the stage of promotion.

Answer 4

Progression

Question 5

A chemical is transformed into a DNA-reactive metabolite (ultimate carcinogen).

Answer 5

Metabolic Conversion to an Ultimate Carcinogen

Question 6

The ultimate carcinogen binds to DNA, causing structural damage (e.g., mutations, adducts).

Answer 6

DNA Interaction and Structural Alteration

Question 7

Cellular repair mechanisms may reverse the damage, but if unsuccessful, mutations persist.

Answer 7

DNA Repair Attempts

Question 8

When the damaged cell divides, the mutation becomes permanently fixed in the genome

Answer 8

Cell Proliferation and Mutation Fixation

Question 9

It is the second stage in multistage carcinogenesis, characterized by the activation of gene expression that leads to the clonal expansion of initiated cells.

Unlike initiation, promotion does not involve direct DNA damage but rather alters gene expression patterns, allowing preneoplastic cells to proliferate

Answer 9

PROMOTION

Question 10

ASPECTS OF PROMOTION

Answer 10

Reversible
Non Genotoxic
Long Duration
Dose Dependent

Question 11

Dependent on continuous exposure to promoting agents; lesions may regress if
exposure stops.

Answer 11

Reversible

Question 12

Tumor promoters do not directly damage DNA but modify cellular signaling pathways

Answer 12

Non Genotoxic

Question 13

Can persist for decades in humans.

Answer 13

Long Duration

Question 14

Exhibits threshold effects (sigmoid dose-response curve)

Answer 14

Dose-Dependent

Question 15

Promoters stimulate the proliferation of initiated cells, giving them a growth advantage.

Answer 15

Clonal Expansion of Initiated Cells

Question 16

Promoters modify cell signaling pathways, leading to changes in:
-Growth factors (e.g., EGFR signaling).
-Anti-apoptotic mechanisms (e.g., Bcl-2 upregulation).
-Inflammatory responses (e.g., NF-κB activation

Answer 16

Altered Gene Expression

Question 18

Many promoters (e.g., phenobarbital, TCDD) suppress programmed cell death, allowing
preneoplastic cells to survive.

Answer 18

Inhibition of Apoptosis

Question 19

Withdrawal of promoters can lead to apoptosis-induced regression of preneoplastic
lesions.

Answer 19

Reversibility and Regression

Question 20

It represents the final, irreversible stage of multistage carcinogenesis,
developing from previously promoted cells. This stage is characterized by
increasing genomic instability and karyotypic evolution, leading to morphologically
detectable changes in cellular structure.

Answer 20

Progression

Question 21

Key Aspects of Progression

Answer 21

Irreversible genetic damage (distinct from reversible promotion)
Karyotypic instability (abnormal chromosome structure/number)
Emergence of invasive/metastatic potential
Clinical cancer manifestation

Question 22

Chemicals that drive transition from promotion to progression

Answer 22

Progressor Agents

Question 23

The dose of a substance that causes death in 50% of a population of test animals.

Answer 23

LD50 (Lethal Dose 50):

Question 24

The concentration of a substance in the environment that causes death in 50% of a
population of test organisms.

Answer 24

LC50 (Lethal Concentration 50):

Question 25

The highest dose or concentration of a substance that does not cause any observable adverse effects

Answer 25

NOAEL (No Observed Adverse Effect Level)

Question 26

The highest concentration of a substance that does not cause any observable effects.

Answer 26

NOEC (No Observed Effect Concentration):

Question 27

The lowest concentration of a substance that causes observable effects

Answer 27

LOEC (Lowest Observed Effect Concentration)

Question 28

are the methods used to determine the harmful effects of substances on living organisms.

Answer 28

Toxicity measurements

Question 29

are the specific effects or outcomes that are measured in toxicity tests, such as lethality, growth, reproduction, or changes in behavior or physiology

Answer 29

Toxicity endpoints

Question 30

Short-term tests measuring the effects of high concentrations of chemicals, with endpoints often reflecting lethality.

Answer 30

Acute Toxicity Tests

Question 31

Longer-term tests measuring the effects of lower, less toxic concentrations, with endpoints concerning sublethal effects like reproduction or grow

Answer 31

Chronic Toxicity Tests

Question 32

It is the first critical stage in chemical carcinogenesis, characterized by permanent genetic damage in a target cell due to exposure to a carcinogenic agent.

Answer 32

INITIATION

Question 33

Activates PKC → cell proliferation

Answer 33

TPA (Phorbol ester)

Question 34

Induces liver enzyme activity → cell growth

Answer 34

Phenobarbital

Question 35

Binds Ah receptor → alters gene expression

Answer 35

TCDD (Dioxin)

Question 36

Promotes colon cell proliferation

Answer 36

Colic Acid

Question 37

Cigarette smoke contains initiators (e.g.,) and promoters (e.g.,)

Answer 37

benzo(a)pyrene phenols