Pathology 2 Flashcards
What is the job of NK cells, how are they regulated, and what do they secrete?
Killers of virus infected and tumor cells.
Activating receptors: activated by viral and stress-induced proteins
Inhibiting receptors: engaged by normal levels of MHC I
Secrete: IFN-y and TNF
What does innate immunity consist of?
Barrier
Phagocytes - neutrophils and macrophages
NK cells
Plasma proteins - compliment, CRP, mannose-binding lectin
What occurs with Tcell activation?
Release of cytokines, proliferation, differentiation into effector or memory cells.
What is the difference between TH1 and TH2 cells?
TH1: Release IL-2 and IFN-gamma. Tcell proliferation, macrophage activation, Ab production
TH2: Release IL-4, 5, 13. eosinophil activation and IgE synthesis
What are 2 subclasses of T regulatory cells?
Treg: Express CD4, CD25, and FoxP3. Suppress Tcell activity, APCs. Suppress autoreactive Tcells
adaptive regulatory Tcells: Express CD4 and upregulate CD25 in the periphery (MALT). induced by inflammation
Release IL-10 and TGF-B
CD8 cell function
Interact with MHC I (expressed on most cells). Activated by foreign peptide, self-restricted. Important in response to virus infection.
What effect does CD 21 have on Bcell activation?
amplifies. Binds complement component (Cdg) that is attached to pathogen surface. Amplifies BCR signal and Bcell response
What is the function of Dendritic cells? What is a follicular dendritic cell?
Dendritic cells: in epithelium and interstitium. major APC for CD4+ Tcells. Can migrate to lymph organs
Follicular dendritic cells: found in germinal centers of lymph follicles. Present to B cells -> activation
What chromosome houses MHC / HLA genes?
Chromosome 6
What genetec loci encode MHC I variable regions?
HLA A, B, C
What genetic loci encode MHC II variable regions?
Subregions of HLA D:
HLA DP, DQ, DR
What types of proteins are presented by MHC I and II?
MHC I: cytoplasmic antigens
MHC II: exogenous antigens
Type I hypersensitivity
Anaphylactic type
IgE mediated, TH2 dependent
Antigen -> dendritic cell -> presentation to Tcell -> TH2 activation, secretion of IL-4 -> Bcell activation -> IgE plasma cell -> IgE attaches to mast cells (first exposure)
Second exposure: allergen cross-links IgE on mast cell -> degranulation
What is released with degranulation of mast cells / basophils in the setting of allergic reaction?
- Primary response - preformed mediators in granules: biogenic amines (histamine, adenosine), chemotactic factor (eosinophil), enzymes, proteoglycans
- Secondary response - newly synthesized (later): PLP A2 activation -> leukotrienes (LTB4, C4, D4) and prostaglandins (PGD2), PAF
cytokine / chemokine secretion: Interleukins, TNFa, GM-CSF
What histopathologic findings are associated with Type I hypersensitivity?
Vascular: vasodilation, increased permeability, edema
-histamine, PAF, LTC4 and D4
Bronchial sm. muscle contractoin: biogenic amines, LTC4 and D4, PAF, PGD2
Increased secretion - mucinous metaplasia: histamine, PGD2
Infiltration - eosinophil, chron. inflamm. cels: eosinophil chemotactic factor, LTB4, PAF, TNFa
What is type II hypersensitivity?
Involves antibody binding to cell surfaces or tissue antigens.
May or may not involve complement
Results in cell destruction or cell/ tissue dysfunction
Examples of Type II hypersensitivity, w/ and w/o compliment.
Compliment dependent:
Autoimmune rxn to blood cells
Transfusion rxns, hemolytic disease of the newborn
Autoimmune skin-bistering (pemphigous vulgaris)
Goodpasture (Ab to glomerular and pulmonary basement membrane)
Antibody-dependent cell-mediated cytotoxicity (ADCC):
Response to parasite / malignant cells
Antibody mediated tissue dysfunction: no cell death
Myasthenia gravis, Graves
What are type III hypersensitivity reactions?
