Cancer Gene Therapy

…Using Tumor Suppressor Genes.

Overview Gene Therapy p53 Using Gene Therapy to Treat Lung Cancer Problems

Gene Therapy

Vectors In Vivo vs. Ex Vivo Which cells are the target cells

What is Gene Therapy?

Gene therapy is a technique for introducing the genetic material of a gene in a patient that lacks that gene because of a mutation.

Vectors

The way you insert the “normal” gene in the patient’s cell is by vectors.

The most common vectors that are used in gene therapy are virus vectors

Why Viruses?

Viruses through the time of evolution have evolved to infect the cells with great specificity

Viruses tend to be very efficient at transfecting their own DNA into the host cell genome.

This allows them to produce new viral particles at the period of synthesis of the cell

Types Of Viruses…

Retrovirus Adinovirus Lentiviruses Poxviruses and Herpes Viruses

Adenovirus36 kb Double Stranded DNA Genome

Entry through CAR receptor and integrin co-receptor

E1A E3 E1B

E2A E4E2B

L1 L2 L4L3 L5

Latest Generation Adenoviral Vector

“Gutless”; Helper-dependent; Minimal Ad

Therapeutic Transgene Stuffer DNAStuffer DNA ITRITR

Which Virus to Use?

Depends how well they transfer the genes to cells which cells they can recognize and infect and whether they alter the cell’s DNA permanently

or temporarily

Cells removed from body

Transgene deliveredCells cultured

Cells returned to the body

Ex Vivo In VivoTransgene delivered

directly into host

Strategies for Transgene Delivery

Which cells are the target cells

Both Healthy and Cancerous cells can be a target Ex of targeting Healthy cells

One way is by replacing a missing or altered gene with a “normal” one

Cont: Which cells are the target cells Ex of targeting Cancer Cells

Scientists can target cancer cells with genes that can be used to destroy the cells. In this technique, cancer cells are introduced to what is called “suicide genes”

Naked DNANaked DNA Target Target CellCell

Therapeutic Therapeutic ProteinProtein

AAVAAV

Retrovirus/LentivirusRetrovirus/Lentivirus

AdenovirusAdenovirus

NucleusNucleus

Gene Therapy Principles

Adenovirus Cell Entry

p53 Pathway

Using Gene Therapy to Treat Lung Cancer In this clinical trial the scientist used gene

therapy in combination with radiation therapy so they can treat lung cancer in 19 different patients

Treatment: Gene therapy and Radiation. Intratumoral needle injections of Ad-p53

on days 1, 18 and 32 of the treatment. tumors ≥ 4 cm where injected with 10 ml tumors ‹ 4 cm were injected with 3 ml

Radiation therapy

Results

17/19 patients made it through the entire therapy

complete response in 2 patients (11%) partial response in 4 patients (21%) stable disease in 1 patient (5%) progressive disease in 11 patients (57%)

Results Not That Good

57% of the patients showed that the cancer progressed to worse stages

Why?

Major Problems that Scientists Must Overcome Identify more efficient ways to deliver the

genes to the patients’ genetic material Develop vectors that can specifically focus

on the targeted cells Ensure that vectors will successfully insert

the desired genes into each of these target cells

Cont: Major Problems that Scientists Must Overcome Deliver genes to a precise location in the

patient’s DNA Ensure that transplanted genes are

precisely controlled by the body’s normal physiologic signals