Intensity of antigen expression reflects IGHV mutational status and Dohner-defined prognostic categories in chronic lymphocytic leukemia, monoclonal B-cell lymphocytosis, and small lymphocytic lymphoma

Abstract

We demonstrate the prognostic utility of antigen quantitation in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and monoclonal B-cell lymphocytosis (MBL). Median antibody-bound-per-cell (ABC) of CD20, CD22, CD25, CD19, and %CD38(+) was determined in CLL (185/208), SLL (8/208) and MBL (15/208) cases by flow cytometry, then compared to Dohner-classification, immunoglobulin status (mutated, IGHV-M; unmutated, IGHV-U), CLL-IPI risk and time to first treatment (TTFT). Trisomy 12 cases showed increased %CD38-expression (p = .0379). Higher %CD38 was observed in IGHV-U versus IGHV-M (p = .0003). CD20ABC was increased in IGHV-U versus IGHV-M (p = .006). Del13q cases demonstrated lower CD22ABC (p = .0198). Cases without cytogenetic abnormality exhibited higher CD19ABC (p = .0295) and CD22ABC (p = .0078). Del17p cases demonstrated lower CD25ABC (p = .0097). High and very-high CLL-IPI risk groups were associated with high CD38-expression (p = .02) and low CD25ABC (p = .0004). Shortened TTFT was associated with high CD38-expression (p < .0001). Interestingly, high CD25ABC trended toward shortened TTFT (p = .07). Quantitative antigen expression reflects CLL-IPI risk groups and Dohner-classification.

Trial registration: ClinicalTrials.gov NCT00001620.

Keywords: Flow cytometry; antibody binding capacity; antigen quantitation; chronic lymphocytic leukemia; mean fluorescence intensity; prognosis.

Figure 1:

Antibody binding capacity (ABC) of CLL, SLL, and MBL patient peripheral blood samples. Box and whiskers represent median, interquartile range (IQR), and 1.5x IQR, respectively. Comparisons between each group performed by Mann-Whitney test. A. CD20 ABC for CLL (11,085; n=184), SLL (19,142; n=180), MBL (16,535; n=14). B. CD22 ABC for CLL (2,195; n=180), SLL (3,521; n=8), MBL (3,533; n=14). C. CD25 ABC of CLL, SLL, and MBL patient peripheral blood samples. CLL (697; n=147), SLL (1,113; n=6), MBL (853; n=11). D. CD19 ABC of CLL, SLL, and MBL patient peripheral blood samples. CLL (8,854; n=78), SLL (11,871; n=3), MBL (9,649; n=4). E. % of CD38 positive expression in CLL, SLL, and MBL patient peripheral blood samples. CLL (2.4%, n=185), SLL (45%, n=8), MBL (6%, n=15).

Figure 2:

Dohner prognostic classification and quantitation of antigen expression. Antibody binding capacity (ABC) for (A) CD20, (B) CD22, (C) CD25, (D) CD19, and (E) percent of CD38 positive expression, grouped by FISH subtype as classified per the Dohner prognostic hierarchy. Box and whiskers represent median, interquartile range (IQR), and 1.5x IQR, respectively. Comparisons between each group versus all others performed by Mann-Whitney test.

Figure 3:

IGVH Mutational status and quantitation of antigen expression. Antibody binding capacity (ABC) for (A) CD20, (B) CD22, (C) CD25 ABC, (D) CD19 ABC and (E) percent of CD38 positive expression, grouped by IGVH mutation status (M=Mutated, U=Unmutated). Box and whiskers represent median, interquartile range (IQR), and 1.5x IQR, respectively. Comparisons between each group performed by Mann-Whitney test.

Figure 4:

Clinical significance of surface antigen expression. Time to first treatment (left) and CLL-International Prognostic Index (CLL-IPI) risk (right) for patients with expression of CD25 (A), CD38 (B), CD20 (C), and CD22 (D) below or equal to and above the median (Q2).