Immune complex mediated
Excess antigen -> immune complex formation and deposition in tissue -> complement activation -> acute inflammation / coagulation, tissue injury
Results in vasodilation, edema, necrosis
What is an Arthus Reaction?
Local immune complex disease
tissue necrosis resulting from acute immune complex vasculitis, usually elicited in the skin.
Immune complexes precipitate in vessel walls -> fibrinoid necrosis
What are 3 phases of Type III hypersensitivity?
1) immune complex formation (exogenous or endogenous antigen)
2) immune complex depisition (local or systemic)
3) tissue injury (complement activation (not at native site), acute inflammation, coagulation)
Examples of Type III hypersensitivity
Acute post-streptococcal glomerulonephritis
SLE
Polyarteritis Nodosa
Rheumatoid Arthritis
What type of necrosis is associated with Type III hypersensitivity?
fibrinous
Due to compliment activation and MAC -> coagulation -> fibrin deposition
What is the key pathologic finding in Type III hypersensitivity?
Acute necrotizing vasculitis of small to medium sized blood vessels
What is Type IV hypersensitivity?
Cell mediated: delayed or cytotoxic
Delayed: TH1 mediated
Cytotoxic: CD8 mediated
Examples of Type IV hypersensitivity
Delayed: TB and TB skin test, contact dermatitis (poison ivy), fungal infections
Cytotoxic: viral infection, tumor immunity, acute graft rejection
IL-12
Produced by macrophages
Results in differentiation and activation of TH1 cells
Describe the Direct and Indirect pathways of transplant rejection
Direct: recipient Tcells recognize MHC on donor APCs. (Acute rejection)
- -Paradoxical Mimicry
a) MHC-1 -> CD8+ Tcell proliferation and cytotoxic hypersensitivity. Results in apoptotic death of graft cells
b) MHC-II -> CD4+ Tcell proliferation (TH1) -> delayed type hypersensitivity. IL-2, TNF-a, and IFN-y ->Inflammatory response and tissue destruction by mobilized macrophages
Indirect: Usual mode of rejection (Chronic Rejection)
Host APCs present graft antigen on self-MHC II
CD4+ Tcell activation -> delayed type hypersensitivity and transplant rejection
What is rejection vasculitis?
Antibody mediated transplant rejection
a) hyperacute: preformed Ab
b) acute: induced Ab
What is hyperacute rejection?
Due to preformed antibody -> rejection vasculitis
w/in minutes - hours of transplant
immune complex formation and vascular deposition -> complement activation -> vasodilation, vascular permeability -> inflammatory infiltrate -> necrosis, hemorrhage, thrombosis -> infarction
How long after transplantation does acute rejection take place? What usually causes it?
days to weeks after transplant or later due to reduction in immunosuppression
What drugs are frequently used to prevent transplant rejection?
Cyclosporine: calcineurin inhibitor - decreases IL-2 expression
Tacrolimus: binds FKPB to inhibit calcineurin (less nephrotoxic)
Corticosteroids: anti-inflammatory and decreases lymphocytes, monoycytes, eosinophils and basophils
Azothioprine: inhibits denovo purine synth. converted to 6-MP
Anti-Tcell receptor Ab
GVH disease and tissues affected
Graft vs. Host disease: donor’s CD4 and CD8 cells react against host tissue
Skin: maculopapular rash, desquamation
Mucosal surfaces: GI: NVD ; eyes and mouth: dryness and irritation
Liver: jaundice (bile duct injury)
Lymph organs: coumpound recipients immunodeficiency may -> autoimmune disease
What are 4 mechanisms of peripheral immunotolerance?
- Anergy - recognition of self antigen w/o co-stimulatory signal -> negative signal -> eventual inactivation / inability to propogate stimulatory signal.
