T-cell lymphomas and leukemias are blood cancers that can affect people of all ages, and though many of them are rare, they can be aggressive. Recent therapeutic advances such as immunotherapy have helped improve the prognosis for patients with these tough-to-treat cancers—but early diagnosis is key to treatment success.
The need for better understanding and treatment continues to grow. The Leukemia & Lymphoma Society estimates that every three minutes, someone is diagnosed with leukemia, lymphoma, or myeloma in the United States alone.
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The challenge is that there are multiple subtypes of T-cell neoplasms, and in any given sample, the malignant T-cells may be scarce. Identifying them with traditional laboratory technologies such as flow cytometry is difficult because of the close resemblance between abnormal and normal T-cells.
Recent advances in flow cytometry and molecular biology are helping improve the detection of T-cell cancers. Emerging technology is easing the task of finding and characterizing clonal expansion—a sure sign of malignancy in cell populations. These tools incorporate new advances that promise to improve the detection and characterization of malignant T-cells, including those that are dimly expressed.
Improving on T-cell receptor profiling
T-cell neoplasm analysis has traditionally been cumbersome due to the complex phenotypes of T-cell malignancies. Abnormalities in T-cells can be very subtle and require the assessment of a large selection of different markers.
T-cell receptor (TCR) profiling is one of the most robust ways to monitor T-cell clonal expansion. But traditional laboratory methods for profiling TCR require monitoring proteins or RNA levels associated with dozens of variables. Flow cytometry kits cover only 70 percent of these variables, while molecular biology methods, such as polymerase chain reaction (PCR), are costly and time consuming, and they require expertise that’s not available in many laboratories.
The recent introduction of conjugated antibodies has greatly improved the analysis of T-cell cancers. In 2019, the development of a flow cytometry assay using an anti-TRBC1 conjugated antibody marked a significant milestone in T-cell neoplasm assessment. Normal peripheral blood contains a mix of TRBC1-positive and TRBC1-negative cells on the surface of all mature TCRαβ T-cells, while T-cell neoplasms are clearly distinguished by their restricted, or “monotypic” TRBC1 expression, meaning they only contain one of the two types of TRBC1 cells. The assay was designed to detect T-cell clonality based on the presence of either TRBC1-positive or TRBC1-negative cells.
The new assay’s findings correlated with T-cell clonality testing by molecular biology. The flow cytometric assay is now used in research settings to test clonality in T-cell malignancies such as mature peripheral T-cell lymphomas, Sezary syndrome, and T-cell large granular lymphocytic leukemia. Because this method provides information that could aid in diagnoses, its implementation in routine use is being considered by research laboratories and clinical facilities.
The future of T-cell cancer diagnosis
Despite its undeniable utility, TRBC1-based flow cytometry assays leave room for improvement. Using TRBC1 alone to assess T-cell clonality could produce ambiguous results in cases with dim TRBC1 expression or TRBC1 negativity.
The recent development of an anti-TRBC2 conjugated antibody can help improve detection accuracy when the T-cell population of interest is TRBC1-negative or dimly expressed. That’s because using both anti-TRBC1 and TRBC2 antibodies together helps identify TRBC1-positive or TRBC2-positive cells simultaneously, more clearly indicating the presence or absence of a clonal expansion.
In a study of various specimens with T-cell neoplasia, a flow cytometry assay employing both TRBC1 and TRBC2 conjugated antibodies showed that all were either positive for TRBC1 clonality, orTRBC2 clonality. When the same assay was run on normal T-cells, both TRBC1-positive and TRBC2-positive cells were identified, as expected. The anti-TRBC2-conjugated antibody is currently available for research use only.
Integrating both types of TCR antibodies to T-cell neoplasm assessment will greatly improve confidence in the clinical diagnosis of hematological malignancies. This will help ensure that more patients are diagnosed in the early stages of their disease, when it’s so essential for oncologists to determine the ideal treatment path.
Faster, more accurate diagnoses—this is the holy grail of oncologists and the patients they serve. Technology advances are moving us closer to realizing that potential.
