Susumu Oda

Interleukin‐4 induces proliferation of adult T‐cell leukemia cells

Abstract: To evaluate the effect of IL‐4 on the growth of leukemic cells from adult T‐cell leukemia (ATL) patients (ATL cells) and determine whether the IL‐4 autocrine mechanism is involved in the growth of ATL cells, we studied the proliferative response of ATL cells, from 11 patients, cultured in the presence or absence of IL‐4 in vitro. Leukemic cells from 10 of the 11 patients examined proliferated in response to both IL‐2 and IL‐4 in a dose‐dependent manner. The proliferative response to IL‐4 was higher than that obtained with IL‐2 in 8 patients. The expression of the IL‐2 receptor (IL‐2R) αα‐chain in leukemic cells from some patients was also enhanced by IL‐4. The IL‐4 receptor was demonstrated by flow cytometry on the surface of ATL cells. Neither IL‐4‐induced proliferation of ATL cells nor IL‐4‐induced IL‐2R expression on ATL cells was inhibited by anti‐Tac or anti‐IL‐2 antibody and, therefore, these effects of IL‐4 are considered independent of endogenous IL‐2 activity. However, IL‐2 and IL‐4 were undetectable in the culture supernatants of ATL cells from any patient by enzyme‐linked immunosorbent assay. Interferon‐γ (IFN‐γ) partially inhibited IL‐2‐ or IL‐4‐induced proliferation of ATL cells. These results suggest that leukemic cells from ATL patients proliferate by an IL‐2 or IL‐4 paracrine mechanism in lymphoid tissue in vivo and that IFN‐γ inhibits IL‐2‐ or IL‐4‐induced proliferation of ATL cells.

ADULT T-CELL LEUKEMIA COMPLICATED BY HYPERCALCEMIA

Three autopsy cases of Adult T‐cell leukemia (ATL) complicated by a severe hypercalcemia are presented. In two of them, the hypercalcemia itself was the direct cause of death. There was no evidence of an increase of serum PTH in all three cases. Prostaglandins were within normal range in two of them. By a bioassay, a bone‐resorbing factor, osteoclast activating factor (OAF)‐like substance, was demonstrated in the culture medium of leukemic cells from one patient. Also, various degrees of osteoclastic activation were found in the bones of all three patients by the postmortem examination. It may be that the hypercalcemia occurring in cases of ATL is partly caused by the humoral factor, which is released from leukemic cells and activates a bone resorption by osteoclasts. Similar cases in which a significant activation of osteoclasts was practically demonstrated by histopathologic examination in addition to the detection of a bone‐resorbing factor have been rarely reported. ACTA PATHOL. JPN. 35 : 437–448, 1985.

Enhancing Effect of Interleukin‐2 on Production of Parathyroid Hormone‐related Protein by Adult T‐Cell Leukemia Cells

Leukemic cells from patients with adult T‐cell leukemia (ATL) can produce a calcium‐regulating protein, parathyroid hormone‐related protein (PTHrP). Moreover, it has been reported that ATL cells produce some cytokines besides PTHrP and that these cells respond to the T‐cell growth factors, interleukin‐2 (IL‐2) and interIenkin‐4 (IL‐4). To elucidate whether PTHrP produced by ATL cells is regulated by IL‐2 or IL‐4, we investigated the in vitro effects of IL‐2 and IL‐4 on the release of PTHrP. IL‐2 increased the release of PTHrP into the conditioned medium from leukemic cells in some, but not all, ATL patients; however, IL‐4 did not affect the PTHrP release. PTHrP messenger RNA (mRNA) levels were increased in ATL cells cultured in the presence of IL‐2. These data suggest that IL‐2 plays a role in the regulation of hypercalcemia by enhancing the production of PTHrP in ATL patients.

A CLINICOPATHOLOGICAL REVIEW OF 12 AUTOPSIED CASES OF ADULT T-CELL LEUKEMIA

Twelve autopsied cases with adult T‐cell leukemia (ATL) were reviewed clinicopathologically. The prognosis of three cases who had suffered from severe cutaneous lesions was much better than that of the other nine cases with no or negligible cutaneous lesions. The surface marker of leukemic cells from six cases was ordinary inducer/helper phenotype (OKT4+ and 8‐), but in one case leukemic cells showed OKT4+ and 8+. In another case, a significant amount of leukemic cell infiltration was found in the thymic cortex. Calcium content in the bone of ATL cases was lower than that of the patients without ATL (control group), and six cases with ATL (50%) were complicated by severe hypercalcemia. Neither adenoma nor hyperplasia of the parathyroid glands was found in any case. In most severely hypercalcemic patients, bone trabeculae were actively absorbed by numerous osteoclasts and partly replaced by fibrous tissues. In two normocalcemic patients, skeletal calcium content was also markedly reduced by osteoporosis, but the activation of osteoclasts was inconspicuous. It was speculated that the manner of bone resorption in ATL cases was diverse and there were some clinicopathological subtypes in ATL from the viewpoints of cutaneous lesions, hypercalcemia, and bone lesions.

LACK OF INTERLEUKIN-4 MRNA EXPRESSION IN ADULT T-CELL LEUKEMIA CELLS

To the Editor: Human T-cell leukemia virus type I (HTLV-I) has been identified as the infectious agent responsible for adult T-cell leukemia (ATL) (1). HTLV-I genome encodes a protein, Tax, that transactivates viral long terminal repeat-directed transcription and a variety of cellular genes such as interleukin (1L)-2 and IL-2 receptor ct chain (2, 3), and granulocyte-macrophage colony-stimulating factor, IL-3 and IL-4 (4). We have previously reported that leukemic cells from some ATL patients proliferated in response to exogenous IL-4 and constitutively expressed IL-4 receptors (5 , 6). Therefore, it may be possible that tax gene is involved in the activation of IL-4 gene in the leukemic cells from ATL patients, and that an IL4/IL-4 receptor autocrine mechanism works in the proliferation of ATL cells. We also reported that IL-4 was not detected in the culture supernatants of ATL cells by enzyme-linked immunosorbent assay (5 ) . However, the question arises as to whether ATL cells produce small but sufficient quantities of IL-4 for growth that are undetectable by conventional assay procedures. Moreover, it is possible that these ATL cells produce IL-4 that is not secreted and that would not be detected in extracellular medium. A more direct answer to this question could be obtained from a study of IL-4 mRNA assayed by a highly sensitive, yet specific reverse transcriptionpolymerase chain reaction (RT-PCR) technique for amplification of minute quantities of cellular mRNA. Eleven patients with ATL were studied. One patient (patient 10) was in chronic type, and the others were in acute type. The mononuclear cells were separated from blood of 10 ATL patients and a lymph node of 1 ATL patient (patient 11) by centrifugation on LSM solution (Litton Bionetics, Kensington, MD). CD4-positive (ATL) cells were more than 90 % of the mononuclear cells of samples, as evaluated by flow cytofluorometry. Total RNA was isolated as previously described by using the single-step isolation procedure (7). We have analyzed tax and IL-4 mRNA by complementary DNA

Unusual bone scintigraphy in chronic myelogenous leukemia — report of a case showing extensive uptake defect

An extensive 99mTc-methylene diphosphonate uptake defect was observed on bone scintigraphy in a 35-year-old male with chronic myelogenous leukemia. This type of bone scintigraphy pattern is quite unusual in leukemic patients and we speculate that acute disturbance of blood supply to the bone marrow was probably the cause.