- Suppression - regulatory Tcells suppress self-reactive Tcells
- Deletion - repeated activation of self-recognizing Tcells -> expression of Fas and Fas ligand -> apoptosis
- Antigen sequestration - antigens “hidden” in tissues not directly exposed to blood and lymph. Ex: brain, testes, eye
how can infection lead to autoimmunity?
1) infection -> increased expression of co-stimulatory molecules on APCs -> activation of self-recognizing Tcells
2) tissue damage 2ndary to infection -> release / alteration of self antigens and exposure of previously “hidden” antigen -> reactivity of self-specific lyphocytes.
What is the genetic link in SLE?
Disease is multifactorial
Increased frequency in family members of pts. w/ SLE, especially monozygotic twins.
-assoc. between certain HLA alleles and certain SLE antibodies (anti-dsDNA, anti-Smith Ag)
-inherited deficiencies in complement in minority of SLE patients - impaired immune complex clearance
What environmental factors are associated w/ SLE?
UV radiation - pyrimidine dimerization -> cell death -> exposure to nuclear Ag
Elevated sex hormones - estrogen - women more affected
Certain meds - hydralazine (HTN)
What are the major antibodies seen in SLE (3 groups)?
Anti Nuclear Ab: Type III hypersensitivity rxns
Anti-phospholipid: bind proteins assoc. w/ phospholipids
-in vivo: hypocoagulability (lupus anticoagulant)
-in vitro: hypercoagulability (secondary antiphospholipid antibody syndrome)
-anti B2-glycoprotein Ab binds cardiolipin -> false (+) syphilis
Anti-formed element: type II hypersensitivity (anemia, thrombocytopenia, leukopenia)
What are the 5 classes or lupus glomerular nephritis?
I: minimal mesangial: appears normal under LM, but EM reveal mesangial immune complex deposition
II: Mesangial lupus nephritis: visible increase in mesangial cell number and matrix volume
III: Focal proliferative glomerulonephritis: 1/2 of all glomeruli are affected. Most severe, most common
same as III, but more widespread, maybe more necrosis/thrombosis
V: Membranous glomerulonephtiris: Thickening of glom. capillary walls. “wire loop” lesions (may be present in III and IV as well)
How can Lupus effect the heart?
- pericarditis most common - fibrinous inflammation of serous membrane -> chronica inflamm, fibrosis
- Libman Sacks endocarditis - vegetations present on any surface of any valve
- Myocarditis
How does SLE effect joints?
Results in synovial inflammation w/o articular erosion
What pattern of immunoflorescent Anti-Nuclear-Antibody (ANA) testing is most specific for SLE?
Rim pattern - “rim” of flourescence around exposed nuclei is indicative of the presence of Anti-dsDNA Ab in patient’s serum.
Other patterns are non-specific or suggest other diagnoses.
What are nucleolar and centromere patterns of ANA immunofluorescence suggestive of?
Nucleolar: systemic sclerosis
Centromere: limited systemic sclerosis (CREST)
What antibodies are most common in SLE?
Anti-dsDNA and Smith Ag
What is a Lupus Erythmatosus (LE) cell or hematoxylin body?
Neutrophil or macrophage that has phagocytosed the nuclei of injured cells.
Seen in SLE
What is chronic discoid lupus erythematosis?
Causes scarring skin plaques
Usually only involves the skin
What is subacute cutaneous lupus erythematosis?
Mild form of SLE that typically manifests as a non-scarring photosensitive cutaneous rash. Mild systemic effects.
ANAs are present, especially anti-Ro (SS-A) Ab.
What medications can cause lupus like symptoms?
hydralazine, procainamide
Symptoms usually resolve with removal of med.
ANAs (esp. antihistone) may be present w/o symptoms
What is Sjorgen Syndrome?
Chronic autoimmune disorder primarily affecting lacrimal and salivary glands.
