Oncology Flashcards
6 modalities/hallmarks of cancer
- Growth factor independence (GOF)
- Loss of response to anti-growth signals/differentiation signals (LOF)
- Resistance to apoptosis
- Recruitment of blood/lymph
- Invasion and metastasis
- Limitless replicative potential
Growth factor independence
- typically related to gain of function oncogenes
Proto-oncogenes
normal genes with important roles in regulating division, differentation, survival, movement –> mutate to oncogenes (GOF)
PI3K Pathway
- PI3K phosphorylates lipid on the cytoplasmic side of membrane
RTK (e.g. EGF receptor) –> activate PI3K–> converts PIP2 –> PIP3 –> docking site for PH domains (e.g. in AKT)–> AKT/PKB –> phosphorylation of proteins
- Involved in many signaling events
- Disregulation can have significant oncogenic downstream effects
Warburg effect
elevated AKT activity due to PI3K mutation –> increased glucose transport & glycolysis (basis of PET)
PTEN
- most common mutation leading to elevated PI3K activity
- PTEN converts PIP3–> PIP2 (opp. of PI3K)
- usually via deletion of PTEN or silencing of locus
- LOF is usually more common than GOF
Tumor suppressor
genes in which loss of function promotes cancer (e.g. PTEN)
p53
- tumor suppressor gene
- activates cell cycle arrest & apoptosis
- most cancers have p53 mutation
- DNA-binding transcription factor
- regulates
- p21 cyclin inhibitor
- GADD45- DNA repair
- Bax, Puma, Noxa- pro apoptosis
- MDM2- self-regulation
- accumulates in cancer cells b/c loss of autoregulation
Li-Fraumeni Syndrome
patients with one germ-line mutant copy of p53 gene –> prone to leukemias, sarcomas, breast, brain cancers associated with loss of remaining functional p53 allele in those cells –classic example of “loss-of-heterozygosity” (LOH).
Apoptosis
- highly ordered, ATP-dependent process-proteins, subcellular components dismantled by proteases (“caspases”)and nucleases
- membrane blebbing produces “apoptotic bodies” containing cellular debris, which are then engulfed by macrophages and other cells
- avoids release of cellular components that could trigger a damaging inflammatory response.
Caspases
- proteases that use conserved cysteine residue in their active site to cleave other proteins after aspartate residues in apoptosis
- initiators
- effectors/exectuioners
- present as procaspases until stimulus initates apoptosis
Intrinsic apoptotic pathway
mitochondrial membrane loses integrity –> cytochrome C released from mitochondria –> binds Apaf 1 to form apoptosome –> recruits procaspase 9 –> cleaves executioner caspases –> apoptosis
BCL related proteins
- promote apoptosis - Bax, Bax
- inhibit apoptosis - Bcl2
- apoptosis determined by equilbirium of these stress-responding factors
Extrinsic apoptotic pathway (death receptor)
- Fas (or other TNF death receptor) receptor binds FasL/–> recruits FADD/TRADD—> recruits intiators 8 and 10 which autoactivate and trigger effectors 8/10 –> DISC
Ways cancers bypass apoptosis
- over expressing antiapoptotics like Bcl2
- downregulating proapoptotics like Bax, Bak
- losing p53 which induces proapoptotics Bax, Puma, Noxa
- downregulating death receptors Fas, Trail
Hayflick Limit
- replicative senescence:
- most cells: division of cell –> some DNA lost –> limits number of replications
- if continued replication –> breakage fusion bridge cycle would occur –> inappropriate fusing of chromosomes
Telomerase
- telomerase adds extra telomeric DNA to some some cells (stem cells, lymphocytes)
- dysregulation ensures stable chromosomes for cancer
Angiogenic switch
- recruitment of blood vessels to ensure tumor growth > 2mm
- balance between
- inhibitors
- statins
- thrombospondin
- activators
- VEGF
