Robbins Neoplasia pg. 1-45 Flashcards
T or F: Cancer cells are subject to Darwinian selection.
T
What does the phrase “all tumor cells are clonal” mean?
they arise from 1 cell
What are the 8 hallmarks of cancer?
- autonomous growth (don’t rely on outside growth signals)
- unregulated growth (do not respond to inhib signals)
- evade death (do not undergo apoptosis) in in conditions normal cells would
- limitless replication
- angiogenesis
- invade tissues and spread to other tissues
- reprogram metabolic pathways
- evade immune system
What is the (simplest) distinction between a malignant and a benign tumor?
benign: remain localized and can be removed surgically
Malignant: the lesion can invade and destroy adjacent structures and spread to distant site to cause death
What to malignant and benign tumors have in common? (think structure/organization)
same 2 basic components: parenchyma and stroma
What are the transformed cells in a turmor called?
parenchyma
What is the stroma? (in a tumor)
supporting, non-neoplastic cells in a tumor
What type cells can make up the stroma?
connective tissue, blood vessels, inflammatory cells (host derived ones)
What does the suffix “-oma” mean?
usually indicates a benign tumor
What are papillomas?
benign epithelial neoplasms
What shape does a papilloma take?
finger-like fronds (macro and microscopic)
What is a polyp?
benign mass that projects from a mucosal surface (macrscopic)
WHat is a benign hollow cystic mass that usually arises in the ovary?
cystadenomas
What is an adenoma?
benign epithelial tumor producing a gland pattern (diff pattern than papillomas)
What are malignant neoplasms that arise in solid mesenchymal tissues?
sarcoma
What are malignant neoplasms that arise from mesenchymal blood cells called?
leukemias and lymphomas
What are carcinomas?
malignant tumors of epithelial cells
What are carcinomas that grow in a glandular pattern?
adenocarcinomas
What are malignant squamous cell tumors called?
squamous cell carcinomas
What is divergent differentiation?
All tumors have a monoclonal origin but at some point during a tumors development it can switch types to create a mixed tumor
Ex: mixed tumor of salivary gland can have epithelial components dispersed in a fibromyxoid stroma with islands of cartilage or bone
What is another name for a mixed tumor?
pleomorphic adenoma
What type of malignant tumor contains recognizable mature or immature cells/tissues of more than one germ layer?
Teratoma
From what do teratomas originate from?
totipotential germ cells such as those present in the ovary and testies (often from more than one germ layer) * they are malignant
**Since they are totipotent in origin, the tumors often have many diff cell types in them (bone, nerve, muscle, fat, etc)
What malignancies end in “-oma”
lymphoma, melanoma, mesothelioma, and seminoma (testicular epithelium)
What is a mass of disorganized tissue indigenous to particular site?
Hamartoma (i.e. a nodule in the lung containing cartilage, bronchi, and blood vessels)
What is a congenital anomaly consisting of a heterotopic rest of cells? (i.e. organized pancreatic tissue found in the submucosa of the stomach)
Choristoma
What are the 4 fundamental features by which benign and malignant tumors can be distinguished?
- differentiation and anaplasia
- rate of growth
- local invasion
- metastasis
In what part of the tumor is differentiation and anaplasia seen?
parenchymal cells
The differentiation of tumor cells refers to …
the extent to which tumor cells resemble their normal cell counterparts.
Describe the difference in differentiation between benign and malignant parenchymal cells?
benign cells are well differentiated and closely resemble their normal counterparts
Malignant cells have a wide range of differentiation–looking similarly and vastly different from their normal counterparts
What does it mean for a neoplasm to be anaplastic?
it is composed of undifferentiated cells
If cells are anaplasic, are they more likely to be malignant or benign?
malignant
Describe the microscopic appearance of anaplastic cells.
