Week 4: Pancreatic Adenocarcinoma/Liver & other PATH

Question 1

Compare and contrast DNA Polymerase Alpha vs. DNA Polymerase Delta

What is the helpful process that occurs after DNA Polymerase Delta activity?

Answer 1

DNA Polymerase Alpha: low fidelity copying, lacks proofreading, will be replaced

DNA Polymerase Delta: high fidelity DNA copying with proofreading function; reaches RNA primer, displaces it and inserts proper deoxyribonucleotides

MMR is the additional process after DNA Polymerase Delta activity, w/ almost no mutations

Question 2

What are the components of the preinitiation complex?

Answer 2

General Transcription Factors

Question 3

What are the functions of enhancers and silencers?

Answer 3

Enhancers enhance the effect of promoters, can fold in ways to end up near promoter and transcription initiation complex. Alone, they cannot effectively induce transcription but transcription factors can bind to them.

Silencers antagonize the effect of promoters. Repressors can bind to silencers.

Question 4

What are Zn fingers?

Answer 4

DNA binding proteins that hold structure together by coordinating with cysteine side chains

Question 5

What are dimerization domains? What results from their formation? Give an ex.

Answer 5

Proteins that recognize DNA can form homodimers or heterodimers via a dimerization domain to generate a hydrophobic effect

Ex: Leucine Zipper

Question 6

What are the different types of transcription factors? How do they compare?

Answer 6

Activators (bind DNA)
Repressors (bind DNA)

Co-activators (↑ transcription rate but don’t bind DNA)
Co-repressors (don’t bind DNA)

General TF’s: part of Transcription Initiation Complex

Question 7

What happens to RNA immediately after transcription? Why?

What is another event that occurs for a similar purpose? How is the site determined?

Answer 7

Capped w/ 7-methyl guanosine (m7G), required for export

Poly(A)-tail site determined by polyadenylation signal, also required for RNA export

Question 8

What is alternative splicing and how is it modulated?
Is alternative splicing synonymous with mutation?

Answer 8

Physiological process of splicing RNA in different way bc of the presence of different set of splice activator and splice repressor proteins that bind to RNA

Alt splicing changes protein sequence through deletion/addition of residues or via a shift in codon reading frame

Alt splicing isn’t synonymous w/ mutation, even though mutation can generate a new splice site or alter a normally used one so that a cryptic splice site comes into use

Question 9

What is the relationship between antibiotics and protein synthesis?

Give 3 classes of antibiotics (and ex’s) that can inhibit bacterial translation

Answer 9

Selectively inhibit protein synthesis by ribosomes in bacteria rather than human cells

Aminoglycosides: Gentamycin, Tobramycin, Amikacin
Chloramphenicol
Macrolides: Erythromycin, Clarithromycin, Azithromycin

Question 10

What are the 2 main components of Heme?
What are 2 things heme constitutes?

Answer 10

components: protoporphyrin and Fe2+/Fe3+
constituents: CytP450 Enzymes and Hemoglobin

Question 11

Where is most heme made? Where is its secondary source?

Answer 11

Most heme is made in bone marrow, as part of hemoglobin synthesis
Less heme made in liver as cytochrome P450 synthesis

Question 12

Describe the steps in Heme Synthesis: a) general
b) components

Answer 12

Synthesis from succinyl co-A and glycine w/ 3 consecutive condensation reactions that follow.
COOH groups trimmed & concludes w/ Fe insertion

(mit): glycine+succinyl COA-> ALA (->cytosol)

(cytosol) : ALA->
* *Porphobilinogen->
* *Hydroxymethylbilane->
* *Uroporphyrinogen III->
* *Coproporphyrinogen III->

(mit)

• *Protoporphyrin IX** -> +Fe2+
• Heme!*

Question 13

How is Heme synthesis regulated by products from the liver and RBC’s?

Answer 13

Question 14

Describe prophyrias in general terms

What are related lab findings?

Answer 14

Diseases of heme synthesis from enzyme deficiencies in synthesis pathway

PBG in urine/blood
Porphyrins in blood, urine and or feces;
ex: Coproporphyrin
Hydrophilic->Urine; ex’s: Uroporphyrin
Hydrophobic->(Bile)->Feces; ex: Protoporphyrin

Question 15

Describe the pathogenesis of acute attack in AIP
with underlying genetics

Answer 15

PBG deaminase deficiency
AD Inheritance
Haploinsufficiency
Reduced penetrance

Question 16

How can acute AIP present?
Rx?