Mostly women 50-60 y/o
Primary - sicca syndrome
Secondary - associated w/ other disorder (usually RA)
What antibodies are most often seen in Sjorgen’s?
Anti-ribonucleoproteins
Anti-Ro (SS-A), Anti-La (SS-B)
What serious condition does Sjogren syndrome increase risk for?
B-cell lymphoma - high rate of replication -> increased chance for errors
Systemic sclerosis and variants. What causes?
chronic excessive fibrosis. Mostly women 40-50.
1) diffuse: rapidly progressing. start with all skin, progress to visceral organs
2) limited: slowly progressing. limited to skin of face and distal upper extremities - includes CREST
Caused by inappropriate activation of CD4+ Tcells -> secretion of cytokines, growth factors -> fibroblast activation -> excessive collagen production
What is CREST?
subset of limited systemic sclerosis Calcinosis Reynaud's Esophogeal dysmotility Sclerodactyly Telangiectasia
What antibodies have been found in systemic sclerosis?
Anti-nuclear Ab:
1) anti-Scl 70: against DNA Topoisomerase I. specific for diffuse Systemic sclerosis
2) anti-centromere Ab. mostly CREST
What is mixed connective tissue disease?
Has overlapping features of SLE, polymyositis, RA, and systemic sclerosis.
Patients have high titers of anti-U1 RNP
Patients present with minimal renal disease.
Excellent response to corticosteroids
What is SCID?
Severe Combined Immunodeficiency Diseases
T and B cell dysfunction
Heterogenous group of diseases
What is the most common form of SCID? What causes it?
X-linked recessive SCID
50-60% of all cases
Abnormal IL receptor protein
What is the most common cause of autosomal recessive SCID? Others?
Adenosine Deaminase (ADA) deficiency ~50% of AR cases
abnormal metabolism of adenosine / deoxyadenosine -> accumulation of alt. metabolites -> decreased DNA synth and cell toxicity
-especially affects Tcells
-has been treated w/ gene therapy (retrovirus w/ normal ADA gene)
Also:
-MHC II deficiency (bare lymphocyte)
- abnormal receptor or signaling
-PNP deficiency (purine metabolism
What are the clinical findings in a patient w/ SCID?
Minimal lymph tissue
Small, non-descended thymus
Severe lymphopenia - decreased mature T and B cells
Deficient cell-mediated immunity: in vitro - no lymphoproliferative response to mitogen or allogeneic substance
in vivo - no delayed-type hypersensitivity or allograft rejection
Deficient humoral immunity: scant IgG, absent M and A
What infections are SCID patients susceptible to?
Pyogenic bacteria (PSA, Strep, Staph, H.influenzae
Fungi and protozoa
Viruses
Viable attenuated vaccines -> illness
How is SCID treated?
Early allogenic stem cell transplant
Good chance for take, but high risk for GVH. Donor sample must be depleted of mature Tcells
What causes DiGeorge Syndrome?
Defective development of 3rd and 4th pharyngeal pouch.
Usually due to 22q11deletion
What are clinical features of DiGeorge?
Hypoplastic or absent thymus
Low-normal lymphocyte count (Bcells are normal)
Paracortical areas of lymph nodes and PALS in spleen are depleted
Deficient cell-mediated immunity (no delayed hypersensitivity or graft rejection)
Absent or rudimentary parathyroid glands hypocalcemia -> tetany in first days of life
congenital defects of heart and great vessels, facial deformity
What infections are DiGeorge patients susceptible to?
Viral, Fungal, Mycobacterial
most bacterial infections are Tcell independent, so immunity is not compromised
How is DiGeorge treated?
Ca++ supplimentation for life
Cardiac surgery
Fetal thymus transplant - often unnecessary. Body has other Tcell maturation zones - often outgrow Tcell deficiency
What is the pathogenesis of Bruton’s X-linked agammaglobulinemia?
