Human Cancer

What are the 3 primaries ways by which growth factor independence can be achieved?

(1) activate the receptor, (2) activate downstream signaling components, and (3) make more growth factors.

A greater number of surviving colonies following an Ames test would indicate a compound that is more mutagenic A. True B. False

A

Both cyclins and Ras are examples of regulator proteins that can bind to and activate kinases A. True B. False

A

Given its function, ERK is very likely to be a potential proto-oncogene A. True B. False

A

Given its function, Mdm2 is very likely to be an oncogene A. True B. False

A

Overexpression of growth factor receptors helps to promote cancer growth by: A. Increasing the likelihood of spontaneous dimerization B. Turning off downstream signals C. Increasing the requirement for growth factors D. Leading to spontaneous translocations E. None of the above

A

Sporadic retinoblastoma requires "2 hits" to progress to cancer while the familial disease requires only 1 hit A. True B. False

A

Which feature of a tumor, once identified, would ensure that you are looking at a malignant tumor rather than a benign tumor? A. none of the above B. a large visible mass C. cells with an abnormally large ratio of nuclear to cytoplasmic volume D. dysplasia E. a combination of hyperplasia and dysplasia

A

Which of the following types of alterations would likely be associated with an increase in the proliferative features of cancer? A. elevated expression of an EGF receptor B. both elevated expression AND truncation of the cyptoplasmic domain C. inability of an EGF receptors to dimerize D. truncation of the cytoplasmic domain of an EGF receptor E. all of the above

A

What type of experiment could you employ to test whether a specific kind of cancer was mostly the result of environmental influence or heredity?

An experiment that can be done is to follow genetic populations and look at ones that move to a different environment. For example, the Osaka Japanese versus the Hawaiian Japanese.

A mutant mouse that has a constitutively active Rb protein would be highly prone to cancer A. True B. False

B

A tumor that arises from connective tissue/stromal cells is called A. Carcinoma B. Sarcoma C. Leukemia D. Adenocarcinoma E. None of the above

B

Cancer is a monoclonal disease and thus is particularly hard to treat A. True B. False

B

The most commonly phosphorylated substrates for the receptor tyrosine kinases are the proteins Src and Ras A. True B. False

B

Why would mutating the DNA binding domain of 1 copy of p53 produce a stronger pro-cancer phenotype than eliminating 1 copy completely?

Because p53 mutation in the binding domain is dominant, one mutation would give 1/16 activating unit whereas eliminating 1 copy completely would still give you a half active p53 of all good subunits.

Why is FdG PET less useful for identifying a glioblastoma than a carcinoma?

Because the brain in general uses a lot of energy so all of it already looks lit up like cancer.

What is the differences between a benign and malignant tumor? Explain the progression from benign to malignant.

Benign tumors are slow growing, well differentiated, encapsulated, remains localized, and rarely kills the patient whereas malignant tumors are fast growing, poorly differentiated, have irregular boundary, and are spread by invasion (passing through the basement membrane) or metastasis (entering circulation and colonizing distant sites). The progression from benign to malignant: (1) early stage aka hyperplasia, (2) transitional stage aka dysplasia, (3) premalignant stage, and (4) malignant stage.

What do Src activation and H-Ras activation have in common?

Both are kept in an off-state in the cell normally but cancer turns it always on.

Cyclin D-CDK4/6 complexes can be inhibited by: A. p27 B. p21 C. p15 D. Rb E. None of the above

C

Which of the following would be necessarily define as malignant? A. Papilloma B. Dysplasia C. Lipoma D. Squamous cell carcinoma E. Adenoma

C

What is the difference between cancer and a tumor?

Cancer is a disease in which abnormal cells of the body divide uncontrollably and infiltrate other parts of the body. A tumor is an abnormal mass of tissue that results when cells divide more than they should or do not die when they should.

What does it mean to say that cancer is a disease of "anti-social cells"?

Cancer is a disease of "anti-social cells" because the cells no longer communicate with each other and therefore proliferate more than they should in the space allotted.

