Acquired loss of p53 induces blastic transformation in p210(bcr/abl)-expressing hematopoietic cells: a transgenic study for blast crisis of human CML

Chronic myelogenous leukemia (CML) begins with an indolent chronic phase but inevitably progresses to a fatal blast crisis. Although the Philadelphia chromosome, which generates p210(bcr/abl), is a unique chromosomal abnormality in the chronic phase, additional chromosomal abnormalities are frequently detected in the blast crisis, suggesting that superimposed genetic events are responsible for disease progression. To investigate whether loss of p53 plays a role in the evolution of CML, we crossmated p210(bcr/abl)-transgenic (BCR/ABL(tg/-)) mice with p53-heterozygous (p53(+/-)) mice and generated p210(bcr/abl)-transgenic, p53-heterozygous (BCR/ABL(tg/-)p53(+/-)) mice, in which a somatic alteration in the residual normal p53 allele directly abrogates p53 function. The BCR/ABL(tg/-)p53(+/-) mice died in a short period compared with their wild-type (BCR/ABL(-/-)p53(+/+)), p53 heterozygous (BCR/ABL(-/-)p53(+/-)), and p210(bcr/abl) transgenic (BCR/ABL(tg/-)p53(+/+)) litter mates. They had rapid proliferation of blast cells, which was preceded by subclinical or clinical signs of a myeloproliferative disorder resembling human CML. The blast cells were clonal in origin and expressed p210(bcr/abl) with an increased kinase activity. Interestingly, the residual normal p53 allele was frequently and preferentially lost in the tumor tissues, implying that a certain mechanism facilitating the loss of p53 allele exists in p210(bcr/abl)-expressing hematopoietic cells. Our study presents in vivo evidence that acquired loss of p53 contributes to the blastic transformation of p210(bcr/abl)-expressing hematopoietic cells and provides insights into the molecular mechanism for blast crisis of human CML. (Blood. 2000;95:1144-1150)     

A murine model of acute liver injury induced by human monoclonal autoantibody

We have previously reported an immunoglobulin (Ig) M autoantibody to hepatocyte-related 190-kd molecules in patients with type 1 autoimmune hepatitis (AIH). This molecule was first isolated by hepatocyte-specific human monoclonal antibody (MoAb). To elucidate the role of this IgM autoantibody in hepatocyte injury, we examined the reactivity of this MoAb to murine hepatocytes and then questioned whether acute hepatic injury could be induced in mice via injection of this MoAb. The reactivity of MoAb was examined via both FACS analysis using murine hepatocytes and immunostaining of liver tissues. We then identified the murine hepatocyte membrane molecule recognized by this MoAb. The role of this MoAb in the immunopathogenesis of AIH was assessed by testing whether its injection into mice could increase serum aminotransferase levels as well as cause changes in liver histology. The present results demonstrate that this MoAb cross-reacted with murine hepatocytes and recognized a 190-kd molecule on the murine hepatocyte membrane just as in human hepatocytes. One hour after the injection of MoAb, the deposition of both IgM and complement component 3 was found in liver tissues. At 8 hours after the injection, serum aminotransferase levels were significantly increased in MoAb-injected mice compared with controls. Histological study revealed massive hepatocyte necrosis in MoAb-injected mice. In conclusion, human MoAb recognized a 190-kd molecule of both human and murine hepatocytes, and the injection of this MoAb to mice resulted in acute liver injury, indicating that this type of autoantibody may play an important role in the immunopathogenesis of AIH.     

Preparation and Characterization of Cellulose Ether Liposomes for the Inhibition of Prion Formation in Prion-Infected Cells

Prion accumulation in the brain and lymphoreticular system causes fatal neurodegenerative diseases. Our previous study revealed that cellulose ethers (CE) have anti-prion activities in vivo and in prion-infected cells when administered at high doses. This study aims to improve the bioavailability of a representative CE using a liposomal formulation and characterized CE-loaded liposomes in cultured cells. The liposomal formulation reduced the EC₅₀ dose of CE by <1/200-fold in prion-infected cells. Compared to empty liposomes, CE-loaded liposomes were taken up much more highly by prion-infected cells and less by macrophage-like cells. Phosphatidylserine modification reduced the uptake of CE-loaded liposomes in prion-infected cells and did not change the anti-prion activity, whereas increased the uptake in macrophage-like cells. Polyethylene glycol modification reduced the uptake of CE-loaded liposomes in both types of cells and reduced the anti-prion activity in prion-infected cells. These results suggest that a liposomal formulation of CE is more practical than unformulated CE and showed that the CE-loaded liposome uptake levels in prion-infected cells were not associated with anti-prion activity. Although further improvement of the stealth function against phagocytic cells is needed, the liposomal formulation is useful to improve CE efficacy and elucidate the mechanism of CE action.     

Inflammation-associated cancer development in digestive organs: mechanisms and roles for genetic and epigenetic modulation

Chronic inflammation, regardless of infectious agents, plays important roles in the development of various cancers, particularly in digestive organs, including Helicobacter pylori-associated gastric cancer, hepatitis C virus-positive hepatocellular carcinoma, and colitis-associated colon cancers. Cancer development is characterized by stepwise accumulation of genetic and epigenetic alterations of various proto-oncogenes and tumor-suppressor genes. During chronic inflammation, infectious agents such as H pylori and hepatitis C virus as well as intrinsic mediators of inflammatory responses, including proinflammatory cytokines and reactive oxygen and nitrogen species, can induce genetic and epigenetic changes, including point mutations, deletions, duplications, recombinations, and methylation of various tumor-related genes through various mechanisms. Furthermore, inflammation also modulates the expressions of microRNAs that influence the production of several tumor-related messenger RNAs or proteins. These molecular events induced by chronic inflammation work in concert to alter important pathways involved in normal cellular function, and hence accelerate inflammation-associated cancer development. Among these, recent studies highlighted an important role of activation-induced cytidine deaminase, a nucleotide-editing enzyme essential for somatic hypermutation and class-switch recombination of the immunoglobulin gene, as a genomic modulator in inflammation-associated cancer development.