Bruton’s Tyrosine Kinase mutation -> inability for Bcells to mature
X-linked recessive
What infections are XLAG patients particular susceptible to?
pyogenic bacteria (Strep, Staph, PSA, Hib) certain viruses (entero and hepatitis) Giardia Lamblia (watery diarrhea)
How is XLAG treated?
periodic gamma-globulin injections
What is the most common primary immunodeficiency ?
Isolated IgA deficiency
What causes isolated IgA deficiency?
Block in differentiation of IgA Bcells
Other classes are usually normal
May be congenital (variable inh. pattern) or acquired (toxoplasmosis, virus, drugs)
What infections are selective IgA deficient patients susceptible to?
Respiratory and GI (sinopulmonary infections and diarrhea: loss of mucosal defense)
Patients may be asymptomatic
What is a concern with blood transfusion in selective IgA deficient patients?
~40% of pts. have anti-IgA Ab.
If given blood containing IgA, may have anaphylactic reaction
What is common variable immunodeficiency?
Heterogenous group of disorders diagnosed in teens and young adults
Hypogammaglobulinemia (usually all, sometimes only G)
Congenital (variable) or acquired
Bcell deficit - failure to mature to plasma cells
May be defective Tcell regulation: either deficient Thelper or excessive Treg
What are features of Common Variable Immunodeficiency?
Normal number of Bcells, but plasma cells lacking
Hyperplastic Bcell areas of lymph tissue in nodes, spleen, GI
Recurrent infections: pyogenic bacteria, intestinal - giardia and C.diff
Non-caseating granulomas (not sure why)
ex. duodenal nodular lymphoid hyperplasia
What is Wiscott Aldrich?
Diagnostic triad: 1) cellular and humoral immunodeficiency 2) eczema 3) thrombocytopenia
Recurrent infections, bleeding complications or malignancy -> death around 6-8 yrs
X-linked recessive : defective WASp protein - cytoskeletal actin rearrangement
susceptibility to encapsulated pyogenic bacteria
How is Wiscott Aldrich treated?
Stem cell transplant
What is the immunoglobin profile seen in Wiscott-Aldrich?
low IgM, normal IgG, elevaged IgA and E
What pathogens are Wiscott-Aldrich patients particularly susceptible to?
polysaccharide antigens
What is Ataxia-Telangiectasia?
Defect in Ataxia-Telangiectasia Mutant (ATM) gene -> chromosomal instability (compromised DNA repair)
Patients have progressive neurologic dysfunction, cerebellar ataxia, oculocutaneous telangiectasia, X-ray sensitivity, impaired organ development (elevated a-fetoprotein)
Variable immunodeficiency, malignancies
What is desmoplasia?
Dense collagenous stroma often induced by malignant neoplasm, especially carcinoma.
Responsible for “hardness” of tumor.
-oma suffix
refers to benign tumor
-carcinoma suffix
epithelial cell malignancy
-sarcoma malignancy
mesenchymal cell malignancy - bone, fat, cartilage, epithelial
adeno- prefix
glandular epithelium
leiomyo- prefix
smooth muscle
rhabdomyo- prefix
skeletal muscle
what is papillary growth pattern?
multiple finger like projections growing into a cystic space.
Polypoid tumor growth
neoplastic cell mass projecting above a mucosal surface.
Seminoma
Malignancy of testicular germ cell line
-oma exception
Teratoma
Germ cell neoplasm that shows differentiation toward more than one germ cell layer (ecto, meso, or endo - often all 3)
May be benign or malignant
Choristoma
Benign tumor - nodules of normal tissue in abnormal places
“ectopic rest of normal tissue”
Hamartoma
Benign mass of normal, mature tissue - disorganized.
Often found in lung - cartilage, bronchi, vessels
what is anaplasia?
Morphologic alterations seen with loss of differentiation.
Anaplasia is a hallmark of malignancy. Reversal of differentiation to a more primitive level.
