Serum levels and differential expression of CD44 in childhood leukemia and malignant lymphoma: correlation with prognostic criteria and survival

Cell-adhesion molecules and their soluble forms: Promising predictors of "tumor progression" and relapse in leukemia

Some surface markers are used to discriminate certain leukemic subpopulations that retain a greater oncogenic potential than others, and, for this reason, they were termed as leukemic stem cells, similar to the concept of cancer stem cells in carcinoma. Among these surface markers are proteins involved in cell-cell adhesion or cell-matrix adhesion, and they may play a role in the relapse of leukemia, similar to metastasis in carcinomas. The most important are epithelial cadherin, neural cadherin, epithelial cell-adhesion molecule, and CD44, which can be cleaved and released, and their soluble forms were found increased in serum levels of cancer patients, being implicated, in some cases, with progression, metastases, and relapse. In this review, we highlighted the role of these four adhesion molecules in carcinomas and hematological malignancies, mainly leukemia, and discuss if the serum levels of soluble forms can be correlated with the surface protein status on the leukemic cells. Accession of the soluble forms looks attractive, but their use as markers in cancer must be studied in association with other parameters, as there are significant changes in levels in other pathological conditions besides cancer. Studies correlating the levels of the forms with the status of the membrane-bound proteins in leukemic (stem) cells and correlating those parameters with relapse in leukemia may afford important knowledge and applicability of those serum markers in clinical practice. For instance, the expression of the membrane-bound forms of these adhesion proteins may have promising clinical use in leukemia and other hematological malignancies.

CD44 is a RAS/STAT5-regulated invasion receptor that triggers disease expansion in advanced mastocytosis

The Hermes receptor CD44 is a multifunctional adhesion molecule that plays an essential role in the homing and invasion of neoplastic stem cells in various myeloid malignancies. Although mast cells (MCs) reportedly express CD44, little is known about the regulation and function of this receptor in neoplastic cells in systemic mastocytosis (SM). We found that clonal CD34⁺/CD38^- stem cells, CD34⁺/CD38⁺ progenitor cells, and CD117⁺⁺/CD34^- MCs invariably express CD44 in patients with indolent SM (ISM), SM with an associated hematologic neoplasm, aggressive SM, and MC leukemia (MCL). In addition, all human MCL-like cell lines examined (HMC-1, ROSA, and MCPV-1) displayed cytoplasmic and cell-surface CD44. We also found that expression of CD44 in neoplastic MCs depends on RAS-MEK and STAT5 signaling and increases with the aggressiveness of SM. Correspondingly, higher levels of soluble CD44 were measured in the sera of patients with advanced SM compared with ISM or cutaneous mastocytosis and were found to correlate with overall and progression-free survival. To investigate the functional role of CD44, a xenotransplantation model was employed using severe combined immunodeficient (SCID) mice, HMC-1.2 cells, and a short hairpin RNA (shRNA) against CD44. In this model, the shRNA-mediated knockdown of CD44 resulted in reduced MC expansion and tumor formation and prolonged survival in SCID mice compared with HMC-1.2 cells transduced with control shRNA. Together, our data show that CD44 is a RAS-MEK/STAT5-driven MC invasion receptor that correlates with the aggressiveness of SM. Whether CD44 can serve as therapeutic target in advanced SM remains to be determined in forthcoming studies.

T cell acute lymphoblastic leukemia (T-ALL): New insights into the cellular origins and infiltration mechanisms common and unique among hematologic malignancies

T-cell acute lymphoblastic leukemia (T-ALL) accounts for 15% and 25% of total childhood and adult ALL cases, respectively. During T-ALL, patients are at risk of organ infiltration by leukemic T-cells. Infiltration is a major consequence of disease relapse and correlates with poor prognosis. Transendothelial migration of leukemic cells is required to exit the blood stream into target organs. While mechanisms of normal T-cell transmigration are well known, the mechanisms of leukemic T-cell extravasation remain elusive; but involvement of chemokines, integrins and Notch signaling play critical roles. Here, we summarize current knowledge about molecular mechanisms of leukemic T-cell infiltration with special emphasis on the newly identified subtype early T-cell-progenitor (ETP)-ALL. Furthermore, we compare the extravasation potential of T-ALL cells with that of other hematologic malignancies such as B-ALL and acute myeloid leukemia (AML).

