Cancer treatment modalities and therapy options

• Current treatment modalities and new therapy options for cancers from gene to cell therapies.

Why Cancer Is Hard to Treat

• Cancer sustains proliferative signalling, evades growth suppressors, resists cell death, enables replicative immortality, induces angiogenesis, and activates invasion and metastasis.
• Properties of cancer cells include clonal origin, immortality, genetic instability, uncontrolled cell proliferation, loss of contact inhibition, metastasis, invasion, and angiogenesis.
• Cancer development occurs through tumor initiation and progression involving mutations and selection for rapid growth.

Targeted Therapies

• Targeted therapies aim for cancer selectivity to minimize "off-target" effects.
• Antisense therapies, apoptosis agonists, immunotherapy, tyrosine kinase inhibitors, ligand-targeted cytotoxins, angiogenesis inhibitors, and metalloproteinase inhibitors are examples of these therapies.

Gene Therapy: Basic Principles and Advances

• Gene therapy aims to fix medical conditions or illnesses resulting from flawed genes by introducing a normal, functioning copy of the gene to help affected cells, tissues, and organs work properly, differing from traditional drug-based approaches that only treat the problem without repairing the genetic flaw.
• Successful gene therapy can fix a problem at its source, but is not a simple solution and requires more research to realize its full potential

Historical Highlights of Gene Therapy

• 1968: Rogers & Pfuderer demonstrated proof-of-concept for virus-mediated gene transfer.
• Steven A. Rosenberg conducted the first officially approved gene transfer into humans.
• China was the first country to approve a gene therapy based product for clinical use.
• EMA recommended a gene therapy product for approval in the EU for the first time.

Gene Therapy Targets

• Gene therapy treats disorders by repairing underlying genetic flaws, but not all conditions are suitable for this approach.
• Key questions to consider for a candidate disorder:
  • Does the condition result from mutations in one or more genes?
  • Which genes are involved, and is a DNA copy available?
  • What is known about the biology of the disorder?

Gene Delivery

• To design the best possible approach, one needs to learn all they can about hot the gene factors into the disorder. For example
  • Which tissues are affected?
  • What role does the protein encoded by that gene play within the cells of that tissue?
  • Exactly how do mutations in the gene affect the protein's function?

How Gene Therapy Affects Tissue

• It is important to consider if adding a normal copy of the gene fix the problem in the affected tissue as mutated genes may encode a protein that prevents the normal protein that function this way are called dominant negative.
• The tissue must be accessible via skin, blood or lungs rather than internal organs and a suitable mode of delivery must be found

Hallmarks of Successful Gene Delivery

• Target the right cells to ensure the gene gets into correct cells
• Activate the gene by transcribing and translating it to produce a functioning protein.
• Integrate the gene into to host cell's genetic material to ensure it continues working in the target cells or survives
• Avoid harmful side effects such as toxicity or immune responses that could make future therapy rounds ineffective.

Gene Therapy Options

• Somatic-cell gene therapy repairs or replaces defective genes in some or all body cells of an individual.
• Germ-line gene therapy repairs or replaces defective genes in germ-line cells, causing the repaired gene to be inherited.

Somatic Cell Gene Therapy Categories

• Ex vivo: cells removed from body, incubated with vector and gene-engineered cells, then returned to the body.
• In situ: vector is placed directly into the affected tissues.
• In vivo: vector is injected directly into the bloodstream.

Vectors

• There is no "perfect vector" to treat every disorder, a gene therapy vector must be customized to address unique features
• Vectors can be viral or non-viral and must be chosen to treat the disorder effectively

Viral Vectors

• These vectors utilise the blue print of a virus, and access cells of the body
• During creation non-essential parts are removed and replaced, to stop viruses producing an infection
• Mostly preferable vectors in clinic trials include Retroviruses including lentivirus, adenovirus, adeno-associated virus, herpex simplex virus

Non-Viral Vectors

• These vectors, which are not based on a irus, introduce genetic material physically or chemically

Types of Vectors

• RNA viruses (Retroviruses)
  • Murine leukemia virus (MuLV)
  • Human immunodeficiency viruses (HIV)
  • Human T-cell lymphotropic viruses (HTLV)
• DNA viruses
  • Adenoviruses
  • Adeno-associated viruses (AAV)
  • Herpes simplex virus (HSV)
  • Pox viruses
• Non-viral vectors
  • Liposomes
  • Naked DNA
  • Liposome-polycation complexes
  • Peptide delivery systems

Most Commonly Used Viral Vectors

• Viruses are an efficient means of delivering foreign genes into cells and can be modified to deliver genes without making people sick.

Viral Vectors: Advantages

• Good at targeting and entering cells.
• Can be engineered to target specific cell types.
• Can be modified so that they cannot replicate and destroy the cell.

Viral Vectors: Drawbacks

• Limited in how much genetic material it can contain.
• Can cause immune responses in patients: patients may get sick and a patient's immunity to a virus may prevent from responding to repeated treatments/

Gene Delivery Strategies

• Increase product potency to allow a reduced gene therapy dose to avoid immune response.
• Wrap the viral vector in an extracellular vesicle to hide it from the immune system.
• Alter viral capsid proteins to help them evade T cells.