Associated with pleomorphism, hyperchromatic nuclei, mitoses, loss of polarity, giant tumor cells
What atypical functions can be taken on by neoplastic cells?
Aberrant hormone synth: PTH by squamous cell carcinoma of lung; Gastrin by pancreatic islet cell tumor of pancreas
Fetal protein synth: a-fetoprotein by hepatocellular carcinoma; carcinoembryonic antigen produced by colon carcinoma
What is dysplasia?
Abnormal growth. Potentially pre-malignant. Confined to epithelial surface. Does not penetrate basement membrane -Failure of normal maturation -Loss of polarity -Cytologic features of anaplasia
Full thickness = carcinoma in situ
What tends to grow faster: poorly, moderately, or well differentiated malignancy?
Well differentiated tends to grow fastest
How do carcinoma and sarcoma spread?
Carcinoma: lymph -> venous -> lung -> arterial circ. and systemic metastasis
Sarcoma: hematogenous spread before lymph
What tissues are common sites of venous metastatic spread
Liver - hepatic portal system
Lungs
Vertebral bodies - paravertebral plexus (prostate carcinoma)
What are clinical features of metastasis by seeding of body cavities?
Fluid collection (ascites, plural effusion, hydrocephalus)- angiogenesis -> exudative edema
Accumulation of mucinous material: ex. mucus secreting ovarian carcinoma
What is malignancy “grade?”
Based on extent of differentiation
Scale: I-IV (well - poorly differentiated)
What is meant by malignancy Stage?
Based on TNM system: Tumor size, lymph Node involvement, hematogenous Metastasis
Scale: 0-IV (T: 0-4, N: 0-3, M: 0-1)
more valuable than stage for determining prognosis and treatment
What underlies cachexia due to malignancy?
Cytokines produced by macrophages or tumor cells
TNF, IL-1 -> decreased appetite + increased fat / muscle catabolism -> wasting
What tumor type is associated with Cushing’s?
Bronchogenic small cell carcinoma
Ectopic production of ACTH or ACTH-like product -> increased release of corticosteroids
What tumor type is associated with SIADH?
Syndrome of inappropriate ADH secretion
Bronchogenic small cell carcinoma
Ectopic ADH production
What tumor type is associated with hypercalcemia?
Bronchogenic squamous cell carcinoma
Ectopic production of PTH
What is carcinoid syndrome and what tumor activity causes it?
Characterized by flushing, sweating, bronchospasm, colicky abdominal pain, diarrhea, right sided CV fibrosis.
Caused by ectopic serotonin produced by tumors (ileal)
What is polycythemia and what tumor type is it associated with?
Increased RBC mass
Renal cell carcinoma
Ectopic production of erythropoietin
What is the name and cause of neuromyopathies seen in association with neoplasm?
Myasthenia Syndrome
Cross-reactive antibodies
What is acanthosis nigricans?
Darkening of the skin, usually in fold areas - axilla, back of neck
Associated with neoplasm
What is hypertrophic osteoarthropathy and what tumor type is it associated with?
Periosteal new bone formation of distal long bones and accompanying arthritis and fingertip clubbing
Associated with bronchogenic carcinoma (usually non-small cell)
What is Trousseau’s Syndrome and what tumor type is it associated with?
Migratory Thrombophlebitis associated with pancreatic adenocarcinoma.
Hypercoagulability -> clot formation, vasculitis and pain in the affected area.
What tumors are associated with nonbacterial thrombotic endocarditis?
