MicroRNAs

1
MicroRNAs

• Andrew Teich

2
miRNA

• Scattered throughout genome (except Y chromasome)
• RNA that gets transcribed but does not code for a
  protein
• Causes modification of protein expression of
  other RNA transcripts

3
miRNA Genesis

• miRNA region of DNA transcribed by RNA polymerase
  2 to produce a primary-miRNA (pri-miRNA)
• pri-miRNA forms a specific hairpin-shaped
  stem-loop secondary structure and is subsequently
  cleaved/processed to form the precursor of mi-RNA
  (pre-miRNA)

4
(No Transcript)
5
miRNA Genesis 2

• pre-miRNA is then transported to the cytoplasm by
  Exportin-5, and further processed to a short,
  double strand miRNA (about 22 nucleotides)
• One strand is incorporated into RISC (RNA induced
  silencing complex) argonaute is the
  catalytically active protein site

6
RISC Function

• Good fit between RNA and mRNA target cleavage
• Moderate fit between RNA and mRNA target can
  blockage
• Up to 30 of our genes are regulated by RISC
  (i.e. via miRNA)

7
(No Transcript)
8
miRNA and Cancer

• Cancer is a multi-step process
• Anything that alters one of these processes could
  be implicated in oncogenesis
• First cancer associated with miRNA was CLL
  (miR-15a and miR-16a deletions)
• These miRNAs were shown to silence BCL-2
  (anti-apoptotic factor)

9
(No Transcript)
10
(No Transcript)
11
(No Transcript)
12
(No Transcript)
13
miRNA and Cancer

• Cancer is a multi-step process
• Anything that alters one of these processes could
  be implicated in oncogenesis
• First cancer associated with miRNA was CLL
  (miR-15a and miR-16a deletions)
• These miRNAs were shown to silence BCL-2
  (anti-apoptotic factor)

14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
Detecting miRNA

• Northern Blot (problem low throughput)
• Microarray
• RT-PCR

18
Lung Cancer

• Most common cancer in the United States
• Many risk factors (asbestos, radiation,
  occupational hazards), but all pale in comparison
  to smoking
• 60 incurable when detected
• Many possible presentations
• Major types Non small cell (Adeno, squamous) vs
  Small Cell

19
Adenocarcinoma

• Comprises about 1/3 to 1/2 of all lung cancers
• Grossly often appears as a diffusely infiltrating
  mass
• Can track along alveoli (BAC) before becoming
  invasive

20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
Squamous Cell Carcinoma

• Comprises about 30 of all lung cancers
• Most cases are centered in segmental bronchi
• Keratin is commonly seen in these tumors, which
  is produced by normal squamous cells
• Many subtypes based on morphology well,
  moderately, and poorly differentiated based on
  keratin

24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
(No Transcript)
32
Avastin

• Tumor formation requires neovascularization
• VEGF is an important promoter of
  neovascularization
• Avastin is a monoclonal antibody to VEGF
• Pulmonary hemorrhage has been shown to occur in
  patients with squamous but not adenocarcinoma
  when treated with avastin