Answer 16

ALA and PBG: neurotoxic
Seizures, respiratory failure possible
Abdominal pain (abdomen non-tender), anxiety, depression, psychosis
Tachycardia

Tx: ~400 g glucose/dose: hyperglycemia

Question 17

What should AIP patients avoid?

Answer 17

Smoking
Alcohol: induce cyt P450
Drugs metabolized via Cyt P450: ex’s
diclofenac, chloramphenicol, erythromycin, lidocaine, barbiturates, sulfonamides, spironolactone, nifedipine, progesterone, progestins, sulfonylureas
Fasting/low carbohydrate intake (X Atkin’s Diet)

Question 18

How can porphyrinogens become pathologic in Porphyria Cutanea Tarda?

Answer 18

Porphyrinogens can spontaneously form porphyrins
Porphyrins can then leak into blood and reach skin
Light can induce porphyrins to inflict oxidative damage

Question 19

Describe the pathogenesis of PCT and other features

Answer 19

Deficiency of uroporphyrinogen III decarboxylase
that can cause light-induced skin lesions
Liver porphyria (like AIP) but is NOT acute

Question 20

Compare and contrast inherited vs. acquired PCT

Answer 20

Inherited (20%): AD, haploinsufficiency
*Decreased Uroporphyrinogen decarboxylase activity in RBC’s

Acquired (80%): RF’s
Hepatitis C Virus
Smoking
Fe Overload (Hereditary Hemochromatosis)
Excessive alcohol intake (+ another RF)
*Normal Uroporphyrinogen decarboxylase activity in RBC’s: damage only affecting liver​

Question 21

How do porphyrins in urine appear in PCT?

What are other lab findings in PCT?

Answer 21

Dark or fluorescent

↑ total porphyrins in urine
w/ more carboxylated porphyrins (esp uroporphyrin)
than coproporphyrin
mildly ↑ ALA and PBG

Question 22

How is acquired PCT Tx?
Other recommendations?

Answer 22

Treat underlying cause
Phlebotomy for Fe overload

Avoid sun exposure
Beta-carotene: antioxidant effects and can reduce damage

Question 23

Describe the enterohepatic circulation of bile salts?

Answer 23

Distal ileum absorbs primary and secondary bile salts via a Na-driven transporter (ASBT) and releases bile salts into blood so that they can move back to the liver and be re-secreted into bile

Question 24

What are RF’s for cholesterol gallstones?

Answer 24

High bile concentration in gallbladder
Gallbladder empties at low rate
Bile system w/ low motility
Excess cholesterol secretion from fibrates: (gemfibrozil, fenofibrate) ↑ expression of cholesterol export proteins (PPAR alpha TF)
Decreased bile salt secretion from liver dysfunction or decreased bile salt reabsorption

Question 25

What are the Rx's of biliary colic from gallstones?

Answer 25

Surgery * *Ursodeoxycholic Acid**: MOA=? * *Ezetimibe**: inhibits cholesterol uptake

Question 26

Globally, what is the viral agent most responsible for liver disease?

Answer 26

Hepatitis B Virus (Also major cause of Hepatocellular Carcinoma, even in absence of cirrhosis)

Question 27

What is the most troubling aspect of the HBV replication cycle?

Answer 27

cccDNA template doesn't go away even after infection resolves, despite Tx's Can reactivate in immunosuppressed setting

Question 28

Describe the Phases of Chronic HBV Infection

Answer 28

**Immune Tolerant**: usually perinatal but adults also possible; mild histology w/o inflammation * *Immune Active:** when Tx is applicable; active histology; hepatocellular necrosis-\>cirrhosis (possible) * *Inactive (Carrier):** cccDNA still present, risk of developing liver cancer

Question 29

Describe the Natural Progression of Chronic HBV

Answer 29

Question 30

Describe the serologic markers of HBV in stages

Answer 30

Question 31

What is the significance of the gene product **CA19-9** in IHC?

Answer 31

Tumor antigen shed by tumor cells into serum ↑ for many reasons: GI cancer: pancreatic, colorectal; esophageal, HCC also pancreatitis, cirrhosis, bile duct diseases & obstruction BUT NOT for dx purposes bc many false +/-'s

Question 32

What is the significance of the gene product **CEA** in IHC?