Which of the following is NOT true: A. cancer of the muscle would be classified as a sarcoma B. all of these are true C. carcinomas derive from epithelial cells D. carcinomas are generally, but not always, of polyclonal origin E. carcinomas are the most common cancer type

D

Experiments using temperature-sensitive mutants of RSV to infect chicken fibroblasts demonstrated that: A. cells infected with RSV generally continue to exhibit normal morphology unless ALV can also activate oncogene expression via insertional mutagenesis B. infection of cells with RSV is necessary to initiate transformation of these cells. While the RSV genome is required for this process, the gene products of the RSV genome don't need to be active to maintain the transformed state of the cells. C. infection with RSV alone is unable to transform cells in culture D. infection with RSV is necessary to initiate transformation of these cells, but the RSV genome is not required to maintain the transformed state E. none of the above

E

Which of the following is NOT a transcriptional target of E2F? A. Rb B. E2F C. Cyclin E D. Cyclin D E. Both Rb and Cyclin D are not targets

E

What are epithelial cells and their general features? Why are epithelial cells so susceptible to malignant transformation?

Epithelial cells are sheets of cells that cover internal or external surfaces. They interact with the outside world ("interface tissue").

How can growth factor independence be tested experimentally?

Find the protein that is binding to the cell surface, isolate, and sequence that protein. The general difference is a glycine to valine change at position 12. The activating mutation disables the GTPase activity of Ras and locks it in the ON state.

Why does glycolysis occurs at such a high rate in cancer?

Four main reasons: (1) very fast source of energy, (2) glycolytic intermediates can be used for macromolecular biosynthesis, (3) adaption to hypoxia, and (4) lactic acidosis favors immunosuppression.

Under what circumstance can human cancer cells be injected and form a tumor into mice? (Hint: what kind of mice need to be used for this to work?)

Human cancer cells can be injected into the fibroblast cells of an immunocompromised mouse (usually they are hairless).

What is the relationship between autocrine signaling and the development of growth factor independence?

In both cases, you don't need to rely on signals from other cells.

How can chromosomal translocation be relevant to both mechanisms (increased expression and altered protein structure) of proto-oncogene activation? Know a specific example for each.

It can increase ligands which increases the likelihood of them colliding and dimerizing. Ligand-independent truncation so it's always on regardless if there is a signal.

Explain how an oncogene can act pleiotropically to drive cancer progression.

It is able to act pleiotropically because it is situated upstream of many targets.

Suppose you treat the membrane of a cell with a drug that prevents PIP2 lipids from becoming phosphorylated into PIP3 lipids. Would this cell be more or less prone to becoming transformed? Explain your answer.

It would be less prone to becoming transformed because ATK would not be able to go through its pathway.

What is the basic difference between leukemia and lymphoma? Which mutations in which cell type would likely produce chronic leukemia vs acute leukemia?

Leukemia occurs when either lymphoid (LL) or myeloid (ML) progenitor cells develop mutations. Acute leukemia is when the mutation happens to the progenitor cells and chronic leukemia happens to the "-blast" cells. Lymphoma is the cancer of mature lymphocytes. It creates a solid tumor, which is localize to lymph nodes and characterized by painless swelling.

What are the differences between the way normal cells and cancer cells behave in a petri dish?

Normal cells would be contact inhibited, need to grow attached to solid substrate, have a finite number of divisions, require external growth factors, have low saturation density, and not be able to form tumors if delivered in vivo. Cancer cells would not have contact inhibition, have anchorage independent growth, be immortal, be able to grow in the absence of external factors, have a high saturation density, and be able to form tumors if delivered in vivo.

How can cancer be classified by its tumor of origin? What are the basic differences between carcinoma, sarcoma, hemotopoietic malignancies, and neuroectodermal tumors?

Pathologists classify tumors by two factors: (a) the presumed cell type and tissue of origin and (b) the degree of malignancy: benign versus malignant. Histological analysis is the easiest and quickest way to accomplish this. Tumors can now be sequenced to reveal the underlying genetic mutations. Epithelial cells = carcinoma (most common ~80%) Connective tissue/mesenchymal cells = sarcoma Immune cells = hematopoietic malignancies (leukemia, lymphoma) Nervous system = neuroectodermal tumors

How can RSV promote cell transformation and how this could be tested experimentally?

RSV can transform cells by integrating its viral genome and creating viral proteins. Viruses are not a "hit and run", they need to stay and that is shown by shifting the temperature to make the viral protein inactive.

What is the basic difference in the genome of RSV vs ALV?

RSV has the src oncogene whereas ALV has the myc oncogene.

Why is RSV strongly transforming and ALV weakly transforming?