Pediatric Hodgkin lymphoma: biomarkers, drugs, and clinical trials for translational science and medicine

Hodgkin lymphoma (HL) is a lymphoid malignancy that is typically derived from germinal-center B cells. EBV infection, mutations in NF-κB pathway genes, and genetic susceptibility are known risk factors for developing HL. CD30 and NF-κB have been identified as potential biomarkers in pediatric HL patients, and these molecules may represent therapeutic targets. Although current risk adapted and response based treatment approaches yield overall survival rates of >95%, treatment of relapse or refractory patients remains challenging. Targeted HL therapy with the antibody-drug conjugate Brentuximab vedotin (Bv) has proven to be superior to conventional salvage chemotherapy and clinical trials are being conducted to incorporate Bv into frontline therapy that substitutes Bv for alkylating agents to minimize secondary malignancies. The appearance of secondary malignancies has been a concern in pediatric HL, as these patients are at highest risk among all childhood cancer survivors. The risk of developing secondary leukemia following childhood HL treatment is 10.4 to 174.8 times greater than the risk in the general pediatric population and the prognosis is significantly poorer than the other hematological malignancies with a mortality rate of nearly 100%. Therefore, identifying clinically valuable biomarkers is of utmost importance to stratify and select patients who may or may not need intensive regimens to maintain optimal balance between maximal survival rates and averting late effects. Here we discuss epidemiology, risk factors, staging, molecular and genetic prognostic biomarkers, treatment for low and high-risk patients, and the late occurrence of secondary malignancies in pediatric HL.

Soluble CD44 and CD44v6 and prognosis in children with B-cell acute lymphoblastic leukemia

AIM

CD44v6 is an isoform of CD44 that can be present in soluble form (sCD44v6). The aim of this study is to evaluate the presence of soluble CD44 (sCD44) and sCD44v6 in serum of children with B-cell precursor acute lymphoblastic leukemia (B-ALL) and their relationship with prognosis.

METHODS

sCD44v6 and sCD44 levels were measured in the sera of patients and healthy children by enzyme-linked immunosorbent assay. The level of the molecules was analyzed in relation to laboratory and clinical characteristics of the patients at presentation and response to therapy.

RESULT

sCD44v6 was significantly lower in patients (103.4 ± 44 ng/mL) than in controls (173.5 ± 73.6 ng/mL) whereas the serum level of sCD44 showed no significant difference between the groups. In patients, sCD44v6 quantity was inversely correlated with sCD44 level (r = -0.57, P < 0.01). The mean serum level of sCD44 in patients with >20% positivity for CD44 surface expression was greater than that in patients with ≤20% positivity (1345 ± 409 ng/mL vs 1111 ± 390 ng/mL, P = 0.05). sCD44v6 showed no significant association with response to therapy and prognostic factors except the TEL/AML1 positivity, as it was higher in TEL/AML1 positive patients (157.3 ± 55.6 ng/mL) than negative ones (92 ± 43.6 ng/mL, P = 0.036). Conversely, sCD44 was lower in TEL/AML1 positive patients and showed a significant association with white blood cell number, blast percentage and extramedullary involvement.

CONCLUSION

The lower level of sCD44v6 in patients than in controls suggests the possible diagnostic value of this molecule for B-ALL. The presence of an association with established prognostic factors despite of no relationship with disease outcome suggested these molecules for more studies in larger patient cohorts.

