CD44 Expression and Soluble CD44 as a Potential Marker of Tumor Load in Pediatric Acute Leukemia

Background: CD44 standard transcript (CD44s) is known to be widely expressed on ANLL and in a high percentage of ALL where it is reported to correlate with tumor burden. Different isoforms have been reported to be expressed on ANLL and/or ALL with various impact on prognosis. In the present study the expression of CD44s and its variant isoforms CD44v4, v6 and v7/8 were analyzed in 76 newly diagnosed children with acute leukemia and correlated with immunophenotyping, TLC and tumor burden. Patients and Methods: The cases comprised 62 ALL and 14 ANLL cases, ALL cases included 42 males and 20 females with an age range of 1 to 17 years, a mean of 3.6 years and a median of 4 years. ANLL cases included 4 males and 10 females with an age range of 2 to 16 years, a mean of 9 years and a median of 9.5 years. Results: CD44s was detected on all ANLL and 98.3% (61/62) of ALL cases tested. CD44v4 was encountered, probably for the first time, in 7/52 ALL and 1/14 ANLL; no other variants were encountered. Serum CD44 (sCD44) level was elevated in 25/35 ALL and in 11/14 ANLL with no correlation to CD44s expression. Conclusion: CD44 variant isoform expression could be used as a marker for monitoring minimal residual disease (MRD) in positive cases. Serum CD44s levels can also be used as a tumor marker for follow up of patients and monitoring of therapy in ALL and ANLL cases independent of CD44 expression.