RSV is strongly transforming because it just needs to be inserted into the cell's genome and because src acts pleiotropically, it doesn't have to be specific. On the other hand, ALV's myc gene has a very specific place it needs to be inserted or it won't become oncogenic.

How can autocrine signaling promote cancer? Know the example for this that we discussed in class. (e.g the Sis oncogene)

Since it's self signaling, it doesn't listen to other cells. Sis uses itself to signal it's growth factors and is derived from the PDGF gene. It only transforms cells that have the PDGF receptor to which the Sis protein can bind.

What are the primary implications from the realization that Src is found in all normal (non-transformed cells) cells?

Src is part of our normal cells. Since it can be transformed from a proto-oncogene to an oncogene, all of our cells that have Src in it have the ability to become cancerous. (1) a normal gene can be converted into a potent oncogene if it was associated with a virus, (2) a single gene could cause all of those transformation features that we saw previously with cells in culture, (3) maybe RSV/Src represented a model by which other viruses could cause cancer, and (4) maybe the cellular genes could be activated in different non-viral ways to get cancer.

What is the Ames test? What is the difference between the first and second versions of the Ames test? What limitations still exist even in the second version of the test?

The Ames test is trying to understand how carcinogens and mutagens transform normal cells. In the first test, histidine, which is needed for bacteria to grow, was missing. Whatever colonies grew meant that the cells had mutated so they did not need histidine. In the second Ames test, some homogenized rat liver was added to the mix because compounds become mutagenic after being processed in the liver which represents a human model more closely. However, even this test still has its limitations which include not having interaction with cells and other complex pathways in the body, being in a laboratory environment, having a culture medium that could be affecting it, and the possibility that this compound would not be normally metabolized by the liver.

What are the pros and cons of using a cell culture model to study cancer?

The pros of using a cell culture are that you can recapitulate many of the features of cancer in vivo, your use of animals is reduced, you will have easy genetic manipulation, you will have homogenous cell population with the same growth requirements, you will have control of the extracellular environment, and you will minimize interference from other biological molecules that occurs in vivo. The cons of using a cell culture are it is impossible to re-create an internal environment. Specifically, you remove the interaction with other cells, hormones, and support structures. These artificial conditions could cause cells to de-differentiate or change phenotype.

What are the original 6 hallmarks of cancer?

The six original hallmarks of cancer are sustained proliferative signaling, evading growth suppressors, activating invasion and metastasis, enabling replicative immortality, inducing angiogenesis, and resisting cell death.

What are the mechanisms by which RTK's can be altered to create oncogenes and be able to provide an example for each?

Truncation of the ectodomain which creates ligand-independent activation. A point mutation in tyrosine kinase domain which causes constitutive activation. Formation of a fusion protein which is where the gene for the RTK Ros has become accidentally fused to the gene for a random unrelated protein called Fit that has a high tendency for dimerization.

Do unicellular organisms get cancer? Why or why not?

Unicellular organisms do not cancer because it has to do with cell signaling and being social with each other. If there were just one cell, cancer would not make sense.

In which ways can viruses convert a proto-oncogene into an oncogene and be able to provide specific examples that we discussed in class?

Viruses can convert a proto-oncogene into an oncogene by turning the oncogene on all the time to it overexpresses through gene amplification.

What is the relationship between DNA mutations and the development of cancer?

When DNA mutates, usually more than once, cancer develops. Cancer is a genetic disease!

What are the 4 main themes of oncogenes that Src helps to exemplify?

(1) Oncogenes are often genes that are involved in cell growth and proliferation pathways. (2) Oncogenes often act pleiotropically by affecting multiple downstream targets simultaneously. (3) Oncogenes are often activated by bypassing auto-inhibitory components. (4) Oncogenes often fall into cell surface receptors, kinases, and transcription factors.

