Biological therapies for cancer treatment Flashcards
What is CRISPR
Clustered repeated interspaced short palindromic repeats
Definition: Genome editing technology that allows for precise alterations to DNA.
Components: Cas9 enzyme (cuts DNA), guide RNA (targets specific DNA sequences).
Process: Guide RNA directs Cas9 to the correct part of the DNA to be cut, enabling editing.
What is CRISPR/Cas9
Clustered repeated interspaced short palindromic repeats (CRISPR)/Cas9 is a powerful gene editing tool that enables editing parts of the genome by removing, adding or altering sections of the DNA sequence.
How does Crispr-Cas 9 system work
The CRISPR-Cas9 system generates a Cas9-mediated double-strand break (DSB) guided by a single guide RNA (sgRNA).
The DNA breaks can be repaired either via a homologous recombination (HR)-mediated repair pathway or via the nonhomologous end-joining (NHEJ) repair pathway, leading to precise or imprecise genome editing, respectively
What are the two kinds of CRISPR/Cas9 editing? (Two repair mechanisms)
NHEJ
HR
Describe the nonhomologous end-joining (NHEJ) repair pathway
The NHEJ pathway is error prone and repairs the DSB by generating insertions and/or deletions at the cleavage site that disrupt the targeted gene
Describe the homologous recombination (HR)-mediated repair pathway
Homologous recombination (HR) is a mechanism for the repair of double-strand breaks (DSBs) in DNA.
Extra:
Homologous recombination (HR) is a DNA repair process used to fix double-strand breaks by using a sister chromatid as a template to ensure accurate repair. The process begins with the resection of DNA ends, followed by strand invasion assisted by the RAD51 protein, which facilitates the formation of a D-loop where new DNA synthesis occurs. Finally, the resolution of the D-loop and associated structures restores the integrity of the DNA, maintaining genomic stability.
Compare the NHEJ and HR pathway
The NHEJ pathway is error prone and repairs the DSB by generating insertions and/or deletions at the cleavage site that disrupt the targeted gene. Unlike HR-mediated repair pathways, the NHEJ repair pathway does not require a homologous DNA template, which simplifies genome-editing procedures.
How CRISPR is used to perform genome editing in cancer
- Knock-out = disrupts the gene
- Alter the gene sequence to change the function
In cancer hypermethylation in the promotor region leads to Tumour suppressor gene (TSG) silencing.
DNA hypermethylation = P16 mutations. - Applications: Targeting oncogenes for disruption, correcting mutations in tumor suppressor genes.
- Outcomes: Can disable cancer growth drivers or introduce new genetic material to combat cancer.
What are the challenges of using CRISPR for cancer treatment?
Delivery Issues: Difficulty in targeting all cancer cells specifically.
Off-target Effects: Potential unintended genetic modifications.
Ethical/Regulatory Concerns: Ethical debates and rigorous regulatory standards.
What are some current and emerging biological therapies?
CRISPR-Cas9: Targeting oncogenes for disruption, correcting mutations in tumour suppressor genes.
CAR T-cell Therapy: Modified T cells to attack cancer cells.
Checkpoint Inhibitors and Oncolytic Viruses: Enhance immune response against cancer or use viruses to kill cancer cells.
How do biological therapies (antibodies) differ from small molecule treatments?
Biological Therapies: Large molecules like antibodies; high specificity, usually work outside or on cell surface.
high selectivity
‘on target’ toxicity effects
Small Molecules: Smaller, can enter cells easily; target pathways inside cells.
Less selectivity
‘on and off target’ toxicity effects
What are the strengths of biological therapies?
- antigen specificity, limited/fewer or no off-target effects
- Toxicity relates to on-target, off tumour toxicities
- Drug interactions: mostly pharmacodynamic
- Long acting
- Can be highly effective against diseases that are difficult to treat with small molecules
Strengths: Specificity, lower toxicity, can target new pathways.
What are the limitations of biological therapies?
- Require cell surface or soluble receptor targets
- Parenteral – oral has limited systemic applicability
- Long acting
- Immunogenicity
- High cost of development and production
- May require complex delivery mechanisms
Limitations: High cost, complex manufacturing, potential immune reactions.
What is antibody resistance?
Definition: When cancer cells change in response to antibody treatment, reducing effectiveness.
How is cancer resistance acquired?
Mechanisms: Loss or change of target antigen, activation of alternative pathways.
e.g.
Loss of the extracellular binding domain = Pathways become activated again and the cancer comes back
- Genetic mutations in cancer cells that alter the antibody target.
- Upregulation of other pathways that help the tumour survive despite the therapy.
Management: Use of combination therapies, development of new antibodies.
