1. Lecture 8: Gene Therapy and Nanomedicine
Contents:
Cancer and Gene Therapy
Genes
Mutations and Cancer
Gene Therapy
Nanomedicine for Gene Therapy
Conclusions

2. Cancer and Gene Therapy
DNA contains all the genetic instructions for the body.
Cells use these DNA instructions to create hormones, proteins, chemicals and other macromolecules needed for the body to function.
To be more efficient in its use of materials, the body signals cells to differentiate into more specialized cell types, making different cells proficient at different tasks.
A complex system of chemical signals regulates the function of cells in the body by signaling certain cell types to do one of four things: make more of something, make less of something, multiply, or die-off.

3. Cancer and Gene Therapy (continued)
Sometimes a cell may be damaged more than it can self-repair, in which case that cell could be signaled to die-off (or other specialized cells signaled to destroy it), so that other healthy cells in the surrounding tissue can multiply to take its place.
As we discussed in the previous lecture, damage to DNA can occur by exposure to UV light, x-rays, viruses, mutagenic chemicals, or reactive oxygen species.
The two matched strands of DNA offer some redundancy that allows small errors to be detected and repaired most of the time.

4. Cancer and Gene Therapy (continued)
However, sometimes damage occurs that goes undetected and uncorrected, resulting in a small mutation.
Because differentiated cells multiply by growing and splitting into two identical copies, every subsequent copy will retain this small mutation.
Differentiated cells only read the sections of DNA related to the specific tasks they carry out, so as long as those sections of DNA are undamaged,, the cells can continue their work without trouble.
When mutations occur on the often-used portion of a differentiated cell's DNA instructions, problems can occur.

5. Cancer and Gene Therapy (continued)
DNA mutations lead to errors in instructions for the proteins and other products created by the cells.
Proteins built with faulty instructions might be missing key components that affect their form and function, leading to flawed proteins.
The complex system of chemical signals becomes disrupted by these flawed proteins.
If the original protein acted as a "produce-less" signal, then flawed versions would not function properly, resulting in the recipient cells not getting that signal and leading to over-production of their product.

6. Cancer and Gene Therapy (continued)
Cancer is characterized by uncontrolled cell growth, which can be caused by a large number of possible signal disruptions.
Most simply, if cancer cells have awed "die-off" signal receptors, then the cells will multiply beyond their intended limit, but won't be culled back to this limit as the signal system intends.
The outcome is that cancer cells multiply at a faster rate than healthy cells, eventually outnumbering the healthy cells.

7. Introduction to the Gene Therapy
Gene therapy is defined as the transplant of normal genes into cells in place of missing or defective genes in order to cure genetic disorders.
When a problem arises, the only way to deal properly with genetic diseases is to fix the source of the problem.
Gene therapy is an approach to medicine that can attack the problems that humans have by going straight to the source.
The new genes that are introduced into the cell can then change the DNA or RNA transcript that is used to create proteins, which will then correct the disease.

8. What are Genes?
Genes in a strict definition are working subunits of DNA that act as instructions to make proteins.
There are about 100,000 of these genes in our body.
It has been estimated by the Human Genome project that 20,000 to 25,000 of these genes are responsible for basic physical and functional units of heredity.
Being units of heredity means that these genes are going to be responsible for things such as the color of our eyes and features that make individuals unique.
These genes are responsible for more than just our physical features – they are responsible for how our bodies work.

9. Gene Mutations
Genes are responsible for how healthy our body stays, and they are also responsible for the defects or diseases that our bodies may have to deal with.
Our bodies get these defects from gene mutations.
Genes get their mutations during the process of cell replication – mitosis, which itself has several stages.
During mitosis, all of the DNA is replicated so that the new cell also has a copy, but the DNA is not always replicated perfectly.
The DNA mutation is a process where incorrect ‘reading’ of RNA happens during the transcription event.
There are three major types of DNA mutations: nonsense, missense and frameshift mutations. Mutations are the cause of some of the most problematic diseases, such as Huntington’s, type I diabetes, most heart diseases, and cancer.

10. Mutations and Cancer
The gene mutation that has been linked to and thought to be responsible for over 50% of cancers is the p53 gene.
This gene is responsible for the actions that cell has to take when it is mutated or damaged.
It can either tell the cell to repair the DNA or to start its death as shown on the diagram.
In the case of cancer, the p53 gene is mutated and is not doing its job, so the damaged cell keeps replicating and growing.
With gene therapy we could possible fix this issue.
Representation of p53 gene function.

