マウス骨髄性白血病細胞の増殖と分化に関する研究

京都大学0048新制・論文博士医学博士乙第2990号論医博第641号新制||医||212(附属図書館)4447UT51-61-I222(主査)教授 野島 徳吉, 教授 沼 正作, 教授 松本 清一学位規則第5条第2項該当Kyoto UniversityDA

Silencing of human T-cell leukemia virus type I gene transcription by epigenetic mechanisms

BACKGROUND: Human T-cell leukemia virus type I (HTLV-I) causes adult T-cell leukemia (ATL) after a long latent period. Among accessory genes encoded by HTLV-I, the tax gene is thought to play a central role in oncogenesis. However, Tax expression is disrupted by several mechanims including genetic changes of the tax gene, deletion/hypermethylation of 5'-LTR. To clarify the role of epigenetic changes, we analyzed DNA methylation and histone modification in the whole HTLV-I provirus genome. RESULTS: The gag, pol and env genes of HTLV-I provirus were more methylated than pX region, whereas methylation of 5'-LTR was variable and 3'-LTR was not methylated at all. In ATL cell lines, complete DNA methylation of 5'-LTR was associated with transcriptional silencing of viral genes. HTLV-I provirus was more methylated in primary ATL cells than in carrier state, indicating the association with disease progression. In seroconvertors, DNA methylation was already observed in internal sequences of provirus just after seroconversion. Taken together, it is speculated that DNA methylation first occurs in the gag, pol and env regions and then extends in the 5' and 3' directions in vivo, and when 5'-LTR becomes methylated, viral transcription is silenced. Analysis of histone modification in the HTLV-I provirus showed that the methylated provirus was associated with hypoacetylation. However, the tax gene transcript could not be detected in fresh ATL cells regardless of hyperacetylated histone H3 in 5'-LTR. The transcription rapidly recovered after in vitro culture in such ATL cells. CONCLUSION: These results showed that epigenetic changes of provirus facilitated ATL cells to evade host immune system by suppressing viral gene transcription. In addition, this study shows the presence of another reversible mechanism that suppresses the tax gene transcription without DNA methylation and hypoacetylated histone

IL-2/IL-2 Receptor Pathway Plays a Crucial Role in the Growth and Malignant Transformation of HTLV-1-Infected T Cells to Develop Adult T-Cell Leukemia

T cells infected with human T-cell leukemia virus type 1 (HTLV-1) transform into malignant/leukemic cells and develop adult T-cell leukemia (ATL) after a long latency period. The tax (transactivator from the X-gene region) and HBZ (HTLV-1 bZIP factor) genes of HTLV-1 play crucial roles in the development of ATL. The process and mechanism by which HTLV-1-infected T cells acquire malignancy and develop ATL remain to be elucidated. Constitutive expression of interleukin-2 (IL-2) receptor α-chain (IL-2Rα/CD25), induced by the tax and HBZ genes of HTLV-1, on ATL cells implicates the involvement of IL-2/IL-2R pathway in the growth and development of ATL cells in vivo. However, the leukemic cells in the majority of ATL patients appeared unresponsive to IL-2, raising controversies on the role of this pathway for the growth of ATL cells in vivo. Here, we report the establishment of 32 IL-2-dependent T-cell lines infected with HTLV-1 from 26 ATL patients, including eight leukemic cell lines derived from five ATL patients, while no T-cell lines were established without IL-2. We have shown that the IL-2-dependent ATL cell lines evolved into IL-2-independent/-unresponsive growth phase, resembling ATL cells in vivo. Moreover, the IL-2-dependent non-leukemic T-cell lines infected with HTLV-1 acquired IL-2-independency and turned into tumor-producing cancer cells as with the ATL cell lines. HTLV-1-infected T cells in vivo could survive and proliferate depending on IL-2 that was produced in vivo by the HTLV-1-infected T cells of ATL patients and patients with HTLV-1-associated diseases and, acts as a physiological molecule to regulate T-cell growth. These results suggest that ATL cells develop among the HTLV-1-infected T cells growing dependently on IL-2 and that most of the circulating ATL cells progressed to become less responsive to IL-2, acquiring the ability to proliferate without IL-2