Mucinic adenocarcinomas
Mucin reacts with platelet selectin -> platelet aggregation and deposition on valve leaflets.
vegetations consist of fibrin and platelets
3 hypercoagulation disorders associated with malignancies
Migratory Thrombophlebitis (Trousseau's) Nonbacterial thrombotic endocarditis Disseminated Intravascular Coagulation
Most assoc. w/ mucinous adenocarcinomas (pancreatic)
4 most common cancers in men and women
Men: 1) prostate 2) lung 3) colon 4) urinary tract
Women: 1) breast 2) lung 3) colon 4) uterus (endometrium)
*note that all are carcinomas
Overall cancer mortality rate and 3 leading cancer mortalities in men and women
Overall mortality 20-25%
Men: lung, prostate, colon
Women: lung, breast, colon
What is the key factor underlying the proliferative potential of cancer cells?
Increased telomerase activity
What is N/C ratio and what does it say about a cell?
Nucleus / Cytoplasm ratio
Higher ratio = less differentiated cell
Cancer cells tend to have high N/C ratio
What is the cause of follicular lymphoma?
Loss of apoptotic capability -> increased survival of lymphocytes
Tumor arises from germinal center Bcells
BCL-2 often hyperactivated
Common translocation: t(14;18)(q32;q21)
What kind of receptors are GFR?
Tyrosine Kinase
What cancers are HER-1 associated with?
Squamous Cell Carcinoma
Non Small Cell Lung Cancer (NSCLC)
Colon Cancer
What cancers are associated with HER-2?
Breast Adenocarcinoma (ovary, lung, stomach, salivary
What are HER-1 and HER-1?
Both are Human Epidermal Growth Factor Receptors
HER-1 also ERBB1
HER-2 also ERBB2 and NEU
HER family consists of 1-4
What is the result of EGFR activation?
Dimerization, auto (cross) phosphorylation, activation of RAS
How can an increase in number affect cell proliferation?
More receptors available for ligand -> more likely response or amplified response
More recpetors -> constitutive activity (due to numbers/ proximity -> autophosphorylation)
What happens to HER-2 activity that leads to breast cancer?
Ligand independent activation
Gene amplification -> HER-2 overexpression
-> reduced survival
What is GIST and what mutation is it associated with?
Gastro Intestinal Stromal Tumor - most common stromal neoplasm
Mutated EGFR c-Kit (TK domain mutation -> constitutive activity) is almost always present.
What mutation is associated with lung adenocarcinoma and what group is most at risk?
TK domain mutation of EGFR
Female, Oriental, Non-smokers
What mutation is seen in many glioblastomas?
Deletion of EC domain of EGFR
What drugs target EGFRs?
Anti EGFR Ab: Cetuximab
Anti HER-2 Ab: Trastuzumab (Herceptin)
Tyrosine Kinase Inhibitors - target catalytic site
-Iressa (Gefitinib), Erlotinib (Tarceva), Imatinib (Gleevac)
What molecule facilitates Ras return to inactive state?
Neurofibromin
What is the effect of KRAS mutation and what tumors are associated?
KRAS mutation -> constitutively active RAS signaling
Tumors are not responsive to anti-EGFR therapy
Tumors: Pancreas, Colon, Lung, Endometrium, Liver
What causes Neurofibromatosis 1?
Autosomal Dominant disorder -> inactivation of Neurofibromin 1
- > increased Ras activity
- proliferation of nerve sheath cells, cafe au lait spots, nodules in iris
- propensity for malignant transformation (neurofibrosarcoma)
What colon cancer mutations are associated with ineffectiveness of anti-EGFR therapy?
Ras mutation or downstream Ser/Thr kinase (BRaf) mutation
What is an oncogene? Dominant or recessive?
Has cancer promoting ability in heterozygous state
dominant
EGFR, HER-2, Ras
What are tumor suppressor genes? Dominant or Recessive?
Genes that inhibit cancer promoting activity (growth / proliferation)
Recessive - homozygous inactivation is needed for cancer formation
Neurofibromin, Rb
Steps that follow Ras activation
Ser-Thr kinase activation -> increase of transcription factors -> Cyclin D -> low levels of Rb phosphorylation -> Cyclin E -> hyperphosphorylation of Rb -> S phase
How are cyclins degraded?
