BISC305 Chapter 16

Treatments for malignant gliomas

- Almst no maligant gliomas are cured by surgery, but many of us believe that the more you get out, the more changes that the next treament of chemo and radiation will work because theres less of a tumor to fight - Typical radiation for this is 5 days a week for a month and they use 3-D imaging techniques that narrowly deliver the beams to the tumor, affecting as little surrounding tissue as possible. Experts said that surgery could give subsequent treatments a better chance of working

Colon cancer

- Best defined cancer genetically - Mutations in the APC tumor suppressor TF occur in most colon cancer, so it is thought to be a first event in many colon cancers - Mutations in p53 tumor suppressor TF occurs only at later stages - PRL3 tyrosine phosphatase is overexpressed in late progression cells when they become metastic but its specific function is unknonw

Genetic of cancer

- Cancer afflicts 1 out of 3 people so it is a common disease by transformation of cells to being cancerous is a rare event - Gene mutations that result in cancer occur is only about 1/3 of the human population during a lifetime - The human body contains trillions of cells, billions of cell divide every day, must have muliple gene mutations to become a transformed cell

Proposed orgin of malignant tumors

- Cancer can arise by mutation in cells in multiple different stages along the differentiation pathway

common changes in cancer cells

- Cancer cells are immortal. Normal cells have a finite number of divisons (around 50) thought to be due to loss of telemorase enzyme - Aneuploidy- controversy whether is cause of genetic instability or consequence of abnormal growth - Suppression of apoptosis - Disappearance of normal cell surface components - Appearance of new cell surfacce componants. GF receptors - Loss of adhesion to other cells and to ECM - Increased motility in culture and in vivo, GBM good example - Lack of serum dependance eg. consitutively active Ras - Loss of anchorage dependance (integin-ECM interactions). Cell can grow in soft agar or methycellulose - Changes in cytoskeleton, like disorganization of MTs

Cancer in the US

- Cancer deaths in the US in 2006 559,888 - Lung cancer deaths- 158,664 (28.3%) - Lung cancer is the leading cancer in both men and women in the US - Lung cancer causes more deaths than the next three most common cancers combind (lyphoid, colon, and breast) - Smoking causes the vast majority (90%) of lung cancer deaths - Therefore, 25% of all cacner deaths are totally preventable

Cancer and genetics

- Cancer is not a genetic disease, but it is caused by the mutation of specific genas - Cancer is mosly not inhertied, some genetic mutations are inhertied, which predposes indivuads to cancer - Identical twins will have a 10-15% chance of developing the same type of cancer by age 72, genetic, so genetis plays a minor role - Genetic mutations arise in somactic cell DNA during ones lifetime, variety of causes, some preventable - Cancer cells proliferate uncontrollable (primary caracteristic) - Malignant dealthy tmors often metastize to distant secondary sites via blood or lyphatic vessels - Healthy tissues in invated by cancer celles, Local invasivesness can be cause of mortality

Retinoblastoma

- Cancer of the retinal cells in the eye. Mutation om the RB genes - There are two pattens that occur there are high frequency in chrildren in some families and low frequency in adults - Also RB gene is commonly mutated in breast, lung, and prostate cancer - Reintroduction of normal RB gene back into transmformed cell in vitro causes loss of transformed phenotype

Genes altered in cancer affects

- Cell cycle progression - Cell adhesion - Apoptosis - DNA repair - Different types of cancers typically have different combinations of mutated genes - Even a specific type of cancer can have a great variability of mutated genes - The most common cancers like breast, colon, prostate and lung carinomas arise in epithelial tissues that are constantly diviing

Rb mutations

- Certian mutations in the RB gene causes a loss of the ability of pRb proeitns to bind to E2F and repress transcription - This causes cells to cycle continuously --> tumor formation - More than 40 protiens bind to pRb which suggest that it also carries out many other unknown fuctions which are disturbed when the cell is mutated some DNA tumor virsues like SV40 and adenoviruses encode protiens (large T-antigen) that bind to pRb, which blocks pRbs ability to bind to E2F, which causes continuous cycling

Tumor suppseor genes mutatuions

- Have to be both copies to cause loss of growth control - Mutations are loss-of-function vs a change in function)

Progression of gene altercations

- Mutation occurs that make cell less responsive to growth control - Cell becomes more motile - More mutation accumulate in cancer cell that results in even less control

Oncogenes mutations

- Mutation of 1 of the 2 copies of an oncogene may be sufficient to cause a loss of growth control - Mutaitons are gain-of-function (they now gain the function to control the activity of the gene) - Oncogenes lead to Genetic instability Rescue from apoptosis Increased motility and metastasis

