Myeloid Blasts: How Myelogenous Blast Cells Form
What are Myelogenous Blast Cells?
Blast cells are immature cells that develop into all kinds of specialized cells through cell division and maturation. While all cells start out as blasts, the presence of abnormal myelogenous blast cells or blasts that have not fully matured into their specialized cells can be an indicator of the presence of cancer or another disease.
Myeloid blasts are produced during the process of hematopoiesis, which is the production of blood cells in the bone marrow. Normally, myeloid blasts mature into healthy blood cells that help protect the body against infection and disease. However, in certain medical conditions, myeloid blasts may fail to mature properly or may multiply excessively, leading to an accumulation of AML blasts in the blood. This can lead to a condition known as myeloid leukemia or myelodysplastic syndrome.
Hematopoietic Stem Cells
Myeloid blasts are formed from hematopoietic stem cells, which are the immature cells found in bone marrow that form the various types of blood cells. As cells die off in the body, or become damaged, the hematopoietic stem cells mature and replace those cells. This is a process that occurs throughout a person’s entire life span.
The 2 main hematopoietic stem cells are:
A myeloid stem cell forms into a myeloid blast that eventually forms a red blood cell, platelet or several types of white blood cells: Neutrophils, Eosinophils, Basophils and Macrophages.
A lymphoid stem cell forms a lymphoid blast that eventually forms several other types of white blood cells.
The Production of Normal Blood Cells
In a healthy person, normal blood cells develop in the bone marrow. Hematopoietic stem cells are produced in the blood marrow and eventually develop into 3 blood cell types: white blood cells, red blood cells or platelets.
How quickly blood cells are produced is a function that is controlled by their body’s needs. Typically white blood cells, which help the body fight infection, may need replacing as quickly as a few hours or a few days. Platelets, which help control clotting, may need replacing about every 10 days. Red blood cells, which carry oxygen throughout the body, only need replacing about every 120 days.
AML and the Formation of Blasts
In a person with AML, the hematopoietic stem cells do not fully develop because of the cancer and are either destroyed by the body in the bone marrow or enter the bloodstream as immature cells and are destroyed shortly thereafter. Less than 5% of the cells in the bone marrow should be myeloid blasts in a healthy patient.
Anemia, fatigue, and other symptoms of AML begin to present when more than 20% of the bone marrow is made up of these immature cells. This is sometimes referred to as the blast stage of AML because the blasts make copies of themselves quickly. Patients with acute myeloid leukemia in blast phase often have a fever, an enlarged spleen, weight loss, and generally feel unwell.
Healthy hematopoietic stem cells can be used in the treatment of AML and other leukemias to replace or rebuild diseased cells. Stem cells can be found in umbilical cord blood and in the bone marrow, and in smaller numbers in the bloodstream. The pelvic area or hips are commonly used as the source of donor stem cells. This process is called a bone marrow transplant, and it is one of the most frequent treatments for AML.
Diagnosing Acute Myeloid Leukemia (AML)
Acute myeloid leukemia (AML) is a type of cancer that affects the bone marrow and blood cells. It is characterized by the uncontrolled proliferation of myeloid blasts. AML is also known as acute myelogenous leukemia, acute myeloblastic leukemia and acute nonlymphocytic leukemia.
The most common symptoms of AML a patient experiences are:
- Tiredness or a general feeling of being run-down.
- Lack of appetite or unexplained weight loss
- Feeling cold
- Bone/joint pain
When a patient experiences these common AML Symptoms, physicians may begin to look for blast cells to confirm the presence of acute myeloid leukemia. Myeloid blasts can be detected through a blood test or bone marrow biopsy.
Typically AML is diagnosed, in part, through a complete blood count (CBC). The patient with AML may show an abnormally high level of white blood cells, but upon closer examination the CBC shows that these cells are actually leukemia blasts that do not protect against infection.
When AML is suspected from the results of a complete blood count, bone marrow tests are usually given as a follow up. Bone marrow samples are obtained from the patient and analyzed for the presence of blasts as well.
The SIERRA Trial and AML Bone Marrow Transplant
The SIERRA clinical trial seeks to determine the effectiveness of the investigational drug Iomab-B, which may enable more transplants in patients aged 55 and older. Upon approval, Iomab-B is intended to prepare and condition patients for a bone marrow transplant, in a potentially safer and more efficacious manner than intensive chemotherapy conditioning that is the current standard of care in bone marrow transplant conditioning.
The SIERRA clinical trial may help improve the way AML is treated in the future.