Hadassah researchers have identified that the gene, which is involved in transporting proteins into the cell nucleus, is essential for the growth and function of acute myeloid leukemia cells. Silencing it also affected leukemic stem cells taken from patients, but the road to developing a cure is still long.
Researchers from Hadassah Medical Center identified a gene that is highly expressed in cells לוקמיה מיאלואידית חריפה And in leukemic stem cells, which are considered one of the sources of disease relapse. When they silenced the gene, IPO11, the cells ceasedLeukemia to grow in culture and their ability to take root in the bone marrow of mice and create leukemia in them was impaired.
The findings point to IPO11 as a potential new target for treatment, but this is in the early stages of research. Researchers have not yet developed a drug that inhibits the gene or the protein it encodes, and the approach has not yet been tested in humans.
A rapidly developing disease
Acute myeloid leukemia, AML, is a malignant disease of the blood cells and bone marrow. It develops following the accumulation of genetic changes in stem cells or young cells of the myeloid lineage.
Normally, these cells mature into different types of blood cells. In AML, they remain young, divide uncontrollably, and accumulate in the bone marrow and blood.
The accumulation of leukemia cells crowd out normal blood cells and impair their production. The decrease in the number of red blood cells can cause anemia and fatigue, the damage to normal white blood cells increases the risk of infections, and the lack of platelets can cause bleeding and bruising.
Sometimes, malignant cells can also accumulate in tissues outside the bone marrow and cause swelling, pain, or pressure on organs.
The disease usually progresses rapidly and requires diagnosis and treatment without delay.
Why does the disease recur?
AML is the most common acute leukemia in adults, and its incidence increases with age. Treatment is determined by the patient's age, health status, the type of mutations found in the cells, and other characteristics of the disease.
Treatment may include intensive chemotherapy, targeted drugs, lower-intensity therapies, and in suitable patients, a stem cell transplant from a donor.
In some patients, treatment is successful in bringing about remission, meaning a state in which leukemia can no longer be detected by conventional tests. However, in a significant proportion of patients, the disease recurs.
According to Dr. Boaz Nachmias, a senior physician in the hematology unit and director of the leukemia service at Hadassah, leukemic stem cells are considered one of the main causes of disease recurrence.
These cells are capable of replenishing the leukemia cell population. They may reside in relatively protected areas of the bone marrow, survive treatment, and later begin to divide again.
"Chemotherapy is successful in eliminating a large portion of the leukemia cells, but the leukemia stem cells may remain in the bone marrow and renew the disease," explains Dr. Nahmias.
How can leukemic stem cells be damaged and prevented from regenerating the disease?
The goal of the research, supported by a grant from the National Science Foundation, was to identify features that distinguish leukemic stem cells from other AML cells, and to find vulnerabilities that could be attacked in the future with drugs.
Large-scale CRISPR scanning
In the first stage, the researchers cultured lines of AML cells derived from patients.
Using technology Crisper The researchers performed a large-scale scan, in which thousands of genetic targets were silenced using a library that included tens of thousands of guide sequences.
They then monitored the cells and examined which silencing techniques prevented them from continuing to grow.
The scan revealed about 500 genes and genetic targets that appeared to be essential for the survival and proliferation of leukemia cells. When these genes were silenced, cell growth was impaired.
However, not every gene that is essential for a cancer cell is suitable for treatment. A gene that is equally essential for healthy cells may be a dangerous target. Therefore, researchers needed to identify targets that are of particular importance to leukemic cells, and especially leukemic stem cells.
Isolation of leukemic stem cells
In the next step, the researchers characterized the leukemic stem cells based on molecular markers and their ability to take root in the bone marrow of mice.
The ability to take root is considered a key test of the function of a leukemic stem cell: if the cell is taken up by the bone marrow and succeeds in producing a new population of leukemia cells, this indicates that it retains its ability to renew the disease.
