class 19 cancer part 2

are cell growth and differentiation stricly generated?

yes

what causes uncontrolled cell divison

when genes that control these functions are mutated or aberrantly expressed

what types of genes are mutated in cancer cells so that they divide uncontrollably?

the genes that control cell growth and differentiation

what is the signifigance of G0 with respect to cancer cells?

healthy cells that stop prolifting enter G0

cells can exit G0 and re-enter the cycle

cancer cells are unable to enter G0

how is the cell cycle regulated

by an interplay of genes whose products either promote or suppress cell division

cells that regulated the profession through the cell cycle by

1. cyclins and cyclin decedent kinases (CDKS)
2. proteins that regulate cell cycle checkpoints

how do cyclins and CDKS work?

a healthy cell regulated synthesis and destruction of different cyclins at different times during the cell cycle

what are the cell cycle checkpoints

when cells decide whether to proceed to the next stage of the cell cycle

where do the cell cycle checkpoints happen at

G1/S, G2/M, and M

what are the general steps of apoptosis

1. nuclear DNA becomes fragmented
2. internal cellular structures break down
3. the cell dissolves into small spherical structures know as apoptosis
4. an optoic bodies are destroyed by the immune system

Bcl2

PREVENTS apoptosis

BAX

INITIATES apoptosis

porto-oncogenes

activated if a cell needs to divide and is the promoter of cell division. “gas pedal”

Tumor suppressor genes

supresses cell division “break pedal”. initiates apoptosis

how are oncogene and photo-oncogene related

An oncogene is a proto-oncogene that is mutated or abnormally expressed and contributed to the development of cancer.

in cancer cells, one or more photo-oncogenes are altered

true

example of proto-oncogene: Was

ras genes encode signal transduction molecules that regulate cell growth and division

is a tumor supressor gene a transcription factor

yes

p53

guardian of the genome

what does p53 do

regulates the cell cycle checkpoints and some also initiate apoptosis

when tumor supressor genes are mutated or inactivated what are cells unable to do

they cannot respond to cell cycle checkpoints AND/OR cannot undergo apoptosis

simplified model of metastasis

1. cancer cells leve the original primary tumor and break out of the tissue of the origin
2. cancer cells than travel in the blood of lymph vessels to other parts of the body
3. cancer cells then leave the vessels and begin secondary new tumors

how can we be predisposed to some cancers?

other mutations of epigenetic alterations in other genes also need to occur in order for cancer to develop in most cancers.

are most inherited cancer-susceptibility alleles not sufficient in themselves to trigger cancer development?

no

loss of heterozygosity

if only the wild-type allele in a cell is altered so that it doesnt work, the the call has mo functioning alleles of the tumor supressor.

how much percent are viruses linked to cancer

12%

retrovirus

can contribute to cancer in animals

is retrovirus and virus with an RNA genome?

yes

how does retrovirus work?

after infecting a host cell, the RNA is converted by the enzyme reverse transcriptase to DNA

ways how retroviruses contribute to cancer?

1. the retroviruses intergrates close to a cellular protocol-oncogene thereby cause the protocol-oncogene to be expressed abnormally
2. the retroviruses may include an oncogene, which it then brings to the cell it infects
3. the retrovirus may have a normal viral gene that stimulates cell division act as a gene-expression regulator for cancer related cellular genes.

acut transforming retroviruses

when a retrovirus may include an oncogene, that then brings it to the cell it infects

some examples o viruses that implicate in human cancers

HIV-1

Human T-cell leukemia virus

HIV-1

immune suppression

Human T-cell leukemia virus (HTLV-1)

adult T-cell leukemia and lymphoma

natural agents that contribute to cancer

natural pesticides and antibiotics

natural radiation

sunlight (uv-light)

radon gas (ionizing radiation)

natural processes in humans that contribute to cancer

human gut

mistakes during dDNA replications

Byproducts of normal metabolism

chronic inflammation (from infection)

how can the human gut contribute to cancer

creates alkylating agents which causes mutations

how does chrominic inflammation cause cancer

stimulates cell division and DNA replication which causes mutations

what percent does our diet stand at with cancer

20%

what in our diet contributes to cancer

red meat and animal fat

hormones in the food

carcinogens created during the cooking process, processing, or digestion

some preserved meats that contain nitrosamines

alcohol

how does hormones food contribute to cancer

it causes cell division which causes DNA replication which causes mutations to occur

how does alcohol contribute to cancer

it can cause liver cancer from your liver being inflamed

some chemicals do not show their affects unless they act in combination with other chemicals

true

is it difficult to estimate the effects of human made chemicals and pollutants on human cancer?

yes

why is it hard to estimate the affects of human made chemicals and pollutants on human cancer?

a substance might be mutagenic and carcinogenic in the labratory, but in real life we are exposed to much lower concentrations of the compound

how many different cancers is tobacco smoke liked to

17

whats the percent of lung cancer deaths from tobacco smoke?

70%

more than 60 different carcinogens in tobacco smoke can lead to mutations

true

lung cancer cells from smokers are aberrant DNA methylation patterns

true

what does chemotherapy do

targets many different aspects of cell biology

what does chemotherapy do in mitosis

prevents mitotic spindle from working

what does chemotherapy do in anti hormone drugs

targets signal transduction pathways which leads to no cell division

what does radiotherapy do

causes DNA damage which can cause cell death

what are the side affects of radiotherapy

usually due to damage to healthy cells that normally divide in the individual.

why can normal healthy cells handle radiotherapy better than cancer cells

because they have intact DNA repair mechanisms