Biomarkers in childhood non-Hodgkin's lymphomas

Pediatric non-Hodgkin's lymphomas (NHLs) are a heterogeneous group of malignancies with distinct clinical, pathological, immunological and genetic characteristics. More than 90% of pediatric NHLs belong to one of three major histological subtypes: mature B-cell neoplasms, lymphoblastic lymphomas and anaplastic large-cell lymphomas. The recognition that different subtypes require different treatment regimens resulted in therapeutic strategies leading to over 80% of patients being cured. On the other hand, patients with resistant or relapsed disease have a poor prognosis. Prognostic biomarkers have not yet been identified for all pediatric NHLs and, although some are very important for diagnosis and prognosis, others may be of questionable value. Discovery of new biomarkers suitable for clinical application may aid the diagnosis and classification of lymphomas, which should, in turn, lead to better patient stratification. Consequent development of new treatment and follow-up approaches should lead to more efficient and less toxic treatment in children with NHL.

CD44 and CD27 expression pattern in B cell precursor acute lymphoblastic leukemia and its clinical significance

The expression of CD44 and CD27 molecules correlates with the differentiation stage of B cell precursors. The present study was designed to investigate the prognostic relevance of CD44 and CD27 molecules in patients with B cell acute lymphoblastic leukemia (ALL). CD27 and CD44 expression was determined in 58 patients by flow cytometry and their relation to established prognostic factors and response to therapy was investigated. Four patterns of expression were found; CD27 single positive (SP) in 20.7 % of patients, CD44SP in 25.8 %, CD27CD44 double positive (DP) in 20.7 %, and CD27CD44 double negative (DN) in 32.8 %. CD27 expression and the CD27SP pattern correlated directly with TEL/AML1 genotype (P = 0.012). Conversely, CD44 expression and the CD44SP pattern correlated inversely with this genotype (P = 0.016). Patients with the DP pattern had a lower WBC count (P = 0.03), lower percentage of blasts in their bone marrow (P = 0.028), and higher platelet count, whereas CD44SP patients had a higher WBC count and higher percentage of bone marrow blasts. Moreover, a negative association between DN pattern and complete remission (CR) rate was detected (P = 0.03). Mean CD27 expression was significantly higher in low-risk group and in patients who achieved CR (P = 0.001), and in those with a higher platelet number (P = 0.046) and less extramedullary involvement (P = 0.008). Although survival and CR duration were longer in patients with DP pattern and shorter in those with DN pattern, the result did not reach statistical significance. The expression of CD27 together with CD44 showed a relationship with several established risk factors as well as response to therapy, indicating the biological significance of these molecules in ALL.

Prognostic value of serum CD44, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 levels in patients with indolent non-Hodgkin lymphomas

Elevated serum CD44, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) have been linked to poor prognosis in aggressive lymphomas, but their utility in low grade lymphomas remains undefined. We evaluated serum CD44, VCAM-1 and ICAM-1 levels in 100 patients with newly diagnosed indolent NHL. The median pre-treatment values of the markers were as follows: CD44 540 ng/mL (range 156-1201), ICAM-1 311 ng/mL (range 102-1222) and VCAM-1 1165 ng/mL (range 248-4779). On univariate analysis, elevated sCD44, sICAM-1 and sVCAM-1 were significantly associated with worse overall (OS) and progression-free survival (PFS). In a subset analysis of patients with stage IV disease, the effects of sCD44 and sICAM-1 on OS persisted (p<0.05), as did the effect of sCD44 on PFS (p<0.01). In a multivariate analysis that included conventional prognostic factors and the Follicular Lymphoma International Prognostic Index (FLIPI) model, sICAM-1 demonstrated prognostic value for OS and PFS. We conclude that serum CD44, ICAM-1 and VCAM-1 can potentially be prognostic in patients with indolent NHL. Though the FLIPI model remains the gold standard for prognosis, these quantitative serologic markers may be useful as adjunct tools in assessing disease risk.