After isolating the stem cells, the researchers performed RNA sequencing, a method that allows them to measure which genes are active in the cell and to what extent.
They compared the gene expression patterns in leukemic stem cells with those in other leukemia cells.
IPO11 was prominent in both cell types
In comparison, the researchers identified IPO11, a gene that was highly expressed in both leukemic stem cells and other AML cells.
The gene encodes a protein called Importin-11, which participates in the transfer of proteins from the cytoplasm into the cell nucleus.
The transfer of proteins to the nucleus is essential for many processes, including the control of gene expression, cell division, and response to external signals. According to the researchers, some of the proteins transferred by IPO11 are necessary for the activity and growth of leukemia cells.
IPO11 was a known gene, but its role in acute myeloid leukemia and leukemic stem cells was unknown until now.
When the researchers silenced IPO11 in AML cells, their ability to continue growing was impaired.
Testing on cells taken from patients
To test whether the result was limited to cell lines grown for a long time in the laboratory, the researchers also examined fresh samples of AML cells from patients.
The samples were taken from both newly diagnosed patients and patients whose disease had returned and become resistant or more difficult to treat.
In these cells too, silencing IPO11 led to a significant decrease in growth in culture.
The researchers also tested the cells' ability to take root in mice. AML cells in which IPO11 was not silenced engrafted into the bone marrow, proliferated, and formed leukemia.
In contrast, cells in which the gene was silenced were unable to take root to the same extent and did not produce the disease as usual.
"We showed that silencing IPO11 dramatically impairs the ability of leukemic stem cells to function," says Dr. Nahmias. "Thus, we identified a therapeutic target that was previously unknown in this context."
A treatment target, not a ready-made cure
Silencing a gene in cells in the laboratory is not equivalent to drug treatment in humans.
To turn the finding into a treatment, it will be necessary to develop a molecule, protein, antibody, or other method that will impair IPO11 activity to a sufficient extent and in a targeted manner.
One of the challenges will be to test how much healthy cells need IPO11. Too strong inhibition of the nuclear protein transport system could also affect healthy cells.
Researchers will need to identify the most important proteins that IPO11 transports in leukemia cells, and see if it is possible to target the pathway more selectively.
It will also be necessary to examine the safety of the delay in animals over time, its effect on the normal circulatory system, and its effectiveness in combination with existing treatments.
"We are now trying to develop a treatment that will inhibit IPO11," says Dr. Nahmias. "The road is still long, but the goal is clear: to damage the leukemic stem cells and reduce the risk of the disease returning."
The study does not at this stage offer a treatment for AML patients, but it does point to a possible weak point in the cells responsible for the disease's recurrence.
FAQ
What is acute myeloid leukemia?
This is a malignant disease in which young cells of the myeloid lineage divide uncontrollably and accumulate in the bone marrow and blood, crowding out normal blood cells.
What are leukemic stem cells?
These are cancer cells that have the ability to self-renew and produce new populations of leukemia cells. They may survive treatment and contribute to disease recurrence.
What is IPO11?
This is a gene that encodes the protein Importin-11, which participates in the transfer of proteins to the cell nucleus.
How did the researchers silence the gene?
The researchers used CRISPR technology to disrupt the expression or function of IPO11 in leukemia cells.
What happened after IPO11 was silenced?
AML cells stopped growing normally in culture, and leukemic stem cells largely lost their ability to take root in the bone marrow of mice and generate leukemia.
Is there already a drug that inhibits IPO11?
No. The researchers have identified a possible target and are now trying to develop a drug to inhibit it.
Has the treatment been tested on humans?
No. The experiments were conducted in cell cultures, patient samples, and mice.
More on the subject on the science website
- The mold that caused the curse of the pharaohs becomes a weapon against leukemia
- Another component in the mechanism that causes leukemia was discovered
- When mitochondrial DNA “directs” the immune system
- A fungus from NASA's clean rooms managed to survive conditions that simulate a journey to Mars
- When the cell's energy station goes wrong
