Hallmarks of Cancer Exam 2

Hyperplasia

increase in number of cells

Hypertrophy

increase in cell size

Dysplasia

disorderly proliferation

Neoplasia

abnormal new growth

Anaplasia

lack of differentiation

Tumor

swelling; equated with neoplasia

Metastasis

The spread of cancer cells beyond their original site

Hyperplastic growth

cells differ minimally from those in normal tissues

-excessive number of cells growing
-proliferation is deregulated, but cells can still assemble into tissues that look almost normal

Metaplasia

One type of normal cell layer is replaced by another type of epithelium from nearby tissues

-minimum deviation from normal tissue
-invading cells looks normal

Where is metaplasia normally found?

epithelial transition zones where one type of epithelium meets another (ex. junction of esophagus and stomach)

Dysplastic epithelium

Cytologically abnormal cells whose nuclei have an abnormal shape and size and lack cytoplasmic features

-represents the transition state between completely benign growth and pre-malignant phase

Cells in dysplasia are packed how?

densely

Abnormal epithelial growths

large growths that can be detected by the naked eye (ex. adenomas, polyps, etc)

In abnormal epithelial growths, do the tissues invade the basement membrane?

No; typically benign

pre-invasive carcinoma

begin to break through the basement membrane and invade into adjacent stroma

Carcinomas

more advanced abnormal growths that invade the basement membrane; malignant and potentially life threatening

Neoplasms

abnormal growths of new tissue (tumor)

Ductal hyperplasia ("overgrowth")

too many cells are present

Atypical ductal hyperplasia

cells start to have an abnormal appearance in breasts (breast cancer)

ductal carcinoma in situ (DCIS)

breast cancer at its earliest stage before the cancer has broken through the wall of the milk duct

DCIS with microinvasion

Stage 1 breast cancer; a few of the cancer cells have started to break through the wall of the duct

Invasive ductal cancer (IDC)

cancer cells have broken beyond the breast duct; most common type of breast cancer

Can be diagnosed at any stage from I-IV

What are the steps of cancer development?

Initiation, promotion, progression, cancer, metastasis

What are the steps of colon cancer progression?

1. APC gene is mutated which leads to the formation of polyps
2. Subsequent mutations in genes on chromosomes 12, 18, and 17 cause the transformation of a polyp into a malignant tumor.
3. More mutations allow cells to metastasize, move to other areas and form new tumors

In 1924, Otto Warburg discovered what about cancer cells?

energy metabolism of most cancer cells was very different from that of normal cells; proposed to be the driver of tumorigenesis (proven wrong)

Tumorigenesis

development of a malignant tumor

Warburg Effect

cancer cells preferentially use glycolysis while decreasing oxidative phosphorylation

What percentage of cancer cells metabolize their glucose by glycolysis?

80%

What are the 2 potential explanations behind the Warburg effect?

1. Cancer cells within a tumor have little access to oxygen.
2. Intermediates in the glycolytic pathway can be utilized by cancer cells as building blocks in biosynthetic reactions for growth.

Do normal non-proliferating cells require biosynthetic reactions?

No

PK-M1 (glycolysis)

expressed in adult tissues and ensures that pyruvate is shuttled from the cytosol into the mitochondria

PK-M2 (glycolysis)

expressed in embryonic cells; rapidly growing normal cells and cancer cells

What are the 3 steps of Pk-M2?

1. Causes pyruvate to be shuttled to lactate dehydrogenase (LDH)
2. Pyruvate is reduced to lactate
3. Lactate is shuttled out of the cell

tumor growth depends on 3 factors:

1. Expression of PK-M2
2. High levels of GLUT1
3. High levels of LDH

HIF-1alpha

Transcription factor that is induced by hypoxia. When oxygen is present, it hydrolyzes HIF-1alpha, which triggers it for degradation

What is the average steady state population of cells in the adult body?

\> 10^13

T or F: Risk for certain types of cancer vary by country?

True

What are 2 factors that may impact cancer risk and incidence?

1. Heredity
2. Environmental (physical environment and lifestyle)

What is the overall conclusion of the mechanisms of a majority of cancers?

the factors and/or agents are external to the body that cause the cancer

T or F: Cancers often have specific, assignable causes that can be traced

True

What are the 3 competing theories of carcinogens?

Chemicals, viruses, X-rays/ radiation

What experiment showed evidence that chemicals can cause cancer and can be induced in the laboratory?

Repeated painting of coal tar condensates induced skin cancer in rabbit ears (Katsusaburo Yamagiwa)

Coal tar is found in:

condensates of cigarettes and products of combustion

Polycyclic Aromatic Hydrocarbons (PAHs)

A class of carcinogenic substances produced during cooking when there is incomplete combustion of organic materials

What virus had the hypothesis that viruses caused leukemia and cancer in chickens?

Rous sarcoma virus

Evidence showed that \_____-induced cancers represent the minority of cancers.

virus

physical and chemical carcinogens act as \___________.

mutagens

X-rays and chemicals can cause cancer by their ability to \__________ genes.

mutate

Theodore Boevri proposed that chromosomes, that were thought to hold genes, were \_________ in cancer.

defective

Philadelphia chromosome

An abnormal chromosome produced by translocation of parts of the long arms of chromosomes 9 and 22.

