Epigenetics and Cancer

Question 1

What are epigenetics?

Answer 1

• mechanisms that regulate gene expression
• ex. methylation, histones and histone acetylation, histone variants that alter chromatin structure, mRNA degradation induced by microRNAs

Question 2

Proteins involved in epigenetic DNA regulation

Answer 2

• DNA methyltransferases
• Histone modifiers
• Chromatin remodelers

Question 3

How do methyltransferases function?

Answer 3

• methyl groups on CpG islands inhibit gene transcription
• also increase binding of transcriptional repressors

Question 4

Is the DNA in our nucleus organized in linear strands?

Answer 4

• no
• wrapped around proteins (histones)
• histones form fibres called chromatin
• chromatin unwinds when necessary so transcription or replication is necessary

Question 5

Which enzymes are considered the “writers” and “erasers” for histone modification?

Answer 5

Writers
- histone acetyltransferases
- histone methyltransferases
Erasers
- histone deacetylase
- histone demethylase

Question 6

What do epigenetics have to do with cancer?

Answer 6

• cancerous cells are found to have global irregular epigenetic landscapes
• very common for cancerous cells to have many mutations in genes coding for epigenetic regulators

Question 7

What type of cancer are we focusing on learning?

Answer 7

• cutaneous squamous cell carcinoma (cSCC)

Question 8

3 types of cells in the epidermis

Answer 8

keratinocytes - epithelial cells
melanocytes - synthesize melanin
langerhans cells - immune protection

Question 9

Functions of epidermis

Answer 9

• prevents water loss
• protection against chemicals, pathogens, UV radiation, and physical insults
• temperature regulation
• electrolyte balance

Question 10

What is basal cell carcinoma?

Answer 10

• most common form of skin cancer
• transformation of the basal keratinocytes
  Etiology - chronic UV exposure, ionizing radiation

Question 11

What is melanoma?

Answer 11

• 4% of all cancers in canada
• very aggressive and highly metastatic
• transformation of melanocytes
  Etiology - chronic UV exposure, familial mutations

Question 12

What is cutaneous squamous cell carcinoma?

Answer 12

• accounts for 20% of all skin cancers in canada
• second most cancer in humans
• transformation of epidermal stem cell keratinocytes in basal layer of skin or hair follicles
  Risk factors - UV radiation, immunosuppression

Question 13

Organization of epidermis cells from superficial to deepest

Answer 13

• Corneocytes
• Granular keratinocytes
• Spinous keratinocytes
• Basal layer (stem cells and transit amplifying cells)