11. Gene Therapy Gene therapy replaces the mutated genes by normal ones.
These transplanted genes can do the following: (1) the DNA strand can be completely replaced; (2) the DNA can be used to knock out mutated DNA; or (3) it can be used to introduce a new gene into a cell in order to help it fight diseases.
The delivery of new genes is normally done through a carrier or virus.
The virus can inject its DNA into the hosting cell nucleus.
In doing so, the virus must get through the endosomal process.
This is the process that protects the cell nucleus from being hi-jacked by something like a virus.
Normally this is not a problem for the virus, since it is coated with a protective outer layer that tricks the endosome.
An endosome is a membrane-bound compartment inside eukaryotic cells.

12. Gene Therapy (continued)
Gene therapy by using a virus as carrier of the DNA can be arranged in two modes: inside or outside the body.
In the inside treatment, the virus that carries the gene is injected directly into the part of the body that has the defective cells.
In the outside treatment, the blood of bone marrow is taken from the patient, and the immature cells are removed.
Then the new genes are added to the cells and injected back into the bloodstream. The cells can then travel to the bone marrow to mature and multiply rapidly, and then replace all of the defective cells.

13. Examples of Gene Therapy
Both the inside and outside the body treatments have been used to treat a wide variety of diseases.
Inside the body gene therapy takes advantage of the fact that viruses tend to infect certain organs. For example, in order to treat hemophilia, doctors tend to the adeno-associated virus.
This virus goes straight to the liver when it is in the blood stream, causing the liver to add more blood-clotting factors into the blood, which cures the hemophilia.
Outside the body gene therapy has been applied to treat severe immunodeficiency diseases by using retroviruses. These viruses are effective in inserting their genes into the DNA of the host cell. This has enabled cures for over 90% of children that have the severe combined immunodeficiency disease (SCID).

14. Nanomedicine for Gene Therapy
There are some potential drawbacks with using the a virus as a carrier for the new DNA.
The main issue is that since it is a virus, the body could see it as a foreign object and attack it.
Another issue is that the body could get infected with the virus.
The topic that has been up and coming in the world of gene therapy is the idea of using nanoparticles as carriers.
The nanoparticles that are used are typically smaller than the cells that are found in our bodies. This allows them to potentially get into a cell in order to change genetic information with the help of the gene therapy.
Gene therapy can utilize the nanoparticles to insert the DNA into the cell and help treat the disease.

15. Nanomedicine for Gene Therapy (continued)
Since there are some problems associated with viruses, research has taken a turn to try replicate the natural process that viruses use.
The three main characteristics of a virus that have to be replicated is its ability to (1) hold DNA, (2) make it through the cell’s endosomal process, and most importantly, (3) place DNA inside of the nucleus.
A behavior that we want to modify is the virus’ ability to replicate and stay inside the body. The idea is whatever we put into the body, we want to be able to exit without harm to the subject.

16. Nanomedicine for Gene Therapy Mimick a Virus
A method for mimicking a virus is by just encapsulating DNA into a nanoparticle itself.
This allows direct DNA interaction if the nanocapsule gets through the endosomal process.
To protect that nanocapsule from this process, we coat it with the same type of protective layering composed of endosome-lytic components, such as lytic peptides and lytic lipids that a virus may use.
The last hurdle to overcome is the DNA interaction with the nucleus. This can be done by presenting the DNA capsule in a fashion that is acceptable to the nucleus.
By layering the DNA capsule in the endosome-lytic components, it can make it through the endosome and be presented in a correct fashion for possible nucleic interaction.

17. Nanomedicine for Gene Therapy Mimick a Virus (continued)
Another possible way of mimicking the virus is by use of dendrimers discussed in Chapter 1.
Dendrimers are compounds that are made up of branches around an inner core, where they serve as a net-like material to hold the DNA.
This is achieved by the electrostatic interaction between the negativity-charged DNA and positive charge of the dendrimer’s core.
This method uses the same technique to get into the cell and escape from the protective endosomal process as the nanocapsules discussed above.
Unlike the nanocapsule technique, the dendrimers method is heavily dependent on the electrostatic interaction between the particle and the DNA.

18. Nanomedicine for Gene Therapy Mimic a Virus (continued)
One way of targeting is to use a magnetic field to guide the magnetic nanoparticles into a targeted area.
The same magnetic field would also be used to heat the nanoparticle so that it could release its DNA where needed.
Gene therapy has already enjoyed some success in the medical world.
It has led to an increase in blood clotting in patients who have hemophilia.
It has also led to an increase in muscle control in patients who have Parkinson’s disease, and of course it has been linked to regression of cancer.
It could cure diseases that are hereditary and reverse the mutations that cause unhealthy situations in the body such as cancer.

19. Conclusions
Nanomedicine and gene therapy could open the door to many possibilities in the medical world.
By combining these two fields, researchers should be able to create new methods that are safer for patients and can lead to saving millions of lives.
Nanomedicine and gene therapy are vital to the understanding of how our body works at the cellular level.
These fields offer researchers insight into how we can help the body in a more safe and efficient way.