造血因子と臨床応用

Clinical applications of hematopoietic growth factors

　造血に関与するサイトカインのうち，造血を正に制御するものは一般的に造血因子と呼ばれ，20数種類が知られている．造血因子は造血幹細胞の分化決定には作用せず，対応する受容体を発現している細胞の増殖因子として働き，分化がもたらされると考えられる．造血因子の臨床治験が数多く行われたが，医薬品として臨床応用されるようになったものはG-CSF，エリスロポエチンなどごく一部にとどまっている．トロンボポエチン(TPO)に代わり，TPO受容体作動薬の開発が進んでいる．

Hematopoietic growth factors are well known to be involved in the regulation of the intricate balance of growth and differentiation of a variety of hematopoietic cells. Late-acting factors such as granulocyte colony stimulating factor(G-CSF)and erythropoietin(EPO)stimulate proliferation of committed progenitors which express corresponding receptors, lead to further differentiation, eventually giving rise to mature cell elements with distinct functions. G-CSF and EPO have beneficial effects in the various clinical setting. The use of other hematopoietic factors is far from established and warrants further careful evaluation. The most promising agents seem to be thrombopoietin receptor(c-Mpl)agonist, which might have the potential to bind c-Mpl and stimulate the proliferation of megakaryocytes and production of platelets.