Effectos of serum deprivation of normal vs cancer cells

- Normal cells depend on growth factors like EGF and insulin to divide to divide in cluture wich is supplied by serum, stimulates the MAPK pathway - Cells can deplete the meida of growth factors or become confluent and stop dividing - Cancer cells do not need these stimulatory factors to divide in culture

Growth properties of normal and cancerous cells

- Normal cels grown in culture grow as a monolayer unti they reach confluecy. They then will become contact-inhibited and stop dividing - Cancer cells do not stop growing and form clumps or foci. They are not contact-inhibited - Cancer is uncontrolled growth of cells, bu where they also spread

Metastasis to another organ

- Primary tumor must grow and cancer cells must detach and invade (intravasate) blood vessels or lymph vessels - Cells must successfully travel through blood or lymph to distant site - Cells must exit (extravasate) vessel and invade into new tissue or organ like brain. - Cells must grow to form secondary tumor

Proto-oncogenes

- Protiens that have various functions in cells, whose activites are normally tightly regulated

Role of pRb protien in controlling the cell cycle

- RB gene encondes the pRb protein which regulates the cell cylce - It regulats the transition from the G1-S transition - This transition commits the cell to go though cell cycle and divide - Time of activation of DNA polyerase, cyclin E, and histons

What it can be used to detect

- This type of analysis can be used to detect differences in gene expression between different types of tumors, which can aid classification as opposed to simple pathological appearance - It can tell you what cell signaling pathways have been turned on or off - It can provide a list of genes to look at as targets for therapeutic drugs

From primary tumor

- Tumor can be removed, dissociated into single cells, and cultured. This can lead to teh estavlishment of cancer cell line

Brian tumor types

- more than 120 types of brain tumors - World health organization calssifaction system is the system that most medical instituaitons use - WHO will classify by cell origin and how the cells behave from the for the least agressive (benign) to the most aggressie (malignant) - Some are given a grade which will range from 1-5, five being the worst, which signifies the rate of growth and invasion

Modle of the p53 funtion

- normal cells dont have a lot of p53 the levels are very unstable - DNA damage increased p53 level by increased stability, causing G1 arrest (via p21) or apoptosis (via increased expression of or binding to Bax) - When both copies of p53 are mutated results in no arrest of DNA is damaged, and mutated cell either divides into tumor or fails to divide and dies

DNA damage checkpoints

- p53 is a transcription factor that activates many genes involed in the cell cycle and apoptosis - DNA damage will activate ATM kinase, which activates Chk2 checkpoint kinase, that stabilizes p53 transcription factor form degradation, which causes expression of p21, which inhbits G1-CDK which cuases cell cycle arrest in G1 so DNA can be repaired - The mutation and inactivation of p53 results in no cell cycle arrest, so damaged DNA does not get repaired - Produces more and more cells with abnormal DNA

p53 Guardian of the genome

- p53 is a tumor suppresseor gene, perhaps the most important - Mutations occur in breasts, brain, and leukemia cancers - Individuals with a sinlge inherited p53 mutaton have Li-Fraumeni syndrome, which prediposes them to high incides of the aboive cancer. second sporative p53 mutation causes cancer (just like RB)

Breast Cancer

1 in 8 women are stricken by breast cancer in the US - 5-10% are due to inheritance of a gene that predisposes them to it (= minor, but important factor) - BRCA1 and BRCA2 genes were identified as the mutated genes in the majoiryt of these inherited predisposition to breast cancer - These also predispose women to breast cancer - BARCA1 and 2 are genes found to be mutated in inherited, but not sporatic brest cancer - Precies BRCA gene function is still unclear

DNA damage, repair, and apoptosis orger

1. DNA damage can cause double stranded breaks 2a. Breaks normally repaired by complexes with BRCA1 and BRCA2 protiens 2b. Mutations in these proteins can caused failed repaire 3a. Failed repare activated p53 system 3b. p53 is normally inhibited by MDM2 protein by causing p53 degradation 4a. Activated p53 can cause expression of p21 and cell cycle arrest 4b. Or it can cause and or expression to Bax and apoptosis Apoptosis is a primary mechanism of eleiminating potential cancer cells

Proteins encoded by proto-oncogenes

1. Growth factors, 2. Growth factor receptors, 3. Protein kinase, 4. Cell cycle regulators, 5. Apoptosis regulators, 6. Transcription factors Appears that all levels of signaling pathways that control - Proteins involved in mitosis tissue invasion, and metastais are not shown, but could be

Mecanisms of proto-oncogenes to oncogenes

1. Ptoto-oncogene can be mutated to cause altered protein structure or funciton 2. Mutations in the regulatory region or gene duplications can cause increased expression 3. A chomosomal rearrangemtn can increase expression or cause abnormal fusion genes 4. Retroviral insertion next to gene cause increased or unregulated expression