- vary in size and shape (pleomorphic)
- extremely hyperchromatic (dark staining)
- larger nuclei (almost equal amt of nucleus to cytoplasm)
- giant cells
- variable shaped and sized nuclei
- numerous mitoses (and can br atypical)
In a neoplasm, what are giant cells?
big cells that can contain an enormous nucleus or several nuclei
T or F: The more rapidly growing and more anaplastic a tumor, the less likely it is to have specialized functional activity.
true
What is the loss in the uniformity of individual cells and their architectural orientation?
dysplasia
In what type of cells does dysplasia principally occur?
epithelial cells
T or F: Dysplasia is a type of neoplastic proliferation
F not neoplastic (can develop into neoplasia)
What is a dysplastic change involving the entire thickness of the epithelium?
carcinoma in situ
What is a pre-invasive stage of cancer?
carcinoma in situ
T or F: Mild to moderate dysplasia that does not involve the entire thickness of the epithelium can regress completely.
True: IF the inciting cause is REMOVED
In general, _____ tumors grow slowly and ____ tumors grow much faster.
benign; cancer
In general, do poorly or well differentiated malignant tumors grow faster?
poorly differentiated
A benign neoplasm does not have the capacity to …
infiltrate, invade, or metastasize to distant sites
encapsulated neoplasms are ______
benign
T or F: all benign neoplasms are encapsulated
F: they are not all encapsulated
Cancers grow by progressive …
infiltration, invasion, and penetration of the surrounding tissues
Next to metastases, _____ is the most relable feature that distinguishes malignant tumors from benign tumors.
local invasiveness
In general, what characteristics increase the likelihood of metastatic spread?
more anaplastic and larger neoplasms
What are the 3 pathways that malignant tumors spread?
- seeding within body cavities
- lymphatic spread
- hematogenous spread
Carcinomas typically spread via _____
lymphatic spread
Sarcomas typically spread via _____
hematogenous spread
What is a “skip metastases”?
cancer is not found in lymph nodes near the primary site… it spreads and seeds in lymph nodes far away from
What is a sentinel lymph node?
first regional lymph node that receives lymph from a primary tumor
Enlarged lymph nodes near the primary neoplasm does not always indicate metastatic spread. Why?
necrotic products of the neoplasm and tumor Ags often evoke immunologic responses
Are arteries or veins penetrated by tumors more readily?
veins
What organs are most frequently involved in secondary sites of hematogenous dissemination? Why?
liver and lungs
bc all portal veins drain to the liver and all caval veins drain to the lungs
Most cancer deaths occur between ages …
55 and 75
Autosomal dominant cancer syndromes typically involve the inheritance of …
a single mutant gene that greatly inc the risk of developing a tumor (i.e. inheritance of a germ line mutation of a cancer suppressor gene)
Autosomal recessive cancer syndrome are characterized by …
chromosomal or DNA instability (usually defect in DNA repair)
What are the features of familial cancers?
- early ago of onset
- tumors in 2 or more close relatives
- multiple or bilateral tumors
What are pre-neoplastic lesions?
aquired condition that inc the likelihood of malignancy but does not always (or usually) progress to cancer. Their removal or reversal may prevent the development of cancer.
***HOW is this different than dysplasia… Is it different??
Autosomal dominant or recessive mode of inheritance for development of cancer?
defects in DNA repair
recessive
Autosomal dominant or recessive mode of inheritance for development of cancer?
mut tumor suppressor gene
dominant
T or F: lethal genetic damage lies at the heart of carcinogenesis
F: non-lethal
What are the principle targets for genetic damage leading to cancer?
- growth-promoting proto-oncogenes
- growth inhibiting tumor suppressor genes
- genes that regulate apoptosis
- DNA repair genes
What are oncogenes and what are proto-oncogenes?
proto-oncogenes are normal cellular genes that are mutated to become oncogenes (oncogenes induce a transformation of phenotype)
What do most oncogenes encode?
Tx factors, growth regulating proteins, proteins involved in cell survival, proteins involved in cell-cell or cell-ECM interactions
T or F: usually only 1 allele of a tumor suppressor gene needs to be damaged for transformation to occur.,
F: both alleles
What is haploinsufficiency?
