Ichiro Miyoshi

A retrovirus (ATLV) was unequivocally demonstrated in human adult T-cell leukemia (ATL) cell lines by density (1.152-1.155 g/cm3) in a sucrose gradient, reverse transcriptase activity insensitive to actinomycin D, RNA labeled with [3H]uridine, and specific proteins with molecular weights of 11,000, 14,000, 17,000, 24,000, and 45,000. Furthermore, cDNA prepared by endogenous reaction with detergent-treated virions hybridized to 35S RNA containing poly(A), which was inducible by IdUrd treatment of a T-cell line derived from leukemic cells of the ATL, and the integrated form of ATLV proviral DNA was detected in T-cell lines derived from ATL. The ATLV proviral DNA was also detected in fresh peripheral lymphocytes from all five patients with ATL tested so far but not in those from healthy adults. On the other hand, ATLV protein of Mr 42,000 was found to be at least one of the ATL-associated antigen(s) that were previously detected in ATL-leukemic cells by all sera from patients with ATL. These findings on the close association of ATLV protein and proviral DNA with ATL are direct evidence for the possible involvement of the retrovirus ATLV in leukemogenesis of human ATL.

The subventricular zone (SVZ) of the adult brain contains neural stem cells that have the capacity to regenerate new neurons after various insults. Brain ischemia causes damage to brain tissue and induces neural regeneration together with angiogenesis. We previously reported that, after ischemic injury in mice, SVZ-derived neural progenitor cells (NPCs) migrate into the striatum, and these NPCs are frequently associated with blood vessels in the regenerating brain tissue. Here we studied the role of blood vessels during the neural regeneration in more detail. BrdU administration experiments revealed that newly generated NPCs were associated with both newly formed and pre-existing blood vessels in the ischemic striatum, suggesting that the angiogenic environment is not essential for the neuron-blood vessel interaction. To observe migrating NPCs and blood vessels simultaneously in damaged brain tissue, we performed live imaging of cultured brain slices after ischemic injury. In this system, we virally labeled SVZ-derived NPCs in Flk1-EGFP knock-in mice in which the blood vessels are labeled with EGFP. Our results provide direct evidence that SVZ-derived NPCs migrate along blood vessels from the SVZ toward the ischemic region of the striatum. The leading process of the migrating NPCs was closely associated with blood vessels, suggesting that this interaction provides directional guidance to the NPCs. These findings suggest that blood vessels play an important role as a scaffold for NPCs migration toward the damaged brain region.

Myeloid-derived suppressive cells (MDSC) have been reported to promote metastasis, but the loss of cancer-induced B cells/B regulatory cells (tBreg) can block metastasis despite MDSC expansion in cancer. Here, using multiple murine tumor models and human MDSC, we show that MDSC populations that expand in cancer have only partially primed regulatory function and limited prometastatic activity unless they are fully educated by tBregs. Cancer-induced tBregs directly activate the regulatory function of both the monocyte and granulocyte subpopulations of MDSC, relying, in part, on TgfβR1/TgfβR2 signaling. MDSC fully educated in this manner exhibit an increased production of reactive oxygen species and NO and more efficiently suppress CD4(+) and CD8(+) T cells, thereby promoting tumor growth and metastasis. Thus, loss of tBregs or TgfβR deficiency in MDSC is sufficient to disable their suppressive function and to block metastasis. Overall, our data indicate that cancer-induced B cells/B regulatory cells are important regulators of the immunosuppressive and prometastatic functions of MDSC.