Given its function, Bcl-2 is very likely to be a tumor suppressor. A. True B. False

B

Given its function, Ras-GAP is very likely to be a potential proto-oncogene A. True B. False

B

Increased DNA methylation at promoters generally increases the expression of the downstream gene A. True B. False

B

Oncogenic mutations in H-Ras are most often the result of A. point mutations resulting in premature stop codon B. point mutations that change the protein's structure resulting in constitutive activaiton C. insertion of extra bases in exon1 of the gene D. frameshift mutations E. none of the above

B

RSV generally causes cellular transformation by inserting upstream of a nearby proto-oncogene A. True B. False

B

Release of Cytochrome c from the mitochondrial membrane is stimulated by: A. Bcl-2 B. Bax C. Caspases D. Checkpoint Kinases E. None of the above

B

Translocations can cause cell transformation by reducing the number of dimerized RTKs A. True B. False

B

Which of the following best characterizes the role of NF-1 in cell signaling? A. It elevates Myc activity B. It inhibits Ras activity C. It converts PIP2 into the PIP3 lipid D. It converts PIP3 back into PIP2 E. None of the above

B

Which of the following is NOT a property of transformed cells? A. loss of contact inhibition B. increased requirement for growth factors C. all of the above are properties of transformed cells D. colony formation in semi-solid media E. immortality

B

Which of the following is not an example of loss of heterozygosity (LOH)? A. Mitotic recombination B. DNA hypermethylation C. Gene transfer D. Nondisjunction in mitosis E. All of the above are examples of LOH

B

Which of the following is not true of the SOS protein that A. It is a GEF protein B. It is a GAP protein C. It is capable of activating Ras D. It contains critical proline residues E. None of the above

B

Explain why a patient with familial retinoblastoma is at a much higher risk of subsequent cancer development than a patient with the sporadic disease.

Because the person lost a good copy of their gene, the mutated one could be invasive in another pathway.

Why would an oncogenic TRK driven by ectodomain deletion require a different treatment than an oncogenic RTK driven by receptor overexpression?

Because there is no outside portion to bind a treatment molecule to.

DNA damage in normal cells will likely result in all of the following except: A. Checkpoint kinase activation B. p53 stabilization C. p53 ubiquitination D. increase in p21 transcription E. all of the above will likely result from DNA damage in a normal cell

C

Which of the following is not a reason why cancer is so hard to treat A. Its hard to distinguish cancer cells from normal cells B. Cancer is constantly mutating C. Cancer is monoclonal in origin D. There are so many types of cancer E. All of the above are reasons

C

Which of the following statements is true? A. most types of human cancer are associated with transforming retroviruses B. RTK autophosphorylation usually happens prior to receptor dimerization C. treating cancer cells that have truncated EGF receptor ectodomains is generally harder than treating cancer cells that have increased EGF receptor expression with structurally normal EGF receptors D. truncation of the ectodomain of an RTK would decrease RTK activation because the growth factor can no longer bind to the receptor E. none of the above

C

Why is cancer so difficult to treat?

Cancer is difficult to treat because it is your own cells that have gone awry. It is difficult to make treatments that differentiate between your cells and cancer cells. If you miss just one cancer cell, it is possible to for the cancer cell to evolve and then become more difficult to treat. Cancer is also not just one single disease; it has many genetic variants.

What is the most likely source of these DNA mutations? Heredity or environment? How do we know?

The most likely sources of DNA mutations are environment because of immigration studies. For example, Japanese who move to Hawaii have specific cancer rates that are inline with the specific cancer rates of that area.

What are the two primary mechanisms whereby proto-oncogenes can be converted into oncogenes and be able to provide specific examples for each mechanism?

Through (1) increased expression and (2) protein activation.

What are the two main implications of Peyton Rous's experiment?

Two implications are (1) virus could cause cancer and (2) another method to promote cancer at will in the lab was presented.

What are the two primary types of carcinomas and which type of epithelial cells do they derive from?

Two main functions are (1) protection for cells and for lumen contents [squamous cell carcinoma] and (2) secretion [adenocarcinoma].

Identify two specific kinds of cancer that cannot fit into any of the four categories based on tissue of origin.

Two specific kinds of cancer that cannot fit into any of the above four categories based on tissue of origin are metastatic melanoma and teratoma.

What are the two primary pieces of experimental evidence that proved tumors were of monoclonal origin?

(1) Epigenetic evidence from leiomyoma: gel electrophoresis showing that leiomyoma tumors express one of the two variants of G6PD, but not both. (2) Monoclonal antibody production of multiple myeloma showed that the antibody (Ig) produces B cells normally but is replaced with a single (monoclonal) antibody-producing B cell population. See only one antibody from the same B-cell.

What is the focus assay and what are soft-agar assays? What properties of cancer cells are each useful for measuring?

A focus-forming assay allows you to see features of cancer cells that normal cells are picking up - can see piling up so loss of contact inhibition. Soft-agar assays allow you to see anchorage independent growth since the cells are floating in the medium.