When 1 mutated allele can cause a disease phenotype
What are the 2 groups of tumor suppressor genes?
guardians and governors
What is the difference between governor and guardian tumor suppressor genes?
governor genes encode a factor that inhibits growth while guardian genes sense genomic damage and cause proliferation to stop
What is the consequence of a mutation in a governor tumor suppressor gene?
cells transform into tumors bc they never receive a signal to stop growing
What is the consequence of a mutation in a guardian tumor suppressor gene?
mutations will accumulate and can eventually lead to the development of cancer (p53)
*recessive mode of inheritance (generally)
What is the difference between a mutation in an oncogenes and a mutation in a tumor suppressor gene?
only 1 allele needs to be mutated in an oncogene to lead to the development of cancer while 2 mutated alleles of tumor suppressor genes are generally needed to lead to cancer
*note, some tumor supressor genes act like oncogenes in that they only need 1 mut allele to cause cancer
What are the common types of non-random structural abnormalities in tumor cells?
- balanced translocation
- deletions
- duplications (gene amplification) `
How do balanced translocations lead to development of neoplasms ?
over expression of pro-oncogenes by removing them from their normal promoter to one that causes them to be under the control of a highly active promoter –> over expression
What are 2 neoplasms that develop from balanced translocations?
Burkitt lymphoma and follicular B cell lymphoma
What is the molecular basis of Burkitt lymphoma?
translocation between chrom 8 and 14 which leads to over expression of MYC gene on chrom 8 bc it is placed under the same control as Ig heavy chain regulatory elements on chrom 14
What is the molecular basis of follicular B cell lymphoma?
reciprocal translocation between chrom 14 and 18 which leads to over expresson on BCL2 (anti-apoptotic gene) when it is moved to chrom 14 and placed under the same reg control of Ig heavy chains
How can a deletion lead to the development of a neoplasm?
can delete a tumor supressor gene (needs both copies KO so the other allele would have a pt mutation)
How does gene amplification lead to the development of neoplasms?
causes over expression of proto-oncogenes
T or F: Aneuploids in an established cause of carcinogenesis
F: it is an established consequence of it
How does aneuploidy arise in cancer cells?
errors in mitotic checkpoint which leads to mis-segregation of chromosomes
What role do miRNAs have in neoplastic transformation? (think oncogenes and tumor supressor genes)
if miRNA levels for an oncogene decrease, it will cause an over expression of the oncoprotein –>
If the miRNAs for a tummor suppressor gene are over expressed it causes a dec in tumor suppressor protein –>
inc proliferation
reduced apoptosis
inc invasiveness
angiogenesis
What are reversible, heritable changes in gene expressin that occur without mutation?
epigenetic changes
Describe the epigenetic modifications present in cancer cells.
global DNA hypomethylation and selective promoter hypermethylation of tumor suppressor gene or DNA repair gene promoters
What is carcinogenesis?
a multistep process resulting from the accumulation of multiple genetic alterations that collectively give rise to a transformed phenotype
What is tumor progression?
over time, tumors become more aggressive and acquire greater malignant potential
T or F: tumor progression is correlated to an inc in tumor size
False: not correlated to size
T or F: Because malignant tumors are monoclonal in origin, the constituent cells are homogenous.
F: they are extremely heterogeneous –> darwinian selection
What type of cells are selected for during tumor progression?
- more adapt at evading immune system
- more aggressive cells
- less responsive to therapy over time
All normal cells require ____ to undergo proliferation.
stimulation by growth factors (via paracrine signaling)
How do tumor cells acquire growth self sufficiency?
- they synthesize the same growth factor to which they are responsive = POSITIVE feedback loop
* *normal cells are not able to do this, they lack the receptor that recognizes the GF they make - they mutate the recpetor so that there are continuous mitogenic signaling to cells (even in the absence of GF)
- they over express the receptor so that they are hyper-responsive to the GF and will proliferate at GF concentrations that normally do not trigger proliferation
- Mutate RAS or ABL
- Mut nuclear Tx Factors (MYC)
- mut that activate cyclins or inactivate CDK inhibitors
* basically anything that drives cell cycle to become dysregulated by via mutations or amplification
What is the most commonly mutated proto-oncogene in human tumors?
RAS (mutation interferes with hydrolysis of bound GTP so that RAS will always be active and thus always signaling for the cell cycle to continue
What is the normla function of RAS protein?
switches between a GDP (inactive) and GTP (active) bound states. When active, its activates expression of MYC protein* –> cell cycle progression
*via P13 kinase/AKT pathway or RAF/ERK/MAP pathway
What is the role of ABL in carcinogenesis?
