4.28.20101. TRK

a. Muscle tropomyosini. Normally binds to actin filaments

ii. Functions in a dimerized form, forming a polypeptide where each of two peptides is wound around one another and Ns and Cs are aligned

iii. Interacts with actin for muscle contractioniv. In gene rearrangement, MusTrop is exchanged for EXC domain of TRK

receptor1. TRK normally binds to GFs like nerve GFs, BDNF, Neurotrophins2. Single polypeptide of Trk receptor interacts with one region of

that GF while the other interacts with another region of GF, dimerizing to make a functioning Trk receptor

v. In this example, a single polypeptide of MusTro is expressed with or instead of the EXC domain of a single Trk receptor

1. When MusTrop dimerizes, it dimerizes the receptor and bring two polypeptides together so that the cytoplasmic regions are juxtaposed

a. Autophosphorylate one another acting as if always bound by GFs

i. Oncoprotein now is continually active, activating Ras signaling and driving cell mitosis

2. PDGF receptora. Platelet derived growth factorb. GF that binds to Trk receptor under normal circumstances, turning on kinase

signalingc. In the oncoprotein form: (driving cell mitosis)

i. Tel, a transcription factor, is coded and expressed as EXC domain of the PDGF receptor

ii. Due to its structure, helix loop helix, it interacts to dimerize receptors and always on

3. Rb Proteina. Tumor suppressorb. Rb normally functions in absence of GF to bind E2F and restrict it from

promoting gene transcriptionc. GFs can activate Ras pathway

i. Stimulates signaling cascade that Pi G1 Cdk-cyclin1. Pi Rb

a. Releasing E2Fi. Drive gene transcription

1. Proteins for S phase required are synthesizedd. Heritable mutations

i. Lead to one hit on a TSGeneii. In sperm, allele is mutated

1. Now have a single copy with functioning Rb and non-functioning Rb

a. Each cell of the body has one hit on normally functioning allele

i. Required for TSG1. TSG regulate mitotic ability and not enhance

it (must have two hits for TSG)e. Mutations from external signals

i. Cells divide normally until individuals cells are mutated twice on the particular gene after fertilization in somatic cells

f. Ras Mutationi. If on always

1. Continually Pi Rb to keep cell in mitotic stateii. Point mutations of Ras and Raf lead to always on

g. Mutations don’t mean that cell will divide uncontrollablyi. P53 – guardian of cell

1. Shut cell down by upregulating ihibitors of the Cdk-cyclin proteins, going to G0

a. P21 is the Cdk inhibitori. Inhibits function of G1 Cdk-cyclins by taking up the

ATP binding site of the G1 Cdk cyclin so it can’t Pi Rb2. Upregulates PUMA

a. Binds to Bcl2i. Leads cell to apoptosis

ii. Mechanisms to recognize DNA damageiii. Tumors are loss of ability to recognize DNA damage

4. Cell Stressa. Responses of cells to stress that can be recognized by cell and lead to cell cycle

arrest or deathb. Treatment induced stress can lead to mutations that can lead to cell death

i. Can induce so much damage that the cell will die instead of mitosisii. Sometimes the treatment for cancers is to also induce mutations so much

that it will die instead of go through mitosisiii. Can cause mitotic failure

1. Instable MTs and can’t polymerize/associate with chromosomes and detach at anaphase

c. Can drive autophagy or necrosisd. Radiation or chemotherapye. Tumoregenic Stress

i. Harms cell way toooooo muchii. Limitation to GFs, oxygen and nutrients

1. Angiogenesis can deal with this lack of nutrientsiii. Immune responses

1. Though to fight tumoregenic cellsiv. DNA damage

1. There’s a limit thoughv. Oncogene activation

vi. Telomere shortening

1. Related to aging2. Progeria disease (premature aging)3. Regulate mitosis (Hayflick limit)

a. Telomere shortening causes cells to reach the Hayflick limit before senescence

b. Telomerases shorten ends of telomeres until too short to replicate cell

c. In cancer cells, telomeres don’t shortenf. In normal cells

i. EXC signal leads to DNA damage1. Repaired by p53 or other mechanisms2. Or undergoes Apoptosis

g. In cancer cellsi. Ionizing radiation causes DNA damage

ii. No cell cycle arrest if that mutation is not recognized because p53 is not functional and cell divides to become cancerous

iii. Cell can die if damage is severe1. Used for radiation therapy

5. P53a. Functioning p53 genes

i. Treating cells with chemo drugs1. Undegoe apoptosis

b. Heterozygous mutationi. Treat with chemo

1. Some cells don’t dividec. Both alleles are knocked out, no functioning p53

i. Treat cells with chemo1. Look just like normal cells (in these particular chemo agents 5-

fluorouracil, etoposide, adriamycin)d. Moral:

i. May cause secondary side effects with chemo drugs and not reducing cancer cells and may not affect tumor cells, so which treatments are best then?

6. Mutationsa. Normal cell undergoes cell division and divide to reach hayflick limitb. Successive mutations

i. Lead to oncogenic transofmraiton and then malignancyii. Cell divides with properties passed down to progeny

1. Can mutate more7. Cancer Smart Bombs

a. Try to target delivery mechanisms to cancer cellsb. There are two types of therapies of these

i. Nanoparticles1. Coated with chemo drugs (anti-cancer drugs) Docetaxel2. Also coated with proteins that act as homing receptors for these

chemo packets

a. These homing receptors will target these nanonparticle packaged with chemo drugs to specific cells of interest

3. Work like immune cellsa. Homing receprots on immune cells will target specific types

of immune cells to inflamed tissue, but to particular sites of tissue where the receptor recognizes a particular protein on surface of that cell

4. Coated with aptomers (homing receptors)a. Short RNA sequences that bind to proteinsb. Put on surface of packages/cancer drugsc. Target drug to receptors on cancer cellsd. Study: prostate cancer cells

i. Receptor: PSMA protein1. Mucosal adresin protein that has globular

domains2. RNA binds to it and delivers drug to prostate

cancer cella. Endocytosed so drug comes in and

hopefully kills prostate cell5. Docetaxel nanoparticle (np aptomer)

a. Targets prostate cells6. Can just target cancer cells

ii. Manipulates a person’s immune system1. Took melanoma patients2. Took out immune cells3. Virally infected immune cells with a virus that would express a

protein that would target them to the melanoma cancer cells4. While generating ‘super immune cells’ outside, they irradiated the

person to destroy the immune system and replaced with super immune system designed through viral infection (and cytokine activation for reproducing normal immune cells)

5. Two of 17 showed a sustained decrease in melanomaa. Considered successful and worked!

6. Benefitsa. Don’t have rejection because it’s the person’s own immune

system8. Hallmarks of Cancer

a. Characteristics of tumor cellsi. Tumor cell recruits blood vessels (increased angiogenesis as well)

ii. Cells less dependent on GFsiii. Enhanced signaling (such as kinase signaling)iv. Unregulated cell mitosisv. May become invasive to become malignant

b. Immune function contributes to tumor progression (Kim et al)

i. Study showed that they have the ability to recruit immune cells, called macrophages, that are activated in such a way that they do two things to promote tumor formation:

1. Increase in cytokine production2. Change in ECM proteins (Versican)

a. This protein (Versican) is secreted by macrophages in high concentrations and also upregulate production of cytokines

i. These characteristics favor tumor cell growth where the cells are healthier