What is the difference between an oncogene and a proto-oncogene?

A proto-oncogene is in normal cells and an oncogene is a gene which can transform cells and contribute to the promotion of cancer.

Analysis of a patients lung tumor reveals that all of the malignant cells in this tumor share a unique chromosomal abnormality. This most likely suggests that A. This mutation must have been inherited B. The tumor is polyclonal in origin C. The tumor is monoclonal in origin D. A large number of normal cells acquired this mutation simultaneously E. None of the above

D

Ligand Independent signaling of receptor tyrosine kinases can result from: A. fusion events that inhibit dimerization B. mutations resulting in truncated ectodomains C. amino acid substitutions in the cytoplasmic domains of receptors D. B and C E. all of the above

D

Normal proto-oncogenes found in the human genome can be activated to become oncogenes by all of the following mechanisms EXCEPT: A. mutations resulting in structural changes in the protein product B. mutations that result in higher levels of expression of the gene C. a retrovirus inserting directly upstream of the gene, driving increased expression D. all of these are mechanisms that can activate proto-oncogenes into oncogenes E. chromosomal translocations

D

Which of the following is true of the c-src gene? A. it BOtH results in cellular transformation AND is an example of a proto-oncogene B. it is present only in cells containing integrated viral DNA C. it results in cellular transformation D. all of the above E. it is an example of a proto-oncogene

E

Which of the following mechanisms may contribute to tumorigenesis driven by the Myc oncogene? A. increased Myc copy number B. constitutive activation of Myc under the transcriptional control of viral promoters C. chromosomal translocations D. A and B E. all of the above

E

Which of the following signaling pathways is in the correct order? A. Receptor -> Sos -> Grb2 -> Ras B. Receptor -> Ras -> Sos -> Grb2 C. Receptor -> Sos -> Ras -> Grb2 D. Receptor -> Grb2 -> Ras -> Sos E. Receptor -> Grb2 -> Sos ->Ras

E

What is the name of the growth factor receptor most commonly found on epithelial cells?

EGF

What are the major symptoms of leukemia and why can leukemia result in these symptoms?

Leukemia results in a huge proliferation of immature white cells, which leads to clotting sepsis, and anemia. Because the useless white cells take up room so the RBCs are pushed out.

Explain the steps between Ras and hyperactivation and hyperphosphorylation of Rb.

Lots of Ras leads to lots of cyclin D by causing the MPKT kinase cascade and promoting transcription factors Fos and Jun. Cyclin D binds to CDK4/6 and hypophosphorylates Rb. Then cyclin E/CDK-2 hyperphosphorylates Rb and inactivates it.

What is the general difference between oncogenic Ras and the Ras proto-oncogene?

The general difference is a glycine to valine change at position 12. The activating mutation disables the GTPase activity of Ras and locks it in the ON state.

What is the basic mechanism of RTK activation that we discussed in class?

The basic mechanism is autophosphorylation. RTKs are single pass transmembrane-proteins that dimerize upon ligand binding. The dimerization causes tyrosine kinase activation and autophosphorylation of the cytosolic tail.

What are the basics of the clonal evolution model of cancer to the extent that we spoke about it in class?

The clonal evolution model is related to Darwinian mutations and natural selection. Because the cancer cell (mutated cell) has proliferative advantage, it gets cloned and becomes a tumor because it outperforms its neighbors. These cells are prone to multiple successive mutations because one mutation destabilizes the cells and makes it more vulnerable to more mutations.

What are the 3 main structural regions of the receptor tyrosine kinase (RTK) (ectodomain, intermembrane domain, and cytoplasmic domain)?

The ectodomain is on the N' terminus side and is where the ligand binds. The intermembrane or transmembrane domain is the plasma membrane. The cytoplasmic domain is by the C-terminal tail and has tyrosine kinase enzymatic activity.

What is the value of using non-mammalian organisms to study cancer?

Zebra fish are easy to house, have low cost, have large numbers of offspring, have transparent bodies, and are amenable to both spontaneous and induced tumors. Drosophila melanogaster or the fruit fly is a useful model for studying normal development because they have a short lifespan. Their genetics are very well understood and form tumors by induction only. Lastly, saccharomyces Cerevisiae or budding yeast cannot induce cancer but can study their cell growth and proliferation pathways.