Plasma M-CSF as an indicator of response to chemotherapy in adult T cell leukemia patients

Impact of visceral involvements and blood cell count abnormalities on survival in adult T-cell leukemia/lymphoma (ATLL)

Multiple visceral involvements and various blood cell count abnormalities are frequently manifested in adult T-cell leukemia/lymphoma (ATLL) at diagnosis. We evaluated the effects of four visceral involvement (bone marrow (BM), skin, liver, spleen) and six blood cell count abnormalities (anemia, neutrophilia, thrombocytopenia, monocytosis, eosinophilia, basophilia) on the overall survival of 168 ATLL patients. In the aggressive type, BM involvement, skin involvement and monocytosis were significantly poor prognostic factors. Furthermore, concomitant involvement of BM and additional visceral organs worsened the prognosis. These data support that multiple organ involvements represent a poor prognostic factor for ATLL and provide clinical significance for BM examinations.

Clinical relevance of survivin as a biomarker in neoplasms, especially in adult T-cell leukemias and acute leukemias

Survivin has been identified as one of the top 4 transcripts among 3.5 million human transcriptomes uniformly up-regulated in cancer tissues but not in normal tissues. Therefore, we quantitatively determined the messenger RNA (mRNA) expression profile for survivin by a real-time reverse transcriptase-polymerase chain reaction (RT-PCR) technique in 113 patients with leukemias, such as adult T-cell leukemia (ATL), acute lymphoid leukemia (ALL), acute myeloid leukemia (AML), chronic myeloid leukemia in crisis, and chronic lymphocytic leukemia (CLL), and in 25 cell lines, including 7 ATL cell lines and 15 solid-tumor cell lines. Furthermore, we examined whether the plasma level of survivin protein as measured by enzyme-linked immunosorbent assay (ELISA) substituted for mRNA expression by PCR quantification. Gene expression was quantitatively confirmed to be up-regulated in approximately 90% of ATL and acute leukemia cases and in all of the cell lines tested, whereas it was down-regulated in almost all cases of CLL. Furthermore, with respect to the interpretation of the gene expression findings, attention was paid to standardization with a housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), in the real-time PCR quantification, because the variability in GAPDH expression among the different cell types was significant. GAPDH expression was relatively low in ATL cells and high in ALL and AML cells. The rates of increase in the levels of survivin protein in the plasma of ATL patients and in the supernatants from in vitro cultures of solid-tumor cell lines were low compared with rates of increase of the mRNA and protein level in the cells, suggesting that the protein levels in plasma do not always reflect survivin expression in tumor cells. Our findings indicate the potential clinical relevance of survivin quantified by real-time PCR but not for the protein level in plasma as determined by ELISA, especially in cases of ATL and acute leukemias.

Mechanism of hypercalcemia in adult T-cell leukemia: overexpression of receptor activator of nuclear factor kappaB ligand on adult T-cell leukemia cells

Hypercalcemia is one of the most frequent and serious complications in patients with adult T-cell leukemia (ATL) and is due to marked bone resorption by accumulation of osteoclasts (OCLs). Although several cytokines such as interleukin 1 and parathyroid hormone-related protein are thought to be involved in the development of high serum Ca(++) levels, its precise underlying mechanism remains unknown. This study analyzed the expression of various genes that are thought to regulate serum Ca(++) levels in ATL and showed that the overexpression of the receptor activator of nuclear factor kappaB (RANK) ligand gene correlated with hypercalcemia. ATL cells from patients with hypercalcemia, which highly expressed the transcripts of the RANK ligand (RANKL) gene, induced the differentiation of human hematopoietic precursor cells (HPCs) into OCLs in vitro in the presence of macrophage colony-stimulating factor (M-CSF). In contrast, ATL cells from patients without hypercalcemia did not induce such differentiation, suggesting that the induction of the differentiation correlated with the expression of the RANKL gene in ATL cells. Cell differentiation was suppressed by osteoprotegerin/Fc, an inhibitor of RANKL, indicating that such differentiation occurred through the RANK-RANKL pathway. In addition, direct contact between ATL cells and HPCs was essential for the differentiation, suggesting that not the soluble form but membrane-bound RANKL played a role in this process. These results strongly suggested that ATL cells induce the differentiation of HPCs to OCLs through RANKL expressed on their surface, in cooperation with M-CSF, and ultimately cause hypercalcemia.

Pathological roles of interleukin-15 in adult T-cell leukemia

Interleukin-15 (IL-15) is a 14-kDa glycoprotein belonging to the same four helix bundle-cytokine family as IL-2. Although the biological activity of IL-15 in vitro has been studied extensively, its physiological role is still obscure. The receptors for IL-15 and IL-2 consist of three subunits, an unique alpha chain and shared beta and gamma chains. Since beta and gamma chains transduce the signals from the receptors, both cytokines share similar biologic functions, although IL-15 and IL-2 do not have sequence homology. The alpha chains function to increase binding affinity for each cytokines. Adult T-cell leukemia (ATL) cells constitutively express the IL-2 receptor (IL-2R) alpha and expression is believed to be essential in the early stages of disease development. We have recently shown that ATL cells also express the complete form of IL-15R including the alpha chain, and that ATL cells proliferate in response to exogenous IL-15. Since the mRNA of IL-15 is ubiquitous and is detected in many tissues and cells, it is possible that IL-15R stimulation is involved in the development and progression of ATL. Here, we review recent studies on IL-15 and IL-15R and their association with ATL and other lymphoproliferative disorders.