Targeting of Different Organs By Viral Vectors

• Adenovirus targets tumors and hematopoietic cells.
• Retrovirus targets tumors, stem, and hematopoietic cells.
• AAV targets the liver, muscle, and retina.
• Alphavirus and polymer-coated adenovirus target tumors.
• Liposome-encapsulated alphavirus provides systemic delivery.
• Lentivirus targets the CNS, liver, and muscle
• Herpes simplex virus targets the CNS, PNS, muscle, hematopoietic, and stem cells.

Oncolytic Viruses

• Engineered oncolytic viruses (OVs) activate the immune system, releasing interleukins or chemokines after tumor cell infection.
• Co-administered checkpoint inhibitors prevent immune response inhibition, ensuring immune cells are activated against tumor cells (APC, antigen-presenting cell).

Impediments to Virotherapy and Ways To Solve This

• Tumor is difficult to treat with normal methods as tumor cells can hide within the connective tissues
• Solutions for this can be inducible and tissue specifies promoters, and suicide gene therapy

Strategy for Gene Transfer

• Transferring a gene involves regulators for tissue specificity, expression amounts and controlled cDNA, which is protein coding

Non-Viral Vectors

• Although viruses can effectively deliver genetic material to the cell , they can have limitataions
• They may not generate an imune response

Non -Viral Vectors

• Liposome
• Cationic polymers
• Naked DNA
• Peptide-mediated gene delivery
• These vectors make it easier to hold therapeutic DNA

Liposomes

• Lipids in water produce liposomes: microscopic sacs with a lipid bilayer that deliver DNA
• No immune response occurs in patients
• Efficiency is lower than for viral vectors

Translation To The Clinic

• Moving gene therapy from the lab to the clinic takes steps and time for approval for regulatory bodies.
• To be approved researchers must
  • Understand the biology behind the disorder
  • Develop the treatment approach
  • Test its effectiveness in biological models of the disease
  • Establish its safety in humans

Why Gene Therapy Approval Takes So Long

• Gene therapy techniques were just emerging when researchers began designing gene therapies for ADA deficiency.
• Although researchers employed the latest technologies at the time, but the therapies were far from perfect.
• Several major obstacles need to be overcome before successful gene therapies are developed.
• Gene therapies will become more effective as researchers learn more about how the human body works at the molecular level.

Clinical Trials and Common Vectors

• A large percentage of clinical trials are on cancer, 3704 trials, then immune and digestive system diseases, and genetic disorders
• Common vectors are retrovirus and adenovirus

Common Vectors Used In The Clinic

• Adenovirus
• Retrovirus
• Vaccinia virus
• Poxvirus
• Adeno asscoaited virus
• Herpes simplex virus
• Lentiviral
• Other categories
• Linknown

Gene editing : Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)

• This is a system with powerful programmable nucleases to edit the gene and knockout, transcription activator-like effector nucleases
• Difficulties in the system are delivering correctly to cells, the frequency of modification may be low and cutting at off target sites

CRISPR/Cas9 system

• CRISPRs are regions in the bacterial genome that help defend against invading viruses, composed of short DNA repeats and spacers.
• When a previously unseen virus infects a bacterium, a new spacer derived from the virus is incorporated amongst existing spacers.
• The CRISPR sequence is transcribed and processed to generate short CRISPR RNA molecules which then associate with and guide bacterial molecular machinery to a matching target sequence in the invading virus and cut

Gene Editing Tools Used In Crispr

• Target DNA: Region of the genome to be modified.
• Cas9: A bacterial enzyme that unzips and cuts the target DNA.
• PAM sequence: A DNA sequence required to define the cutting site.
• Guide RNA: A fragment of RNA that binds to Cas9 and leads Cas9 to the desired location to edit the genome.

Crispr Method Of Action

• First there must be a target DNA matching genome sequence, then a cut, then guide RNA helps facilitate and PAM speeds up the process

Gene Therapy :Current Challenges

• Gene therapy is not new, but has only seen limited success why,because gene delivery and activation are not easy, also there are problems with delivering it to the germline, the immune system, and disruption from the cells

Cell Therapy : An Alternative

• Stem cells are also being used to treat patients diseases and conditions

Sem Cell Derived Therapeutics

• Sem cells treat; leukemia and sickle cell, stroke parkinsons
• Sem cells can treat cirrhosis
• sem cells have high regenerative qualities for muscle and other tissues

Stem Cell Therapy

• Stem cells can be genetically modified to target tumor cells even when metastatic or invasive, there are high quantities of proteins which is important in research

Therapuetic Cells

• Tumour cell can secrete proteins with the help of immune cells and fibroblast cells , and stem cells

Fight Cancer With Cancer

• Cancer cells have 'self-homing' properties, whereby they can track cells of their own kind within an organ and throughout the body.
• The homing property can be implemented to deliver therapeutics
• This can be achieved through CRISPR or similar processes

CAR-T Cell Therapy

• T cells are engineered to find cancer cells
• This is done by putting genes causing special receptors for the modified T cells
• The modified T cells are then sent to a lab where a multiplication occurs
• The multiplied cells attack the cancer

CAR-T Cell Therapy

• Cancer must be selected, and tumour antigens must be found
• Receptors must be designed
• Immune cells are key
• Expansion must be determined for the cells

CAR-T for Solid Tumours and T-cell Activation

• Cancer cells are targeted to the tumour to suppress the micro environment cells