Angiogenesis is imporant for tumor growth

1. The transformed cell proliferates into small tumor, will stay small if it remains without blood vessels 2. Tumor produces angiogenic factors that attract blood vessels to grow into it 3. Tumor becomes vascularized and os now capable of unlimited growth and metastasis to distant sites

Benign tumor

Before malignant prgrresion, cells sometimes forma benign tumor which has controlled growth, but is not invasive or metastatic - Melignant progression in cervical cancer takes >10 years

Cancer Stem Cells

CSCs must be present and motile for metastasis CSCs are resistant to treatments CSC are thought to be able to arise from DNA mutations that occur in 1. Differentiated cells 2. Neural Stem Cells 3. Committed Progenitor Cells CSCs self-renew, but mostly give rise to hererogeneous cells types within a GBM

Premalignant cells

Can sometimes be identified by their moprhology, in pic it has large nucluius

Monoclonal

Cancer is monoclonal, events that cause a cell to become cancerous generally happen in a single cell in an individual, that then expands to a tumor - Malignant transformation requires multiple gene altercations to have occurred in the same cell

Leading causes of death

Cancer is number two leading cause of death, 559,888 which is 23% of all deaths

Transforaiton of normal cells

Cells can be transformed by using carcinogenic chemicals, radiation, or tumor causing virsues. These cells will grow indefinitely, like naturally occuring tumor cells. Injection of these cells into a animal will often form tumors. This can also lead to the establishment of cancer cell lines, but their properties may be different from cell lines made from primary tumors

p53 in treated cells

Cells with 2 normal p53 genes die when mutated with chemotherapeuric agents because they enter apoptosis - Cells that have mutations on p53 wont repond or will respond porly to these chemotherapeurtic agents because they cannot be trigged into apoptosis by p53 (since its not functioning) or it will not halt cell cycle to repair DNA

Causes of Cancer DNA

DNA- mutagens- alter the DNA genome Chemical carinogens- in soot, in cigarette smoke, in grilled meat, benzene Ionization radiation (skin cancer)

Oncogenes

Encoded proteins that promote loss of growth control and promote transformation. They arise by mutation or activation of normal cellular proto-onogenes. Which are involved in normal cell function. Only one copy of these genes needs to be mutated or activated to gain uncontrolled funciton

Human Glioblastoma Multiforme

GBM is devived from stem/progenitor cells or glial cells. - GBM is an exaple of a highly mobile cancer in brain, which makes it extremely letha becuase of local invasiveness

5 year survival rates of malignant brain cancer

Glioblastoma multiforme (Grade 4) 3.4% Anaplastic astrocytoma (Grade 3) 30% Anaplastic Oligodendroglioma (Grade 3) 42% PNET/medulloblastoma 55% Oligodendroglioma (Grade 1 or 2) 70% Ependymoma 70% Pilocytic astrocytoma 91% Brain tuomors are the second leading cause of cancer-realted deaths in children under the age of 20

Sporadic adult version

Is low frequency in older general population. Mutations in both gene copies occurs randomly.

Stem and progenitor cells

It is thought that the diving stem or progenitor cells acculate the mutations that are required for malignant transformation - Adult stem cells are tough to be the primary cells of origin of many types of cancer because they have time to accumulate mutations

Inherited RB

Just one of these mutated gene will not cause cause, only one sportadic mutation in the second RB copy is necessary to develop cancer

IRS activate signaling pathwasy

MAPK cascade is very important - Ras MAP kinase pathway causes transcriciption of genes involed in proliferation (cyclin D1) - Cancer can be caused by mutations in Ras, Raf, c-fos, c-jun, RTKs (EGRF, PDGFR) - Mutations in Ras found in about 30% of human cancers. Mutations prevent hydrolysis of GTP to GDP, so actvates Raf and MAP kinase cascade. Mutations in GAPs can also keep Ras active (no GTPase activity)

Genes that control carcinogensis

Many genes that are altered in carcinogenesis can be placed in 2 broad categories

Cancers of p53

More than 50% of all human cancers have mutations in bother copies of p53, and more than 1000 different mutatiosn in p53 are known - Elimination of p53 function is an important step in the progression of many cancer cells towards the fully malignant state - p53 levels rise in cells with damaged DNA, causes transcription of p21, which inhibits Cdk to remain in G1 phase until DNA is repaire - High levels of p53 can also activate apoptosis by upregulating Bax gene

Tumor suppressor genes

Most act as negative regulators of cell proliferations - There are about two dozen tumor suppressor genes Transcription Factors: APC, BRCA1, p53, WT1 Cell cycle regulators-RB, p16 Signaling regulators: NF1, PTEN - Some mutations are widespread, other specific - You cant inherit cancer, but may inherit mutations, this means it just requires one less mutation in tumor suppressor genes to get cancer