Answer 32

Glycoprotein on GI surface during embyronic dev ↑ can signal as tumor marker for many GI malignancies: colon & rectum-most freq also pancreas, stomach, breast, lung, medullary carcinoma of thyroid & ovarian benign ↑: smoking, infections, IBD, pancreatitis, cirrhosis NOT for dx purposes but monitoring, non-SP/SN

Question 33

What is the significance of the gene product **B72.3** in IHC?

Answer 33

tumor associated glycoprotein (mucin like molec) (TAG-72) on cancer cells marker can be shed & enter blood; target for anti-cancer monoclonal antibodies

Question 34

What is a common mutation in pancreatic cancer?

Answer 34

**kRAS mutation:** oncogenic form encodes K-RAS protein-\>uninhib RTK pathways-\>prolif common in pancreatic cancer

Question 35

What is the significance of a p53 mutation?

Answer 35

tumor suppressor gene: "genome guardian;" preserves stability & prevs muts activates DNA repair prots, cell cycle arrest at G1/S interface, apoptosis initation

Question 36

What is the significance of a p16 mutation?

Answer 36

p16 (CDKN2A) mut: tumor suppressor gene; cyclin dependent kinas prevs interaction btwn CDK 4/6 with Cyclin D, inhibiting cell from progressing from G1-\>S

Question 37

What is the significance of the gene product **Smad4** on IHC?

Answer 37

Tumor suppressor gene that encodes a key intracellular transcription factor inv TGF-beta signaling cascade that mediates epithelial cell growth; disruption from missense, nonsense, frameshift mutations 55% of pancreatic cancers w/ mutation or deletion of Smad4 Assoc w/ juvenille polyposis syndrome, ↑ risk for GI cancers (ie: colorectal)

Question 38

What is the significance of the gene product **Mesothelin** on IHC?

Answer 38

Protein encoded by MSLN gene, expressed in mesothelial cells may relate to cell adhesion; overexpressed in tumors incl pancreatic adenocarcinoma, mesothelioma & ovarian tumors interaction w/ other membrane proteins & help peritoneal spread of tumors by cell adhesion

Question 39

Following a Whipple procedure to remove a pancreatic mass, what chemotherapy regiment could be given with post-operative radiation? Describe MOA, DLT/AE

Answer 39

**Gemcitabine** & **Fluorouracil (5-FU)** S Phase Specific Antimetabolites; Pyrimidine Analogues (T/C) Gemcitabine's AE's: flu-like prodrome, diarrhea 5-FU: MOA- inhibits thymidylate synthase DLT: myelosuppresion, mucositis, diarrhea, hand-foot and palmar-plantar syndrome \*Leucovorin & 5-FU synergistically ↑ cytotoxicities

Question 40

What is the chemo drug under preliminary study for pancreatic cancer? Class MOA DLT

Answer 40

**Irinotecan:** S Phase Specific Topoisomerase I Inhibitor MOA: interferes w/ coiling & repair of DNA in S phase DLT: myelosuppresion & diarrhea

Question 41

What are the 1st line agents vs. HBV infection?

Answer 41

**Tenofovir** and **Entecavir**

Question 42

How is unconjugated hyperbilirubinemia measured? Describe it's pathophysiology

Answer 42

Indirect, i ↑ \>80% of increased total bilirubin ↑ bilirubin production; hemolysis, hemolytic anemia (w/ schistocytes), resorbing hematoma: overwhelming conjugation system ↓ glucoronosyltransferase: impaired bilirubin uptake * Gilbert's*: benign no sx; jaundice in times of stress * Crigler Najaar*: premature death in babies who can't conjugate

Question 43

How is conjugated hyperbilirubinemia defined? ​Describe it's pathophysiology

Answer 43

Direct Hyperbilirubinemia ↑ from impaired hepatic secretion, enlarged portal tract may be seen on US extrahepatic obstruction: stones, tumors, strictures obstructive jaundice, physical block of flow into duodenum intrahepatic obstruction: hepatocellular, canalicular, ductular damage \*↓ hepatic uptake of conjugated bilirubin: advanced liver injury\*

Question 44

Compare and contrast Acute Vs. Chronic Hepatitis Time course Lab findings Symptoms

Answer 44

**Acute Hepatitis:** Clinical/biochemical evidence of liver dis \< 6 mo's ↑ aminotransferase (\>1000 IU/L) Low grade fever, N/V, RUQ pain +/- jaundice **Chronic Hepatitis:** Clinical/biochemical evidence of liver dis \> 6 mo's Hyperbilirubinemia, Hypoalbuminemia Early: fatigue, jaundice, pruritus, cachexia Adv: Na & H2O retention-ascites/edema \*Portal HTN: GI bleeding, hypersplenism Synthetic Dysfunction \*Hepatocellular Carcinoma (RF: Cirrhosis)

Question 45

In setting of acute hepatitis, when is hospitalization indicated?