- FGF
- EGF
- PDGFB
- inhibitors
Tumor vasculature
highly anomalous because of inconsistent equilibrium between pro/anti angiogenic factors
VEGF
- vascular endothelial growth factor –> stimulates EC division, survival, differentiation, movement –> master regulator
- main form = VEGF A
- binds to tks on ECs (VEGFR1 and 2) –> angiogenesis
VEGF blockers
antiangiogenic therapy
- bevacizumab = mab
- sunitinib/sorafenib = kinase inhibitors
Seed and Soil Metastasis
- cancer cells follow venous and lymphatic drainage
- some tumor cells may adher in or survive better in certain organs
Importance of Philadelphia chromosome
- encodes fusion protein BCR-ABL = oncogene with abnormal tk activity
- t (9;22) –> BCR intiator, ABL gene
- present in 100% CML, 30% AML
- Tx: Gleevec/Imatinib
FFPE
Formalin fixed parafin embedded –> cut tumor specimen –> laser capture DNA –> PCR –> identify markers, resistance
BRAF mutation
- GOF V600E most common (val/glu)
- predicts resistance to Vemurafinib
- BRAF mutation
- 40-60% melanoma
- 40-70% papillary thyroid
- 10% metstatic colorectal
Sequencing Read Length
number of sequential images taken
Sequencing Read Depth
number of DNA fragments for a given position
Reactive/benign disorders
- polyclonal expansion of different kinds of cells
- leukemoid reaction - expansion of granulocytes in response to bacterial infection
- lymphadenitis- inflammation of lymph nodes
Neoplasms
- clonal expansion of a single cell
- uncontrolled expnasion –> organ replacement –> functional compromise –> death
Leukemia
- neoplasms that involve bone marrow and spill into peripheral blood
- blood forming elements:
- granulocytes
- red cells
- megakaryocytes
- all lymphoblast-related are leukemias
- blood forming elements:
Lymphoma
- solid mass tumor of lymph nodes, spleen, extranodal sites (GI tract, skin)
- neoplasm of mature lymphocytes
Acute/precursor neoplasm
- immature early undifferentiated state
- blast
Chronic/peripheral neoplasm
mature differentiated cell neoplasm
Lymphomas- morphology
- size: small vs large (size of a mature lymphocyte vs. histiocyte nucleus)
- growth pattern: nodular vs. diffuse
- morphology is not the best predictor of behavior since some small cell lesions can be aggressive and indolent lesions can be unresponsive to therapy
Secondary lymphoid follicles
- follicle which develops after antigen presentation with B cells undergoing class switch and somatic hypermut.
-
germinal center: C10+BCL6+BCL2- –> need apoptosis working during proliferation so must be bcl2-
- dark zone: proliferating centroblasts
- light zone: mature centrocytes
- mantle of naiive B cells: CD10-BCL6-BCL2+
- undelrying CD21+ follicular dendritic meshwork
- mantle of plasma cells
Lymphomas- immunophenotype
- expression pattern of a surface and intracellular proteins in a cell population
- benign (polytypic) vs. neoplastic (monoclonal)
- lineage (CD3/T vs CD19/B)
- stage of diff. (Tdt vs. surface Ig)
- aberrant expressions
- CD5+ B cells
- mature T cells w/o pan-t antigens
- assessed by:
- flow cytometry
- immunohistochemistry
Immature B cell markers
Tdt- expressed by immature lesions
CD19
Mature B cell markers
all: CD19, CD20
mature: k/l light chains
germinal: CD10, BCL6 (secondary follicles)
all except germinal: BCL2
Immature T cell markers
Tdt
CD1a
cCD3
Mature T cell markers
CD2
sCD3
CD5
CD7
also: CD4/8
Lymphomas-genotype
- gross chromosomal rearrangements that lead to abnormal gene expression
- B cells undergo mutlipel rounds of damage –> more common neoplasms
- Ig rearrangement in marrow
- somatic hypermut./class switch
- Examples:
- Burkitt’s = t(8;14) IgH/Myc
- Follicular = t(14;18) IgH/BCL2
What does lymphoma genotype prove?