Ubiquitylation
ubiquitin added to phosphorylated cyclin, targed for proteosome destruction
What is responsible for negative control of cyclin / CDK complexes?
CDKI (CDK inhibitor) - induced by growth inhibitors (TGF-B, p53)
What is the result if CDKI inhibition?
malignancy w/ homozygous inactivation of CDKI gene
What cyclin facilitates passage through the G1 restriction point?
Cyclin D1
2 CDKIs, their activators and inhibitors
P21 - activated by TGF-B (weakly) and DNA damage via p53
- targets CDKs A,B,E
p15 - activated by TGF-B
- targets CDK D
What malignancies are increased levels of CDK 4 associated with?
CDK4: liposarcoma
What malignancies are increased levels of Cyclin E associated with?
Breast cancer
- significantly higher mortality with higher levels of cyclin E
Decreased p27 is associated with a worse outcome in what kind of cancer?
breast
Rb inactivation is seen in what malignancies?
Small cell carcinoma of the lung
breast ca
glioblastoma
Inherited mutations of Rb cause what malignancy?
malignant retinal tumor
Leukocoria
Most common presentation of Retinoblastoma
Eye appears whitish (vs. normal red-eye) under special lighting
2 forms of Retinoblastoma
Sporadic: usually unilateral. Age of diagnosis ~24 mos
Familial: Autosomal Dominant. Bilateral disease. Age of diagnosis ~8mos
Rosettes
Seen microscopically in Retinoblastoma
Rings of undifferentiated cells
What is Loss of Heterogenosity?
In setting of inherited mutation - one gene affected, other is normal. Normal gene is shut down, usually by methylation.
EX: Rb - dominant pattern of inheritance, but molecularly is recessive - both genes must be deactivated for disease to manifest. Penetrance is near 100% due to high rate of LOH
What cancer associated gene type is frequently inactivated by methylation?
Tumor Supressor genes (Rb)
What risk is presented by treating familial Rb with radiation treatment?
500x increased risk of 2ndary tumor
How does low penetrance Rb differ from usual familial Rb?
Low penetrance mutations result in either decreased expression or expression of a partially functional product vs. deletion as seen in the usual familial mutation.
At what rate do mutations occur in normal cells?
1 per 10^-9 or 10^-10 cell divisions
What is the effect of inactivation of house keeping genes?
Mutations in other genes
What is the key ability of a carcinogen?
Ability to oxidize DNA
4 examples of chemical carcinogens and associated turmors.
Aromatic Hydrocarbons:lung, bladder, pancreas, sq. of uper aero digestive (cig. smoke) Asbestos: Malignant Mesothelioma Chemo drugs: Hematologic Malignancies -aklylating agents (Busulfan, Melphalan) Nitrosamines: Gastric
2 naturally occurring carcinogens and associated tumors
Aflatoxin B1: Hepatocellular carcinoma
Bile acids: colon cancer
What malignancies are ionizing and UV radiations associated with?
Ionizing: hematologic, thyroid
UV: skin
3 outcomes of DNA adduct formation
Repair
Cell death
Permanent lesion
What is Benzopyrene?
Procarcinogen found in cigarette smoke. Must be metabolized to BPDE for carcinogenic effect.
What is BPDE?
benzo(a)pyreinediolepoxide.
Carcinogenic product of benzopyrene. Inserts into DNA double helix, distorting and facilitating mutation
3 substances that ROS react with
Fatty acids
Proteins
DNA
Barret’s Esophagus
normal squamous epithelium -> goblet cells due to reflux
May precede dysplasia and invasive esophageal adenocarcinoma
Anti-inflamatories and cancer
May reduce risk.
NSAID: adenoma and colorectal in FAP and sporadic settings
-gastric ca. in pts w/ gastritis
Aspirin: post diagnosis of colorectal ca. lowers risk of recurrence, morbidity and mortality (esp. COX2 tumors)