Answer 45

Poor PO intake Encephalopathy Synthetic Dysfunction, ↑ INR (liver failure)

Question 46

What is the #1 cause of acute liver failure in the US? What is the inciting agent? How can it be reversed?

Answer 46

Drug Induced Liver Injury (DILI) Acetaminophen N-acetylcysteine

Question 47

What is the most common cause of ↑ LFT's in blood donors and "cryptogenic cirrhosis?" Give risk factors How would you differentiate between its two types?

Answer 47

Non-Alcoholic Fatty Liver Disease RF's: Dyslipidemia, Obesity, Non-insulin dependent Diabetes, Glucose intoleerance Histologically resembles alcoholic liver disease; liver biopsy differentiates *steatosis* vs. *steatohepatitis* **Steatosis:** fat (-) inflammation, (-) fibrosis, assumed non-progressive **Nonalcoholic Steatohepatitis (NASH)**: fat + inflammation, central hyaline sclerosis (chicken-wire fibrosis), assumed progressive, acute inflammatory cells (PMN's) even though chronic diease, mallory hyaline, balloon liver cells

Question 48

What liver condition does this represent?

Answer 48

**Steatosis** Fat w/o inflammation No fibrosis (Non-progressive)

Question 49

What liver condition does this represent?

Answer 49

**Nonalcoholic Steatohepatitis (NASH):** fat + inflammation, central hyaline sclerosis (chicken-wire fibrosis), assumed progressive, acute inflammatory cells (PMN's) even though chronic diease, mallory hyaline, balloon liver cells

Question 50

For **fulminant hepatic failure**, note: Time Course Causes Lab Px Tx Note?

Answer 50

Within 6 weeks of liver disease onset (jaundice), encephalopathy (confusion/frank coma) Causes: DILI, viral hepatitis, *toxins* (**Amanita**-fungus) Lab: Elevated aminotransferases and INR Px: Cerebral Edema, usual cause of death Tx: supportive management, emergent liver transplant Note: Bilirubin will be ↑ bc of liver failure, can't excrete bc of liver necrosis

Question 51

Autoimmune Liver Diseases **Primary Biliary Cholangitis (PBC) vs. Primary Sclerosing Cholangitis (PSC)** EPI Lab Serology Dx Tx

Answer 51

Question 52

Describe *biliary colic*

Answer 52

Intermittent obstruction of cystic duct

Question 53

Describe *acute cholecystitis* How is it diagnosed?

Answer 53

cystic duct obstruction but no px of jaundice bc flow from liver unimpeded HIDA Scan

Question 54

When is surgery indicated for acute cholecystitis?

Answer 54

RUQ pain, fever, WBC count that doesn't improve

Question 55

Describe ascending cholangitis What procedure can be performed?

Answer 55

CBD obstruction, so obstructive jaundice possible ERCP can extract impacted stone

Question 56

What is the most common cause of **acute pancreatitis** in the US?

Answer 56

Gallstones

Question 57

What are 4 types of liver cells?

Answer 57

Hepatocytes Stellate Endothelial Kupffer Cells

Question 58

What is the condition when Fe is found in the liver and the spleen?

Answer 58

Hemosiderosis

Question 59

What is the condition when Fe is found in the liver and the pancreas?

Answer 59

Hemochromatosis

Question 60

Although PSC doesn't have specific Tx, if cholangitis develops-how should patient be managed?

Answer 60

Antibiotics and decompressions w/ ERCP

Question 61

How would *acute cholecystitis* present on HIDA scan?

Answer 61

Absence of gallbladder visualization, sign that cystic duct is blocked Liver and small intestine will fill but gallbladder won't\*

Question 62

Describe bile salt synthesis

Answer 62