L7 Stem Cell Therapies Flashcards
What are stem cells?
Undifferentiated cells that are capable of self-renewal and have the potential to differentiate into various cell types
Which are more potent: embryonic or adult stem cells?
Embryonic stem cells (pluripotent)
Most valuable source of embryonic SCs?
Amniotic fluid
Blood from umbilical cord consists of which stem cells?
Haematopoietic and mesenchymal SCs
Which are more potent: haematopoietic or mesenchymal stem cells?
Haematopoietic
Most frequently used source of mesenchymal SCs?
Bone marrow
Where do stem cells come from?
- amniotic fluid
- human umbilical cord
- bone marrow
- adipose tissue
First generation stem cells
- Haematopoietic (multipotent)
- Mesenchymal (multipotent)
Most commonly used stem cell type
HSC
Bone marrow transplants containing __ have been used to treat haematological cancers.
HSCs
Advantage of MSCs
Much easier to isolate and produce a higher yield compared to other SCs
What properties do MSCs possess?
- immunomodulatory
- anti-inflammatory
- angiogenic
- anti-apoptotic
- trophic
Mesenchymal stem cell therapy used in Europe for treating fistulising Crohn’s disease
Alofisel
Second generation stem cells
- Embryonic
- Induced pluripotent
Examples of embryonic stem cell therapies
- Pluripotent derived retinal pigment epithelium to treat age-related macular degeneration
- Oligodendrocytes for spinal cord injuries
How are iPSCs formed?
When the adult cells are cultured with embryonic SCs, forming new cells with SC-like properties
What may occur as a result of the reprogramming process to iPSCs?
Chromosomal abnormalities
2 categories of next generation stem cells
- Use as delivery vehicles for therapeutic drugs
- Use as enhanced therapeutic agents themselves
Tools to create next generation stem cells
- Virus-mediated transduction
- Gene editing tools e.g. CRISPR-Cas
- Chemogenetics (DREADDs)
- Optogenetics
- Copper-free Click Chemistry
Transduction of SCs with exogenous genes can be used to…
- drive expression of proteins not normally expressed in SCs
- treat haematological cancers using CARs
- control cell signalling pathways using optogenetic actuators
- increase expression of proteins normally expressed in SCs
- express WT proteins as a mechanism to functionally compensate for genetic mutations
What is the safest viral vector to use to facilitate stable long-term expression of a given exogenous gene, and why?
Lentivirus because it preferentially integrates into transcriptional unit - less likely to disrupt TSGs & protooncogenes
What is Kymriah?
An immunocellular therapy containing tisagenleleucel, autologous T cells genetically modified ex vivo using a lentiviral vector encoding an anti-CD19 CAR (enhances patient’s T cell response against tumour antigens)
Kymriah indications
- B cell acute lymphoblastic leukaemia in patients up to age 25 whose cancer did not respond to previous treatment, and has come back at least twice
- Diffuse large B cell lymphoma in adults whose cancer has come back or did not respond after 2 or more previous treatments
What is optogenetics?
Use of light-responsive proteins to activate cell signalling pathways when exposed to specific wavelengths of light
Explain how Copper-free Click Chemistry works?
- Nanoparticles loaded with chemotherapeutic paclitaxel and cyclooctyne
- MSCs coated with azide
- MSCs migrate to tumour site. Azide binds nanoparticles that have cyclooctyne.
- Click chemistry reactivity with cyclooctyne ensures paclitaxel reaches tumour site efficiently
Stem cells have a natural tropism for __
tumour cells
Two types of stem cells commonly used for drug delivery
Neural SCs and MSCs (little to no immunogenicity)
SCs are packaged with the following anti-cancer agents…
- Prodrug converting enzymes
- Apoptosis-inducing factors
- Oncolytic viruses
How does using SCs for drug delivery affect systemic toxicity?
They reduce systemic toxicity
Example of SCs delivering a prodrug converting enzyme
Retroviral transduction of NSCs and MSCs to induce expression of cytosine deaminase allows for the systemic administration of the non-toxic prodrug 5-fluorocytosine, which is converted at tumour site (to which SCs have migrated) into the highly toxic chemotherapeutic 5-fluorouracil
3 main groups of anti-metabolites
- Folate antagonists: methotrexate
- Pyrimidine analogs: Floxuridine
- Purine analogs: thiopurines, mercaptopurine
Chemotherapeutic approaches to treat glioblastoma multiforme targeting __ factors have failed to produce clinical benefit.
angiogenic
NSCs engineered to express __ have been shown to be well-tolerated in a small Phase I trial in patients with high grade recurrent glioma.
cytosine deaminase, a prodrug converting enzyme
What is being tested in clinical trials as an alternative therapeutic approach for high grade glioma?
Intracerebral injection of NSCs engineered to express human carboxylesterase (hCE1m6), which converts irinotecan to the highly potent SN-38
Examples of approved topoisomerase inhibitors
Irinotecan and topotecan
An example of using SCs to deliver apoptosis-inducing drugs
Recent small Phase I trial used autologous bone marrow-derived MSCs engineered to express the suicide gene encoding HSV-tk in patients with advanced GI adenocarcinoma. HSV-tk converts the prodrug ganciclovir to the toxic ganciclovir triphosphate, which induces apoptosis in actively proliferating cells.
Bystander effect of toxic metabolite ganciclovir triphosphate
Toxic metabolite also taken up by neighbouring cells within the TME, resulting in further tumour cell death
How do oncolytic viruses work?
Viral vectors that infect solid tumour cells, replicate and cause tumour cell lysis and release viral progenies which infect neighbouring tumour cells
Example of an onolytic immunotherapy
Talimogene laherparepvec (T-VEC) is a genetically modified, HSV type 1-based oncolytic immunotherapy approved for the treatment of melanoma with metastatic lesions in skin & LNs
Advantage of packaging OVs within SCs
To shield the OVs from physiological mechanisms that may limit their biodistribution and effectiveness
Use of stem cells as therapeutics
- Immuno-oncology
- Tissue repair
- Gene therapy
Future work using iPSCs will hopefully allow potential to…
create ‘off-the-shelf’ antigen-specific immunotherapies
Modified allogeneic bone marrow-derived MSCs transfected with __ currently being investigated in Phase II trials for TBI
Notch intracellular domain
NSCs that have been engineered to constitutively express __ are currently in Phase II trial for ALS
glial cell-derived neurotrophic factor (GDNF)
What is Strimvelis?
- Stem cell-based gene therapy approved by EMA for the treatment of ADA-SCID
- Autologous HSCs transduced with a retrovirus which encodes ADA enzyme
What is Zyntelgo?
- EMA approved autologous HSC-based therapy for the treatment of β-thalassaemia
- Introduces functional copies of β-globin gene→less frequent blood transfusions
A way to reduce immunogenicity in iPSCs
Reduce HLA expression on the surface of stem cells to make them less recognised by NK cells, T cells & macrophages
Why are stem cell therapies for oncology under the greatest scrutiny?
- Because stem cells share common molecular features with cancer cells
- MSCs have angiogenic and immunosuppressive properties which may promote tumour growth