重複腎盂尿管と尿管異所開口を伴った巨大水腎症の1例

33歳女.腹部膨隆を主訴とし, 腹部超音波検査, DIPと順行性腎盂造影, CT, MRI, 膀胱鏡検査等で, 両側重複腎盂尿管の右上半腎より発生した巨大水腎症と術前診断された.腰部斜切開で後腹膜腔に入ると右上半腎所属の尿管は明らかな腎盂尿管移行部狭窄を伴っており, これにより巨大水腎症が発生したと思われた.尿管異所開口の部位は断定できないが, すくなくとも外尿道括約筋群よりも遠位であると考えられた.巨大水腎とその所属尿管は一塊として摘出され, 巨大水腎の内容量は2, 640mlであった.術後1年目のDIPで良好な経過を取っているGiant hydronephrosis is an uncommon clinical entity. Even more uncommon is the association of giant hydronephrosis with a double collecting system and ectopic ureter. Here, we report a case of giant hydronephrosis of the bilateral duplex systems associated with ureteral ectopia. The patient underwent upper pole nephrectomy and upper ureterectomy. To our knowledge, only four similar cases have been reported previously

同一腎に腎細胞癌と腎血管筋脂肪腫を合併した1例

結節性硬化症の合併は認めない.腹部超音波検査にて, 右腎の中部外側に高エコーを呈する腫瘤を, 下極付近に前者よりも更に高エコーを呈する腫瘤と指摘され当科受診.CT, MRI, 血管造影にて, 右腎中部外側の腫瘤は腎細胞癌と術前診断された.1990年3月経腹膜的根治的右腎摘除術を施行, 中部外側の腫瘍は腎細胞癌, alveolar type, common type, clear cell subtype, G1と, 下極付近の腫瘍は腎血管筋脂肪腫と病理診断された.術後経過は良好で, 術後61ヵ月再発転移を認めないCoexistence of renal cell carcinoma and angiomyolipoma in the same kidney is rare. A 54-year-old woman without tuberous sclerosis was admitted for further examination of incidental renal masses on ultrasonography. Computerized tomography revealed a 17-mm high density mass in the mediolateral portion of the right kidney and a 5-mm low density mass near the right lower pole. Because the former mass showed a typical tumor pattern on selective renal angiography and the latter mass was strongly hyperechoic on ultrasonography, a clinical diagnosis of renal cell carcinoma and angiomyolipoma was made. A right radical nephrectomy confirmed the preoperative diagnosis. She has been followed for 61 months with no recurrence

Tax-Independent Constitutive IκB Kinase Activation in Adult T-Cell Leukemia Cells

Adult T-cell leukemia (ATL) is a fatal T-cell malignancy that arises long after infection with human T-cell leukemia virus type I (HTLV-I). We reported previously that nuclear factor-κB (NF-κB) was constitutively activated in ATL cells, although expression of the viral proteins was barely detectable, including Tax, which was known to persistently activate NF-κB. Here we demonstrate that ATL cells that do not express detectable Tax protein exhibit constitutive IκB kinase (IKK) activity. Transfection studies revealed that a dominant-negative form of IKK1, and not of IKK2 or NF-κB essential modulator (NEMO), suppressed constitutive NFκB activity in ATL cells. This IKK activity was accompanied by elevated expression of p52, suggesting that the recently described noncanonical pathway of NF-κB activation operates in ATL cells. We finally show that specific inhibition of NF-κB by a super-repressor form of IκBα (SR-IκBα) in HTLV-I-infected T cells results in cell death regardless of Tax expression, providing definitive evidence of an essential role for NF-κB in the survival of ATL cells. In conclusion, the IKK complex is constitutively activated in ATL cells through a cellular mechanism distinct from that of Tax-mediated IKK activation. Further elucidation of this cellular mechanism should contribute to establishing a rationale for treatment of ATL