Medical Health Encyclopedia

Important antigens associated with ALL include:

• CD10, more frequently referred to as cALLa (common ALL antigen). This antigen occurs in about half of all ALL cases and in about 80% of ALL B-precursor patients. It is associated with a good prognosis.
• CD95 (associated with a good prognosis)
• CR19
• DR

The surfaces of T-cell ALL cancer cells express several antigens as well. For example the presence one of these, CD2, suggests a favorable prognosis.

Testing for Genetic Abnormalities

Genetic tests are useful for a number of important criteria:

• Diagnosing a specific ALL subtype
• Designing appropriate treatment
• Deciding prognosis
• Monitoring patients throughout treatment and beyond

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Cytogenetics is a technique that researchers use to determine specific genetic abnormalities, which are found in nearly 65% of all leukemias. Detecting these genetic defects is helpful in making a full diagnosis of ALL and in planning the most appropriate therapy. Specific technologies called microarray chips are now capable of checking up to 48,000 different genes in a single experiment, which holds promise for assessing prognosis and developing very targeted therapies in the future. Research on DNA microarray analysis continues to reveal different prognostic subgroups of ALL. As the precision, logistics, and cost effectiveness of DNA microarray assays improve, they may be used more commonly in the clinical setting.

MTHFR Variants. Methylenetetrahydrofolate reductase (MTHFR) is an enzyme involved in folate metabolism, and variations in the MTHRF gene may also influence response to antifolate chemotherapy. A 2004 study showed that patients with one of two specific variations of the MTHFR gene had a lower probability of survival following treatment with methotrexate.

Translocations. Genetic translocations (swapping of genes on chromosomes) may affect outlook. Examples include the following:

• Patients with the t(12;21) genetic translocation (also referred to as TEL-AML1 fusion) have an excellent prognosis.
• Patients who carry the defective gene called ETV6 often respond well to chemotherapy.
• The t(4;11), sometimes referred to as MLL, is the most common translocation in children under one year. Unfortunately, it carries a poor outlook in anyone who carries it. A 2001 study suggested that this genetic variant may actually be a unique leukemia and require treatments that differ from standard ALL.
• The Philadelphia translocation also t(9;22) indicates a poor outlook. It represents about 20% of adult cases and only about 5% of childhood cases.
• The t(1;19) location occurs in about 5% of ALL childhood cases and requires aggressive treatment.