Mutations in p53 gene

Most mutations on p53 are at a place on p53 that interacts with DNA

Tumor suppressors and oncogenes working together

Most tumors contain alteration in both oncogenes and tumor suppressor gene. Cells with active oncogenes still do not become trasformed if they have normal tumor suppressor genes. As many as 7 different genes must be mutated in colon cancer to become fully malignant

Mecahnisms of antion of cancenomaq

Mutations shown in DNA sequence of p53 tumor suppresor gene - p53 is mutated in about 50% of cancers - Chemical agents or UV irradiation cause distinct nucleotide subsitutions - Normal metabolic processes can also lead to deamination and nucleotide subsitution

High risk verison

Occurs in 90% of childhood fmaily members, therefor a dominant trait. Also at high risk for develping sarcomas - One RB mutation is inhertied by must devlop mutation in other copy to develip cancer, 10% never develope mutation and rteinoblastoma

Primary GBM and sconday GBM

Primary is just full blown GBM without any progression, Secondary GBM will progress from lower grade, thee are not meatstatic (will not spread)

Incident and mortality by cancer type

Prostate cancer incident is very high by mortality is low (14%) Lung cancer incident is high, with high mortality (86%) - Pancrate anc brian ceancer indcien is low, but very deadly (90%)

Oncogenes detail

Remember oncogenes are derived from proto-onogenes, which have functions in normal cells - about 100 oncogenes have been identified, but only about a dozen play a role in human carcinogenesis - RAS GTPase is the oncogene mutated most often in human cancers - Other oncogene encode growth factors, protein kinase, growth factor receptors, protein kinases, transcription factors, and apoptosis regulators - Some are cancer-specific, indicating the importance of certain pathways in those cell types

Familial adenomatous polyposis cali (FAP)

Results in hundreds or tohughts of premaignant polyps (adenomas) - These people inherit a mutation on the APC gene and the spoadic mutation of the other copy reults in Polys - APC mutations are also found in 80% of sporadic colon tumors - APC is a tumor suppressor protien that inhibts transcription of genes (eg. MYC) that stimulate cell proiferation. Action is conplex

Karyotypeing cancer cells

Shows highly abnormal chomosomes - Cancer cells are often aneuploid with highly aberrany (differnt) chhromosome pairs that are suppose to be identical....they can have - extra ones, missing ones, rearranged ones - A normal diplod would have 22 pairs of autosomes and 2 sex chromosomes - Above breastcancer cell line is aneuploid, chromosomes should be single color, multicolored chromosomes have large translocation of DNA - These abnormalities noramlly would have triggered apoptosis in normal cell cycle checkpoints. Cancer cells have overcome thesecheckpoints

DNA microarrays for detemining treatment

The earlier that a cancer is discovered, the more likely a person can be cured, this isnt always true because some release metastatic cells early on - Prognosis for breast cancer can be revealed in the expression levels of 70 selected genes by microarray analyses - Graphs show that lymph ode metastases are not good indicator of patient survival whereas classifcation based on the 70 genes is a good prognostic indicator. It will also indicate how aggressive the treatment should be

Gene expression profiling

There are around 35o genes that have a causal role in development of cancers - Monitoring gene expression in cells is an important tool for diagnosing different cancers - DNA microarrays are made by placing thousands of spots of DNA from known genes on a slide - cDNAs are made from tumor cells, fluorescently labeled, and hybridized to slide - Colors different depending on expression levels

CNS tuomors classifcation

They are classified by their normal cell counterparts Cell types inside the cell like astrocyes and neurons, oligodendocytes, ependymal cells

Causes of cancer RNA and viruses

Tumor viruses- only a small fraction, mostly increases risk of developing cancer, not directly DNA- polyoma vius, SV40, adenovirus, herpes-like viruses RNA- retorviruses carry oncogenes to v-src, or they insert next to proto-oncogene in genome and activate it There are no known risk factors for brain cancer

In adult

When you have two normal RB copies then you have no cancer Must have 2 indepednet mutations. Takes a long time so only in older adults - It will take until later in life to get 2 independent mutations

Tumor suppressor gene

encode proteins that restrain cell growth and prevent cells from becoming malignant. Mutations can cause loss of growth control. Both copies of these genes must be mutated to result in loss of their function

New brain/cerntal nervous

form 1980-2000 there was an increase of nearly 50% in the estimated number of new cases of malignant brain/central nervous system tumors in the United States

pRb in the cell cycle

pRb normally will interact with E2F transcription factor to repress transcription of multiple gene that are needed for the cell to move from the G1 to S phase - Activation of cyclin-depedent kinas (Cdk) at the end of G1 causes phosphylation of pRb and dissociation from E2F - E2F activates transcription - Many proteins needed for G1 to S phase transition are expressed (ex. cyclin E and DNA polyerase - G1 to S transition occurs

Enviornment factors

there are many differnt enviornment factors the are importnat, example with japanese ppl coming over