- clonality
- specific tumor subtype
Lymphomas- normal cell counterpart
neoplastic cells recapitulate morphology, immunophenotype of progenitor cells
Lymphomas-clinical features
- variable: asymptomatic vs. constitutional
- “type B” symptoms: fever, night sweats, weight loss
- dictated by affected site & tumor biology
- lymph nodes = lymphadenopathy
- extranodal = organ dysfunction
- marrow involvement = suppression
- plasma cell = bone destruciton
Lymphomas-characterization by clinical features
- lymphoblastic = pediatric
- extranodal marginal zone = mucosal spread
B Cell NHL
- derived from mature B cells
- neoplasms capitulate function of progenitors
- bone marrow involvement common (stage IV) –> interstitial except follicular
- liver/spleen involvement common
- difficult to cure
- can transform to aggressive
- IgH/14 involved in some important translocations
- indolent: follicular, cll/sll, marginal
- aggressive: DLBCL
- highly aggressive: Burkitt’s
Follicular lymphoma immunophenotypic profile
B: CD19+/CD20+/CD(2-8)-/
Germinal Center: CD10+
Aberrant: BCL2+
low Ki67 –> disease of cells surving a long time//not a disease of cells proliferating
CLL/SLL immunophenotypic profile
B: CD19+/CD20+
T: CD5+
Non-germinal: CD10-/BCL6-/BCL2+
Marginal lymphoma immunophenotypic profile
No distinct marker
B: CD19+CD20+
Not Germinal: CD10-/BCL6-/BLC2+
Follicular lymphoma- clinical features
- t(14;18) –> BCL2+
- General lymphadenopathy
- BM involvement common (Stage IV) –> represents hematogenous spread
- nonaggressive
- spleen and liver involvement common
- fine diffuse nodularity –> expansion of splenic white pulp
- in extensive disease –> red pump also
- occasional peripheral blood involvement –> small cleaved cells
- extranodal involvement uncommon
Follicular lymhoma- prognosis
- Indolent- waxing/waning course –> 8 years
- largely incurable
- Often transforms to diffuse B cell lymphoma –> 1 year survival
- Tx: observation, symptom relief, anti-CD20
Follicular lymphoma- morphology
- germinal center B cells
- nodular appearance- lots of germinal centers
- crowded, back to back
- lack polarity (thick/thin ends)
- no tingible body macrophages
- no discernable mantle
- paratrabecular aggregates
- grade 1 = more nodular and more centrocytes –>indolent
- grade 2/3 = more than 5 centroblasts/hpf
CLL/SLL: Chronic lymphocytic leukemia/Small lymphocytic lymphoma
- spectrum cancer
- circulating cells –> leukemia
- solid mass –> lymphoma
- CLL = most common adult leukemia
- SLL = uncommon
CLL/SLL-clinical features
- 13q/trisomy 12/deletion 11q/deletion 17p
- usually asymptomatic//6th decade presentation
- general lymphadenopathy
- low grade lymphoma for most of life
- usually progresses to Stage IV
- common hepatosplenomegaly
- peripheral blood involvement
- immune dysregulation
- autoimmune RBC/platelet
- AIHA
- thrombocytopenia
- autoimmune RBC/platelet
CLL/SLL- prognosis
- variable survival
- Group 2 > Group 1 prognosis
- transformations
- prolymphocytic leukemia
- richter’s transformation –> DLBCL
Richter’s transformation
- transformation of CLL/SLL to DLCBL
- same mechanism employed in all indolent lymphomas
CLL/SLL- morphology
- unknown source
- diffuse effacement of architecture
- proliferation centers: “pseudofollicles”
- prolymphocytes/paraimmunoblasts
- small round lymphocytes with condensed chromatin, scant cytoplasm, and fewer large cells. also see smudge cells
- interstitial marrow infiltrate: nodular or diffuse
CLL/SLL Group 1 and 2
- unmutated IgV
- no SHM/naive
- Zap70+
- aggressive
- hypermutated IgV
- post GC/mature
- Zap70-
- indolent
Marginal zone lymphoma
- 3 diseases
- nodal marginal zone lymphoma
- splenic marginal zone lymphoma
- extranodal marginal zone (MALT) –> most common
MALT MZL-clinical features
- t(1;14) API2-MALT1
- t(11;18) IgH/BCL10
- t(14;18) IgH/MALT-1
- associated with chronic inflammation (e.g. pylori, jejuni, borrelia, chlamydia)
- low grade with transformation to DLCBL
- Tx: antibiotics/antiviral
S-MZL
splenic marginal zone lymphoma associated with Hep C
MALT/MZL
NF-kB pathway
- responsible for stimulating cell survival and proliferation
- MALT–> BCL10 or API2MALT1 –> binds MALT1 –> induction of NF-kB
Plasma cells
- terminally differentiated B cells:
- CD19+, CD138+, CD56-
- in lymphoma, CD56+ hone plasma cells to marrow
- CD19+, CD138+, CD56-
- lymph nodes and bone marrow
- clockface nuclear chromatin, perinuclear clear zone, gray cytoplasm, eccentric nuclei
Multiple Myeloma
- plasma cell neoplasm
- most common lymphoid neoplasm in AA, 2nd most in whites
Multiple Myeloma- clinical features
- multifocal –> areas of hematopoeisis (vertebrae–>emergency!!!), ribs, skull)
- anemia (from marrow replacement and renal failure)
- hypercalcemia (osteoclast activation)
- rouleaux/blood viscosity increase –>neurologic/thrombotic
- bone destruction
- pain
- osteolytic lesions –> “punchout”
Crab Plaits
C - calcium is high
R - renal failure
A - anemia
B - bone disease, bone pain, Bence-Jones protein (a paraprotein)
P - paraproteins (useful for monitoring patient)
L - LDH (again for monitoring)
A - amyloidosis (a complication)
I - immune paresis (suppression of Ig, a complication)
T - thalidomide (treatment)
S - stem cell transplant (treatment)