Ames test

Quantitatively assess the potency of carcinogens to mutate bacteria

Procarcinogens

compounds or substances that can lead to the formation of cancer cells

In aerobic conditions, glycolysis yields:

36 molecules of ATP/glucose

In anaerobic or hypoxic conditions, glycolysis yields:

2 molecules of ATP/glucose because the pyruvate is reduced to lactate and secreted from the cells

Johannes Grib Fribiger proposed: \___________.

He reported that stomach cancers in rats were caused by spirochete worms, which was discredited, why?

cancer is an infectious disease

tumors were metaplastic stomach epithelium caused by extreme vitamin deficiency

What did Dulbecco and Rubin state about Rous sarcoma virus stocks?

the stocks can transform chicken epithelial cells in a petri dish and immortalize cells

Virtually all compounds that are mutagenic are \_____________.

carcinogenic

Not call compounds that are carcinogenic are \____________.

mutagenic

What are 2 ways carcinogens act through?

1. mutations of DNA
2. non-genetic methods (ie. promoters)

Many mutagenic compounds are found in what diet?

Western diet

What are some difficulties in proving that foodstuffs are carcinogenic?

- Dietary plant and animal foodstuff is made up of thousands of diverse chemicals in different concentrations
-Most chemicals er converted to other products in the stomach and liver after ingestion
-Mutagenicity of various compounds differ on various cells due to metabolic differences

What is one of the complications with the Ames test?

many carcinogens fail the test and may be non-mutagenic

tumor suppressor genes

make proteins that stop cell division and kill cells

Oncogene

cancer causing gene; promotes division

DNA repair genes

repair DNA mutations

\_____________ are altered versions of normal cellular genes that when mutated or deregulated lead to the hallmarks of cancer.

Oncogenes

What are 3 common oncogenes?

1. Ras (GTPase)
2. Myc (transcription factor)
3. Receptor tyrosine kinases (RTKs)

What are 3 common tumor suppressors?

1. p53 (transcription factor)
2. pRb (cell cycle protein)
3. PTEN (lipid phsphatase)

Somatic cells

body cells

Cell cycle is regulated at 3 main checkpoints which are...

1. G1/S Checkpoint
2. G2/M checkpoint
3. M Checkpoint

G1 to S transition checkpoint

cell enters S phase of cell cycle or exit to G0

G2/M transition checkpoint

ensures DNA has been replicated and any DNA damage has been repaired

M checkpoint

Monitors attachment of spindle fibers to chromosomes

What are the 2 classes of cell cycle regulatory genes that are mutated in cancer?

1. Tumor suppressor genes (encode proteins that turn off cell division)
2. Proto-oncogenes (encode proteins that turn on/ increase rate of cell division)

RB1 protein mutation leads to:

retinal, bone, lung and/or bladder cancer

RB1 gene controls what checkpoint?

G1/S

pRB

master brake of the cell cycle, inhibits transcription

APC protein

tumor suppressor; plays an important role in Wnt signaling pathway

Wnt pathway

pathway regulates/controls cell proliferation

What is RNA-seq?

It is a technique that provides information and analysis of the cellular transcriptome

What is an advantage of using RNA-seq over microarray analysis?

ability to look at alternative gene spliced transcripts, post-transcriptional modifications, gene fusion, etc.

What is chromatin immunoprecipitation (ChIP)?

technique used to identify DNA sequence that transcription factors and chromosome associated proteins bind to

Single-cell sequencing (SCS)

Technology that can provide DNA or RNA sequence information from a single cell as opposed to sequencing the genomes from a collection of cells

What are the mouse models used for cancer research? (4)

1. Mutant mice
2. Knockout mice
3. Transgenic mice/ knock-in mice
4. inducible mouse models

What mouse model is used to study colorectal cancer?

APC^min/+ mouse

APC^min/+ mouse model

Heterozygous for a mutation in Apc gene

Cre-lox recombination

involves knocking out a target gene only in a specific cell type. Uses Cre recombinase (topoisomerase) to cause recombination between loxP sites. Turn off genes via inversions or deletions, depending on orientation of loxP sites.

LoxP sites

DNA recognition sites recognized by Cre recombinase, used in Cre/loxP Recombination Systems to bookend genes of interest for manipulation

To excise DNA: loxP sites are in the same orientation

To flip DNA: loxP sites are in opposite orientations

CRE mechanism

1. Cre protein recognizes and binds to 13-bp palindromic regions in the LoxP site to form a dimer
2. The dimer binds in a second LoxP site to form a tetramer

3. DNA strands are cut by Cre and rejoined by ligase

Inducible Cre-LoxP recombination

tissue specific Cre is fused to modified ligand binding domain of the estrogen receptor

Treatment using Tamoxifen activates \_____, exposing NLS. This allows Cre to enter the nucleus to catalyze LoxP site recombination.

Cre

Xenograft models

Most heavily utilized preclinical models to evaluate anticancer therapeutics

Patient derived xenograft (PDX) are used for what?

to create an environment that resembles the natural growth of cancer. Tissues from a patient's tumor are implanted into an immunodeficient mouse

chimeric mice

composed of at least 2 genetically distinct cell lineages originating from different zygotes

RB is located in the \_________ of the cell. While there, it binds to \_____, which is a promoter for transcription.

nucleus; E2F

Floxing a gene

putting a loxP on either end of a gene

How can expression of GFP be studied?

Using a stop codon, crossing it with a mouse that is promoting GFP, which causes the mouse to turn green.

KRAS G12C

single point mutation that favors the activated state of KRAS, amplifying the signal pathways leading to oncogenesis.

EcoR1

restriction enzyme that allows you to cut a gene in either direction