ABL gene translocates to form a BCR-ABL hybrid. This mutates the Tyr Kinase to make it constitutively active –> this activates everything downstream of RAS –> MYC constitutively expressed –> cell cycle progresses continuously
What is the consequence of constiuitively active MYC?
inc expression of CDK and decreases expression of CDK inhibitors –> cell cycle ON
At what point in the cell cycle do cells become committed to DNA replication? What protein is primarily responsible for controlling this step?
G1-S transition via cyclins
What check point monitors the integrity of DNA before replication?
G1-S checkpoint
What check point monitors DNA aftetr replication to determine whether it can safely enter into mitosis?
G2-M checkpoint
All cancer cells seem to have genetic lesions that disable the _____ checkpoint.
G1-S so that the cells continuously enter S phase
How many mutations are needed to cause retinoblastoma?
Both RB genes
Pts with retinoblastoma are usually born heterozygous and then loose their normal copy
T or F: A cell that is heterozygous at the RB locus is neoplastic
F: not neoplastic
Describe the role of active and inactive RB in the cell cycle:
Inactive: it is in a hyperphosphorylated state; it cannot find to E2F –> E2F can turn on Tx of S phase genes –> cell cycle proceeds to S phase
Active RB: in a hypophosphoylated state in which it can bind E2F –> Tx OFF –> cell cycle does NOT go into S phase
Describe how RB becomes activated and inactivated.
Growth factors (EGF, PDGF) activate cyclin D/Cdk4, 6 and cyclin E/Cdk2 to phosphorylate RB –> RB inactive –> cell cycle goes into S phase
Growth inhibitors (TGF-B, p53) inactivate cyclin D/Cdk4, 6 and cyclin E/Cdk2 –> RB active –> cell cycle does NOT go into S phase
RB exerts ________ effects by controlling the G1-S phase transition of the cell cycle.
anti-proliferative
*when RB is active it turns off cell cycle by inhibiting E2F
What happens to the cell cycle if there is non-functional RB?
E2F would not be controlled –> cell cycle always proceeding to S phase
What os the normal role of p53?
senses DNA damage -> upregs Cdk inhibitors to stop cell cycle at G1 and allow repair of damage
If DNA damage is too great to repair, p53 triggers senescence or apoptosis (via BAX or PUMA gene induction)
What is Li-Fraumeni syndrome?
persons have 1 mutated copy of p53 gene, therefore, they are predisposed to developing malignant tumors
What activates p53 expression? (3)
- anoxia (= NO oxygen)
- inappropriate oncogene signaling (MYC or RAS)
- DNA damage
Describe the normal TGF-Beta signaling pathway.
TGF-B binds to receptors and inhibits proliferation by…
- activating Cdk inhibitors
- inhibiting expression of MYC and cyclins
In 100% of _____ cancers and 83% of ____ cancers, at least one component of the TGF-beta pathway is mutated.
pancreatic and colon
What is WNT and what is its normal function in cell cycle?
a soluble pro-proliferative factor
MOA: prevents degradation of Beta-catenin by APC so Beta-catenin can go into the nucleus to work with TCF and turn on proliferative genes
APC gene exerts _____ actions by regulating destruction of Beta-catenin.
anti-proliferative
Would a mutated APC gene or protein so that it could not interact with Beta-catenin be pro- or anti-proliferative
pro-proliferative bc B-catenin would not be destroyed/it could go into the nucleus to turn on pro-proliferative genes
What is the mutation in adenomatous polyposis syndrome?
germ line mut in APC gene
In 100% of _____ cancers and 83% of ____ cancers, at least one component of the TGF-beta pathway is mutated.
pancreatic and colon
What is WNT and what is its normal function in cell cycle?
a soluble pro-proliferative factor
MOA: prevents degradation of Beta-catenin by APC so Beta-catenin can go into the nucleus to work with TCF and turn on proliferative genes
APC gene exerts _____ actions by regulating destruction of Beta-catenin.
anti-proliferative
Would a mutated APC gene or protein so that it could not interact with Beta-catenin be pro- or anti-proliferative
pro-proliferative bc B-catenin would not be destroyed/it could go into the nucleus to turn on pro-proliferative genes
What is the mutation in adenomatous polyposis syndrome?
germ line mut in APC gene
