92
や，発現量は少なく，単にウイ．ルス遺伝子の量的なも
ののみが細胞DNAの調節機構の破綻に関係している
のではないと考えられる．
IC， D腫瘍は腫瘍組織内に2種類の内在性ウイルス
が活性化され多数存在す．るという特徴を有している
が，Ad12がこ．れらの活性化にどのように関与している
か，また〃多y6遺伝子との関連など，興味深い問題点が
残されている．
特別講演 遺伝子治療研．究の現状と展望：血友病モ
デル
．（Gene therapy for hemophilia B：Amodel for
gene transfer system requiripg systemic delivery of
recombinant gene products）
（Department of Human Genetics，
University of Michigan Medical Schoo1）
Koutoku Kurachi
Hemophilia B ．is an X−chromosome−linked
rΦcessive disease which results from a．de負ciency of
biologically・active factor IX in the systemic circula・
tion． Currently hemophilia is treated by frequent
plasma protein replacement therapies which expose
patients to risks of serious side．一effect§such as infec−
tions with blood三bome pathological viruses includ一
ing HIV−1 and hepatitis． We have recently demon−
strated that skeletal muscle cells．can e岱ciently
produce recombinant factor IX．勿碗フηas well as勿
卿。．When retrovirus−transduced skeletal myo−
blasts were implanted into muscles， they fuse
e缶ciently to the host myo且bers as well as among
．themselves， and． continue．垂窒盾р浮モ奄獅〟@recombinant
factor IX which are ef五ciently transported into the
systemic circulation． Importantly， genetically
modi丘ed myoblasts could be recovered from．the
muscle tissues even after 4 months of cell implanta−
tion， indicating that some im．planted myoblasts can
survive for a long period of time as viable myo−
blasts， presumably as satellite cells。 These observa−
tion p士ovide a strong rationale for using skeletal
muscle cells as an e缶cient drug delivery ve耳icle that
may be engineered to allow a long・term production
of rhFIX into the systemic circulation at a level h萱gh
enough to correct hemophilia． This g6ne transfer
approach． may also be adapted to many other dis−
orders of muscles as well as proteins．which require
as e缶cient transportation．into the systemic circula−
tion。
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